EP3007903A1

EP3007903A1 - Security structure having a diffractive optical element

Info

Publication number: EP3007903A1
Application number: EP14733373.6A
Authority: EP
Inventors: Pierre Sarrazin
Original assignee: ArjoWiggins Security SAS
Current assignee: Oberthur Fiduciaire SAS
Priority date: 2013-06-10
Filing date: 2014-06-10
Publication date: 2016-04-20
Anticipated expiration: 2034-06-10
Also published as: AU2014279723A1; JP2016530118A; FR3006795A1; EP3007903B1; FR3006795B1; WO2014199296A1; AU2014279723B2

Abstract

The present invention relates to a security structure (1) comprising: at least one non-opaque microzone (30), having a section no larger than 1,000,000 µm²; at least one diffractive optical element (40) generating at least one interference pattern (66) in a view plane (62) separated from the diffractive optical element (40), at least partially vertically adjacent to the non-opaque microzone (30).

Description

Security structure with diffractive optical element

The present invention relates to security structures and articles, including documents, secure comprising such structures.

Background

The use of diffractive optical elements (DOEs) as security elements for producing a pattern of interference from a light source is known. These elements can be made to be illuminated by a monochromatic or poly chromatic light, in order to generate the interference pattern by diffraction and transmission through the element to a viewing plane. Depending on the case, this viewing plane can be virtual and located between the element and the light source or be materialized by a real surface located behind the element relative to the source.

International application WO 01/00418 discloses a diffractive optical element made directly on a document by laser ablation.

Australian patent application AU 2013100172 discloses a security document comprising a multitude of openings made by laser ablation generating a diffractive optical element and a reflective layer having on its surface series of grooves and a liquid crystal layer.

International application WO 99/37488 discloses plastic-based security documents in which the diffractive optical element is positioned on or in a transparent or semi-transparent window, so as to be visualized using a collimated polychromatic light source through the presence of another window located on the same document, away from the element.

International application WO 2007/079549 describes the use and visualization of diffractive optical elements on security documents. The elements are made to record individual data, including data otherwise present on the document, such as a portrait or a civil status in the case of a piece of identification.

International application WO 2008/031170 describes the production and use of security documents comprising at least one diffractive optical element and a lens optical structure or another security element having a embossed embossed structure. This application also describes the use and visualization of binary or multi-phase diffractive optical elements. Australian patent application AU 2011101567 describes the use and visualization of diffractive optical elements sensitive to at least three different wavelengths on security documents. The diffractive optical elements are recorded with three different lengths and the interference pattern is reproduced by illumination at the appropriate wavelengths.

There is a need to be able to use diffractive optical elements with different types of substrates without requiring at the time of manufacture of the element the presence of the entire document.

There is also a need to further improve security structures and secure items incorporating such structures, especially to make it more difficult to counterfeit.

The invention aims to meet all or part of these needs.

summary

The subject of the invention is, according to a first of its aspects, a security structure comprising:

at least one non-opaque microzone of less than or equal to

1000000 μιη ² ,

at least one diffractive optical element generating at least one interference pattern in a viewing plane remote from the diffractive optical element, superimposed at least partially on the non-opaque microzone.

Non-opaque microzone

By "non-opaque microzone" is meant an area sufficiently permeable to light to allow visualization of the interference pattern by light passing through this area, having a cross-sectional area of less than or equal to 1000000 μπι ² , better inferior or equal to 200000 μπι ² , even better between 10 μπι ² and 200000 μπι ² , even better between 5000μπι ² and 200000 μπι ² Preferably, the non-opaque microzone has a cross section sufficient to observe the DOE in transmitted light and sufficiently reduced so as not to be substantially visible in reflection. A non-opaque microzone is thus of limited extent, being delimited by an opaque periphery. The non-opaque micro-zone may be translucent, in particular diffuse part of the light passing through it or transparent, not diffusing the light passing through it. Preferably, the non-opaque microzone is transparent. By "an opaque perimeter", it is necessary to include an optical density greater than or equal to 1, more preferably 1.5.

A non-opaque microzone has the advantage of being easily detectable only under certain observation conditions, and is thus not easily visible to the naked eye if these observation conditions are not respected. Thus, the use of a non-opaque micro-zone makes it easier to conceal the diffractive optical element and makes counterfeiting more difficult to achieve.

The non-opaque micro-zone may be of circular or non-circular section, in particular polygonal, in particular polygonal regular or non-regular, or oblong, in particular elliptical.

The non-opaque microzone may be made in a layer of fibrous or non-fibrous material which extends all around the non-opaque microzone.

The non-opaque microzone may be a microperforation of a layer of a substantially opaque material filled at least partially, preferably entirely, with a transparent material including a protective adhesive material. The transparent material, penetrating into the microperforation, makes it possible to secure the layer of substantially opaque material and the layer carrying the diffractive optical element. The fact that the microperforation is at least partially filled protects it from the external environment, including soiling.

For example, the or each non-opaque microzone may be defined by an absence of material within a layer of a substantially opaque material, in particular be defined by a microperforation through this opaque material when it is, for example, a fibrous substrate, or be defined by demetallization when the opaque material is metallic.

In the presence of microperforations, these are preferably carried out using a laser. In a variant, the microperforations are carried out using microneedles or by water jet.

When the non-opaque micro-zone is constituted by a microperforation, the axis of this microperforation is preferably oriented substantially normally to the surface of the layer through which the microperforation is performed. The axis may, alternatively, form an angle with the normal to the surface of the layer which is traversed by the microperforation. The non-opaque microzone may be, when defined by a microperforation, of constant or non-constant cross section over the thickness of the layer traversed by the microperforation.

