External part for a timepiece or a piece of jewellery comprising an interferential colour coating and manufacturing method of said part

Abstract

The invention relates to an exterior part (10) comprising a substrate (11) comprising a coating (12) consisting of the following successive superimposed layers: - an opaque or semi-opaque reflective layer (121) configured to have a reflectance of at least 90% for wavelengths of 600 nm to 780 nm, - a transparent or semi-transparent layer (122) having a refractive index of 1.45 to 2.8 for a wavelength of 630 nm, - an absorbing layer (123), said layer imparting a predetermined interference color to the coating (12).

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of watchmaking or jewelry, more particularly to an external component of a watch or jewelry piece comprising a coating providing an interference color, and to a method of manufacturing said component.

[0002] In the present text, the term "external component" refers to any decorative article in the field of watchmaking or jewelry, for example consisting of a watch case, a watch dial, a watch dial lettering block, a watch bracelet, etc., intended to be visible to the user.

[0003] Preferably, the present invention relates to an external component of a watch or jewelry piece comprising a coating, the interference color of which is a red hue. BACKGROUND

[0004] In the field of watchmaking or jewelry, more generally in the field of decorative articles, the deposition methods by painting, varnishing or enameling are not always suitable.

[0005] Indeed, on the one hand, the layer of material applied to the surface of the article to be decorated is too thick to reveal any surface structure, for example brushed, sunray, sandblasted, laser-structured surface, etc., on the other hand, the lifetime of this layer and thus of its color is not always satisfactory.

[0006] Thus, thin-film vacuum deposition techniques, such as physical vapor deposition (known by the acronym "PVD"), chemical vapor deposition (known by the acronym "CVD"), atomic layer deposition (known by the acronym "ALD") are preferred.

[0007] However, although these deposition techniques make it possible to obtain a wide variety of colored coatings, the implementation of these methods does not make it possible to obtain certain specific colors, such as a red hue, on an industrial scale. SUMMARY

[0008] The present invention overcomes the aforementioned drawbacks by providing a solution for producing an external component having a predetermined interference color resulting from the addition of destructive and constructive interferences. In the present text, the color resulting from the optical interference phenomenon is called "interference color".

[0009] To this end, the present invention relates to an external component comprising a substrate comprising a coating consisting of the following successive superimposed layers:

[0010] - an opaque or semi-opaque reflective layer configured to have a reflectance of at least 90% for wavelengths of 600 nm to 780 nm,

[0011] - a transparent or semi-transparent layer having a refractive index of 1.45 to 2.8 for a wavelength of 630 nm,

[0012] - an absorbing layer.

[0013] Said layers confer a predetermined interference color to the coating.

[0014] Advantageously, the predetermined color is a red hue with metallic luster. More particularly, the predetermined color is a Burgundy or a purple-red hue. This predetermined color is obtained by a particular arrangement of the optical stack defined by the layers of said coating.

[0015] Furthermore, said coating has a very low thickness, generally less than 3 μιη, which makes it suitable for covering any decorative article comprising surface structures or comprising complex geometrical shapes.

[0016] Another advantage of the present application is that it makes it possible to obtain very diversified red hues without substantially modifying the thickness of the coating. For example, between all the red hues that said coating can have, the coating thickness varies by a value of less than 3 nm.

[0017] In particular embodiments, the present application can further include one or more of the following features, alone or in any technically possible combination.

[0018] In particular embodiments, the reflective layer is made of a metallic material chosen from copper (Cu), gold (Au), rhodium (Rh), platinum (Pt).

[0019] In particular embodiments, the reflective layer is made of Cu.

[0020] In particular embodiments, the reflective layer has a thickness of at least 40 nm.

[0021] In particular embodiments, the reflective layer has a thickness of 100 nm.

