Coloured timepiece component

Abstract

The invention relates to a timepiece component, in particular an external timepiece component, in particular a dial, characterised in that it comprises a body, one surface of which is at least partially covered by a coating forming an optical colouring device, characterised in that the coating comprises a stack of the following successive layers on the surface: - a first layer made of at least one metal material; - a second layer of semiconductor material; - a third layer made of at least one metal material; - optionally repetition of the second and third layers; - one or more oxide layers; - optionally an upper finishing layer such as an acrylic and / or nitrocellulose finishing layer, in particular a layer of zapon; - optionally, one or more layers of a metal material, in particular chromium, or titanium, inserted between two of the layers of the coating defined above, such a layer promoting adhesion and / or partial absorption of light.

Description

[0001] Colorful watch component

[0002] The invention relates to a watch component comprising a coating which forms an optical device for coloring or more generally decorating the watch component. It also relates to a timepiece comprising at least one such watch component. It also relates to a method for manufacturing such a watch component.

[0003] There are ancient and traditional processes for coloring watch components, for example by applying paint, varnish, lacquer or enamel.

[0004] New techniques by thin layer deposition are now used as an alternative, as described for example in documents EP3896193A1 and EP4060386A1. These solutions are based on the deposition of a coating comprising numerous thin layers, which make it possible to obtain different colors. These existing methods, however, have disadvantages, including their complexity and the difficulty of obtaining a repeatable and robust color, suitable for industrial manufacturing.

[0005] The general object of the invention is to propose a solution for coloring a watch component which makes it possible to improve existing solutions.

[0006] More specifically, a first object of the invention is to propose a solution for coloring a watch component which makes it possible to achieve a predefined color in a durable, robust and repeatable manner.

[0007] A second object of the invention is to propose a solution for coloring a watch component by a simple method compatible with industrial manufacturing. To this end, the invention is based on a watch component, in particular a watch exterior component, in particular a dial, characterized in that it comprises a body, one surface of which is at least partially covered with a coating forming an optical coloring device, characterized in that said coating comprises a stack of the following successive layers on said surface:

[0008] - a first layer made of at least one metallic material;

[0009] - a second layer of semiconductor material;

[0010] - a third layer made of at least one metallic material;

[0011] - optionally the repetition of the second and third layers;

[0012] - one or more layers of oxides;

[0013] - optionally a top coat such as an acrylic and / or nitrocellulose top coat, including zapon;

[0014] - optionally, one or more layers of a metallic material, in particular chromium, or even titanium, interposed between two of said layers of the coating defined above, such a layer promoting adhesion and / or partial absorption of light.

[0015] The invention also relates to a method for manufacturing a watch component, in particular a watch component for display, in particular a dial, comprising a prior step of manufacturing a body of the watch component, characterized in that it comprises the deposition of a coating on at least part of a surface of said body, this deposition of a coating comprising the following steps:

[0016] - deposition of a first layer made of at least one metallic material;

[0017] - deposition of a second layer of semiconductor material; - deposition of a third layer made of at least one metallic material;

[0018] - optionally repetition of the deposition of the second and third layers;

[0019] - deposition of one or more layers of oxides;

[0020] - optionally depositing a top finishing layer such as an acrylic and / or nitrocellulose top coat, in particular zapon;

[0021] - optionally, deposition of one or more layers of a metallic material, in particular chromium, or even titanium, intercalated between two of said layers of the coating defined above, such a layer of chromium and / or titanium having a very low thickness less than or equal to 2 nm to promote the adhesion of said two layers of coating or such a layer of chromium and / or titanium having a thickness greater than 2 nm to form a partial absorption layer.

[0022] The invention is more precisely defined by the claims.

[0023] These objects, characteristics and advantages of the present invention will be explained in detail in the following description of particular embodiments made without limitation in relation to the attached figures among which:

[0024] Figures 1a, 1b and 1c schematically represent sectional views of coatings for a component according to three variants of a first embodiment of the invention.

[0025] Figures 2a and 2b schematically represent sectional views of coatings for a component according to two variants of a second embodiment of the invention. Figure 3 schematically represents a sectional view of a coating for a component according to a third embodiment of the invention.

[0026] By convention, we will use throughout the description the adjectives "upper" and "lower", "high" and "low", and the expressions "above", "below", according to the orientations used in the figures. As a note, in these figures, the lowest layer is the one intended to be applied directly in contact with the surface of the body of a watch component and the highest layer is the one facing outwards, which forms the final external surface of the watch component.

[0027] We will subsequently use the simplified term “component” to designate a watch component.

[0028] The aim of the invention is therefore to generate a chosen color of a surface of a component. The invention is based on the use of a coating, comprising several particular superimposed thin layers, which together form an optical device whose effect is a coloring, that is to say that the effect consists of modulating the behavior in reflectivity of the light of a surface, so as to favor certain wavelengths compared to others.

