Method for manufacturing a three-dimensional item with metal pattern(s)

Abstract

The invention relates to a method for manufacturing a three-dimensional item comprising at least one metal pattern, comprising at least: - a step A of providing a flat substrate made of thermoformable material; - a step B of forming, on a surface of the flat substrate, a temporary masking coating which adheres to said surface, in order to obtain a masked substrate having at least one unmasked zone; - a step C of thermoforming the flat substrate in order to give the latter a three-dimensional general shape; - a step D of metallizing the masked substrate in order to form a metal deposit on the latter at least on said unmasked zone; - and a step E of removing said temporary masking coating, the thermoforming step C being carried out before the metallization step D and before the step E of removing said temporary masking coating, the metallization step D being carried out by non-electrolytic deposition from one or more metallization solutions containing at least one metal in the form of a metal cation and at least one reducing agent capable of transforming the metal cation into metal, by spraying the metallization solution or solutions in the form of one or more aerosols. The invention also relates to a method for manufacturing three-dimensional items with metal pattern(s).

Description

[0001] METHOD FOR MANUFACTURING A THREE-DIMENSIONAL ARTICLE WITH METAL PATTERN(S)

[0002] TECHNICAL FIELD

[0003] The present invention relates to the general technical field of three-dimensional articles provided with metallic, decorative and / or functional pattern(s).

[0004] The invention relates more specifically to a method of manufacturing a three-dimensional article comprising at least one metallic pattern.

[0005] PRIOR TECHNIQUE

[0006] In the field of manufacturing objects decorated with metallic patterns, processes are already known which consist of producing or affixing metallic patterns to the surface of a three-dimensional semi-finished object, such as for example a glass or plastic flask or bottle, by additive techniques (for example, by screen printing or pad printing using a metallic ink, or by applying a metallic film by hot stamping) or subtractive techniques (for example, by metallization of the surface of the object then selective laser engraving). Although allowing particularly aesthetic decorative effects, these techniques nevertheless prove to be expensive and difficult to implement for extensive patterns.Furthermore, they are very difficult, if at all, to apply for the decoration of three-dimensional semi-finished objects of complex geometry / topography, so that they are generally implemented only on substantially flat or cylindrical surface portions of prefabricated three-dimensional semi-finished objects.

[0007] In the field of printed electronics, methods are known for manufacturing three-dimensional articles or objects locally covered by electrically conductive metallizations, in which conductive patterns are produced on a thermoplastic polymer substrate by direct printing (screen printing or inkjet) using an electrically conductive ink, such as in particular an ink loaded with silver particles. A thermal and / or actinic treatment is then applied to evacuate a solvent contained in the ink and / or crosslink a polymer matrix of the ink. The substrate is then thermoformed to give it the desired three-dimensional appearance.In addition to the fact that the implementation of an electrically conductive ink is relatively expensive, the electrical performance of the conductive patterns obtained using such an ink remains improvable, in particular in terms of the level and homogeneity of electrical conductivity, which may in certain cases prove problematic for the proper functioning of an electronic device incorporating such a three-dimensional object.

[0008] STATEMENT OF THE INVENTION

[0009] The objects assigned to the invention therefore aim to provide a response to the aforementioned needs and problems, and to propose in particular a new process making it possible to manufacture, in a simple and efficient manner, three-dimensional articles with decorative and / or functional metallic pattern(s), in a wide variety of shapes and geometries.

[0010] Another object of the invention is to propose a new method which makes it possible to manufacture three-dimensional articles with metallic pattern(s) of all dimensions.

[0011] Another object of the invention is to propose a new method which makes it possible to manufacture three-dimensional articles with metallic pattern(s) quickly and relatively inexpensively.

[0012] Another object of the invention is to propose a new method for manufacturing three-dimensional articles with metallic pattern(s) which is simple to implement.

[0013] Another object of the invention aims to propose a new method for manufacturing three-dimensional articles with metallic pattern(s) which can be implemented industrially.

[0014] Another object of the invention is to propose a new method for manufacturing three-dimensional articles in which the metallic pattern(s) is (are) capable of being fine, precise and complex. Another object of the invention is to propose a new method for manufacturing three-dimensional articles in which the metallic pattern(s) is (are) particularly resistant to external aggression.

[0015] Another object of the invention aims to propose a new method for manufacturing three-dimensional articles whose metallic pattern(s) is (are) particularly homogeneous and regular, both in terms of thickness and in terms of surface appearance.

[0016] Another object of the invention aims to propose a new method for manufacturing three-dimensional articles with metallic pattern(s) which allows excellent control of the shape of the metallic pattern(s).

[0017] The objects assigned to the invention are achieved using a method of manufacturing a three-dimensional article comprising at least one metallic pattern, comprising at least:

[0018] - a step A of providing a flat substrate made of thermoformable material;

[0019] - a step B of forming on a surface of the flat substrate a temporary masking coating which adheres to said surface, to obtain a masked substrate having at least one unmasked area;

[0020] - a step C of thermoforming the flat substrate to give the latter a general three-dimensional shape;

[0021] - a step D of metallization of the substrate to form a metallic deposit on the latter;

[0022] - and a step E of removing said temporary masking coating.

[0023] SUMMARY DESCRIPTION OF THE DRAWINGS

[0024] Other features and advantages of the invention will appear and emerge in more detail on reading the description given below, with reference to the appended drawings, given solely as illustrative and non-limiting examples, among which:

[0025] - figure 1 illustrates, in the context of a first example of implementation of a method according to the invention for the manufacture of a three-dimensional RFID antenna, a flat substrate whose surface is covered with a temporary masking coating which adheres to said surface, thus forming a masked substrate having at least one unmasked zone, intended to receive a metal deposit;

[0026] - Figure 2 illustrates a thermoformed masked substrate, obtained after having subjected the masked flat substrate of Figure 1 to a thermoforming step in accordance with the invention;

[0027] - Figure 3 illustrates a thermoformed substrate whose surface is provided with a solid silver metal pattern forming an RFID antenna electrode, obtained after having in particular subjected the thermoformed masked substrate of Figure 2 to a metallization step and a step of removing the temporary masking coating in accordance with the invention;

[0028] - figure 4 illustrates, in the context of a second example of implementation of a method according to the invention for the manufacture of a three-dimensional article with decorative metallic patterns, a flat substrate whose surface is covered with a temporary masking coating which adheres to said surface, thus forming a masked substrate having at least one unmasked zone, intended to receive a metallic deposit;

[0029] - Figure 5 illustrates a metallized masked substrate, obtained after having subjected the masked flat substrate of Figure 4 to a metallization step and to a step of removing the temporary masking coating in accordance with the invention;

[0030] - Figure 6 illustrates a thermoformed metallized substrate whose surface is provided with a plurality of decorative metal patterns in solid silver, obtained after having subjected the masked metallized flat substrate of Figure 5 to a thermoforming step in accordance with the invention.

[0031] BEST WAY TO CARRY OUT THE INVENTION

[0032] The invention relates to a method for manufacturing a three-dimensional article comprising at least one metallic pattern (or "metallized pattern"). For the purposes of the invention, "three-dimensional" means a physical object which develops substantially in the three dimensions of space, following non-negligible distances from each other. The shape and dimensions of the metallic pattern(s) are not particularly limited, and may in particular depend on the intended application of the three-dimensional article and the metallic pattern(s) carried by the latter.Advantageously, the metallic pattern(s) concerned is / are decorative and / or functional, and thus form(s) or contribute(s) to forming, for example and in a non-limiting manner, one or more printed circuits, one or more integrated circuits on a semiconductor substrate, one or more sensor / detector electrodes, one or more electrodes of an electrical heating / defrosting device, one or more radiofrequency antennas (WiFi®, RFID, etc.), one or more coding pictograms capable of being read by electronic devices, one or more figurative and / or scriptural information identifying a product which incorporates or with which said three-dimensional article is associated, in particular a commercial product, such as a decorative visual or design on packaging, on an automotive product, etc.

[0033] The manufacturing method according to the invention comprises at least the following steps:

[0034] - a step A of providing a flat substrate made of thermoformable material;

[0035] - a step B of forming on a surface of the flat substrate (i.e. on a surface of at least one face of the latter) a temporary masking coating which adheres to said surface, to obtain a masked substrate having at least one unmasked area (“selective” temporary masking coating). Advantageously, said unmasked area is an area of ​​the surface of said face of the flat substrate bearing the temporary masking coating (and not, for example, an area of ​​a surface of a face of the flat substrate opposite the face bearing the temporary masking coating);

[0036] - a step C of thermoforming the flat substrate to give the latter a general three-dimensional shape;

[0037] - a step D of metallization of the substrate to form a metallic deposit on the latter, at least therefore on the unmasked area;

[0038] - a step E of removing said temporary masking coating. This preferably involves completely removing said temporary masking coating, the three-dimensional article obtained at the end of the manufacturing process thus advantageously being completely free of said temporary masking coating. Thanks to the method according to the invention, which thus cleverly proposes to form a temporary (selective) masking coating adhering to the surface of a flat substrate made of thermoformable material, prior to a step of thermoforming this flat substrate, for carrying out selective metallization of the substrate, it thus advantageously becomes possible to manufacture in a particularly simple and efficient manner three-dimensional articles with decorative and / or functional metallic pattern(s), in a wide variety of shapes and geometries.In particular, it thus advantageously becomes possible to manufacture in a particularly simple and efficient manner articles whose substrate, but also the decorative and / or functional metal pattern(s), have a three-dimensional, non-planar shape. Indeed, it proves in practice much easier to carry out temporary masking on a flat substrate than on a three-dimensional substrate, which is also of complex shape / geometry, and the use of such a temporary masking coating then makes it possible to easily and precisely metallize a wide variety of substrates made of thermoformable material, according to a plurality of conceivable metallization techniques.

[0039] The invention covers various embodiments, as will be understood from the following, which are based on the general principle of using a temporary (selective) masking coating formed on the flat substrate and adhering to the surface of the latter to delimit particular areas of the substrate which, at the end of the process, will carry one or more metallic pattern(s). In certain cases, the temporary masking coating may be intended to allow selective activation of the surface of the substrate, so that only at least one area of ​​the surface of the substrate not masked by the temporary masking coating will be activated and will be able, during the metallization step D, to receive a metallic deposit to form one or more metallic pattern(s).In other cases, in particular when it is not necessary to activate the surface of the substrate to allow subsequent metallization of the latter, the metallization step D may constitute a step of metallization of the masked substrate to form a metallic deposit on the latter at least on said unmasked area. At the end of step E of removing the temporary masking coating, only said unmasked area will bear a metallic deposit forming or intended to form the desired metallic pattern(s). The method may further optionally comprise in particular all or part of the following additional steps (and not necessarily in the following order):.

