CH719291A2 - Method of depositing a coating on a substrate. - Google Patents

Abstract

The invention relates to a method for depositing a coating on a substrate (100), said method being characterized in that it comprises successively: - a step of depositing a thin intermetallic layer (110) on said substrate (100 ), so as to obtain a covering part (10), – a step of annealing the covering part (10) in a dedicated enclosure.

Description

Technical field of the invention

The invention relates to the field of materials, and in particular materials defining the external appearance of trim parts for watches, jewelry, fashion items, or more generally various objects.

More particularly, the invention relates to a process for depositing a coating on a substrate.

Technology background

[0003] The deposits of thin layers under a controlled atmosphere are commonly used in industry in general and in the watchmaking and jewelery fields in particular, to produce coatings with aesthetic and/or technical applications.

[0004] For aesthetic applications, the thin layers deposited can be composed of noble metals, such as gold (Au) and silver (Ag), or noble metal alloys. These noble metal alloys are often composed of a combination of gold, silver and copper (Cu), possibly with additions of platinum (Pt) or other related metals. In these alloys of noble metals, the atoms form metallic bonds which are at the origin of the color of the alloy and its malleability.

[0005] Among the thin film deposition methods commonly used are physical vapor deposition methods (known by the acronym in English "PVD", for "Physical Vapor Deposition") comprising in particular the sputtering method and evaporation methods; chemical vapor deposition methods (known by the sign in English “CVD” for “Chemical Vapor Deposition”); metal deposition methods by galvanic growth; and atomic thin layer deposition methods (known by the acronym “ALD”, for “Atomic Layer Deposition”).

[0006] There are also intermetallic compounds, in particular of noble metals, offering a wider range of colors compared to the aforementioned standard noble alloys. For example, the intermetallic compounds Pt-Al yellow, Pt-Al-Cu orange or pink, Au-Al blue, Au-In purple.

[0007] In these intermetallic compounds, the atoms form strong covalent bonds which are at the origin of the particular colors of these compounds, but which make them hard and brittle in their massive form. These intermetallic compounds are therefore difficult to exploit and actually little exploited in their massive form because they are not very malleable and difficult to shape.

[0008] These intermetallic compounds can nevertheless be used in the form of more or less thin layers by implementing one of the aforementioned methods of depositing thin layers under vacuum.

For example, these deposition methods can be implemented to deposit thin layers of intermetallic compounds formed from metals such as Au, Al, Cu, In or Pt, such as AuAl2 or PtAl2 compounds.

[0010] Nevertheless, the thin layers of intermetallic compounds deposited by these methods are out of thermodynamic equilibrium and present a mainly amorphous phase which does not have the desired color that said intermetallic compounds of the same compositions have in their massive and crystalline form, but typically a gray color without any particular aesthetic interest.

[0011] Indeed, the thermodynamic state of the intermetallic compounds, and in particular their crystallinity and/or the presence of different phases, has a major impact on their color for a given composition.

[0012] A step of annealing the layer in situ during the deposition process, typically at 400° C., is therefore implemented to cause at least partial crystallization of the layer of intermetallic compound thus deposited and to obtain the coloring of the layer which is specific to the crystalline phase of said intermetallic compound for the given composition.

[0013] Thin layers of intermetallic compounds remain in practice very little used insofar as, although they offer interesting alternatives in terms of choice of colors compared to thin layers of standard noble alloys, the implementation of the method for depositing them is long and complex due to the need to perform in situ annealing of the thin layers.

Summary of the invention

The present invention solves the aforementioned drawbacks.

[0015] To this end, the invention relates to a process for depositing a coating on a substrate, comprising successively: - a step of depositing a thin layer formed of an intermetallic compound on said substrate, so as to obtain a trim part, – an annealing step for the trim part in a dedicated enclosure.

[0016] Compared to the state of the prior art where the annealing is carried out in situ during the deposition of the thin layer, the invention offers the advantage of being able to treat a large number of substrates simultaneously, for example in a large oven, and therefore reduce the process time per part. This approach also allows the use of thin layer deposition methods which do not allow in situ annealing, at least not without making the process and/or the equipment prohibitively complex.

