Manufacturing process for a watch component

Abstract

The invention relates to a method for manufacturing a watch component comprising the following steps: a. providing a support made of polymer material (10); b. forming at least one base layer on at least a part of the support comprising a contact layer formed on the support, said contact layer being based on a metallic material whose equilibrium constant with respect to cyanide ions is greater than or equal to -5; c. forming at least one main layer (12) above said at least one base layer by electroplating using a galvanic bath comprising cyanide ions in order to form a watch component.

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a method for manufacturing a watch component comprising a first step of thin metal deposition on a polymer material support followed by a second step of thick metal deposition by electroplating. TECHNICAL BACKGROUND OF THE INVENTION

[0002] Electroforming is increasingly used in various sectors of activity such as watchmaking. It consists of galvanic growth (electroplating) in a mold (for example obtained by photolithography (LiGA process)). Thus, electroforming can be used for mass replication processes. These technologies generally use a support (for example a substrate or a mandrel) made of polymer material on which the electroforming takes place.

[0003] An electroforming process is generally used on supports for double-sided metal growth. A first step of thin metal deposition is therefore carried out on a polymer material support in order to coat the support, then a second step of metal deposition by electroplating, which limits the infiltration of the electrolyte from the galvanic bath towards the support.

[0004] However, in watchmaking, growths are generally desired on a single face. This means that the polymer material support can interact with the electrolytics of the galvanic bath. It has been observed that, due to incompatibility of the electrolyte, delaminations of the metal deposit occur, particularly in the case of cyanide electrolytes that can be found in various galvanic baths, such as those for obtaining an 18-carat gold deposit widely used in watchmaking but also for other deposit metals. SUMMARY OF THE INVENTION

[0005] The aim of the invention is to propose a method for manufacturing a watch component comprising a first step of thin metal deposition on a polymer material support followed by a second step of thick metal deposition by electroplating which encounters little or no defect in the adhesion of the galvanic deposit even if the galvanic bath, comprising a cyanide electrolyte, is in contact with the polymer material support.

[0006] To this end, the invention relates to a method for manufacturing a timepiece component comprising the following steps: a. providing a support made of polymer material; b. forming at least one base layer on at least part of the support comprising a contact layer formed on the support, said contact layer being based on a metallic material whose equilibrium constant with respect to cyanide ions is less than or equal to 5; c. forming at least one main layer above said at least one base layer by electroplating using a galvanic bath comprising cyanide ions in order to form a timepiece component.

[0007] Conventionally, a layer of a precious metal, such as pure gold, can be deposited by physical vapor deposition (sometimes known by the abbreviation PVD) on a polymer support to support a subsequent electroforming step. In fact, precious metals such as pure gold are preferentially deposited on polymer supports because they are very stable, particularly due to their resistance to different environments: acid, basic, chlorinated, no oxidation in ambient air, possible galvanic recovery.

[0008] Following the delaminations of galvanic deposits observed, particularly in the case of cyanide electrolytes in galvanic baths to obtain an 18-carat gold deposit, it was investigated where the chemical incompatibility between the cyanide electrolyte and the materials used could come from.

[0009] It has been found that compatibility is based on the nature of the metal-polymer support interactions. These are weak physisorption bonds that can be easily cleaved in the presence of a complexing agent with strong affinities for the metal. This strong affinity can be characterized by an equilibrium constant pKf, equivalent to the value of -log (Kf), Kf being the formation constant. The higher its value, the higher the stability of the complex and the higher the metal-ligand affinity.

[0010] Therefore, in order to be able to resort to electroforming in the presence of a cyanide electrolyte, it has been found that it is necessary to choose a low metal - cyanide ion affinity. Contrary to a technical prejudice, the pure gold deposit is in fact not a good candidate for a subsequent galvanic deposition because its affinity is very strong with cyanide ions. Thus, it has been calculated that the equilibrium constant pKf is located between 38.3 and 15.27 depending on the cyanide derivative present in the electrolyte. There is therefore an exchange and cleavage of the metal - polymer support bond which causes delamination.

