Method of decorating timepiece assembly

Abstract

The invention relates to a method for decorating a timepiece component with a white coating. The method comprises preparing a timepiece component, depositing a metal adhesion layer on the entire timepiece component by physical vapor deposition in a deposition chamber, depositing an aluminum diffusion layer on the entire component by physical vapor deposition under a flow of a reactant gas, such that the aluminum layer is deposited in the form of a faceted crystal structure, and depositing the aluminum diffusion layer on the entire timepiece component. The flow of reactant gases is reduced or stopped when the diffusing layer reaches the desired thickness in order to terminate the layer with a thin layer of pure aluminum, and a transparent protective layer is deposited by atomic thin film deposition.

Description

Technical Field

[0001] The invention relates to a coating having a white surface obtained by superposition of PVD and ALD deposited layers. The invention also relates to a timepiece component having such a white surface. Background Art

[0002] The watch industry is constantly looking for new solutions in terms of colour and appearance. White timepieces, such as dials, are often achieved by using mother-of-pearl or applying enamel.

[0003] Precious metals such as silver, platinum, palladium and rhodium have a bright white appearance. Electroplated deposition of these metals can also achieve this appearance. However, they reflect light specularly, giving the surface of the article a bright metallic sheen. By carefully parameterizing the electroplated deposition method, the specular sheen of such coatings can be reduced to a matte white.

[0004] Vacuum physical vapor deposition (PVD) techniques, such as cathode sputtering, can be used to produce thin coatings with predetermined properties on substrates of various types and with complex (three-dimensional) geometries.

[0005] Many other natural substances have a white color. Examples include pigments made from microparticles of minerals such as titanium or aluminum oxide. These particles diffusely reflect light. These pigments are deposited on the surface of an article in the form of paint, lacquer or enamel.

[0006] However, pigment-based white coatings do not provide adequate and satisfactory decorative qualities. This is because they cannot maintain the surface finish of the substrate, nor can they accurately preserve the details of the decoration. In addition, prior art electroplated coatings have a matte appearance and are relatively brittle.

[0007] There is therefore a need for a white coating that maintains the surface finish of the substrate. Summary of the invention

[0008] One of the objects of the present invention is in particular to overcome the disadvantages of the prior art methods.

[0009] More precisely, one object of the invention is to propose a method for manufacturing a white "porcelain" coating that retains the surface finish of a polished, matte, sunray or other decorative substrate, as well as a timepiece component having a surface coated with a thin white layer obtained by this method.

[0010] To this end, the invention relates to a method for decorating a timepiece component with a white coating, comprising the following steps:

[0011] - preparing the watch assembly and installing said assembly in the deposition chamber;

[0012] - Deposition of a metal adhesion layer over the entire watch component by physical vapor deposition;

[0013] - depositing an aluminum diffusion layer over the entire assembly by physical vapor deposition under a flow of a reactive gas, such that the deposited layer contains 0.5 to 10 atomic % of this gas, causing the aluminum layer to crystallize in the form of a faceted crystal structure;

[0014] - reducing or cutting off the reactive gas flow when the diffuser layer reaches the desired thickness in order to complete the stack with a thin layer of pure aluminum, thus maximizing the reflectivity of the resulting stack;

[0015] - A transparent protective layer is deposited using the ALD method.

[0016] According to a further advantageous variant of the invention:

[0017] - the adhesion layer is a metal layer or a metal alloy, which can be selected from: aluminum, titanium, titanium aluminide or chromium;

[0018] - the thickness of the adhesion layer is 30 nm to 100 nm, preferably 50 nm;

[0019] - the method comprises, after depositing the adhesion layer, an additional step of depositing a dielectric layer;

[0020] - the thickness of the dielectric layer is 500 nm to 2000 nm, preferably 1000 nm;

[0021] - The dielectric layer can be a nitride, oxide or oxynitride of aluminum, titanium or silicon;

[0022] - the thickness of the diffusion layer is 300nm to 6000nm, preferably 1000nm to 2000nm, more preferably 1500nm;

[0023] - the thickness of the final pure aluminum layer is 50 nm to 400 nm, preferably 200 nm;

[0024] - the thickness of the protective layer is 0.5 nm to 20 nm, preferably 2 nm;

[0025] - The protective layer can be selected from the following materials: titanium dioxide, aluminum oxide, silicon dioxide, silicon nitride;

[0026] - the preparation of the timepiece component comprises a cleaning step before depositing the above-mentioned layers;

[0027] - the watch component has decoration and / or surface finishing;

[0028] -The reactive gas during the deposition of the diffusion layer is oxygen or nitrogen.