[0017] In particular embodiments, the invention may also comprise one or more of the following characteristics, taken in isolation or in all technically possible combinations.

[0018] In particular embodiments, the step of depositing the thin intermetallic layer is carried out by implementing a PVD deposition method from among cathode or ion sputtering, thermal evaporation, evaporation by electron beam or by arc, or ablation by pulsed laser beam.

In particular modes of implementation, the deposition of the thin layer is carried out from at least one target composed of an alloy of at least two metals or of at least two targets of different pure metals. . In the case of the use of targets of pure metals, the deposition of the thin layer is carried out by cathodic co-sputtering (known under the term "cosputtering"), that is to say by simultaneous cathodic sputtering at least two targets of different pure metals, the intermetallic compound then forming at the meeting of the at least two flows of atoms on the substrate. The powers applied to the at least two targets are chosen independently so that the sputtering rates of the at least two different metals result in the desired layer composition. Nevertheless, the metal deposition rate varies according to the wear of the corresponding targets and the composition of the layer consequently drifts as said targets are mined. These deposition rate variations can be compensated by a correction of the power applied to each of the targets according to their wear, either manually on the basis of a calibration table, or automatically thanks to a feedback loop based on a measurement. in situ (for example, a spectral measurement of the optical emission of the plasma in the case of sputtering).

In the case of the use of an alloy target, the composition of said target is chosen so as to directly obtain the desired layer composition on the substrate, with the advantage of not depending on the wear of said allied target.

In particular embodiments, the deposition step is carried out so that the thin intermetallic layer has a thickness between 20 and 1000 nm, preferably between 200 and 500 nm, and more preferably 300 nm .

In particular modes of implementation, the annealing step is carried out by the implementation of an overall annealing operation in which the whole of the intermetallic thin layer is heat treated in order to crystallize it and to impart an expected color.

In particular embodiments, the temperature to which the covering part is subjected during the global annealing operation is between 200° C. and 500° C., and is preferably substantially equal to 300 ° C, for a time between 30 and 120 minutes, and preferably 60 minutes.

[0024] In particular embodiments, the overall annealing step is carried out in a conventional furnace under an ambient atmosphere, preferably under a protective atmosphere of an inert gas, i.e. argon (Ar), or under vacuum in order to avoid any chemical interaction between the thin intermetallic layer and the atmosphere.

[0025] In particular embodiments, the annealing step is carried out by implementing a localized annealing operation on a predetermined zone of the thin intermetallic layer. A color contrast is thus obtained between the non-annealed, amorphous and gray zone, and the annealed, crystallized and colored zone.

In particular embodiments, the annealing step is carried out by implementing the localized annealing operation following the global annealing operation.

In particular embodiments, the localized annealing operation is carried out by means of a laser, the beam of which has a diameter of between 10 μm and 100 μm, or even between 50 μm and 100 μm.

In particular modes of implementation, the localized annealing operation is carried out by means of a laser configured to emit pulses whose duration is between 4 ns and 350 ns, of variable frequency between 10 kHz and 1MHz.

In particular embodiments, the localized annealing operation is carried out in an ambient atmosphere, preferably in a chamber under a protective atmosphere of an inert gas, i.e. argon (Ar), or under vacuum in order to avoid any chemical interaction between the thin intermetallic layer and the atmosphere.

In particular embodiments, the step of depositing the thin layer can be preceded by a step of surface structuring in which the surface of the substrate is structured, for example on only one part.

In particular embodiments, the part of the surface of the structured substrate corresponds to the predetermined zone subjected to the localized annealing operation, a surface appearance contrast then being added to the color contrast to an advantageous aesthetic effect.

[0032] In particular embodiments, the structuring is carried out over the entire surface of the substrate which will be covered by the thin intermetallic layer.

In particular embodiments, the method comprises, following the step of depositing a thin intermetallic layer and the step of global and/or localized annealing, a step of depositing a layer for protecting the thin intermetallic layer against attacks from the environment, in which the thin intermetallic layer is covered with a stack of thin dielectric layers deposited by one or more vacuum deposition methods, such as by PVD, CVD or ALD.