[0011] After research and tests, it has been observed that, advantageously according to the invention, when said at least one base layer, deposited during step b, is based on a metallic material whose equilibrium constant pKf with respect to cyanide ions is less than or equal to 5, no delamination during step c is observed. This is a decisive advantage, in particular for watch components which are very frequently manufactured using at least one cyanide galvanic bath.

[0012] Thus, contrary to a technical prejudice, depending on the electrolyte of the galvanic bath, the material(s) of said at least one base layer must be selected so as to have a low chemical affinity with the components of the galvanic bath in order to be able to remain the site of initiation of the galvanic growth without delamination from the polymer material support. This consideration is valid for a wide range of applications such as the manufacture of composite components, i.e. comprising the polymer material support in the final watch component or not, or the use of the method according to the invention in a manufacturing process such as comprising the adhesion of said at least one base layer to a photosensitive resin (such as for example SU-8), said at least one base layer then being thickened using a galvanic deposition without delamination.

[0013] The invention may also include one or more of the following optional features, taken alone or in combination.

[0014] Step a may comprise the phases i intended to provide a replication tool comprising in part a geometry to be reproduced of the watch component, ii intended to at least partially cover the replication tool with a polymer material in order to form a support made of polymer material with a geometry complementary to the geometry to be reproduced of the watch component and iii intended to release the support made of polymer material from the replication tool. Of course, whether the watch component comprises or does not comprise the support made of polymer material, step a could be different, such as in particular forming the support made of polymer material without using a replication tool and / or from an injection mold.

[0015] Even more effectively, said at least one base layer is based on a metallic material whose equilibrium constant with respect to cyanide ions is less than or equal to 3. Such a metallic material may be based on chromium and / or aluminum and / or iron and / or tin and / or titanium. It is therefore understood that each metallic material may be pure or in the form of the main element of an alloy of at least one other metallic material from the list and / or at least one other element not belonging to the list.

[0016] Said at least one base layer may comprise several layers, that is to say may further comprise at least one second upper layer formed above said contact layer, said at least one second upper layer having a lower capacity to be passivated compared to each other base layer in order to facilitate the initiation of step c. Indeed, depending on the speed of passivation of said contact layer, it may be difficult to initiate step c to form said at least one main layer by electroplating. In this preferred variant, said at least one base layer therefore comprises at least two base layers.A first base layer, called the contact layer, is formed on the support based on a metallic material whose equilibrium constant with respect to cyanide ions is less than or equal to 5 (or 3) and a second base layer, called the upper layer, is formed above the first contact layer and is more stable than the first contact layer to ensure the implementation of step c. Said at least one second upper layer may, for example, be based on copper and / or gold and / or silver. It is therefore understood that each metallic material may be pure or in the form of the main element of an alloy of at least one other metallic material from the list and / or at least one other element not belonging to the list.

[0017] Step b is preferably obtained by physical vapor deposition. Of course, other deposition methods can be envisaged without departing from the scope of the invention.

[0018] After step c, the method may include a step d intended to machine the watch component in order to modify its shape by removing material. Advantageously according to the invention, it is thus possible to work and / or decorate and / or remove any surplus of said at least one main layer while the support made of polymer material is still integral with said at least one base layer. Step d may, for example, make it possible to form at least one fixing element for the watch component. By way of non-limiting example, step d could, for example, form feet of the watch component forming a watch dial in order to fix the latter to a watch movement.

[0019] After step c or after step d, according to a particular embodiment, the method may comprise a step e intended to release the watch component from the support so that the watch component comprises said at least one base layer and said at least one main layer, i.e. without support. This step e may in particular be used for a mass replication process in which the support made of polymer material is used to form several watch components at the same time during the method according to the invention.

[0020] After step e (which may be preceded by step c or step d), according to a particular embodiment, the method may comprise a step f (final step) intended to form at least one decorative layer on at least a portion of the watch component in order to modify the aesthetic appearance of the watch component. Typically, this makes it possible to form said at least one main layer based on a less noble metallic material such as pure copper (or one of its alloys) and then to cover (for example by another electroplating) all or part of said at least one main layer with at least one decorative layer made of a more noble material such as based on a precious metal such as pure gold (or one of its alloys) in order to give a more high-end finish to the watch component.