The non-opaque micro-zone may also be delimited by an impression of an opaque ink, in particular an impression of a transparent plastic film, for example the same film as that on which the diffractive optical element is made.

A same layer of the structure according to the invention may have a plurality of non-opaque microzones superimposed each at least partially on the same diffractive optical element.

The non-opaque micro-zone (s) may each form a pattern that is found in at least a portion of the interference pattern generated by the diffractive optical element.

For example, the non-opaque microzone has a contour that is found in the interference pattern, for example the same geometric shape.

Several non-opaque microzones can together define a pattern that is found in at least part of the interference pattern, for example the image of the same character, place, monument or object, or the same text, for example the value of a break or the name of a bank. The pattern facilitates authentication by the observer by comparing said pattern with the interference pattern. This arrangement increases the security of the document because counterfeiting requires pattern reproduction both in the microzones and in the interference pattern of the security structure.

In the case of a non-opaque micro-zone formed by a microperforation, the thickness of the layer traversed by the microperforation may be between 10 and 1000000 μιη.

The number of non-opaque microzones is preferably between 1 and 1500 non-opaque micro-zones per cm ² , preferably between 10 and 500 per cm ² , more preferably between 10 and 300 per cm ² . Diffractive optical element

The diffractive optical element that generates the interference pattern in a viewing plane remote from the diffractive optical element is preferably of the digital type. Its manufacture is then based, as described in WO 2008/031170, on a stamping performed according to complex data which are reconstructed in the viewing plane to form a pattern of interference in two dimensions. Thus, when the diffractive optical element is illuminated by a collimated light source, it generates an interference pattern producing an image in this viewing plane, which is visible on a surface positioned in this plane, or visible in transmission from this plan.

The mathematical transformation between the element and the visualization plane can be likened to a Fast Fourier Transform (FFT). Thus, complex data, including phase and amplitude information, must be physically encoded in the microstructure of the element. The relief to be given to the microstructure can be calculated by performing the inverse FFT transform of the desired pattern in the viewing plane.

Diffractive optical elements are sometimes referred to as computer generated holograms, and differ from other types of holograms such as rainbow, Fresnel or volume reflection holograms.

Preferably, the diffractive optical element is an embossed structure.

Preferably, the interference pattern generated by the diffractive optical element is found at least partly, better in all, on the security structure, or on the article, in particular the document incorporating it, in particular in the form of an imprint and / or a security element, in particular a watermark, and / or a pattern generated by microperforations or a metallization or demetallization. In the case of microperforations, one of these may define the non-opaque microzone.

For example, the diffractive optical element generates the image of a character and a watermark reproducing the same character is present on a fibrous substrate on which is made a microperforation defining the non-opaque microzone.

The non-opaque microzone may also belong to a security element that reproduces all or part of the interference pattern. For example, the non-opaque microzone is formed by demetallizing a metallized security thread and the image of a character produced by the interference pattern is found on the wire, being formed by demetallization thereon, with or without superposition with the diffractive optical element.

Preferably, the diffractive optical element is smaller, especially in all directions of its plane, than the non-opaque micro-zone. Alternatively, the diffractive optical element may be larger in at least one direction of its plane than the non-opaque microzone.

The diffractive optical element is preferably formed on a thermoplastic film, preferably transparent, having a thickness less than or equal to 50 μπι, in particular by embossing the latter. This thermoplastic film may be laminated at least partially with the layer carrying the non-opaque micro-zone or through which the non-opaque micro-zone is made. Alternatively, the thermoplastic film comprising the diffractive optical element is attached to the non-opaque micro-layer bearing layer by an adhesive structure, preferably also protective, comprising an adhesive material. As described above, the adhesive structure can be introduced in the liquid state between the thermoplastic film and the layer carrying the non-opaque micro-zone by means of at least one microperforation, in particular forming at least one non-opaque micro-zone.

The presence of the thermoplastic film makes it possible to form the diffractive optical element independently of the rest of the secured article, thus to facilitate its manufacture.

The thermoplastic film may be laminated or bonded with a security element, in particular a security wire or foil, having at least one transparent zone, in particular the non-opaque microzone, superimposed at least partially with the diffractive optical element. This security element may have a security pattern, especially in the form of printing, micro-perforations or metallization or demetallization. As indicated above, this pattern may correspond at least partially to the interference pattern produced by the diffractive optical element.

The diffractive optical element can be recorded on the thermoplastic film by a so-called roll-to-roll process.

The diffractive optical element can be visualized under polychromic or monochromatic light.

The diffractive optical element can be associated with an optical, interferential, iridescent or absorbing filter, placed on the path of the light reaching or leaving the optical element diffractive. This filter can belong to the security structure or the article and thus constitute an additional security element as such.

Security structure

The security structure may be in the form of an element which is integrated in a fibrous substrate during manufacture thereof or which is attached to its surface.

The security structure may be in the form of patch, security wire, foil or film.

The security structure may be exposed to the external environment on its two opposite faces or be on only one of them or be covered on both sides by one or more non-completely opaque layers, for example a film protection or varnish.

The security structure can be in one piece at the time of its integration into or on the rest of the article, including the document, or be composed of several sub-elements that are assembled through the rest of the article. article, including the document, for example being reported on different faces of a substrate of the document. These sub-elements may or may not come into contact with each other. For example, a first sub-element may carry the diffractive optical element and second sub-element may bear the associated non-opaque microzone, and the two may be separated by at least one substrate layer of the document or may be directly joined together. with the other.

Preferably, the security structure comprises a protective adhesive structure or an adhesive structure associated with a protective structure disposed between the first sub-element carrying the diffractive optical element, in particular the diffractive optical element and the second sub-element carrying the microzone. not opaque.

