SUBSTRATE COMPRISING A SILVER-PLATED SURFACE PROTECTED AGAINST SILVER TARNISHING AND METHOD FOR MANUFACTURING SUCH A SUBSTRATE

Abstract

A substrate includes a final silver-plated surface protected against silver tarnishing by a protective coat having a thickness between 1 nm and 200 nm, the protective coat includes a first coat of Al.sub.2O.sub.3 deposited on said final silver-plated surface and having a thickness between 0.5 nm and 100 nm, and on the first coat of Al.sub.2O.sub.3, a second coat of TiO.sub.2 having a thickness between 0.5 nm and 100 nm, the substrate including a coat of a silver and copper alloy comprising between 0.1% and 10% by weight of copper with respect to the total weight of the alloy, forming said final silver-plated surface, said coat of a silver and copper alloy having a thickness between 1000 nm and 3000 nm. Embodiments also relate to a method for manufacturing such a substrate.

Claims

1-37. (canceled)

38: A substrate comprising a final silver-plated surface protected against silver tarnishing by a protective coat having a thickness between 1 nm and 200 nm, preferably between 1 nm and 100 nm, said protective coat comprises a first coat of Al.sub.2O.sub.3 deposited on said final silver-plated surface and having a thickness between 0.5 nm and 100 nm, preferably between 0.5 nm and 50 nm and on the first coat of Al.sub.2O.sub.3, a second coat of TiO.sub.2 having a thickness between 0.5 nm and 100 nm, preferably between 0.5 nm and 50 nm, the substrate being characterised in that it comprises a coat of a silver and copper alloy comprising between 0.1% and 10% by weight of copper with respect to the total weight of the alloy, forming said final silver-plated surface, said coat of a silver and copper alloy having a thickness between 1000 nm and 3000 nm.

39: A substrate comprising a final silver-plated surface protected against silver tarnishing by a protective coat having a thickness between 1 nm and 200 nm, preferably between 1 nm and 100 nm, said protective coat comprises a first coat of Al.sub.2O.sub.3 deposited on said final silver-plated surface and having a thickness between 0.5 nm and 100 nm, preferably between 0.5 nm and 50 nm and on the first coat of Al.sub.2O.sub.3, a second coat of TiO.sub.2 having a thickness between 0.5 nm and 100 nm, preferably between 0.5 nm and 50 nm, characterised in that said substrate comprises a coat of substantially pure silver forming said final silver-plated surface, said coat of substantially pure silver having a thickness between 1000 nm and 3000 nm.

40: The substrate according to claim 38, wherein the first coat of Al.sub.2O.sub.3 has a thickness between 30 nm and 50 nm and in that the second coat of TiO.sub.2 has a thickness between 10 nm and 50 nm.

41: The substrate according to claim 38, wherein the protective coat has been deposited by ALD.

42: The substrate according to claim 38, wherein it is based on silver.

43: The substrate according to claim 38, wherein it is not based on silver.

44: The substrate according to claim 38, wherein said substrate has no initial silver-plated surface and in that it comprises, between said substrate and said coat of silver and copper alloy, a coat of substantially pure silver.

45: The substrate according to claim 39, wherein the coat of substantially pure silver has a thickness between 1500 nm and 2500 nm.

46: The substrate according to claim 38, wherein the silver and copper alloy comprises between 0.2% and 8% by weight, preferably between 0.5% and 7% by weight, of copper with respect to the total weight of the alloy.

47: The substrate according to claim 38, wherein the substrate is a horological element.

48: The substrate according to claim 38, wherein it has a surface structuring.

49: A method for manufacturing a substrate comprising a final silver-plated surface protected against silver tarnishing by a protective coat, wherein said method comprises the following steps: a) obtaining a substrate having a final silver-plated surface b) depositing on at least a part of said final silver-plated surface from step a) at least one protective coat against silver tarnishing having a thickness between 1 nm and 200 nm, preferably between 1 nm and 100 nm, said step b) comprising a first step b1) of depositing, on at least a part of said final silver-plated surface from step a), a first coat of Al2O3 having a thickness between 0.5 nm and 100 nm, preferably between 0.5 nm and 50 nm, and a second step b2) of depositing, on the first coat of Al.sub.2O.sub.3 obtained in step b1), a second coat of TiO2 having a thickness between 0.5 nm and 100 nm, preferably between 0.5 nm and 50 nm, characterised in that the method comprises a step a1) of depositing on said substrate a coat of a silver and copper alloy comprising between 0.1% and 10% by weight of copper with respect to the total weight of the alloy to obtain said final silver-plated surface, said coat of a silver and copper alloy having a thickness between 1000 nm and 3000 nm.

