WO2022003045A1

WO2022003045A1 - Methods for manufacturing optical security components, optical security components and secure objects equipped with such components

Info

Publication number: WO2022003045A1
Application number: PCT/EP2021/068045
Authority: WO
Inventors: Guillaume Basset; Angélique Luu-Dinh; Vincent TOLLET; Aurélie CHAN YONG
Original assignee: Surys
Priority date: 2020-06-30
Filing date: 2021-06-30
Publication date: 2022-01-06
Also published as: FR3111843A1

Abstract

According to one aspect, the method for manufacturing an optical security component according to the present description comprises providing a multilayer film with a support film (311) and a replication layer (313) comprising a structured face (F) with first regions (R1) and second regions (R2) that form recesses relative to the first regions. The method comprises depositing a first reflective layer (314) on the structured face; depositing (302) a covering layer (315) such that an average thickness of the covering layer at the second regions is strictly greater than an average thickness of the covering layer at the first regions; removing (303) a given thickness of the covering layer by etching so as to leave only the first regions exposed; eliminating (304) the first reflective layer from only the first regions, the at least partially micro- or nanostructured second regions forming, with the reflective layer, at least a first pattern having at least a first optical effect.

Description

Methods of manufacturing optical security components, optical security components and secure objects equipped with such components

Technical field of the invention

The present description relates to methods of manufacturing optical security components, optical security components and secure objects equipped with such components. The optical security components according to the present description apply in particular to security marking for authenticating valuable objects, and more precisely to authentication with the naked eye by observation in reflection and / or in transmission.

State of the art

Many technologies are known for the authentication of valuables and in particular the authentication of valuable documents, such as banknotes or travel documents (passports, identity cards or other official documents), or for the authentication of valuable documents. '' product authentication by means of marking labels. These technologies are aimed at the production of optical security components whose optical effects as a function of the observation parameters (orientation with respect to the observation axis, position and dimensions of the light source, etc.) take characteristic configurations and verifiable. The general goal of these optical components is to provide new and differentiated effects, from physical configurations that are difficult to reproduce or imitate by a forger. These technologies are very varied and implement physical mechanisms such as light diffraction, resonance in waveguides, plasmonic resonances, moiré effects, and any other mechanism aimed at producing animation effects. or colors visible under different observation conditions. Patent applications EP 3634770 [Ref. 1] and EP 3634771 [Ref. 2] thus describe technologies allowing animation effects based on diffraction. Patent applications EP 2695006 [Ref. 3] and EP 2771724 [Ref. 4] describe technologies using plasmonic resonances. Patent applications EP2264491 [Ref. 5] and EP 2567270 [Ref. 6] describe technologies using resonances in a waveguide. Patent applications WO 2019072859 [Ref. 7] and EP 3470235 [Ref. 8] describe technologies implementing moiré effects. Most of the technologies used for the production of optical security components include the manufacture of a multilayer stack with in particular a micro or nanostructured layer on at least one of its faces so as to form, for example, a diffractive grating, a matrix of microlenses. , a Fresnel structure, a chaotic structure, etc. The manufacture of these structures, the pitch of which is sometimes less than the wavelength, requires specific equipment, which makes it possible to obtain, for the optical components thus obtained, excellent performance in terms of preventing counterfeiting.

The multilayer stack also includes a reflective layer arranged on the structured face and allowing an observer to make an optical effect visible in reflection and / or transmission. The reflective layer may be a metallic layer and / or a transparent reflective layer of the high refractive index layer type (or HRI layer according to the abbreviation of the English expression "High Refractive Index").

It is known to form the reflective layer on only part of the structured face, for example according to a given pattern. This makes it possible, for example, when the reflecting layer is made of metal, to keep areas of transparency between the structures. The optical security component can then maintain transparency and allow the visualization of information present on a value object on which the component is affixed or be inserted in a transparency window of the value object, for example a banknote. . Limiting the area covered by the reflective layer can also have the effect of further improving the effect of preventing counterfeiting. For example, when the reflective layer is provided on the structured face in a pattern corresponding to only the micro or nanostructures, the visual effect for an observer is increased at the level of the micro or nanostructures due to the greater contrast with the other unstructured regions. . In general, the methods aiming to laterally structure the reflecting layer on the structured face of an optical security component, that is to say to limit in a controlled manner the area occupied by the reflecting layer, in particular in correspondence with each optical patterns and / or structures, are called “demetallization processes”, when the reflecting layer is made of metal. Methods of lateral structuring of the reflective layer using steps of printing soluble masking varnish or sparing varnish are known (see for example the patent US5145212 [Ref. 9]). These methods require the alignment of the structured face with respect to a mask. Therefore, it is difficult to simultaneously achieve high productivity and high positioning accuracy. Typically, according to this method, an offset between the target position and the contour of the reflecting layer (or “register”) appears during manufacture; such an offset can be between 20 μm and 500 μm.

US patent 9272308 [Ref. 10] describes a method of lateral structuring of the reflective layer which is very rapid and which makes it possible to obtain a selective positioning of the reflective layer on regions of the structured face having different micro or nanostructures with very good precision. In this process, a flash deposition of a protective layer, for example chromium, is deposited on the uniformly applied reflective layer. Due to the difference in depth between the micro or nanostructures of the different regions, the protective layer is not applied in the same way on the different regions and it is thus possible to selectively remove the reflective layer. This method is only applicable, however, in the case of a specific structured face, exhibiting regions with differentiated micro or nanostructures.

The patent application US 20080310025 [Ref. 11] describes an optical security component reproduced in FIG. 1 and a demetallization process making it possible to obtain such a component. As shown in Fig. 1, a replication layer 3 is structured with diffractive structures 4, 5, the diffractive structures 5 having a higher depth / width ratio. Furthermore, a metallic layer 3m is arranged on the replication layer 3 and has demetallized regions 10d which are arranged in perfect coincidence (zero register) with the diffractive structures 5. The transparency of the multilayer stack 100 in the 10d regions is greater than outside these regions at a specific wavelength. The process of demetallization of the reflective metal layer 3m described in [Ref. 11] mentioned above comprises, during the manufacture of the component, the deposition of a photosensitive layer on the metallic layer deposited on the whole of the structured face and the illumination by UV rays of the photosensitive layer on the side of. the face opposite to that bearing the photosensitive layer. In regions 10c which carry the Diffractive structures 5, the resulting metallic layer is naturally more corrugated and locally thinner than in the flat regions 10d. As a result, the photosensitive layer is more illuminated in the structured regions. It is then possible to selectively remove the photosensitive layer in the unstructured regions and then remove the metal in the regions not protected by the photosensitive layer. This method allows self-alignment of the metal layer on the structured regions and therefore exhibits excellent precision. Such a process is, however, strongly dependent on the thickness and the nature of the metal, or more generally on the nature of the reflecting layer and its UV transparency as a function of the thickness. In particular, it is probable that such a method could only be applied with great difficulty in the case of a dielectric reflecting layer instead of the metallic layer due to the low absorption of dielectric materials in the UV. Moreover, such a method does not make it possible to selectively deposit metal on regions having identical micro or nanostructures or different micro or nanostructures but having transmissions similar to the irradiation wavelength (UV), after metallization.

