Method for manufacturing a timepiece dial

Abstract

The invention relates to a method for manufacturing a timepiece dial, comprising steps a: forming a substrate (10) made of a transparent material, b: depositing at least one base layer (20) onto at least part of the substrate (10), said at least one base layer (20) being partially perforated with openings (25) with predetermined cross sections allowing the openings (25) to be non-perceptible to the naked human eye, and c: depositing at least one working layer (30) onto said at least one base layer (20) without plugging the openings (25), in order to form a dial (9) with an improved aesthetic appearance while allowing transmission of electromagnetic radiation through its thickness.

Description

PROCESS FOR MANUFACTURING A WATCH DIAL TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a method of manufacturing a dial intended to be implanted in front of at least one photovoltaic cell in order to allow all or part of the ambient light to pass through and in particular such a dial implanted in a timepiece. TECHNICAL BACKGROUND OF THE INVENTION

[0002] It is known to form timepieces with a watch movement powered by a photovoltaic cell. This type of timepiece is economically advantageous because it avoids too frequent maintenance due, for example, to changing the battery. However, it requires the photovoltaic cell to be installed as close as possible to a dial that must allow electromagnetic radiation to pass through. The need to transmit electromagnetic radiation makes it difficult to integrate photovoltaic cell technology into luxury watchmaking where the aesthetic requirements of dials are important. Indeed, fine watchmaking requires opaline finishes using precious metals with a high reflection coefficient and which can be decorated with guilloche patterns that are harmful to the transmission of electromagnetic radiation.

[0003] Document JP H11-326549 describes an example of a manufacturing process for a watch dial allowing the transmission of electromagnetic radiation. However, the manufacturing process described in this document is complicated, long and expensive to implement. Thus, it uses separate steps of preparing parts which are assembled, in a final step, by gluing which do not allow in particular to meet the aesthetic requirements of luxury watch dials, nor to guarantee the shape of the dials or to be compatible with traditional finishing steps. More specifically, an openwork metal layer is obtained separately from a mold formed by a steel substrate and pillars formed by photolithography. Several metal layers are deposited by electroplating between the pillars of the mold (the pillars forming openwork) then the metal assembly is delaminated from the mold.Exposure to ultraviolet radiation from photolithography involves a dimensional variation depending on the thickness, which makes the resolution very variable on three-dimensional decorations such as the pillars used. Consequently, in addition to the bonding steps, the separate manufacturing step of the perforated metal layer, in particular by its delamination, induces a high risk of deformation and / or deterioration which does not allow, in particular, to meet the aesthetic requirements of. luxury watch dials, nor to guarantee the shape of the dials or to be compatible with traditional finishing steps. For these reasons, the dial produced by this document remains relatively unattractive and incompatible with certain traditional finishing steps such as guilloché or certain three-dimensional decorations. SUMMARY OF THE INVENTION

[0004] The aim of the invention is to propose a simple and economical dial manufacturing method in order to obtain a dial without any real aesthetic limitation, that is to say in particular one which can always accommodate indexes and / or guilloches, allowing the transmission through its thickness of electromagnetic radiation without marks or the photovoltaic cell being perceptible to a naked human eye on the dial to allow the latter to be compatible with the aesthetic requirements of luxury watchmaking such as an opaline guilloche finish.

[0005] To this end, the invention relates to a method for manufacturing a watch dial comprising the following steps: a. providing a substrate made of transparent material; b. depositing at least one base layer on at least part of the substrate, said at least one base layer being partially perforated with openings according to predetermined sections allowing the openings to be invisible to the naked human eye; c. depositing at least one working layer on said at least one base layer without blocking the openings in order to form a dial with an improved aesthetic appearance while allowing the transmission of electromagnetic radiation through its thickness.

[0006] Advantageously according to the invention, the manufacturing method adapts to the surface of the substrate and is therefore usable not only on flat or domed dials but also on dials with three-dimensional decorations. Thus, the stacking of the layers with the openings is sufficiently robust to withstand traditional finishing processes such as sunburst, spraying and shading. The method also allows the decoration of the dial to be available in a multitude of finishes from the same substrate formation step a (using for example the same mold), which makes it very economical. The formation of the base layer with openings beforehand allows, once carried out, the use of traditional electrolytes and manual finishing operations essential for obtaining the color and surface condition characteristic of luxurious opaline dials.The dial resulting from this manufacturing process allows sufficient transmission of light to a photovoltaic cell while allowing the latter to be masked, i.e. making it invisible to the naked human eye. It is therefore possible to opt for. a photovoltaic cell with high yields while having high aesthetic requirements for the dial and very affordable production costs. In addition, the process advantageously makes it possible to use a substrate that is compatible with the market trend towards creating thin timepieces.

[0007] The invention may also include one or more of the following optional features, taken alone or in combination.

[0008] The transparent substrate material may be polymer-based to enable very low and very rapid production costs of step a using, for example, injection into a mold. For example, the transparent substrate material may be polyamide-based.

[0009] According to an alternative, step b may comprise a first phase intended to deposit said at least one base layer on the substrate then a second phase intended to partially openwork said at least one base layer according to the predetermined sections, or a single phase intended to selectively deposit said at least one base layer on the substrate in order to form said at least one base layer directly with the openings according to the predetermined sections during its deposition. For both possibilities of the alternative, step b is simple and precise in particular as regards the dimensions of the openings, the predetermined sections of which preferably have dimensions less than 35 μm, in order to be imperceptible to a naked human eye, in particular because, thanks to step c, it is not necessary for the base layer to be very thick.Furthermore, the openings made during step b can be, advantageously according to the invention, used to form a decoration. In the case of the first possibility of the alternative, it is understood that a small thickness is therefore to be perforated which allows a very low production cost due to the small volume of material to be removed and therefore the very short time necessary for perforating. The perforating phase is preferably obtained by laser ablation such as using a nanolaser. Preferably according to the invention, step b is implemented by physical vapor deposition to form an electrically conductive metal base layer.

[0010] Step c may be implemented by electroplating to form at least one metallic working layer preferably thicker than the base layer. Thus, at the end of step c, a finishing operation may be implemented to form a decoration on the working layer such as sunburst or satin finishing without risking damage to the dial. Electroplating step c may use a galvanic bath comprising leveling agents in order to limit the clogging of the openings.