[0021] Depending on the nature of said at least one base layer, step f may comprise a preliminary phase intended to depassivate said at least one base layer followed by a phase of deposition by electroplating of said at least one decorative layer. Indeed, if said at least one base layer is based on a material having the capacity to be passivated very quickly, the adhesion to said at least one base layer after release from the support may be insufficient.

[0022] Depending on the nature of said at least one base layer, step f may comprise a preliminary phase intended to remove said at least one base layer followed by a phase of deposition by electroplating of said at least one decorative layer. Indeed, if said at least one base layer is based on a material having the capacity to be very quickly passivated, the adhesion to said at least one base layer after release from the support may be insufficient.

[0023] Of course, step f can be obtained by another type of deposition such as, for example, physical vapor deposition, chemical vapor deposition or autocatalytic deposition. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Other features and advantages of the invention will become clear from the description given below, for information purposes only and in no way limiting, with reference to the appended drawings, in which: – Figure 1 is a schematic view of an example of a timepiece; – Figures 2 to 6 are schematic views of successive steps of an example of a first embodiment of a method according to the invention; – Figures 7 to 9 are schematic views of successive steps of an example of a second embodiment of a method according to the invention; – Figure 10 is a diagram representing an example of a method according to the invention. DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT OF THE INVENTION

[0025] In the various figures, identical or similar elements bear the same references, possibly with the addition of an index. The description of their structure and function is therefore not systematically repeated.

[0026] In all that follows, the orientations are the orientations of the figures. In particular, the terms “upper”, “lower”, “left”, “right”, “above”, “below”, “forward” and “backward” are generally understood to refer to the direction in which the figures are represented.

[0027] By "polymer" is meant all materials formed from at least one polymer chain, sometimes called fiber, more or less long which can be of natural or synthetic origin. In the context of the invention, the term polymer can therefore refer to a resin (in particular photosensitive such as SU-8) or an organic varnish. In the context of the invention, by way of non-limiting example, a polymer material can comprise, for example, polycarbonate (PC) and / or polymethyl methacrylate (PMMA, sometimes called plexiglass) and / or cycloolefin copolymer (COC) and / or acrylonitrile butadiene styrene (ABS) and / or methyl methacrylate acrylonitrile butadiene styrene (mABS).

[0028] By "based on" is meant a material or alloy constituting at least 50% by total mass or weight of a given element. By way of non-limiting example, a gold-based material means a material formed from pure gold (24 carat gold) or a material formed by alloying gold with at least one other element, the gold constituting at least 50% by total mass or weight of the material.

[0029] In the following, unless otherwise indicated, all percentages (%) indicated are percentages by total mass or weight (in English “weight”).

[0030] By "pure metal" is meant a material theoretically formed at 100% by total mass or weight of a given metal, i.e. without any other alloying metal. In practice, depending on the manufacturing process, the material obtained may include so-called pollution elements whose proportion by weight does not exceed 0.2% of the total mass of the alloy which generally prevents obtaining 100% of metal by total mass but rather substantially between 97% and 100%.

[0031] By “thin deposit” is meant a thickness of deposited material of at most 1000 nm such as said at least one base layer 11 for example implemented by step b of the method according to the invention. Preferably, the thin deposit can also be at least 1 nm. The thin deposit may thus comprise a thickness of deposited material equal to 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 850 nm, 900 nm or 1000 nm. The purpose of this thin deposit is to provide a compatible layer to serve as a seat for the future electroplating (step c) because the support 10 made of polymer material does not allow it.

[0032] By “thick deposit” is meant a thickness of deposited material of at least 2 µm such as said at least one main layer 12 for example implemented by step c of the method according to the invention. Preferably, the thin deposit can also be at most 1000 µm. The very thick deposit can thus include a thickness of deposited material equal to 2 µm, 5 µm, 10 µm, 20 µm, 30 µm, 40 µm, 50 µm, 60 µm, 70 µm, 80 µm, 90 µm, 100 µm, 150 µm, 200 µm, 250 µm, 300 µm, 350 µm, 400 µm, 450 µm, 500 µm, 550 µm, 600 µm, 650 µm, 700 µm, 750 µm, 800 µm, 850 µm, 900 µm or 1000 µm. The purpose of this thick deposit (compared to each of the thin deposits) is to provide a mechanically robust layer to serve as the main metal part (solid metal part). Preferably, the thick deposit has a thickness of deposited material at least equal to 200 µm.