US patent 5,714,213 [Ref. 12] describes an optical security component and a manufacturing method, the steps of which are illustrated in FIG. 2. The method comprises (step 10) replicating a structure in a support material 17 to form a diffractive structure 4 in depressions 21 formed in the support material 17. A printing step (step 11) by means of of an applicator roller 26 makes it possible to apply in precise registration on the surfaces of the unstructured zones 5 a soluble material 25 forming a separation layer. The viscosity and the thickness of application of the soluble material are chosen so that this material does not fill the depressions 21 and does not contaminate the structures in relief 12 forming the diffractive structure 4. The support material 17 is then covered ( step 12) of a reflective layer 14, both on the structures in relief 12 in the depressions 21 and on the separation layer 25. A washing operation (step 13) makes it possible to remove the soluble material 25 with the layer reflective 14 directly applied thereto. The reflective layer 14 is then only present on the diffraction elements 4.

However, such a method requires metallizing on a soluble material, as well as obtaining a dissolution of the soluble material covered with the reflecting layer. 14. Furthermore, the pressure of the applicator roller on the trays which border the depressions 21 could damage micro or nanostructures formed on these trays, thus limiting the possibility of having diffractive structures both in the depressions and on the trays which. surround them.

Patent application DE 102015 010945 [Ref. 13] describes a layered structure for a security element, said structure comprising a plurality of mirror surfaces arranged on relief elements of a surface located opposite a "representation". The mirror surfaces cover between 10% and 90% of the surface and are distributed so that when observed from a first viewing angle, the incident light is reflected from the mirror surfaces and the representation is not visible, while when observing from a second viewing angle, the representation is visible. The method of making such a layered structure includes applying a reflective layer to a relief with elevations and depressions, the metal layer exhibiting poor adhesion with the relief structure. Due to the low adhesion of the metal layer, it can be selectively removed on the elevations by means of a film selectively deposited on the elevations. When the film is removed, the metallic layer is removed along with the film.

Such a process thus requires the use of a specific metallic layer, namely a metallic layer of low adhesion, which can generate weaknesses on the manufactured component.

Patent application JP 2016 114776 [Ref. 14] describes an optical security component and a method of manufacturing such a component, in which the component exhibits a colored effect which depends on the position of the observer, whether it is during an observation from the front side that on the back side. Notably, in an example of a method described in [Ref 14], a relief structure is formed with depressions and elevations. A reflective layer is deposited over the entire structured surface then a colored resin layer is deposited at least at the level of the depressions to protect the metal layer, for example the resin layer is deposited over the entire structure. Then the resin is scraped with a blade to expose the metal layer at the only places of the elevations. The exposed metal layer can then be removed. However, in the process thus described, as in [Ref 12] previously cited, the removal by scraping of the colored resin layer can damage micro or nanostructures formed on the plates, thus limiting the possibility of having diffractive structures at both in depressions and on the plateaus that surround them.

The present description describes a method for the lateral structuring of the reflecting layer in an optical security component which overcomes the drawbacks of the state of the art. In particular, a method according to the present description, beyond having excellent precision in the lateral structuring of the reflecting layer, is universal in that it is suitable for any type of material forming the reflecting layer, and does not depend in particular on 'possible variations in thickness and / or opacity of the reflecting layer, and does not depend on the shape of the macro or nanostructures. Moreover, it does not present the difficulties and the implementation limitations mentioned in particular in relation to the [ref. 12], [Ref.13], [Ref.14]

Summary of the invention

In the present description, the term "include" means the same as "include", "contain", and is inclusive or open and does not exclude other elements not described or shown. Further, in the present description, the term "approximately" or "substantially" is synonymous with (means the same as) a lower and / or upper margin of 20%, for example 10%, of the respective value. According to a first aspect, the present description relates to a method of manufacturing an optical security component comprising the following steps: providing a multilayer film comprising a support film and a replication layer, said replication layer comprising, on a side opposite to the side facing the support film, a structured face with first regions and at least second regions forming depressions with respect to the first regions, such as: said second regions of said structured face of the film layer replication are at least partially micro or nanostructured; a minimum level difference at the border between each first region and each second adjacent region of the structured face of the replication layer is between about 0.5 µm and about 10 µm; depositing on the whole of said structured face of the replication layer at least a first reflective layer; depositing on all of said first regions and said at least second regions of said structured face of the replication layer provided with said first reflecting layer with a covering layer such as an average thickness of the covering layer at the level of the second regions of the replication layer is strictly greater than an average thickness of the covering layer at the level of the first regions of the replication layer; removing, by chemical attack, a given thickness, substantially constant over the entire surface, of said covering layer, so as to leave exposed only the first regions of the replication layer; the elimination of said first reflective layer on the only first regions of the replication layer, said second micro or nanostructured regions of the replication layer forming, with the reflective layer, at least a first pattern carrying at least a first effect optical.

The applicant has shown that such a method allows lateral structuring of the "universal" reflecting layer, that is to say that the method is suitable for any type of material forming the reflecting layer and does not depend on the shape or form. of the nature of micro or nanostructures. Furthermore, the precision of the lateral position of the reflecting layer is excellent with respect to each of the micro or nanostructures, with a zero register or less than about 5 microns, advantageously less than about 2 microns and even less than about 1 micron, of the makes steps of the process implemented. It is thus possible to have an excellent distinction between visual effects produced by first regions and neighboring second regions.

These effects are obtained in particular by providing a replication layer with a face structured so as to have different levels and more precisely first regions and at least second regions forming depressions with respect to the first regions, in such a way that a minimum level difference at the border between each first region and each second adjacent region of the structured face of the replication layer is between approximately 0.5 μm and approximately 10 mch A controlled shrinkage by chemical attack of the previously deposited covering layer to cover all the first and second regions of the structured face then makes it possible to leave only the first regions exposed and to protect the second regions which form depressions with respect to the first regions. The step of removing the reflective layer which follows takes place automatically and precisely on the first regions only, since the reflective layer is protected in the second regions by the covering layer.

According to one or more exemplary embodiments, a minimum level difference at the border between each first region and each second adjacent region of the structured face of the replication layer is between approximately 1 μm and approximately 5 μm, advantageously between approximately 1 μm and about 3 pm. This minimum level difference can be determined as a function of the micro or nanostructurations possibly present on said second regions. Indeed, in the case of microstructurations of the second regions, the minimum level difference may be greater than in the case of nanostructurations.

