METHOD FOR DEPOSITING A COATING ON A SUBSTRATE

Abstract

A method for depositing a coating on a substrate (100), including successively depositing a thin intermetallic layer (110) on the substrate (100), so as to obtain an external part (10), and annealing the external part (10) in a dedicated enclosure.

Claims

1. A method for depositing a coating on a substrate (100), said method comprising: a step of depositing a thin intermetallic layer (110) on said substrate (100), so as to obtain an external part (10) of a timepiece, jewellery or fashion items, a step of annealing the external part (10) in a dedicated enclosure different from the enclosure wherein the deposition of the thin intermetallic layer (110) is performed.

2. The method according to claim 1, wherein the step of depositing the thin intermetallic layer (110) is performed by implementing a PVD deposition method from cathodic or ionic sputtering, thermal evaporation, arc or electron beam evaporation, or pulsed laser beam ablation.

3. The method according to claim 2, wherein the deposition of the thin layer is performed from at least one target consisting of a composite of at least two metals or of at least two targets of different pure metals.

4. The method according to claim 1, wherein the deposition step is performed so that the thin intermetallic layer (110) has a thickness between 20 and 1000 nm, preferably between 200 and 500 nm, and more preferably of 300 nm.

5. The method according to claim 1, wherein the annealing step is performed by implementing an overall annealing operation wherein the entire thin intermetallic layer (110) is heat treated.

6. The method according to claim 5, wherein the temperature to which the external part (10) is subjected during the overall annealing operation is between 200° C. and 500° C., and is preferably substantially equal to 300° C., fora duration between 30 and 120 minutes, and preferably of 60 minutes.

7. The method according to claim 1, wherein the annealing step is performed by implementing a localised annealing operation on a predetermined area (111) of the thin intermetallic layer (110).

8. The method according to claim 5, wherein the annealing step is performed by implementing a localised annealing operation on a predetermined area (111) of the thin intermetallic layer (110) after the overall annealing operation.

9. The method according to claim 7, wherein the localised annealing operation is performed by means of a laser the beam of which has a diameter between 10 μm and 100 μm.

10. The method according to claim 7, wherein the localised annealing operation is performed by means of a laser configured to emit pulses the duration of which is between 4 ns and 350 ns, of variable frequency between 10 kHz and 1 MHz.

11. The method according to claim 1, wherein the step of depositing the thin intermetallic layer (110) may be preceded by a surface structuring step wherein the surface (112) of the substrate (100) is structured.

12. The method according to claim 11, wherein only one portion of the surface (112) of the substrate (100) is structured, the structured portion (113) corresponding to a predetermined area (111) of the thin intermetallic layer (110) subjected to a localised annealing operation.

13. The method according to claim 11, wherein the surface structuring is performed on the entire surface (112) of the substrate (100).

14. The method according to claim 1, further comprising, after the step of depositing the thin intermetallic layer (110) and the step of overall and/or localised annealing, a step of depositing a protective layer (120).

15. The method according to claim 14, wherein during the step of depositing a protective layer (120), the thin intermetallic layer (110) is covered by a stack of thin dielectric layers and/or by a translucent polymer layer.

16. The method according to claim 15, wherein the composition and the thickness of the thin dielectric layers of the protective stack (120) are specifically selected to conserve the original colour of the thin intermetallic layer (110) or to advantageously modify the colour of the thin intermetallic layer (110) in a chosen direction.

17. A timepiece component comprising a substrate (100), wherein said substrate (100) comprises a coating deposited by implementing a method according to claim 1, said component having a predetermined final colour.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0042] Other features and advantages of the invention will become apparent upon reading the following detailed description given by way of non-limiting example, with reference to the drawing of FIG. 1 schematically showing a sectional view of a timepiece component, such as an external part of a timepiece, including a substrate comprises a coating deposited by implementing a method for depositing an intermetallic layer according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0043] The present invention relates to a method for depositing a coating on a substrate 100, said method including a step of depositing a thin intermetallic layer 110 on the substrate 100 so as to obtain an external part 10 of a timepiece, jewellery or fashion items. In particular, such an external part 10 may advantageously form a timepiece component.

[0044] The substrate 100 may be produced in any suitable material, such as in metallic material, ceramic, etc.

[0045] The method includes a step of depositing a thin intermetallic layer 110 on the substrate 100, followed by a step of annealing said external part 10 in a dedicated enclosure, so that the external part 10 has a predetermined final colour.

[0046] The step of depositing the thin intermetallic layer 110 is performed by implementing a PVD deposition method and more particularly by implementing one of the following methods: ionic or cathodic sputtering, thermal evaporation, arc or electron beam evaporation, or pulsed laser beam ablation.