[0029] The objective of this effect is naturally to allow a user to perceive a predefined color and / or more generally a decorative effect. This effect therefore occurs in the visible range of light. We will subsequently refer to the visible range as all visible wavelengths, or a significant portion of the visible wavelengths. Thus, the expression visible range can, for example, subsequently refer to a range of wavelengths between 380 and 780 nm, or even between 380 and 650 nm, or even between 380 and 550 nm. The term visible range can thus incorrectly refer to only a portion of the theoretical visible range.

[0030] As will be detailed later, the optical effect according to the concept of the invention is obtained by a stack of thin layers with chosen optical properties. The overall optical effect results from the different absorption, reflection and interference phenomena induced by the superimposed layers. In particular, the material chosen for each layer and the associated refractive index will make it possible to define the optical property sought by each layer and an overall optical effect resulting from the combination of the different layers.

[0031] The refractive index is often a complex number, which is composed in a known manner of a real part n, which defines the deflection by an interface between two given layers of an incident light ray, and an imaginary part k, which defines an extinction coefficient, which accounts for the attenuation of the incident light wave. These values ​​depend on the wavelength, and the refractive indices will therefore be considered subsequently in the visible range.

[0032] On the other hand, we will use the expression “based on a material” to designate the use of at least 50% by weight of said material.

[0033] As mentioned above, the invention is based on the use of a particular coating, which forms an optical coloring device, which is arranged on all or part of a surface of a body of a component to be colored.

[0034] More particularly, the invention is based on using a particular coating, comprising a first group comprising at least two reflective layers surrounding a layer of semiconductor material, and a second group comprising at least one oxide layer.

[0035] The first group of coating includes, in order from bottom to top:

[0036] - a first layer made of one or more metallic materials;

[0037] - a second layer of semiconductor material;

[0038] - a third layer made of one or more metallic materials.

[0039] The first and third layers thus form reflective layers, i.e. their main effect is to reflect incident light. Preferably, the first and third layers, or even the other optional reflective layers of the coating, are characterized by the fact that they form a medium whose refractive index in the visible range comprises a real part less than 3.5 and an imaginary part, i.e. an extinction coefficient, greater than 1. This real part may have a maximum value (less than 3.5) in the visible range, and form a function of the wavelength initially increasing up to this maximum value, then decreasing, with the increase in the wavelength. The imaginary part may be increasing with the wavelength.

[0040] Preferably also, these layers are made up of one or more metallic materials. Each of these layers may be entirely made of a single metallic material, or even a mixture of two or more metallic materials, arranged within the same layer or in a succession of superimposed layers. According to advantageous embodiments, the metallic material(s) are chosen from gold, platinum, titanium, palladium, chromium, rhodium, silver, copper, tungsten, aluminum, the latter being able to be encapsulated by a very thin layer of Al2O3 deposited by an ALD process (acronym for Atomic Layer Deposition). Alternatively, any metallic material may be used. According to a simple embodiment, each of the first and third layers is presented as a metallic layer, entirely made of a single metallic material, which may be the same for both layers or which may be different.

[0041] Furthermore, according to one embodiment, the first layer has a thickness greater than or equal to 100 nm. It optically isolates the coating from the body. It also contributes significantly to the overall optical rendering of the coating. This first layer is thicker than the other layers of the coating, and can act as a substrate, while being within the coating. Alternatively, this first layer can be formed by the body.

[0042] According to one embodiment, the third layer has a thickness of between 2 and 50 nm, or even between 5 and 50 nm, or even between 30 and 40 nm, and / or a thickness greater than or equal to 20 nm.

[0043] As implementation examples, the third layer can be chosen from:

[0044] - a layer of gold with a thickness of between 5 and 50 nm, or even between 30 and 40 nm, and / or with a thickness greater than or equal to 20 nm, or

[0045] - a layer of platinum or titanium or palladium or chromium or rhodium or silver between 5 and 50 nm, or even between 30 and 40 nm, and / or with a thickness greater than or equal to 20 nm, or

[0046] - a layer comprising gold and / or platinum and / or titanium and / or palladium and / or chromium and / or rhodium and / or silver between 5 and 50 nm, or even between 30 and 40 nm, and / or with a thickness greater than or equal to 20 nm.

[0047] According to an advantageous embodiment, gold is used as a metallic layer for the first and / or third layer, possibly combined with chromium as will be detailed later. Indeed, gold is an easy to deposit, robust material, and showing good reproducibility from one manufacturing cycle to another.

[0048] Advantageously, the second layer of semiconductor material is characterized by the fact that it forms a medium whose refractive index in the visible range comprises a real part greater than 2.5 and an imaginary part, that is to say an extinction coefficient, greater than 0.05. This real part may have a maximum value (greater than 2.5) in the visible range, and form a function of the wavelength initially increasing up to this maximum value, then decreasing, with the increase in the wavelength. The imaginary part may decrease with the wavelength. The extinction coefficient is in particular greater than 0.05 for wavelengths less than 550 nm, or even for wavelengths between 380 and 550 nm, or even between 380 and 650 nm, or even between 380 and 780 nm.