"Protective adhesive structure or protective structure" is understood to mean a layer or a plurality of layers intended to protect mechanically and / or optically the diffractive optical element, in particular when the diffractive optical element is an embossed structure.

The protective adhesive structure preferably comprises a layer of a mixture of a high refractive index material (HRI) and an adhesive material which is disposed on the diffractive optical element. Alternatively, the first sub-element comprises a layer of an HRI material, preferably deposited by vacuum vaporization on the diffractive optical element, on which is preferably disposed a layer of an adhesive material, the layer of adhesive material being preferably disposed between the layer of a material HRI and the second sub-element carrying the non-opaque microzone. The superposition of the layer of HRI material and the layer of adhesive material forms the protective adhesive structure. The adhesive layer mechanically protects the diffractive optical element

The HRI material makes it possible to protect the diffractive optical element from attenuation or cancellation of its optical effect that could result from the presence of the adhesive material.

In another variant, the protective structure associated with the adhesive structure comprises a mixture of a high refractive index material (HRI) and a binder, which is arranged on the diffractive optical element, the adhesive structure preferably being arranged on the protective structure, in particular between the second sub-element carrying the non-opaque micro-zone and the protective structure.

As a further variant, the first sub-element comprises a layer of an HRI material disposed, in particular deposited by vacuum vaporization, on the diffractive optical structure, on which is disposed a layer comprising a binder, the superposition of the layer of HRI material and the layer comprising a binder forming the protective structure associated with the adhesive structure. The adhesive structure is preferably disposed on the protective structure, in particular between the protective structure and the second sub-element carrying the non-opaque micro-zone.

Preferably, the binder is secured for example by the presence of a specific marker or a luminescent compound. The layer of HRI material makes it possible to optically protect the diffractive optical element and the binder layer makes it possible to mechanically protect the diffractive optical element.

The HRI material makes it possible to protect the diffractive optical element from attenuation or cancellation of its optical effect that could result from the presence of the adhesive material and / or the layer comprising a binder.

By "an HRI material" is meant a material having a high refractive index, preferably greater than or equal to 1.7. Preferably, the HRI material is selected from zinc sulphide (ZnS), zinc oxide (ZnO), zirconium oxide (ZrO ₂ ), titanium dioxide (TiO ₂ ), carbon (C), indium oxide (In ₂ 0 ₃ ), indium tin oxide (ITO), tantalum pentoxide (Ta ₂ O ₅ ), cerium oxide (CeO ₂ ), lithium oxide (Y ₂ O 3), ₃ ), europium oxide (Eu ₂ 0 ₃ ), ferrous oxides, hafnium nitride (HfN), hafnium carbon (HfC), hafnium oxide (Hf0 ₂ ), lanthanum oxide (La ₃ O ₃ ), magnesium oxide (MgO), neodymium oxide (Nd ₂ O ₃ ), praseodymium oxide (Pr ₆ On), samarium oxide (Sm ₂ 0 _3), antimony trioxide (Sb ₂ 0 _3), silicon carbon (SiC), silicon nitride (SizNu), silicon monoxide (SiO), selenium trioxide (Se ₂ 0 ₃ ), tin oxide (SnO ₂ ), tungsten trioxide (WO ₃ ), combinations thereof and the like.

The protective adhesive structure or the adhesive structure associated with a protective structure may be introduced via one or more microperforations of the second sub-element, in particular at least one microperforation defining a non-opaque micro-zone. The protective adhesive structure or the adhesive structure associated with a protective structure may partially, preferably totally, fill the micro-perforation (s).

Alternatively, the diffractive optical element is disposed on a first side of the first sub-element, the second side of the sub-element having no diffractive optical element and the adhesive structure being disposed between the second sub-element and the second side of the first sub-element. The adhesive structure is therefore not in contact with the diffractive optical element.

The security structure may include a plurality of said diffractive optical elements, each generating an interference pattern in a viewing plane remote from the diffractive optical element.

These diffractive optical elements may generate different or identical interference patterns, supplementing or not.

Preferably, the protective adhesive structure or the protective structure is applied to all the diffractive optical elements.

The security structure may comprise a plurality of non-opaque microzones superimposed each at least partially on at least one respective diffractive optical element. Preferably, a plurality of non-opaque microzones is superimposed on the same diffractive optical element

The non-opaque micro-zone (s) may visually define a pattern that is at least partially reflected in the interference pattern generated by at least one diffractive optical element. For example, a plurality of non-opaque microzones are arranged in an arrangement that reproduces one or more alphanumeric characters, and the interference pattern produces an image of these same alphanumeric characters in the viewing plane. The pattern facilitates authentication by comparing the pattern to the interference pattern. This arrangement further increases the difficulty for the potential counterfeiter that should reproduce the pattern both in the microzones and in the interference pattern of the security structure.

The security structure may comprise at least one absorbing or interferential filter, in particular a color filter, superimposed at least partially on the non-opaque micro-zone.

The security structure may comprise at least two non-opaque microzones each formed by a micro-perforation axis forming an angle with the normal with the surface of the security structure, the angles being different. At least two diffractive optical elements may each be superposed at least partially on a respective non-opaque micro zone. This arrangement makes it possible, by orienting the beam of light differently, to be able to visualize one or the other of the interference patterns produced and to be able to create, for example, an animation by alternately observing the two interference patterns.

Article, including document, secure

The subject of the invention is also an article, in particular a document, which is secure and comprises a security structure according to the invention.

The secure document may comprise a substrate, in particular a fibrous substrate having at least one window, the window being at least partially superimposed on both the diffractive optical element and the non-opaque micro-zone. The security structure can be reported on this substrate or integrated therewith.