[0011] The method may comprise, after step c, a step d intended to form at least one finishing layer on the working layer(s) without blocking the openings. This finishing step can be useful for giving a precise final shade to the dial. Step d can be implemented by electroplating to form a metallic finishing layer such as one based on a precious metal. Electroplating step d can use a galvanic bath including leveling agents to limit the clogging of the openings. Thus, at the end of step d, a finishing operation can be implemented to form a decoration on the finishing layer such as sunburst or satin finish without risking damage to the dial.

[0012] Finally, the method may include the final step e intended to form at least one protective layer and / or a layer of varnish on the upper surface of the dial in order to protect the appearance of the latter such as a high-end opaline finish. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] 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 according to the invention; Figure 2 is an exploded view of another example of a timepiece according to the invention; Figures 3 to 8 are examples of steps of the manufacturing method according to several variants of the invention; Figure 9 is a schematic sectional representation of an example of a dial obtained by the method of the invention; Figure 10 is a functional diagram of the method of the invention according to several embodiments and several variants; Figures 11 to 14 are successive steps according to a variant of the manufacturing method in which attachment sites are formed to promote the subsequent adhesion of a deposit of material;Figure 15 is an example of a halftone decoration formed by openings in the base layer obtained by a variant of step b of the method according to the invention.; DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT OF THE INVENTION

[0014] 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.

[0015] 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 in relation to the direction in which the figures are represented. The term "horizontal" is therefore understood as a direction parallel to the main section of the watch movement plate and the term "vertical" is understood as a direction perpendicular to the horizontal direction and parallel to the thickness of the watch movement plate.

[0016] By "timepiece 2" we mean all types of instruments for measuring or counting time such as clocks, small clocks, watches, etc.

[0017] By “watch movement 3” is meant all types of mechanism capable of counting time and powered by electrical energy comprising for example a battery 7, an autoquartz type system (oscillating mass charging a capacitor or a battery 7) and / or a photovoltaic cell 1.

[0018] By "transparent material" is meant a material which transmits at least 50% of the incident electromagnetic radiation (typically ambient light where dial 9 is), in particular for the wavelengths usable by a photovoltaic cell 1 generally between 400 nm and 1100 nm.

[0019] By "electrically conductive" is meant a material having, preferably, an electrical conductivity o at least equal to 1 MS m -1 or an electrical resistivity p at most equal to 1 pQ m at a temperature of 300 K.

[0020] By "not perceptible to a human eye" is meant a detail of dial 9 that is not observable to the naked eye, i.e. without magnifying optics, due to dimensions smaller than the resolving power of the observer's eye. It is generally accepted that on average, a human eye is capable of separating (distinguishing) details of 0.5 mm at a distance of 1 m. In the case of an application to a dial 9, by remaining within dimensions smaller than 35 μm, holes in dial 9 will remain unperceptible to a human eye. It is therefore understood that these dimensions smaller than 35 μm are obtained in step b and theoretically further reduced on the final dial 9 depending on the layers formed over the base layer(s).

[0021] Visible wavelengths mean the range of electromagnetic radiation wavelengths that can be observed by the naked human eye, i.e. without any detection aids. On average, the human eye perceives a light spectrum of electromagnetic radiation with wavelengths in a vacuum between 380 nm and 780 nm.

[0022] "Based on" means a material or alloy constituting at least 50% by total mass or weight of a given element. In the following, unless otherwise indicated, all percentages (%) indicated are percentages by total mass or weight.

[0023] The invention preferably finds its application in timepieces 2 whose watch movement 3 comprises at least one photovoltaic cell 1. The watch movement 3 is preferably of the quartz type. It uses in particular a quartz tuning fork resonator 4 as a time base and at least one stepping motor (not visible) which are configured using a control unit to move by means of a gear train 5 at least one time display 6 (an hour hand 6a and a minute hand 6b in the example of FIG. 1) in a manner known per se.

[0024] In the preferred application of the invention, the watch movement 3 does not include a battery as a source of electrical energy but a photovoltaic cell 1 - rechargeable battery 7 assembly managed by the control unit which allows a lifetime greater than that of a battery. More precisely, the watch movement 3 is supplied with electrical energy by the photovoltaic cell 1 - rechargeable battery 7 assembly. The photovoltaic cell 1 is a transducer of electromagnetic radiation (such as solar radiation) into electrical energy in a known manner. The battery 7 is used to store electrical energy and compensate for variations in energy harvested by the photovoltaic cell 1 (in particular in the event of an absence of radiation or insufficient reception of radiation to provide the electrical energy necessary for the operation of the watch movement 3).The control unit of the watch movement 3 therefore also manages the electrical energy produced by the photovoltaic cell 1 to power the components of the watch movement 3 and / or recharge the battery 7. The battery 7 can therefore have a lower capacity than usual batteries and is preferably based on lithium technology.

[0025] This architecture is economically advantageous because it avoids frequent maintenance of the watch due, for example, to changing the battery, and long-term storage of timepieces 2 is also less restrictive. However, it requires the installation of the photovoltaic cell 1 in place of the dial or as close as possible to a dial 9 that allows electromagnetic radiation to pass through. In the latter case, the photovoltaic cell 1 can be attached to the dial 9 itself or to the watch movement 3. The need to allow electromagnetic radiation to pass through makes it difficult to integrate the technology into luxury watchmaking where the aesthetic requirements of dials 9 are important. Indeed, fine watchmaking requires the use of precious materials and guilloche patterns.

[0026] For example, a good portion of high-end watchmaking pieces include 9 dials with an opaline silver finish that gives a velvety texture. This traditional finish is very difficult to reconcile with an application photovoltaic due to the physicochemical properties of silver. Its high reflectivity is more suitable for the manufacture of light reflectors or mirrors than for the manufacture of a light-transmitting layer. Silver is also very susceptible to tarnishing and sulfurization and therefore must be protected to maintain its attractive appearance.

[0027] The invention therefore aims to propose a method 100 for manufacturing a dial 9 simple and economical in order to obtain a dial 9 without any real aesthetic limitation, that is to say in particular always being able to receive indexes and / or guilloches, authorizing the transmission through its thickness of electromagnetic radiation without marks or the photovoltaic cell being perceptible by a human eye on the dial 9 to allow the latter to be compatible with the aesthetic requirements of luxury watchmaking such as an opaline guilloche finish.

