EP3083258B2 - Security item - Google Patents

Description

The present invention relates to security articles, in particular security structures intended to be introduced into documents to secure them, as well as the secure documents themselves. "Secure document" means a means of payment, such as a banknote, a check or a restaurant ticket, an identity document, such as an identity card, a visa, a passport or a driver's license, a lottery ticket, a transport ticket or even a ticket or an entry card to cultural or sporting events.

In order to guard against attempts to falsify or counterfeit a secure document, it may be useful for its authentication and/or identification to be able to be done simply.

It is known to apply an iridescent pigment by coating or printing in order to provide first-level security. Such security can nevertheless prove to be relatively easy to counterfeit.

WO2011/120917 describes a banknote which comprises a support sheet of which at least one face comprises a transparent protective varnish of non-shiny appearance. This varnish is applied in the form of a continuous solid surface preferably completely covering the surface of the banknote, and makes it possible to observe a background lined with offset printing. It is partially coated with a second shiny protective layer which contrasts with the varnish layer. Patterns defined by the second layer are thus observable with the naked eye in reflected light. The document only provides for observation in reflected light and does not exploit a difference in appearance between observation in transmitted light and observation in reflected light. This document also provides for applying the different layers on both sides of the banknote, in order to benefit from the effect on the front and back sides.

EP 0 518 740 relates to a secure document containing an opaque security thread, visible in transmitted light, and presenting on at least one face iridescent marks.

The document WO 2004/030928 A1 relates to a security article having 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 security articles and in particular to benefit from security structures and secure documents having new effects that are easily recognizable by the man in the street, while being difficult to counterfeit.

The invention aims to meet this need and has as its object, according to one of its aspects, a security article according to claim 1.

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

As a variant, the security article does not comprise a substrate distinct from the layers. The first layer can for example be a film comprising mass of iridescent pigments and play the role of support for the printing of the second layer.

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

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

The term “nanometric modification” and “nanometric particle” denotes respectively a modification whose extent is between 1 and 1000 nm and a particle whose largest dimension is between 1 and 1000 nm.

By “transmitted light” it is necessary to understand a light which propagates through the possible substrate and the first and second layers.

Unless otherwise stated, by “observable”, “observation”, “visible”, we mean “observable”, “observation”, “visible” in reflected light.

For example, if the first and second layers are deposited on the recto side of a substrate, the latter is illuminated on the verso side, and the observation is carried out on the recto thanks to the light transmitted through the article alone, under incidence normal.

The absence of visibility of the pattern in transmitted light may be due to the nanometric size of the local modifications of the article, in particular of the particles.

The invention makes it possible to benefit, thanks to the difference in appearance in reflected light and in transmitted light, from a first level security easily recognizable by the man in the street and which can easily be combined with other securities.

In addition, the first layer can be similar to securities with which the man in the street is already familiar, in particular by being iridescent.

The security article can be a security structure intended to be integrated into or attached to a document to secure it, such as a security thread, a patch, a foil, a lamination film or a protective film for mentions variables.

The security item can still be a document secure, the different layers being for example carried by the substrate of the document itself and deposited by a technique of coating, surfacing or printing.

Contrast between the first and second layers

In accordance with the invention, a contrast is observable in reflected light between the first layer alone and the superposition of the first and second layers.

This contrast is linked to different reflectances. Reflectance refers to the ratio of the reflected luminous flux to the incident luminous flux at given angles.

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

Preferably, the superposition of the first and of the second layer has an appearance, in particular a tint and/or a shine, similar to that of the non-opaque substrate.

The pattern is for example an alphanumeric character, and the corresponding information can be found elsewhere on the document.

For example, in the case of a banknote, the pattern can correspond to the value of the note, the name of the currency, the bank or the country.

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

The reflectance of the superposition of the first and second layers must be 10%, preferably 20%, lower than the reflectance of the first layer alone. Reflectance is measured using a goniometer with 45°/45° illumination/viewing geometry and at the wavelength with the maximum reflectance for the first layer, preferably in the visible spectrum , i.e. a wavelength between 400 and 800 nm.

Possible non-opaque substrate

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

The substrate does not have to be entirely transparent or translucent. It suffices that it be in a zone overlapping at least partially with the first and the second layer, and preferably that it be in a zone encompassing a region where only the first layer appears and a region where both layers.

The substrate can be made transparent or translucent by incorporating or applying a suitable compound, in particular a transparentizing ink or else by compression or embossing, in particular by localized application of pressure and/or heat.

This transparency can advantageously be carried out in the form of a pattern so as to obtain a pseudo-watermark.