In particular embodiments, the thicknesses and compositions of the thin dielectric layers forming the protective stack are chosen so that the interference optical effects of said thin dielectric layers compensate for the purpose of retaining the color. original of the thin intermetallic layer.

In particular embodiments, the thicknesses and compositions of the thin dielectric layers forming the protective stack are chosen so that the optical interference effects of said thin dielectric layers modify the color of the thin intermetallic layer of aesthetically advantageous way, for example by increasing the saturation of the color or correcting the hue in a chosen direction.

In particular embodiments, the protective layer is a layer of translucent polymer deposited by spraying or any other method known to those skilled in the art.

In particular embodiments, the protective layer is a composite layer with combinations of polymer and dielectric layers deposited by techniques known to those skilled in the art.

The invention also relates, according to another aspect, to a timepiece component comprising a substrate comprising a coating deposited by implementing the aforementioned method.

Brief description of figures

[0039] Other characteristics and advantages of the invention will become apparent on reading the following detailed description given by way of non-limiting example, with reference to the drawing of FIG. 1 schematically representing a sectional view of a watch component , such as a trim part, comprising 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

The present invention relates to a process for depositing a coating on a substrate 100, said process comprising a step of depositing a thin intermetallic layer 110 on the substrate 100 so as to obtain a trim part 10.

The substrate 100 can be made of any suitable material, such as metal, ceramic, etc.

The method includes a step of depositing a thin intermetallic layer 110 on the substrate 100, followed by a step of annealing said trim part 10 in a dedicated enclosure.

The step of depositing the thin intermetallic layer 110 is carried out by implementing a PVD deposition method and more particularly by implementing one of the following methods: cathode or ion sputtering, thermal evaporation , evaporation by electron beam or by arc, or ablation by pulsed laser beam.

The deposition of the thin intermetallic layer 110 is made from at least two targets each composed of a clean metal and / or from at least one target composed of an alloy of at least two metals .

Preferably, to simplify the implementation of the step of depositing the thin intermetallic layer 110, the latter is made from a target composed of an alloy of at least two metals. Furthermore, the results obtained during tests show 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 composed of an alloy of metals.

By way of non-limiting example, the metals used are chosen from Pt, Al, Cu, In and Au, or from alloys of these metals.

More specifically, the metals are for example chosen so that the thin intermetallic layer 110 comprises an Au-Al, Au-In, Pt-Al or Pt-Al-Cu intermetallic combination.

The deposition step is carried out so that the thin intermetallic layer 110 measures between 20 and 1000 nm in thickness, preferably between 200 and 500 nm, and more preferably 300 nm. Thus, the thin intermetallic layer 110 is advantageously opaque and presents a good compromise between a sufficiently large thickness for the thin intermetallic layer 110 to be adapted to resist the mechanical stresses that it is likely to undergo, and a sufficiently small thickness so that the consumption of noble metals and that the deposition time of the thin intermetallic layer 110 are not too high.

The deposition process is implemented so that the thin intermetallic layer 110 has an amorphous phase following its deposition.

The parameters of the PVD deposition method, in particular the powers applied simultaneously to the different sources, are chosen so that the thin intermetallic layer 110 obtained has a composition which exhibits a desired color after the annealing step.

By way of non-limiting example, a Pt-Al-Cu intermetallic thin layer can be deposited by cathodic co-sputtering from 3 targets of pure Pt, Al and Cu whose composition is Pt 61.7% by mass , Al 18.3% by mass, Cu 20.0% by mass. On leaving the deposit, the thin intermetallic layer is weakly crystallized and its color is measured at (L*, a*, b*) = (77.5, 1.9, 2.6). It therefore has a very slightly pinkish gray color but without much aesthetic advantage. After annealing in a vacuum tube oven at 500° C. for 2 hours, the layer crystallizes and takes on a color measured at (L*, a*, b*) = (78.2, 10.8, 20.8). It then presents a very intense and aesthetically advantageous pinkish-orange color.

The annealing step is advantageously carried out in a dedicated enclosure, different from the enclosure in which the deposition of the thin intermetallic layer 110 is carried out, that is to say different from the deposition chamber in which is carried out the PVD deposit.

The annealing step has the effect of modifying the phase of the thin intermetallic layer 110, by changing it from an amorphous phase to a crystalline phase.

