ES2696473T3 - Security item - Google Patents

Abstract

Security article comprising: - a first layer (12) at least partially visible with reflected light, the first layer (12): - comprising a thermoplastic film containing one or more pigments, or - comprising a binder and at least one pigment dispersed in the binder when deposited by printing, surface finishing or coating, - a second diffuser layer (13) at least partially visible with reflected light, partially superimposed on the first layer (12), modifying the reflectance of the first layer (12), in order to appear in observation with reflected light by contrast between the first layer alone (12) and the superimposition of the first (12) and second layers (13), at least one motif observable to the naked eye, the pattern that appears with reflected light not being visible to the naked eye with transmitted light in particular when the first layer (12) is observed through the second layer (13).

Description

DESCRIPTION

Security item

The present invention relates to security articles, particularly to security structures intended to be inserted into documents to provide them with security, as well as to the documents insured as such. The term "insured document" means a means of payment, such as a banknote, a check or a restaurant voucher, an identity document, such as an identity card, a visa card, a passport or a permit. driving, a tenth lottery, a transport ticket or also an entrance ticket or invitation to cultural or sports events.

In order to prevent against attempts of forgery or fraudulent imitation of a document with security, it may be useful to authenticate and / or identify it easily.

It is known to apply by coating or printing an iridescent pigment in order to constitute a first level security. Such security can nevertheless be relatively easy to imitate.

WO2011 / 120917 discloses a banknote comprising a backing sheet of which at least one face comprises a clear protective varnish of non-glossy appearance. This varnish is applied in the form of a continuous solid color that preferably completely covers the surface of the bill, and allows to observe a background provided with offset printing. It is partially coated with a second protective layer with a shiny appearance that contrasts with the varnish layer. Reasons defined by the second layer can thus be observed with the naked eye with reflected light. The document only foresees an observation with reflected light and does not exploit an aspect difference between an observation with transmitted light and an observation with reflected light. This document also provides for applying the different layers on the two sides of the bill, in order to benefit from the effect by the straight and verso sides.

EP 0 518 740 refers to a security document containing an opaque security thread, visible with transmitted light, and having iridescent marks on at least one side.

WO 2004 / 030928A1 refers to a security article with a plurality of layers such as a set of images generated in reflection and which are not visible in transmission.

There is a need to further improve the security articles and particularly to benefit from security structures and security documents that present new effects easily recognizable by the man in the street, being difficult to imitate.

The invention seeks to respond to this need and aims, according to one of its aspects, a security article comprising:

- a first layer at least partially visible with reflected light,

- a second diffusing layer at least partially visible with reflected light, at least partly superimposed on the first layer, which modifies the reflectance of the first layer, so that it appears under observation with light reflected by contrast between the first layer alone and the superposition of the first and second layers, at least one motif observable to the naked eye, the reason being that it appears with reflected light visible to the naked eye with transmitted light, in particular when the first layer is observed through the second layer.

Preferably, the security article comprises a non-opaque substrate.

Alternatively, the security article does not comprise a substrate other than the layers. The first layer can, for example, be a film comprising in bulk iridescent pigments and play the supporting paper for the printing of the second layer.

Similarly, the second layer can be a film comprising colloidal silica mass and play the supporting paper for the coating of the first iridescent layer.

By diffusing layer, it is necessary to understand any layer diffusing the incident light.

By "nanometric modification", and "nanoparticle", a modification is designated respectively whose extension is between 1 and 1000 nm and a particle whose larger dimension is between 1 and 1000 nm.

By "transmitted light" it is necessary to understand a light that propagates through the eventual substrate and the first and second layers.

Unless otherwise mentioned, "observable", "observation", "visible", means "observable", " observation »,« visible »with reflected light.

For example, if the first and second layers are deposited on the straight side of a substrate, the latter is illuminated on the side verso, and the observation is made on the straight side thanks to the only light transmitted through the article, low incidence normal.

