CH711122B1 - Component of a timepiece, decorative article and deposition process. - Google Patents

Abstract

The present invention describes a method of depositing a protective and / or decorative coating on a substrate (10). The method comprises electroplating a layer (20) of eg silver, rough or porous, and reflective, on the substrate, followed by deposition by an ALD (Atomic Wash Deposition) process of a protective layer. at least partially transparent (30), for example an aluminum oxide Al 2 O 3, a titanium oxide TiO 2, a silicon oxide SiO 2, a tantalum oxide Ta 2 O 5 deposited on top of the layer rough or porous, and reflective. The method of the invention is applicable to a multitude of decorative articles among which watch components such as bridges, plates, oscillating masses, dials and other elements of watches.

Description

Description

TECHNICAL FIELD [0001] The present invention relates to a decorative coating having a white surface obtained by a superposition of layers deposited by galvanic and CVD. Embodiments of the invention relate to decorative articles with a white surface for the production of watch elements, jewelery, eyeglasses or other decorative objects, as well as a method for the manufacture of such surfaces.

STATE OF THE ART [0002] The decorative field industry, for example watchmaking, is looking for new solutions in terms of colors and appearance. Watchmaking items of white color, such as dials, are often obtained through the use of mother-of-pearl and enamel.

[0003] Several natural substances have a white color. By way of example, mention may be made of pigments consisting of microparticles of mineral substances such as titanium and aluminum oxides. These materials, which are part of a mother-of-pearl or an enamel, reflect the light in a diffuse way. Particle size and dispersion are responsible for the white appearance of the surface.

The surface of metals such as silver, platinum, palladium, rhodium, offers a bright white appearance. The silver surfaces more particularly, freshly deposited, have an extremely high coefficient of reflection and a very pure white color but they tarnish very easily to the air. Silver dulling can be limited to a certain extent by the application of several kinds of protective layers, for example nitrocellulose lacquers (Zapon). These solutions, however, do not offer absolute protection: the protective layers can become detached, they are not completely impermeable, and they tend to turn yellow with time and exposure to light.

[0005] European Patent EP 2 434 031 B1 describes a process for depositing a silver layer over a rough aluminum layer by a PVD process.

US patent application 2009 004 386 discloses a solid silver coin protection method by layers of the ALD type.

In the present invention, the colorimetric coordinates of the inventive surface are expressed using the CIEL * a * b * color space and measured according to standard CIE1976 (SCI mode, illuminant D65-100).

BRIEF SUMMARY OF THE INVENTION [0008] An object of the present invention is to provide a method of depositing a protective and / or decorative coating on a substrate free from the limitations of known coating methods.

According to the invention, these objects are achieved in particular by means of the appended claims, and in particular by means of a method for depositing a protective and / or decorative coating on a substrate comprising the following steps: electroplating d a rough, or porous and reflective layer on the substrate, for example silver, platinum, rhodium, white gold; deposition by an Atomic Layer Deposition (ALD) method of an at least partially transparent protective layer, for example an Al 2 O 3 aluminum oxide, a TiO 2 titanium oxide, a SiO 2 silicon oxide, a Ta 2 O 5 tantalum oxide, an oxide hafnium HfO2, a zirconium oxide ZrO2 deposited over the rough or porous and reflective layer.

According to one aspect of the invention the galvanic deposition is carried out at a temperature between 17 ° C and 25 ° C, preferably between 20 ° C and 22 ° C.

According to another aspect of the invention, the ALD deposition is carried out at a temperature of between 100 ° C. and 200 ° C., preferably between 120 ° C. and 150 ° C.

This solution has the advantage in particular reported by the prior art to be a simple technique to obtain this type of coating.

BRIEF DESCRIPTION OF THE FIGURES [0013] Examples of implementation of the invention are described in the accompanying figures which schematically illustrate, not to scale, and in section, the sequence of articles 100 having received a white decorative layer by the process of the invention.

Fig. 1 schematically illustrates the sequence 100 of a protective coating according to the invention.

Fig. 2 schematically illustrates a variant of the coating of the invention with a nickel layer 13 followed by a gold flash 15.

Example (s) of Embodiment of the Invention [0014] White is defined, in colorimetry, as the brightest of the gray values. In order to quantify it, a spectrophotometer is used to measure the SCI / SCE colorimetric indices which must approach as close as possible to: L * = 100, a * = b * = 0 [0015] The white color also comes from the ability of a surface to reflect white light in a diffuse manner. This condition can be achieved by a hybrid material whose transparent constituents have a different refractive index (eg wall painting, snow, etc.) that will diffuse the incident light. Another solution adopted for this application is to deposit a highly reflective material whose surface texture also diffuses the incident light. The choice was silver because it is the most reflective metal known to date.

