COVERING PART OF A CLOCK OR PIECE OF JEWELRY WITH AN INTERFERENCE COATING AND METHOD FOR MANUFACTURING THIS PART

Description

Technical field of the invention

[0001] The invention falls within the field of watchmaking or jewelry, and relates more particularly to a watchmaking or jewelry component comprising a coating giving an interference color, and a method for manufacturing said component.

[0002] In this text, "dressing parts" refers to any decorative item in the fields of watchmaking or jewelry, for example consisting of a case, a dial, a dial appliqué, a bracelet, etc., intended to be visible to a user.

[0003] Preferably, the present invention relates to a watch or jewelry component comprising a coating whose interference color is a shade of red. Technological background

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

[0005] Indeed, on the one hand, the layer of material applied to the surface of an item to be decorated is too thick to allow any surface structuring to appear, for example a brushed, sunburst, sandblasted, laser-structured surface, etc., and on the other hand, the lifespan of this layer and consequently of its color is not always satisfactory.

[0006] Thus, vacuum thin film deposition techniques, such as physical vapor deposition (PVD), chemical vapor deposition (CVD), and atomic layer deposition (ALD), are preferred.

[0007] These thin film deposition techniques are described in documents EP3339983, US20100209698 and US6849343.

[0008] However, despite the fact that these deposition techniques make it possible to obtain coatings of a multitude of colors, the implementation of these processes does not make it possible to obtain certain specific colors, such as shades of red, on an industrial basis. Summary of the invention

[0009] The invention overcomes the aforementioned drawbacks by providing a solution for producing a trim piece with a predetermined interference color resulting from the combination of destructive and constructive interference. In this text, "interference color" refers to a color generated by an optical interference phenomenon.

[0010] To this end, the present invention relates to a covering part comprising a substrate having a coating composed of the following successively superimposed layers: an opaque or semi-opaque reflective layer, configured to have a reflectance of at least 90% for wavelengths between 600 nm and 780 nm, with a thickness of at least 40 nm, a transparent or semi-transparent layer, with a refractive index between 1.45 and 2.8 for a wavelength of 630 nm, and with a thickness between 10 nm and 50 nm, - an absorbing layer with a thickness between 5 nm and 8 nm, an acrylic and / or nitrocellulose protective layer superimposed on the absorbing layer and with a refractive index between 1.48 and 1.51 for a wavelength of 630 nm.

[0011] These layers impart a predetermined interference color to the coating. In particular, these layers impart a red interference color to the coating, characterized in the CIELAB color space, illuminating D65, by an L* parameter between 25 and 35, an a* parameter between 8 and 15, and a b* parameter between 0 and 7.

[0012] Advantageously, the predetermined color is a shade of red with a metallic sheen. More specifically, the predetermined color is a shade of burgundy or purple. This predetermined color is achieved through the specific optical stacking arrangement defined by the coating layers.

[0013] In addition, the coating has a very low thickness, typically less than 3 µm, which makes it suitable for covering any decorative item with a surface structure or complex geometric shape.

[0014] Another advantage of the present invention lies in the fact that it allows for a very wide variety of shades of red without substantial modification of the coating thickness. For example, the coating thickness varies by a maximum of less than 3 nm between all the shades of red that the coating can exhibit.

[0015] In particular embodiments, the invention may further comprise one or more of the following features, taken individually or in all technically possible combinations.

[0016] In particular embodiments, the reflective layer is made of metallic material chosen from copper (Cu), gold (Au), rhodium (Rh), platinum (Pt).

[0017] In particular embodiments, the reflective layer is made of Cu.

[0018] In particular embodiments, the reflective layer has a thickness of 100 nm.

[0019] In particular embodiments, the transparent layer is made of a material selected from silicon dioxide (SiO2), titanium dioxide (TiO2), alumina (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 aluminium nitride (AIN).

[0020] In particular embodiments, the transparent layer is made of SiO2.

[0021] In particular embodiments, the transparent layer has a thickness of 30 nm.

[0022] In particular embodiments, the absorbent layer is made of a material chosen from: titanium (Ti), nickel (Ni) or chromium (Cr).

[0023] In particular embodiments, the absorbent layer is made of Cr.

[0024] In particular embodiments, the coating has a reflection rate of less than 10% for wavelengths between 350 nm and 600 nm, and greater than or equal to 10% for wavelengths between 620 nm and 780 nm.