[0040] - at least one step F of preparing the surface of the substrate;

[0041] - a step G of defining a two-dimensional masking pattern, according to which the temporary masking coating is then formed on the surface of the flat substrate during step B, from a modeling of a deformation of the flat substrate during step C of thermoforming and a representation of the metallic pattern(s) to be obtained on the surface of the thermoformed substrate;

[0042] - a step H of activating the surface of the substrate, in particular the unmasked zone(s) intended to carry the metallic pattern(s);

[0043] - a step I of rinsing the surface of the metallized substrate;

[0044] - a step J of drying the surface of the metallized substrate;

[0045] - one or more step(s) K, L, M of finishing treatment of the surface of the metallized substrate, and / or more specifically of the metallic deposit or of the metallic pattern(s) formed on the latter;

[0046] - a step N of overmolding the thermoformed substrate;

[0047] - a step O of assembly of additional components.

[0048] For the purposes of the invention, the term "flat substrate" is advantageously understood to mean a substrate of substantially two-dimensional general shape, that is to say extending essentially in two of the three directions of space, and more negligibly in the third direction of space. Typically, such a flat substrate can thus take the form of a film, a sheet or a plate. The term "thermoformable material" is advantageously understood to mean a material which can be shaped, deformed, by heating, that is to say a material to which it is possible to give a particular shape after having brought it to a temperature (forming temperature) suitable for softening it, and which retains, after cooling and hardening, the shape which has thus been given to it.If the flat substrate does not already exist prior to the implementation of the method according to the invention, step A of providing the flat substrate (hereinafter abbreviated as “step A”) may then comprise the manufacture of such a flat substrate from a chosen thermoformable material. In general, and depending on the intended applications, the flat substrate may be made of non-conductive / dielectric thermoformable material, of semi-conductive thermoformable material or even of conductive thermoformable material (intrinsically or following a treatment that has made it conductive).

[0049] Step B of forming the temporary masking coating (or "temporary protective coating") (hereinafter abbreviated as "step B") aims, as introduced above, to delimit on the surface of the substrate, one or more particular zone(s) which, not having been masked by the temporary masking coating, will bear the desired metallic pattern(s) at the end of step D of metallization, step C of thermoforming and step E of removing the temporary masking coating. Conversely, the zone(s) of the substrate which were previously masked by the temporary masking coating will be devoid of metallic deposit, and therefore of metallic pattern(s), at the end of the steps of metallization, thermoforming and removal of the temporary masking coating.For the purposes of the invention, the temporary masking coating is a coating that adheres to the surface of the substrate, either directly to the bare surface of the latter, or possibly indirectly via an intermediate coating adhering to the surface of the substrate and to which the temporary masking coating adheres in return. In any event, the temporary masking coating is therefore not a mechanical mask / stencil (such as a screen printing mask for example) which would simply be affixed, plated, in contact with said surface. It is further understood that the temporary masking coating is not intended to form, or contribute to forming, said metal deposit and metal pattern(s).

[0050] Thermoforming step C (hereinafter abbreviated as "step C") generally consists of hot deforming the flat substrate, in an advantageously controlled manner, in order to give the latter a general three-dimensional shape, advantageously predefined. In particular, step C aims to deform the flat substrate at least locally and at least in a direction secant to a mean plane of extension of said flat substrate.

[0051] According to one variant (hereinafter, "variant V1"), thermoforming step C is carried out before metallization step D. According to a first sub-variant (hereinafter, "variant V1a") of this variant V1, thermoforming step C is also preferably carried out before step E of removing the temporary masking coating. In this case, step C is therefore a step of thermoforming the masked flat substrate, not yet metallized, during which the flat substrate and the temporary masking coating are simultaneously thermoformed (or thermodeformed), prior to carrying out step D of metallization of the masked substrate thus thermoformed. As such, the temporary masking coating is therefore itself advantageously thermoformable, or at least thermodeformable, so as to be able to undergo elongation and thus follow the deformation of the flat substrate, while adhering to the surface of the latter, during thermoforming step C.The temporary masking coating is thus advantageously designed, in particular in terms of elongation / deformation capacity without breaking, to be able to withstand the conditions for carrying out step C of thermoforming the flat substrate, without significant degradation of its function of masking the surface of the latter. Thus, if the shape and / or the surface area of ​​the unmasked zone(s) can be modified by step C of thermoforming, the temporary masking coating nonetheless remains substantially cohesive and film-forming, so in particular that no additional unmasked zone is involuntarily generated by the deformation of the temporary masking coating during step C of thermoforming. For the sake of simplicity, the expression “unmasked zone(s)” will refer indifferently in the following to one or more unmasked zone(s) of the masked substrate, whether the latter is thermoformed or not.

[0052] According to a second sub-variant (“variant V1b”) of this variant V1, step C is carried out after step E of removing the temporary masking coating, for example in the case where said temporary masking coating is intended to allow selective activation of the surface of the substrate during an activation step H prior to metallization step D. In this case, step C is therefore a step of thermoforming the flat substrate, devoid of said temporary masking coating and not yet metallized, prior to carrying out step D of metallization of the substrate thus thermoformed.

[0053] To the extent that, according to this variant V1, the metal deposit is thus formed on the surface of the substrate after the latter has been thermoformed, the metal deposit therefore does not undergo the mechanical deformation and heating to which the flat substrate is subjected during the thermoforming step C. It is thus advantageously possible to manufacture a three-dimensional article of particularly marked and / or complex shapes and geometries, therefore involving significant deformation of the flat substrate during thermoforming, without the risk of step C leading to degradation (delamination, (micro)-cracking, etc.) of the quality of the metal deposit, and in particular of its properties in terms of electrical conductivity. In particular, it becomes advantageously possible to subject the flat substrate to a deformation rate greater than or equal to 200% during the thermoforming step C.Such a variant V1 proves to be particularly advantageous in the case in particular where it is desired to obtain a three-dimensional article comprising one or more metal patterns for functional purposes, such as forming in particular one or more conductive metal tracks of a printed circuit, one or more sensor / detector electrodes or even one or more radiofrequency antennas.

[0054] According to another variant (hereinafter, "variant V2"), thermoforming step C is carried out after metallization step D. According to this variant V2, step C is therefore a step of thermoforming the metallized flat substrate, during which the flat substrate and the metal deposit formed on its surface therefore simultaneously undergo deformation. Although it is possibly conceivable ("variant V2a") for the temporary masking coating to be present on the surface of the flat substrate during thermoforming step C, this is not strictly necessary. On the contrary, it is even advantageous that, in this variant V2, step E of removing the temporary masking coating is carried out before thermoforming step C ("variant V2b"), so as to prevent deformation of the temporary masking coating from possibly damaging the metal deposit.

[0055] According to this variant V2, step B of forming the temporary masking coating and step D of metallization are thus both carried out on the flat substrate. The implementation of these steps B and D is thus simplified, said steps B and D being able to be easily carried out in line in an industrial context. That being said, it is preferable to reserve this variant V2 for the manufacture of three-dimensional articles requiring limited deformation of the metallized substrate during step C of thermoforming, in order to limit the risk of degradation of the quality of the metal deposit during thermoforming which could lead to a breakage or inhomogeneity of the conductive properties of the metallic pattern(s), and / or for the manufacture of three-dimensional articles whose metallic pattern(s) is (are) essentially decorative.

[0056] Carried out after step B, metallization step D (hereinafter abbreviated as “step D”) consists of forming on the surface of the substrate, and at least on the area(s) not masked by the temporary masking coating or on one or more areas of the substrate corresponding to the area(s) not masked by the temporary masking coating, a metal deposit intended to form all or part (i.e. alone or possibly in combination with a complementary metal deposit for example) of the desired metal pattern(s). By “metal deposit” is meant here generally a deposit, a layer, comprising - or formed from - at least one metal or metallic substance, therefore including at least one elementary metal (or “elementary simple body”), at least one mixture of elementary metals, at least one metal alloy and / or at least one metal oxide.

[0057] Advantageously, metallization step D is carried out in such a way that the metal deposit obtained at the end of the latter comprises at least one metal (or “metallic substance”) chosen from the group comprising: an elementary metal such as silver Ag, gold Au, nickel Ni, copper Cu, iron Fe, tin Sn, cobalt Co, an alloy of the latter, a mixture of two or more of these elementary metals, or one or more oxides of at least one of these elementary metals.

[0058] Advantageously, in particular with regard to electrical conductivity properties and / or with regard to decorative properties (e.g., “mirror” effect) of the metal pattern(s), the metallization step D is carried out in such a way that the metal deposit is made of solid metal, possibly loaded with additional particles (or “fillers”) which may be organic or inorganic. In this case, the metal deposit is therefore essentially—if not totally, with the inevitable exception of non-metallic impurities—formed of metal (or “metallic substance”), as defined above. The term “metallic deposit made of solid metal” therefore advantageously means, in particular, that the metal deposit is advantageously free of polymer matrix.This makes it possible in particular to obtain a metallic pattern whose properties remain particularly stable over time, unlike a pattern which would comprise a polymer matrix in which metallic particles would be dispersed, which polymer matrix would then be liable to degrade progressively under the effect, for example, of light, heat, etc., thus leading to a drift over time of the properties of the metallic pattern. Advantageously, the solid metal may consist of a single pure elemental metal (typically more than 90%, preferably more than 95%, and more preferably more than 98%). For example, the metallic deposit may thus be formed of a pure elemental metal, for example pure silver Ag (preferably more than 95%, and more preferably more than 98%), and possibly additional particles.Where appropriate, said solid metal forms a solid (metallic) matrix within which said additional particles are dispersed. Said additional particles are preferably chosen with a characteristic size of less than 100 pm. In general, the use of such additional particles aims to modify the physical properties (e.g. mechanical / tribological, electrical and / or optical) and / or the intrinsic chemical properties of the solid metal which is loaded with them.As non-limiting examples of additional particles that may be included, alone or as a mixture, in a solid metal metal deposit, mention may be made of: diamond carbon particles, silicon carbide SiC particles, molybdenum disulfide M0S2 particles, particles of one or more rare earths or rare earth oxide(s), graphene particles, particles of a fluoropolymer (such as polytetrafluoroethylene (PTFE), for example), particles of elemental metal or metal oxide(s), etc.