[0028] In the example illustrated in Figure 10, the manufacturing method 100 comprises a first step 50 intended to provide a substrate 10 made of a material transparent to the wavelengths usable by a photovoltaic cell 1 generally between 400 nm and 1100 nm. The transparent material of the substrate 10 is preferably polymer-based, which makes it inexpensive while offering good mechanical strength and great freedom of shape. Of course, other types of substrates 10 transparencies are possible such as glass-based or ceramic-based.

[0029] In order to follow the market trend to create thin timepieces 2, it may be interesting to reduce the thickness, that is to say the dimension along the vertical axis, of the substrate 10. Thus, preferably the minimum thickness of the substrate 10 is 400 μm. This limit is preferred because, below this, shrinkage phenomena may become significant and a significant risk of defects for any subsequent deposit against the substrate 10 may occur.

[0030] According to a variant of the first step 50, the substrate 10 is formed from a styrenic polymer. A first example is methyl methacrylate acrylonitrile butadiene styrene (M-ABS), which is well suited for photovoltaic applications. M-ABS has good adhesion properties with metal films and is highly transparent (typically 88%-94% for visible wavelengths) due to the incorporation of the rubbery phase into a methyl methacrylate (MMA) - styrene - acrylonitrile (SAN) phase. More precisely, the MMA adds the transparent component to the SAN phase.

[0031] A second example is acrylonitrile butadiene styrene (ABS), i.e. the first example without MMA phase. In order to obtain better mechanical properties for the substrate 10, it is also possible to use a filled ABS, for example with glass fibers.

[0032] Of course, other transparent polymer variants are also possible, such as polyamide (PA), polycarbonate (PC), cycloolefin (CO) or polymethyl methacrylate (PMMA).

[0033] When the substrate 10 is preferably polymer-based, the first step 50 can be obtained using a conventional molding phase such as, for example, using an injection into a mold giving the rough shape of the future dial 9. Indeed, a molding phase is fast, precise and economical. Of course, other techniques can be implemented to carry out the first step 50 such as, for example, additive manufacturing.

[0034] The first step 50 can also be used to produce at least one form of finishing on the blank of the future dial 9. Thus, for example, the mold could include a relief intended to form a decoration (guilloche, sunburst, Geneva stripes, Paris nails, etc.) on the face opposite that facing the photovoltaic cell 1 of the blank of the future dial 9. However, this solution is not preferred because these finishes obtained on the blank would be partially flattened during the following steps of deposition on the substrate 10 of the method and the dial 9 obtained would lose part of its transmission capacity. For these reasons, preferably, the upper surface of the substrate 10 obtained by the first step 50 is smooth or includes a slight roughness to promote the adhesion of a subsequent deposit on top.

[0035] In a first embodiment, the manufacturing method 100 comprises, after the first step 50, a second step 60 intended to form at least one base layer 20, called the bonding layer, on at least a portion of the substrate 10 obtained during the first step 50. Each base layer 20 is relatively thin and preferably comprises a single layer of a material. However, it is perfectly conceivable that several base layers 20 are formed based on materials, identical or different, on the substrate 10. The material of the base layer(s) 20 is preferably metallic such as based on nickel, copper, gold or silver, but other materials such as an alloy of at least two of the previously mentioned metals can also be used.Preferably, the base layer 20 or all of the base layers 20 has a thickness, i.e. the dimension along the vertical axis, of between 10 nm and 1 pm, such as, for example, being equal to 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm or 1 pm.

[0036] The second step 60 can be carried out by different methods. When the substrate 10 is polymer-based, the metallization required for the second step 60 can be made difficult for reasons of adhesion and because of chemical incompatibilities between the different types of materials. For example, baths The electrochemical processes traditionally used in watchmaking are based on cyanide compounds. They are generally incompatible with metal-polymer interfaces, in particular because cyanides (CN) very strongly complex noble metals. This phenomenon can lead to delamination at a metal-polymer interface which is further weakened if the base layer 20 is perforated, i.e. does not completely cover the upper surface of the substrate 10. Indeed, such perforations considerably increase the contact areas between the cyanides and the metal-polymer interface. It is therefore important that the formation of the base layer 20 makes it possible to avoid subsequent delamination of the interface between the substrate 10 and the base layer 20 during any subsequent galvanic treatments and during treatments of the surface of the dial 9.

[0037] According to a first variant of the second step 60, the base layer 20 is formed on the substrate 10 by physical vapor deposition (also known by the English abbreviation PVD). In this variant, the base layer 20 may preferably comprise a metal layer of chromium, silver, nickel, aluminum, titanium, tin, iron, copper or gold. However, other types of metals such as aluminum and titanium may also be used. Such metallization of the substrate 10 by physical vapor deposition is directional and therefore makes it possible to form the base layer 20 only on the upper surface of the substrate 10, which makes it possible to maintain the light transmission coefficient of the dial 9 without deposition on the rest of the substrate 10, which reduces the processing time.

[0038] According to a preferred possibility of implementing the second step 60, the deposition of a chromium layer by physical vapor deposition as a base layer 20 or as a first base layer 20 is carried out. A chromium layer indeed has good adhesion with a substrate 10 based on M-ABS but also with other polymers in general. The first chromium-based base layer 20 may, for example, have a thickness of between 100 nm and 130 nm obtained by physical vapor deposition on a substrate 10 based on M-ABS. However, it may be difficult to start a galvanic deposition on the chromium because of its reactivity (passivation) with the ambient air.

[0039] According to a variant of the preferred possibility of implementing the invention, there is therefore provided, over the first base layer 20 based on chromium, a second base layer 20, for example by physical vapor deposition, based on silver and / or based on gold in order to ensure a homogeneous deposition for the rest of the process 100 by limiting the oxidation of the chromium on the surface to guarantee good conductivity of the set of base layers 20 which is compatible with the use of standard finishing galvanic baths. The variant of the preferred possibility of implementing implementation of the invention of the second step 60 therefore makes it possible to obtain a dial 9 with a coloring very close to the target thanks to the good adhesion of the set of base layers 20 even if the substrate 10 is polymer-based. The second silver-based base layer 20 may have a thickness of between 100 nm and 130 nm obtained by physical vapor deposition on the first chromium-based base layer 20.

