How to decorate watch components

Abstract

To produce a white "porcelain" coating that retains the surface finish of the polished, matte, sunrayed or otherwise decorated substrate.SOLUTION: The present invention relates to a process for decorating a component of a portable timepiece with a white coating. The process includes preparing the component of the portable timepiece, depositing a metal adhesion layer via physical vapor deposition, depositing an aluminum diffusing layer over the entire component under a flow of a reactive gas so that it forms a faceted crystalline structure, via physical vapor deposition, reducing or stopping the flow of the reactive gas when the diffusing layer has reached the desired thickness to terminate the deposition of the diffusing layer, and depositing a thin layer of pure aluminum, and subsequently depositing a transparent protective layer via atomic thin-film deposition.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a coating having a white surface obtained by superimposing layers deposited by PVD and ALD. The present invention further relates to a component of a watch (e.g., wristwatch, pocket watch) having such a white surface. [Background technology]

[0002] The watch industry is constantly exploring new possibilities in terms of color and appearance, with white dials and other timepieces often achieved through the use of mother-of-pearl or the application of enamel.

[0003] Noble metal surfaces such as silver, platinum, palladium, and rhodium give a brilliant white appearance. This appearance can also be achieved by galvanic deposition of these metals, which specularly reflect light and give the surface a brilliant metallic sheen. By carefully parameterizing the galvanic deposition process, the specular sheen of this coating can be reduced to a matte white.

[0004] Vacuum physical vapor deposition (PVD) techniques such as cathodic sputtering can be used to produce thin coatings with defined properties on a wide variety of substrates with complex (three-dimensional) shapes.

[0005] Many other natural substances are also white. For example, pigments made from fine particles of mineral substances such as titanium dioxide or aluminum oxide are also white. These particles diffusely reflect light. These pigments are deposited on the surface of an article as paints, lacquers, or enamels.

[0006] However, pigment-based white coatings do not provide sufficient and satisfactory decorative qualities because they do not preserve the surface finish of the material and do not accurately preserve the decorative details. Additionally, prior art galvanic coatings have a matte appearance and are relatively brittle.

[0007] Therefore, a white coating is needed that will maintain the surface finish of the substrate. Summary of the Invention [Problem to be solved by the invention]

[0008] One of the aims of the present invention is, inter alia, to overcome various drawbacks of the prior art methods.

[0009] More precisely, one of the aims of the present invention is to propose a method for producing a white "porcelain" coating that preserves the surface finish of a polished, matt, sun-exposed or decorated substrate, as well as components of a watch whose surfaces are coated with a thin white layer obtained by this method. [Means for solving the problem]

[0010] To this end, the invention relates to a method for decorating a component of a watch with a white coating, the method comprising: - providing a watch component and placing said component in a deposition chamber; - depositing a metallic adhesion layer over the watch components by physical vapor deposition; - depositing an aluminum diffusion layer over the entire component under a flow of reactive gas, the deposited layer containing 0.5-10 atomic % of the reactive gas, and recrystallizing the aluminum diffusion layer in the form of a faceted crystal structure by physical vapor deposition; - reducing or shutting off the flow of reactive gases when the diffusion layer reaches a desired thickness, thereby terminating the deposition of the stack and depositing a thin pure aluminum layer to maximize the reflectivity of the resulting stack; - depositing an optically transparent protective layer using an ALD method.

[0011] Another preferred variant of the invention has the following characteristics: said adhesion layer is a layer of a metal or metal alloy selected from the group consisting of aluminium, titanium, titanium aluminide and chromium; The thickness of the adhesive layer is between 30 nm and 100 nm, preferably 50 nm. the method comprises the additional step of depositing a dielectric layer after said adhesion layer has been deposited. The thickness of the dielectric layer is between 500 nm and 2000 nm, preferably 1000 nm. The dielectric layer can be a nitride, oxide or oxynitride of aluminum, titanium or silicon. The thickness of the diffusion layer is 300 nm to 6000 nm, preferably 1000 nm to 2000 nm, and more preferably 1500 nm. The final thickness of the pure aluminum layer is between 50 nm and 400 nm, preferably 200 nm. The thickness of the protective layer is between 0.5 nm and 20 nm, preferably 2 nm. Said protective layer may be chosen from the materials titanium dioxide, aluminium oxide, silicon dioxide and silicon nitride. The preparation of the watch components includes a cleaning step before depositing the layers described above. The components of the watch are provided with a decoration and / or a surface finish. The reactive gas during the deposition of the diffusion layer is oxygen or nitrogen.