The secure article may have at least a second non-opaque microzone, at least partially superimposed on both the diffractive optical element and the non-opaque first microzone. The or each non-opaque microzone can be defined by absence of material, in particular by a microperforation. The microperforations can each be made in a fibrous jet. Observation is done through the two non-opaque microzones.

The secure article may comprise a substrate, in particular a fibrous substrate, comprising a microperforation defining the non-opaque micro-zone, and the diffractive optical element may be present on a security element attached to or integrated with said substrate. In this case, the security structure consists of the security element and the substrate.

The secure article may include a security element having at least one non-opaque microzone superimposed on the diffractive optical element. The latter can be formed on a thermoplastic film, which is assembled, for example by lamination, with the security element, while it is already in place or not on the document.

The secured article can be a passport, an identity card, an access card, a driving license, an interactive playing or collectible card, a means of payment, notably a payment card, a bank note , a tax stamp, a sticker, a voucher or a coupon, a transport, loyalty, service or subscription card, a token or a casino license plate.

The secure article preferably has at least one security element or pattern identical or similar at least partially to the interference pattern.

By "similar", it is understood that the two patterns may be identical to a transformation, including a homothety, have the same shape, present the same information including alphanumeric characters, the typography may be different. Both reasons include, for example, the same written information, including the marital status, the currency of a cut, the name of a place, a date, or the same visual information, including a photograph or a drawing.

Authentication method

The subject of the invention is also a method for authenticating a security structure or an article, in particular a secure document according to the invention, comprising the steps of:

illuminate the diffractive optical element with a light source, - check, especially through the non-opaque micro-zone, the presence of an interference pattern in a viewing plane remote from the diffractive optical element

The light is preferably collimated.

Preferably, during illumination of the diffractive optical element, light passes through the non-opaque microzone before encountering the diffractive optical element and generating an interference pattern.

The light source may be polychromatic, the viewing plane being virtual and positioned between the light source and the security structure. The polychromatic light can be a white light. The pattern of interference is observed through the non-opaque micro-zone that serves as a viewfinder.

The method may include the step of arranging at least one filter, for example colored or interferential, between the light beam and the security structure, or between the viewing plane and the observer.

The presence of the filter makes it possible to select a single wavelength and to more easily see a hidden element that is difficult to see without the filter, particularly in the case of a complex multiton pattern consisting of a superposition of simple patterns of different colors.

As a variant, the light source may be monochromatic, being in particular a coherent and / or collimated light, the viewing plane being real and positioned after the security structure with respect to the light source.

Verification of the presence of an interference pattern can be done using a camera equipped with a camera, including a mobile phone with focus disposed in the viewing plane. The use of a device other than the eye makes it possible to avoid any danger for the eye related to a high luminous intensity, in particular in the case of the use of a laser.

The method may comprise the step of comparing an interference pattern generated by the diffractive optical element with a pattern present on the article, in particular defined by a watermark, an impression, a metallization or demetallization or microperforations, or in a form not directly apprehensible, for example recorded on a RFID chip or on a server to which it can be accessed through a link present on the document. The method may include the step of verifying that the data of the interference pattern corresponds to data otherwise provided by the document.

In the case of observation of the pattern of interference generated by the diffractive optical element by an electronic device, the latter can be arranged to automatically analyze the image observed and for example compare it to reference information, or decrypt it to extract information compared to reference information, to verify the authenticity of the article, including the document.

The electronic device can be arranged to analyze the interference pattern observed and access a database to verify the authenticity of the article, including the document.

The article, in particular the document, may carry information that makes it possible to access, via a remote server, reference data that make it possible to verify that the image observed originates from an authentic diffractive optical element.

This information can be stored in an RFID chip present on the document and read by the device used to observe the interference pattern, for example using FC technology.

The invention will be better understood on reading the following detailed description, non-limiting examples of implementation thereof, and on examining the appended drawing, in which:

FIG. 1 schematically represents an example of a secure document according to the invention, FIG. 2 is a section along II - II of FIG. 1, FIGS. 3 to 6 are views similar to FIG. 2, variant embodiments. FIG. 7 schematically represents another example of a secure document according to the invention, FIG. 8 is a section along VIII-VIII of FIG. 7, and FIG. another example of a secure document according to the invention, FIG. 10 is a section along XX of FIG. 8, FIG. 11 schematically shows another example of a secure document according to the invention, FIG. 12 is a section along XII-XII of FIG. 10, FIG. is a view similar to that of FIG. 12, FIGS. 14 to 20 show other examples of safety structures according to the invention, FIGS. 21 and 22 represent, in section, variants of safety structures according to the invention. FIGS. 23 to 26 are views similar to FIG. 2, variant embodiments of the example of FIG. 1, FIG. 27 represents another security element according to the invention, FIGS. 28A and 28B represent FIGS. variants of the non-opaque microzone, and - Figures 29 and 30 schematically illustrate the visualization of the interference pattern.

In the schematic figures, the actual relative proportions of the different constituent elements have not necessarily been respected, for the sake of clarity of the drawing. Some layers may have been monolithically represented for the sake of simplification, whereas they may consist of several sub-layers in reality. In addition, some layers can be assembled by the use of adhesive layers arranged between them, which are not always shown in the figures. Finally, in the presence of juxtaposed opaque and non-opaque zones, this presence has been represented only schematically with only two zones arranged side by side, it being understood that in reality these different zones will be more often than two, with arrangements that can be complex, to define a text or a raster image for example. The diffractive optical element has been represented very simply and schematically in the figures. The possible surface reliefs caused by a possible embossing are not particularly represented, this does not exclude their possible presence.

The secure article 10 shown in FIGS. 1 and 2, for example a document such as a banknote, comprises a security structure 2 according to the invention, comprising a diffractive optical element 40 superimposed at least partially on a non-microarray. opaque 30.