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

In the case of a translucent substrate, it may be a fibrous substrate or a substrate having at least one layer of plastic material endowed with light scattering properties, for example due to its surface condition. and/or the presence of diffusing fillers or microcavities within it.

It may 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 they can also be synthetic fibers, in particular as described in the application FR1359135 .

The fibers can be chosen from different types of cellulosic fibers, for example fibers from wood or from 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 chosen from polyolefins and other thermoplastic materials, in particular PET (polyethylene terephthalate) and PC (polycarbonate).

In the case of an at least partially fibrous substrate, the latter may comprise a watermark or a pseudo watermark.

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

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

The substrate may incorporate a first, second or third level security element. In particular, the substrate can advantageously be watermarked when it is a paper, and the first and second layers can optionally be superimposed on the watermark. The pattern visible in reflected light by aspect contrast between the first layer alone and the superposition of the first and second layers can be superimposed on a non-opaque zone of the substrate, for example said watermark in the case of a watermarked paper.

First layer

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

The first layer can be entirely transparent but, preferably, it provides an optical effect which is not limited to a single contribution of shine.

Thus, the first layer is preferably other than a simple transparent varnish, and preferably the superposition of the first layer and of the second layer constitutes a non-totally transparent assembly diffusing the light in at least part of the visible spectrum.

The first layer preferably comprises one or more particles giving it particular optical properties, in particular one or more reflective, chromatic, interference, preferably goniochromatic, in particular iridescent particles. These particles can be spherical or lamellar. These are in particular pigments or platelets.

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

The first layer may never be opaque, or as a variant opaque in places, provided that there remains a zone allowing observation in light transmitted through it and the second layer.

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

The first layer can be deposited on the possible substrate in multiple ways, for example in the fluid state, for example in the form of a print, a surfacing or a coating 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 in particular take the form of a strip.

The first layer can be perforated or not. The opening or openings define, for example, one or more patterns in negative writing.

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

The first layer can cover an area of the substrate which has homogeneous properties in transmitted light. As a variant, this zone of the substrate has inhomogeneous properties in transmitted light, which means that a pattern linked to these inhomogeneous properties can appear in transmitted light, if necessary preferably in a zone where the first and second layers are superimposed.

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

The first layer can also be embedded within the substrate in places, which is for example the case when the article according to the invention is a security element which is in the form of a wire introduced in windows in a substrate in paper.

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

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

The first layer can also be formed by printing, in particular being deposited by screen printing, intaglio, ink jet or photogravure, preferably it is produced by screen printing or photogravure. The non-opaque substrate can undergo printing, in particular partial printing, the non-printed areas then being able to form a pattern which appears “in negative” in reflected light, or even in transmitted light as well.

The first layer can also result from a surface treatment such as surfacing or coating.

The layer, when it is deposited by printing, by surfacing or by coating, can comprise a binder and at least one pigment dispersed in the binder.

Preferably, the first particle(s) used to give the first layer its optical properties are chosen from interference pigments, preferably from goniochromatic and/or iridescent pigments, in particular nacres comprising mica, titanium, silica, aluminum, tin oxide, zirconium oxide, alumina, iron oxide, or borosilicate.

The structure of these particles may be a non-opaque or opaque, in particular metallic, core coated with one or more thin layers having different refractive indices, said thin layers possibly consisting of metals and/or dielectric materials.

This or these particles can be chosen to give the first layer a shiny appearance when observed in reflected light and not shiny when transmitted.

The binder of the first layer can be chosen from binders based on polyvinilalcohol, polyacrylic, polyurethane, polyvinilacetate as well as copolymers associates.

The first layer is preferably glossy. This gloss is in particular imparted by the particles and/or the binder.

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

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

• Liant polyvinyl alcohol (Mowiol 47-88 de la société Kuraray) + pigments (Mearlin Firemist Gold de la société BASF) à 20% en poids sec,
• Liant polyacrylique (Revacryl 5732 de la société Synthomer) + pigments (Pearl Sparkling Yellow de la société QolorTech) à 37% en poids sec, ou
• Liant polyurethane (Witcobond 391-64 de la société Baxenden) + pigments (Lustrepack Gold de la société Merck) à 50% en poids sec.

It is possible to adapt the quantity of particle(s) within the first layer according to the intrinsic opacity of the retained particle(s) so that the first layer retains a certain transparency.
The first layer can correspond to one of the following examples:

• Polyvinyl alcohol binder (Mowiol 47-88 from Kuraray) + pigments (Mearlin Firemist Gold from BASF) at 20% by dry weight,
• Polyacrylic binder (Revacryl 5732 from Synthomer) + pigments (Pearl Sparkling Yellow from QolorTech) at 37% by dry weight, or
• Polyurethane binder (Witcobond 391-64 from Baxenden) + pigments (Lustrepack Gold from Merck) at 50% by dry weight.