[0033] By “timepiece” is meant all types of instruments for measuring or counting time such as clocks, small clocks, watches, etc.

[0034] By "watch movement" we mean all types of mechanism capable of counting time whether they are powered by mechanical energy (for example a barrel) or electrical energy (for example a battery).

[0035] By “dressing” is meant all types of devices capable of containing, displaying, decorating and / or controlling a watch movement such as, for example, all or part of a case, a bracelet or a display.

[0036] By “micromechanical part” we mean all types of parts that can be used in a timepiece, in particular to form its watch movement.

[0037] The method according to the invention is intended to manufacture a component 1 in the watchmaking field which is in particular intended to be mounted in a timepiece 2. Thus, the component 1 can form all or part of a watch exterior such as all or part of a dial (as illustrated in FIG. 1) or a flange, a display such as a hand or a disc, a case, a bracelet, a crystal or a control member such as a crown or a push button. Component 1 may also form all or part of a watch movement 3 such as a micromechanical part such as all or part of an escapement device such as a Swiss anchor mechanism, a resonator such as a balance-spring mechanism, an energy source such as a barrel, an automatic winding system or a battery, a gear train such as a mobile or a toothed wheel, a spring, a screw, a bridge or a plate.

[0038] As will be explained in more detail below, the method according to the invention allows the manufacture of a metallic component 1 (for example comprising several metallic materials) or of a composite component 1, that is to say comprising the support made of polymer material in the final watch component 1.

[0039] Advantageously according to the invention, the method according to the invention can also be used as a sub-step of a manufacturing process requiring the adhesion of said at least one base layer, for example, on a photosensitive resin (such as for example SU-8), said at least one base layer then being thickened using galvanic deposition without delamination.

[0040] Conventionally, a layer of pure gold is deposited by physical vapor deposition on a polymer support to support a subsequent electroforming step. In watchmaking, galvanic baths containing cyanide electrolytes such as the two examples cited below can be used.

[0041] Example 1: KCN: 18 to 35 gl<-1> Au: 6.0 to 12 gl<-1>(provided by KAu(CN)6) Copper: 55 to 100 gl<-1>

[0042] Example 2: KCN: 27 to 30 gl<-1> Au: 5 gl<-1>(provided by KAu(CN)6) Copper: 55 gl<-1> Indium: 0.8 gl<-1>

[0043] Following delaminations of galvanic deposits observed, particularly in the case of cyanide electrolytes in galvanic baths to obtain an 18-carat gold deposit, it was investigated where the chemical incompatibility between the cyanide electrolyte and the materials used could come from.

[0044] The invention thus aims to propose a method for manufacturing a watch component 1 comprising a first step b of thin metal deposition on a polymer material support followed by a second step b of thick metal deposition by electroplating which encounters little or no defect in the adhesion of the galvanic deposit even if the galvanic bath, comprising a cyanide electrolyte, is in contact with the polymer material support.

[0045] It has been found that compatibility is based on the nature of the metal-support interactions in polymer material. These are weak physisorption bonds that can be easily cleaved in the presence of a complexing agent with strong affinities for the metal. This strong affinity can be characterized by an equilibrium constant pKf. The higher its value, the higher the stability of the complex and the metal-ligand affinity.

[0046] This equilibrium constant pKfest depends on the complexation constant Kc or the formation constant Kf in the case of metal-ligand bonds.

[0047] The formation of the complex follows the following reaction: M<t+> + nL <u->↔ [M(L)n]<t-nu+> (1) with: M: metal L: ligand n: number of ligands t and u: number of charges

[0048] The formation constant Kf can thus be written:

[0049] Finally, the equilibrium constant pKf can be written: pKf= - log(Kf) (3)

[0050] Therefore, in order to be able to resort to electroforming in the presence of a cyanide electrolyte, it has been found that it is necessary to choose a low metal - cyanide ion affinity. Contrary to a technical prejudice, the pure gold deposit is ultimately not a good candidate for a subsequent galvanic deposition because its affinity is very strong with cyanide ions. Thus, it has been calculated that the equilibrium constant pKf is located between 38.3 and 15.27 depending on the cyanide derivative present in the electrolyte. There is therefore an exchange and cleavage of the metal - polymer support bond which causes delamination.