50: A method for manufacturing a substrate comprising a final silver-plated surface protected against silver tarnishing by a protective coat, wherein said method comprises the following steps: a) obtaining a substrate having a final silver-plated surface b) depositing on at least a part of said final silver-plated surface from step a) at least one protective coat against silver tarnishing having a thickness between 1 nm and 200 nm, preferably between 1 nm and 100 nm, said step b) comprising a first step b1) of depositing, on at least a part of said final silver-plated surface from step a), a first coat of Al.sub.2O.sub.3 having a thickness between 0.5 nm and 100 nm, preferably between 0.5 nm and 50 nm, and a second step b2) of depositing, on the first coat of Al.sub.2O.sub.3 obtained in step b1), a second coat of TiO.sub.2 having a thickness between 0.5 nm and 100 nm, preferably between 0.5 nm and 50 nm, characterised in that the method comprises a step a3) of depositing a coat of substantially pure silver on said substrate to obtain said final silver-plated surface, the coat of substantially pure silver having a thickness between 1000 nm and 3000 nm.

51: The method according to claim 49, wherein the first coat of Al.sub.2O.sub.3 has a thickness between 30 nm and 50 nm and in that the second coat of TiO.sub.2 has a thickness between 10 nm and 50 nm.

52: The method according to claim 49, wherein step b) is carried out by means of a method selected from the group comprising an ALD, PVD, CVD, and sol-gel deposition.

53: The method according to claim 52, wherein step b) is carried out by ALD deposition.

54: The method according to claim 49, wherein it comprises, before and/or after step b2), a plasma treatment step.

55: The method according to claim 49, wherein it comprises, between step a) and step b), at least one plasma pre-treatment step c) of the final silver-plated surface of the substrate obtained in step a)

56: The method according to claim 55, wherein the plasma pre-treatment step c) consists of an Ar plasma or Ar/H.sub.2 plasma pre-treatment.

57: The method according to claim 55, wherein step c) is carried out without venting the final silver-plated surface of the substrate between step c) and said step b).

58: The method according to claim 55, wherein it comprises, between step c) and step b), an oxidising pre-treatment step d).

59: The method according to claim 58, wherein the oxidising pre-treatment step d) consists of a plasma pre-treatment with an oxidising agent.

60: The method according to claim 58, wherein the oxidising pre-treatment step d) consists of injecting water or hydrogen peroxide, in liquid form, into a pre-treatment chamber in a vacuum.

61: The method according to claim 58, wherein step d) is carried out without venting the final silver-plated surface of the substrate between step c) and said step d).

62: The method according to claim 58, wherein step b) is carried out without venting the final silver-plated surface of the substrate between step d) and said step b).

63: The method according to claim 62, wherein steps c), d) and b) are implemented in the same overall treatment machine.

64: The method according to claim 49, wherein the substrate from step a) has no initial silver-plated surface, and in that said method comprises an intermediate step a2) of depositing a coat of substantially pure silver between said substrate and the coat of silver and copper alloy.

65: The method according to claim 49, wherein it comprises, before at least one of steps a1), a2) or a3) and/or before step b), a heat treatment step of the substrate to relax any internal stress in said substrate.

66: The method according to claim 49, wherein the substrate is metallic, and preferably based on gold or silver.

67: The method according to claim 50, wherein the coat of substantially pure silver has a thickness between 1500 nm and 2500 nm.

68: The method according to claim 49, wherein the silver and copper alloy comprises between 0.2% and 8% by weight, preferably between 0.5% and 7% by weight, of copper with respect to the total weight of the alloy.

69: The method according to claim 49, wherein the substrate is a horological element.