[0059] The metal deposit may be single-layer or multi-layer, depending on the desired properties and the intended applications of the metal pattern(s). Advantageously, step D is carried out in such a way that the metal deposit has, at the end of said metallization step D, a thickness of between 10 nm and 5 μm, preferably between 10 nm and 1 μm, and more preferably between 10 nm and 500 nm. According to a variant, step D is carried out in such a way that the thickness of the metal deposit obtained at the end of step D is substantially constant over the entire extent of said metal deposit, i.e. the thickness is substantially identical at every point of the metal deposit. It is thus possible to obtain one or more metal pattern(s) which have a thickness that is substantially constant over the entire extent of the metal pattern(s).According to another variant, step D is carried out in such a way that the thickness of the metal deposit obtained at the end of step D is variable depending on the extent of said metal deposit (while preferably remaining within the aforementioned ranges of values), that is to say that the metal deposit has at least a first zone and a second zone, distinct, the thickness of the metal deposit being increasing or on the contrary decreasing (thickness gradient) from said first zone towards said second zone. Such a variation in the thickness of the metal deposit thus advantageously makes it possible to obtain one or more metal pattern(s) which define zones of different electrical conductivity or resistivity, or even of different transparency or reflectivity to electromagnetic waves (for example to visible, IR or UV light, to radiofrequency waves, etc.), which may be of particular interest depending on the functional and / or decorative applications targeted.

[0060] Different metallization methods, and in particular different methods called "wet" or "dry", can be considered for carrying out metallization step D. Among the main methods called "dry" that can be considered here, we can cite physical vapor deposition (PVD) techniques and chemical vapor deposition (PVD) techniques. However, these techniques have the major drawback of needing to place the substrate under vacuum to carry out the metallization.It is therefore preferable for metallization step D to implement one or more so-called "wet" metallization methods, electrolytic or chemical (non-electrolytic), using one or more suitable metallization solutions, which are generally easier and less expensive to implement, particularly in an industrial manufacturing context.

[0061] Thus, according to an advantageous variant, the metallization step D is carried out by non-electrolytic (chemical) deposition from one or more metallization solutions (or “oxidation-reduction solution(s)”), advantageously containing at least one metal in the form of a metal cation (i.e. metal in cationic form, forming an oxidant) and at least one reducing agent capable of transforming the metal cation into metal. Said at least one metal cation can advantageously be obtained by dissolution in the liquid phase of at least one corresponding metal salt. According to a first embodiment of this non-electrolytic variant, the aforementioned non-electrolytic deposition (or “metallization”) is more specifically carried out by projection of the metallization solution(s) in the form of one or more aerosol(s).In this case, the method according to the invention optionally comprises, before said metallization step D, at least one of the following additional steps:

[0062] - a step P of treatment to increase the surface energy of the substrate, knowing that in the case where the method comprises an activation step H, such a step P of treatment to increase the surface energy of the substrate may optionally be provided before said activation step H;

[0063] - a step Q of wetting the surface of the substrate;

[0064] - a step R of rinsing the surface of the substrate.

[0065] Step P of treatment to increase the surface energy of the substrate may possibly be comparable to a step F of preparation of the surface of the substrate.

[0066] This embodiment by projection of aerosol(s) is particularly interesting in that, in addition to the excellent properties of the metal deposit which can be formed in this way, it allows simple and rapid metallization of substrates of all dimensions, and in particular large substrates. Furthermore, it is particularly well suited to the case where the metallization step D is carried out after the thermoforming step C, and where the surface to be metallized is therefore not flat but on the contrary deformed. Furthermore, this embodiment makes it possible to obtain in a particularly simple manner a metal deposit whose thickness is variable according to the extent of said metal deposit, as envisaged in the above.Furthermore, this embodiment by projection of aerosol(s) advantageously makes it possible to form in a simple and efficient manner a metallic deposit in solid, dense metal (and therefore substantially devoid of porosity, unlike a porous metallic deposit which would be formed from an aggregate of metallic particles), which proves to be particularly interesting, in particular when seeking to obtain a metallic pattern having excellent electrical properties.

[0067] According to a second embodiment of this non-electrolytic variant, the aforementioned non-electrolytic deposition is an autocatalytic (or "electroless") chemical deposition (or "metallization") carried out by immersing the substrate in one or more metallization solutions, optionally comprising, in addition to one or more metal cations and one or more reducing agents, one or more complexing agents, one or more stabilizing agents, and other possible additives (surfactants, etc.). In this case, the method then advantageously comprises a step H of activating the surface of the substrate prior to the metallization step D, and optionally, before said activation step H, at least one of the following steps, preferably in the following order:

[0068] - satin finishing step S, preferably implemented between step B of forming the temporary masking coating and step H of activation;

[0069] - step T of rinsing the surface of the substrate, in the event of implementation of such a satin finishing step S.

[0070] According to another wet variant, the metallization step D can optionally be carried out by electrolytic deposition (or "electrodesposition" or "galvanostegy"). Such electrolytic deposition (or "metallization") is based on an oxidation-reduction reaction using an electric current, starting from a metallization solution typically containing at least one metal in cationic form in an aqueous medium. An electric current is imposed between the substrate that is to be metallized and a counter-electrode. The metal cation is then reduced on the surface of the substrate to form a metal deposit.However, such an electrolytic deposition metallization method is less preferable than the two previous ones since it is only possible in the case where the thermoformable material of the substrate is (electro)conductive, which therefore strongly limits the choice of thermoformable material, in particular excluding most thermoformable polymer materials.

[0071] Optionally, metallization step D may be carried out on the one hand according to the first embodiment of the non-electrolytic metallization variant (e.g. by spraying aerosol(s)) mentioned above and optionally, on the other hand, according to the second embodiment of the non-electrolytic metallization variant (e.g. by immersion) mentioned above and / or according to the electrolytic deposition variant mentioned above. As is apparent from the above, step E of removing the temporary masking coating (hereinafter abbreviated as “step E”) aims to remove the temporary masking coating present on the surface of the substrate.

[0072] As such, step E can be performed:

[0073] - either before the metallization step D, in the case in particular where the method comprises a step H of activating the surface of the substrate prior to the metallization step D and where the temporary masking coating is intended to allow selective activation of the surface of the substrate;

[0074] - either after step D of metallization;

[0075] - either, more preferably, during metallization step D, or partly during metallization step D and partly after metallization step D, or partly before metallization step D, partly during metallization step D and partly after metallization step D.

[0076] Carrying out step E at least partially concomitantly with carrying out step D of metallization, as preferentially proposed above, advantageously contributes to accelerating and simplifying the implementation of the method according to the invention, by limiting the number of successive steps necessary.

[0077] Advantageously, step E of removing the temporary masking coating is carried out at least partially by chemical, non-mechanical means, in order to remove said temporary masking coating in a simple and clean manner from the surface of the substrate, in particular in the case where said step E is carried out after step C of thermoforming, while limiting the risk of degrading the fineness and precision of the metallic pattern(s) that it is sought to obtain.

[0078] In this respect, step E of removing the temporary masking coating advantageously comprises at least one operation of dissolving (at least partially) the temporary masking coating by at least one solvent used in the method. Optionally, step E may even advantageously consist essentially of dissolving (at least partially) the temporary masking coating by at least one solvent used in the method. Here, the term "dissolving by at least one solvent" means a disintegration, a disintegration, a loss of cohesion, total or partial, of the temporary masking coating, under the action of a particular fluid (a liquid, preferably) chosen for its specific chemically aggressive character with respect to the temporary masking coating, such as to allow its disintegration, its separation, and its removal from the surface of the substrate.It may thus be a dissolution mechanism in a solvent in the strict chemical sense, but not necessarily. Preferably, said temporary masking coating is alkali-soluble (or at least alkali-sensitive) so that it can be preferentially dissolved by an alkaline solvent used in the process.

[0079] Step E may optionally comprise, prior to said operation of dissolving the temporary masking coating, an operation of exposure under actinic radiation (for example, under UV light) and / or an operation of heat treatment of the temporary masking coating, in order to weaken the temporary masking coating and / or to facilitate its subsequent dissolution. Step E may optionally comprise, after such a dissolution operation, a liquid phase entrainment operation and / or a mechanical entrainment operation by a gas (preferably air), in particular in order to facilitate the evacuation of the dissolved temporary masking coating and / or any debris not completely dissolved therefrom.

[0080] In the case mentioned above where step E is carried out during metallization step D, or partly during metallization step D and partly after metallization step D, or partly before metallization step D, partly during metallization step D and partly after metallization step D, said solvent allowing the removal by dissolution of the temporary masking coating is preferably at least contained in the (or one of the) metallization solution(s) used during step D. It is therefore an operation of dissolving the temporary masking coating by at least one solvent used during step D. The duration of formation of the metal deposit during said metallization step D is then preferably chosen to be less than or equal to the duration necessary for the dissolution of the temporary masking coating under the action of said solvent.Additionally or alternatively, the method may comprise a step I of rinsing the surface of the metallized substrate and the solvent allowing the removal by dissolution of the temporary masking coating may be contained in a rinsing liquid used in said step I.

[0081] However, it remains possible, although less preferential, that step E can be carried out by a non-chemical means, for example by laser ablation, using a jet of pressurized gas, or by any suitable known mechanical means.

[0082] This being stated, certain aspects of the above steps will be described in more detail below.

[0083] - Step A of supplying a flat substrate made of thermoformable material -

[0084] Although it is possible to consider the use of a flat substrate made of glass (mineral) or metal, it is preferable for the flat substrate to be made of a thermoformable polymer material (thermoplastic material), whether filled or not, or of a thermoformable composite material with a polymer matrix. In particular, thermoformable polymer or polymer matrix materials are generally easier to use, due to a softening temperature much lower than that of glass or most metals.Among the thermoformable polymer materials that may be considered, non-limiting examples may be mentioned polystyrene (PS), high-impact polystyrene (SB / HIPS), polyethylene (PE), polypropylene (PP), polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS), polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), or thermoplastic polyesters, such as, for example, polylactic acid (PLA), polyethylene terephthalate (PET) and polyethylene terephthalate glycol (PETG). In the case where the flat substrate is a composite thermoformable material with a polymer matrix, the polymer(s) of the polymer matrix may be chosen, for example, from the thermoformable polymer materials listed above.

[0085] More generally, the thermoformable material of the flat substrate may be a single material or, on the contrary, a composite material. The flat substrate may be single-layer or possibly multi-layer. Advantageously, said flat substrate may be a film, a sheet or a plate of a thermoformable polymer material or of a composite thermoformable material with a polymer matrix, with a thickness of between 8 μm and 15 mm, and more preferably between 25 μm and 10 mm, which facilitates handling and subsequent thermoforming.

[0086] Depending on the material and thickness chosen, the flat substrate may be substantially rigid, or on the contrary flexible. However, it is preferable in practice, in particular to facilitate industrial implementation of the process, for the flat substrate to be flexible, i.e. it can advantageously be curved, folded, by human force alone without breaking, deforming, or irreversibly degrading. The flat substrate may thus, for example, advantageously be supplied continuously from a coil of wound substrate, then be wound back into a coil at the end of step B of forming the temporary masking coating or at the end of step D of metallization, in the case (variant V2) where the latter is carried out before step C of thermoforming (so-called "roll-to-roll" / "R2R" process in English).In contrast, a "rigid substrate" means a substrate that cannot be bent or folded by human force alone without breaking or degrading irreversibly.