According to one or more exemplary embodiments, said at least a first pattern is recognizable with the naked eye by an observer.

A pattern carrying an optical effect is recognizable to the naked eye by an observer when it is generated by micro or nano-structured regions s comprising two lateral dimensions in two orthogonal directions greater than 50 μm, preferably greater than 100 μm, more preferably greater than 300 µm.

By "lateral dimension" is meant in the present description a dimension measured in the plane of the component, without any particular reference direction, that is to say in a plane parallel to the support film.

According to one or more exemplary embodiments, some of said first and or second regions of the structured face of the replication layer may form patterns with smaller lateral dimensions, these patterns being produced in order to generate, for example, control elements requiring a control tool. portable or laboratory examination, for advanced control and / or forensic purposes.

According to one or more exemplary embodiments, the provision of the multilayer film comprises:: the replication of a structure on said replication layer by means of a tool comprising a face structured with first regions and at least second regions, such as : the first regions of the tool form depressions from the second regions of the tool such that between a first region of the tool and a second region of the adjacent tool, a minimum level difference between a first mean level of said first region of the tool and a second mean level of said second region of the tool is between about 0.5 µm and about 10 µm, said second regions of the tool are at least partially micro or nanostructured, said replication resulting in said structured face of the replication layer, said first regions and said second regions of the structured face of the replication layer corresponding respectively to said first regions and second regions of the tool.

Replication by means of a tool as described above is advantageous in that it allows large-scale production at low cost. The specific surface of such a tool is little increased compared to a standard tool with no difference in levels and the productivity of the replication is thus not or very little impacted, unlike the techniques requiring the replication of particular structural profiles.

According to one or more exemplary embodiments, the replication comprises hot stamping of a thermoformable replication layer. In other exemplary embodiments, replication can include crosslinking of the replication layer, for example with ultra-violet (UV) radiation.

As regards the tool, the first average level of a first region or the second average level of a second region can be defined, when there are micro or nanostructures, by a plane located at a height corresponding to an average of the heights of the micro or nanostructures.

Furthermore, due to the manufacturing defects of the tool, it is possible that first regions or second regions of the tool have average levels at substantially different heights respectively from other first regions or second regions of the tool. tool. In all cases, the designer will ensure that a minimum level difference between a first average level and a second average level of a first region of the tool and a second region of the adjacent tool is between approximately 0.5 pm and approximately 10 pm This minimum level difference can be determined according to the micro or nanostructurations possibly present on the second regions of the tool. In fact, in the case of microstructurations of the second regions of the tool, the minimum level difference may be greater than in the case of nanostructurations. According to one or more exemplary embodiments, said minimum level difference is between approximately 1 μm and approximately 5 μm, advantageously between approximately 1 μm and approximately 3 μm.

According to one or more exemplary embodiments, the support film comprises polyethylene terephthalate (or PET), polypropylene (PP), Polyethylene (PE), polystyrene (PS) and a thickness of for example between about 6 and about 50 μm .

According to one or more exemplary embodiments, the replication layer a few microns thick comprises a photosensitive resin, a thermosetting resin and / or a thermoplastic resin.

According to one or more exemplary embodiments, said at least one first reflective layer comprises a metallic layer comprising, for example, a metal or an alloy of metals chosen from aluminum, silver, copper, chromium, nickel. The reflecting layer can also comprise a dielectric layer, for example a layer comprising a high index dielectric material (or HRI according to the abbreviation of the English expression “High Refractive Index”), that is to say of refractive index greater than the refractive index of the neighboring layers with a refractive index difference greater than or equal to 0.3, preferably greater than 0.5, for example a layer comprising at least one material chosen from zinc sulphide, oxides titanium dioxide, hafnium dioxide, niobium pentoxide, tantalum pentoxide, zirconium dioxide. According to other exemplary embodiments, the reflective layer may comprise several sublayers of different materials, for example both metallic and dielectric materials, for example to form multilayer coatings interfering with each other. In general, reference may be made to the materials described in LIS Tables 4856857 [Ref. 15] for materials or combinations of materials suitable for forming such a reflective layer.

Furthermore, said at least one first reflective layer can comprise different materials on different zones of the structured face of the replication layer, for example macroscopic zones, that is to say of dimensions. lateral greater than a millimeter in two perpendicular directions. In this case, the step of depositing said at least one first reflective layer may comprise several steps and / or use deposition masks compatible with high productivity manufacturing.

According to one or more exemplary embodiments, a thickness of said first reflective layer is between approximately 20 nm and approximately 200 nm and may vary locally.

According to one or more exemplary embodiments, the covering layer comprises a photosensitive resin or a thermoplastic resin. According to one or more exemplary embodiments, a viscosity of the covering layer is between approximately 1 mPa.s and approximately 100 mPa s, for example between 20 mPa.s and 80 mPa.s. For example, the covering layer comprises a material chosen from a photosensitive polymer resin (for example Novolak ® from Shipley ®), an epoxy resin (for example of the SU-8 type), an embossing resin, a water-soluble polymer resin ( Polyvinylpyrrolidone or Polyvinyl acetate). The thickness of the covering layer is adapted according to the micro / nanostructures present in the first regions and / or the second regions of the structured face of the replication layer and the minimum step height between the first regions and second regions. According to one or more exemplary embodiments, an average thickness of the covering layer at the level of the second regions of the structured face of the replication layer is between approximately 0.5 μm and approximately 20 μm, advantageously between approximately 1 μm and approximately 10 μm and an average thickness of the covering layer at the first regions of the structured face of the replication layer is between about 0.2 µm and about 19 µm, preferably between about 0.5 µm and about 9 µm. The average thickness of the covering layer at said first and second regions can in particular be determined as a function of the minimum height difference between the first and second adjacent regions. Indeed, the covering layer in the present description covers all of the first and second regions of the structured face of the replication layer.

According to the present description, the step of controlled removal of the covering layer (called “development” in the present description) is carried out by a chemical attack, that is to say a chemical etching, for example by wet process. by the controlled dissolution of the covering layer by means of an aqueous-based solution or based on another solvent, or alternatively by dry etching. Dry etching includes in particular reactive ion etching - or reactive ion etching - called by its acronym, RIE. Dry etching allows, like wet etching, the selective and controlled removal of the covering layer without damaging the microstructures.

An aqueous-based solution suitable for chemical attack of the covering layer is, for example, an alkaline solution (comprising, for example, soda, potassium hydroxide or tetramethylammonium hydroxide).