Article 10 comprises a substrate 1 1, in particular paper, provided with a window 15 which visually gives access to the diffractive optical element 40.

In the example considered, the non-opaque micro-zone 30 is formed by an X-axis microperforation made through a substrate 18, in particular paper, of the document 10, assembled with the substrate 11.

The diffractive optical element is made on a transparent plastic film 43, which is assembled with a security element 20 having a non-opaque zone 23 superimposed at least partially on the diffractive optical element 40 and the microperforation 30.

The thermoplastic film 43 may be polyethylene terephthalate (PET).

The diffractive optical element 40 generates an interference pattern in a distant viewing plane.

The at least partial alignment of the various openings and transparent zones defines a non-opaque zone A which goes on both sides of the secure document 1.

Referring to FIGS. 29 and 30, examples of methods of visualization of the security structure 2 according to the invention will be described.

The interference pattern of the security structure 2 is visualized by illuminating the non-opaque micro-zone 30 with a light source 60 in a plane 62 remote from the diffractive optical element 40.

The security structure 2 is preferably arranged so that its plane is oriented orthogonally to the incident light from the light source 60 and the non-opaque micro-zone 30 is preferably positioned on the side of the light source. 60.

The non-opaque micro-zone 30 makes it possible in particular to aim the diffractive optical element 40 with the incident beam. The light source 60 is preferably collimated.

As illustrated in FIG. 29, the light source 60 may be a source of monochromatic light, in particular a laser. The viewing plane 62 is then real and is positioned downstream of the security structure 2 with respect to the light source 60. The interference pattern 66 may be viewed using a portable device, in particular of a mobile phone set in photo or video mode and positioned in the viewing plane 62. The interference pattern 66 is displayed through the non-opaque micro-zone 30.

As illustrated in FIG. 30, the light source 60 may be a polychromatic source. The viewing plane 62 is then virtual and positioned upstream of the security structure 2 with respect to the light source 60. The visualization of the interference pattern 66 is done by observing the light source 60 through the non-microzone. opaque 30.

Authentication of the security structure 2 may require the use of a filter 68 positioned upstream or downstream of the security structure 2. This filter can be used to filter the wavelengths visible to the eye.

Authentication of the security structure 2 can be done by comparing the interference pattern 66 generated by the diffractive optical element 40 with one or more additional information present on the security structure 2 or the associated article 10 for example to a comparison pattern defined by a watermark, an impression, a metallization or demetallization or micro-perforations. The non-opaque microzone 30, being in particular a demetallization or a microperforation, may constitute, at least partially, the comparison pattern.

The invention is not limited to a particular secure article, and it may be other than a valuable document, including an identity document or a card. The substrates 11 and 18 of the example of FIGS. 1 and 2 can thus be non-fibrous.

The diffractive optical element 40 may be formed on a thermoplastic film 43 according to one of the methods described above. The thickness e of the diffractive optical element 40 is preferably less than or equal to 50 μπι, better than or equal to 25 μιη.

The diffractive optical element 40 may be, as illustrated in FIG. 2, of larger section than that of the non-opaque micro-zone 30. The non-opaque micro-zone 30 preferably has a section S of less than 1000000 μπι ² , better still less than or equal to 200,000 μιη ² , and even more preferably between 10 μηι ² and 200,000 μιη ² , and even more preferably between 5000 μιη ² and 200,000 μιη ^2.

The non-opaque micro-zone 30, when made in the form of microperforation, can be arranged in various ways.

As illustrated in FIG. 14, the non-opaque micro-zone 30 may have a variable section, in particular narrowing in the direction of the diffractive optical element 40.

FIG. 15 shows a non-opaque micro-zone 30 formed by a microperforation whose X axis forms a non-zero angle α with the normal on the surface of the security structure 2. The angle α may be between -45 ° and 45 °.

As illustrated in FIG. 16, the security structure 2 may comprise at least two non-opaque micro-zones 30 ₁ and 30 ₂ opening on the same surface S ₁₂ , each non-opaque micro-zone 30 ₁ and 30 ₂ being superposable on a diffractive optical element 40i or 40 ₂ respectively. This configuration makes it possible, by varying the viewing angle, to choose the diffractive optical element that one wishes to visualize. An animation can, if necessary, be observed by alternating the visualization of the two interference patterns.

The non-opaque microzone 30 may be made other than in the form of a microperforation through an opaque layer.

As illustrated in FIG. 17, the non-opaque micro-zone 30 may be filled with a non-opaque transparent material, colorless or otherwise.

As illustrated in FIG. 18, the non-opaque micro-zone 30 may be delimited by an impression 35. The layer 38 on which the printing is performed may be a transparent film which bears, on the face opposite to the printing, the element diffractive optics 40.

Alternatively, the non-opaque microzone 30 may be formed by demetallizing a metal layer 37 as shown in FIG. 19.

The security structure 2 may comprise an optical filter placed in the path of the light gaining or leaving the diffractive optical element.

FIG. 20 shows a security structure 2 comprising an optical filter 80, absorbing or interferential, in particular colored, superimposed on the non-opaque micro-zone 30. The filter 80 may be positioned upstream or downstream of the diffractive optical element 40. The filter 80 makes it possible to select one or more wavelengths of the light during the visualization of the interference pattern. The filter makes it possible to obtain a customization of the interference pattern by allowing the choice of the visualization color.

As illustrated in FIG. 21, the security structure 2 may comprise a plurality of diffractive optical elements 40i, 40i and respective non-opaque microzones 30i,..., 30i of respective axes Xi,..., Xi, each non-opaque microzone 30i; ...; 30i superimposed on a diffractive optical element 40i; ...; 40i corresponding.