[0025] According to another object, the present invention relates to a method for manufacturing a watch or jewelry component characterized in that it comprises the following successive steps of generating a coating on a substrate surface: deposition of an opaque reflective layer on a substrate, said layer being configured to have a reflectance of at least 90% for wavelengths between 600 nm and 780 nm, and having a thickness of at least 40 nm, deposition of a transparent layer having a refractive index between 1.45 and 2.8 at 630 nm, and having a thickness between 10 nm and 50 nm, deposition of an absorbing layer having a thickness between 5 nm and 8 nm,

[0026] The process further includes a final step 104 of depositing a protective layer configured to advantageously have a refractive index between 1.48 and 1.51 for a wavelength of 630 nm. Said layers are deposited so as to impart to the coating a red interference color characterized in the CIELAB color space, illuminating D65, by a parameter L* between 25 and 35, a parameter a* between 8 and 15, and a parameter b* between 0 and 7.

[0027] In specific implementation methods, the deposition of reflective, transparent and absorbent layers is carried out by physical vapor deposition process using electron gun evaporation.

[0028] In particular implementation modes, the transparent layer deposition step is carried out with a deposition speed between 0.01 nm / s and 0.1 nm / s.

[0029] In particular implementation modes, the absorbent layer deposition step is carried out with a deposition speed between 0.01 nm / s and 0.05 nm / s. Brief description of the figures

[0030] Other features and advantages of the invention will become apparent from the following detailed description, given by way of non-limiting example, with reference to the accompanying drawings in which: there figure 1 schematically represents a cross-sectional view of a trim piece according to a preferred embodiment of the invention; the figure 2 represents a spectral reflectance curve measured with a spectrocolorimeter on a coating according to the invention; the figure 3 represents a spectral reflectance curve measured with a spectrocolorimeter on a coating according to the invention, further comprising a protective layer; the figure 4represents a flowchart of a manufacturing process for a trim piece according to another aspect of the invention. Detailed description of the invention

[0031] The present invention relates to a covering piece 10 comprising a substrate 11 having a coating 12 composed of several successively superimposed layers allowing to give the covering piece, on a surface intended to be visible to a user, a predetermined interference color.

[0032] Preferably, the predetermined interference color is a shade of red.

[0033] The substrate 11 can be made of a metallic, ceramic or polymer material. Furthermore, it can be coated with a galvanic underlayer.

[0034] On substrate 11 is deposited a reflective layer 121, opaque or semi-opaque, configured to reflect wavelengths between 600 nm and 780 nm.

[0035] More specifically, reflective layer 121 preferentially exhibits a reflection coefficient greater than 0.9 for wavelengths between 600 nm and 780 nm.

[0036] The reflective layer 121 can be semi-opaque in the sense that it can have a transmittance other than zero; however, the transmittance must remain less than or equal to 15% over the range of wavelengths of the visible spectrum.

[0037] This reflective layer 121 is preferably made of metallic material and has a thickness of at least 40 nm.

[0038] 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 wavelengths between 600 nm and 780 nm, this range being representative of shades of red in the light spectrum. Furthermore, this material is chosen for its low absorption of wavelengths in the red range.

[0039] Even more preferably, the reflective layer 121 is made of Cu, particularly for economic reasons and ease of implementation.

[0040] The reflective layer 121 can be produced by PVD process, by galvanizing or by any other suitable thin film deposition process.

[0041] A transparent layer 122 is superimposed on the reflective layer 121.

[0042] The transparent layer 122 can also be semi-transparent in the sense that it can absorb light over a certain range of wavelengths, for example wavelengths below 500 nm in the case where said transparent layer 122 would be made of TiO2, and be transparent to light over another range of wavelengths.

[0043] The material for this transparent layer 122 is chosen for its optical transparency properties. For example, transparent layer 122 is made from a material selected from: SiO2, TiO2, Al2O3, HfO2, ZrO2, Ta2O5, SnO2, ITO, ZnO, MgO, Si3N4, and AIN. Preferably, transparent layer 122 is made from SiO2, particularly for economic reasons, ease of implementation, and repeatability.

[0044] For example, the transparent layer 122 advantageously has a refractive index between 1.45 and 2.8 for a wavelength of 630 nm and has a thickness between 10 nm and 50 nm, depending on the refractive index of the latter.

[0045] The transparent layer 122 can be deposited on the reflective layer 121 by PVD, CVD, ALD, or any other suitable thin film deposition process.

[0046] Finally, as the figure 1 , an absorbent layer is superimposed on the transparent layer 122.

[0047] 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.