[0049] The second layer is based on one or more semiconductor materials. It can be present entirely in a single semiconductor material, or even in a mixture of two semiconductor materials, arranged within the same layer or in two superimposed sub-layers. According to advantageous embodiments, the semiconductor material(s) are chosen from silicon Si, germanium Ge, a combination of silicon Si and germanium Ge, a semiconductor material of the III-V families such as gallium arsenide GaAs, tantalum oxynitride (TaOxNy). As a remark, this last material can be alternatively insulating, semiconducting or electrically conductive, depending on its degree of nitriding and oxidation, respectively characterized by the values ​​of y and x. This implies that its refractive index can vary over a wide range of values.It is possible to form layers in this TaOxNy material showing optical behavior similar to that of a semiconductor, or even similar to that of silicon Si. Alternatively, any semiconductor material can be used, advantageously with an absorption coefficient greater than 0.05.

[0050] According to an advantageous embodiment, the second layer has a thickness of between 5 and 50 nm.

[0051] The use of silicon, and more generally of a semiconductor material, offers several advantages. The optical behavior of the second layer varies little with the angle of incidence, which is not the case, for example, with silicon oxide. Indeed, since the refractive index of semiconductor materials is generally high (real part greater than 2.5, or even 3, in the visible range), the trajectory of light rays is naturally brought back towards the vertical when they penetrate the material. On the other hand, the non-zero imaginary part of the refractive index of these materials implies an important role of the interfaces in the phenomenon of optical interference. This makes it possible, in particular, to greatly limit the iridescence of the color obtained.

[0052] As a side note, the semiconductor material used is unoxidized, and at least not intentionally oxidized. Likewise, this semiconductor material is unintentionally amorphous, and not hydrogenated.

[0053] The structure of this first group of the coating, comprising the use of two metal layers surrounding a layer of semiconductor material, is advantageous because it allows the amount of transmitted and reflected light to be modulated, and in particular the intensity of light that interacts with the layer of semiconductor material. In addition, the thickness of the third metal layer can be chosen so as to decouple the layer of semiconductor material from the second group of the coating. Indeed, even for a relatively transparent metal such as gold in small thicknesses, a thickness of approximately 20 nm is already sufficient to significantly attenuate the electromagnetic radiation. The third layer thus makes it possible to determine the amount of light that reaches the layer of semiconductor material.

[0054] Finally, the inventors surprisingly discovered that this combination of the said first group has very advantageous properties, which allow modulation of the optical properties over the entire visible range in a flexible, robust, reproducible way, without iridescence. The result cannot be obtained from the layers taken individually.

[0055] This first group can thus be based on a multitude of combinations of materials, including Au(substrate) / Si / Au, Au(substrate) / Si / Ag, Ag(substrate) / Si / Au, Rh(substrate) / Si / Au, (Rh / Au)(substrate) / Si / Au, Cr(substrate) / Si / Au, etc.

[0056] Optionally, this structure of the first group can be modified to incorporate one or more layers of chromium Cr, or more generally of metal, in particular intercalated between two of the three layers described previously. Such a layer of chromium can fulfill two different functions.

[0057] A thin layer of chromium, or more generally metal, less than 2 nm thick, advantageously between 0.5 and 2 nm, has little optical effect, and mainly fulfills the function of an adhesion layer. It can be intercalated between any two layers of the coating to improve their adhesion.

[0058] A layer of chromium, or more generally of metal, of greater thickness, greater than 2 nm, also contributes to the optical effect of the coating. In particular, it fulfills a function of partial absorption of the incident light. It can be associated with the first layer or the third layer, as mentioned previously. This allows, for example, to modify in a controlled and versatile manner the reflection at the interface between the layer of semiconductor material and the third layer. Such a layer can be interposed between two layers of the first group or be positioned on top of the first group, to make an interface with a second group of the coating, described later.

[0059] Alternatively, any metal can be used as a replacement for chromium depending on the desired effect, such as titanium Ti, which can act as an adhesion and / or partial absorption layer.

[0060] The first group of the coating can thus have a structure enriched by the presence of one or more layers of metal, such as chromium. Its structure can thus, for example, consist of combinations such as Au(substrate) / Si / Cr-Au-Cr, Au(substrate) / Si / Au-Cr, Au(substrate) / Si / Cr- Au, Au(substrate)-Cr / Si / Au, Au(substrate)-Cr / Si / Cr-Au, Au(substrate)-Cr / Si / Cr-Au-Cr, Au(substrate)-Cr / Si / Au-Cr, or even Au(substrate) / Si / Cr, the chromium layer here forming the aforementioned third layer.