The attack is controlled in its kinetics to obtain a partial attack in thickness. This chemical attack can be carried out, for example, by immersion in a development bath for a predetermined period of time followed by rinsing and / or drying. Stirring the bath, for example mechanically or by ultrasound, can make it possible to obtain, in a known manner, better homogeneity of the bath and of the speed of the chemical attack on a given surface. In the example of a water-soluble covering layer such as polyvinylpyrrolidone, the chemical etching bath for carrying out the development can be composed only of water or of water with additives in limited quantities.

According to one or more exemplary embodiments, the removal of said first reflective layer in said first regions of the structured face of the replication layer is carried out by chemical attack using an aqueous solution, for example a solution containing one or more several acids or one or more bases, for example hydrochloric acid, phosphoric acid, nitric acid, acetic acid, sulfuric acid, cerium and ammonium nitrate. In another exemplary embodiment, a lift-off is used for the removal of said first reflective layer by using an additional sacrificial layer under said first reflective layer, said sacrificial layer and the first reflective layer not being exposed after the controlled removal. of the covering layer than in said first regions.

According to one or more exemplary embodiments, the method further comprises, after the elimination of said first reflective layer on said first regions of the replication layer, a step of removing the covering layer in said second regions of the structured face of the replication layer, as removal can be carried out according to methods similar to those described above, or according to other methods known in the state of the art.

According to one or more exemplary embodiments, the residual covering layer is left in said second regions of the structured face of the replication layer. The covering layer could, for example, be colored so as to produce a colored effect visible to the eye and differentiated according to the viewing side. The covering layer may also include controllable inks in a spectral band different from the band visible to the eye, such as the near infrared (for example centered on 900 nm) or a spectral band located in the Ultra-violet. Finally, it is possible to add to the covering layer other markers such as, for example, chemical reagents ("taggants"), photosensitive or luminescent rare earths.

According to one or more exemplary embodiments, the method further comprises a step of depositing a second reflective layer on the whole of the structured face. This additional step can be carried out, advantageously but not necessarily, following the elimination of said first covering layer on said second regions of the structured face of the replication layer, so that the first and second reflective layers are in direct contact. in said second regions of the replication layer. An optical security component is then obtained with first regions and second regions respectively covered either with the only second reflective layer or with the first and the second reflective layer, which can make it possible to generate differentiated optical effects between the first regions and second regions.

According to one or more exemplary embodiments, said first regions of the structured face of the replication layer are at least partly micro or nanostructured, such that after deposition of said second reflecting layer, said first regions at least partly micro or nanostructures form at least one second pattern carrying at least one second optical effect, for example a second pattern recognizable to the naked eye by an observer.

The second reflective layer may comprise any material cited as an example with reference to the first reflective layer. According to one or more exemplary embodiments, said structured face of the replication layer comprises at least a second region interrupted by a plurality of first regions forming a plurality of micropillars arranged within said second region, a maximum lateral dimension of said micropillars, seen above, being less than about 50 µm, preferably less than about 30 mch, preferably less than about 20 µm, more preferably less than about 10 µm. This plurality of micropillars has as an average distance between the micropillars, preferably a distance between 8 and 100 μm, preferably between 10 and 50 μm. The applicant has shown that such micropillars were particularly useful, during the manufacturing process, in the case of second regions of the structured face of the replication layer having large lateral dimensions, typically dimensions in two directions perpendicular at least equal to 50 pm and up to a few millimeters for example. Such a second region of large dimensions could in fact have a curved “dome” profile rather than a plane profile during a replication step. With micropillars, it is ensured that the covering layer will follow the profile of such a second region and will therefore have a minimum thickness before the controlled removal of the covering layer, and a non-zero thickness after the controlled removal of the covering layer. Furthermore, the maximum lateral dimension makes it possible not to disturb or very little disturb, for an observer, the first optical effect produced by the second region.

According to one or more exemplary embodiments, the method further comprises a step of depositing an adhesive and / or closing layer, continuous or discontinuous. This step can be performed after all of the steps described above.

According to one or more exemplary embodiments, the adhesive layer comprises a heat-reactivatable adhesive. In a preferred embodiment, the adhesive layer comprises one or more polymers having a melting point between 80 ° C and 150 ° C, for example a polyurethane acrylic copolymer in aqueous dispersion and / or a styrene-acrylate copolymer and / or of an ethylene vinyl acetate (EVA) copolymer. In a preferred embodiment, the adhesive layer has a thickness of between about 2 µm and about 25 µm, preferably between about 5 µm and about 10 µm. An adhesive layer may allow the transfer of the optical security component thus manufactured onto a substrate of an object to be secured. According to another embodiment, the adhesive layer comprises a permanent adhesive, for example based on acrylic or rubber, of thickness preferably between about 5 µm and about 100 µm, preferably between about 10 µm and about 60 µm. pm so as to produce a label type product.

According to one or more exemplary embodiments, the adhesive layer is transparent at least in the visible spectral band.

According to one or more exemplary embodiments, the closure layer comprises, for example, a polymethyl methacrylate (PMMA) and has a thickness of between approximately 0.1 μm and approximately 5 μm, preferably between approximately 0.25 μm and approximately 2 μm.

According to one or more exemplary embodiments, the multilayer film comprises a detachment layer arranged between the support film and the replication layer. According to one or more exemplary embodiments, the release layer comprises natural or synthetic wax, preferably of an average thickness of less than approximately 1 μm, preferably less than approximately 0.5 μm. A detachment layer may allow, during the transfer of the optical security component to a substrate of an object to be secured, the detachment of the support film.

According to one or more exemplary embodiments, the multilayer film further comprises a protective layer arranged between the detachment layer and the replication layer. Such a protective layer will allow the protection of the component after transfer of the optical security component onto a substrate of an object to be secured and detachment of the support film.

According to one or more exemplary embodiments, the structured face of the replication layer further comprises at least third regions forming depressions with respect to the first regions, such that a minimum level difference at the border between each first region and every third adjacent region of the structured face of the replication layer is between about 0.5 µm and about 10 µm and strictly less than the minimum level difference between each first region and every third adjacent region of the structured face of the replication layer. replication.

Such third regions form depressions with an intermediate level between the first regions and the second regions. It is thus possible to generate more complex optical effects thanks to multiple reflective coatings and / or perfectly referenced transparency zones.

The manufacturing process may for example include the deposition on the entire structured face of said at least one first reflective layer; the deposition on all of said first, second and at least third regions of the covering layer such that an average thickness of the covering layer at the level of the second regions of the replication layer is strictly greater than an average thickness of the covering layer at level of the third regions, itself strictly greater than an average thickness of the covering layer at the level of the first regions; removing a given thickness of the covering layer, substantially constant over the entire surface, so as to leave exposed the first regions and the third regions of the replication layer; removing the first reflective layer from the first and third regions of the replication layer only; removing the residual covering layer and depositing on the entire structured face at least a second reflective layer; the replication of the process with the deposition and the selective thickness removal of the covering layer so as to leave exposed this time only the first regions of the replication layer; the elimination of the second reflective layer on the first regions only. The method can be followed by a step of depositing a third reflective layer, for example a transparent reflective layer, in the case where at least part of the first regions are micro or nanostructured.