[0022] In particular embodiments, the transparent layer is made of a material chosen from silicon dioxide (SiO2), titanium dioxide (TiO2), aluminum oxide (Al2O3), hafnium dioxide (HfO2), zirconium dioxide (ZrO2), tantalum oxide (Ta2O5), tin dioxide (SnO2), indium tin oxide (ITO), zinc oxide (ZnO), magnesium oxide (MgO), silicon nitride (Si3N4) and aluminum nitride (AIN).

[0023] In particular embodiments, the transparent layer is made of SiO2.

[0024] In particular embodiments, the transparent layer has a thickness of 10 nm to 50 nm.

[0025] In particular embodiments, the transparent layer has a thickness of 30 nm.

[0026] In a particular embodiment, the absorption layer is made of a material chosen from titanium (Ti), nickel (Ni) or chromium (Cr).

[0027] In a particular embodiment, the absorption layer is made of Cr.

[0028] In a particular embodiment, the absorption layer has a thickness of 5 nm to 8 nm.

[0029] In a particular embodiment, the coating has a reflectance less than 10% for wavelengths of 350 nm to 600 nm and greater than or equal to 10% for wavelengths of 620 nm to 780 nm.

[0030] In a particular embodiment, the coating has a red color, characterized in that in the CIELAB color space with D65 as illuminant, the parameters L* of 25 to 35, a* of 8 to 15 and b* of 0 to 7.

[0031] In a particular embodiment, the coating comprises an acrylic and / or nitrocellulose protective layer superimposed on the absorption layer and having a refractive index of 1.48 to 1.51 for a wavelength of 630 nm.

[0032] According to another object, the application relates to a method of manufacturing an external component of a timepiece or a piece of jewelry, characterized in that it comprises the following successive steps of generating a coating on the surface of a substrate:

[0033] - depositing on the substrate an opaque reflective layer configured to have a reflectance of at least 90% for wavelengths of 600 nm to 780 nm,

[0034] - depositing a transparent layer having a refractive index of 1.45 to 2.8 at 630 nm,

[0035] - depositing an absorption layer.

[0036] In a particular embodiment, the deposition of the reflective layer, the transparent layer and the absorption layer is carried out by physical vapor deposition by evaporation with an electron gun.

[0037] In a particular embodiment, the step of depositing the transparent layer is carried out at a deposition rate of 0.01 nm / s to 0.1 nm / s.

[0038] In a particular embodiment, the step of depositing the absorption layer is carried out at a deposition rate of 0.01 nm / s to 0.05 nm / s.

[0039] In a particular embodiment, the method comprises a final step of depositing a protective layer configured to advantageously have a refractive index of 1.48 to 1.51 for a wavelength of 630 nm.BRIEF DESCRIPTION OF DRAWINGS BRIEF DESCRIPTION OF DRAWINGS

[0040] Other characteristics and advantages of the application will appear on reading the following detailed description, given as non-limiting examples, with reference to the attached drawings in which:

[0041] - Figure 1 shows a cross-sectional view of an external part according to a preferred exemplary embodiment of the application;

[0042] - Figure 2 shows the spectral reflectance curve measured with a spectrophotometer on a coating according to the application;

[0043] - Figure 3 shows the spectral reflectance curve measured with a spectrophotometer on a coating according to the application further comprising a protective layer;

[0044] - Figure 4 shows a flowchart of a method for manufacturing an external part according to another aspect of the application. DETAILED DESCRIPTION

[0045] The application relates to an external part 10 comprising a substrate 11 comprising a coating 12 consisting of several successive superimposed layers to confer on the external part a predetermined interference color on the surface intended to be visible to the user.

[0046] Preferably, the predetermined interference color is a red hue.

[0047] The substrate 11 can be made of a metallic, ceramic or polymeric material. In addition, it can be coated with an electroplated primer.

[0048] A reflective, opaque or semi-opaque layer 121 is deposited on the substrate 11, configured to reflect wavelengths of 600 nm to 780 nm.

[0049] More particularly, the reflective layer 121 preferably has a reflection coefficient greater than 0.9 for wavelengths of 600 nm to 780 nm.