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

The first layer preferably does not have any microstructured relief such as a diffraction grating or a lenticular grating. As a variant, the first layer has a microstructured relief, such as for example a diffraction grating, in particular a hologram.

The first layer may contain, where appropriate, a security element being a luminescent substance, in particular fluorescent and/or phosphorescent. Such a security element has the effect of allowing disappearance under illumination, for example UV illumination, of a pattern comprising nanometric particles of the second layer. The second layer is detailed below.

second layer

The second diffusing layer comprises a matrix having a refractive index n _matrix and local nanometric modifications in the matrix, of refractive index n _{modifications} , which may differ from that of the matrix with a difference |n _matrix − n _{modifications} | greater than or equal to 0.01, better still 0.03. According to a preferred variant, this layer comprises a polymer matrix having a refractive index n _matrix , and a dispersion of nanometric particles in the matrix, with a refractive index n _particles different from that of the matrix, with a gap |n _matrix - n _particles | greater than or equal to 0.01, better still 0.03.

The second layer is only partially superimposed on the first layer, which means that there is at least one area visible to the observer of the first layer which is not covered by the second layer, in order to reveal a pattern by contrast. In particular, the second layer can be perforated so as to reveal the first layer in places, the total area occupied by this or these openings then being advantageously less than half of the total area defined by the outer perimeter of the second layer.

The second layer can be completely superimposed on the first except in the openings formed in the second layer, where the first layer is not covered by the second and remains visible. This can make it possible to form one or more visible patterns in negative writing within the second layer.

The second layer may be partially but not totally superimposed on the first, in particular because of the presence of openings.

The second layer may have a localized diffusing character so as to reveal said pattern. These may be nanometric modifications localized to the regions of the pattern only.

As a variant, the second layer is non-perforated and the pattern or patterns are formed in positive writing at least partially on the first layer.

It may be advantageous to combine one or more patterns which appear in positive writing and one or more patterns, in particular identical, which appear in negative writing on the first layer. In this case, care will be taken to maintain, in observation in reflected light, an appearance, in particular a hue and/or a shine, similar between the superposition of the two layers and the possible substrate. Preferably the presence of the second layer is not easily perceptible. by the observer in transmitted light, or even is not perceptible, because of the nanometric extent of the local modifications, and in particular of the size of the particles of the second layer.

The second layer may contain no opacifying particulate filler, in particular no intrinsically opaque pigment.

The second layer can be a print. The second layer may be devoid of goniochromatic pigment and/or reflective metallic pigment, in particular pigment comprising a layer of a metal such as aluminum.

When the second layer is deposited by printing, this printing can be performed by screen printing, intaglio, ink jet or photogravure, preferably it is performed by screen printing or photogravure.

The local nanometric modification(s), in particular the particles, present in the second layer are preferably chosen so as to give it optical properties different from those of the first layer.

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

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

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

The layer, in particular the polymer matrix, comprises for example a material chosen from polyvinylalcohols, polyacrylics, polyurethanes, polyethylene terephthalates, polysiloxanes, polycarbonates, polyvinylacetates as well as copolymers.

The particles can 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 can comprise at least one additional security element, in particular a security element as described below. This or these additional security elements can be superimposed, where appropriate, at least partially with a pattern created by contrast in reflected light between the first layer alone and the superposition of the first and second layers.

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

The second layer may contain, where appropriate, a security element being a luminescent substance, a photochromic substance, and/or a thermochromic substance.

In the case where these substances comprise particles, these are preferably of nanometric size, so as to preserve the invisibility to the naked eye in transmitted light of the second layer.

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

It may be particularly advantageous for the second layer to comprise a luminescent compound to make the pattern or patterns formed by the second layer appear, in particular in light transmitted under UV or IR.

For example, the second layer comprises a fluorescent pigment or dye under UV. The first layer can be devoid of it or comprise a luminescent compound appearing in another color under UV or IR excitation.

The first layer may, as a variant, comprise a luminescent compound which allows a pattern of the second layer to disappear 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 an ALBERDINGK U5201 binder from the company Alberdingk Boley, a filler HDK XK20030 from the company WACKER in a proportion of 50% by dry weight

Additional security features

The secure item or document may comprise one or more additional security elements as defined below, in particular within the first, the second layer or the substrate.