Of course, other sequences of steps are possible depending on the desired results.

According to a second aspect, the present description relates to a method of manufacturing an optical security component comprising the following steps: providing a multilayer film comprising a support film and a replication layer, said replication layer comprising, on a side opposite to the side facing the support film, a structured face with first regions and at least second regions forming depressions with respect to the first regions, such as: said first regions of said structured face of the film layer replication are at least partially micro or nanostructured; a minimum level difference at the border between each first region and each second adjacent region of the structured face of the replication layer is between about 0.5 µm and about 10 µm; depositing on the whole of said structured face of the replication layer at least a first reflective layer; depositing on all of said first regions and said at least second regions of said structured face of the replication layer provided with said first reflecting layer with a covering layer such as an average thickness of the covering layer at the level of the second regions of the replication layer is strictly greater than an average thickness of the covering layer at the level of the first regions of the replication layer; removing, by chemical attack, a given thickness, substantially constant over the entire surface, of said covering layer, so as to leave exposed only the first regions of the replication layer; removing said first reflective layer on only the first regions of the replication layer; depositing on the whole of said structured face of the replication layer at least one second reflecting layer, said first micro or nanostructured regions of the replication layer forming, with said second reflecting layer, at least one first pattern bearing d 'at least a first optical effect, for example a first pattern recognizable to the naked eye by an observer. Such a method, which is an alternative to the method according to the first aspect, once again makes it possible to obtain a zero or almost zero offset between the first regions and the second regions coated with different reflective coatings which may comprise transparent metallic and / or dielectric layers as described above. . In this case, the first pattern carrying at least a first optical effect is formed by the first regions. Of course, the second regions can also be at least partially micro or nanostructured.

According to a third aspect, the present description relates to an optical security component comprising: a multilayer film with a support film and a replicating layer, in which the replicating layer comprises, on a side opposite to the opposite side. backing film, one side structured with first regions and second regions such as:

_ said second regions form depressions with respect to the first regions, a minimum level difference at the border between each first region and each second adjacent region of the structured face of the replication layer is between approximately 0.5 μm and approximately 10 mch, and at least part of said first regions and said second regions are micro or nanostructured; a first reflective layer arranged only on said second regions; a second reflective layer arranged on the whole of the structured face of the replication layer, such that said second regions form at least a first pattern carrying at least a first optical effect and said first regions form at least one second carrier pattern at least one second optical effect, different from said first optical effect.

Such an optical component is remarkable in that it presents, to an observer, a very good contrast between the first regions and the second regions configured to produce differentiated optical effects. This effect is made possible by the second regions formed as depressions with respect to the first regions.

According to one or more exemplary embodiments, the multilayer film further comprises a detachment layer arranged between the support film and the replication layer.

According to one or more exemplary embodiments, the component further comprises a closure layer and / or an adhesive layer deposited on said second reflecting layer.

According to one or more exemplary embodiments, said at least one first pattern and / or said at least one second pattern is recognizable to the naked eye by a user. According to a fourth aspect, the present description relates to a secure object, for example a secure document of value, comprising a substrate and at least one optical security component obtained according to a manufacturing process according to the first aspect and / or at least one optical component. security obtained according to second aspect and / or at least one optical security component according to the third aspect, deposited on said substrate.

Brief description of the figures

Other advantages and characteristics of the invention will become apparent on reading the description, illustrated by the following figures:

[Fig. 1], already described, illustrates an optical security component according to the state of the art described in [ref. 11];

[Fig. 2], already described, illustrates the steps of a process for manufacturing an optical security component, with demetallization, according to the state of the art described in [ref. 12]; [Fig. 3 A] illustrates a first step of a first example of a method of manufacturing an optical security component according to the present description;

[Fig. 3B] illustrates subsequent steps of the first example of a method of manufacturing an optical security component according to the present description;

[Fig. 4] shows an example of a product (top view) of the value document type, secured with an optical security component obtained with an example of the process according to the present description and a sectional view along the line A - A ’of said product;

[Fig. 5A] illustrates a first step of a second example of a method of manufacturing an optical security component according to the present description;

[Fig. 5B] illustrates subsequent steps of the second example of a method of manufacturing an optical security component according to the present description;

[Fig. 6A] illustrates a first step of a third example of a method of manufacturing an optical security component according to the present description;

[Fig. 6B] illustrates subsequent steps of the third example of a method of manufacturing an optical security component according to the present description;

[Fig. 6C] illustrates a top view (partial) of a structured face of an optical security component obtained with a method as described in Figs. 6A and 6B. Detailed description of the invention

In the figures, the elements are not shown to scale for better visibility. In particular, the horizontal and vertical axes are shown at different scales for better visibility. Also on each of the vertical and horizontal axes, the heights and respectively the widths of the different structures and layers can be considerably different, in particular according to the specificities and constraints of implementation.

Figs. 3 A and 3B represent diagrams illustrating steps of a first example of a method of manufacturing an optical security component according to the present description.

Fig. 3A illustrates a first step 301 of replicating a structure on a replication layer 313 of a multilayer film, the multilayer film comprising a support film 311, the replication layer 313 and in this example, a detachment layer 312 (optional ) arranged between the support film 311 and the replication layer 313.

The support film is, for example, a polyethylene terephthalate (or PET) film with a thickness of between about 6 and about 50 μm. The detachment layer 312 is, for example, a layer of natural or synthetic wax, with an average thickness of, for example, between 0.1 μm and 3 μm. The release layer allows during the transfer of the optical security component on a substrate of an object to be secured, to detach the support film. The replication layer 313 comprises, for example, a photosensitive resin or a thermosetting resin with an average thickness of, for example, between 0.5 μm and 20 μm. In exemplary embodiments, the multilayer film can also comprise a protective layer (not shown in FIG. 3A) arranged between the detachment layer 312 and the replication layer 313.

Replication is obtained in this example by means of a tool 30 comprising a face structured with first regions R0i and second regions RO2 such that the first regions of the tool form depressions with respect to the second regions of the tool. As can be seen in FIG. 3A, the second RO2 regions of the tool are at least partially micro or nanostructured. A minimum level difference h between a first average level of a first region R0i and a second average level of a second adjacent region RO2 is between approximately 0.5 μm and approximately 10 μm. This minimum height difference depends in particular on the height of the micro and nanostructures of the second regions. Thus, for example, in the case of second nanostructured RO2 regions, the minimum height difference may be between approximately 1 μm and approximately 3 μm. The shapes and lateral dimensions of the first and second regions of the tool, as well as the micro or nanostructurations of the first and / or second regions will be determined as a function of the patterns sought on the final optical component. A portion of the first and second regions of the tool may have a minimum dimension greater than greater than 50 μm, preferably greater than 100 μm, more preferably greater than 300 μm.