This solution of the present invention has the advantage of being able to be implemented by the use of standard equipment found on the market, and of not requiring the production of specific expensive equipment for the annealing of the layer in situ. In addition, the annealing step can be carried out simultaneously for a large number of covering parts 10 in the same enclosure, which tends to reduce the duration of carrying out the process per covering part 10 and the costs of manufacturing.

The annealing step can be carried out by implementing an overall annealing operation in which the whole of the thin intermetallic layer 110, and consequently the whole of the covering part 10, is heat treated.

In the case of the global annealing operation, the dedicated enclosure is formed by a furnace.

The overall annealing operation is preferably carried out in a furnace under a controlled atmosphere, for example under argon or nitrogen. Alternatively, the global annealing operation is carried out under vacuum, the working pressure being for example between 10<-6> and 10<-2> mbar, and preferably at 10<-4> mbar.

The temperature to which the covering part 10 is subjected during the global 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 60 minutes.

Alternatively, the annealing step can be performed by implementing a localized annealing operation on a predetermined zone 111 of the thin intermetallic layer 110.

The localized annealing operation can be carried out on the thin intermetallic layer 110 directly following its deposition, that is to say when it has an amorphous phase, or following the global annealing operation. , in which the annealing is carried out on the whole of the covering part 10.

This localized annealing step has the effect of locally modifying the color of the thin intermetallic layer 110, in order to generate a decoration, for example in the form of dial indexes, numerals, logos, etc.

The localized annealing operation is carried out using 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 displacement of the laser beam is advantageously controlled by a scanning system specific to the laser and based on mechanical or optical axes providing high precision of the position of the point of impact of the laser beam on the thin intermetallic layer 110.

The laser beam has the effect of generating locally, at the point of impact with the thin intermetallic layer 110, a local rise in temperature leading to a local phase change of said thin intermetallic layer 110, and consequently to a local color change.

The laser beam can be generated by a laser with nanosecond pulses or with microsecond pulses, or optionally by a continuous laser.

More specifically, during the localized annealing step, the laser can emit pulses with a duration of between 4 ns and 350 ns, of variable frequency between 10 kHz and 1 MHz, and which can reach an average power around 40 W.

Alternatively, the localized annealing step can also be implemented using picosecond or femtosecond pulsed lasers, using the high-speed thermal accumulation effect in frequencies ranging from 100 to 200 kHz up to at 10 MHz, or series of pulses in bursts (known by those skilled in the art by the term “bursts” in English) spaced from each other by a few picoseconds to a few nanoseconds.

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

By way of example, the laser beam may have a wavelength comprised in the infrared spectrum, in the visible spectrum or in the ultraviolet spectrum.

During the localized annealing step, the variation in the energy of the pulses of the laser beam, their repetition frequency and their degree of superposition result in modifying the color of the intermetallic layer 110.

It is thus possible to create multicolored or contrasting decorations on the basis of a single deposition of a thin intermetallic layer 110 of homogeneous composition.

Advantageously, the steps of deposition and annealing of the thin intermetallic layer can be preceded by a step of structuring the surface 112 of the substrate 100 in which part of the surface 112 of the substrate 100 is structured, and is called "structured part 113" in the following text, so as to generate a surface structure contrast on said surface 112.

The structured part 113 of the surface 112 of the substrate 100 can correspond to the predetermined zone 111 of the intermetallic layer 110 which is subjected to the heat treatment during the localized 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.

Alternatively, in a variant embodiment of the invention, the structuring is carried out over the entire surface 112 of the substrate 100.

Such a surface structuring step may consist, for example, in polishing, mattifying or satin-finishing partially or totally the surface 112 of the substrate 100, depending on the variant embodiment considered.

[0075] In order to facilitate the localized annealing step and to reduce the local heat input necessary to perform the phase transformation of the thin intermetallic layer, the covering part 10 can be preheated to a temperature which approaches of the phase transition temperature.

Advantageously, the thin intermetallic layer 110 obtained after the deposition step can 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 attack. , during a subsequent deposition step which can advantageously be carried out with the same deposition equipment as that used to implement the step of depositing the thin intermetallic layer 110. This stack of thin dielectric layers can also have the effect of modify the visual appearance of the covering part 10, for example to increase its shine, and/or to modify the color of the intermetallic layer 110 by an advantageous interference effect.

