CH709669A1 - protective layer, decorative and deposition process. - Google Patents

Abstract

The invention relates to a protective and decorative coating and its deposition process combining PVD and ALD layer depositions. The first layer (11) is a metal layer or non-deposited by PVD or ALD. The second layer (12) is a transparent layer deposited by ALD. The particular color of the coating is a function of the thickness of the transparent layer. For example, a color identical to that of rhodium is obtained. Protection and / or decoration can also be done on a sintered tungsten material. Due to the insulating nature of the ALD layer, two-color coatings can be made by creating openings in the second layer, for example by laser ablation or selective ablation, in which galvanic layers can be deposited. The invention further relates to an element for a timepiece comprising a coating according to the invention.

Description

Technical area

The present invention relates in particular, but not exclusively, to a decorative coating and / or protector having a metallic luster or a color with metallic dyes. This method is particularly suitable for the protection of elements used in timepieces, such as plates, bridges, gear wheels, screws, oscillating masses, dials, indexes, sconces, wickets, needles or any other element of the movement or outer wrapping, but also for applications in leather goods, jewelery, eyewear, manufacture of writing instruments and portable electronic devices.

In embodiments, the coating of the invention has a two-color pattern obtained by the selective deposition of galvanic layers of different colors from the rest of the substrate provided with the coating of the invention.

State of the art

In the state of the art is already known PVD (physical vapor deposition or physical deposition in vapor phase) deposition techniques to obtain protective layers and / or decorative on all kinds of articles. These techniques are used for example to give a distinctive aesthetic appearance to apparent elements used in the production of watches. For example, it is known to apply PVD coatings to metal parts giving them a glossy appearance or mast depending on the state of the initial surface, metallic gray, black, or colored, depending on the method used. The color palette that can be achieved by these techniques is however limited.

It is also known to deposit by PVD thin and transparent layers with a thickness comparable to or less than the wavelengths of visible light, which give the surfaces on which they are deposited a color attributable to an interference phenomenon. This process makes it possible to obtain interfering colors ranging from dark yellow to green, passing through shades of violet and blue, which are difficult to achieve by other means. However, especially when the parts to be coated are not flat, but complex geometries, the color thus obtained is not uniform.

[0005] PVD or galvanic layers are also commonly used for the protection of parts made of materials subject to corrosion, or to give a precious appearance to ordinary materials.

To this end, it is often used galvanic layers of rhodium which have a very nice and sought after shiny appearance, especially by watch manufacturers. These methods do not always succeed in guaranteeing perfect adhesion on all substrates, such as, for example, sintered tungsten which is used in the production of oscillating masses of movements of automatic mechanical watches. In addition, galvanic processes employ toxic chemicals whose handling and disposal are expensive and burdensome.

Cathodic sputtering and other PVD processes allow perfect adhesion on most substrates, and employ toxic reagents in very limited quantities. However, these methods do not make it possible to produce rhodium layers which can compete economically with that of the galvanic rhodium.

[0008] ALD (Atomic Layer Deposition or Atomic Deposition) deposition techniques are also known. These techniques make it possible in particular to deposit very dense and conformal layers on a plurality of substrates.

[0009] GB 2 455 993 describes the use of the ALD technique for obtaining decorative layers of colors and for obtaining protective layers by combining a PVD layer and the deposition of a transparent layer by ALD. However, the color of this coating is determined by metallic or pigmented nanoparticles dispersed in the transparent ALD phase. This document does not mention the nature of the substrate.

Brief summary of the invention

An object of the present invention is to provide a protective layer and / or decorative and its method, free from the limitations of known methods.

According to the invention, these objects are achieved in particular by means of the appended claims, and in particular by means of a coating for the protection and / or decoration of a component of a timepiece comprising, on a substrate: a first at least partially reflective layer, for example of aluminum, palladium, gold or silver, preferably deposited by a PVD method (Physical Vapor Phase Deposition); a second at least partially transparent layer, for example aluminum oxide Al2O3, titanium oxide TiO2, silicon oxide SiO2, tantalum oxide Ta2O5, deposited by an ALD (Atomic Deposition) process above the first layer.