[0087] - Step F of preparation of the substrate surface -

[0088] As introduced previously, the method may comprise one (or more) step(s) F of preparing the surface of the substrate, which aim(s) to modify certain properties of the surface of the substrate with a view to carrying out one (or more) subsequent step(s) of the method. This may be one (or more) step(s) of preparing the surface of the flat substrate, therefore carried out before the thermoforming step D, and / or one (or more) step(s) of preparing the surface of the thermoformed substrate, therefore carried out after the thermoforming step C.

[0089] Furthermore, such a step F may be carried out before or after step B of forming the temporary masking coating. In some cases, preparing the surface of the flat substrate before forming the temporary masking coating makes it possible to avoid subjecting the temporary masking coating to physicochemical modifications, which could result in excessive adhesion of the latter to the surface of the flat substrate, which could make subsequent removal of the temporary masking coating more difficult. In other cases, the preparation of the surface of the flat substrate may be carried out after forming the temporary masking coating, so as, on the contrary, to strengthen the cohesion, the adhesion, of the temporary masking coating and, possibly, to slow down the removal of the latter.

[0090] Step F may comprise an operation of cleaning and / or degreasing the surface of the substrate, using any products known per se and suitable. In addition to or instead of such a cleaning / degreasing operation, step F may comprise an operation of depositing on the surface of the substrate a varnish, possibly colored / pigmented, for example a UV-crosslinking varnish applied by spraying, by any known and suitable means such as a compressed air paint gun (for example, a High Volume Low Pressure (HVLP) spray gun).

[0091] Optionally, step F may comprise at least, or correspond to, a treatment for increasing the energy of the surface of the substrate (step P).

[0092] - Step B of forming the temporary masking coating -

[0093] The practical arrangements for carrying out step B may in particular depend on the nature of the thermoformable material of the flat substrate, the precision sought for the definition of the unmasked zone(s), as well as possibly, in the case in particular of sub-variant V1 mentioned above, the conditions of step C of thermoforming (in terms in particular of temperature and deformation rate) to which it is subsequently desired to subject the flat substrate and the temporary masking coating during step C of thermoforming.

[0094] Said step B of forming the temporary masking coating is preferably carried out by selective deposition of a layer of a liquid or pasty masking composition on the surface of the flat substrate, by any known and suitable application technique, and for example by screen printing, pad printing, flexography, gravure printing and / or direct printing (for example, drop-by-drop or “inkjet”),

[0095] - possibly followed by drying and / or hardening of the layer of masking composition thus deposited.

[0096] Depending on the formulation of the masking composition chosen, the drying and / or curing thereof may include drying / desolvation, possibly under the effect of a thermal input, or polymerization / crosslinking of the deposited masking composition under the effect of a thermal input and / or under the action of actinic radiation (for example, by exposure to ultraviolet (UV) light). Such drying and / or curing of the deposited layer of masking composition proves to be particularly advantageous depending on the fluidity of the masking composition, in order to avoid uncontrolled spreading of the masking composition which would impair the definition of the shape of the unmasked area(s).

[0097] Alternatively, although in a more complex and therefore less preferential manner, step B can be carried out by

[0098] - (non-selective) deposition of said liquid or pasty masking composition on the surface of the flat substrate, for example by dipping, by spraying, or any other known and suitable non-selective deposition technique,

[0099] - possibly followed by drying and / or hardening of the layer of masking composition thus deposited,

[0100] - followed by selective ablation of the temporary masking coating formed to locally create one (or more) unmasked area(s) on the surface of the flat substrate.

[0101] Optionally, said masking composition is deposited on the surface of the flat substrate during step B according to a two-dimensional masking pattern previously defined during a step G as described below.

[0102] The masking composition may be chosen to be substantially colorless, or on the contrary colored / pigmented. A masking composition containing a dye / pigment makes it possible, where appropriate, to more easily visualize the temporary protective coating formed on the surface of the flat substrate, which may prove practical in certain cases.

[0103] Preferably, step B is carried out in such a way that the temporary masking coating has, at the end of step B of forming the latter (and therefore, where appropriate, after drying and / or hardening of the deposited masking composition layer), a thickness of between 100 nm and 50 μm, preferably between 500 nm and 20 μm, and more preferably between 1 μm and 10 μm. Such a thickness makes it possible to obtain a sufficient barrier effect on the surface of the areas of the substrate which are not intended to subsequently carry the metal pattern(s). What is more, such a thickness advantageously contributes to the ability of the temporary masking coating to undergo thermoforming step C without significant damage, where appropriate (variant V1 a).According to one variant, step B is carried out in such a way that, at the end of step B, the thickness of the temporary masking coating is substantially constant over the entire extent of the temporary masking coating, i.e. the thickness of the latter is substantially identical at every point of said temporary masking coating. According to another variant, step B is carried out in such a way that, at the end of step B, the thickness of the temporary masking coating is variable over the extent of the latter (while preferably remaining within the aforementioned ranges of values), i.e. the temporary masking coating has at least a first portion and a second portion, which are distinct, the thickness of the first portion being different from the thickness of the second portion.Such a difference in thickness of the temporary masking coating, preferably in the ranges of values ​​indicated above, may prove interesting in particular in the case of variant V1, to locally adapt the thickness of the temporary masking coating to the amplitude of the deformation to which it is desired to subject a given area of ​​the (masked) substrate during thermoforming step C.

[0104] It should be noted that, since step B of forming the temporary masking coating is carried out on the (flat) substrate before step C of thermoforming, the temporary masking coating therefore does not form at the end of step B, or at least not necessarily, an exact negative of the metal pattern(s) that it is sought to ultimately obtain on the surface of the thermoformed substrate. Indeed, according to sub-variant V1 described above, the temporary masking coating itself undergoes deformation during step C, so that it is the deformed temporary masking coating, obtained at the end of step C, which then advantageously corresponds to the negative of the metal pattern(s) to be obtained. According to variant V2, the temporary masking coating may or may not be present on the surface of the substrate when carrying out step C of thermoforming.In the preferred case where step E of removing the temporary masking coating is carried out before step C, the surface of the flat substrate is therefore provided with one (or more) “raw” metal pattern(s) which will undergo deformation during step C of thermoforming to lead to obtaining the desired metal pattern(s). Thus, the temporary masking coating corresponds in this case to the negative of said “raw” metal pattern(s).

[0105] As mentioned previously, in the case of sub-variant V1 a of variant V1 , the temporary masking coating is advantageously thermoformable and designed, in particular in terms of elongation / deformation capacities without breaking and temperature resistance, to be able to withstand the conditions for carrying out step C of thermoforming the flat substrate, without significant degradation of its function of masking the surface of the latter. Typically, the temporary masking coating is advantageously designed so that it has, in particular at the forming temperature chosen for step C of thermoforming, a rate of elongation / deformation without breaking at least equal to the rate of deformation that it is desired to impart to the flat substrate during the thermoforming step.

[0106] Such a particular design may typically involve an appropriate choice in terms of formulation of the masking composition, it being understood that the exact formulation of the masking composition may depend in practice on a certain number of factors such as in particular the method of application of the masking composition to the substrate, the nature of the thermoformable material of the substrate, the forming temperature at which thermoforming step C is carried out, the thickness of the temporary masking coating to be formed, the rate of deformation that it is desired to impart to the flat substrate and to the temporary masking coating during thermoforming step C, etc.For example, such an ability of the temporary masking coating to withstand the conditions for carrying out step C of thermoforming the flat substrate can be given to it by a choice, in the formulation of the masking composition, of a particular polymeric organic binder capable of forming an organic polymer matrix having the desired elongation / deformation without breakage and temperature resistance capacities.

[0107] The preferentially dissolvable (or sensitive) nature of the temporary masking coating to a solvent used in the method, and more preferentially at least to one solvent contained in the or one of the metallization solutions used in step D, can be conferred on the temporary masking coating by a choice in terms of formulation of the masking composition, and for example by choosing a component, such as in particular a polymeric organic binder intended to form a polymeric organic matrix, which is dissolvable by the solvent in question, or at least sensitive to the latter.

[0108] For example, the masking composition implemented during step B may comprise all or part of the following components (it being understood that the content of the masking composition in each of these components may depend in particular on the chosen method of application of said masking composition, as well as its possible method of drying / hardening):

[0109] - a carrier component, which may represent between 20% and 70% of the total weight of the masking composition. The carrier component may comprise an organic or aqueous solvent, a monomer, an oligomer or a mixture of these compounds. It has the particularity of solubilizing or suspending the rest of the components described below. The carrier component contributes to the viscosity and rheological properties of the masking composition, thus facilitating its application. It is intended to be evaporated in the case of a thermally drying masking composition and / or to be crosslinked in the case of a masking composition crosslinking under UV, for example;

[0110] - a binder component, which may represent 30% to 70% of the total weight of the masking composition. It is advantageously intended to form an organic polymer matrix which may be of the acrylic, polyester, vinyl, styrene, or polyamide type in the case of a thermally drying masking composition. In the case of a masking composition crosslinked under UV exposure, the binder component may be a mixture of monomers and oligomers of the acrylate, cationic, or anionic type, as well as the polymers mentioned above. The binder component may optionally also act as a carrier.The binder component provides the temporary masking coating with its main properties, including in particular its adhesion to the substrate, its resistance to friction, its possible sensitivity to a solvent used in the process (for example, alkali sensitivity) and its possible capacity to withstand thermoforming step C and to thermodeform without breaking during the latter;

[0111] - a solid, organic or inorganic component, which may represent between 1% and 50% of the total weight of the masking composition. It may correspond to a mineral or organic filler, possibly fibrous. It may confer, or contribute to conferring, on the masking composition and / or the temporary masking coating a color, particular rheological properties and resistance to friction;

[0112] - one or more additives), which may represent between 0.01% and 10% of the total weight of the formula. These may be one or more rheology additives, wetting agents, antifoams, dispersants, surfactants, stabilizers or colorants. These additives make it possible, among other things, to rectify the rheology, the applicability, the wettability of the masking composition on the substrate, to accelerate or decelerate the drying or hardening of the masking composition, to better disperse and stabilize the solid component, to color the masking composition, or even to improve certain properties of the temporary masking coating such as, for example, its resistance or its gloss;

[0113] - optionally, one or more photoinitiators, which may represent between 5% and 15% of the total weight of the masking composition. In the case of a masking composition curable under UV exposure, they allow the crosslinking of monomers and oligomers. They may be of a radical, cationic or anionic nature.