[0029] The invention also relates to a timepiece component having a white coating obtained using the method described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Further features and advantages of the present invention will become apparent on reading the following detailed description given by way of example and not limitation, and with reference to the accompanying drawings, in which:

[0031] - Figure 1 Schematically shows a substrate with a white coating obtained using the method of the present invention;

[0032] - Figure 2 A schematic diagram showing the steps in the method according to the invention is shown. DETAILED DESCRIPTION

[0033] Figure 1 A schematic diagram of a layer stack obtained according to the method of the invention is shown.

[0034] According to one aspect of the present invention, a coating that imparts a porcelain white color to the surface of a decorated article is deposited by sequential PVD and ALD depositions.

[0035] Preferably, a housing equipped with a magnetron-type sputtering system is used for the purposes of the present invention. The sputtering system comprises at least one aluminum sputtering target and a gas injection line for generating a controlled reactive or inert atmosphere within the housing. The operation of such a sputtering device is described in the scientific and technical literature, is well known to those skilled in the art, and will only be repeated in summary herein.

[0036] According to the invention, the white surface consists of a coating comprising at least four layers 10, 12, 13 and 14 on a substrate 1. In order to achieve the desired structure of layer 12, a fifth layer, a dielectric layer 11, is required on most substrates.

[0037] The method according to the invention comprises a first step 20 during which the substrate, here a watch component, is cleaned by polarization of the substrate holder, by an in-situ plasma in the deposition chamber or by any other method known to those skilled in the art.

[0038] The method comprises a second step 21 for depositing a first layer 10, called an adhesion layer, on the substrate 1. The adhesion layer 10 can consist, for example, of aluminum deposited by sputtering an aluminum source in a neutral atmosphere, i.e. without adding reactive gases. The adhesion layer can also be made of titanium, titanium aluminide or chromium, and has a thickness of typically 30 nm to 100 nm, preferably 50 nm.

[0039] The method comprises an optional step 22 in which a dielectric layer 11 is deposited on the adhesion layer. This layer has a thickness of 500 nm to 2000 nm, preferably 1000 nm, and consists of a nitride, oxide or oxynitride of aluminum, titanium or silicon. This layer is used for preferential nucleation of the layer 12 deposited in step 23.

[0040] The third step 23 consists in depositing the second layer 12. During this step, a cathode equipped with an aluminum target is used and a reactive gas (for example oxygen or nitrogen) is introduced into the chamber and maintained at a rate to obtain an aluminum layer doped with 0.5 to 10 atomic % of reactive gas, called the diffusion layer 12. The thickness of the diffusion layer 12 is between 300 nm and 6000 nm, preferably between 1000 nm and 2000 nm, preferably 1500 nm.

[0041] The purpose of the third step is to effect the deposition of aluminum atoms with a reactive gas in order to obtain an aluminum oxide layer (or aluminum nitride layer in the case of nitrogen) with a faceted crystal structure. Due to its faceted crystal structure, such a layer provides a diffusing effect to the incident light.

[0042] In a fourth step 24, without quenching the cathode with the aluminum target, when the desired thickness of the oxygen-doped layer is reached, the reaction gas flow is completely stopped or gradually reduced until it stops, so as to complete the deposition of the diffusion layer 12 with a pure aluminum layer 13, so no reaction gas doping is required. The thickness of the final pure aluminum layer 13 is 50nm to 400nm, preferably 200nm.

[0043] Finally, in a fifth step 25, when the pure aluminum layer 13 has reached the desired thickness, a transparent protective layer 14 is deposited, preferably by an ALD deposition method. The protective layer 14 consists of one of the following materials: titanium dioxide, aluminum oxide, silicon dioxide or silicon nitride.

[0044] Thus, the diffuser layer 12 covered by the pure aluminum layer 13 effectively diffuses the self-reflected light, imparting a white color to the treated substrate while preserving the details of its surface finish and decoration.

[0045] A first embodiment of the method of the present invention:

[0046] - In-situ plasma cleaning of the substrate 1 in the deposition chamber by polarization of the substrate holder;

[0047] -Deposition of aluminum adhesion layer using aluminum target without adding reactive gas;

[0048] - then, without extinguishing the cathode, oxygen is introduced into the deposition chamber, the flow rate of oxygen being selected and maintained so that the composition of the deposited aluminum oxide layer is substantially close to the composition of Al2O3;

[0049] - then, without extinguishing the cathode, the oxygen flow is reduced and maintained at a value that produces an oxygen-doped aluminum layer, forming a diffuse faceted crystalline structure;

[0050] - once the desired thickness of the oxygen-doped layer is reached, the oxygen flow is completely stopped, without extinguishing the cathode, to complete the deposition of the diffusing layer with pure aluminum, without oxygen doping;

[0051] - Once the desired thickness of the pure aluminum layer is reached, the PVD deposition process is completed and the transparent protective layer is deposited using the ALD deposition method.