[0040] Of course, this combination of first and second base layers 20 could be replaced by a base layer 20 comprising a composition gradient ranging from 100% of a first material to 100% of a second material. As a non-limiting example, a base layer 20 with a thickness of 200 nm could comprise a composition gradient ranging from 100% chromium against the substrate 10 to 100% silver on the surface against which the working layer 30 will be deposited.

[0041] If the metallic material chosen for the second step 60 does not have sufficiently good adhesion with the substrate 10, any subsequent electroplating step may use a bath with a non-cyanide electrolyte, for example described below, and / or an increase in surface adhesion (application of a primer or promoter) in order to improve the implementation of the second step 60.

[0042] According to a second variant of the second step 60, the base layer 20 is formed on the substrate 10 by autocatalytic deposition (known by the English term “electroless plating”) after having created and activated attachment sites 10B on at least part of the surface of the substrate 10.

[0043] According to one possibility of this second variant of the second step 60 illustrated in the example of Figures 11 to 13, the polymer-based material of the substrate 10 is chosen to comprise a butadiene phase 10A, such as ABS or M-ABS, so that attachment sites 10B are obtained by oxidation of the butadiene phase 10A of the substrate 10. In a first phase illustrated in the example of Figure 11, the substrate 10 is formed with the butadiene phase 10A. In a second phase illustrated in Figure 12, the butadiene phase 10A is transformed by oxidation at the external surface of the substrate 10 in order to create attachment sites 10B (recessed parts). This oxidation takes place preferably with the help of permanganate ions (MnO4-) which are anions of permanganic acid salts, consisting of four oxygen atoms around a manganese atom.Optionally, after this oxidation phase, the surface of the substrate 10 can be treated in a weak acidic aqueous solution such as sodium bisulfite to remove the oxidation product.

[0044] Of course, the second phase of creation of 10B attachment sites can be achieved by other types of compounds such as, for example, a hexavalent chromium (chromium VI) but this compound is generally less favored because it is classified as harmful by European legislation REACH for chemical substances and RoHS for hazardous substances in electrical and electronic equipment.

[0045] In a third phase, the attachment sites 10B are activated by treating the surface of the substrate 10 with a metal colloid or a metal composition. In the example illustrated in FIG. 13, metal particles 10C are immobilized (adsorbed) at the attachment areas 10B in order to make the polymer substrate 10 more compatible for receiving electroless deposition. The metal of the metal colloid or the metal composition preferably comes from the group comprising the metals of transition group I of the periodic table of elements or of transition group VIII. Preferably, the metal in question is palladium, platinum, iridium, rhodium, gold or silver or a mixture of at least two of these metals. A preferred possibility for implementing the third phase uses palladium as the metal of the metal colloid.

[0046] The metal colloid may also be stabilized by a protective colloid, which may be metallic, organic, or of another form. For example, a metal protective colloid may include tin ions (Sn 2+ ), polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP). In a variant of the preferred embodiment of the third phase, the solution of the metal colloid used for activation is therefore an activator solution with a palladium / tin colloid. This colloidal solution is obtained from a palladium salt (palladium II), a tin salt (tin II) and an inorganic acid. A preferred palladium salt (palladium II) is palladium chloride. A preferred tin salt (tin II) is tin chloride. The inorganic acid can consist of hydrochloric acid (HCl) or sulfuric acid (H2SO4) with preference for the former.

[0047] The temperature of the colloidal solution during the second activation phase may be between 20°C and 50°C and preferably between 35°C and 45°C, i.e. for example equal to 20°C, 25°C, 30°C, 35°C, 40°C, 45°C or 50°C. The treatment time with the activator solution may be from 0.5 min to 10 min, preferably from 2 min to 5 min and even more preferably from 3 min to 5 min, i.e. for example equal to 0.5 min, 1 min, 0.5 min, 1 min, 1.5 min, 2 min, 2.5 min, 3 min, 3.5 min, 4 min, 4.5 min, 5 min, 5.5 min, 6 min, 6.5 min, 7 min, 7.5 min, 8 min, 8.5 min, 9 min, 9.5 min or 10 min.

[0048] The colloidal solution is formed by reduction of palladium chloride to palladium using tin chloride (tin II). The conversion of palladium chloride to colloid is complete. Therefore, the colloidal solution no longer contains palladium chloride. The concentration of palladium (Pd 2+ ) can be understood between 5 mgT 1 and 100 mgT 1 , preferably 20 mgT 1 at 50 mgT 1 and even more preferably 30 mgT 1 at 45 mgT 1 , that is to say for example equal to 5 mgT 1 , 10 mgT 1 , 15 mgT 1 , 20 mgT 1 , 25 mgT 1 , 30 mgT 1 , 35 mgT 1 , 40 mgT 1 , 45 mgT 1 , 50 mgT 1 , 55 mgT 1 , 60 mgT 1 , 65 mgT 1 , 70 mgT 1 , 75 mgT 1 , 80 mgT 1 , 85 mgT 1 , 90 mgT 1 , 95 mgT 1 or 100 mgT 1 The concentration of tin chloride (Sn2+) can be between 0.5 gT 1 and 10 g. I' 1 , preferably 1 gT 1 at 5 gT 1 and even more preferably 2 gT 1 at 4 gT 1 , that is to say for example equal to 0.5 gT 1 , 1 g-l' 1 , 1.5 gT 1 , 2 g-l'1 , 2.5 g-l' 1 , 3 g-l' 1 , 3.5 g-l' 1 , 4 g-l' 1 , 4.5 g-l' 1 , 5 g-l' 1 , 5.5 g-l' 1 , 6 g-l' 1 , 6.5 g-l' 1 , 7 g-l' 1 , 7.5 gT 1 , 8 g-l' 1 , 8.5 gT 1 , 9 gl -1 , 9.5 gT 1 or 10 gT 1 . The concentration of hydrochloric acid (HCl) can be between 100 mIT 1 and 300 mIT 1 (of a 37% by weight solution of HCl), for example equal to 100 ml 1 , 125 mi l' 1 , 150 mi l' 1 , 175 mi l' 1 , 200 mIT 1 , 225 mIT 1 , 250 mi l' 1 , 275 mIT 1 or 300 mi l' 1 A colloidal palladium / tin solution further includes tin ions (tin IV) which are formed by oxidation of tin ions (tin II).