[0051] After research and tests, it has been observed that, advantageously according to the invention, when said at least one base layer, deposited during step b, is based on a metallic material whose equilibrium constant pKf with respect to the cyanide ions is less than or equal to 5, no delamination during step c is observed. This is a decisive advantage, in particular for watch components manufactured using at least one cyanide galvanic bath.

[0052] For this purpose, as visible in Figure 10, the invention relates to a method for manufacturing a timepiece component comprising the following steps: a. providing a support 10 made of polymer material; b. forming at least one base layer 11 on at least a portion of the support 10 comprising a contact layer formed on the support 10, said contact layer being based on a metallic material whose equilibrium constant pKf with respect to cyanide ions is less than or equal to 5; c. forming at least one main layer 12 above said at least one base layer 11 (i.e. one (or more) base layer(s) 11 or on the one(s) which form(s) the upper surface) by electroplating using a galvanic bath comprising cyanide ions in order to form a timepiece component 1.

[0053] Thus, contrary to a technical prejudice, depending on the electrolyte of the galvanic bath, the material(s) of said at least one base layer 11 must be selected so as to have a low chemical affinity with the components of the galvanic bath in order to be able to remain the site of initiation of the galvanic growth without delaminating from the support 10 made of polymer material. This consideration is valid for a wide range of applications such as the manufacture of composite watch component 1, i.e. comprising the support made of polymer material in the final watch component 1 or not, or the use of the method according to the invention in a manufacturing process such as comprising the adhesion of said at least one base layer 11 on a support 10 made of photosensitive resin (such as for example SU-8), said at least one base layer 11 then being thickened using a galvanic deposit (said at least one main layer 12) without delamination.

[0054] In the example illustrated in Figures 2 and 3, step a may comprise a first phase i intended to equip a replication tool 8 partly comprising a geometry (shape 8a to be replicated) to be reproduced of the watch component 1. Then, a second phase ii is intended to at least partially cover the replication tool 8 (in particular its shape 8a to be replicated) with a polymer material in order to form a support 10 made of polymer material with a complementary geometry (replication shape 10a) of the geometry (shape 8a to be replicated) to be reproduced of the watch component 1. The second phase ii may be obtained by plastic injection (the material of the part 10 is hot-pressed in an injection mold), by casting (the material is cast and crosslinked on the mold) or by embossing (the mold 8 is pressed onto the material 10 before drying (evaporation of the solvent), cooling, or crosslinking (chemical, photochemical).

[0055] Finally, a third phase iii is intended to release the support 10 made of polymer material from the replication tool 8 as illustrated in FIG. 3. The third phase iii can be obtained by solubilization of the support 10, by thermal shock (heating or cooling, the different expansion variations of which for each material will release the support 10) or by mechanical shock (stretching, twisting, contraction, etc. allowing the support 10 to be released). For thermal and mechanical shocks, prior passivation of the contact surface of the tool 8 can be provided to facilitate the detachment of the support 10.

[0056] Of course, whether the watch component 1 includes or does not include the support 10 made of polymer material, step a could be different, such as forming the support 10 made of polymer material without using a replication tool 8 and / or from an injection mold (for example, with a fixing element for the future watch component 1). As a non-limiting example, the support 10 could also be obtained from a flat substrate made of a first polymer material covered with an openwork mask (obtained for example from photolithography) made of a second polymer material. It is understood that the openwork, each bottom of which is formed by the flat substrate, could serve as molds for galvanic growth and whose wall shape makes it possible to obtain a three-dimensional watch component of predetermined geometry.Step a could also be obtained by three-dimensional printing (direct additive manufacturing of the support 10) or by laser radiation lithography (high precision of the geometry of the support 10 without the use of a mask).