In practice, the tool can be manufactured according to different known techniques such as for example: by holography, using different exposures and doses of coherent light illumination of a photosensitive material, by replication of micro and nanostructures and arrangement of the different structures on at least two levels, carried out for example by replication by lithography (or NIL according to the English abbreviation "nano-imprinting lithography", the NIL processes being considered in the broad sense as the processes of replication of micro and nanostructures), by micro -machining, by laser micro-ablation, by localized etching of a substrate, by plasma and / or laser and / or chemical attack, by three-dimensional printing, by three-dimensional exposure and crosslinking of a material by an electromagnetic wave, or by any other known method or combination of the different methods described above.

As shown in Fig. 3A, the replication step results in a replication layer 313 with a structured face F with first R 1 regions and second R 2 regions forming depressions relative to the first regions.

The first Ri regions and second R2 regions of the structured face F correspond precisely to the first R0i regions and second RO2 regions of the tool respectively, since they are obtained by replicating the structure of the tool in the replication layer.

The methods of industrial replication of optical security components are carried out, for example, by pressing the structured tool 30 mounted on a cylinder on the multilayer film placed between the tool and the backing cylinder. The multilayer film comprises, as described above, in particular the support film and the replication layer. The replication layer can be thermoformable, in this case the tool cylinder is heated to perform hot stamping, or be crosslinkable by radiation, generally by ultraviolet rays. In this case, the replication layer is crosslinked when it is molded with the tool. Fig. 3B illustrates subsequent steps of the method according to this exemplary embodiment. The method comprises a step of depositing on the whole of said structured face F of the replication layer at least a first reflective layer 314 then the deposition (step 302) or “coating” of a covering layer 315 on it. set of first regions and second regions of the structured face of the replication layer provided with the first reflective layer.

The covering layer 315 comprises, for example, a photosensitive resin or a thermoplastic resin.

The coating of the covering layer on the structured face at two levels F of the replication layer is done so as to obtain an average thickness of the covering layer in second regions which is strictly greater than an average thickness of the covering layer in the first regions. This non-homogeneity can be obtained by the properties of the material of the covering layer, such as its surface tension and its viscosity and / or the coating technique used, for example by rotogravure, curtain coating (or "curtain coating" according to the English expression), inkjet printing or offset printing. Thus the difference in average height between the first and second regions at the level of the surface of the covering layer is less than the difference in height between the first and second regions at the level of the surface of the replication layer.

Then follows a step 303 of controlled removal of the covering layer or "development". The shrinkage is controlled in the sense that a predetermined thickness of the covering layer is removed, this thickness being substantially constant over the entire surface, so as to leave exposed only the first regions Ri of the replication layer.

Such a controlled removal of the covering layer without deterioration of the structures is made possible thanks to a removal by chemical attack, for example by wet process, by a controlled dissolution of the covering layer, by means of an aqueous-based or based solution. another solvent.

The solution used for the chemical attack can be adapted in its composition, its concentration and its temperature to the covering layer whose controlled removal must be done. In cases for example where photosensitive resins are used as covering layer, exposed or unexposed according to their positive or negative polarity, development solutions (controlled removal by chemical attack) are available commercially ready to use or to dilute. See for example [Ref. 16] and [Ref. 17] for various solutions supplied by Micro Chemicals ® and information on their use. Photosensitive or thermoplastic resins are of course available from other producers or distributors. Many reference books are also available. [Ref 18] describes for example the dissolution of photosensitive resins. Those skilled in the art can therefore choose the best covering layer and the implementation of its controlled shrinkage by chemical attack as a function of the constraints of implementation, machines, costs and product specifications.

Since the first R 1 regions of the replication layer are the only ones to be exposed, it becomes easy to remove (step 304) the first reflective layer 314 on the first regions, while the reflective layer 314 is protected in the second R2 regions. . In at least part of the micro or nanostructured R2 regions, it is possible to observe at least a first pattern carrying at least a first optical effect recognizable to the naked eye by an observer.

Thus, the method described results in a selective binary masking used as a mask for etching the reflective layer previously deposited (metal and / or HRI). Very good resolution is observed on the resulting optical security component 300 in the selective lateral structuring of the reflecting layer 314.

Fig. 4 shows in diagram 41 an example of product 400 (top view) of the value document type, secured with an optical security component obtained with an example of a method as described in relation to FIGS. 3A, 3B. Figure 42 shows a sectional view along line A - A 'of the product.

As illustrated in diagram 42 of FIG. 4, the secure document 400 comprises a substrate 401 and an optical security component as illustrated for example in FIG. 3B. In diagram 42, a protective layer 318 is shown, initially present between the detachment layer 312 and the replication layer 313. The layer 316 is for example an adhesive layer.

As in the example of the optical security component 300 illustrated in FIG. 3B, in this example, only part of the second regions R2 are micro or nanostructured and coated with the reflecting layer 314. The micro or nanostructurations are for example chosen in a known manner to generate, once coated with the reflecting layer 314, an effect recognizable visual as described for example, but without limitation, in one of the references [Ref. 1] - [Ref. 8] Second regions also may not be micro or nanostructured. Once coated with the reflecting layer, they offer an observer a reflecting pattern, for example a perfectly delimited metallic pattern or an interference layer.

Figs. 5A and 5B illustrate a second example of a method according to the present description.

Fig. 5 A illustrates a first step 501 of replication of a structure on a replication layer 313 arranged on a support film 311. In this example, the support film is for example a polyethylene terephthalate (or PET) film with a thickness of between about 6 and about 50 µm configured to remain on the component and serve as a protective layer. Thus, a layer of detachment is not necessary.

Replication in this example is obtained by means of a tool 30 comprising a face structured with first regions R0i, R0 'i and R0''i and second regions RO2, RO'2 _. As in the method described with reference to FIG. 3A, the first regions of the tool form depressions relative to the second regions of the tool.

In this example, some of the first regions (R0i, R0 ”i) are also micro or nanostructured.

As before, the replication step results in a replication layer 313 with a structured face F with first regions R 1, R ′ and R "i and second regions R2, R’ 2 forming depressions relative to the first regions. The first regions Ri, R'i and R ”i and the second regions R2, R'2 of the structured face F correspond to the first regions R0i, RO'i and R0” i and second regions RO2, R0'2 of the tool respectively, since they are obtained by replicating the structure of the tool in the replication layer.