[0061] Alternatively, instead of a sequential combination of layers involving a chromium layer such as Cr-Au-Cr, it is also possible to deposit a mixed Au layer x Cr y by co-deposition of two different materials at the same time on the same area. The sequential Cr-Au-Cr version is simpler and more robust to implement in practice and remains the preferred variant.

[0062] According to an alternative embodiment, the structure formed by the first group could be repeated, that is to say that the first group could comprise the additional superposition of a layer of semiconductor material and a reflective layer, according to a structure alternating a layer of semiconductor material and a reflective layer, in which each layer of semiconductor material is interposed between two reflective layers.

[0063] In addition, the coating comprises a second group, positioned on the first group described above. This second group comprises at least one oxide layer. This second group makes it possible in particular to modulate the reflectivity of the coating, and for example to increase the perceived clarity of the surface.

[0064] The refractive index in the visible range of each of this or these oxide layers preferably comprises a real part less than 3 and an imaginary part less than 0.05, or even less than 0.01.

[0065] According to an alternative embodiment, said one or more layers of oxides of this second group comprises two layers respectively made of two different materials, the refractive indices of which are different.

[0066] According to an alternative embodiment, each of the oxide layers of this second group consists of or is based on a material chosen from SiO2, TiO2, ALOs, SisN4, Ta2Os, TaOxNy, AlOxNy, TiOxNy. In the case of these latter ternary materials, the stoichiometry will be chosen so that the material has optical properties similar to those of the other oxides. According to one embodiment, the second group consists of:

[0067] - a layer of silicon oxide SiO2 with a thickness of between 20 and 140 nm, preferably between 40 and 75 nm, and / or

[0068] - a layer of titanium oxide TiO2 with a thickness of between 5 and 100 nm, preferably between 5 and 50 nm.

[0069] In all cases, the thicknesses of the oxide layers are minimized, low, in order to minimize the iridescence they cause and to have good industrial robustness.

[0070] This second group, in addition to participating in the definition of the optical properties of the coating, also makes it possible to form a protective layer for the coating, and thus to increase the environmental robustness of the stack of layers of the coating.

[0071] Finally, the second group optionally comprises a top finishing layer, such as an acrylic and / or nitrocellulose layer, in particular zapon, which is therefore positioned on the oxide layer(s). Alternatively, this finishing layer may comprise another material, such as a sol-gel type material. This finishing layer may also comprise functional compounds such as a dye or diffusing particles. As a note, in such a case of using a finishing layer, such as an acrylic and / or nitrocellulose layer, in particular zapon, it is advantageous to deposit a final layer of metal, in particular chromium, with a thickness of less than 2 nm, and preferably greater than 0.5 nm, on the last layer of oxides, i.e. the highest, to form an adhesion layer for the finishing layer.It has indeed been noted that such a layer very significantly reinforces the adhesion of the acrylic and / or nitrocellulose topcoat to the structure. As a further note, if an acrylic and / or nitrocellulose topcoat is used, its optical properties are also considered. Indeed, some products used for such a topcoat, for example "Zapon", have a refractive index close to that of SiO2 oxide. In this case, it may be advantageous not to deposit a SiO2 oxide layer, since the optical effect of the latter can be masked to a very large extent by the effect of the topcoat.

[0072] The second group preferably does not include a metal layer producing an optical effect. Only a thin metal layer, for example of chromium and / or titanium, with a thickness of less than 2 nm, can be used, for its function of strengthening the adhesion between layers.

[0073] Generally, some parts of the stack forming the coating can be split to modulate or strengthen their effect. For example, it is possible to split the first group of layers, and thus to have for example an Au(substrate) / Si / Au / Si / Au stack, with or without intercalated Cr layers, at some or all of the interfaces, as described previously. In such a structure, the thicknesses of the layers can be different for the same material, for example the thickness of the first Si layer can be different from that of the second Si layer. On the other hand, whether intentional or not, the second Si layer can have a different residual oxidation state than the first. Similarly, it is possible to split the second group of layers, and therefore have, for example, a TiO2 / SiO2 / TiO2 / SiO2 stack instead of TiCk / SiCk, or a SiO2 / TiO2 / SiO2 / TiO2 / Zapon stack instead of SiCk / TiCk / Zapon.The coating according to the invention allows numerous combinations of layers, which makes it possible to obtain a wide range of colors and renderings, in particular colors in red, purple, blue, green or even brown tones.

[0074] The table below gives some examples of layers made, with the colors obtained. The brightness L* and the color values ​​a* and b* are evaluated in the space defined by the International Commission on Illumination, CIE L*a*b*, as indicated in the “Technical Report of Colorimetry” CIE 15: 2004. The measurements are made in SCI (Specular Component Included) and SCE (Specular Component Excluded) mode and are presented below in SCI mode.