[0057] Even more effectively, said at least one base layer 11 is based on a metallic material whose equilibrium constant with respect to cyanide ions is less than or equal to 3. Such a metallic material may be based on chromium and / or aluminum and / or iron and / or tin and / or titanium. It is therefore understood that each metallic material may be pure or in the form of the main element of an alloy of at least one other metallic material from the list and / or at least one other element not belonging to the list.

[0058] Step b is preferably obtained by physical vapor deposition. Of course, other deposition methods can be envisaged without departing from the scope of the invention. In the example illustrated in FIG. 4, said at least one base layer 11 is deposited only against the replication form 10a of the support 10. The thin deposition of said at least one base layer 11 makes it possible to faithfully reproduce the replication form 10a and to adhere to the support 10.

[0059] Insofar as the material of said at least one base layer 11 whose equilibrium constant pKf with respect to the cyanide ions is less than or equal to 5 (or 3) has the capacity to be very quickly passivated such as aluminum, titanium or chromium, preferably, step b comprises the deposition of a second base layer 11, called the upper layer, above said first contact layer 11, formed on the support 10. Indeed, depending on the speed of passivation of said first contact layer 11, it may be difficult to initiate step c to form said at least one main layer 12 by electroplating.In this preferred variant, said at least one base layer 11 therefore comprises at least two base layers 11, that is to say a first contact layer 11 formed on the support 10 based on a metallic material whose equilibrium constant with respect to the cyanide ions is less than or equal to 5 (or 3) and a second upper layer 11 formed above the first contact layer 11 which is more stable than the first contact layer 11 to guarantee the implementation of step c.

[0060] This second upper layer 11, which is preferably a thin deposit, may comprise copper and / or a noble metal such as gold or silver, and it may for example be deposited by physical vapor deposition just after one or more first base layers 11 such as the first contact layer 11. In this case, said at least one main layer 12 will be deposited during step c from the second upper layer 11 without encountering any adhesion problem. Of course, several second upper layers 11 may also be deposited between said at least one first contact layer 11 and said at least one main layer 12.

[0061] Step c is intended to form at least one main layer 12 by electroplating using a galvanic bath comprising cyanide ions in order to form the solid metal part of the watch component 1. In the example illustrated in FIG. 5, said at least one main layer 12 is deposited from said at least one base layer 11 until it covers an upper part of the support 10. The very thick deposition of said at least one main layer 12 makes it possible to adhere to said at least one base layer 11 and to thicken the latter so as to improve the mechanical strength of the watch component 1. Said at least one main layer 12 may be based on a noble material (precious metal such as pure gold or silver (or one of their alloys)) or less noble material (more conventional metal such as pure copper or nickel (or one of their alloys)) depending on the desired rendering or the final visibility of said at least one main layer 12.

[0062] According to a first variant of the first embodiment, the method according to the invention can stop at the end of step c and form a composite watch component 1 comprising the support 10 made of polymer material, said at least one base layer 11 and said at least one main layer 12. Of course, a finishing step (for example machining and / or polishing) and / or protection (for example varnishing, PVD or ALD) can be provided to make the watch component 1 suitable for being mounted in the timepiece 2 (aesthetics, geometry, etc.).

[0063] According to a second variant of the first embodiment, at the end of step c, the method according to the invention can continue and stop with step e, as illustrated in the example of FIG. 6, intended to release the watch component 1 from the support 10 in order to form the watch component 1 only from said at least one base layer 11 and said at least one main layer 12. Step e can be obtained by selective or partially selective etching of said at least one base layer 11 or by dissolving the support 10 therefrom.

[0064] This step e can in particular be used for a mass replication process in which the support 10 made of polymer material is used to form several watch components 1 during the method according to the invention. Of course, a finishing step (for example machining and / or polishing) and / or protection (for example varnishing, PVD or ALD) can be provided to make the watch component 1 suitable for being mounted in the timepiece 2 (aesthetics, geometry, etc.).

[0065] According to a first variant of the second embodiment, after step c, the method continues and ends with step d intended to machine the watch component 1 in order to modify its shape by removing material. It is thus possible to form, as illustrated in the example of FIG. 7, a composite watch component 1 comprising the support 10 made of polymer material, said at least one base layer 11 and said at least one main layer 12.