The security structure 2 may comprise a security element 20 comprising one or more non-opaque zones 23, each non-opaque zone overlapping at least partially with at least one diffractive optical element 40i, 40i. A non-opaque zone 23 may be superimposed with at least two diffractive optical elements 40 _u ..., 40i.

In the variant shown in FIG. 23, the security structure 2 comprises a plurality of color filters 60i,..., 60i, in particular of different colors, each superimposed on at least one respective diffractive optical element 40i,. 40i.

It can be seen in FIG. 2 in particular that the security structure 2 may comprise a security element 20 which is at least partially superimposed on the diffractive optical element 40 and the non-opaque micro-zone 30. More particularly, as illustrated, this element of security 20 can be visible through the window 15 and interposed between the substrate 11 and the film 43 carrying the diffractive optical element 40.

The security element 20 is preferably at least partially opaque, being for example metallized.

The non-opaque zone 23 may be formed by demetallization or perforation.

The element 20 can provide visible security through the window 15, for example in the form of a pattern 50 located outside the non-opaque zone 23, this pattern 50 being for example formed by printing or demetallization, as illustrated in FIG. figure 1.

The pattern 50 is for example composed of alphanumeric characters, as shown in Figure 1. It may be a text indicating the name of the bank, the country and / or the value of the cut. The pattern 50 can be produced in accordance with the teaching of the application WO 2006/066927, in the form of raster points rendering an image in transmitted light, one of the demetallizations or perforations of the pattern 50 that can constitute the non-opaque micro-zone 30.

The pattern 50 is found, preferably, partially or totally in the interference pattern 66 generated by the diffractive optical element 40. For example, in FIG. 1, the pattern 50 representing the value of the cutoff is found in FIG. interference pattern that also represents the value of the cut, the typography may be the same or different.

In general, in the case of a security element 20 comprising a metallized layer, as usable metals, mention may be made of aluminum, copper, gold, iron, silver and chromium. , nickel, zinc, cadmium, bismuth and their alloys and oxides.

The security element 20 may be in the form of a patch, a wire or a foil security.

In the case where the security element 20 is a security thread, its width may be relatively small, preferably less than or equal to 10 mm.

The window 15 may be made by cutting and have an outline of any shape, for example circular, elliptical or polygonal, as shown in Figure 1, especially in the form of a regular polygon or not.

The window 15 may be unique on the document or the document may comprise several. In this case, the windows 15 can be arranged on the same face of the document or on opposite faces.

The window 15 may be formed by modifying, for example, the accumulation of fibers on the forming wire and the non-opaque micro-zone 30 may be formed in particular by means of micro-needles or by water jet, preferably by laser ablation. . The jets 11, 18 are, for example, fibrous jets assembled in the wet phase.

The two jets 11, 18 each have a thickness / for example between 10 and 1000 μπι, better between 50 and 700 μπι.

The two jets 11, 18 may comprise natural and / or synthetic fibers.

Substrates 11 and 18 may still be non-fibrous. More generally, the document 10 may have a multilayer structure comprising at least one fibrous layer and a layer of thermoplastic material.

Preferably, the diffractive optical element 40 is laminated with the security element 20 before being incorporated in the secure document 1.

Alternatively, the diffractive optical element 40 is attached to the security element 20 by gluing, hot or cold. The adhesive used is, for example, a transparent adhesive of the polymer adhesive type such as NOLAX.

The assembly composed of the security element 20 and the diffractive optical element 40 can be incorporated between the two jets 11, 18, the security element 20 being positioned on the side of the window 15, as illustrated in FIG. 2.

In general, Article 10 may include various ancillary, first-level, second-level or third-level security features. Among the additional security features, some are detectable to the eye, daylight or artificial light, without the use of a particular device. These security elements comprise for example colored fibers or boards, fully or partially printed or metallized wires. These security elements are called first level.

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

Other types of additional security elements require for their detection a more sophisticated detection device. 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 comprise, 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. At least one of these security elements can define information found in the interference pattern generated by the diffractive optical element 40.

The diffractive optical element 40 and the layer 18 defining the non-opaque microzone 30 may be in contact with each other, as is the case particularly in the example of FIG. 2.

Alternatively, the diffractive optical element 40 and the layer 18 defining the non-opaque microzone 30 may be separated by one or more intermediate layers.

For example, as illustrated in FIG. 3, the film 43 carrying the diffractive optical element 40 can be positioned adjacent to the substrate 11 comprising the window 15, and the security element 20 can be interposed between the film 43 and the non-opaque microzone 30.

Preferably and as illustrated in FIG. 23, the diffractive optical element 40, in particular the side of the film 43 carrying the latter, and the layer 18 are separated by a protective adhesive structure 45 preferably comprising a layer of a mixture of a adhesive material and a material HRI. The protective adhesive structure 45 makes it possible to secure the film 43 carrying the diffractive optical element 40 and the layer 18. The presence of the material HRI makes it possible to prevent the attenuation or cancellation of the optical effects of the diffractive optical element which could caused by the superposition of adhesive material with the diffractive optical element 40.

The diffractive optical element 40 may, in a variant, carry a layer of an HRI material 47, in particular deposited on the diffractive optical element 40 by vacuum vaporization, itself carrying a layer of an adhesive material. In this case, the layer 47 serves to protect the diffractive optical element 40 against attenuation or cancellation of its optical effect due to the presence of the adhesive structure. The mechanical protection of the latter is obtained by the layer of adhesive material 46.

Alternatively, as illustrated in FIG. 24, the diffractive optical element 40, in particular the side of the film 43 carrying the latter, and the layer 18 are separated by an adhesive structure 46 comprising an adhesive material and a protective structure 47 comprising a material HRI, the protective structure 47 being applied to the diffractive optical element 40, in particular on the side of the film 43 carrying the diffractive optical element 40 and the adhesive structure 46 being disposed between the protective structure 47 and the layer 18.