[0114] As non-limiting examples of carrier components, mention may be made of: water, butanol, methoxypropanol, ethyl acetate, butyl acetate, cyclohexane, 2-butoxyethanol acetate, 2-methoxy-1-methylethyl acetate, propylene carbonate, isopropyl myristate, diethylene glycol monoethyl ether acetate, glycerol, hexane, methylcyclohexane, or, among the monomers: PETIA, HDDA, IBOA, TMPTA, TPGDA, HEMA, etc. Non-limiting examples of binder components include: vinyl acetate and vinyl chloride copolymer, acrylic resin, polyvinyl alcohol, polyvinylpyrrolidone, polyurethane, aliphatic urethane acrylate, polyester acrylate, polyester, etc. Non-limiting examples of solid components include: silica, barium carbonate, barium sulfate, aluminum hydroxide, wax, etc.

[0115] - Step G of defining a two-dimensional masking pattern -

[0116] It may prove important, particularly in the case where said at least one metal pattern is intended to play a functional role, and in particular for (radio-)electric or electronic applications, to ensure perfect control of the shape of the metal pattern obtained on the surface of the thermoformed substrate. In this respect, the method according to the invention may advantageously comprise, before step B, a step G of defining a two-dimensional masking pattern, according to which the temporary masking coating is then formed on the surface of the flat substrate during said step B of forming the temporary masking coating, from a modeling of a deformation of the flat substrate, and where appropriate of the temporary masking coating, during step C of thermoforming and a representation (or modeling) of said at least one metal pattern to be obtained.In other words, a two-dimensional masking pattern is defined by "inverse anamorphosis", so that this two-dimensional masking pattern, according to which the temporary masking coating is formed on the surface of the flat substrate during step B, makes it possible to obtain the desired metallic pattern(s) by anticipating and compensating for the effects of the deformation caused by the thermoforming step C. The step of defining such a two-dimensional masking pattern can be carried out using commercially available computer software, such as, for example, the T-SIM® software from SIMCON (formerly CADFLOW), the PAM-FORM™ software from ESI GROUP, the ANAMAP™ software solution from KALLISTO or the Thermo 3D™ software from QUADRAXIS. - Step H of activating the surface of the substrate -.

[0117] Depending on the nature of the substrate, the nature of the metal deposit to be formed, and depending on the metallization method(s) used to carry out metallization step D, a prior step of activating the surface of the substrate may prove necessary to allow, or at least to facilitate, the formation of the metal deposit on the surface of the substrate.

[0118] In the case where metallization step D is carried out by non-electrolytic deposition by projection of one (or more) metallization solution(s) in the form of aerosol(s), such an activation step H (or at least “sensitization”) may be necessary for the deposition of certain metals. It aims in particular to accelerate the oxidation-reduction reaction occurring in step D. During step H, the surface of the substrate is brought into contact with at least one sensitizing chemical species, which is absorbed onto the surface of the substrate and which will then accelerate the metallization reaction.

[0119] Preferably, the activation step H is carried out after the step B of forming the temporary masking coating and before the step E of removing the latter, so that the sensitizing chemical species(s) are therefore adsorbed both on the temporary masking coating and on the unmasked area(s), i.e. not covered by the latter.

[0120] In practice, step H is preferably carried out by spraying at least one sensitizing solution onto the surface of the substrate, by any known and appropriate means, such as, for example, using a compressed air paint gun (for example, a High Volume Low Pressure (HVLP) spray gun). Alternatively, step H could be carried out by immersing the substrate in at least one sensitizing solution.

[0121] For example, a first sensitizing solution based on stannous chloride (SnCl2) or SnSCU / ^SCU / quinol / alcohol is applied by spraying or immersion. A palladium or silver solution capable of reacting with Sn ions is then deposited in the same way. 2+to form nucleation centers on the surface of the substrate, or even a colloidal PdSn solution formed ex situ. For more details, one can refer for example to "Metal Finishing Guidebook and Directory Issue", 1996 Metal Finishing publication, pages 354, 356 and 357. H. Narcus, to ". Metallizing of Plastics", Reinhold Publishing Corporation, 1960, Chapter 2, page 21. F. Lowenheim, or even to "Modern electroplating", John Wiley & Sons publication, 1974 Chapter 28, page 636. Advantageously, the sensitization of the surface of the substrate is implemented by means of a sensitization solution based on stannous chloride, for example in accordance with the method of implementation described in document FR-2 763 962 B1. In this case, a rinsing step using a rinsing liquid as described below is carried out immediately after sensitization, without an intermediate step.According to one variant, the activation of the surface of the substrate is carried out by means of a sensitization solution, in particular palladium chloride, for example in accordance with the method of implementation described in document FR-2 763 962 B1. In this case, a rinsing step using a rinsing liquid as described in the examples below is carried out immediately after the activation step H, without an intermediate step.

[0122] In the case where metallization step D is carried out by autocatalytic chemical deposition (“electroless”) by immersion in one or more metallization solutions, such an activation step H, which advantageously aims to accelerate the catalytic redox reaction occurring in step D, is generally essential. It consists of depositing on the surface of the masked substrate, a currentless chemical metallization catalyst, for example a Sn / Pd type catalyst.

[0123] Preferably, the activation step H is carried out after the step B of forming the temporary masking coating and before the step E of removing the latter, so that the catalyst is adsorbed both on the temporary masking coating and on the unmasked area(s), i.e. not covered by the latter.

[0124] Step H is preferably preceded by a satin finishing step S followed by a rinsing step T. Step S corresponds to a treatment for increasing the surface energy of the substrate and / or increasing the roughness of the substrate, which may be of the type defined below for step P. In the case of an autocatalytic chemical deposition, the satin finishing is preferably carried out by physical treatment (corona discharge, plasma treatment, etc.) or chemical treatment (for example, a sulfochromic or other treatment) in order to provide sufficient adhesion to the metal deposit to be formed. The rinsing step T advantageously corresponds to rinsing of the type defined below for step R.

[0125] - Step C of thermoforming the flat substrate -

[0126] Step C of thermoforming the flat substrate can advantageously be carried out by any known thermoforming means and technique, obviously adapted to the characteristics of the substrate (nature of the thermoformable material, thickness of the flat substrate, etc.) and, where appropriate, to the intrinsic characteristics of the temporary masking coating and / or to the intrinsic characteristics of the metal deposit or of the metal pattern(s) possibly present on the surface of the flat substrate to be thermoformed.

[0127] Typically, step C is carried out by heating the flat substrate in an advantageously homogeneous manner, by conduction and / or by convection and / or by radiation, until the thermoformable material of the flat substrate is brought to a forming temperature sufficient to make the flat substrate malleable. The forming temperature in question can obviously vary depending on the thermoformable material chosen. For a thermoformable polymer material, the forming temperature is typically chosen to be at least equal to a glass transition temperature of the material in question, and therefore advantageously lower than the melting temperature of the material in question. Once made malleable, the flat substrate is pressed against a male (“positive” mold) or female (“negative” mold) mold (or counterform), advantageously with vacuum suction and / or pressure, so that the flat substrate deforms and takes the shape of the mold.The deformed substrate is then cooled so that the thermoformable material hardens and retains the shape imparted by the mold, then the deformed substrate is removed from the mold. - Metallization Step D -.

[0128] As introduced previously, metallization step D can be carried out after thermoforming step C (variant V1) or on the contrary before thermoforming step C (variant V2).

[0129] — Non-electrolytic deposition by projection in the form of aerosol(s)

[0130] The steps P of treatment for increasing the surface energy of the substrate, step Q of wetting the surface of the substrate and step R of rinsing the surface of the substrate, which may optionally precede the activation step H or the metallization step D are described below, as a preamble to a description of the metallization step D according to the embodiment envisaged above in which the metallization is carried out by non-electrolytic (chemical) deposition by projection of one (or more) metallization solution(s) in the form of aerosol(s). In the case where step D is carried out after the thermoforming step C (variant V1), said steps P, Q and R are preferably carried out after said step C.

[0131] Step P of treatment to increase the surface energy of the substrate can be carried out:

[0132] - by physical treatment, preferably chosen from the following physical treatments: flaming, plasma treatment, corona treatment, increased roughness (by sandblasting, shot blasting, etc.) and combinations thereof, and / or

[0133] - by chemical treatment, preferably chosen from the following chemical treatments: application of a silane-based solution, depassivation of the surface using one or more acid solutions, polishing using rare earth oxide, fluorination, acid or alkaline chemical attack to create micro-roughness and combinations thereof.

[0134] More preferably, the physical treatment is a treatment by flaming and / or by plasma, in particular in the case where the substrate, flexible or rigid, is made of a thermoformable polymer material or a thermoformable composite material with a polymer matrix. The flaming consists, for example, of passing the substrate to be metallized under a flame whose temperature is, for example, between 1,200°C and 1,700°C. The duration of the flaming is generally 4 to 50 seconds. The flame is preferably obtained by combustion of a fuel, such as propane for example, in the presence of an oxidant such as oxygen. The treatment (by) plasma corresponds, for example, to passing the substrate to be metallized through a plasma torch, for example those marketed by ACXYS® or PLASMATREAT®.More preferably, the chemical treatment is a fluorination treatment, in the case where the substrate, flexible or rigid, is made of a thermoformable polymer material or a thermoformable composite material with a polymer matrix. Fluorination corresponds, for example, to bringing into contact, in a reduced pressure enclosure, the substrate to be metallized and a gaseous solution based on inert gas (argon) containing a fluorine additive. Such fluorination can be carried out, for example, with equipment of the type marketed by the company AIR LIQUIDE®.

[0135] In any event, these physical and / or chemical treatments for increasing the surface energy of the substrate must advantageously be carried out so that the surface energy of the substrate is, at the end of step P, greater than or equal to 50 or 55 dynes, preferably greater than or equal to 60 or 65 dynes, and even more preferably greater than or equal to 70 dynes. Below these values, the wetting of the substrate could prove insufficient and the metallic deposit obtained after metallization could have unsatisfactory adhesion, gloss and reflectivity characteristics. The value of the surface energy can be measured, for example, by techniques known to those skilled in the art consisting of applying a specific solution to the substrate using a brush or a felt-tip pen and measuring the retraction time of the solution thus applied.

[0136] The wetting step Q typically consists of coating the surface of the substrate with a liquid film, for example by spraying or by vaporization / condensation of a wetting liquid, to promote the spreading of the metallization solution(s) (“oxidation-reduction solution(s)”). The choice of wetting liquid is preferably made from the following group: deionized or non-deionized water, optionally with one or more anionic, cationic or neutral surfactants added, an alcoholic solution comprising one or more alcohols (for example isopropanol, ethanol and their mixture), and their mixtures. For example, deionized water with an anionic surfactant and ethanol added may be chosen as the wetting liquid.In a wetting variant in which the wetting liquid is transformed into vapor which is sprayed onto the substrate on which the vapor condenses, it is preferable for the liquid to be essentially aqueous for obvious reasons of industrial convenience. The wetting duration depends on the surface of the substrate considered and the spraying or vaporization / condensation rate of the wetting liquid. The wetting step Q can possibly replace the activation step H.