[0075] Color L*a*b* (SCI) Stack Thicknesses (nm)

[0076] Green 43 / -14 / 15 Au(substrate) / Si / Cr / Au / >100 / 35 / 3 / 7 / 32

[0077] TiO2

[0078] Green 58 / -6 / 10 Au(substrate) / Si / Au / >100 / 39 / 34 / 17 / 41 dark TiO2 / SiO2

[0079] Blue 85 / 1 / 8 Au(substrate) / Si / Au / >100 / 29 / 25 / 75 / 47 clear SiO2 / TiO2

[0080] Brown 49 / 11 / 11 Au(substrate) / Cr / Si / Au / >100 / 17 / 12 / 15 / 8

[0081] TiO2

[0082] Brown 52 / 7 / 9 Au(substrate) / Cr / Si / Cr / >100 / 17 / 12 / 3 / 14 / 3 / 6 light Au / Cr / TiO2 In general, our approach allows obtaining a very wide range of colors by optical interference of light, and in particular of colors different from black. Black can be defined as colors having L*a*b* coordinates such that -2 < a* < 2 and -2 < b* < 2 and L* < 30.

[0083] Figures 1a to 1c schematically represent variants of a first embodiment of a coating according to the invention. In all these variants, the first group of the coating comprises the same structure of two layers of gold surrounding a layer of silicon. The first two variants comprise a second group composed of two oxide layers, respectively of silicon dioxide SiO2 and titanium dioxide TiO2, the order of which is reversed for the second variant. The third variant of Figure 1c has the same stack as the first variant of Figure 1a on which a top layer of zapon is added.

[0084] Figures 2a and 2b schematically represent variants of a second embodiment of a coating according to the invention. According to the embodiment of Figure 2a, the first group of the coating comprises a structure of two layers of gold surrounding a layer of silicon. The second group comprises an oxide layer, in this case titanium dioxide TiO2, on which a finishing layer of zapon is added. Figure 2b represents an alternative embodiment of that of Figure 2a, in which a thin layer of chromium is interposed between each pair of adjacent successive layers of the embodiment of Figure 2a, to increase the adhesion between these layers.

[0085] Figure 3 finally schematically represents a third embodiment of a coating according to the invention. The first group integrates three relatively thick chromium layers, respectively arranged on each of the three base layers of the first group, to provide an optical complement to the first group. In other words, the first layer forming the substrate comprises a thick gold layer completed by the superposition of a chromium layer, and the third gold layer is completed by its positioning between two chromium layers. The second group is identical to that of the embodiment according to Figure 1c.

[0086] The coating according to the invention described above may be combined with other characteristics contributing to a coloring effect or more generally to the decoration of the component. For example, the surface to be decorated of the component may comprise a surface structuring, wholly or partly covered by the coating described above. This coating has a total thickness sufficiently low to match and preserve the reliefs of the surface structuring. A surface structuring may consist, for example, of sunburst, sandblasting, satin finishing, brushing, snailing, at least one Côte de Genève, pearling, hooping, and / or any type of decoration with repeated patterns.

[0087] The body may be made of many materials, and in particular may be made of brass, gold, ceramic, in particular zirconia or alumina, sapphire, silicon, nickel Ni, or nickel-phosphorus NiP. It may be a body entirely made of the same material, or comprising several materials. In particular, the surface of the body to be colored may comprise a layer of material, for example to facilitate the production of a surface structuring as mentioned above in its thickness. Such a layer may for example be made of silver.

[0088] The component may be a watch component, for example a watch component for display such as a dial, a bezel, a bezel disc, a crystal, a case, a bracelet, or a watch movement component, such as a weight or a blank or a bridge or a barrel cover or a pawl cover.

[0089] The invention also relates to a method for manufacturing a watch component, in particular a watch component for display, in particular a dial, comprising a prior step of manufacturing a body of the watch component, characterized in that it comprises the deposition of a coating on at least part of a surface of said body, this deposition of a coating comprising the following steps:

[0090] - deposition of a first layer made of at least one metallic material;

[0091] - deposition of a second layer of semiconductor material;

[0092] - deposition of a third layer made of at least one metallic material;

[0093] - optionally repetition of the deposition of the second and third layers;

[0094] - deposition of one or more layers of oxides;

[0095] - optionally depositing a top finishing layer, such as an acrylic and / or nitrocellulose layer, in particular zapon;

[0096] - optionally, deposition of one or more layers of a metallic material, in particular chromium, or even titanium, intercalated between two of said layers of the coating defined above, such a layer of chromium having a very low thickness less than or equal to 2 nm to promote the adhesion of said two layers of coating or such a layer of chromium having a thickness greater than 2 nm to form a partial absorption layer.