In preferred embodiments, the first layer is a layer of PVD aluminum, while the second layer is an ALD layer of aluminum oxide (Al2O3), whose thickness is chosen according to the color that the we want to get. Thickness layers between 40 nm and 80 nm, preferably between 50 nm and 70 nm, more preferably between 55 nm and 65 nm give coatings which are essentially identical in appearance to galvanic rhodium, without the disadvantages mentioned above. -above.

In other possible variants, the first layer 11 could also be deposited by a chemical deposition process, for example an ALD process.

[0014] Semi-transparent ALD layers of greater thicknesses make it possible to obtain interferential colors in the range of browns, magenta, blue, yellow, orange, purple, green, pink, depending on the increasing thickness of the layer. Compared to similar structures obtained by PVD, this technique gives remarkably uniform layers of thickness and color on substrates of any geometry,

We can optionally make openings in the second layer ALD, which is dielectric, to expose the underlying layer or substrate and deposit galvanic layers in these openings to obtain two-color or multicolored coatings.

The present invention also relates to a method of producing the coating mentioned above, as well as components of timepieces thus coated. In particular, the present invention lends itself particularly to the production of oscillating masses for automatic mechanical watch movements, as well as the movement plates because the coating of the invention is of a sufficiently small thickness not to influence the tolerances. receptacle holes of the driven elements (bearings, clockwork, axes).

Brief description of the figures

Examples of implementation of the invention are indicated in the description illustrated by the appended figures in which: <tb> Fig. 1 <SEP> schematically illustrates the structure of a protective and decorative coating according to the invention. <tb> Fig. 2 <SEP> illustrates the colorimetric parameters of a coating according to the invention. <tb> Figs. 3a and 3b <SEP> schematically illustrate a variant of the coating of the invention with selective openings in which a third galvanic layer is deposited.

Example (s) of embodiment of the invention

With reference to FIG. 1, the coating of the invention comprises, on a suitable substrate 10, a first reflecting layer 11 made by a PVD method. Any suitable material can be used as the substrate, but very successful tests have been made with sputtered aluminum layers on brass, steel, titanium or sintered tungsten substrates. The invention is not limited to these materials in particular. In the context of the invention, the layer 11 is also not limited to an aluminum layer, but could also include a layer of silver, gold, palladium, or any other material likely to be present. thus deposited. The same layers could also be deposited, in the context of the invention, by another suitable deposit method.

According to one aspect of the invention, the first layer 11 is covered by a second transparent or semi-transparent layer 12 deposited by an ALD method. Preferably, the thickness of the layer 12 is of the order of the wavelength of the visible light and, in this way, it imparts a predetermined color to the coating. The ALD deposition process is part of the CVD (Chemical Vapor Deposition) class. 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 TiO 2, SiO 2, ZnO, HfO 2, SnO, or Ta 2 O 5 layers can also be deposited by this method. Variants make it possible to deposit also nitrides (TiN, TaN, Si3N4, WN, NbN) metals (Al, Ru, Ir, Pt), or sulphides (ZnS).

The quantitative determination of the color of a coating can be carried out using the parameters of the CIE standard color space 1976 (L *, a *, b *) designated CIELAB standard thereafter. The parameters L *, a *, b * of the standard are given in this document in relation to a measurement according to the CIE 1964 standard (observer distance - illuminant of 10 ° and a standard lighting source CIE D65 (daylight 6500 ° K), unless otherwise indicated.

FIG. 2 illustrates the colorimetric properties of an exemplary coating according to the invention comprising, on a substrate, a first metallic Al PVD layer and a second transparent Al2O3 layer deposited by an ALD method. The parameters L *, a *, b * were measured for various thicknesses of the oxide layer. The curve 31 indicated by the filled circles is that of the parameter L *, represented at 1:10 scale with respect to the parameters a * and b *; the curve 32 marked by squares gives the variation of the parameter a * and the curve 33 with the triangles that of the parameter b *. The horizontal lines 36, 37, 38 indicate, for comparison, the parameters L * / 10, a *, b * of a rhodium flash used as the reference color.