The lack of visibility of the motif with transmitted light may be due to the nanometric size of the local modifications of the article, particularly the particles.

The invention allows to benefit from the difference in appearance with reflected light and transmitted light of a first level security element easily recognizable by the man in the street and that can be easily combined with other security elements.

In addition, the first layer may be similar to the security elements with which the man in the street is already familiar, particularly in an iridescent state.

The security article can be a security structure intended to be integrated in or added to a document to provide it with security, such as a security thread, a patch, a sheet, a lamination film or a protective film of variable mentions .

The security article can also be a document with security, the different layers being, for example, supported by the substrate of the document itself and deposited by a coating, surface preparation or printing technique.

Contrast between the first and second layers

According to the invention, a contrast can be observed with reflected light between the first single layer and the superposition of the first and second layers.

This contrast goes together with different reflectances. Reflectance refers to the relationship between the reflected luminous flux and the incident luminous flux at given angles.

The superposition of the first and second layers preferably constitutes a set that is not totally transparent in at least one area, thanks to the diffusion of the light, at least in a part of the visible spectrum, by the second layer that modifies thus, the intensity of the reflectance of the first layer.

Preferably, the superposition of the first and second layers has an appearance, particularly a color and / or gloss, similar to that of the non-opaque substrate.

The reason is for example an alphanumeric character, and the corresponding information can be found on the other hand in the document.

For example, in the case of a banknote, the reason may correspond to the value of the ticket, the name of the currency, the bank or the country.

In the case of an identity document, the reason corresponds, for example, to the name or photograph of the document holder, or to the name of the issuing state of the document.

The reflectance of the superposition of the first and second layers should be less than 10%, preferably 20%, to the reflectance of the first layer alone. The reflectance is measured with the aid of a goniometer with an illumination / observation geometry of 45 ° / 45 ° and at the wavelength which has the maximum reflectance for the first layer, preferably within the visible spectrum, ie a length of wave between 400 and 800 nm.

Eventual non-opaque substrate

The eventual non-opaque substrate can be a transparent or translucent substrate. A translucent substrate is a substrate that diffuses light, that is, it allows a certain luminous intensity to pass without being transparent.

The substrate does not have to be completely transparent or translucent. It suffices that it be in an area that overlaps at least partially the first and the second layer, and preferably it is in an area that includes an area where only the first layer and an area where the two layers are included.

The substrate can be made transparent or translucent by incorporation or application of a suitable compound, particularly a transparentizing ink or also by compression or embossing, particularly by localized application of pressure and / or heat.

This transparentization can advantageously be carried out in the form of a pattern in order to obtain a pseudo-filigree.

In the case of a transparent substrate, it may be a film of a plastic material, particularly a thermoplastic material, or of a complex comprising several layers of superimposed plastic materials, in particular several layers of superposed transparent thermoplastic materials.

In the case of a translucent substrate, it may be a fibrous substrate or a substrate with at least one layer of plastic material having diffusion properties of light, for example on account of its surface condition and / or the presence of diffusion charges or microcavities in its breast.

It can also be a hybrid substrate comprising at least one fibrous layer and at least one layer of transparent or translucent plastic material.

When the substrate is at least partially fibrous, the fibers are preferably natural fibers such as cellulosic fibers, but can also be synthetic fibers, particularly such as those described in the application FR 1359135.

The fibers can be selected from different types of cellulosic fibers, for example wood fibers or annual plants such as cotton, hemp, abaca, or flax fibers. When the substrate comprises at least one layer of a synthetic material, this material is for example selected from polyolefins, and other thermoplastic materials, particularly PET (polyethylene terephthalate) and PC (polycarbonate). In the case of a substrate at least partially fibrous, this may comprise a watermark or a pseudo-filigree.

The thickness of the substrate is preferably between 5 and 1000 μm, better between 50 and 200 μm.

