Timepiece component or jewellery component and method for manufacturing such a timepiece component or jewellery component

Abstract

The present invention relates to a timepiece or jewellery component made entirely or partly of a material comprising between 37.5% and 95% by weight of a precious metal relative to the total weight of the material, wherein the material comprises a matrix derived from a thermoplastic resin, a thermosetting resin, or an elastomer, and at least some precious-metal-based particles dispersed in the matrix. The precious-metal-based particles have dimensions such that the maximum dimension of the precious-metal-based particles in the plane of the observed surface of the material is less than 100 μm, and the minimum dimension of the precious-metal-based particles in the plane of the observed surface of the material is greater than 1 nm, preferably greater than 10 nm, more preferably greater than 200 nm, still more preferably greater than 0.5 μm, and most preferably greater than 1 μm, wherein at least one of the matrix and the precious-metal-based particles is configured so as to exhibit a final hue predefined by its coordinates a*, b*, and L* in the CIE L*a*b* space, such that the colour difference ΔE* between the predefined final hue of at least one of the matrix and the precious-metal-based particles and the hue of the pure native precious metal is greater than 15, wherein the precious-metal-based particles are homogeneously dispersed in the matrix, and wherein the quantity of precious-metal-based particles dispersed in the matrix is predetermined so that, under the same illumination conditions using an illuminant, the material appears to exhibit a hue identical to, or close to, the predefined final hue of at least one of the matrix and the precious-metal-based particles to an observer positioned at a distance of at least 30 cm from the surface of the material, and wherein the hue of the material is such that the colour difference ΔE* between the hue of the material and the predefined final hue of at least one of the matrix and the precious-metal-based particles is less than 10, and such that the colour difference ΔE* between the hue of the material and the hue of the pure native precious metal is greater than 15.

Description

[0001] WATCHMAKING OR JEWELRY COMPONENT AND METHOD FOR MANUFACTURING SUCH A WATCHMAKING OR JEWELRY COMPONENT

[0002] technical field

[0003] The present invention relates to a watch or jewelry component in a material comprising between 37.5% and 95% by weight of a precious metal, inclusive, relative to the total weight of the material, said material comprising a matrix and at least particles based on said precious metal dispersed in the matrix.

[0004] The present invention also relates to a method for manufacturing such a watch or jewelry component.

[0005] State of the art

[0006] Precious metals, such as gold-based alloys, are commonly used in the manufacture of watch and jewelry components, either as a coating or in bulk form. These gold-based alloys are traditionally yellow, red, or gray. Watchmakers and jewelers are increasingly seeking to move beyond the natural color of gold and are particularly interested in developing gold alloys with different hues, such as dark or black. Such alloys can be achieved by depositing a black layer onto a gold material, for example, by electrodeposition with rhodium or ruthenium, or by chemical vapor deposition (CVD) with carbon black. Other processes utilize gold nanoparticles coated with at least one layer of a metal oxide, such as silicon dioxide, zirconium oxide, or titanium oxide, based on the plasmonic effect of the gold nanoparticles.

[0007] For example, patent EP 2,369,022 describes a process for manufacturing a bulk material containing at least 12-karat or even 18-karat gold, composed of silica-coated gold nanoparticles. The color of the gold nanoparticles used is adjusted according to their size, geometry (spherical, cylindrical, and pyramidal), composition, and chemical environment. The bulk material is obtained by heating and microwave irradiation, a process that preserves the specific color of the gold nanoparticles. However, the patent describes the preparation of a bright red gold nanoparticle solution, a purple solution of silica-coated gold nanoparticles, and a black pellet obtained after heating and microwave irradiation. Therefore, the described process does not guarantee the preservation of the nanoparticle color and is thus not sufficiently robust.

[0008] EP 3 482 851 describes a process for manufacturing a material containing at least 18 carats of gold, formed from an assembly of gold nanoparticles in a titanium dioxide matrix. However, this process is complex because it requires the use of solvents and heating the mixture in the reactor. Furthermore, due to the significant absorption or less-than-ideal optical properties of titanium dioxide for light transmission, the depth of light penetration through the material is insufficient to achieve the maximum plasmonic effect of the gold nanoparticles, so the color of the resulting material is not a deep black. In addition, it is stated that the powder obtained is black before the compaction and sintering steps, while after these two steps, the material is anthracite in color. The initial color of the nanoparticles is therefore altered.Furthermore, the mechanical properties of titanium dioxide, such as hardness or toughness, are not always sufficient to meet the specifications imposed depending on the components.