However, it is observed in this example that the second region R'2 is slightly convex. This unwanted curvature may result from the replication process in the case of second regions of large lateral dimensions, typically greater than 50 microns. When this curvature is too great, this can hamper the implementation of the method and the means described in relation to FIGS. 6A - 6C can be implemented to remedy it. In the event that the side dimensions second regions remain small, typically less than 40 microns, the induced curvature is generally not a problem for the implementation of the method. Fig. 5B illustrates subsequent steps of the method according to this exemplary embodiment and comprises, as previously, a step of depositing on the whole of the structured face F of the replication layer a first reflective layer 314, the coating 502 of a covering layer 315 over all of the first regions and the second regions of the structured face of the replication layer provided with the first reflective layer, the controlled development 503 of the covering layer 315 and the removal 504 of the first reflective layer 314 only in the first regions Ri, R'i and R ”i, the reflecting layer 314 being protected in the second regions R2, R'2. In the example of FIG. 5B, as can be seen in step 504, the method further comprises, after removing the first reflective layer 314 in the first regions only, removing the covering layer in the second regions R2, R'2.

In this example, the method further comprises a step 505 of depositing a second reflective layer 317 on the whole of the structured face and then depositing an adhesive layer 316.

The second reflective layer 317, for example a metallic and / or HRI layer, is in contact with the first reflective layer 314 only in the second regions R2, R'2.

The adhesive layer 316 comprises, for example, a permanent adhesive, configured to be bonded to a substrate of an object to be secured to form an optical security component 500 of the label type.

In the example of fig. 5B, the optical security component 500 is configured to generate several differentiated visual effects. These visual effects result in this example from the first structured regions R 1 coated with the single second reflective layer 317, the first structured regions R'i also coated with the single second reflective layer 317 and the second regions R2, R'2 coated with the second. reflective layer 317 superimposed on the first reflective layer 314.

Figs. 6A to 6C illustrate a third example of a method according to the present description. Fig. 6A illustrates a first step 601 of replication of a structure on a replication layer 313 arranged on a support film 311. In this example, the support film is for example a polyethylene terephthalate (or PET) film with a thickness of between approximately 6 and about 50 µm configured to remain on the component and serve as a protective layer. Thus, a release layer is not necessary.

Replication in this example is obtained by means of a tool 30 comprising a face structured with first regions R0i, RO'i and second regions RO2, R0 '2 _. As in the method described with reference to FIG. 3A, the first regions of the tool form depressions with respect to the second regions of the tool. As in the previous examples, the replication step 601 results in a replication layer 313 with a structured face F with first regions R1, R'i and second regions R2, reforming depressions with respect to the first regions.

In this example, the second region R ’2 present, as in the example with reference to FIG. 5B, large lateral dimensions so that at the time of replication there may result a curvature of the domed region which may interfere with the later stages of coating the cover layer and partial development.

To remedy this effect, in this example, the second region RO'2 of the tool is interrupted by a plurality of first regions POi so that the corresponding second region R '2 of the structured face F of the replication layer 313 is also interrupted by a plurality of first regions forming a plurality of micropillars Pi arranged within the second region R ′ 2, a maximum lateral dimension of said micropillars, seen from above, being less than about 50 μm.

Fig. 6B illustrates subsequent steps of the method according to this exemplary embodiment and comprises, as in the previous examples, a step of depositing 602 on the whole of the structured face F of the replication layer of a first reflective layer 314, the coating 603 of the covering layer 315 over all of the first regions and of the second regions of the structured face of the replication layer provided with the first reflective layer, the controlled development 604 of the covering layer 315 and the elimination 605 of the first reflective layer 314 only in the first regions Ri, R'i and Pi, the layer reflective 314 being protected in the second regions R2, R'2. In the example of FIG. 6B, as can be seen in step 605, the method further comprises removing the covering layer in the second regions R2, R'2.

In this example, the network of micropillars Pi arranged within the second region R'2 of large surface, makes it possible to ensure, during the coating step 603 of the covering layer, that the latter will follow the relief of the covering layer. second region R'2. The micropillars have, for example, lateral dimensions of between approximately μm and approximately 5 μm and are distributed with a period of between approximately 10 μm and approximately 30 μm. The 2D array of micropillars is sparse enough not to disturb the visual appearance of the second micro or nanostructured region coated with the reflective layer 314.

The optical security component 600 thus manufactured is illustrated in a partial top view in FIG. 6C, the component 600 illustrated in FIG. 6B showing a sectional view along the line B - B 'of the partial top view illustrated in FIG. 6C.

As can be seen in Fig. 6C, the micropillars Pi, of lateral dimensions of 3 × 3 μm are regularly spaced every 30 μm on two axes of the plane of the component. Thus, only about 1% of the area encompassing the second region and comprising the plurality of first regions formed by the micropillars no longer contains the first reflective layer 314 after removal thereof in the first regions.

In a manner identical to the methods and products described above, third regions (not shown in the figures), also exhibiting a difference in average height with the first regions and with the second regions, can be provided. These third regions will be able to make it possible to deposit, conserve or remove reflective layers independently of those present on the first and second regions. It will then be possible to generate patterns in the different and more complex optical security components, while maintaining high productivity manufacturing. In general, the structured face of the replication layer can include more than two levels.

The first and second regions can undergo different production operations on separate macroscopic areas (greater than a millimeter on each axis perpendicular to the plane of the component), for example to be covered on one half by a colored metal such as copper having fine metallized / demetallized elements therewith, and another portion by a gray metal such as aluminum having also fine metallized / demetallized elements.

Likewise, these processes can be carried out with non-metallic or non-metallic reflective layers.

The method described in the invention allows high lateral resolution of reflective layer preservation with high manufacturing productivity, and can be combined with any other method which allows the creation of several different areas without providing high lateral resolution. Of course, the examples described by means of the above figures are given by way of illustration and in a nonlimiting manner. They can also be combined.

Although described through a number of exemplary embodiments, the optical security component according to the present description comprises different variants, modifications and improvements which will be evident to those skilled in the art, it being understood that these different variants , modifications and improvements fall within the scope of the invention as defined by the following claims.