[0137] Advantageously, rinsing step R, as well as the other rinsing steps which punctuate the process, like step I or step T, consist of bringing all or part of the surface of the substrate into contact with one or more rinsing liquid(s), preferably demineralized water, by spraying an aerosol of the rinsing liquid(s).

[0138] Step D of metallization by non-electrolytic (chemical) deposition by projection of one (or more) metallization solution(s) in the form of aerosol(s) advantageously relates to the process described in documents FR-2 763 962 B1, EP-2 326 747 B1 or EP-2 318 564 B1.

[0139] Metallization step D is advantageously carried out (at least) by non-electrolytic deposition from:

[0140] - either a single metallization solution containing said at least one metal in the form of a metal cation and said at least one reducing agent capable of transforming the metal cation into metal,

[0141] - either two separate solutions: the first solution (“oxidizing solution”) containing at least one metal in the form of a metal cation (oxidant(s)) and the second solution (“reducing solution”) containing one or more reducer(s),

[0142] - or a plurality of separate solutions, each of which may contain either at least one metal in the form of a metal cation (oxidant(s)), or one or more reducing agents, provided that at least one of the solutions ("oxidizing solution") contains at least one metal in the form of a metal cation and that at least one other of the solutions ("reducing solution") contains one or more reducing agents. The reducing agent is advantageously chosen to be strong enough to reduce the metal cation to metal, i.e. the standard redox potential of the oxidizing / reducing agent pair of the chosen reducing agent is lower than that of the oxidizing / reducing agent pair of the oxidant (gamma rule).Such a non-electrolytic variant is particularly advantageous in that it allows the formation, on the surface of a substrate which is indifferently conductive or not, of a solid metal deposit, as envisaged above, which is moreover of a thickness advantageously included in the above-mentioned ranges of values.

[0143] During the metallization step D, the metallization solution(s) is (are) sprayed in the form of one (or more) aerosol(s) onto the masked substrate, and in particular at least onto the unmasked area(s) thereof. By "aerosol" is meant here a set of fine particles of the metallization solution(s) suspended in a gaseous medium (for example, air). It may thus advantageously be a mist of droplets of size less than 100 pm, preferably less than 60 pm, and even more preferably from 0.1 pm to 50 pm, obtained by nebulization and / or by atomization of the metallization solution(s).

[0144] Advantageously, the metallization solution(s) ("oxidation-reduction solutions") may be obtained from solutions, advantageously aqueous, of one (or more) oxidizing metal cation(s) (typically obtained by dissolving one or more corresponding metal salts) and one or more reducing compounds, preferably by dilution of concentrated stock solutions, the diluent preferably being demineralized water. Depending on the nature of the metal deposit to be formed, the projection of the metal solution(s) may be carried out continuously, i.e. in a single operation, or discontinuously by alternating projection phases and relaxation times. For example, for a silver-based metal deposit, the projection will preferably be carried out continuously.For example, for a nickel-based metal deposit, the projection will preferably be carried out discontinuously by alternating projection phases and relaxation times. Depending on the desired thickness of the metal deposit, the projection time can advantageously vary between 0.5 s and 200 s, preferably from 1 s to 50 s and even more preferably from 2 s to 30 s for a substrate surface to be metallized of 1 dm. 2 . Modulation of the projection cone can allow the metallization solution(s) to be projected over a more or less wide area of ​​the substrate. By modulating the projection duration and / or the quantity of metallization solution(s) projected locally, it is possible to obtain a gradient of metal deposit thickness, as mentioned previously.

[0145] The projection of the metallization solution(s) can be carried out using any suitable spraying means, preferably using one or more compressed air paint guns, such as for example one or more high volume low pressure (HVLP) guns. Advantageously, the spraying means and the substrate can be set in relative motion (translation and / or rotation), in order to allow in-line metallization and / or to ensure good projection over all the areas to be metallized of the substrate, in particular in the case where the latter has been thermoformed prior to metallization step D.

[0146] According to a first projection method, one or more solutions of metal cation(s) ("oxidizing solution(s)") and one or more solutions of reducing agent(s) ("reducing solution(s)") are simultaneously and continuously projected onto the surface to be treated, in the form of one or more aerosols. In this case, the mixing between the oxidizing solution and the reducing solution can be carried out just before the formation of the aerosol or by fusion of an aerosol produced from the oxidizing solution and an aerosol produced from the reducing solution, preferably before coming into contact with the surface of the substrate to be metallized. According to a second projection method, one or more solutions of metal cation(s) ("oxidizing solution(s)") are successively projected, by means of one or more aerosols, then one or more solutions of reducing agent(s) ("reducing solution(s)").In other words, the projection of the redox solution is carried out by separate projection(s) of one or more solutions of one or more metal oxidants and one or more solutions of one or more reducers. This second possibility corresponds to an alternating projection of the reducing solution(s) and the solution(s) of metal cation(s). In the context of the second projection method, the association of several oxidizing metal cations to form a multilayer of different metals or alloys is such that the different metal cations are, preferably, projected naturally separately from the reducer but also separately from each other and successively.According to a third projection method, a metallization solution, made metastable, containing a mixture of said at least one metal in the form of a metal cation ("oxidant(s)") and said at least one reducing agent is sprayed in the form of an aerosol, then, after projection onto the surface of the substrate, the metallization solution is activated so that the transformation of the metal cation(s) into metal is triggered, preferably by contact with an initiator, advantageously provided by means of one or more aerosols, before, during or after projection of the metallization solution. The initiation or activation of the redox reaction is then perhaps obtained by any appropriate physical (temperature, UV, etc.) or chemical means.

[0147] Water appears to be the most suitable solvent, without excluding the possibility of using organic solvents, for the preparation of the metallization solution(s) to be sprayed in the form of aerosol(s).

[0148] The concentration(s) of metal salt(s) in the oxidizing solution(s) to be sprayed are preferably between 0.1 g / l and 100 g / l and more preferably between 1 g / l and 60 g / l. Where appropriate, the concentration(s) of metal salt(s) in the stock solution(s) are preferably between 0.5 g / l and 500 g / l, or the dilution factor of the stock solution(s) is preferably between 5 and 5,000. Advantageously, the metal salts are chosen from silver nitrate, nickel sulfate, copper sulfate, tin chloride, aurochloric acid, iron chloride, cobalt chloride and mixtures thereof.

[0149] The selection of the reducing agent(s) is preferably made from the following compounds: borohydrides, dimethylaminoborane, hydrazine, sodium hypophosphite, formalin, lithium aluminum hydride, reducing sugars such as glucose derivatives or sodium erythorbate, and mixtures thereof. The selection of the reducing agent requires taking into account the pH and the properties targeted for the metal deposition. These routine adjustments are within the reach of those skilled in the art. The concentration(s) of metal salt(s) in the reducing solution(s) to be sprayed are preferably between 0.1 g / l and 100 g / l, and more preferably between 1 g / l and 60 g / l. Where appropriate, the concentration(s) of reducer(s) in the stock solution(s) are preferably between 0.5 g / l and 250 g / l, or the dilution factor of the stock solution(s) is preferably between 5 and 2,500.

[0150] Optionally, additional particles, as contemplated in the foregoing, may be incorporated into at least one of the metallization solutions to be projected onto the substrate during metallization step D. The additional particles are thus advantageously trapped in the metal deposit formed on the surface of the substrate.

[0151] As indicated previously, such a method of metallization by projection of aerosol(s) is particularly interesting in that it allows in particular simple and rapid metallization of substrates of all dimensions, and in particular large substrates, and in that it is particularly well suited to the case where metallization step D is carried out after thermoforming step C (variant V1), and where the surface to be metallized is therefore not flat but on the contrary deformed.

[0152] Furthermore, such a method of metallization by projection of aerosol(s) makes it possible, in the context of the invention, to obtain a metallic deposit, possibly multilayer, with excellent properties in terms in particular of adhesion to the substrate, homogeneity of thickness and surface condition (very low roughness). It is thus advantageously possible in particular to obtain in this way one or more metallic pattern(s) having excellent properties in terms of electrical conductivity. What is more, such a method of metallization by projection of aerosol(s) allows particularly fine control of the thickness of the metallic deposit formed, which can therefore in particular be transparent or opaque, depending on the intended applications.

[0153] — Non-electrolytic deposition by immersion

[0154] In accordance with what has been described previously, according to the embodiment in which the metallization of the substrate is carried out by auto-catalytic chemical deposition (or "electroless") by immersion of the substrate in one (or more) metallization solution(s), the metallization step D may advantageously be preceded by a step H of activation of the substrate, and optionally preceded, before said activation step H, by at least one of the following steps, preferably in the following order:

[0155] - satin finishing step S, preferably implemented between step B of forming the temporary masking coating and step H of activation;

[0156] - step T of rinsing the surface of the substrate, in the event of implementation of such a satin finishing step S.

[0157] Advantageously, the satin finishing step S is a treatment step for increasing the surface energy of the substrate as described previously with regard to non-electrolytic metallization by aerosol projection (Step P). The same applies to the rinsing step T.

[0158] As introduced previously, the metallization step D is, in this particular embodiment, typically carried out by immersing the substrate in a bath (“electroless” bath) of a metallization solution, optionally comprising, in addition to one or more metal cation(s) and one or more reducing agent(s), one or more complexing agent(s), one or more stabilizing agent(s), and other possible additives (surfactants, etc.). Typically, during step D, the formation of the metal deposit occurs on all the areas of the substrate on which a catalyst has previously been deposited during the activation step H.

[0159] To the extent that the activation step H is preferably carried out after the step B of forming the temporary masking coating and before the step E of removing the latter, the area(s) of the substrate covered by the temporary masking coating is (are) therefore not catalyzed, and therefore cannot be the site of the formation of a metal deposit.

[0160] Preferably, the metallization step D is carried out here after the step E of removing the temporary masking coating. Indeed, in the event that, on the contrary, the metallization step D is carried out before said step E, it would be advantageous to provide that the temporary masking coating is designed so that the catalyst cannot be adsorbed on the surface of the latter, and that said temporary masking coating is capable of resisting the “electroless” bath, in order to limit the risk of contamination of said “electroless” bath. — Electrolytic deposition

[0161] For more details on this metallization method which can possibly be implemented in step D of metallization, one can refer to the technical literature relating to this technology, and for example to the treatises on galvanostegy.