[0009] It has also been proposed to integrate plasmonic gold nanoparticles into a ceramic matrix, the whole then being sintered at temperatures above 800°C, or even above 1000°C, like a traditional ceramic, to obtain a composite material.

[0010] Here again, after sintering, an alteration in the color of the nanoparticles was observed, linked to their plasmonic effect. While not limited by theory, it is assumed that during sintering, which takes place at high temperature, the gold nanoparticles transform, grow, and coalesce, losing their plasmonic effect. This process therefore does not guarantee the preservation of the nanoparticles' color.

[0011] The present invention aims to remedy these drawbacks by proposing a watch or jewelry component in a material comprising between 37.5% and 95% by weight of a precious metal and which has a uniform predefined final shade, in particular a dark or black shade.

[0012] Another objective of the present invention is to propose a method for manufacturing a watch or jewelry component in a material comprising between 37.5% and 95% by weight of a precious metal, allowing the achievement of a predefined final color.

[0013] Another objective of the present invention is to propose a method for manufacturing a watch or jewelry component in a material comprising between 37.5% and 95% by weight of a precious metal, allowing for the simple production of a component comprising a precious metal, in particular gold, of a predefined color, such as a dark or black shade, and in particular deep black.

[0014] Disclosure of the invention

[0015] To this end, the invention relates to a watch or jewelry component made wholly or partly from a material comprising between 37.5% and 95% by weight of a precious metal, inclusive, relative to the total weight of the material, said material comprising a matrix from a material selected from the group comprising at least a thermoplastic resin, a thermosetting resin, and an elastomer, and at least particles based on said precious metal dispersed in the matrix.

[0016] According to the invention, said precious metal-based particles have dimensions such that the maximum dimension of said precious metal-based particles in the plane of the observed material surface is less than 100 pm, preferably less than 60 pm, preferably less than 50 pm, preferably less than 30 pm, and the minimum dimension of said precious metal-based particles in the plane of the observed material surface is greater than 1 nm, preferably greater than 5 nm, preferably greater than 10 nm, preferably greater than 100 nm, preferably greater than 200 nm, preferably greater than 0.5 pm, more preferably greater than 1 pm, at least one of the matrix and the precious metal-based particles being configured to exhibit a final hue predefined by its coordinates a*, b*,and L* in the CIE L*a*b* color space and such that the color difference AE* in the CIE L*a*b* color space between the predetermined final hue of said at least one of the matrix and precious metal-based particles and the hue of said pure native precious metal is greater than 15, preferably greater than 20, preferably greater than 50, more preferably greater than 100, said precious metal-based particles being dispersed homogeneously in the matrix, the quantity of precious metal-based particles dispersed in the matrix being predetermined so that said material appears to have the same or a similar hue to the predetermined final hue of said at least one of the matrix and precious metal-based particles to the same observer located at least 30 cm, and preferably at least 10 cm, from the surface of said material under the same illumination conditions by an illuminant,said tint of the material being such that the AE* color difference in the CIE L*a*b* color space between the tint of the material and the predefined final tint of said at least one of the matrix and precious metal-based particles is less than 10, preferably less than or equal to 5, preferably less than or equal to 4, and more preferably less than or equal to 3, more preferably less than or equal to 2, and more preferably less than or equal to 1, and such that the AE* color difference in the CIE L*a*b* color space between the tint of the material and the tint of the pure native precious metal is greater than 15, preferably greater than 20, preferably greater than 50, more preferably greater than 100.

[0017] Thus, the same observer placed at least 10 to 30 cm from the surface of the watch or jewelry component according to the invention will perceive, under the same conditions of illumination by an illuminant, a watch or jewelry component comprising between 37.5% and 95% by weight of a precious metal and which has a uniform overall color identical or close to the color of the matrix chosen at the start, by optical effect, and / or which has a uniform overall color identical or close to the color corresponding to the plasmonic effect of the precious metal-based particles chosen at the start.