[0049] As explained above, for the third activation step, instead of the metal colloid, a solution of a metal composition can be used for activation. This solution can comprise an acid and a metal salt. The metal in the metal salt consists of one or more of the metals from transition groups I and VIII of the periodic table of elements as for the metal colloid. The metal salt can be a palladium (palladium II) salt, preferably palladium chloride, palladium sulfate or palladium acetate, or a silver (silver II) salt, preferably silver acetate. The acid is preferably hydrochloric acid (HCl). Alternatively, it is also possible to use a metal complex, for example a salt of a palladium complex, such as a salt of a palladium-aminopyridine complex.

[0050] The metal compound in the third activation phase can have a metal concentration between 40 mgT 1 and 80 mgT 1 , that is to say for example equal to 40 mgT 1 , 45 mgT 1 , 50 mgT 1 , 55 mgT 1 , 60 mgT 1 , 65 mgT 1 , 70 mgT 1 , 75 mgT 1 or 80 mgT 1 The solution of the metal compound may be used at a temperature between 25°C and 70°C and preferably at 25°C, i.e. for example equal to 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C or 70°C. The treatment time with the solution of a metal compound may be from 0.5 min to 10 min, preferably from 2 min to 6 min and even more preferably from 3 min to 5 min, i.e. for example equal to 0.5 min, 1 min, 0.5 min, 1 min, 1.5 min, 2 min, 2.5 min, 3 min, 3.5 min, 4 min, 4.5 min, 5 min, 5.5 min, 6 mins, 6.5 mins, 7 mins, 7.5 mins, 8 mins, 8.5 mins, 9 mins, 9.5 mins or 10 mins.

[0051] After the third phase of activating the attachment sites 10B on the substrate 10, a fourth phase intended to form the base layer 20 on the substrate 10 can be carried out by conventional autocatalytic deposition (known as “electroless plating”) as illustrated in the example of FIG. 14. Preferably, the base layer 20 according to this second variant of the second step 60 is based on nickel and / or copper. Of course, other types of metals compatible with autocatalytic deposition can also be used.

[0052] Unlike the first embodiment variant of the second step 60, according to the second variant of the second step 60, the formation of the base layer 20 may be selective or not, that is to say may only partially coat the substrate 10 or completely coat it. In the latter case, the substrate 10 is entirely metallized by the base layer(s) 20, then resulting in a dial blank 9 with a core preferably based on polymer which can replace a conventional brass dial blank.

[0053] In the first case, the selective formation of the base layer(s) 20 according to the second variant of the second step 60 can be configured to metallize a single face of the substrate 10 as for the first variant. The selectivity can be achieved by selective masking either in the second phase of creation of the attachment sites 10B, or in the third phase of activation of these attachment sites 10B, or in the fourth phase of catalytic deposition.Another solution for providing selectivity of the second variant of the second step 60 may be to adapt the first step 50 of the method 100 by manufacturing the polymer-based substrate 10 using bi-injection molding according to which a first type of polymer with a butadiene phase (such as ABS) is located on the upper surface of the substrate 10 and another type of polymer without this phase (such as a PC) is located on the other faces of the substrate so that attachment sites are not created on these other faces.

[0054] According to a third variant of the second step 60, the base layer 20 is formed on the substrate 10 by atomic layer deposition (known by the English terms “Atomic Layer Deposition” or ALD) and preferably by plasma-enhanced atomic layer deposition (known by the English terms “Plasma Enhanced Atomic Layer Deposition” or PEALD). ALD is a method of depositing layers at the atomic scale allowing deposits of very uniform thickness which consist of exposing a surface successively to different chemical precursors in order to obtain ultra-thin layers of metallic compounds, oxides or other materials. The ALD technology is based on self-saturated surface reactions which take place sequentially allowing controlled growth. In general, an ALD cycle comprises at least two injections of precursors, these injections being separated by a purge step serving to remove the precursor and excess reaction products before introducing the other precursor. Advantageously, ALD technology makes it possible to deposit layers on a surface having a very high aspect ratio, because the reaction takes place on a monolayer of precursor gases adsorbed directly on the surface. In this case, the base layer(s) 20 may comprise an electrically conductive material such as a metal such as platinum, palladium, chromium, silver or an alloy of these metals.

[0055] Generally, the above three variants of the second step 60 are not exhaustive. Thus, the base layer(s) 20 may also be formed by other techniques such as electroless chemical spray deposition or dipping.

[0056] After the second step 60, the method 100, according to the first embodiment, comprises a third step 70 intended to partially perforate the base layer(s) 20 with openings 25 according to predetermined sections. As explained above, in the case of an application to a dial 9, the predetermined sections are provided in dimensions less than 35 μm along the entire thickness of the base layer(s) 20 allowing the openings 25 to be invisible to a naked human eye. This is why; the third step 70 is sometimes referred to subsequently as the step intended to micro-perforate the base layer(s) 20. These micro-perforations or openings 25 allow the incident light to pass through the base layer(s) 20 to be transmitted into the substrate 10. Preferably, the openings 25 allow between 8% and 25% of the incident light on the dial 9 to be transmitted to at least one photovoltaic cell 1 located under the substrate 10.

[0057] Of course, the density (ratio between the surface area of ​​the predetermined sections and the total upper surface area of ​​the dial 9) and the distribution (distribution of the predetermined sections over the total upper surface area of ​​the dial 9) of the openings 25 influences the transmission of the incident light through the dial 9. Thus, the greater the density of the openings 25, the higher the light transmission will be and the more homogeneous the distribution of the openings 25 will be, the more evenly the light distribution on the surface of the photovoltaic cell 1 will be. Furthermore, each micro-perforation step 70 must be precisely controlled in section (or in diameter) and in position to obtain a clean aesthetic.It is also understood that the dimensions of the openings 25 are adapted so that they are not blocked at the end of the execution of the method according to the invention, that is to say that all or part of the through openings 25 remain at the end of the execution of the method according to the invention. According to one example, the openings 25 have a circular section with a diameter of between 20 μm and 30 μm, such as for example equal to 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm. 26 pm, 27 pm, 28 pm, 29 pm and 30 pm. Furthermore, by way of non-limiting example, a uniform spacing, i.e. a center-to-center distance between each opening 25, may be between 30 pm and 70 pm, such as for example equal to 30 pm, 35 pm, 40 pm, 45 pm, 50 pm, 55 pm, 60 pm, 65 pm and 70 pm, with a width of material always being present between the openings 25 and preferably at least equal to 3 pm.