FIG. 2 indicates that Al2O3 layers of thickness between 40 nm and 80 nm significantly change the perceived color of the coating. An ALD layer whose thickness is in this range thus makes it possible to obtain metal coatings of a predetermined color, which at the same time protects the underlying layer and the substrate.

More particularly, Al2O3 layers with thicknesses close to 60 nm give rise to a coating whose color is essentially identical to that of the reference color. Those skilled in the art can choose a thickness of Al2O3 between 40 nm and 80 nm, preferably between 50 nm and 70 nm, more preferably between 55 nm and 65 nm to mimic rhodium-plated objects or with a color parameter L * according to the CIELAB standard which is equal to or greater than 80; the color parameter a * according to the CIELAB standard which is between 0 and 2 and the color parameter b * according to the CIELAB standard which is between 4 and 0.

It is also possible to obtain a comparable effect by depositing a first layer 11 of any material with a color substantially identical to that of aluminum or characterized by predetermined color parameters, for example with color parameters L * = 95 ± 0.5; a * = 0 ± 0.5; b * = 0 ± 0.5.

The method of the invention is particularly advantageous in the production of oscillating masses used in the movements of automatic mechanical watches. The heavy metal of the oscillating masses is usually sintered tungsten which has a very high density. This dull gray-looking material, however, is almost always covered by a galvanic coating to give it a glossy appearance and protect it from corrosion. By the method illustrated above it is possible to obtain oscillating masses which, when used in a movement with rhodium-plated components, seem to be made of the same material as the other elements of the watch. Furthermore, the method of the invention can also be applied to the plate, the bridges, the movement mobiles, usually made of steel, brass or titanium. In addition, the method of the invention described above also provides protection against corrosion.

According to an alternative embodiment, when the thickness of the semi-transparent layer is greater, there are obtained coatings having a color by interference effect. A wide range of colors from brown, magenta, blue, yellow, orange, purple, green, pink, can be obtained. Advantageously, the thickness of the ALD layers does not depend on the orientation of the surface in the deposition apparatus, and this makes it possible to obtain layers whose thickness is remarkably constant, giving rise to highly uniform color coatings. and reproducible, which would have been impossible if the transparent layer had been deposited by PVD methods, which are inherently directional.

Preferably, in this embodiment, is deposited under the transparent layer a gray PVD layer or with a hue. The color of the resulting coating couple is dark, while the deposit on a shiny metallic layer gives rise to lighter colors.

According to another variant of the invention, illustrated in FIGS. 3a and 3b, selective ablation is performed to obtain one or more openings 19 of specific shapes and positions. The openings 19 can be made for example by laser ablation or by any other appropriate method.

In some cases, for example when using a laser for selective ablation, the latter may include the removal of the ALD layer 12 and also the first layer 11, until the substrate is discovered. The invention is not, however, limited to this method of ablation and may also include methods in which only the ALD layer 12 is etched, for example by wet-etch, dry-etch or any other suitable method. Preferably, as will be seen later, the surface exposed by the ablation is conductive.

In a subsequent step, illustrated in FIG. 3b, the openings 19 are filled by a galvanic coating 25 deposited on the first layer 11 or on the electrically conductive substrate 10. The galvanic coating 25 does not adhere to the regions covered by the electrically insulative ALD layer 12. The coating 25 is for example a layer of gold or other material contrasting with the color of the regions covered by the ALD layer 12 in order to make a decorative pattern.

Although the examples presented refer to an oscillating weight or an element of a movement, the method of the invention allows to deposit a coating on various elements, in order to obtain particularly attractive decorative articles and having a beautiful effect. For example, a coating can be applied by the inventive method to internal components of watches such as dials, highlights, sconces, indexes, needles, screws, or external elements, for example boxes, glasses, bottoms, crowns, push buttons, links or bracelet clasps. Furthermore the method of the invention can be applied also to any other object, including leather goods and / or jewelry, and glasses, writing instruments, or portable electronic devices.

The first layer 11 and the ALD layer 12 may be deposited in two separate reactors, or in a single reactor, without departing from the scope of the invention.