The protective structure 47 may comprise a binder, preferably secured. In the variant illustrated in FIG. 25, the film 43 and the layer 18 are separated by an adhesive structure 46, the latter being situated on the side of the film 43 that does not have the diffractive optical element 40. A protective structure 47 comprising a material HRI may be present on the diffractive optical element 40, and in particular completely cover the latter. This protective structure 47 makes it possible in particular to mechanically protect the diffractive optical element 40 during the assembly of the security structure 2 with the article 10 while retaining the optical properties.

In the variant illustrated in FIG. 26, the film 43 and the layer 18 are separated by a protective structure 47 comprising a layer of an HRI material 47a, a layer of a binder 47b and an adhesive structure 46 comprising an adhesive material. The layer of HRI material 47a preferably covers at least partially the diffractive optical element 40 and the binder layer 47b preferably covers the layer of HRI material 47a.

Preferably, the binder is secured, in particular by one or more luminescent or absorbent substances under UV, visible and / or IR excitation. Preferably, the luminescent or absorbing substances are non-diffusing and the binder layer 47b is transparent. The luminescent or absorbing substances are preferably particles of nanometric sizes.

Preferably, the layers 47a, 47b and 46 are transparent so as not to disturb the optical effect generated by the diffractive optical element.

The deposition of the protective structure 47 can be done by printing on the diffractive optical element 40 as explained in the patent application FR 2961319, that is to say that the hollows of the diffractive optical element 40 are filled with the HRI material.

The protective structure 47 or the protective adhesive structure 45 may comprise nanoparticles of metal oxides, such as TiO 2, having in particular a diameter of between 1 and 100 nm, better still between 5 and 25 nm and / or a transparent varnish and / or a crosslinkable organic binder and / or a pigment dispersant. The thickness of the protective adhesive structure 45 is preferably between 1 and 10 microns, more preferably between 2 and 5 microns.

Preferably, the adhesive structure 46 or the protective adhesive structure 45 is introduced by the microperforations between the diffractive optical element 40, and / or the film 43 carrying it, and the layer 18. Preferably, as illustrated in FIGS. 24, the layers 46 or 45 are introduced so as to fill the microperforations to protect them against the external environment, including soiling, as explained in the application DE 10 2011 004935.

As illustrated in FIG. 4, the security element 20 can be positioned in the window 15, the film 43 still extending between the two jets 11 and 18.

The diffractive optical element 40 may be made of a film 43 which extends continuously around the diffractive optical element 40. In a variant, the film 43 which was used to produce the diffractive optical element 40 does not extend to beyond this, as shown in Figure 5.

As illustrated in FIG. 6, the film 43 can be positioned in the window

15. The same can be said of the security element 20, when present.

As illustrated in FIGS. 7 and 8, the security structure 2 may comprise a diffractive optical element 40 and a security element 20 having a non-opaque micro-zone 30 superimposed at least partially on the diffractive optical element 40.

The first jet 11 may have a window 15 and the second jet 18 may have a non-opaque zone 32. The window 15 and the non-opaque zone 32 may or may not have the same shape and size and overlap at least partially with the element diffractive optics 40 and non-opaque microzone 30 so as to form a transparent through area A on the secure document 1. The security structure 2 may have substantially the same shape as the window 15 and be positioned in the latter.

The secure document 1, shown in FIG. 9, comprises two substrates 11, 18 constituted by first and second jets 11, 18 each provided with a microperforation 30, 16, preferably made by laser ablation, and receive between them an element diffractive optics 40. The diffractive optical element 40 and the two microperforations 30, 16 are superimposed.

The secure document 1, shown in FIG. 11, comprises a first substrate 11 forming the first jet, provided with a window 15, and a second substrate 18 forming the second jet, provided with a non-opaque micro-zone 30. The window 15 and the microperforation 30 are superimposed so as to form in the secure document a transparent area A which goes on both sides of the secure document 1 in which positions the diffractive optical element 40.

As illustrated in FIG. 12, in particular when the diffractive optical element 40 is carried by a thermoplastic film 43, the diffractive optical element 40 can be positioned between the two jets 11, 18, the film 43 being in direct contact with those -this.

As illustrated in FIG. 13, the optical security element 40 can be positioned between a substrate 18 and a security element 20, the substrate comprising the non-opaque micro-zone 30.

As illustrated in FIG. 27, the security element 20 may comprise a pattern 50, here the letters AW, produced by a plurality of microperforations 19, one of these microperforations possibly constituting the non-opaque micro-zone 30, for example the tip. A. The pattern AW can be reproduced on the interference pattern generated by the diffractive optical element 40.

The non-opaque micro-zone 40 may be of various shapes, in particular circular, as illustrated in FIG. 1, or any other, for example triangular as illustrated in FIG. 28A, or crescent-shaped, as illustrated in FIG. 28B.

The invention is not limited to the illustrated examples.

The particularities of the examples illustrated can be combined within non-illustrated variants.

The expression "comprising one" is synonymous with "having at least one", except when the opposite is specified.

Claims

Safety structure (2) comprising:

at least one non-opaque micro-zone (30), of section less than or equal to 1000000 μιη ² ,

at least one digital type diffractive optical element (40) generating at least one interference pattern (66) in a viewing plane (62) remote from the diffractive optical element (40), superimposed at least partially on the non-microarray opaque (30).

2. Structure according to claim 1, the non-opaque micro-zone (30) being defined by an absence of material within a layer (18; 20) of a substantially opaque material.