[0058] According to a variant of the micro-perforation step 70, a variation of the sections of the openings 25 can be executed in halftone (known as "halftone") in order to give an apparent variation in the depth of color of the dial 9. More precisely, as visible in the example of FIG. 15, an increase in the sections of the openings 25 can be provided in the direction F (magnified view on the left of FIG. 15) such that the naked human eye does not discern these points but integrates them to give an illusion of several levels of brightness of a color (non-magnified view on the right of FIG. 15). Thus, the halftone micro-perforation step 70 can be used in order to limit or adapt the visual impact of the openings 25. For example, the openings 25 can be located in order to form a design or pattern on the dial 9 in variation of color while maintaining the transmission through the dial 9.

[0059] According to another variant of the micro-perforation step 70, the openings 25 can be used to simulate a decoration such as a guilloche or satin finish (streaks substantially parallel to each other) or sunburst (streaks converging in a single center which is visible or not) usually obtained using a brush and / or an abrasive. By configuring the micro-perforation step 70 (section, density, distribution, etc. in the upper plane of the dial 9), these decorations or guilloche can be obtained or at least visually reinforced, while contributing to the transmission through the dial 9.

[0060] The micro-perforation step 70 can be carried out by different methods such as lithography or chemical etching techniques. Preferably, it is carried out by laser ablation, i.e., localized removal by sublimation of material by laser radiation. According to a preferred variant, the laser ablation uses a nanolaser, i.e., with a pulse duration generally of the order of nanoseconds (for example, from 0.1 ns to 100 ns). The pulse repetition frequency of the laser can be 3.3 kHz with a power that can vary according to the desired diameter of the openings 25. Indeed, the use of a nanolaser makes it possible to control the cycle time to limit manufacturing costs, in particular by using affordable laser equipment. Of course, the use of a more expensive laser source such as a femtolaser or a picolaser can also be used.

[0061] Of course, when the lower surface of the substrate 10 also comprises the base layer(s) 20, the micro-perforation step 70 must be carried out on both faces in order to obtain the desired appearance of dial 9 while having good transmission of light through the dial 9 either by using internal reflections or by using a scanning scanner in order to align the openings 25 of each of the faces with each other. It is also understood that it is also possible to remove the base layer(s) 20 from the lower face of the substrate 10.

[0062] In a second embodiment of the method 100, instead of the successive steps 60 then 70, a single step 65 may be provided in order to form said at least one base layer 20 selectively on the substrate 10 to form said at least one base layer 20 directly with the openings 25 according to the predetermined sections allowing the openings 25 to be invisible to a naked human eye during the deposition of the base layer 20 according to the same technical effects and advantages of the successive steps 60 then 70 of the first embodiment.Such selective deposition may be carried out for example by area selective atomic layer deposition (AS-ALD) or by selective electroplating (electroforming) comprising for example a phase of lithography of a mold at at least one level (each protruding part will form the openings 25) followed by a phase of filling the mold by electroplating at least one material (the deposited material will form the base layer(s) 20).

[0063] After the formation of the base layer(s) 20 with the openings 25 according to step 65 (or according to steps 60 then 70), the method 100 advantageously comprises a step 80 intended to form at least one working layer 30 on the base layer(s) 20 without blocking the openings 25, i.e. deposited without completely covering the predetermined sections of the openings 25. As illustrated in the example of FIG. 5, the working layer 30 is preferably metallic and is thicker than the base layer(s) 20. Preferably, the working layer 30 has a thickness, i.e. the dimension along the vertical axis, of at least 1.5 μm, and even more preferably of at least 2 μm.

[0064] According to a preferred variant, said at least one working layer 30 of step 80 is deposited by electroplating. The working layer 30 may be based on different metals. It may in particular be based on copper, nickel, zinc, gold, silver, platinum, palladium, rhodium, ruthenium or alloys comprising one or more of these elements depending on whether a finishing layer 40 is provided or not as explained below. Indeed, if a finishing layer 40 is used, the working layer 30 may be of a less noble and less expensive material such as copper, nickel or zinc because it will be masked by the finishing layer 40. If no finishing layer 40 no finishing is used, the working layer 30 can preferably be based on precious metal giving maximum aesthetic elegance such as silver, gold, platinum, palladium, rhodium or ruthenium.

[0065] When the adhesion of the base layer(s) 20 to the substrate 10 is high, cyanide baths can be used for step 80. However, it is also possible to use cyanide-free electrolytes to avoid compromising the adhesion of the base layer(s) 20 to the polymer-based substrate 10. This option may be of interest, for example, when a gold-based base layer 20 is deposited by physical vapor deposition on a polymer-based substrate 10, because the adhesion of this base layer 20 may not be sufficient during subsequent electroplating steps due to delamination of the gold-polymer interface linked to the presence of cyanides.Cyanide-free baths (without complexed cyanide or without free cyanide) limit delamination problems at the interface between the polymer-based substrate 10 and the gold-based base layer(s) 20, but their use may make it more difficult to achieve a targeted opaline silver appearance.

[0066] Advantageously according to the invention, as illustrated in the example of Figure 6, manual finishing operations intended to form a decoration 31 such as guilloche, sunburst or satin finishing, which require not only good adhesion but also a minimum working thickness, can be carried out on the working layer 30 at the end of step 80. Indeed, these operations generate abrasion likely to strip the base layer(s) 20 if no working layer 30 were present according to the invention, that is to say would risk exposing the polymer-based substrate 10, forcing the dial blank to be scrapped. The presence of the thicker working layer 30 makes it possible to carry out such finishing operations on this working layer 30 without the risk of making the substrate 10, preferably polymer-based, visible to the naked eye.

[0067] After step 80, the method 100 according to the invention may comprise an optional step 90 intended to form a finishing layer 40 on each working layer 30 to adapt the desired finishing color. This finishing layer 40 may in particular comprise silver, the latter being often used for three-dimensional decorations and the traditional opaline finish which are typically desired for a dial 9 of a high-end watch. The finishing layer 40 provides the final color of the dial 9 and depending on the desired color this finishing layer 40 can for example have a thickness, that is to say the dimension along the vertical axis, between 100 nm and 1 pm such as, for example, being equal to 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm or 1 pm.