[0097] The deposition of the different layers by the above-mentioned steps is carried out in the order indicated, the different layers being superimposed on each other, starting from the surface of the body of the component. These layers are therefore superimposed and adjacent, arranged according to the order indicated, with the exception of any intermediate layers of metal, in particular chromium, which may be intercalated between these different layers, according to the optional deposition mentioned.

[0098] According to an advantageous embodiment, all or part of the layers of the coating are deposited by physical vapor deposition PVD, for example by vacuum evaporation or sputtering or by ion beam, by chemical vapor deposition CVD, or by atomic layer deposition ALD.

[0099] Furthermore, advantageously, all the layers of the coating could be deposited by the same technique in the same manufacturing cycle, apart from a possible top finishing layer such as an acrylic and / or nitrocellulose finishing layer, in particular zapon. These deposits are preferably made without air exposure between the deposition of two successive layers.

[0100] Alternatively, different deposition techniques can be used, including PVD, CVD or ALD, for different layers of the coating, provided they are compatible.

[0101] As a first example of the implementation of the manufacturing process, vacuum evaporation is used, which allows the deposit of thin layers of the elements Si, Cr, Au, TiO2 and SiO2 with very well-controlled thickness. The semiconductor layer is then made of Si, the metallic layers of Au, and possibly Cr, the optional adhesion layers of Cr and the oxide layers of TiO2 and SiO2.

[0102] As a second example of the manufacturing process implementation, sputtering is used, which also allows the deposit of thin layers of the elements Si, Cr, Au, TiO2 and SiO2 with very well-controlled thickness. The semiconductor layer is then made of Si, the metallic layers of Au, and possibly Cr, the optional adhesion layers of Cr and the oxide layers of TiCb and SiO2.

[0103] As a third example of the manufacturing process implementation, sputtering is used, which allows the deposit of thin layers of TaOxNy, Cr, and Au of very well-controlled thickness. The semiconductor layer is then made of TaOxNy, the metal layers of Au, and possibly Cr, the optional adhesion layers of Cr, and the upper layers of TaOxNy.

[0104] It is possible to use different variations of the deposition techniques known to those skilled in the art. For example, Ar can be projected onto the components during deposition, which densifies the layers, according to the ion beam assisted PVD technique. The same ion beam can also be supplied with O2 or N2 to promote oxidation and / or nitriding of the coating respectively.

[0105] The characteristics of the deposited layers can be observed during deposition in a known manner. For example, a quartz microbalance placed within the deposition chamber allows the deposited thickness to be monitored with high precision. Similarly, it is possible to perform an analysis of the optical transmission or optical reflection of the deposited layer during deposition, which makes it possible to target an optical property target and not a thickness target.

[0106] Indeed, the chambers of the deposition machines are placed under vacuum during the deposition cycles. However, the residual atmosphere invariably contains residual gases such as O2 or H2O or N2, which means that a certain degree of oxidation and / or partial nitriding of the layers is possible, unintentionally. This unintentional phenomenon can be minimized, or even eliminated, by preparing the deposition machine appropriately, in particular by cleaning it. This partial oxidation and / or nitriding is likely to have an influence on the optical properties and therefore potentially on the overall appearance of the deposited coating. If necessary, it is possible to adapt the thicknesses of the layers to compensate for and eliminate this unintentional optical effect, and to obtain the correct appearance.

[0107] Measurements have shown that the Si semiconductor material deposited according to the invention has an optical behavior close to pure, non-oxidized Si. Indeed, refractive index measurements in a "clean" machine (long pumping time), with a low residual oxygen partial pressure, give a refractive index n of 4.04 for an incident wavelength of 550 nm and 3.87 for an incident wavelength of 630 nm, which is very close to the values ​​for pure silicon (4.39 for amorphous silicon and 4.08 for crystalline silicon at 630 nm). In a "dirty" machine (shorter pumping time), the refractive index measurements are 3.35 for an incident wavelength of 550 nm and 3.20 for an incident wavelength of 630 nm, which is lower but still very far from the value of 1.47 for silicon dioxide SiO2. Similarly, the extinction coefficients k remain very high, and very much greater than 0.05 over a large part of the visible part of the spectrum. The Si-based material deposited by the process of the invention therefore always behaves like a semiconductor, whatever the state of the deposition machine and the possible natural, unintentional oxidation phenomenon.

[0108] In summary, the preceding considerations show that it is therefore possible to implement the invention as described based on a coating comprising a first group with a second layer of semiconductor material. This semiconductor material may have oxidation, in particular unintentional oxidation, which is either negligible or compensated by an adaptation of the thicknesses of the layers of the coating, in order to obtain the desired result, in particular the desired color.

[0109] Finally, the invention has the advantage of simplifying the manufacturing process, particularly by using a second layer of semiconductor material. In addition, the semiconductor material provides advantageous optical properties: in fact, the semiconductor material has a high refractive index, is partially absorbent (extinction coefficient k > 0.05 over a large part of the visible range), and is robust (it allows industrial and reproducible deposition, stable over time).