[0018] For example, in the case where the final predefined shade of said at least one of the matrix and precious metal-based particles is black or dark as defined in the CIE L*a*b space by the parameters -10 <a*< 10, -10 <b*< 10 et 0 <L*< 50, de préférence -5 <a*< 5, -5 <b*< 5 et L*< 30, de préférence -5 <a*< 5, -5 <b*< 5 et L*< 15, un même observateur placé à au moins 10 à 30 cm de la surface du composant horloger ou de bijouterie selon l’invention percevra, dans les mêmes conditions d’illumination par un illuminant, un composant horloger ou de bijouterie comprenant entre 37,5% et 95% en poids d’un métal précieux et qui présente une couleur globale uniforme noire ou foncée telle que définie ci-dessus correspondant à la teinte finale prédéfinie dudit au moins l’un de la matrice et des particules à base du métal précieux.

[0019] The present invention also relates to a method for manufacturing a watch or jewelry component made wholly or partly from a material comprising between 37.5% and 95% by weight of a precious metal, inclusive, relative to the total weight of the material, said method comprising the following steps: a) providing a material for forming the matrix selected from the group comprising at least one thermoplastic resin, one thermosetting resin, and one elastomer; b) providing at least some initial precious metal-based particles; at least one of the matrix and the precious metal-based particles being configured to exhibit a final hue predefined by its coordinates a*, b*,and L* in the CIE L*a*b* color space and such that the color difference AE* in the CIE L*a*b* color space between the predefined final hue of said at least one of the matrix and precious metal-based particles and the hue of said pure native precious metal is greater than 15, preferably greater than 20, preferably greater than 50, more preferably greater than 100; (c) optionally supply at least one additional component intended to constitute between 0% and 10% by weight of the material, inclusive; (d) combine the material intended to form the matrix with the initial precious metal particles and optionally with said at least one additional component in order to obtain a homogeneous mixture of precious metal-based particles and optionally with said at least one additional component in the matrix; (e) produce by molding, from the mixture obtained in step (d), the watch component in whole or in part in a material comprising between 37,5% and 95% by weight of the precious metal, inclusive, relative to the total weight of the material, and wherein the precious metal-based particles have dimensions such that the maximum dimension of said precious metal-based particles in the plane of the observed material surface is less than 100 pm, preferably less than 60 pm, preferably less than 50 pm, preferably less than 30 pm, and the minimum dimension of said precious metal-based particles in the plane of the observed material surface is greater than 1 nm, preferably greater than 5 nm, preferably greater than 10 nm, preferably greater than 100 nm, preferably greater than 200 nm, preferably greater than 0.5 pm, and more preferably greater than 1 pm,and the quantity of precious metal particles dispersed in the matrix being predetermined such that said material appears to have the same or a similar hue to the predetermined final hue of said at least one of the matrix and the precious metal-based particles to the same observer placed at least 30 cm, and preferably at least 10 cm, from the surface of said material under the same illumination conditions by an illuminant, said hue of the material being such that the AE* color difference in the CIE L*a*b* color space between the hue of the material and the predetermined final hue of said at least one of the matrix and the precious metal-based particles is less than 10, preferably less than or equal to 5, preferably less than or equal to 4, more preferably less than or equal to 3, more preferably less than or equal to 2, and more preferably less than or equal to 1,and such that the AE* color difference in the CIE L*a*b* color space between the hue of the material and the hue of the pure native precious metal is greater than 15, preferably greater than 20, preferably greater than 50, and more preferably greater than 100.

[0020] Preferably, the material intended to form the matrix supplied in step a) is a thermosetting resin chosen from the group including epoxy resins, polyurethane resins, dimethacrylate urethane polymers (IIDMA), and crosslinked in step e) by a hardener, by the addition of heat or by photopolymerization.