[0068] It is therefore understood that the working layer 30 and the finishing layer 40 may comprise the same material or different materials. For example, even if the working layer 30 comprises silver, it may still be advantageous to deposit a finishing layer 40 also comprising silver on this layer but by reducing, for example, the current density to improve the precision of the shade of the finishing layer 40 and, incidentally, that of the dial 9. Each layer which is formed above the base layer(s) 20, in particular the working layer 30 and any finishing layer 40, may be deposited by electroplating in the same bath or in different baths. However, other deposition techniques may also be used for the formation of the layers 30, 40.

[0069] In the example illustrated in Figure 7, during the formation of the working layer 30 and any finishing layer 40, the walls surrounding the openings 25 move closer together as the galvanic deposits are successively covered (the base layer(s) 20 is covered by the working layer 30, itself possibly covered by a finishing layer 40). This (these) covering(s) improve(s) the reflection against the walls surrounding the openings 25 and therefore the overall appearance of the dial 9, and it also offers better protection against corrosion of the openings 25.

[0070] Other layers may also be used, such as an anti-diffusion layer between the finishing layer 40 and the working layer 30 and / or between the working layer 30 and the base layer(s) 20. Such an anti-diffusion layer may, for example, be nickel-based. It is used to limit intermetallic migration phenomena between the layers and to stabilize the aesthetics of the dial 9.

[0071] When the layers 30, 40 are deposited by electroplating, the deposition parameters are configured to avoid blocking the openings 25, i.e. without completely covering the predetermined sections of the openings 25. In particular, a low current density is preferred and for this reason the current density is preferably at most 0.8 A dm 2 and even more preferably at most 0.6 A dm 2This allows less horizontal penetration into the openings 25. A longer immersion time in the galvanic bath imposed by a limited current density is also advantageous, for example a duration of at least 6 min and preferably at least 7 min.

[0072] Furthermore, this risk of blocking the openings 25 is especially significant for the working layer 30 in view of its significant thickness (compared to those in particular of the layers 20, 40) and the concentration of the electric field lines in the electrolyte bath at the periphery of the openings 25. For this reason, leveling agents may be present in the galvanic bath during the formation of the working layer 30. work. Leveling agents may include, for example, quaternary ammoniums (NR4 +) which are polyatomic cations of general structure N-R4, the R groups being able to be the same or different alkyl or aryl groups. Other possibilities for leveling agents are modified benzyl-phenyl, polyethyleneimine (PEI), 4-cyanopyridine (C6H4N2) and 3-diethylamino-7-(4-dimethylaminophenylazo)-5-phenylphenazinium chloride (C30H31CIN6). The use of a leveling agent can in particular slow down and limit the horizontal growth of the deposited layer which has a tendency to block the openings 25. Indeed, the positive zeta potential of the leveling agents, that is to say the electric charge on the surface of these particles, favors their adsorption on the periphery of the openings 25 which has a high negative charge density.The leveling agents can then slow down growth on the perimeter of the openings 25, which helps to avoid or at least limit clogging and to maintain a high transmission of light through the openings 25. It is therefore understood that the electrolytic bath(s) can comprise at least one leveling agent to electroplatingly form each working layer 30 and / or each additional layer such as the finishing layer 40 formed above the base layer(s) 20.

[0073] Between the deposition of the different layers 20, 30, 40 mentioned above, neutralization and rinsing steps can take place in order not to pollute the baths between them and to start a step with a clean and active surface. A degreasing step can also take place between some of the deposits, for example before the deposition of the finishing layer 40.

[0074] In view of the above, compared to a manufacturing method in which layers are stacked and then a perforation is made through all of the layers formed on the substrate, the inventors were able to observe that the invention has several advantages. First of all, pollution and diffusion in the layers 30, 40 are avoided by release of metals from the layers 20 or from the polymer of the substrate 10. The cycle time of step 70 for producing the openings 25 is much shorter or is even completely removed by the alternative step 65 directly forming the openings 25. More affordable laser equipment can be used for step 70. The appearance of the dial 9 in the areas of the openings 25 is significantly improved. The adhesion of the layers 20, 30, 40 to the substrate 10 is good. Finally, the dials 9 obtained are stable to aging.

[0075] In order to quantify the improvement in the appearance of the obtained dial 9, a test with a micro-perforation step was carried out on a 5 μm thick metal deposit using a femto-laser. It was observed that femto-laser drilling very significantly degrades the appearance of the upper layer which was in the silver-based test. Furthermore, it has also been observed that the openings have a non-constant section of generally conical appearance which deteriorates the visual appearance of the dial due to the deterioration of the material of the walls surrounding the openings. In addition, this conical shape also reduces the transmission of light through the openings (the section which decreases when approaching the substrate reduces the part of the incident light potentially transmitted).

[0076] Advantageously according to the invention, the layers 30, 40 described above are compatible with traditional methods of finishing and / or three-dimensional decorations of dial 9 such as for example sunburst, spraying (a variant of sandblasting increasing the roughness to give a diffuse reflection of the incident light), blurring (a variant of spraying giving a less pronounced roughness) or satin finishing. These finishes and decorations 31, 41 can be produced piece by piece after the formation of the layers 30, 40, which makes it possible to obtain several different types of dials 9 by using the same injection mold for the substrate 10.

[0077] According to a manufacturing example illustrated in Figure 7, a first finish 31 can be carried out on the working layer 30 before the formation of a finishing layer 40, the latter replicating a decorated shape 41 of the first finish 31 of the layer 30. Of course, a finish 41 can also be carried out only on the finishing layer 40 after its formation (no finish 31 on the layer 30) or a second finish to perfect the appearance of the decorated shape 41 initiated from the first finish 31 of the layer 30 can be carried out.