70: The method according to claim 69, wherein a structuring is produced on the surface of the substrate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Further specificities and advantages will emerge clearly from the description given hereinafter, which is by way of indication and in no way limiting, with reference to the appended drawings, wherein:

[0021] FIG. 1 is a schematic view of a first alternative embodiment of substrate according to the present invention;

[0022] FIG. 2 is a schematic view of a second alternative embodiment of substrate according to the present invention; and

[0023] FIG. 3 is a schematic view of a third alternative embodiment of substrate according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0024] The present invention relates to a substrate comprising a final silver-plated surface protected against silver tarnishing by a protective coat.

[0025] Such a substrate is for example a horological or jewellery element, and particularly an external horological part element. In particular, the substrate can be a timepiece dial, which can have a structuring on the surface thereof, such as engine-turning, i.e. a set of lines with fine details, which intersect with a view to obtaining a decorative effect. The substrate can be an index, a decoration mounted on the dial (moon phase or other, or a hand.

[0026] The substrate is preferably metallic. It can be made of brass, based on yellow or white gold, or silver, or any other suitable metal or metal alloy, precious or not.

[0027] The substrate can have an initial silver-plated surface or not.

[0028] The substrate can comprise an initial silver-plated surface, said substrate then being based on silver (pure silver or silver alloy, particularly silver alloys with an Ag content >90% by weight) and having intrinsically said initial silver-plated surface also forming the final silver-plated surface. The protective coat is then deposited directly on the silver-based substrate.

[0029] With reference to FIG. 1, a substrate 1 according to a first alternative embodiment of the invention is represented whereby the substrate 1 can have no initial silver-plated surface or comprise an intrinsic silver-plated surface. In the first case, the substrate can be for example made of brass, based on yellow or white gold, or any other suitable metal or metal alloy, precious or not, with the exception of silver. In the second case, the substrate 1 is based on silver, made of solid silver for example, and has intrinsically an initial silver-plated surface.

[0030] Advantageously, the substrate 1 comprises a coat 2 of a silver and copper alloy comprising between 0.1% and 10% by weight of copper with respect to the total weight of the alloy, forming said final silver-plated surface. The coat 2 of silver and copper alloy can be deposited directly on the substrate 1, in particular when said substrate 1 is not based on silver, and take the place of the fine silver coating conventionally used. The coat 2 of silver and copper alloy can be deposited by any suitable method, such as PVD (flash deposition), or galvanically by means of a suitable silver and copper galvanic bath.

[0031] With reference to FIG. 2, a substrate 10 according to a second alternative embodiment of the invention is represented whereby the substrate 10 is not based on silver and comprises a coat 20 of substantially pure silver forming said final silver-plated surface. Such a coat 20 is preferably deposited galvanically. The substrate 10 can be itself made of brass and coated with a coat of precious metal, deposited for example galvanically, for example a coat of gold. The substrate 10 can also be a solid precious metal, for example made of solid gold. If necessary, intermediate metallic coats known to a person skilled in the art can be used to prevent any intermetallic diffusion between certain metals initiated by heat treatments or the ALD process.

[0032] With reference to FIG. 3, a substrate 100 according to a third alternative embodiment of the invention is represented whereby the substrate 100 is not based on silver and comprises a coat 2 of a silver and copper alloy comprising between 0.1% and 10% by weight of copper with respect to the total weight of the alloy forming said final silver-plated surface. Furthermore, the substrate 100 comprises, between said substrate 100 and said coat 2 of silver and copper alloy, a coat 20 of substantially pure silver.

[0033] Regardless of the alternative embodiment with a coat of substantially pure silver, said coat 20 of substantially pure silver can have a thickness between 200 nm and 3000 nm.

[0034] According to an embodiment, the coat 20 of substantially pure silver can have a thickness between 200 nm and 600 nm, preferably between 300 nm and 500 nm in order to form a thin silver coating.

[0035] According to a preferred embodiment, the coat 20 of substantially pure silver can have a thickness between 1000 nm and 3000 nm, preferably between 1500 nm and 2500 nm in order to form a thick silver coating.