Preferably, the substrate does not have, in at least one area that is superimposed on the first and second layers, optical properties capable of preventing observation with reflected light of the pattern formed by contrast of appearance between the two layers.

The substrate can incorporate a security element of first, second or third level. In particular, the substrate may advantageously be filigree when it is a paper, and the first and second layers may eventually overlap the watermark. The visible pattern with light reflected by contrast of appearance between the first layer alone and the superposition of the first and second layers can be superimposed on a non-opaque area of the substrate, for example the indicated filigree in the case of a filigree paper.

First layer

The first layer allows to obtain a visual contrast in observation with reflected light with the superposition of the first and second layers.

The first layer can be completely transparent but, preferably, it provides an optical effect that is not limited to a single brightness contribution.

Thus, the first layer is preferably another one of a simple transparent varnish, and preferably the superposition of the first layer and the second layer constitutes a not entirely transparent assembly that diffuses the light in at least a part of the visible spectrum.

The first layer preferably comprises one or more particles that confer particular optical properties, mainly one or more reflective, chromatic, interferential particles, preferably goniochromatic, particularly iridescent. These particles can be spherical or laminar. These are in particular pigments or inserts.

The first layer is not completely opaque in order to allow an observation through it with transmitted light, particularly in an area where the first and second layers overlap and / or in the area of the pattern formed in observation with light reflected by contrast aspect between the first layer and the superposition of the first and second layers.

The first layer may never be opaque, or in an opaque variant by zones, with the proviso that there remains a zone that allows observation with light transmitted through it and the second layer.

In the presence of drafts in the first layer, the second layer may or may not extend in the drafts of the first layer.

The first layer can be deposited on the optional substrate in multiple ways, for example in the fluid state, for example in the form of a printing, embossing or covering coating.

The first layer can extend from one end of the substrate to the other, without necessarily covering its entire surface. The first layer can particularly take the form of a ribbon.

The first layer may be perforated or not. The draft (s) define, for example, one or several reasons in negative writing.

The first layer can also be deposited on the substrate in the form of a sheet, comprising for example a film that is laminated or extruded onto the substrate or also co-extruded with the substrate.

The first layer can cover an area of the substrate that has homogeneous properties with transmitted light. In variant, this area of the substrate has inhomogeneous properties with transmitted light, which causes a pattern attached to these non-homogeneous properties to appear with transmitted light, preferably in an area where the first and second layers overlap.

The first layer can be directly in contact with the substrate, being for example in contact with the fibers thereof when it is fibrous, or coating the substrate with interposition of one or more intermediate layers, when they have for example homogeneous optical properties with transmitted light.

The first layer can also be sunk into the substrate by zones, which is the case, for example, when the article according to the invention is a security element that is presented in the form of a yarn inserted into windows on a paper substrate.

The first layer is preferably closer to the substrate than the second layer.

The first layer may comprise a thermoplastic film comprising one or more pigments therein, for example incorporated during an extrusion in the thickness of the film. It can be a raw thermoplastic film or a hybrid material with several co-extruded layers. It is preferably a thermoplastic film with microcavities as described in the application WO 2010146065.

The first layer can also be formed by an impression, being deposited particularly by screen printing, engraving in candy, ink jet or heliogravure, preferably it is made by screen printing or heliogravure. The non-opaque substrate can undergo an impression, particularly a partial print, the unprinted areas being able to then form a pattern that appears "in negative" with reflected light, even with light transmitted equally.

The first layer may also result from a surface treatment such as a surface finish or coating.

The layer, when deposited by printing, by surface preparation or by coating, may comprise a binder and at least one pigment dispersed in the binder.

Preferably, the first particle (s) used for the purpose of imparting its optical properties to the first layer are selected from among the interferential pigments, preferably between the goniochromatic and / or iridescent pigments, particularly the pearlescents comprising mica, titanium. , silica, aluminum, tin oxide, zirconium oxide, alumina, iron oxide, or borosilicate.