[0078] The manufacturing method 100 is, advantageously according to the invention, adapts to the surface of the substrate 10 and is therefore usable not only on flat or domed dials 9 but also on dials 9 having three-dimensional decorations. As illustrated in the example of FIG. 9, the stack of layers 20, 30, 40 with the openings 25 is sufficiently robust to withstand traditional finishing processes such as sunburst, spraying and shading and then allows the decoration of the dial 9 to be declined in a multitude of manual finishes. The formation of the base layer 20 with openings 25 beforehand allows, once carried out, the use of traditional electrolytes and essential manual finishing operations for obtaining the color and surface condition characteristic of luxurious opaline dials 9.The dial 9 resulting from the present manufacturing method 100 allows sufficient transmission of light to a photovoltaic cell 1 while allowing the latter to be masked, that is to say, making it invisible to a human eye. It is therefore possible to opt for a photovoltaic cell 1 whose aesthetics are not advantageous while having high aesthetic requirements and lower costs for the manufacture of the dial 9. In order to facilitate the mounting of the dial 9 on the. photovoltaic cell 1 such as its orientation, the substrate 10 can be formed during step 50 with stops forming dial feet 8 which can for example be elastically fitted.

[0079] In a manufacturing example illustrated in Figure 8, after step 80 or 90, the method 100 may comprise an optional final step 95 with at least one phase intended to form a protective layer 45 on the upper surface of the dial 9, i.e. on the layers 30 and / or 40 and the bottom of the openings 25, in particular when the layers 30 and / or 40 are silver-based, because the latter is a fragile metal and sensitive to the atmospheric environment. The protective layer 45 may for example comprise an oxide such as alumina (AI2O3) and / or titanium dioxide (CI102) formed by ALD, a layer of parylene (CsHs) deposited by chemical vapor deposition (known by the English abbreviation "CVD") or a layer of silicate (a salt combining silicon dioxide (SiC>2) with other metal oxides) deposited by chemical vapor deposition.The layer(s) 45 may make it possible to form a semi-transparent plastic dial 9 with ALD coatings which protect(s) the plastic base of the substrate 10 and / or any deposit from tarnishing such as silver-based and / or which generate(s) a whole range of colors by interference phenomena through the layers 45 (the visible color is modulated from the partially reflected light).

[0080] Additionally or alternatively, as for a traditional watch dial, the final step 95 may also include a phase intended to form a layer 46 of varnish on the upper surface of the dial 9 produced for the purposes of protection and to ensure the stability of the appearance of the dial 9 over time. Traditional varnishes of the Zapon® type include diluents and solvents which risk dissolving the material of a polymer-based substrate 10 which may make them incompatible with the latter.

[0081] If the protective layer 45 is deemed insufficient to prevent interactions between the Zapon® varnish and the substrate 10, a layer 46 of two-component varnish based on acrylic polyurethane can be used instead. Such a varnish comprises a compound of acrylic and polyurethane polymers which have different chemical and physical structures but are firmly associated in the compound which is not likely to react with a polymer-based substrate 10. Of course, it is also possible to envisage a first phase of forming a layer 46 of two-component varnish based on acrylic polyurethane followed by a second phase of forming a layer 46 of traditional varnish of the Zapon® type.

[0082] Alternatively, the substrate material 10 may also be adapted to a more chemically stable polymer such as polyamide to improve stability with the varnish layers 46.

[0083] The invention is not limited to the embodiments and variations presented and other embodiments and variations will become apparent to those skilled in the art. Thus, the above embodiments are examples. Although the description refers to one or more embodiments and their variants, this does not necessarily mean that each reference relates to the same embodiment or variant, or that the features apply only to a single embodiment or variant. Single features of different embodiments and their variants may also be combined and / or interchanged to provide other embodiments.

[0084] Furthermore, the invention cannot be limited to a timepiece. Thus, the invention could also be applied in other fields such as, for example, jewelry, jewelry, leather goods, tableware, optical instruments or writing instruments.

Claims

CLAIMS 1. Method (100) for manufacturing a watch dial comprising the following steps: a. providing a substrate (10) made of transparent material; b. depositing at least one base layer (20) on at least a portion of the substrate (10), said at least one base layer (20) being partially perforated with openings (25) according to predetermined sections allowing the openings (25) to be invisible to the naked human eye; c. depositing at least one working layer (30) on said at least one base layer (20) without blocking the openings (25) in order to form a dial (9) with an improved aesthetic appearance while allowing the transmission of electromagnetic radiation through its thickness.

2. Manufacturing method (100) according to the preceding claim, in which the transparent material of the substrate (10) is polymer-based.

3. Manufacturing method (100) according to the preceding claim, in which the transparent material of the substrate (10) is based on polyamide.

4. Manufacturing method (100) according to one of claims 1 to 3, in which step b comprises the following phases:

1. depositing said at least one base layer (20) on the substrate (10); 2. partially opening said at least one base layer (20) according to the predetermined sections.

5. Manufacturing method (100) according to the preceding claim, in which the openwork phase is obtained by laser ablation, preferably using a nanolaser.

6. Manufacturing method according to one of claims 1 to 3, in which step b comprises the following phase:

1. selectively depositing said at least one base layer (20) on the substrate (10) in order to form said at least one base layer (20) directly with the openings (25) according to the predetermined sections during its deposition.

7. Manufacturing method according to any one of the preceding claims, comprising, after step c, the following step: d. forming at least one finishing layer (40) on each working layer (30) without blocking the openings (25).

8. Manufacturing method (100) according to the preceding claim, in which step d is implemented by electroplating to form a metallic finishing layer (40).

9. Manufacturing method (100) according to claim 7 or 8, wherein, at the end of step d, a finishing operation is carried out to form a decoration (41) on the finishing layer (40).

10. Manufacturing method according to any one of the preceding claims, comprising the following final step: e. forming at least one protective layer (45) and / or one layer (46) of varnish on the upper surface of the dial (9) in order to protect the appearance of the latter.

11. Manufacturing method (100) according to any one of the preceding claims, wherein, during step b, the predetermined sections of the openings (25) have dimensions less than 35 μm in order to be invisible to the naked human eye.

12. A manufacturing method (100) according to any preceding claim, wherein step b is carried out by physical vapor deposition to form an electrically conductive metal base layer (20).

13. Manufacturing method (100) according to any one of the preceding claims, in which the openings (25) made during step b form a decoration.

14. A manufacturing method (100) according to any preceding claim, wherein step c is carried out by electroplating to form a metal working layer (30).

15. Manufacturing method (100) according to the preceding claim, in which the electroplating step c uses a galvanic bath comprising leveling agents.

16. Manufacturing method (100) according to any one of the preceding claims, wherein, at the end of step c, a finishing operation is carried out to form a decoration (31) on the working layer (30).

Images