[0050] The reflective layer 121 can be semi-opaque in the sense that it can have a non-zero transmittance, but the transmittance must remain less than or equal to 15% in the wavelength range of the visible spectrum.

[0051] This reflective layer 121 is preferably made of a metallic material and has a thickness of at least 40 nm.

[0052] Preferably, the reflective layer 121 is made of a material chosen from Cu, Au, Rh or Pt. The material of the reflective layer 121 is chosen for its optical ability to reflect the light of wavelengths from 600 nm to 780 nm, this interval representing the red hue in the spectrum. Moreover, this material is chosen for its low absorption of red wavelengths.

[0053] More preferably, the reflective layer 121 is made of Cu, in particular for economic reasons and for ease of implementation.

[0054] The reflective layer 121 can be made by PVD method, by electroplating or by any other suitable thin film deposition method.

[0055] A transparent layer 122 is superimposed on the reflective layer 121.

[0056] The transparent layer 122 can also be translucent in the sense that it can absorb light in a certain range of wavelengths, for example wavelengths less than 500 nm in the case where the transparent layer 122 is made of Ti02, and be transparent to light in another range of wavelengths.

[0057] The material of this transparent layer 122 is chosen for its optical property of transparency. For example, the transparent layer 122 is made of a material chosen from Si02, Ti02, AI2O3, Hf02, Zr02, Ta205, Sn02, ITO, ZnO, MgO, Si3N4, A1N. Preferably, the transparent layer 122 is made of Si02, in particular for economic reasons, ease of implementation and repeatability.

[0058] For example, the transparent layer 122 advantageously has a refractive index of 1.45 to 2.8 for a wavelength of 630 nm and has a thickness of 10 nm to 50 nm, depending on the refractive index of the layer.

[0059] The transparent layer 122 can be deposited on the reflective layer 121 by PVD, CVD, ALD method or by any other suitable thin film deposition method.

[0060] Finally, as shown in Figure 1 an absorbing layer is superimposed on the transparent layer 122.

[0061] This absorbing layer 123 is made of a metallic material chosen for its optical absorption properties. For example, the absorbing layer 123 is made of Ti, Ni or Cr. Preferably, the absorbing layer 123 is made of chromium.

[0062] The absorbing layer 123 has a thickness of 4 nm to 10 nm, preferably 5 nm to 8 nm, more preferably 7.2 nm to 7.8 nm.

[0063] It is understood here that the present application advantageously makes it possible to obtain an interference color of red hue, thanks to the coating 12, which has a very low thickness, of the order of a few microns, more precisely less than 3 pm.

[0064] Thanks to the above-mentioned features, the coating 12 is advantageously configured to have a reflectance of less than 10%, varying from 8% to 3%, for wavelengths of 350 nm to 580 nm and a reflectance varying from 3% to 24% for wavelengths of 580 nm to 750 nm. These values are graphically represented by the spectral reflectance curves of Figure 2 from measurements made on the coating 12 with a spectrophotometer.

[0065] These reflectances can advantageously delimit the reflected spectrum of color representative of the red hue perceived visually by the user.

[0066] In a preferred exemplary embodiment of the application, the coating 12 can further advantageously comprise an acrylic and / or nitrocellulose protective layer 124 superimposed on the absorbing layer 123, to protect the other layers from possible chemical and / or mechanical attacks.

[0067] The addition of such a protective layer 124, for example having a thickness of 3 pm and a refractive index close to 1.5, for example 1.48 to 1.51, for a wavelength of 630 nm, also makes it possible to create a destructive interference to advantageously reduce the reflectance for wavelengths of 350 nm to 550 nm, to enable the wavelengths of 580 nm to 780 nm to delimit the color of the coating 12.

[0068] In other words, in a preferred exemplary embodiment of the application, the protective layer 124 advantageously participates in obtaining the final red color of the coating 12.