The structure of these particles can be a non-opaque or opaque core, particularly metallic, coated with one or more thin layers having different refractive indices, said layers being constituted by metals and / or dielectric materials.

This or these particles can be selected to give the first layer a bright appearance in observation with reflected light and not bright in transmission.

The binder of the first layer can be chosen from alcohol-based polyvinyl alcohol, polyacrylic, polyurethane, polyvinyl acetate binders as well as the associated copolymers.

The first layer is preferably bright. This gloss is particularly conferred by the particles and / or the binder.

The total mass amount of particle (s), in dry weight, in the first layer, can be comprised between 10 and 60%, better between 20 and 40%.

The thickness of the first layer can be comprised, on the article, between 3 and 30 pm.

The amount of particle (s) within the first layer can be adapted as a function of the intrinsic opacity of the particle or particles retained so that the first layer maintains a certain transparency.

The first layer can correspond to one of the following examples:

• Polyvinyl alcohol binder (Mowiol 47-88 from the Kuraray Company) pigments (Mearlin Firemist Gold from the BASF Company) at 20% by dry weight,

• Polyacrylic binder (Revacryl 5732 from the Synthomer Company) pigments (Pearl Sparkling Yelow from the QolorTech Company) at 37% by dry weight, or

• Polyurethane binder (Witcobond 391-64 from the Baxenden Company) pigments (Lustrepack Gold from the Merck Company) at 50% by dry weight.

The first layer can carry at least one security element, particularly a metallization and / or demetallization.

The first layer preferably has no microstructured relief such as a diffraction grating or a lenticular network. Alternatively, the first layer has a microstructured relief, such as, for example, a diffraction grating, particularly a hologram.

The first layer may contain, if necessary, a security element which is a luminescent substance which is particularly fluorescent and / or phosphorescent. A security element of this type has the effect of allowing a disappearance under a lighting, for example a UV illumination, of a pattern comprising nanometric particles of the second layer. The second layer is detailed below.

Second layer

The second diffuser layer comprises a matrix with an index of refraction nmatriz and local nanometric modifications in the matrix, with refraction index nmodifications, which may differ from that of the matrix with a difference | nmatriz - nmodificaciones | greater than or equal to 0.01, better than 0.03. According to a preferred variant, this layer comprises a polymer matrix with an index of refraction nmatrix, and a dispersion of nanoscale particles in the matrix, with refractive index nparticles different from that of the matrix, with a difference | nmatriz - npartículas | greater than or equal to 0.01, better than 0.03.

The second layer is only partially superimposed on the first layer, which means that there is at least one area visible by the observer of the first layer that is not covered by the second layer, so that a contrast pattern appears. In particular, the second layer may be perforated so as to allow the first layer to appear in zones, the total area occupied by it or these openings then being advantageously less than half of the total surface defined by the outer perimeter of the second layer. cap.

The second layer can be completely overlapped with the first layer except in the openings formed in the second layer, where the first layer is not covered by the second layer and becomes apparent. This can allow forming one or more visible motifs in negative writing within the second layer.

The second layer may be partially but not fully superimposed on the first, particularly due to the presence of drafts.

The second layer may have a localized diffusing character so that the indicated reason appears. These may be nanometric modifications located in the areas of the motif only.

Alternatively, the second layer is not perforated and the pattern (s) are positively written at least partly on the first layer.

It may be interesting to combine one or several motifs that appear in positive writing and one or more motives, particularly identical, that appear in negative writing on the first layer. In this case, care will be taken to keep an aspect, particularly a color and / or gloss, similar between the superposition of the two layers and the possible substrate observed in reflected light. Preferably the presence of the second layer is not easily discernible by the observer with transmitted light, even it is not perceptible, due to the nanometric extension of the local modifications, and particularly of the size of the particles of the second layer. The second layer may not comprise any charge of opacifying particles, particularly any intrinsically opaque pigment.