[0036] Such a thick silver coating has the advantage of obtaining an intermediate or final coat of substantially pure silver free from porosities, in order to be able to obtain a final silver-plated surface of the substrate free from porosity and thus ensure increased adhesion of the protective coat against silver tarnishing on said final silver-plated surface.

[0037] Regardless of the alternative embodiment with a coat of silver and copper alloy, the coat 2 of silver and copper alloy has either a thickness between 200 nm and 600 nm, and advantageously between 300 nm and 400 nm, or, preferably, a thickness between 1000 nm and 3000 nm, and more preferably between 1500 nm and 2500 nm in order to constitute a thick coating having the aforementioned advantages.

[0038] Preferably, the silver and copper alloy comprises between 0.2% and 8% by weight, preferably between 0.5% and 7% by weight, of copper with respect to the total weight of the alloy. The proportion of copper with respect to the silver is selected so as to create enough Cu radicals on the surface which will subsequently ensure the adherence of the protective coat against silver tarnishing, without altering the colour of the silver since the coat of silver and copper alloy forms the final silver-plated surface of the substrate.

[0039] The final silver-plated surface of the substrate, either the coat of silver and copper alloy 2 of the substrate 1 or 100, or the coat of substantially pure silver 20 of the substrate 10, or the initial silver-plated surface of the surface if it is itself based on silver, is protected against silver tarnishing by a protective coat 4 having a thickness between 1 nm and 200 nm, preferably between 1 nm and 100 nm, and more preferably between 40 nm and 100 nm.

[0040] According to the invention, said protective coat 4 comprises a first coat 4a of Al.sub.2O.sub.3 deposited on said final silver-plated surface and having a thickness between 0.5 nm and 100 nm, preferably between 0.5 nm and 50 nm, and on the first coat 4a of Al.sub.2O.sub.3, a second coat 4b of TiO.sub.2 having a thickness between 0.5 nm and 100 nm, preferably between 0.5 nm and 50 nm.

[0041] Particularly preferably, the first coat 4a of Al.sub.2O.sub.3 has a thickness between 30 nm and 50 nm and the second coat 4b of TiO.sub.2 has a thickness between 10 nm and 50 nm.

[0042] Advantageously, the protective coat 4 has been deposited by means of a method selected from the group comprising an ALD (Atomic Layer Deposition), PVD (Physical Vapour Deposition), CVD (Chemical Vapour Deposition), and sol-gel deposition. Preferably, the protective coat 4 has been deposited by ALD. A successive ALD deposition of the first coat 4a of Al.sub.2O.sub.3 then of the second coat 4b of TiO.sub.2 makes it possible to form compact coats and obtain extremely thin and highly protective coatings, with a particularly good aesthetic rendering. The details and parameters of such an ALD deposition are known to a person skilled in the art. They are for example described in the patent EP 1 994 202. The Al.sub.2O.sub.3 coat can be obtained from a TMA (Tri-Methyl-Aluminium) precursor, the oxidation of which can be carried out with H.sub.2O, O.sub.2; or O.sub.3. The TiO.sub.2 coat can be obtained from TTIP (Titanium Iso ProPoxide) or TiCl.sub.4 (Titanium Tri Chloride), the oxidation of which can be carried out with H2O, O.sub.2 or O.sub.3.

[0043] Particularly preferably, the protective coat 4 against silver tarnishing is obtained by means of an ALD deposition of a first coat of Al.sub.2O.sub.3 having a thickness between 30 nm and 50 nm and of a second coat 4b of TiO.sub.2 having a thickness between 10 nm and 50 nm.

[0044] Surprisingly, the combination of the order and the thickness of the first coat of Al.sub.2O.sub.3 and of the second coat of TiO.sub.2 makes it possible to obtain a protective coat against silver tarnishing which enhances the very white colour of the silver as much as possible, thus preserving the silvery brightness of the final surface of the substrate.