References

Ref. 1: EP 3634770 Ref. 2: EP 3634771 Ref. 3: EP 2695006 Ref. 4: EP 2771724

Ref. 5: EP2264491 Ref. 6: EP 2567270 Ref. 7: WO 2019072859 Ref. 8: EP 3470235 Ref. 9: US5145212

Ref. 10: US 9272308 Ref. 11: US 20080310025 Ref. 12: US 5714213 Ref. 13: DE 102015 010945 Ref. 14: JP 2016 114776

Ref. 15: US 4856857

Ref. 16: https://www.microchemicals.com/products/developers.html

Ref. 17: htps: //www.microchemicals.com/technical information / TroubleShooter EN pdf

Ref. 18: Handbook of Semiconductor Technology: Processing of Semiconductors Chapter 4 Photolithography (DOI: 10.1002 / 9783527621828)

Claims

E A method of manufacturing an optical security component (300) comprising the following steps: providing a multilayer film comprising a support film (311) and a replication layer (313), said replication layer comprising, on a side opposite to the side facing the support film, a structured face (F) with first regions (Ri) and at least second regions (R2) forming depressions with respect to the first regions, such as: said second regions regions (R2) of said structured face of the replication layer are at least partially micro or nanostructured; a minimum level difference at the border between each first region and each second adjacent region of the structured face of the replication layer is between about 0.5 µm and about 10 µm; depositing on the whole of said structured face (F) of the replication layer at least a first reflective layer (314); depositing (302) on all of said first regions and said at least second regions of said structured face of the replication layer provided with said first reflecting layer with a covering layer (315) such as an average thickness of the covering layer at the level of the second regions of the replication layer is strictly greater than an average thickness of the covering layer at the level of the first regions of the replication layer; the removal (303), by chemical attack, of a given thickness, substantially constant over the entire surface, of said covering layer, so as to leave exposed only the first regions (Ri) of the replication layer ; the elimination (304) of said first reflective layer on the only first regions (Ri) of the replication layer, said second at least partially micro or nanostructured regions (R2) of the replication layer forming, with the reflective layer, at the at least a first pattern carrying at least a first optical effect.

2. A method of manufacturing an optical security component according to claim 1, further comprising, after removing said first reflective layer on said first regions of the replication layer, a step of removal (504) of the covering layer in said second regions of the replication layer.

3. A method of manufacturing an optical security component according to claim 1, wherein the covering layer is colored.

4. A method of manufacturing an optical security component according to any one of the preceding claims, further comprising, after the step of removing the first reflective layer on the first regions, a step of depositing (505) d 'at least a second reflective layer (317) on the whole of the structured face.

5. A method of manufacturing an optical security component according to claim 4, wherein said first regions (Ri) of the structured face of the replication layer are at least partly micro or nanostructured, such that after deposition of said second reflecting layer (317), said first regions at least partly micro or nanostructured form at least one second pattern carrying at least one second optical effect.

6. A method of manufacturing an optical security component according to any one of the preceding claims, wherein said structured face (F) of the replication layer comprises at least one second region (R '2) interrupted by a plurality of first regions forming a plurality of micropillars (Pi) arranged within said second region, a maximum lateral dimension of said micropillars, seen from above, being less than about 50 µm.

7. A method of manufacturing an optical security component according to any one of the preceding claims, further comprising, after the step of removing the first reflective layer on the first regions, a step of depositing a layer. adhesive and / or closure (316).

8. A method of manufacturing an optical security component according to any one of the preceding claims, wherein the multilayer film further comprises a release layer (312) arranged between the support film (311) and the replication layer.

9. A method of manufacturing an optical security component according to claim 8, wherein the multilayer film further comprises a layer of protection (318) arranged between the detachment layer (312) and the replication layer.

A method of manufacturing an optical security component (300) according to any preceding claim, wherein providing the multilayer film comprises: replicating (301) a structure on said replicating layer (313). by means of a tool (30) comprising a face structured with first regions (R0i) and at least second regions (RO2), such as: the first regions of the tool form depressions with respect to the second regions of the l 'tool such that between a first region of the tool and a second region of the adjacent tool, a minimum level difference (h) between a first average level of said first region (R0i) of the tool and a second average level of said second region (RO2) of the tool is between approximately 0.5 μm and approximately 10 μm, said second regions of the tool are at least partially micro or nanostructured, said replication resulting in said structured face (F ) of the diaper replication, said first regions (Ri) and said second regions (R2) of the structured face (F) of the replication layer corresponding respectively to said first regions (R0i) and second regions (RO2) of the tool.

11. A method of manufacturing an optical security component comprising the following steps: providing a multilayer film comprising a support film and a replicating layer, said replicating layer comprising, on a side opposite to the facing side. -vis of the support film, a face structured with first regions and at least second regions forming depressions with respect to the first regions, such as: said first regions of said structured face of the replication layer are at least partially micro or nanostructured ; a minimum level difference at the border between each first region and each second adjacent region of the structured face of the replication layer is between about 0.5 µm and about 10 µm; depositing on the whole of said structured face of the replication layer at least a first reflective layer; depositing on all of said first regions and said at least second regions of said structured face of the replication layer provided with said first reflecting layer with a covering layer such as an average thickness of the covering layer at the level of the second regions of the replication layer is strictly greater than an average thickness of the covering layer at the level of the first regions of the replication layer; removing, by chemical attack, a given thickness, substantially constant over the entire surface, of said covering layer, so as to leave exposed only the first regions of the replication layer; removing said first reflective layer on only the first regions of the replication layer; depositing on the whole of said structured face of the replication layer at least one second reflecting layer, said first micro or nanostructured regions of the replication layer forming, with said second reflecting layer, at least one first pattern bearing d 'at least a first optical effect recognizable to the naked eye by an observer.

12. Method according to any one of the preceding claims, wherein the removal, by chemical attack, of a given thickness, substantially constant over the entire surface, of said covering layer, comprises the controlled dissolution of the covering layer. , by means of an aqueous-based solution or based on another solvent.

13. Optical security component (500) comprising: a multilayer film comprising a support film (311) and a replication layer (313), wherein the replication layer comprises, on a side opposite to the facing side. of the support film, a structured face (F) with first regions (Ri, R'i) and at least second regions (R2, R '2) such that: said second regions form depressions with respect to the first regions, a minimum level difference at the boundary between each first region and each second adjacent region of the structured face of the replication layer is between about 0.5 µm and about 10 mch, and at least part of said first regions and at least part of said second regions are micro or nanostructured; a first reflective layer (314) arranged only on said second regions; a second reflecting layer (317) arranged on the whole of the structured face of the replication layer, such that said second regions form at least a first pattern carrying at least a first optical effect and said first regions form at least at least one second pattern carrying at least one second optical effect, different from said first optical effect.

14. An optical security component according to claim 13, wherein the multilayer film further comprises a release layer (312), arranged between the support film (311) and the replication layer (313).

15. Optical security component according to claim 14, wherein the multilayer film further comprises a protective layer (318) arranged between the release layer (312) and the replication layer (313).

16. Optical security component according to any one of claims 13 to 15, further comprising an adhesive and / or closure layer (316) deposited on said second reflective layer (317).

17. An optical security component according to any one of claims 13 to 16, wherein said first pattern and / or said second pattern is recognizable to the naked eye by an observer.

18. Secure object (400), for example secure value document, comprising a substrate (401) and at least one optical security component obtained according to a manufacturing process according to any one of claims 1 to 12 and / or at least an optical security component according to any one of claims 13 to 17, deposited on said substrate.