[0162] - Step E of removing the temporary masking coating -

[0163] In accordance with the above, step E can be carried out:

[0164] - either (in full) before the metallization step D, in the case in particular where the method comprises a step H of activating the surface of the substrate prior to the metallization step D and where the temporary masking coating is intended to allow selective activation of the surface of the substrate;

[0165] - either (in full) after step D;

[0166] - either, more preferably, (in full) during step D, or partly during step D and partly after step D, or partly before step D, partly during step D and partly after step D.

[0167] As introduced previously, step E advantageously comprises at least one dissolution operation, or even essentially consists of a dissolution, of the temporary masking coating by at least one solvent used in the process.

[0168] In the event that the method comprises a step I of rinsing the surface of the metallized substrate, step E of removing the temporary protection may optionally be carried out either during the rinsing step I, or partly during the metallization step D and at least partly during said rinsing step I. In the event that the method comprises a drying step J, step E of removing the temporary protection may optionally be carried out partly during the metallization step D and at least partly during said drying step J.

[0169] The operation of dissolving the temporary masking coating may be carried out, for example, by spraying one (or more) aqueous solvent(s), by spraying one (or more) organic solvent(s), by spraying a mixture of aqueous solvent(s) and organic solvent(s), by immersion in a bath of aqueous solvent(s), by immersion in a bath of organic solvent(s) or by immersion in a bath of a mixture of aqueous solvent(s) and organic solvent(s). Optionally, said dissolving operation may be carried out with the addition of heat, and thus be carried out at a temperature preferably between 30°C and 90°C, and more preferably between 50°C and 80°C. In practice, the time of carrying out step E may depend in particular on the methods of carrying out step D of metallization, and in particular on the metallization method(s) implemented during it.In particular, the removal of the temporary masking coating at least in part during metallization step D assumes that the methods of carrying out the latter allow it and that the residue produced by this removal is not such as to hinder the proper progress of metallization step D.

[0170] — Non-electrolytic deposition by projection in the form of aerosol(s)

[0171] In this embodiment, step E of removing the temporary masking coating may be carried out at least in part during step D, in the advantageous case mentioned above where a solvent capable of dissolving the temporary masking coating is contained in the, or in at least one of the, metallization solution(s) used during step D.

[0172] In practice, and even more preferably, the temporary masking coating is alkali-soluble (or at least alkali-sensitive), and the (or one of the) metallization solution(s) has (have) a strongly alkaline pH (typically greater than 9), so that the metallization solution(s) can dissolve the temporary masking coating during step D. Typically, during the projection of the metallization solution(s) in the form of aerosol(s), the unmasked areas of the substrate are metallized, while the temporary masking coating is dissolved and discharged in the effluents, thus revealing: either the desired metallic pattern(s), in the case where step D is carried out after step C of thermoforming (variant V1); or one or more corresponding “raw” metal pattern(s), as mentioned above, in the case where step D is carried out before step C of thermoforming (Variant V2).

[0173] However, it is preferable that the metallization time, i.e. the time required to form the metal deposit during step D, be limited, so as to prevent any risk of metallization of substrate areas which were initially covered by the temporary masking coating.

[0174] In this embodiment by projection of aerosol(s), it is possible in addition, or alternatively in particular in the case where the metallization solution(s) used do not contain a solvent capable of dissolving the temporary masking coating, to rinse, for example by spraying, the masked and metallized surface of the substrate using one or more solvents capable of dissolving the temporary masking coating. The dissolution of the temporary masking coating is thus accompanied by the removal of any metal deposit present on its surface.

[0175] — Non-electrolytic deposition by immersion

[0176] In this other embodiment, which generally involves the implementation of an activation step H as described above, Step E may typically be carried out between step H and metallization step D, by applying to the surface of the masked substrate a solvent capable of dissolving the temporary masking coating. Such application may be carried out for example by immersing the masked substrate in said solvent or by spraying said solvent onto the surface of the masked substrate, followed by rinsing.

[0177] This dissolution reveals the activated area(s) of the substrate surface which will be able to receive the metal deposit intended to form the desired metal pattern(s). The area(s) of the substrate surface which were previously covered by the temporary masking coating were not activated (adsorption of the catalyst) during step H, so that no metal deposit will be formed there for at least the time necessary for the formation of a metal deposit on the activated area(s) of the substrate surface. — Electrolytic deposition

[0178] In this embodiment, Step E of removing the temporary masking coating may optionally be carried out at least in part during step D of metallization, typically in the case where the metallization solution used contains a solvent capable of dissolving the temporary masking coating and where the time required for the formation of the metal deposit by electrolytic deposition is advantageously less than or equal to the time required for the dissolution of the temporary masking coating by said solvent. Alternatively, or optionally in a complementary manner, step E may be carried out after step D of metallization, and for example during a step I of rinsing the metallized substrate carried out using a rinsing liquid containing or forming a solvent capable of dissolving the temporary masking coating.

[0179] - Step I of rinsing the surface of the metallized substrate -

[0180] After the metallization step D, the method may comprise, as mentioned above, a step I of rinsing the surface of the metallized substrate. The rinsing step I may, like the other rinsing step(s) (steps P and R in particular) that the method may comprise, be carried out in any known and appropriate manner, for example by spraying / projecting one (or more) rinsing liquid(s) using an HVLP gun or by dipping / immersing in one or more rinsing liquid(s). The latter is preferably water, and more preferably demineralized water, except possibly in the case where the rinsing liquid contains or forms a solvent (other than water) for dissolving the temporary masking coating.

[0181] - Step J of drying the surface of the metallized substrate -

[0182] After step I of rinsing the surface of the metallized substrate, the method may comprise a step J of drying the surface of the metallized substrate. The drying step J consists, like any other drying steps that could occur after each rinsing step, of removing the rinsing liquid. Such drying may typically be carried out at room temperature by blowing a stream of compressed air, for example under a pressure of 5 bar, or using an air knife type blowing system. Drying in the open air or in an oven is also possible.

[0183] - Stages K, L, M of finishing treatment of the surface of the metallized substrate -

[0184] One (or more) additional “finishing” step(s) may be implemented after the metallization step D, and preferably again after the thermoforming step C in the case where this is carried out after the metallization step D, in order, for example, to protect the metal pattern(s) formed from the metal deposit against external physical and / or chemical attacks, and / or in order to modify or improve the properties of the metal pattern(s), for example in terms of electrical conductivity and / or optical properties.

[0185] In this respect, the method may optionally comprise a step K of complementary metallization (or “thickening step”) by forming at least one additional metal deposit on the surface of the (initial) metal deposit obtained at the end of the metallization step D. Such a step K of complementary metallization may advantageously be carried out by electrolytic deposition (for example, by galvanostegy) or by non-electrolytic deposition (“electroless”). Said additional metal deposit may be of identical composition or not to that of the initial metal deposit. For example, the additional metal deposit may comprise, or be formed from, at least one metal chosen from silver, nickel, copper, gold, iron, cobalt, tin, zinc, ruthenium, palladium, one or more oxides thereof, or one or more alloys thereof, or a combination thereof.Such a complementary metallization step K may in particular prove to be of interest when the (initial) metallization step D is carried out by non-electrolytic chemical deposition, as envisaged previously, and it is desired to obtain one (or more) metallic pattern(s) with a total thickness greater than 5 μm.

[0186] Alternatively or additionally, the method may optionally comprise a step L of passivation of the metal deposit(s) forming the metal pattern(s), in order to protect it against corrosion or oxidation. Typically, such a passivation step L may be carried out by spraying, or by immersion in, at least one passivation solution adapted to the composition of the metal deposit(s) forming the metal pattern(s), such as for example a solution of inorganic tin salt(s), an organic precious metal passivation solution such as is commonly available commercially, or an inorganic solution from the family of silanes or silicon oxides (SiO x ).

[0187] Alternatively or additionally, the method may possibly include

[0188] - after said metallization step D and thermoforming step C, and preferably after step E of removing the temporary masking coating -, a step M of forming a finishing coating covering the surface of the substrate (metallized thermoformed substrate) bearing the metallic pattern(s). Such a finishing coating, organic or inorganic, may constitute a protective coating against mechanical friction, against oxidation, etc., and / or an electrical insulating coating, and / or a decorative coating. Step M of forming the finishing coating may typically be carried out by depositing / applying, by any known and suitable technique, at least one finishing layer of a curable and / or crosslinkable liquid composition (for example, by UV exposure or by thermal baking) on ​​the surface of the substrate bearing the metallic pattern(s).The liquid composition may be a paint or a varnish, advantageously chosen for example from the following group: alkyds, polyurethanes, epoxies, vinyls, acrylics and their mixtures. Preferably, the liquid composition is a varnish, optionally colored / pigmented, advantageously chosen from the following compounds: epoxies, alkyds and acrylics.

[0189] - Overmolding step N -

[0190] Optionally, the method according to the invention may comprise, after thermoforming step C, a step N of overmolding the (thermoformed) substrate. Step N may be carried out after metallization step D in the case where the latter is carried out after thermoforming step C, or on the contrary before metallization step D in the event that the metal deposit / metal pattern(s) might be damaged during overmolding step N. Overmolding step N (or injection molding) advantageously consists of injecting a polymer material or a mixture of polymer materials, compatible with the nature of the material of the thermoformed substrate, into a mold inside which the thermoformed (and preferably metallized) substrate has been previously positioned.Such an overmolding step can advantageously make it possible, for example, to form a protective and / or support part for the thermoformed (and preferably metallized) substrate.

[0191] - Step O of assembly of additional components -

[0192] For certain applications of the three-dimensional article, it may be desired to assemble to the thermoformed substrate provided with the metallic pattern(s), overmolded or not, one (or more) electrical, electronic and / or optoelectronic component(s), in a through-hole and / or surface-mounted manner (electrical connector(s), electric cable(s) / wire(s), light-emitting diode(s), electronic chip(s), etc.). Advantageously, such an assembly step O may be implemented using one or more robotic surface-mounted component placement (SMD) systems, commonly called “pick-and-place” or “P&P” machines, one or more robotic arms, or any other known advantageously automated means of depositing liquids / components on a 2.5D or 3D surface.Such an assembly step can advantageously be carried out by soldering and / or using an electroconductive adhesive, isotropic or anisotropic, taking for example the form of a film or a paste, and of any suitable chemical nature (silicone, epoxy, acrylic, etc.). If necessary, an operation of baking the electroconductive adhesive can be implemented.