[0066] Advantageously according to the invention, it is thus possible to work and / or decorate and / or remove any surplus of said at least one main layer 12 while the support 10 made of polymer material is still integral with said at least one base layer 11. Step d can, for example, make it possible to form at least one element 12a for fixing the watch component 1. By way of non-limiting example, step d could, for example, form feet of the watch component 1 forming a watch dial in order to fix the latter to a watch movement 3.

[0067] According to a second variant of the second embodiment, at the end of step d, the method according to the invention can continue and stop with step e, as illustrated in the example of FIG. 8, intended to release the watch component 1 from the support 10 in order to form the watch component 1 without this support 10 and, for example, only from said at least one base layer 11 and said at least one main layer 12. Step e can be obtained by selective or partially selective etching of said at least one base layer 11, the etching solution not reacting or reacting little with said at least one main layer 12. Alternatively, step e can be obtained by dissolving the support 10 therefrom.

[0068] This step e can in particular be used for a mass replication process in which the support 10 made of polymer material is used to form several watch components 1 at the same time during the method according to the invention. Of course, a finishing step (for example machining and / or polishing) and / or protection (for example varnishing, PVD or ALD) can be provided to make the watch component 1 suitable for being mounted in the timepiece 2 (aesthetics, geometry, etc.).

[0069] According to a third variant of the second embodiment, at the end of step e, the method according to the invention can continue and stop with step f (final step) intended to form at least one decorative layer 13 on at least a part of the watch component 1 (total covering in the example of FIG. 9) in order to modify the aesthetic appearance of the watch component 1. Typically, this makes it possible to form said at least one main layer 12 based on a less noble metallic material such as pure copper (or one of its alloys) and then to cover (for example by another electroplating) all or part of said at least one main layer 12 with at least one decorative layer 13 made of a more noble material such as based on a precious metal such as pure gold (or one of its alloys) in order to give a more high-end finish to the watch component 1.Of course, step f can be obtained by another type of deposition such as, for example, physical vapor deposition, chemical vapor deposition or autocatalytic deposition. Finally, as for the other variants, a finishing step (for example machining and / or polishing) and / or protection (for example varnishing, PVD or ALD) can be provided to make the watch component 1 suitable for being mounted in the timepiece 2 (aesthetics, geometry, etc.).

[0070] In this third variant of the second embodiment, if said at least one base layer 11 is based on a material having the capacity to be very quickly passivated such as aluminum, titanium, chromium, the adhesion on said at least one base layer 11 after release from the support 10 may be insufficient. Two ways are possible for implementing step f on the entirety of the watch component 1.

[0071] A first case may consist of depassivating said at least one base layer 11 and then depositing said at least one decorative layer 13 to carry out step f. The oxides present on the surface of said at least one base layer 11 forming the passivating layer may, upon contact with a reducing agent, be removed. This results in the elimination of the passivating oxide layer and allows the implementation of step f both on said at least one main layer 12 and on said at least one base layer 11. Alkali metals are very good candidates for the reduction of metal oxides. Lithium is the metal with the highest reduction capacity due to its low electronegativity. Examples of reducing agents include sodium hydride (NaH), lithium hydride (LiH), calcium dihydride (CaH2) and, more generally, any derivative containing metallic elements such as potassium, calcium, sodium, magnesium or barium.

[0072] A second case may consist of removing said at least one base layer 11. Indeed, if the depassivation remains too limited in time in contact with air, the oxide can be reformed instantly. In the case of repassivation that is too rapid for implementation of step f, the second possibility consists of completely and selectively removing the oxide and the metal from the base layer 11 and then depositing said at least one decorative layer 13 to carry out step f. This removal operation consists of using a chemical solution aimed either at solubilizing and complexing only the passivated metal, or creating an electrochemical cell to reduce said at least one base layer 11 at the surface.

[0073] For example, for chromium, removal using cerium ammonium citrate can be cited: 3 Ce(NH4)2(NO3)6+ Cr → 3 Cr(NO3)3+ 3 Ce(NH4)2(NO3)5(4)

[0074] This operation will selectively remove the chromium without altering the other coatings present on the surface of the watch component 1. In other words, the oxide and the chromium are removed at the same time without attacking the metal of said at least one main layer 12 of the watch component 1. It is then possible to implement step f as explained above.