An embodiment of the invention consists of a method for depositing a white decorative layer on a substrate 10 comprising an electroplating deposition step of a rough or porous reflective metal layer 20, followed by the deposition of an at least partially transparent layer 30 by an Atomic Layer Deposition (ALD) method. The method of the invention comprises a galvanic part and a CVD part, of which two non-limiting examples will be provided later.

Example of Galvanic Treatment The galvanic part consists in depositing a reflective metal (in this case silver) by a wet method on a conductive base (cuprous metals, ferrous metals, titanium, etc.).

Preferably, the substrate is previously washed and cleaned, in order to remove all fat residues. For example, electrolytic degreasing or ultrasonic washing can be used. Any alkaline film that remains on the surface of the support following the washing steps can be removed by appropriate packaging.

Depending on the nature of the substrate and the circumstances, one or more sub-layers may be deposited between the substrate 10 and the reflective layer 20 which will then be deposited. The role of the underlayer (s) 15 is to improve the adhesion and adhesion of the deposit and, if necessary, to remove the reflective deposit 20.

Preferably, the last underlayer is a gold flash or that of a noble metal. Indeed, this underlayer makes it possible, in the event of poor adhesion or when the deposit is irregular, to dissolve the reflective layer without attacking the substrate, which can thus be recovered.

Depending on the nature of the substrate 10 will be used as sublayer 15 a layer of nickel, copper, gold, a noble metal, or any other suitable material. The sub-layers can be applied alone or by stacking.

[0022] Conclusive results have been obtained, during tests on stainless steel substrates, by a simple underlayer constituted by a gold flash 15 followed by a reflective layer of silver (Ag), as see it in fig. 1. The substrates of copper alloys, on the other hand, received a stack of underlays: a nickel layer 13 followed by a gold flash 15, as seen in FIG. 2. This arrangement has given excellent adhesion of the layer 20, but other variations are possible.

Then comes the silvering step. Each reflective metal deposit could be used in the context of the invention, but the silver layers give a very pure and bright white, because of the very high reflectivity of this metal. We deposit a layer about 5 to 10 μm thick with a rough or porous surface topography (typical growth: "cauliflower"). In order to guarantee a homogeneous, white layer, many parameters must be taken into account. Temperature, immersion time, current density, electrolyte pH and chemistry.

By way of example, without implying a limitation of the invention, we present below an example of a process which allowed the deposition of a layer of excellent quality.

- Temperature: 18 ° C - Immersion time: 10 min - Density of current: 2 A / dm2 - Electrolyte pH: 10.8 - Electrolyte chemistry: 35 g / L KAg (CN) 2 + 200 g / L K2CO3 [0025] The layer thickness is then measured by X-ray fluorescence. Layers having a thickness of 5 μm or greater gave an optimal result.

Example of CVD treatment

[0026] Among the "Chemical Vapor Deposition" (CVD) surface treatments, Atomic Layer Deposition (ALD) technology has rapidly become an important technique for thin film deposition in a wide variety of applications. The semiconductor industry is a major consumer of this technology in order to grow oxides with high dielectric constant.

ALD technology is based on sequential self-saturated surface reactions, which lead to a controlled growth atomic layer per atomic layer of dense oxide coating. In its most standard form, one cycle comprises at least two injections, corresponding to the introduction of the two precursors of the chemical reaction, and two "purges" separating the injections, serving to remove the excess precursor and the reaction products before the reaction. introduction of the following precursor. In this example, the precursors used are successively trimethylaluminium Al 2 (CH 3) 6, abbreviated TMA and deionized water whose conductance is less than 0.5 pS.

The self-saturated growth is obtained when the two precursors do not meet in the gaseous state. All the desirable properties of ALD technology, including compliance, layer quality, and uniformity of thickness, are the result of the self-saturated growth mechanism. A total of 880 cycles is required to obtain an amorphous alumina layer with a thickness of 100 nm and a refractive index of 1.64. The injection time of the TMA is 300 ps, that of the deionized water is 300 ps and finally the purge time is 8 and 11 s, respectively. This transparent and protective coating causes a decrease in color index of up to 3%. A spectrophotometer is used to measure SCI / SCE colorimetric indices and thus validate this stage of the manufacturing range.

Prior to introduction into the ALD reactor, the surfaces coated with rough or porous electrochemical silver preferably undergo ultrasonic-assisted laundry cleaning in a slightly alkaline solution. Then, the components are placed on suitable passive stainless steel supports which will then be introduced into the reactor which will be immediately evacuated (5 mbar). In order for chemical reactions to occur, the surfaces to be coated must be brought to a precise and controlled temperature during the process. In this case, the reactor and the components are stabilized at a temperature of 150 ° C before the precursors are introduced to begin the growth of the coating. At the interface, the adhesion of the alumina film is ensured by a few injections of deionized water which makes it possible to graft hydroxyl groups, abbreviated OH, to which the first molecules of TMA will be able to bind.