[0193] Ultimately, the method according to the invention presents in particular the following advantages:

[0194] - it makes possible the manufacture of three-dimensional articles, of any size and complex shape, provided with decorative and / or functional metal patterns, which may themselves be of large size and / or complex shape;

[0195] - it allows the manufacture of three-dimensional articles provided with metallic patterns which can be particularly fine, precise and / or complex;

[0196] - it allows the manufacture of three-dimensional articles provided with metallic patterns which are particularly resistant to external aggressions; - it allows the manufacture of three-dimensional articles provided with metallic patterns which are particularly homogeneous and regular, both in terms of thickness and in terms of surface appearance (very low roughness);

[0197] - it allows the manufacture of three-dimensional articles provided with metallic patterns in a multiplicity of possible metals (pure metals, metallic alloys, metallic oxides, etc.);

[0198] - it allows the manufacture of three-dimensional articles with metallic pattern(s) which can be used in a large number of technical applications, in particular among the most demanding and sensitive in terms of properties of the metallic patterns (fineness, thickness, purity, electrical conductivity, roughness, etc.), said metallic patterns being able to be decorative and / or functional, and thus being able to advantageously form or contribute to forming, for example and in a non-limiting manner, one or more printed circuits, one or more integrated circuits on a semiconductor substrate, one or more sensor / detector electrodes, one or more electrodes of an electrical heating / defrosting device, one or more radiating element(s) of a radiofrequency antenna (WiFi®, RFID, etc.), one or more coding pictograms capable of being read by electronic devices, one or more figurative and / or scriptural information identifying a product which incorporates or with which said three-dimensional article is associated, in particular a commercial product, such as a decorative visual or design on packaging, on an automotive product, etc.;.

[0199] - it can be implemented in an industrial context for large-scale production;

[0200] - it is particularly quick, simple and economical to implement.

[0201] Below will now be described, in connection with the appended figures, two examples of implementation of a method according to the invention for the manufacture of three-dimensional articles with metallic pattern(s). Example 1 illustrates in particular the implementation of variant V1 in which thermoforming step C is carried out before metallization step D, while example 2 illustrates in particular the implementation of variant V2 in which thermoforming step C is carried out after metallization step D. - Example 1 - Manufacture of a three-dimensional RFID antenna -

[0202] - Step A: a flat substrate is provided, formed from a polycarbonate film with a thickness of 250 μm, and 330 mm long by 250 mm wide;

[0203] - Step B: a temporary masking coating is formed by screen printing, from a thermodeformable and alkali-sensitive masking composition developed by the company JET METAL TECHNOLOGIES®, on the polycarbonate film. The deposited masking composition layer is then dried by desolvation at 60° for 5 min. As illustrated as an example in Figure 1, the temporary masking coating thus formed delimits at least one unmasked area (in the center);

[0204] - Step C: the film thus selectively masked is then heated homogeneously by infrared (IR) up to 215 °C, then pressed onto a counterform, in order to thermoform it. Figure 2 illustrates an example of a thermoformed masked film obtained after cooling and hardening;

[0205] - Step P / Step Q: the surface of the thermoformed masked film is subjected to a treatment to increase the surface energy by plasma treatment (so-called “air” plasma: 80% nitrogen / 20% oxygen at 0.5 mbar ( / .e. 50 Pa) for 2 min), so that at the end of this treatment, the surface energy of the thermoformed masked film is greater than 50 dynes and said surface can be perfectly wetted by spraying water, the water then forming a continuous film on the surface of the thermoformed masked film;

[0206] - Step H: a stannous chloride-based sensitizing solution is sprayed onto the surface of the thermoformed masked film for 10 s using an HVLP gun;

[0207] - Step R: the surface of the thermoformed masked film is rinsed to remove the sensitizing solution by spraying demineralized water for 10 seconds using an HVLP gun;

[0208] - Step D / Step E: a metallic deposit is formed on the surface of the thermoformed masked film and sensitized by simultaneous projection of a first aqueous metallization solution (oxidizing solution) based on silver nitrate at a concentration of 2 g / l and having a pH > 9, and a second metallization solution (reducing solution) based on glucose, for 80 s using HVLP guns set to a spray pressure of less than 2.5 bar (i.e. 2.5.10 5 Pa). Under the effect of the alkalinity of the first metallization solution, the temporary, alkali-sensitive masking coating is partially degraded and removed from the surface of the substrate with the effluents, thus revealing the desired metallic pattern;

[0209] - Step I: the surface of the metallized thermoformed film is rinsed with water using an HVLP gun. This rinse removes any residue of the temporary masking coating. If necessary, additional rinsing is carried out by immersion in a bath or by spraying solutions containing a solvent such as ethanol / isopropanol to ensure the complete absence of residue of the temporary masking coating and any metallic deposits carried by the latter;

[0210] - Step J: the surface of the metallized thermoformed film is dried at room temperature under an air flow of 5 bar (i.e. 5.10 5 Pa). The result obtained is illustrated in Figure 3, in which the thermoformed polycarbonate film and the solid elemental silver metallic pattern obtained on its surface form a three-dimensional RFID antenna;

[0211] - Step O: an RFID antenna electronic chip is then assembled on the metallized thermoformed film, by soldering or using an electroconductive adhesive;

[0212] - Step M: the metallized surface of the three-dimensional article thus obtained is then covered using a protective varnish developed by the company JET METAL TECHNOLOGIES®.

[0213] - Example 2 - Manufacture of a three-dimensional article comprising decorative motifs in the form of silver lines -

[0214] - Step A: a flat substrate formed from a polycarbonate film with a thickness of 250 μm, and 380 mm long by 310 mm wide, is provided;

[0215] - Step B: a temporary masking coating is formed by screen printing, from an alkali-sensitive masking composition developed by the company JET METAL TECHNOLOGIES®, on the polycarbonate film. The deposited masking composition layer is then dried by desolvation at 80° for 5 min. As illustrated as an example in Figure 4, the temporary masking coating thus formed delimits a plurality of unmasked areas in the form of lines;

[0216] - Step P / Step Q: the surface of the masked film is subjected to a treatment to increase the surface energy by direct ceramic corona treatment, at a speed of 3 m / min and in 3 passes, so that at the end of this treatment, the surface energy of the masked film is greater than 50 dynes and said surface can be perfectly wetted by spraying water, the water then forming a continuous film on the surface of the masked film;

[0217] - Step H: a stannous chloride-based sensitizing solution is sprayed onto the surface of the masked film for 10 s using an HVLP gun;

[0218] - Step R: the surface of the masked film is rinsed to remove the sensitizing solution by spraying demineralized water for 10 seconds using an HVLP gun;

[0219] - Step D / Step E: a metallic deposit is formed on the surface of the masked and sensitized film by simultaneous projection of a first aqueous metallization solution (oxidizing solution) based on silver nitrate at a concentration of 2 g / l and having a pH > 9, and a second metallization solution (reducing solution) based on glucose, for 80 s using an HVLP gun. Under the effect of the alkalinity of the first metallization solution, the temporary, alkali-sensitive masking coating is partially degraded and removed from the surface of the substrate with the effluents;

[0220] - Step I: the surface of the metallized film is then rinsed consecutively with water using an HVLP gun for 10 s, then with a rinsing liquid "SelectRinse" developed by the company JET METAL TECHNOLOGIES® for 15 s using an HVLP gun in order to remove any residues of the temporary masking coating, then again with water using an HVLP gun. - Step J: the surface of the metallized film is dried at room temperature under an air flow of 5 bar (i.e. 5.10 5 Pa). Figure 5 illustrates as an example the metallized film thus obtained;

[0221] - Step C: The selectively metallized film is then heated homogeneously by infrared (IR) up to 215°C, then pressed onto a counterform, in order to thermoform it. Figure 6 illustrates as an example the thermoformed masked film thus obtained after cooling and curing, which can then form the three-dimensional article as such, or be used to form said three-dimensional article. POSSIBILITY OF INDUSTRIAL APPLICATION

[0222] The invention finds application in the general technical field of three-dimensional articles provided with metallic, decorative and / or functional pattern(s), and methods of manufacturing these articles.

Claims

DEMANDS 1. A method for manufacturing a three-dimensional article comprising at least one metallic motif, comprising at least: - a step A of supplying a flat substrate made of thermoformable material; - a step B of forming on a surface of the flat substrate a temporary masking coating which adheres to said surface, to obtain a masked substrate having at least one unmasked area; - a step C of thermoforming the flat substrate to give it a general three-dimensional shape; - a step D of metallization of the masked substrate to form a metallic deposit on the latter at least on said unmasked area; - and a step E of removal of said temporary masking coating, the thermoforming step C being carried out before the metallization step D and before the removal of said temporary masking coating step E, the metallization step D being carried out by non-electrolytic deposition from one or more metallization solutions containing at least one metal in the form of a metallic cation and at least one reducing agent capable of transforming the metallic cation into metal, by spraying the metallization solution(s) in the form of one or more aerosols.

2. A method according to any one of the preceding claims, wherein the metal deposit is made of solid metal.

3. A method according to any one of the preceding claims, wherein the metal deposit has, at the end of the metallization step D, a thickness of between 10 nm and 5 pm, preferably between 10 nm and 1 pm, and preferably also between 10 nm and 500 nm.

4. A method according to any one of the preceding claims, wherein step D is carried out such that the thickness of the metallic deposit varies according to the extent of said metallic deposit, the metallic deposit having at least a first zone and a second zone, distinct from the thickness of the deposit metallic being increasing or decreasing from said first zone to said second zone. A method according to any one of the preceding claims, wherein step E of removing the temporary masking coating is carried out during step D of metallization, or partly during step D of metallization and partly after step D of metallization, or partly before step D of metallization, partly during step D of metallization and partly after step D of metallization. A method according to any one of the preceding claims, wherein step E of removing the temporary masking coating comprises at least one operation of dissolving the temporary masking coating with at least one solvent used in the method, said temporary masking coating preferably being alkali-soluble so as to be able to be dissolved preferably by an alkaline solvent used in the method.A method according to claims 5 and 6, wherein said solvent is contained in the metallization solution(s). A method according to any one of the preceding claims, wherein step B of the formation of the temporary masking coating is carried out by selectively depositing a layer of a liquid or paste-like masking composition onto the surface of the flat substrate, for example by screen printing and / or direct printing, optionally followed by drying and / or curing of the masking composition layer. A method according to any one of the preceding claims, wherein the temporary masking coating, after the formation step thereof, has a thickness of between 100 nm and 50 pm, preferably between 500 nm and 20 pm, and preferably further between 1 pm and 10 pm.A method according to any one of the preceding claims, wherein the flat substrate is a film, sheet or plate of a polymer material. thermoformable or a thermoformable polymer matrix composite material, preferably with a thickness between 8 µm and 15 mm, and more preferably between 25 µm and 10 mm. A method according to any one of the preceding claims, comprising a step G of defining a two-dimensional masking pattern, whereby the temporary masking coating is then formed on the surface of the flat substrate, based on a model of a deformation of the flat substrate during the thermoforming step C and a representation of the metallic pattern to be obtained. A method according to any one of the preceding claims, comprising, subsequent to the thermoforming step C, an overmolding step N of the substrate.

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