[0052] A second embodiment of the method of the present invention:

[0053] - In-situ plasma cleaning of the substrate 1 in the deposition chamber by polarization of the substrate holder;

[0054] -Deposition of aluminum adhesion layer using aluminum target without adding reactive gas;

[0055] - Then, without extinguishing the cathode, a reactive gas (preferably nitrogen) is immediately introduced into the chamber. The nitrogen flow rate is maintained at a value that produces a nitrogen-doped aluminum layer forming a diffuse crystalline structure;

[0056] - once the desired thickness of the nitrogen-doped layer is reached, the nitrogen flow is gradually stopped without extinguishing the cathode, so as to complete the deposition of the diffusion layer with pure aluminum, without nitrogen doping;

[0057] - Once the desired thickness of the pure aluminum layer is reached, the PVD deposition process is completed and the transparent protective layer is deposited using the ALD deposition method.

[0058] The substrate or watch component has a polished, structured or decorated surface, such as engraving, "pearl", satin-finished, "Côtes de Genève", spiral, "guilloche", sunray, engraved surface, etc. The white decorative coating of the present invention is thin enough to clearly distinguish the decoration and restore the surface condition of the underlying substrate. The result is a white, porcelain-like decorative surface. Once the coating is applied, the surface finish and topography of the substrate are preserved and fully perceptible / visible. Thus, a glossy substrate with "pearl" will retain its glossy appearance and the "pearl" will be visible. Similarly, a matte substrate with "Côtes de Genève" will retain its matte appearance and the "Côtes de Genève" will be perfectly visible.

[0059] The method of the present invention can deposit a white "porcelain" coating on all types of watch components to obtain particularly attractive decorative items. For example, the method described herein can be used to white-coat interior components (e.g., dials, hands, inlays, bridges, splints, barrels, pendulums, etc.). In addition, the method of the present invention can also be applied to jewelry.

[0060] It is thus possible to obtain a timepiece component having a porcelain white appearance, while preserving the surface finish and decoration of the component.

Claims

1. A method for decorating a watch component (1) with a white coating, comprising the following steps: - preparing a timepiece component (1) and installing said component in a deposition housing; - depositing a metal adhesion layer (10) on the entire timepiece component by physical vapour deposition; - depositing an aluminum diffusion layer (12) over the entire assembly by physical vapor deposition under a reactive gas flow, maintaining the reactive gas rate to obtain an aluminum layer doped with 0.5 to 10 atomic % of reactive gas, so that the aluminum layer crystallizes in the form of a faceted crystal structure; - when the diffusing layer has reached the desired thickness, reducing or shutting off the flow of reactive gas in order to terminate the diffusing layer (12) with a thin layer of pure aluminium (13); - Deposition of a transparent protective layer (14) by atomic thin film deposition.

2. The decoration method according to claim 1, characterized in that: The adhesion layer (10) is a metal layer or a metal alloy selected from aluminum, titanium, titanium aluminide or chromium.

3. The decoration method according to claim 1 or 2, characterized in that: The thickness of the adhesion layer (10) is 30 nm to 100 nm.

4. The decoration method according to claim 1 or 2, characterized in that: It comprises the optional step of depositing a dielectric layer (11) under a flow of oxygen or nitrogen after depositing the adhesion layer.

5. The decoration method according to claim 4, characterized in that: The thickness of the dielectric layer (11) is 500nm to 2000nm.

6. The decoration method according to claim 4, wherein the dielectric layer (11) is a nitride, an oxide or a nitride oxide of aluminum, titanium or silicon.

7. The decoration method according to claim 1 or 2, wherein the diffusion layer (12) has a thickness of 300 nm to 6000 nm.

8. The decoration method according to claim 1 or 2, wherein the diffusion layer (12) has a thickness of 1000 nm to 2000 nm.

9. The decoration method according to claim 1 or 2, wherein the thickness of the pure aluminum layer (13) is 50 nm to 400 nm.

10. The decoration method according to claim 1 or 2, wherein the thickness of the protective layer (14) is 0.5 nm to 20 nm.

11. The decoration method according to claim 1 or 2, wherein the protective layer (14) is selected from the following materials: titanium dioxide, aluminum oxide, silicon dioxide, silicon nitride.

12. The decorating method according to claim 1 or 2, wherein the reactive gas used for the diffusion layer (12) is oxygen or nitrogen.

13. A timepiece component having a white face obtained by the method according to any one of claims 1 to 12.

14. The watch component according to claim 13, which is selected from the group consisting of a dial, a hand, an inlay, a bridge, a splint, an oscillating weight, a barrel, and a clasp.

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