Among the additional security elements, some are detectable with the naked eye, in daylight or in artificial light, without using a particular device. These security elements comprise, for example, colored fibers or boards, printed or totally or partially metallized threads. These security elements are said to be first level.

Other types of additional security elements are detectable only using a relatively simple device, such as a lamp emitting in the ultraviolet (UV) or infrared (IR). These security elements include, for example, fibers, boards, bands, threads or particles. These security elements may or may not be visible to the naked eye, being for example luminescent under illumination from a Wood lamp emitting at a wavelength of 365 nm. These security elements are said to be of second level.

Other types of additional security elements require a more sophisticated detection device for their detection. These security elements are for example capable of generating a specific signal when they are subjected, simultaneously or not, to one or more external excitation sources. The automatic detection of the signal makes it possible to authenticate, if necessary, the document. These security elements include, for example, tracers in the form of active materials, particles or fibers, capable of generating a specific signal when these tracers are subjected to optronic, electrical, magnetic or electromagnetic excitation. These security elements are said to be third level.

Another subject of the invention, according to another of its aspects, is a process for authenticating a document according to the invention, in which a user observes the document successively in reflected light then in transmitted light, deduces therefrom information concerning the authenticity of the document on the basis of a comparison of the observed aspects, in particular the visibility of the pattern in reflected light and its non-visibility in transmitted light.

When the second layer comprises a luminescent, in particular fluorescent, compound, the method may also comprise a step of illumination under UV or IR in transmitted light, in order to bring out the pattern formed by the second layer.

Another subject of the invention, according to another of its aspects, is a process for producing a document as defined above, in which a first layer is partially covered by a second layer modifying the reflectance of the first layer, so as to make it appear in observation in reflected light by contrast between the first layer and the superposition of the first and second layers an observable pattern on said face, this pattern not being visible to the naked eye in transmitted light, due to the low contrast in transmitted light, or even the non-existent contrast, given the low opacity of the second layer.

• la figure 1 représente en coupe partielle et schématique un article sécurisé selon l'invention,
• les figures 2A à 2C illustrent des variations d'aspect selon l'observation d'un exemple d'article selon l'invention, et
• les figures 3A et 3B représentent un autre exemple de variation d'aspect pouvant être obtenue dans un autre exemple de réalisation selon l'invention.

The invention may be better understood on reading the detailed description which follows, of non-limiting examples of implementation thereof, as well as on examining the appended drawing, in which:

• the figure 1 represents in partial and schematic section a secure article according to the invention,
• them figures 2A to 2C illustrate variations in appearance according to the observation of an example of an article according to the invention, and
• them figures 3A and 3B represent another example of variation in appearance that can be obtained in another example embodiment according to the invention.

In the attached drawing, the actual proportions of the various constituent elements or their spacing have not always been respected for the sake of clarity.

We represented on the figure 1 an example of security article 1 according to the invention, in this case a secure document.

Article 1 comprises a substrate 11 covered with a first layer 12 in contact with it, itself covered with a second layer 13.

The first layer 12 can have a shiny appearance in reflected light, for example when observed along the path OR of the figure 1 .

The shiny appearance of the first layer 12 is for example obtained by producing this layer 12 by means of a thermoplastic film including at least one first particle P1, preferably interference, for example a particle comprising mica plates coated with carbon dioxide. titanium TiO ₂ .

The second layer 13 only partially covers the first, which allows the observer to distinguish a pattern M ₂ delimited by the extent of the second layer 13.

The second layer 13 preferably has a matte appearance in reflected light, when observed along the path OR. The second layer 13 for example incorporates a filler or particle P2, for example fumed silica, as detailed above.

Preferably, the second layer 13 is deposited by printing, which makes it possible to easily form a pattern with the desired contour, for example a pattern in positive or negative writing, in particular an alphanumeric pattern or corresponding to information which is found elsewhere on the 'article.

Printing 13 is for example performed by screen printing. The formulation of the second layer 13 is such that in light transmitted following illumination of the back of the article, that is to say from an observation along the path OT, the pattern M ₂ is not visible to the naked eye from the front of the item.

We represented at the figure 2 an exemplary embodiment according to the invention, in which the first layer 12 is perforated and defines a first pattern M ₁ in negative, revealing the substrate 11.

The second layer 13 is deposited, for example printed by screen printing, so as to present an outline 131 which draws a second pattern M ₂ , for example of a shape similar to the first pattern M ₁ and visible only in reflected light.