[0110] The invention has many other advantages. Beyond the reflection spectrum obtained, the durability of the stack, i.e. the consistency of the rendering over time, or its manufacturing robustness (reproducibility from one manufacturing batch to another, the number of layers being as low as possible and thin thicknesses, deposition techniques being as compatible as possible, or even unique for the entire stack) will be just as important.

[0111] It is also possible to list the following advantages of the invention:

[0112] ► Usable on small and large series in an industrial and reproducible manner;

[0113] ► Stacking of layers that can be deposited easily in the same deposition equipment during the same cycle;

[0114] ► Robustness and durability;

[0115] ► Many possible colors on the same basis, due to the multitude of influential parameters; ► Obtaining a rendering target, in particular a color, for example a color according to the CIE L*a*b* reference, in particular a color different from black, or a color outside the domain defined by -2 < a* < 2 and -2 < b* < 2 and L* < 30;

[0116] ► Optimization over the entire visible range, not over a single wavelength or a restricted range;

[0117] ► Little, if any, iridescence.

[0118] As a note, as previously described, it is possible to use an ultra-thin metal layer, with a thickness of less than 2 nm, in particular a layer of chromium or titanium, at at least one of the interfaces between two layers of a coating, to promote adhesion between said two layers.

[0119] It turns out that this effect is particularly remarkable for the adhesion of a finishing layer, such as an acrylic and / or nitrocellulose finishing layer, for example in zapon, so as to promote the adhesion and / or robustness of this finishing layer. Thus, this approach can be implemented in all the embodiments envisaged by the invention. This approach can also be implemented to promote the adhesion and / or robustness of this finishing layer regardless of the type of layers and / or underlying structure^).

[0120] More generally, such a characteristic can be generalized to any finishing layer to be deposited on any coating on the surface of a component.

[0121] Thus, the invention also relates to a watch component, in particular a watch component for display, in particular a dial, characterized in that it comprises a body, one surface of which is at least partially covered with a coating, characterized in that said coating comprises a finishing layer such as an acrylic and / or nitrocellulose finishing layer, in particular zapon, and an intermediate layer on which this finishing layer is deposited, made of metallic material, in particular chromium, or even titanium, with a thickness of less than 2 nm, to promote the adhesion of said finishing layer.

[0122] The invention also relates to a method for manufacturing a watch component, in particular a watch component for display, in particular a dial, comprising a prior step of manufacturing a body of the watch component, characterized in that it comprises the deposition of a coating on at least part of a surface of said body, this deposition of a coating comprising the following steps:

[0123] - deposition of a layer of a metallic material, in particular chromium or even titanium, with a thickness less than or equal to 2 nm, then

[0124] - depositing a finishing layer such as an acrylic and / or nitrocellulose finishing layer, in particular zapon, directly onto said layer of a metallic material, so that this finishing layer has improved adhesion due to said layer of a metallic material.

[0125] The invention has been described on the basis of a coating which comprises a second group comprising one or more oxide layers. In any case, each oxide layer of this second group could be replaced by a layer of a semiconductor material, to take advantage of the advantageous properties of a semiconductor material, as described previously. Thus, according to one embodiment, the coating comprises a second group arranged on a first group as described, this second group comprising one or more layers of semiconductor material, such as for example a layer of TaOxNy.

Claims

Claims 1. Watch component, in particular a watch component for exterior use, in particular a dial, characterized in that it comprises a body, one surface of which is at least partially covered with a coating forming an optical coloring device, characterized in that said coating comprises a stack of the following successive layers on said surface: - a first layer made of at least one metallic material; - a second layer of semiconductor material; - a third layer made of at least one metallic material; - optionally the repetition of the second and third layers; - one or more layers of oxides; - optionally, one or more layers of a metallic material, in particular chromium, or even titanium, interposed between two of said layers of the coating defined above, such a layer promoting adhesion and / or partial absorption of light.

2. Watch component according to the preceding claim, characterized in that - the first and / or the third layer is in a material having a refractive index in the visible range which includes a real part less than 3.5 and an extinction coefficient greater than 1; and / or - the second layer is in a material having a refractive index in the visible range which includes a real part greater than 2.5 and an extinction coefficient greater than 0.05; and / or - the oxide layer(s) is in a material having a refractive index in the visible range which includes a real part less than 3 and an extinction coefficient less than 0.05, or even less than 0.

01.

3. Watch component according to one of the preceding claims, characterized in that the first layer has a thickness greater than or equal to 100 nm and / or is entirely made of one or more metallic materials chosen from gold, platinum, titanium, palladium, chromium, rhodium, silver, copper, tungsten, aluminum.