[0012] The invention further relates to a watch component having a white coating obtained using the method described herein.

[0013] Other characteristics and advantages of the invention will become apparent from a reading of the following detailed description, given by way of example with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0014] [Figure 1] 1 shows a schematic representation of a substrate provided with a white coating obtained using the method according to the invention. [Figure 2] 1 is a schematic diagram illustrating some steps of the method according to the invention; DETAILED DESCRIPTION OF THE INVENTION

[0015] FIG. 1 shows a schematic diagram of a stack of layers obtained according to the method according to the invention.

[0016] According to one aspect of the invention, the deposition of the coating that gives the surface of the decorative article its porcelain white color is carried out by a series of PVD and ALD depositions.

[0017] Preferably, for purposes of the present invention, an enclosure equipped with a magnetron-type sputtering system is used. The spray system includes at least one aluminum spray target and a gas inlet line for creating a controlled reactive or inert atmosphere within the enclosure. The operation of this spray device is well documented in the scientific and technical literature and is known to those skilled in the art, so only a brief summary will be given here.

[0018] According to the present invention, the white surface is constructed by a coating comprising at least four layers 10, 12, 13 and 14 on a substrate 1. To achieve the desired structure of layer 12, a fifth layer, dielectric layer 11, is required on most substrates.

[0019] The method according to the invention comprises a first step 20 of cleaning the substrate, here a component of a watch, by in-situ plasma in a deposition chamber, by polarization of the substrate holder or any other method known to a person skilled in the art.

[0020] The method includes a second step 21 for depositing a first layer 10, called an adhesion layer, on the substrate 1. For example, the adhesion layer 10 can consist of aluminum deposited by spraying an aluminum source in a neutral atmosphere, i.e., without the addition of reactive gases. The adhesion layer can also be made of titanium, titanium aluminide or chromium and typically has a thickness of 30 nm to 100 nm, preferably 50 nm.

[0021] The method can include an optional step 22 of depositing a dielectric layer 11 on the adhesion layer. The dielectric layer 11 has a thickness of 500 nm to 2000 nm, preferably 1000 nm, and is composed of a nitride, oxide, or oxynitride of aluminum, titanium, or silicon. The dielectric layer 11 is used for selective nucleation of the layer 12 deposited in step 23.

[0022] The third step 23 involves depositing the second layer 12. During this step, using a cathode with an aluminum target, a reactive gas such as oxygen or nitrogen is introduced into the chamber and maintained at a rate such that an aluminum layer doped with 0.5-10 atomic % of the reactive gas, known as the diffusion layer 12, is obtained. The thickness of the diffusion layer 12 is 300-6000 nm, preferably 1000-2000 nm, and preferably 1500 nm.

[0023] The purpose of this third step is to influence the deposition of aluminum atoms by means of reactive gases so as to obtain a layer of aluminum oxide (or aluminum nitride in the case of nitrogen) with a faceted crystalline structure, which, thanks to its faceted crystalline structure, gives such a layer a diffusing effect on the incident light.

[0024] In a fourth step 24, when the oxygen-doped layer has reached the desired thickness, the cathode with the aluminum target is not quenched, and the reactive gas flow is stopped completely or gradually reduced until it stops, terminating the deposition of the diffusion layer 12 and depositing a pure aluminum layer 13, thus without doping with a reactive gas. The thickness of the final layer of pure aluminum 13 is between 50 nm and 400 nm, preferably 200 nm.

[0025] Finally, in a fifth step 25, once the pure aluminum layer 13 has reached the desired thickness, a light-transmitting protective layer 14 is deposited, preferably by ALD deposition, consisting of any of the following materials: titanium dioxide, aluminum oxide, silicon dioxide, and silicon nitride.

[0026] Thus, the diffusing layer 12 covered with the pure aluminum layer 13 effectively diffusely reflects white light, imparting a white color to the treated substrate while preserving surface finish and decorative details.