According to one aspect of the invention, the layer 20 is covered by a transparent or semi-transparent protection layer 30 deposited by an ALD method. The thickness of the layer 30 is between 80 nm and 120 nm, preferably 100 nm. The value of the refractive index of the layer 30 is between 1.2 and 2.5, preferably between 1.4 and 1.8.

The ALD deposition process belongs to the category of CVD (Chemical Vapor Deposition). It allows, from a precursor, to deposit monatomic layers which are individually oxidized to obtain a continuous layer of oxide. For example, the trimethylaluminium precursor is used to obtain Al 2 O 3 layers, but layers of TiO 2, SiO 2, ZnO, HfO 2, SnO, Ta 2 O 5, ZrO 2, SrTiO 3 can also be deposited by this method. Variants also make it possible to deposit nitrides (Si3N4).

The quantitative determination of the color of a coating can be carried out using the parameters of the standard color space CIE 1976 (L *, a *, b *) designated standard CIELAB thereafter. The parameters L *, a *, b * of the standard are given in this document in relation to a measurement according to the CIE 1976 standard (observer distance - illuminant of 10 ° and a standard lighting source CIE D65 (daylight 6500 ° K), unless otherwise indicated The value of the L * color parameter is between 96.0 and 98.0, preferably 97.0.

The method of the invention allows to deposit a white coating on various items to obtain particularly attractive decorative elements. For example, it is possible to deposit a white coating by the inventive method on watch elements, in particular internal trim components such as dials, hands, indexes, bridges, plates, oscillating masses, barrels. Furthermore, the method of the invention can be applied also to other decorative items, for example jewelry or spectacle frames.

Reference numerals employed in the figures [0034] 100 Sequence 10 Substrate 13 Nickel layer 15 Gold underlayer 20 Rough or porous conductive layer 30 Partially transparent layer

Claims (16)

claims A method of depositing a protective and / or decorative coating on a substrate comprising the steps of: Electroplating deposition of a rough or porous, reflective layer (20) on the substrate (10); Deposition by an ALD method of an at least partially transparent protective layer (30) over the rough or porous and reflective layer (20). The deposition method of claim 1 wherein said rough or porous, reflective layer (20) is a layer of one of silver, platinum, rhodium, white gold. 3. deposition method according to one of claims 1 to 2 wherein an underlayer (15) or a plurality of sub-layers (15,13) are deposited between the substrate (10) and the rough or porous layer, and reflective (20). 4. deposition process according to claim 3 wherein the underlayer (15) or the sub-layers comprise a layer of a material of: nickel, copper, noble metal, for example gold. 5. Deposition process according to one of claims 1 to 4 wherein the electroplating deposition is carried out at a temperature between 17 ° C and 25 ° C, preferably between 20 ° C and 22 ° C. 6. Deposition process according to one of claims 1 to 5 wherein the duration of electroplating deposition is between 5 min and 15 min. 7. deposition process according to one of claims 1 to 6 wherein the current density for electroplating deposition is between 0.2 A / dm2 and 5 A / dm2, preferably between 0.8 A / dm2 and 1.2 A / dm2 8. Deposition process according to one of claims 1 to 7 wherein the electroplating deposition is performed in an electrolyte with a pH of between 10 and 12, preferably between 11 and 11.5. 9. Deposition process according to one of claims 1 to 8 wherein the electroplating deposition is performed in an electrolyte whose concentrations are between 30-60 g / L KAg (CN) 2 and 50-320 g / L K2CO3 . 10. Deposition process according to one of claims 1 to 9 wherein the thickness of the protective layer is between 80 nm and 120 nm, preferably 100 nm. 11. deposition method according to one of claims 1 to 10 wherein the transparent or semi-transparent protective layer (30) is a layer of a material of: Al2O3, TiO2, SiO2, ZnO, HfO2, SnO, Ta2O5 , ZrO2, SrTiO3, Si3N4. 12. Deposition process according to one of claims 1 to 11 wherein the deposition ALD is carried out at a temperature between 100 ° C and 200 ° C, preferably between 120 ° C and 150 ° C. 13. Deposition process according to one of claims 2 to 12 wherein the rough or porous layer, and reflective (20) is a silver layer, and the value of the color parameter L * according to the standard CIELAB CIE 1976 of The coating obtained is greater than 96.0, preferably greater than 97.0. Deposition process according to one of Claims 1 to 13, in which the transparent or semi-transparent protective layer (30) is a layer of a material with a refractive index of between 1.2 and 2.5, preferably between 1.4 and 1.8. 15. Component of a timepiece, for example dial, needle, index, bridge, platinum, oscillating mass, barrel, with a white surface obtained by the method of one of claims 1 to 14. 16. Decorative article with a white surface obtained by the method according to one of claims 1 to 14.