The second layer can be an impression. The second layer may be devoid of goniochromatic pigment and / or reflective metallic pigment, particularly of pigment comprising a layer of a metal such as aluminum.

When the second layer is deposited by printing, this printing can be done by screen printing, engraving in candy, inkjet or heliogravure, preferably by screen printing or heliogravure.

The local nanometric modulus (s), particularly the particles, present in the second layer are preferably selected in order to confer optical properties different from those of the first layer.

Thus, preferably, the first and second layers contain different particles, particularly pigment particles of different colors.

Preferably the particles are preferably mineral metal oxides or carbonates, preferably still based on silica, and more preferably based on pyrogenic silica.

The local modifications contained in the second layer have an extension comprised between 1 and 1000 nm and preferably between 1 and 200 mm. In particular, the particles contained in the second layer have a greater dimension comprised between 1 and 1000 nm and preferably between 1 and 200 nm.

The layer, particularly the polymeric matrix, comprises for example a material selected from polyvinyl alcohols, polyacrylic alcohols, polyurethanes, polyethylene terephthalates, polysiloxanes, polycarbonates, polyvinyl acetates as well as copolymers.

The particles may constitute between 20 and 70% by dry weight, preferably between 30 and 50% by dry weight, of the total mass of the second layer.

The second layer may comprise at least one supplementary security element, particularly a security element as described below. This or these supplementary security elements can, if necessary, be superimposed at least partially with a pattern created by contrast with reflected light between the first single layer and the superposition of the first and second layers.

The thickness of the second layer on the article can be between 1 and 30 pm.

The second layer may contain, if necessary, a security element which is a luminescent substance, a photochromic substance, and / or a thermochromic substance.

In the case in which these substances comprise particles, these are preferably of nanometric size, in order to maintain the invisibility with the naked eye with transmitted light of the second layer.

The pattern (s) formed by contrast of appearance with the first layer can nevertheless be visible independently of the revelation of a luminescent, photochrome or thermochrome effect.

It may be particularly interesting that the second layer comprises a luminescent compound to make the reason (s) formed by the second layer appear, particularly with light transmitted under UV or IR.

For example, the second layer comprises a pigment or fluorescent dye under UV. The first layer may be devoid of or comprise a luminescent compound that appears in another color under excitation with UV or IR. The first layer can, in a variant, comprise a luminescent compound that allows a disappearance of a pattern of the second layer under UV excitation.

In particular, the binders of the first and second layers can be the same.

For example, the second layer may comprise, dispersed in a binder ALBERDINGK U5201 of the Alberdingk Boley Company, an HDK load XK20030 from the WACKER company in a proportion of 50% by dry weight.

Supplementary security elements

The security article or document may comprise one or more supplementary security elements as defined below, particularly within the first, the second layer or the substrate.

Among the supplementary security elements, some can be detected with the naked eye, in daylight or with artificial light, without the use of a particular device. These security elements comprise, for example, colored fibers or planks, printed or metallized threads, in whole or in part. These security elements are called first level.

Other types of supplementary security elements can only be detected with the aid of a relatively simple apparatus, such as a lamp that emits in ultraviolet (UV) or infrared (IR). These security elements comprise, for example, fibers, planks, strips, threads or particles. These security elements may be visible to the naked eye or not, being for example luminescent under an illumination of a Wood lamp that emits at a wavelength of 365 nm. These security elements are called second level.

Other types of supplementary security elements need a more sophisticated detection device for detection. These security elements are for example capable of generating a specific signal when they are subjected, simultaneously or not, to one or more sources of external excitation. The automatic detection of the signal allows to authenticate, if necessary, the document. These safety elements comprise, for example, tracers which are in the form of active materials, particles or fibers, capable of generating a specific signal when these tracers are subjected to optronic, electric, magnetic or electromagnetic excitation. These security elements are called third level.