[0045] The substrate according to the invention is obtained by means of a manufacturing method which comprises the following steps: [0046] a) obtaining a substrate 1, 10, 100 having a final silver-plated surface [0047] b) depositing on at least a part of said final silver-plated surface from step a) at least one protective coat 4 against silver tarnishing having a thickness between 1 nm and 200 nm, preferably between 1 nm and 100 nm, and more preferably between 40 nm and 100 nm, said step b) comprising a first step b1) of depositing, on at least a part of said final silver-plated surface from step a), a first coat 4a of Al.sub.2O.sub.3 having a thickness between 0.5 nm and 100 nm, preferably between 0.5 nm and 50 nm, and a second step b2) of depositing, on the first coat 4a of Al.sub.2O.sub.3 obtained in step b1), a second coat 4b of TiO.sub.2 having a thickness between 0.5 nm and 100 nm, preferably between 0.5 nm and 50 nm.

[0048] Particularly preferably, the first coat 4a of Al.sub.2O.sub.3 has a thickness between 30 nm and 50 nm and the second coat 4b of TiO.sub.2 has a thickness between 10 nm and 50 nm.

[0049] Advantageously, step b) is carried out by means of a method selected from the group comprising an ALD, PVD, CVD, and sol-gel deposition.

[0050] Particularly preferably, step b) is carried out by means of ALD deposition.

[0051] Advantageously, the method according to the invention can combine protective coat deposition and plasma treatment, before and/or after step b2), typically an Ar plasma, in order to reduce the internal tensions of the protective coats deposited. This combination makes it possible to soften the protective coats to render them less brittle during environmental stress, such as mechanical, thermal or other stress.

[0052] Advantageously, the method for manufacturing the substrate according to the invention can comprise, between step a) and step b), at least one plasma pre-treatment step c) of the final silver-plated surface of the substrate obtained in step a).

[0053] This plasma pre-treatment step c) consists of stripping the final silver-plated surface in order to remove particularly the AgS/Ag.sub.2S sulphides which have formed naturally on the surface of the substrate exposed to the air and which prevent good adhesion of the protective coat 4.

[0054] Advantageously, this step c) consists of an Ar plasma or Ar/H.sub.2 plasma pre-treatment.

[0055] According to an implementation of the method for manufacturing the substrate according to the invention, step b) is implemented directly after step c), without any other additional pre-treatment.

[0056] According to a further implementation, the method for manufacturing the substrate according to the invention comprises an additional intermediate oxidising pre-treatment step d), between step c) and step b), making it possible to create AgO/Ag.sub.2O sites forming covalent bonds between the Al.sub.2O.sub.3 present in the first coat 4a and the silver of the final silver-plated surface of the substrate so as to favour the adhesion of the protective coat 4 on the substrate.

[0057] According to an alternative embodiment, the oxidising pre-treatment of step d) can consist of an oxidising plasma pre-treatment with an oxidising agent such as oxygen, or Ar/O.sub.2, making it possible to create the AgO/Ag.sub.2O sites.

[0058] The O.sub.2 dosage in the plasma must be precise in order to create enough AgO/Ag.sub.2O sites, but which tend to turn silver yellow, while ensuring the whiteness of the silver.

[0059] The plasma treatment parameters are known to a person skilled in the art and do not require further details here.

[0060] According to a further alternative embodiment, the oxidising pre-treatment of step d) can consist of injecting water or hydrogen peroxide, in liquid form, into a pre-treatment chamber in a vacuum causing the evaporation of the water or hydrogen peroxide, which in contact with the substrate, will form AgO/Ag.sub.2O sites. The quantity of water or hydrogen peroxide injected is of the order of some tens of micromoles.

[0061] Particularly advantageously, step d) is carried out without venting between step c) and said step d). To this end, the substrate pre-treated according to step c) undergoes the additional pre-treatment according to step d) without breaking the vacuum.

[0062] Furthermore, the substrate obtained from step a) and pre-treated according to step c) only or according to steps c) and d) is then advantageously transferred in a vacuum into a deposition chamber, preferably by ALD deposition, for a direct implementation of step b) on the pre-treated substrate obtained from step c) or steps c) and d), without venting the final silver-plated surface of the substrate.

[0063] To this end, pre-treatment steps c) and d) and step b) of depositing the protective coat, preferably by ALD deposition, are advantageously implemented in the same overall treatment machine wherein the device for pre-treatment according to step c) or according to steps c) and d) is incorporated in the device for depositing the protective coat 4, preferably by ALD deposition, enabling an overall treatment without venting the final silver-plated surface of the substrate, and preferably in a vacuum, for the implementation of steps c), optionally d) if present, and b).