[0075] The invention is not limited to the embodiments and variants presented and other embodiments and variants will become clear to those skilled in the art. Thus, the above embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the characteristics apply only to a single embodiment. Simple characteristics of different embodiments can also be combined and / or interchanged to provide other embodiments. Without being limiting, as visible in Figure 10 in dotted line, it may be envisaged to apply a step f of forming at least one decorative layer to the watch component 1 formed after step c, that is to say without necessarily having implemented the machining step d and / or the release step e.

[0076] Furthermore, the invention cannot be limited to the materials given as examples above. Thus, the invention could also be applied with a barrier layer such as a nickel-based layer (pure or alloy) between, for example, two layers whose intermetallics are very easy to form at room temperature. As a non-limiting example, copper diffuses very easily into gold. Such a barrier layer would therefore prevent the diffusion of copper into the gold on the watch component 1 by providing better visual stability over time. LIST OF REFERENCES

[0077] 1 watch component 2 timepiece 3 watch movement 8 replication tool 8a form to be replicated 10 polymer material support 10a replication form 11 base layer 12 main layer 12a fixing element 13 decoration layer

Claims

1. Method for manufacturing a watch component (1) comprising the following steps: a. providing a support (10) made of polymer material; b. forming at least one base layer (11) on at least a portion of the support (10) including a contact layer formed on the support (10), said contact layer being based on a metallic material whose equilibrium constant with respect to cyanide ions is less than or equal to 5; c. forming at least one main layer (12) above said at least one base layer (11) by electroplating using a galvanic bath comprising cyanide ions in order to form a watch component (1).

2. Method according to the preceding claim, in which step a comprises the following phases: i. providing a replication tool (8) partly comprising a geometry (8a) to be reproduced of the watch component (1); ii. at least partially covering the replication tool (8) with a polymer material in order to form a support (10) made of polymer material with a complementary geometry (10a) of the geometry (8a) to be reproduced of the watch component (1); iii. releasing the support (10) made of polymer material from the replication tool (8).

3. Method according to claim 1 or 2, in which said at least one base layer (11) is based on a metallic material whose equilibrium constant with respect to cyanide ions is less than or equal to 3.

4. Method according to any one of the preceding claims, wherein said at least one base layer (11) is based on chromium and / or aluminum and / or iron and / or tin and / or titanium.

5. A method according to any one of the preceding claims, wherein said at least one base layer (11) further comprises at least one second upper layer formed above said contact layer, said at least one second upper layer having a lower passivation capacity compared to each other base layer (11) in order to facilitate the initiation of step c.

6. Method according to any one of the preceding claims, wherein said at least one second upper layer (11) is based on copper and / or gold and / or silver.

7. Method according to any one of the preceding claims, in which step b is obtained by physical vapor deposition.

8. Method according to the preceding claim, in which, after step c, the method comprises the following step: d. machining the watch component (1) in order to modify its shape by removing material.

9. Method according to the preceding claim, in which step d makes it possible to form at least one element (12a) for fixing the watch component (1).

10. Method according to claim 8 or 9, wherein, after step d, the method comprises the following step: e. releasing the watch component (1) from the support (10) so that the watch component (1) comprises said at least one base layer (11) and said at least one main layer (12).

11. Method according to any one of claims 1 to 7, wherein, after step c, the method comprises the following step: e. releasing the watch component (1) from the support (10) so that the watch component (1) comprises said at least one base layer (11) and said at least one main layer (12).

12. Method according to any one of the preceding claims, in which the method comprises the following final step: f. forming at least one layer (13) of decoration on at least a portion of the watch component (1) in order to modify the aesthetic appearance of the watch component (1).

13. Method according to the preceding claim, in which said at least one decorative layer (13) is based on a precious metal.

14. Method according to claim 12 or 13, in which step f comprises a preliminary phase intended to depassivate said at least one base layer (11) followed by a phase of deposition by electroplating of said at least one decorative layer (13).

15. Method according to claim 12 or 13, in which step f comprises a preliminary phase intended to remove said at least one base layer (11) followed by a phase of electroplating deposition of said at least one decorative layer (13).