4. Watch component according to one of the preceding claims, characterized in that the second layer has a thickness of between 5 and 50 nm and / or is entirely made of a semiconductor material chosen from silicon Si, germanium Ge, a combination of silicon Si and germanium Ge, a semiconductor material of the III-V families such as gallium arsenide GaAs, tantalum oxynitride (TaOxNy).

5. Watch component according to one of the preceding claims, characterized in that the third layer has a thickness of between 2 and 50 nm, or even between 5 and 50 nm, and / or in that the third layer is entirely in one or more metallic materials chosen from gold, platinum, titanium, palladium, chromium, rhodium, silver, copper, tungsten, aluminum or in that the third layer is a layer of gold with a thickness of between 5 and 50 nm, or even between 30 and 40 nm, and / or with a thickness greater than or equal to 20 nm.

6. Watch component according to one of the preceding claims, characterized - in that said one or more layers of oxides comprise two layers respectively made of two different transparent materials, the refractive indices of which are different, - or in that it comprises one or more layers of material chosen from SiO2, TiO2, A^Os, SisN4, Ta20s, TaOxNy, AlOxNy, TiOxNy, - or in that said one or more layers of oxides or semiconductor material comprises: - a layer of silicon oxide SiO2 with a thickness of between 40 and 140 nm, preferably between 40 and 75 nm, and / or - a layer of titanium oxide TiO2 with a thickness of between 5 and 100 nm, preferably between 5 and 50 nm, a layer of chromium with a thickness of less than or equal to 2 nm being optionally added to promote the adhesion of one or more layers.

7. Watch component according to one of the preceding claims, characterized in that it comprises at least one layer of a metallic material, in particular chromium, with a thickness of between 0.5 and 2 nm, arranged between two layers of the coating to promote the adhesion of said two layers of the coating, and / or in that it comprises at least one layer of a metallic material, in particular chromium, with a thickness greater than 2 nm, arranged between two layers of the coating to form a partial absorption layer modifying the optical behavior at the interface of said two layers of the coating.

8. Watch component according to one of the preceding claims, characterized in that it comprises a surface structuring carried out on all or part of said surface of the body, in particular a surface structuring such as sunburst, sandblasting, satin finishing, brushing, snailing, at least one Geneva stripe, perlage, hooping, and / or any type of decoration with repeated patterns, the coating being at least partially arranged on said surface and thickness structuring weak enough to fit and preserve the reliefs of the surface structure.

9. Watch component according to one of the preceding claims, characterized in that the body is made of brass, gold, ceramic, in particular zirconia or alumina, sapphire, silicon, nickel Ni, or nickel-phosphorus NiP, and / or in that it is a dial, a bezel, a bezel disc, a crystal, a case, a bracelet, a watch movement component, such as a mass or a blank or a bridge or a barrel cover or a pawl cover.

10. Watch component according to one of the preceding claims, characterized in that said coating forms an optical device with a coloring distinct from black defined as the colors having coordinates L*a*b* -2 < a* < 2 and -2 < b* < 2 and L* < 30.

11. Watch component according to one of the preceding claims, characterized in that said coating comprises an upper finishing layer such as an acrylic and / or nitrocellulose finishing layer, in particular zapon.

12. Timepiece, in particular watch, characterized in that it comprises a timepiece component according to one of the preceding claims.

13. Method for manufacturing a watch component, in particular a watch component for exterior use, in particular a dial, comprising a prior step of manufacturing a body of the watch component, characterized in that it comprises the deposition of a coating on at least part of a surface of said body, this deposition of a coating comprising the following steps: - deposition of a first layer made of at least one metallic material; - deposition of a second layer of semiconductor material; - deposition of a third layer made of at least one metallic material; - optionally repetition of the deposition of the second and third layers; - deposition of one or more layers of oxides; - optionally depositing a top finishing layer such as an acrylic and / or nitrocellulose top coat, in particular zapon; - optionally, deposition of one or more layers of a metallic material, in particular chromium, or even titanium, intercalated between two of said layers of the coating defined above, such a layer of chromium having a very low thickness less than or equal to 2 nm to promote the adhesion of said two layers of coating or such a layer of chromium having a thickness greater than 2 nm to form a partial absorption layer.

14. Manufacturing method according to the preceding claim, characterized in that all or part of the layers of the coating are deposited by physical vapor deposition PVD, in particular by vacuum evaporation, or cathodic sputtering, or by chemical vapor deposition CVD, or by atomic layer deposition ALD.

15. Manufacturing method according to one of claims 13 to 14, characterized in that all the layers of the coating, apart from a possible upper finishing layer such as an acrylic and / or nitrocellulose finishing layer, in particular zapon, are deposited by the same method in the same manufacturing cycle.

16. Manufacturing method according to one of claims 13 to 15, characterized in that it comprises a step of measuring the thickness of a deposited layer and / or measuring the optical transmission or optical reflection of a deposited layer during a deposition step, so as to determine the end of said deposition step as a function of the measurement(s).

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