[0064] The substrate 1, 10, 100 of step a) is metallic, and preferably based on gold or silver.

[0065] Said substrate of step a) can comprise an initial silver-plated surface, said substrate then being based on silver and having intrinsically said initial silver-plated surface also forming the final silver-plated surface. The protective coat 4 is then deposited directly on the silver-based substrate according to step b).

[0066] According to a further alternative embodiment, if the substrate is made of solid silver, the colour thereof will not be as white as that of fine silver, it could then be intended to deposit, by means of galvanoplasty or a vacuum process, a coat of fine silver on solid silver, before depositing the protective coat.

[0067] According to a further preferred alternative embodiment, whether the substrate 1, 100 from step a) has an initial silver-plated surface or not, the method for producing the substrate according to the invention can comprise a step a1) of depositing on said substrate 1, 100 a coat 2 of a silver and copper alloy comprising between 0.1% and 10% by weight of copper with respect to the total weight of the alloy to obtain said final silver-plated surface, as shown in FIG. 1.

[0068] According to a further preferred alternative embodiment, if the substrate 100 from step a) has no initial silver-plated surface, the method for producing the substrate according to the invention can comprise an intermediate step a2) of depositing a coat 20 of substantially pure silver between said substrate 100 and the coat 2 of silver and copper alloy, as shown in FIG. 3.

[0069] According to a further preferred alternative embodiment, if the substrate 10 from step a) has no initial silver-plated surface, the method for producing the substrate according to the invention can comprise a step a3) of depositing a coat 20 of substantially pure silver on said substrate 10 to obtain said final silver-plated surface, as shown in FIG. 2. The same applies if the substrate from step a) has an initial silver-plated surface.

[0070] Advantageously, the substrate 1, 10, 100 can be heat-treated before at least one of steps a1), a2) or a3) and/or before step b) in order to relax any internal stress associated with the preceding machining or coat deposition steps. The treatment temperatures and durations are dependent on the nature of the substrate and the coats and must not impact the aesthetics of the part before the deposition of the protective coat from step b). The heat treatment parameters are known to a person skilled in the art and do not require further details here.

[0071] Regardless of the alternative embodiment with the coat of substantially pure silver, said coat 20 of substantially pure silver has a thickness between 200 nm and 3000 nm.

[0072] According to an embodiment, the coat 20 of substantially pure silver can have a thickness between 200 nm and 600 nm, preferably between 300 nm and 500 nm, in order to form a thin silver coating.

[0073] According to a further preferred embodiment, the coat 20 of substantially pure silver can have a thickness between 1000 nm and 3000 nm, preferably between 1500 nm and 2500 nm in order to form a thick silver coating, as explained above.

[0074] Regardless of the alternative embodiment with a coat of silver and copper alloy, said coat 2 of silver and copper alloy has either a thickness between 200 nm and 600 nm, advantageously between 300 nm and 400 nm, or, preferably, a thickness between 1000 nm and 3000 nm, and more preferably between 1500 nm and 2500 nm in order to form a thick coating as explained above.

[0075] Preferably, the silver and copper alloy comprises between 0.2% and 8% by weight, preferably between 0.5% and 7% by weight, of copper with respect to the total weight of the alloy.

[0076] When the substrate has a structuring on the surface thereof, such as engine-turning, step a) of the method for manufacturing for the substrate according to the invention comprises a substep whereby said structuring is produced on the surface of the substrate.

[0077] A substrate comprising a final silver-plated surface protected with a protective coat according to the invention, in particular when the protective coat against silver tarnishing has been deposited by ALD, has an appearance and very white brightness of the silver that are preserved despite the presence of the protective coat against silver tarnishing. If the substrate has undergone engine-turning, the fine details of the engine-turning remain clearly visible despite the presence of said protective coat against silver tarnishing.

[0078] Furthermore, the substrate according to the invention has a protective coat against silver tarnishing without any lack of adherence.

[0079] The substrates according to the invention can also be used to produce jewellery, writing implement, spectacle-related and leather good products.