[0027] A first embodiment of the method according to the invention: The substrate 1 is plasma cleaned in-situ in the deposition chamber by polarization of the substrate holder. The aluminum adhesion layer is deposited using an aluminum target without the addition of reactive gases. Next, without switching off the cathode, oxygen is introduced into the deposition chamber and the flow of oxygen is selected and maintained so as to deposit an aluminum oxide layer having a composition substantially close to that of Al2O3. Next, without turning off the cathode, the oxygen flow is reduced and maintained to a value that causes the oxygen-doped aluminum layer to form a diffused faceted crystal structure. - Once the oxygen-doped layer has reached the desired thickness, the oxygen flow is stopped completely without turning off the cathode, completing the deposition of the diffusion layer with pure, non-oxygen-doped aluminum. Once the pure aluminum layer reaches the desired thickness, the PVD deposition process is completed and an optically transparent protective layer is deposited using ALD deposition.

[0028] A second embodiment of the method according to the invention: The substrate 1 is plasma cleaned in-situ in the deposition chamber by polarization of the substrate holder. The aluminum adhesion layer is deposited using an aluminum target without the addition of reactive gases. Next, without switching off the cathode, a reactive gas, preferably nitrogen, is introduced into the second chamber, the nitrogen flux being maintained at a value that produces a nitrogen-doped aluminum layer that forms a diffuse crystalline structure. - When the nitrogen-doped layer reaches the desired thickness, the nitrogen flow is gradually stopped without turning off the cathode, terminating the deposition of the diffusion layer and depositing pure aluminum that is not nitrogen-doped. Once the pure aluminum layer reaches the desired thickness, the PVD deposition process is completed and an optically transparent protective layer is deposited using ALD deposition.

[0029] The substrate or watch component may have a polished, structured, or decorated surface, such as a knurled, "perlage," satin-finished, "Geneva stripes," spiral, "guillochee," ray, or engraved surface. 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. This results in a white, porcelain-like, decorated surface. After application of the coating, the surface finish and topography of the substrate are preserved and fully perceptible / visible. Thus, a glossy material with "perlage" will retain its glossy appearance, and the "perlage" will be visible. Similarly, a matte material with "Geneva stripes" will retain its matte appearance, and the "Geneva stripes" will be perfectly visible.

[0030] Thanks to the method according to the invention, it is possible to deposit a white "porcelain" coating on components of any type of watch, resulting in particularly attractive ornaments. For example, internal components such as dials, hands, ornaments, bridges, plates, barrels, and oscillating weights can be white-coated using the method described herein. The method according to the invention can also be applied to ornaments.

[0031] In this way, it is possible to obtain watch components that have the white appearance of porcelain, while preserving the surface finish and decoration of the components. [Explanation of symbols]

[0032] 1. Components of a watch 10 Adhesive layer 11 Dielectric layer 12 Diffusion layer 13 pure aluminum layers 14 Protective layer

Claims

1. A method for decorating a watch component (1) with a white coating, comprising: Providing a watch component (1) and placing it in a deposition enclosure; depositing a metallic adhesion layer (10) over the watch components by physical vapor deposition; depositing a diffusion layer (12) of aluminum over the component under a flow of reactive gas, which is oxygen or nitrogen, the rate of the reactive gas being maintained such that the reactive gas results in an aluminum layer doped with 0.5 to 10 atomic percent, said aluminum layer crystallizing by physical vapor deposition in the form of a faceted crystal structure; When the diffusion layer reaches a desired thickness, reducing or shutting off the flow of reactive gases to terminate the deposition of the diffusion layer (12) and deposit a thin pure aluminum layer (13); and depositing a light-transmitting protective layer (14) by atomic thin film deposition. A method characterized by:

2. The adhesive layer (10) is a layer of a metal or metal alloy selected from the group consisting of aluminum, titanium, titanium aluminide, and chromium.

2. The method of claim 1 .

3. The thickness of the adhesive layer (10) is 30 nm to 100 nm.

2. The method of claim 1 .

4. Optionally, after depositing the adhesion layer, depositing a dielectric layer (11) under a flow of oxygen or nitrogen.

2. The method of claim 1 .

5. The thickness of the dielectric layer (11) is 500 nm to 2000 nm.

5. The method of claim 4.

6. The dielectric layer (11) is a nitride, oxide or oxynitride of aluminum, titanium or silicon.

5. The method of claim 4.

7. The thickness of the diffusion layer (12) is 300 nm to 6000 nm.

2. The method of claim 1 .

8. The thickness of the pure aluminum layer (13) is 50 nm to 400 nm.

2. The method of claim 1 .

9. The thickness of the protective layer (14) is 0.5 nm to 20 nm.

2. The method of claim 1 .

10. The protective layer (14) is selected from the materials titanium dioxide, aluminum oxide, silicon dioxide and silicon nitride.

2. The method of claim 1 .

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