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

The stack of thin dielectric layers can be formed from different oxides, nitrides, oxy-nitrides, such as TiO2, Al2O3, SiO2, SiN, Si3N4, and can be deposited by an ALD and/or PVD deposition method. and/or CVD.

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

Overall, if the method according to the present invention comprises all of the aforementioned steps, they are implemented successively, starting with the step of structuring the surface of the substrate 100, then the step of depositing the thin layer intermetallic layer 110 is carried out, followed by the global annealing step and/or the localized annealing step, and finally by the step of depositing the protective layer 120.

The invention thus proposes a solution for the use of intermetallic compounds, in particular based on noble metals, offering a wide range of new colors for aesthetic applications in watchmaking, jewelery and any other luxury product.

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

Claims (17)

1. Method for depositing a coating on a substrate (100), said method being characterized in that it comprises successively: – a step of depositing a thin intermetallic layer (110) on said substrate (100), so as to obtain a covering part (10), – a step of annealing the covering part (10) in a dedicated enclosure. 2. Method according to claim 1, in which the step of depositing the thin intermetallic layer (110) is carried out by implementing a PVD deposition method from cathode or ion sputtering, thermal evaporation, evaporation by electron beam or by arc, or ablation by pulsed laser beam. 3. Method according to claim 2, in which the deposition of the thin layer is carried out from at least one target composed of an alloy of at least two metals or of at least two targets of different pure metals. 4. Method according to one of claims 1 to 3, in which the deposition step is carried out so that the thin intermetallic layer (110) has a thickness of between 20 and 1000 nm, preferably between 200 and 500 nm, and more preferably 300 nm. 5. Method according to one of claims 1 to 4, in which the annealing step is carried out by implementing an overall annealing operation in which the whole of the thin intermetallic layer (110) is heat treated . 6. Method according to claim 5, in which the temperature to which the covering part (10) is subjected during the global annealing operation is between 200° C. and 500° C., and is preferably substantially equal to 300° C., for a time comprised between 30 and 120 minutes, and preferably 60 minutes. 7. Method according to one of claims 1 to 4, in which the annealing step is carried out by implementing a localized annealing operation on a predetermined zone (111) of the thin intermetallic layer (110). 8. Process according to claims 5 and 7, in which the annealing step is carried out by carrying out the localized annealing operation following the global annealing operation. 9. Method according to one of Claims 7 or 8, in which the localized annealing operation is carried out by means of a laser, the beam of which has a diameter of between 10 μm and 100 μm. 10. Method according to one of claims 7 to 9, in which the localized annealing operation is carried out by means of a laser configured to emit pulses whose duration is between 4 ns and 350 ns, of variable frequency between 10 kHz and 1 MHz. 11. Method according to one of claims 1 to 10, in which the step of depositing the thin intermetallic layer (110) can be preceded by a step of surface structuring in which the surface (112) of the substrate (100 ) is structured. 12. Method according to claim 11 and one of claims 7 to 10, in which only part of the surface (112) of the substrate (100) is structured, the structured part (113) corresponding to the predetermined area (111) of the thin intermetallic layer (110) subjected to the localized annealing operation. 13. Method according to claim 11, in which the surface structuring is carried out over the entire surface (112) of the substrate (100). 14. Method according to one of claims 1 to 13, comprising, following the step of depositing a thin intermetallic layer (110) and the step of global and/or localized annealing, a step of depositing a protective layer (120). 15. Method according to claim 14, in which during the step of depositing a protective layer (120), the thin intermetallic layer (110) is covered with a stack of thin dielectric layers and/or with a translucent polymer layer. 16. Method according to claim 15, in which the composition and the thickness of the thin dielectric layers of the protective stack (120) are specifically chosen to preserve the original color of the thin intermetallic layer (110) or to advantageously modify the color of the thin intermetallic layer (110) in a chosen direction. 17. Watch component comprising a substrate (100), characterized in that said substrate (100) comprises a coating deposited by implementing a method according to one of claims 1 to 16.