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

The figure 2A is a reflected light view of the article of the figure 2 and the figure 2B is a transmitted light view. We see on the figure 2B that the patterns M ₂ are no longer discernible in transmitted light.

The second layer 13 may not have any luminescence property by not integrating, for example, any fluorescent dye or pigment, under UV or IR.

As a variant, the second layer 13 is produced in such a way as to have luminescence properties, and comprise for example a dye or pigment fluorescent under UV P2, so that the second pattern or patterns are visible in transmitted light in the presence of radiation. ultraviolet, as shown in Fig. 2C , but are invisible in transmitted light in the absence of ultraviolet radiation.

The figures 3A and 3B illustrate another exemplary embodiment according to the invention in which only the print 13 has an outline defining a pattern M. The Figure 3A is a view in reflected light of the substrate covered with the film 12 and the print 13, and the Figure 3B is a transmitted light view. We see on the Figure 3B that the patterns M formed by the second layer 13 do not appear in transmitted light.

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

A second layer 13 is partially placed on the first layer. This second layer comprises nanometric modifications, preferably it comprises nanometric particles P2.

The 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 so as to form one or more patterns. On this layer 13 is arranged a layer 12 comprising particles P1, preferably goniochromatic particles, more preferably iridescent particles. The plastic material in layer 13 may entirely cover layer 12. In this embodiment, the observation is made from layer 13.

The expression "comprising a" must be understood as being synonymous with "comprising at least one", unless the contrary is specified.

Claims (15)

1. Security article comprising:

   - a first layer (12) at least partially visible in reflected light, the first layer (12):

   - comprising a thermoplastic film including one or more pigments therein, or

   - comprising a binder and at least one pigment dispersed in the binder when the first layer is deposited by printing, by surfacing or by coating,

   - a second diffusing layer (13) at least partially visible in reflected light, partially superimposed on the first layer (12) and modifying the reflectance of the first layer (12) such that at least one pattern that can be observed with the naked eye appears when observed in reflected light by contrast between the first layer (12) alone and the superimposition of the first (12) and second layers (13), the pattern appearing in reflected light not being visible to the naked eye in transmitted light, particularly when the first layer (12) is observed through the second layer (13), the second layer comprising local nanoscale modifications the extent of which is between 1 and 1000 nm.
2. Article according to claim 1, the superimposition of the first layer (12) and the second layer (13) forming a not totally transparent assembly diffusing light at least in part of the visible spectrum.
3. Article according to one of the preceding claims, the first layer (12) comprising one or more first particles (P1), the first particle or particles (P1) being selected from the group consisting of reflective, chromatic, interference, preferably goniochromatic, particularly iridescent particles.
4. Article according to any one of claims 1 to 3, the first layer (12) comprising a thermoplastic film.
5. Article according to any one of the preceding claims, the second diffusing layer comprising a matrix having a refractive index n_matrix and local nanoscale modifications within the matrix having a refractive index n_{modifications} different from that of the matrix having a difference |n_matrix - n_{modifications}| greater than or equal to 0.01, preferably 0.03.
6. Article according to any one of the preceding claims, the second layer (13) being devoid of a goniochromatic pigment.
7. Article according to any one of the preceding claims, the second layer comprising local nanoscale modifications the extent of which is between 1 and 200 nm.
8. Article according to any one of the preceding claims, the second layer comprising particles of greater dimensions of between 1 and 1000 nm, preferably between 1 and 200 nm.
9. Article according to any one of the preceding claims, the second layer comprising mineral particles (P2) preferably of metal oxides or carbonates, more preferably based on silica and most preferably based on pyrogenic silica.
10. Article according to any one of the preceding claims, the second layer comprising particles forming between 20 and 70 % by dry weight, preferably between 30 and 50 % by dry weight of the total weight of the second layer.
11. Article according to any one of the preceding claims, the second layer being partially but not totally superimposed on the first layer.
12. Article according to any one of the preceding claims, the first layer comprising a luminescent, preferably fluorescent and/or phosphorescent substance.
13. Article according to any one of claims 1 to 12, the second layer having a localised diffusing character such that the said pattern appears.
14. Process for authenticating an article (10) according to any one of the preceding claims, in which a user observes the article successively in reflected light, then in transmitted light, compares the appearances observed and thereby obtains information about authenticity as a function of the result of the comparison.
15. Process for the manufacture of an article (10) according to any one of claims 1 to 13, in which a first layer is partially covered by a second layer modifying the reflectance of the first layer such that a pattern that can be observed on the said face appears when observed in reflected light by contrast between the first layer and the superimposition of the first and second layers, this pattern not being visible to the naked eye in transmitted light.

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