[0069] With the aid of the protective layer 124, the coating 12 has a reflectance of less than or equal to 5% for wavelengths of 350 nm to 550 nm, varying from 5% to 21% for wavelengths of 550 nm to 750 nm. These values are graphically represented by the spectral reflectance curves of Figure 3 from measurements made on the coating 12 with a spectrophotometer.

[0070] Thus, in a preferred exemplary embodiment of the application, the coating 12 has a red color characterized, in the CIELAB color space with D65 as the light source, by a parameter L* of 25 to 35, a parameter a* of 8 to 15 and a parameter b* of 0 to 7.

[0071] It should be noted that the protective layer 124 is not essential and that, in other embodiments of the application, the coating 12 can have a red color, for example characterized in the CIELAB color space by the above-mentioned parameters, without said protective layer 124. Thus, in a preferred exemplary embodiment of the application, the coating 12 has a red color characterized, in the CIELAB color space with D65 as the light source, by a parameter L* of 25 to 35, a parameter a* of 8 to 15 and a parameter b* of 0 to 7.

[0072] The application further relates to a method of manufacturing an external component 10 of a timepiece or a piece of jewelry, for example as described above. The successive steps of this method are represented by the flowchart of Figure 4 consist in producing a coating 12 on the surface of the base 11 to produce a predetermined interference color.

[0073] More particularly, the method comprises the following successive steps:

[0074] - 101 depositing on the base 11 an opaque reflective layer 121, said layer being adapted to reflect wavelengths of 600 nm to 780 nm,

[0075] - 102 depositing a transparent layer 122 having a refractive index of 1.45 to 2.8 for a wavelength of 630 nm,

[0076] - 103 depositing an absorbing layer 123.

[0077] One example of the manufacturing method described in detail below uses vacuum deposition techniques to deposit the reflective layer 121, the transparent layer 122 and the absorbing layer 123.

[0078] More particularly, in one preferred embodiment, a physical vapor deposition method by evaporation with an electron gun is used.

[0079] However, it should be noted that the deposition of the layers can be carried out by other PVD methods, such as magnetron sputtering in a reactive medium, or by CVD methods, such as the ALD method and plasma-enhanced chemical vapor deposition, known by the acronym PECVD.

[0080] The deposition 101 of the reflective layer 121 is carried out, for example, so as to give said reflective layer 121 a thickness of 100 nm. Preferably, among the following materials that can be considered for constituting the reflective layer 121 : Cu, Au, Rh or Pt, Cu is preferred.

[0081] The transparent layer 122 is then deposited on the reflective layer 121, preferably with a thickness of 30 nm. Preferably, among the following materials that can be considered for constituting the transparent layer 122: Si02, Ti02, AI2O3, Hf02, Zr02, Ta205, Sn02, ITO, ZnO, MgO, Si3N4 or A1N, Si02 is preferred.

[0082] For example, in order to obtain good repeatability of the deposition of the transparent layer 122, a deposition rate of 0.01 nm / s to 0.1 nm / s, preferably 0.1 nm / s, is chosen, with an oxygen (02) flow of 5 seem. These parameters also make it possible to control very precisely the material density and the thickness of the transparent layer 122.

[0083] An absorbing layer 123 is then deposited on the transparent layer 122, preferably with a thickness of, for example, 5 nm to 8 nm, preferably 7.2 nm to 7.8 nm. Preferably, the absorbing layer 123 is made of chromium.

[0084] For example, in order to obtain a good repeatability of the deposition of the absorbing layer 123, a deposition rate of 0.01 nm / s to 0.05 nm / s, preferably 0.02 nm / s, is chosen, and an argon (Ar) flow of 2 seem is used in order to minimize the effect of the fouling of the walls of the enclosure on the repeatability of the deposition of the absorbing layer 123.

[0085] In a preferred embodiment of the application, the manufacturing method further comprises a final step 104 of depositing a protective layer 124. This protective layer 124 is configured to advantageously have a refractive index of about 1.48 to 1.51 for a wavelength of 630 nm.