The invention also has as its object, according to another of its aspects, a method of authenticating a document according to the invention, in which the user observes the document successively with reflected light and then with transmitted light, deducting information regarding the authenticity of the document. document on the basis of a comparison of the observed aspects, particularly the visibility of the subject with reflected light and its non-visibility with transmitted light.

When the second layer comprises a luminescent compound, particularly fluorescent, the method may further comprise a stage of illumination under UV or IR with transmitted light, in order to cause the pattern formed by the second layer to appear.

The invention also has as its object, according to another of its aspects, a method of manufacturing a document as defined above, in which a first layer is partially covered by a second layer that modifies the reflectance of the first layer, with the In order to appear in observation with light reflected by contrast between the first layer and the superposition of the first and second layers an observable motif on the indicated face, this reason not being visible to the naked eye with transmitted light, due to the low contrast with light transmitted, even non-existent contrast, taking into account the low opacity of the second layer.

The invention can be better understood by reading the detailed description that follows, of non-limiting examples of this, as well as the examination of the attached drawing, in which:

- Figure 1 represents in partial section and schematic a security article according to the invention, - Figures 2A to 2C illustrate variations of appearance according to the observation of an example of article according to the invention, and

- Figures 3A and 3B represent another example of variation of appearance that can be obtained in another embodiment according to the invention.

In the attached drawing, the actual proportions of the various constituent elements or their spacings have not always been respected in an attempt to clarify.

1 shows an example of security article 1 according to the invention, in this case a document provided with security.

The article 1 comprises a substrate 11 covered with a first layer 12 in its contact, likewise covered with a second layer 13.

The first layer 12 can have a bright appearance with reflected light, for example when viewed according to the path OR of Figure 1.

The bright appearance of the first layer 12 is for example obtained by making this layer 12 by means of a thermoplastic film including at least a first particle P1, preferably interferential, for example a particle comprising mica plates coated with TiO titanium dioxide ²

The second layer 13 only partially covers the first, which allows the observer to distinguish an M ² motif delimited by the extension of the second layer 13.

The second layer 13 preferably has a matte appearance with reflected light, when viewed according to the OR path. The second layer 13 integrates for example a charge or particle P2, for example pyrogenic silica, as detailed above.

Preferably, the second layer 13 is deposited by printing, which allows to easily form a pattern on the desired contour, for example a motif in positive or negative writing, particularly an alphanumeric motif or corresponding to information that is otherwise found in Article.

The printing 13 is for example made by screen printing. The formulation of the second layer 13 is such that with light transmitted subsequently in the illumination of the verse of the article, that is to say an observation according to the path OT, the motif M ² is not visible to the naked eye from the rectum of the article.

FIG. 2 shows an embodiment according to the invention, in which the first layer 12 is perforated and defines a first motif M ¹ in negative, allowing the substrate 11 to appear.

The second layer 13 is deposited, for example printed by screen printing, in order to present a contour 131 which designs a second M ² pattern, for example similar to the first M ¹ pattern and visible only with reflected light.

The second layer 13 has for example substantially the same color as the substrate 11.

Figure 2A is a view with reflected light of the article of Figure 2 and Figure 2B is a view with transmitted light. It can be seen in FIG. 2B that the M ² motifs are no longer discernible with transmitted light.

The second layer 13 may not have any luminescent property, for example, without integrating any dye or fluorescent pigment, under UV or IR.

Alternatively, the second layer 13 is made in order to exhibit luminescent properties, and comprise for example a dye or fluorescent pigment under UV P2, so that the second or second patterns are visible with muz transmitted in the presence of ultraviolet radiation, as illustrated in Figure 2C, but are invisible with transmitted light in the absence of ultraviolet radiation.

Figures 3A and 3B illustrate another embodiment according to the invention in which only the print 13 has a contour defining a pattern M. Figure 3A is a view with reflected light of the substrate coated with the film 12 and the print 13 , and Figure 3B is a view with transmitted light. It is observed in Figure 3B that the motifs M formed by the second layer 13 do not appear with transmitted light.