[0048] The absorbent layer 123 has a thickness between 4 nm and 10 nm, preferably between 5 nm and 8 nm, and even more preferably between 7.2 nm and 7.8 nm.

[0049] It is understood here that the present invention makes it possible, thanks to the coating 12, to advantageously obtain an interference color in shades of red, said coating 12 having a very small thickness, on the order of a few thousandths of a millimeter, more precisely less than 3 µm.

[0050] Coating 12 is advantageously configured, thanks to the aforementioned characteristics, to exhibit a reflection rate of less than 10%, ranging from 8% to 3% for wavelengths between 350 nm and 580 nm, and ranging from 3% to 24% for wavelengths between 580 nm and 750 nm. These values ​​are graphically represented by the spectral reflectance curve of the figure 2, resulting from measurements carried out with a spectrocolorimeter on coating 12.

[0051] These reflection rates can advantageously define a reflection spectrum representative of a user's visual perception of a color within a shade of red.

[0052] The coating 12 also advantageously includes a protective layer 124, acrylic and / or nitrocellulose, superimposed on the absorbent layer 123, in order to protect the other layers from possible chemical and / or mechanical aggressions.

[0053] The addition of such a protective layer 124, for example with a thickness of 3 µm and a refractive index close to 1.5, for example between 1.48 and 1.51 for wavelengths of 630 nm, also makes it possible to generate destructive interferences which advantageously reduce the reflection rate between 350 nm and 550 nm leaving the wavelengths between 580 nm and 780 nm to define the color of the coating 12.

[0054] In other words, the protective layer 124 contributes advantageously to obtaining the final red color of the coating 12.

[0055] With the protective layer 124, the coating 12 exhibits a reflectance of less than or equal to 5% in the wavelength range between 350 nm and 550 nm, ranging from 5 to 21% for wavelengths between 550 nm and 750 nm. These values ​​are graphically represented by the spectral reflectance curve of the figure 3 , resulting from measurements carried out with a spectrocolorimeter on coating 12.

[0056] Thus, coating 12 has a red color characterized in the CIELAB color space, illuminating D65, by a parameter L* between 25 and 35, a parameter a* between 8 and 15, and a parameter b* between 0 and 7.

[0057] The present invention further relates to a method for manufacturing a watch or jewelry component 10, for example, as described above. The successive steps of this method are represented by the flowchart of the figure 4 and consist of generating a coating 12 on a surface of a substrate 11 in order to generate a predetermined interference color.

[0058] More specifically, the process includes the following successive steps: deposit 101 of an opaque reflective layer 121 on a substrate 11, said layer being adapted to reflect wavelengths between 600 nm and 780 nm, deposit 102 of a transparent layer 122 having a refractive index between 1.45 and 2.8 for a wavelength of 630 nm, deposit 103 of an absorbing layer 123.

[0059] An example of a manufacturing process described in detail below uses a vacuum deposition technique to deposit the reflective 121, transparent 122 and absorbent 123 layers.

[0060] More specifically, in a preferred implementation mode, a physical vapor phase deposition process using electron gun evaporation is employed.

[0061] However, it should be noted that layer deposition can be achieved by other PVD methods, such as magnetron sputtering in reactive media, or by CVD processes, such as the ALD process and plasma-enhanced chemical vapor deposition (known by the English acronym PECVD for "Plasma Enhanced Chemical Vapor Deposition").

[0062] The reflective layer 121 is deposited, for example, so that said reflective layer 121 has a thickness of 100 nm. Preferably, among the following materials that could be used to constitute the reflective layer 121: Cu, Au, Rh or Pt, Cu is preferred.

[0063] The transparent layer 122 is then deposited on the reflective layer 121, preferably so as to have a thickness of 30 nm. Preferably, among the following materials that can be considered for constituting the transparent layer 122: SiO2, TiO2, Al2O3, HfO2, ZrO2, Ta2O5, SnO2, ITO, ZnO, MgO, Si3N4, or AIN, SiO2 is preferred.

[0064] As an example, to achieve good repeatability for the deposition of the transparent layer 122, the deposition rate is chosen between 0.01 nm / s and 0.1 nm / s, preferably 0.1 nm / s, and the oxygen (O2) flux is 5 sccm. These parameters also allow for very precise control of the material density and thickness of the transparent layer 122.

[0065] The absorbent layer 123 is then deposited on the transparent layer 122, preferably so as to have a thickness of for example between 5 nm and 8 nm, preferably between 7.2 nm and 7.8 nm. Preferably, the absorbent layer 123 is made of chromium.