[0047] The deposition of the thin intermetallic layer 110 is performed from at least two targets each consisting of a specific metal and/or from at least one target consisting of a composite of at least two metals.

[0048] Preferably, to simplify the implementation of the step of depositing the thin intermetallic layer 110, it is produced from a target consisting of a composite of at least two metals. Moreover, the results obtained during tests demonstrate that the composition of the thin intermetallic layer 110 is more reproducible when the step of depositing the thin intermetallic layer 110 is implemented from a single target consisting of a metal composite.

[0049] By way of non-limiting example, the metals used are selected from Pt, Al, Cu, In and Au, or from composites of these metals.

[0050] More specifically, the metals are for example selected so that the thin intermetallic layer 110 includes an Au—Al, Au—In, Pt—Al, or Pt—Al—Cu intermetallic combination.

[0051] The deposition step is performed so that the thin intermetallic layer 110 measures between 20 and 1000 nm of thickness, preferably between 200 and 500 nm, and more preferably 300 nm. Thus, the thin intermetallic layer 110 is advantageously opaque and has a good compromise between a thickness thick enough in order that the thin intermetallic layer 110 is adapted to withstand mechanical stresses that it is likely to undergo, and a thickness thin enough in order that the consumption of noble metals and that the duration for depositing the thin intermetallic layer 110 are not too high.

[0052] The deposition method is implemented so that the thin intermetallic layer 110 has a mainly amorphous phase after its deposition.

[0053] The parameters of the PVD deposition method, particularly the powers applied simultaneously on the various sources, are selected so that the thin intermetallic layer 110 obtained has a composition that has a desired final colour after the annealing step.

[0054] By way of non-limiting example, the thin metallic layer 110 may be made of Pt—Al—Cu composite the composition of which is Pt 61.7% by weight, Al 18.3% by weight, Cu 20.0% by weight, the deposition step of which being performed by cathodic co-sputtering from 3 pure Pt, Al and Cu targets. At the end of the deposition step, the thin intermetallic layer 110 is not very crystallised and has a colour characterised by the parameters (L*, a*, b*)=(77.5, 1.9, 2.6). Therefore, it has a very slightly pinky grey colour but without significant aesthetic advantage. After the annealing step, performed in a vacuum tube furnace at 500° C. for 2 hours, the layer crystallises so as to have a colour characterised by the parameters (L*, a*, b*)=(78.2, 10.8, 20.8). It then has a very strong and aesthetically advantageous final pinky-orange colour.

[0055] The annealing step is advantageously performed in a dedicated enclosure, different from the enclosure wherein the deposition of the thin intermetallic layer 110 is performed, that is to say different from the deposition chamber wherein the PVD deposition is performed.

[0056] The annealing step has the effect of modifying the phase of the thin intermetallic layer 110, by making it change from a mainly amorphous phase to a crystalline phase.

[0057] This solution of the present invention has the advantage of being able to be implemented by using standard equipment found on the market, and not requiring the production of expensive specific equipment for annealing the layer in situ. Furthermore, the annealing step may be performed simultaneously for a large number of external parts 10 in the same enclosure, which tends to reduce the duration of performing the method for each external part 10 and the manufacturing costs.

[0058] The annealing step may be performed by implementing an overall annealing operation wherein the entire thin intermetallic layer 110, and consequently the entire external part 10, is heat treated.

[0059] In the case of the overall annealing operation, the dedicated enclosure consists of a furnace.

[0060] The overall annealing operation is preferably carried out in a furnace in a controlled atmosphere, for example in argon or nitrogen. Alternatively, the overall annealing operation is carried out in a vacuum, the working pressure being located for example between 10.sup.−6 and 10.sup.−2 mbar, and preferably at 10.sup.−4 mbar.

[0061] The temperature to which the external part 10 is subjected during the overall annealing operation is for example between 200° C. and 500° C., and is preferably substantially equal to 300° C. The duration of the overall annealing operation is for example between 30 and 120 minutes, and is preferably of 60 minutes.

[0062] Alternatively, the annealing step may be performed by implementing a localised annealing operation on a predetermined area 111 of the thin intermetallic layer 110.

[0063] The localised annealing operation may be performed on the thin intermetallic layer 110 directly after its deposition, that is to say when it has a mainly amorphous phase, or after the overall annealing operation, wherein the annealing is performed on the entire external part 10.

[0064] This localised annealing step has the effect of locally modifying the colour of the thin intermetallic layer 110, in order to generate a decoration, for example in the form of indexes of dials, digits, logos, etc.