Claims

1. An exterior component (10) comprising a substrate (11), characterized in that It comprises a coating (12) consisting of the following successive superimposed layers: - an opaque or semi-opaque reflective layer (121) configured to have a reflectance of at least 90% for wavelengths of 600 nm to 780 nm, - a transparent or semi-transparent layer (122) having a refractive index of 1.45 to 2.8 for a wavelength of 630 nm, - an absorbing layer (123) made of a material chosen from Ti, Ni or Cr, said coating (12) having a red predetermined interference color, in the CIELAB color space with D65 as light source, a parameter L* of 25 to 35, a parameter a* of 8 to 15 and a parameter b* of 0 to 7, wherein said reflective layer (121) has a thickness of at least 40 nm, said transparent or semi-transparent layer (122) has a thickness of 10 nm to 50 nm and said absorbing layer (123) has a thickness of 5 nm to 8 nm.

2. External part (10) according to claim 1, wherein said reflective layer (121) is made of a metallic material chosen from Cu, Au, Rh, Pt.

3. External part (10) according to claim 1 or 2, wherein said reflective layer (121) is made of Cu.

4. External part (10) according to claim 1, wherein said reflective layer (121) has a thickness of 100 nm.

5. External part (10) according to claim 1 or 2, wherein said transparent or semi-transparent layer (122) is made of a material chosen from Si02, Ti02, AI2O3, Hf02, Zr02, Ta205, Sn02, ITO, ZnO, MgO, Si3N4, AIN.

6. External part (10) according to claim 5, wherein said transparent or semi-transparent layer (122) is made of Si02.

7. External part (10) according to claim 1, wherein said transparent or semi-transparent layer (122) has a thickness of 30 nm.

8. External part (10) according to claim 1, wherein said absorbing layer (123) is made of Cr.

9. External part (10) according to claim 1 or 2, wherein said coating (12) has a reflectance of less than 10% for wavelengths of 350 nm to 600 nm and greater than or equal to 10% for wavelengths of 620 nm to 780 nm.

10. External part (10) according to claim 1 or 2, wherein said coating (12) comprises a protective layer (124) of acrylic and / or nitrocellulose superimposed on the absorbing layer (123) and having a refractive index of 1.48 to 1.51 for a wavelength of 630 nm.

11. A method of manufacturing an exterior component (10) of a timepiece or a piece of jewelry, characterized in that It comprises the following successive steps for generating a coating (12) on the surface of a substrate (11): - 101 depositing on the substrate (11) an opaque reflective layer (121) configured to have a reflectance of more than 90% for wavelengths of 600 nm to 780 nm, - 102 depositing a transparent or semi-transparent layer (122) having a refractive index of 1.45 to 2.8 for a wavelength of 630 nm, - 103 depositing an absorbing layer (123) made of a material chosen from Ti, Ni or Cr, - 103 depositing an absorbing layer (123), said absorbing layer (123) being made of a material chosen from Ti, Ni or Cr, wherein said reflecting layer (121) has a thickness of at least 40 nm, said transparent or semi-transparent layer (122) has a thickness of 10 nm to 50 nm, and said absorbing layer (123) has a thickness of 5 nm to 8 nm.

12. The method according to claim 11, wherein the deposition of the reflecting layer (121), of the transparent or semi-transparent layer (122) and of the absorbing layer (123) is carried out by physical vapor deposition by means of an electron gun.

13. The method according to claim 11 or 12, wherein the step 102 of depositing the transparent or semi-transparent layer (122) is carried out at a deposition rate of 0.01 nm / s to 0.1 nm / s.

14. The method according to claim 11 or 12, wherein the step 103 of depositing the absorbing layer (123) is carried out at a deposition rate of 0.01 nm / s to 0.05 nm / s.

15. The method according to claim 11 or 12, comprising a final step 104 of depositing a protective layer (124) configured to have a refractive index of 1.48 to 1.51 for a wavelength equal to 630 nm.

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