[0066] As an example, in order to obtain good repeatability for the deposition of the absorbing layer 123, the deposition speed is chosen between 0.01 nm / s and 0.05 nm / s, preferably 0.02 nm / s, and the argon (Ar) flux is 2 sccm so as to minimize the influence of fouling of the walls of the enclosure on the repeatability of the deposition of the absorbing layer 123.

[0067] The manufacturing process also includes a final step 104 of depositing a protective layer 124. This protective layer 124 is configured to advantageously have a refractive index of approximately between 1.48 and 1.51 for a wavelength of 630 nm.

Claims

1. An external part (10) for horology or for jewellery comprising a substrate (11) comprising a plating (12) consisting of the following successively overlapping layers: - an opaque or semi-opaque reflective layer (121), configured to have a reflectance of at least 90% for wavelengths comprised between 600 nm and 780 nm, with a thickness of at least 40 nm, - a transparent or semi-transparent layer (122), with a refractive index comprised between 1.45 and 2.8 for a wavelength of 630 nm, and with a thickness comprised between 10 nm and 50 nm, - an absorbent layer (123) with a thickness comprised between 5 nm and 8 nm, - a protective layer (124) of acrylic and / or nitrocellulose that overlaps the absorbent layer (123) and has a refractive index between 1.48 and 1.51 for a wavelength of 630 nm, said layers imparting to the plating (12) a red interference colour characterised, in the CIELAB colour space, illuminant D65, by an L* parameter comprised between 25 and 35, an a* parameter comprised between 8 and 15, and a b* parameter comprised between 0 and 7.

2. The external part (10) according to claim 1, in which the reflective layer (121) is made of a metallic material chosen among: Cu, Au, Rh, Pt.

3. The external part (10) according to claim 1 or 2, in which the reflective layer (121) is made of Cu.

4. The external part (10) according to any of claims 1 to 3, in which the reflective layer (121) has a thickness of 100 nm.

5. The external part (10) according to any of claims 1 to 4, in which the transparent layer (122) is made of a material chosen among: SiO2, TiO2, Al2O3, HfO2, ZrO2, Ta2O5, SnO2, ITO, ZnO, MgO, Si3N4, AlN.

6. The external part (10) according to claim 5, in which the transparent layer (122) is made of SiO2.

7. The external part (10) according to any of claims 1 to 6, in which the transparent layer (122) has a thickness of 30 nm.

8. The external part (10) according to any of claims 1 to 7, in which the absorbent layer (123) is made of a material chosen among: Ti, Ni or Cr.

9. The external part (10) according to claim 8, in which the absorbent layer (123) is made of Cr.

10. The external part (10) according to any of claims 1 to 9, in which the plating (12) has a reflectance of less than 10% for wavelengths comprised between 350 nm and 600 nm, and greater than or equal to 10% for wavelengths comprised between 620 nm and 780 nm.

11. A method for manufacturing an external part (10) for horology or for jewellery, said method comprising the following successive steps of hobbing a plating (12) on a surface of a substrate (11): - depositing 101 an opaque reflective layer (121) onto a substrate (11), said layer being configured to have a reflectance greater than 90% for wavelengths comprised between 600 nm and 780 nm and with a thickness of at least 40 nm, - depositing 102 a transparent layer (122), with a refractive index comprised between 1.45 and 2.8 for a wavelength of 630 nm, and with a thickness comprised between 10 nm and 50 nm, - depositing 103 an absorbent layer (123) with a thickness comprised between 5 nm and 8 nm, the method further comprising a final step 104 involving the deposition of a protective layer (124) configured to advantageously have a refractive index comprised between 1.48 and 1.51 for a wavelength equal to 630 nm, said layers being deposited so as to impart to the plating (12) a red interference colour characterised in the CIELAB colour space, illuminant D65, by an L* parameter comprised between 25 and 35, an a* parameter comprised between 8 and 15, and a b* parameter comprised between 0 and 7.

12. The manufacturing method according to claim 11, in which the reflective (121), transparent (122) and absorbent (123) layers 101, 102 and 103, respectively, are deposited using an electron beam physical vapour deposition method.

13. The manufacturing method according to any of claims 11 or 12, in which the transparent layer (122) deposition step 102 is carried out at a deposition velocity comprised between 0.01 nm / s and 0.1 nm / s.

14. The manufacturing method according to any of claims 11 or 13, in which the absorbent layer (123) deposition step 103 is carried out at a deposition velocity comprised between 0.01 nm / s and 0.05 nm / s.