[0065] The localised annealing operation is performed with the aid of a laser the beam of which may have a diameter for example between 10 μm and 100 μm, or even between 50 μm and 100 μm. The movement of the laser beam is advantageously controlled by a scanning system specific to the laser and based on mechanical or optical axes or by a scanning system specific to the substrate based on mechanical axes providing a high precision of the position of the point of impact of the laser beam on the thin intermetallic layer 110.

[0066] The laser beam has the effect of generating locally, at the point of impact with the thin intermetallic layer 110, a local rise of the temperature resulting in a local change of phase of said thin intermetallic layer 110, and consequently in a local change of colour.

[0067] The laser beam may be generated by a nanosecond pulsed or microsecond pulsed laser, or optionally by a continuous laser.

[0068] More specifically, during the localised annealing step, the laser may emit pulses of a duration between 4 ns and 350 ns, of variable frequency between 10 kHz and 1 MHz, and that may reach an average power in the order of 40 W.

[0069] Alternatively, the localised annealing step may also be implemented by using picosecond or femtosecond pulsed lasers, by using the heat accumulation effect at high rate in frequencies ranging from 100 to 200 kHz up to 10 MHz, or pulse series in bursts, as known by the person skilled in the art, spaced apart from one another from a few picoseconds to a few nanoseconds.

[0070] The wavelength of the laser beam is determined so as to favour the absorbance of the material of the thin intermetallic layer 110 that the beam is intended to impact.

[0071] By way of example, the laser beam may have a wavelength in the infra-red spectrum, in the visible spectrum or in the ultraviolet spectrum.

[0072] During the localised annealing step, the variation of the energy of the pulses of the laser beam, their repetition frequency as well as their degree of superposition result in modifying the colour of the intermetallic layer 110.

[0073] It is thus possible to create multicoloured or contrasted decorations based on a single deposition of thin intermetallic layer 110 of homogeneous composition.

[0074] Advantageously, the steps of depositing and annealing the thin intermetallic layer may be preceded by a step of structuring the surface 112 of the substrate 100 wherein a portion of the surface 112 of the substrate 100 is structured, and is called “structured portion 113” in the remainder of the text, so as to generate a surface structure contrast on said surface 112.

[0075] The structured portion 113 of the surface 112 of the substrate 100 may correspond to the predetermined area 111 of the intermetallic layer 110 that is subjected to the heat treatment during the localised annealing operation. This has the advantageous effect of reinforcing the difference between the visual appearance of said predetermined area 111 and that of the rest of the thin intermetallic layer 110.

[0076] Alternatively, in an alternative embodiment of the invention, the structuring is performed on the entire surface 112 of the substrate 100.

[0077] Such a surface structuring step may consist for example in polishing, matt finishing or satin finishing partially or totally the surface 112 of the substrate 100, according to the alternative embodiment considered.

[0078] In order to facilitate the localised annealing step and reduce the local contribution of heat needed to carry out the phase transformation of the thin intermetallic layer, the external part 10 may be preheated to a temperature that is close to the phase transition temperature. Thus the supplementary energy contribution by laser may be reduced.

[0079] Advantageously, the thin intermetallic layer 110 obtained after the deposition step may be covered with a protective layer 120, for example formed by a stack of thin dielectric layers intended to protect the thin intermetallic layer 110 against environmental hazards, during a subsequent deposition step that may advantageously be performed with the same deposition equipment as that used to implement the step for depositing the thin intermetallic layer 110. This stack of thin dielectric layers may also have the effect of modifying the visual appearance of the external part 10, for example by increasing the brightness thereof, and/or by modifying the colour of the intermetallic layer 110 by an advantageous interference effect.

[0080] The step of depositing a protective layer 120 is advantageously the last step of the method according to the invention.

[0081] The stack of thin dielectric layers may be formed of various oxides, nitrides, oxynitrides, such as TiO.sub.2, Al.sub.2O.sub.3, SiO.sub.2, SiN, Si3N4, and may be deposited by an ALD and/or PVD and/or CVD deposition method.

[0082] Alternatively, the step of depositing a protective layer 120 may consist in depositing a varnish layer, for example a polymer varnish layer of the zapon or parylene type.

[0083] Globally, if the method according to the invention includes all of the aforementioned steps, they are implemented successively by starting with the step of structuring the surface of the substrate 100, then the step of depositing the thin intermetallic layer 110 is performed, followed by the overall annealing step and/or the localised annealing step, and finally the step of depositing the protective layer 120.

[0084] The invention thus proposes a solution for the use of intermetallic compounds, particularly based on noble metals, offering a wide range of new colours for aesthetic applications in watchmaking, jewellery and any other luxury product.

[0085] More generally, it should be noted that the implementations and embodiments considered above have been described by way of non-limiting examples, and that other variants are consequently possible.