Reference numbers used in the figures

[0033] <Tb> 10 <September> Substrate <tb> 11 <SEP> metal layer <tb> 12 <SEP> transparent layer <tb> 19 <SEP> selective opening <tb> 25 <SEP> galvanic layer <tb> 31 <SEP> L * (d) / 10 <Tb> 32 <September> a * (d) <Tb> 33 <September> b * (d) <tb> 36 <SEP> L * (Rh) / 10 <Tb> 37 <September> a * (Rh) <Tb> 38 <September> b * (Rh)

Claims (18)

1. Coating for the protection and / or decoration of a component of a timepiece comprising, on a substrate: a first at least partially reflective layer; an at least partially transparent second layer deposited by an ALD (Atomic Deposition) process above the first layer. 2. The coating of the preceding claim, wherein said first layer is a layer of Al, Ag, Au, Pd, or Pt, and said second layer is an ALD layer of a material of: Al2O3, TiO2, SiO2, ZnO, HfO2, SnO, Ta2O5, TiN, TaN, Si3N4, WN, NbN, Al, Ru, Ir, Pt, ZnS. The coating of one of the preceding claims, wherein the thickness of said second layer is between 40 nm and 80 nm, preferably between 50 nm and 70 nm, more preferably between 55 nm and 65 nm. 4. The coating of one of the preceding claims, wherein said first layer (11) is deposited by a PVD method (Physical Vapor Phase Deposition). 5. The coating of claim 2, wherein the thickness of said second layer is chosen so as to obtain a color for the coating characterized by: the color parameter L * according to the CIELAB standard is equal to or greater than 80; the color parameter a * according to the CIELAB standard is between 0 and 2 and the color parameter b * according to the CIELAB standard is between 4 and 0. 6. The coating of claim 2, wherein the thickness of said second layer is chosen to obtain a color substantially equivalent to that of rhodium. 7. The coating of one of claims 1 or 2, wherein the thickness of the second layer is chosen so as to obtain an interferential color in the range brown, magenta, blue, yellow, orange, purple, green, pink, according to the increasing thickness of the second layer. 8. The coating of one of the preceding claims wherein said second layer (12) has openings (19), and wherein said first layer or substrate is covered in the openings by a galvanic coating (25). . 9. A method of depositing a protective and / or decorative coating on a substrate comprising the following steps: depositing a first, at least partially reflective layer (11) on the substrate; deposition by an ALD (Atomic Deposition) process of a second at least partially transparent layer (12) above the first layer. The method of the preceding claim, wherein said first layer is a layer of Al, Ag, Au, Pd, or Pt, and said second layer is an ALD layer of one of Al2O3, TiO2, SiO2, ZnO, HfO2, SnO, Ta2O5, TiN, TaN, Si3N4, WN, NbN, Al, Ru, Ir, Pt, ZnS. 11. The method of claim 1, wherein said first layer is deposited by a PVD method. The method of one of claims 9 to 11, wherein the thickness of said second layer is between 40 nm and 80 nm, preferably between 50 nm and 70 nm, more preferably between 55 nm and 65 nm. 13. The method of one of claims 9 to 12, wherein the thickness of said second layer is chosen so as to obtain a color for the coating characterized by: the color parameter L * according to the CIELAB standard is equal to or greater than 80; the color parameter a * according to the CIELAB standard is between 0 and 2 and the color parameter b * according to the CIELAB standard is between 4 and 0. 14. The method of one of claims 9 to 11, wherein the thickness of said second layer is chosen to obtain a color substantially equivalent to that of rhodium. The method of one of claims 9 to 11, wherein the thickness of the second layer is selected to obtain an interferential color in the brown, magenta, blue, yellow, orange, purple, green, pink, according to the increasing thickness of the second layer. 16. The method of one of claims 9 to 15, comprising: partially removing said second layer to create apertures (19) in the second layer (12) in predetermined regions of the coating, exposing said first layer (11) or the substrate (10). deposition of a galvanic layer (25) on the first layer (11) or on the substrate (10) in the regions discovered during partial ablation. 17. Element for a timepiece comprising a coating according to one of claims 1 to 8. 18. Protective and / or decorative coating according to one of claims 1 to 8, deposited on a sintered tungsten substrate.