Figure 4 illustrates another embodiment of the article according to the invention. The article comprises a first layer 12 of plastic material, for example PET in which particles P1 are dispersed, preferably goniochromatic particles, preferably still iridescent particles.

A second layer 13 is partially arranged in the first layer. This second layer comprises nanometric modifications, preferably comprising nanometric particles P2.

Figure 5 illustrates another embodiment of the article according to the invention. The article comprises a layer 13 of plastic material, for example PET, comprising localized nanometric modifications in order to form one or several motifs. In this layer 13 is disposed a layer 12 comprising particles P1, preferably goniochromatic particles, preferably also iridescent particles. The plastic material in the layer 13 can completely cover the layer 12. In this embodiment, the observation is made from the layer 13.

The expression "comprising one" must be understood as being synonymous with "comprising at least one", unless otherwise specified.

Claims (15)

1. Security article that includes: - a first layer (12) at least partially visible with reflected light, the first layer (12): - comprising a thermoplastic film including one or more pigments in its interior, or - comprising a binder and at least one pigment dispersed in the binder when deposited by printing, by surface finish or by coating, - a second diffusing layer (13) at least partially visible with reflected light, partially superimposed on the first layer (12), modifying the reflectance of the first layer (12), so that it appears under observation with light reflected by contrast between the first single layer (12) and the superposition of the first (12) and second layers (13), at least one motif observable to the naked eye, the reason being that it appears with reflected light visible to the naked eye with transmitted light in particular when the first layer (12) is observed through the second layer (13). Item according to claim 1, the superposition of the first layer (12) and the second layer (13) constituting a non-transparent assembly that diffuses the light at least in a part of the visible spectrum. Item according to one of the preceding claims, the first layer (12) comprising one or more first particles (P1), the first particle (s) (P1) being selected from among the reflective, chromatic, interferential particles, preferably goniochromatic particularly iridescent. Article according to any one of claims 1 to 3, the first layer (12) comprising a thermoplastic film. Article according to any one of the preceding claims, the second diffusing layer comprising a matrix with an index of refraction nmatrix and local nanometric modifications in the matrix, with refraction index nmodifications, different from that of the matrix with a difference | nmatriz - nmodifications | greater than or equal to 0.01, better than 0.03. Article according to any one of the preceding claims, the second layer (13) being devoid of a goniochromatic pigment. Item according to any one of the preceding claims, the second layer comprising local nanometric modifications whose extension is between 1 and 1000 nm, preferably between 1 and 200 nm Article according to any one of the preceding claims, the second layer comprising particles with a greater dimension comprised between 1 and 1000 nm, preferably between 1 and 200 nm. Article according to any one of the preceding claims, the second layer comprising mineral particles (P2), preferably metal oxides or carbonates, preferably still based on silica, and more preferably on the basis of pyrogenic silica. Article according to any one of the preceding claims, the second layer comprising particles constituting between 20 and 70% dry mass, preferably between 30 and 50% dry mass, of the total mass of the second layer . Article according to any one of the preceding claims, the second layer being partially but not totally superimposed on the first. Article according to any one of the preceding claims, the first layer comprising a luminescent substance, preferably fluorescent and / or phosphorescent. 13. Article according to any one of claims 1 to 12, the second layer having a localized diffusing character in order to cause the said reason to appear. The authentication procedure of an article (10) according to any one of the preceding claims, in which a user observes the article successively with reflected light and then with transmitted light, compares the observed aspects, and extracts from them an information regarding Authenticity based on the result of the comparison. 15. Method of manufacturing an article (10) according to any one of claims 1 to 13, wherein a first layer is partially covered by a second layer that modifies the reflectance of the first layer, in order to make it appear in observation with light reflected by contrast between the first layer and the superposition of the first and second layers an observable motif on said face, this reason not being visible to the naked eye with transmitted light.