3. Structure according to claim 1 or 2, the non-opaque micro-zone (30) being defined by a microperforation.

4. Structure according to claim 1 or 2, the non-opaque micro-zone (30) being defined by a demetallization.

5. Structure according to any one of the preceding claims, the non-opaque micro-zone (30) being delimited by an impression of an opaque ink.

6. Structure according to any one of the preceding claims, the non-opaque micro-zone (30) having a cross section less than or equal to 200000 μπι ² , even better between 10 μπι ² and 200000 μπι ² , even better between 5000μπι ² and 200000. μιη ²

7. Structure according to any one of the preceding claims, the interference pattern (66) generated by the diffractive optical element (40) being found at least partly, more completely, on the security structure (2), or on the article (10) incorporating it, especially in the form of printing, a watermark, a pattern generated by microperforations or a metallization or demetallization.

8. Structure according to any one of the preceding claims, the interference pattern (66) being found at least partly, better in all, on the security structure (2) or the article (10) incorporating it, in the form of a pattern generated by microperforations (19), one of which defines said non-opaque micro-zone (30).

The structure of any one of the preceding claims, wherein the non-opaque patterned microzone (30) is found on at least a portion of the interference pattern (66), more preferably the same or similar to it.

10. Structure according to any one of the preceding claims, comprising a protective adhesive structure (45) disposed between the diffractive optical element (40) and a sub-element carrying the non-opaque micro-zone (30).

11. Structure according to claim 10, the protective adhesive structure (45) comprising a mixture of an adhesive material and a material HRI.

12. Structure according to claim 10, the protective adhesive structure (45) being formed of a layer of a material HRI, preferably deposited by vacuum vaporization on the diffractive optical element, and a layer of a material adhesive.

13. Structure according to any one of claims 10 to 12, the protective adhesive structure (45) filling at least partially, more completely, at least one microperforation.

14. Structure according to any one of claims 1 to 9, comprising an adhesive structure (46) associated with a protective structure (47) disposed between the diffractive optical element (40) and a sub-element carrying the non-opaque micro zone (30).

The structure of claim 14, the protective structure (47) comprising a mixture of a HRI material and a binder and being applied to the diffractive optical element (40).

16. Structure according to claim 14, the adhesive structure (46) being disposed between a sub-element bearing the non-opaque microzone (30) and the protective structure (47).

17. Structure according to any one of claims 1 to 9, the protective structure (47) being formed of the superposition of a layer of an HRI material (47a) and a layer comprising a binder (47b), the layer comprising a binder (47b) being disposed on the layer of HRI material (47a).

18. Structure according to any one of claims 14 to 17, the adhesive structure (46) being disposed between a second sub-element carrying the non-opaque micro-zone (30) and the side without a diffractive optical element (40) of a first sub-element carrying the diffractive optical element (40).

19. Structure according to any one of claims 14 to 18, the adhesive structure filling at least partially, more completely, at least one mi croperforati on.

20. Structure according to any one of the preceding claims, the diffractive optical element (40) being formed on a thermoplastic film (43), preferably transparent, having a thickness less than or equal to 50 μπι.

21. Structure according to claim 20, the thermoplastic film (43) being laminated with an at least partially opaque layer (20) defining said non-opaque micro-zone (30).

22. Structure according to claim 21, the thermoplastic film (43) being laminated with a security element (20), in particular a security wire or foil, having at least one transparent zone (23) superimposed at least partially with the diffractive optical element (40) and a security element in particular in the form of printing, a watermark, a pattern generated by microperforations or a metallization or demetallization.

23. Structure according to any one of the preceding claims, comprising a plurality of said diffractive optical elements (40) and a plurality of non-opaque micro-zones (30), in particular each overlapping at least partially with at least one diffractive optical element (40). respective.

24. Structure according to any one of the preceding claims, comprising at least one optical filter (80), in particular a color filter, overlapping at least partially with the non-opaque micro-zone (30).

25. Structure according to any one of the preceding claims, constituting a patch, a foil or a security thread.

26. Structure according to any one of claims 1 to 25, comprising an at least partially opaque fibrous layer (18) defining said non-opaque micro-zone.

27. Secure article (10) comprising a security structure (2) according to any one of claims 1 to 26.

28. Secure article according to claim 27, comprising a substrate (11), in particular fibrous, having at least one window (15), this window (15) being at least partially superimposed both on the diffractive optical element (40) and on the first non-opaque micro-zone (30).

A secure article according to claim 27, comprising a substrate (11) having at least a second non-opaque micro-zone (16), the second non-opaque micro-zone (16) being at least partially superimposed on both the diffractive optical element ( 40) and the non-opaque micro-zone (30).

30. Secure article according to any one of claims 27 to 29, the article being a passport, an identity card, a driving license, an interactive playing or collecting card, a means of payment, including a card a bank note, a voucher or a voucher, a secure label, a transport card, a loyalty card, a service card or a subscription card, or a specific payment method such as 'a token or a wafer especially used in casinos.

31. Secure article according to any one of claims 27 to 30, having at least one security element or pattern identical or at least partially similar to the interference pattern (66).

32. The method of authenticating a security structure according to any one of claims 1 to 26, comprising the steps of:

illuminating the diffractive optical element with a light source (60), checking, especially through the non-opaque micro-zone, the presence of an interference pattern (66) in a viewing plane (62) remote from the diffractive optical element (40).

33. The method of claim 32, the verification of the presence of an interference pattern (66) is using a camera equipped with a camera, including a mobile phone.

The method of any one of claims 32 to 33, including the step of comparing the interference pattern (66) generated by the diffractive optical element (40) and a pattern (50) present on the document, in particular defined by a watermark, an impression, a metallization or demetallization, or micro-perforations.