[0021] The use of a matrix made from a material selected from a group comprising at least one thermoplastic resin, one thermosetting resin, and one elastomer advantageously eliminates the sintering step traditionally used in the manufacture of a composite material comprising a ceramic matrix. Step e) of the process of the invention can therefore advantageously be carried out at temperatures below 500°C instead of above 800°C for sintering. Thus, the precious metal-based particles are not exposed to temperatures close to or even above their melting point, so they will not be altered during the production of the material. In particular, their dimensions and shapes will be preserved.Therefore, particularly with regard to precious metal nanoparticles with a plasmonic effect, these nanoparticles will not be transformed during the manufacturing of the material and will not lose their plasmonic effect. Similarly, when an optical effect is desired, the sizes of the precious metal-based particles mixed in the matrix will not be altered during the material's production. Thus, the process of the invention advantageously ensures the preservation of the characteristics and properties of the precious metal-based particles within the material.

[0022] Such manufacturing processes are also simple to implement.

[0023] Brief description of the drawings

[0024] Other features and advantages of the present invention will become apparent from the following detailed description of various embodiments of the invention, given by way of non-limiting examples, and made with reference to the attached drawing in which: Figure 1 schematically represents the steps of the process according to the invention.

[0025] Embodiments of the invention

[0026] The present invention relates to a watch or jewelry component made wholly or partly from a material comprising between 37.5% and 95% by weight of a precious metal, including the limits, relative to the total weight of the material. Such a watch or jewelry component consists, for example, of a watch casing element, such as a dial, a cover, an appliqué, a crown, a hand, a case, a bracelet element, all or part of these components, as well as a decorative element, for example, or a piece of jewelry.

[0027] The said material of the watch or jewelry component comprises a matrix and at least particles based on said precious metal dispersed in the matrix.

[0028] The matrix is ​​advantageously derived from a material selected from the group comprising at least one thermoplastic resin, one thermosetting resin, and one elastomer.

[0029] Preferably, the matrix is ​​made from a thermosetting resin selected from the group comprising epoxy resins, polyurethane resins, and dimethacrylate urethane polymers (UDMA). The thermosetting resin is crosslinked by a suitable crosslinking system depending on its nature. In particular, the thermosetting resin is crosslinked by a suitable chemical crosslinking agent, such as a hardener, by the application of heat or by irradiation, notably by photopolymerization, for example by UV light. Different crosslinking systems can be combined. For example, a hardener can be combined with a temperature increase. The crosslinking reaction advantageously takes place at temperatures below approximately 500°C and can be carried out under a controlled atmosphere and / or under controlled pressure.

[0030] The thermoplastic resin can be, for example, polypropylene (PP), polyetheretherketone (PEEK), polysulfone (PSU), or polyamide (PA).

[0031] The elastomer can be a natural rubber, a silicone rubber, a fluoroelastomer (FKM), a thermoplastic elastomer (TPE), a styrene-butadiene rubber (SBR), a butyl rubber.

[0032] Preferably, the particles based on said precious metal used in the invention are particles based on gold, silver, palladium, platinum, rhodium, and mixtures thereof. Preferably, the particles based on said precious metal are gold-based particles, and the material preferably comprises between 37.5% and 75% gold by weight relative to the total weight of the material, i.e., preferably between 9 and 18 carats. If the particles based on said precious metal are platinum-based particles, the material may preferably comprise between 37.5% and 95% platinum by weight relative to the total weight of the material.

[0033] It is specified that, in this description, the expression "based on said precious metal" means that the particle "based on said precious metal" comprises, by weight, said precious metal. This precious metal may constitute 100% of the particle, in which case the particle is a pure particle of said precious metal. These particles may also be in the form of an alloy comprising, by weight, said precious metal and another metal, which may itself be a precious metal or not, for example, as will be described below. Furthermore, the composition of the alloy is determined in such a way as to meet the required purities.According to the invention, said particles based on said precious metal in the material have dimensions such that the maximum dimension of the particles based on said precious metal in the plane of the observed surface of the material is less than 100 pm, preferably less than 60 pm, preferably less than 50 pm, preferably less than 30 pm, preferably less than 20 pm, preferably less than 10 pm, preferably less than 5 pm, and the minimum dimension of said particles based on said precious metal in the plane of the observed surface of the material is greater than 1 nm, preferably greater than 5 nm, preferably greater than 10 nm, preferably greater than 50 nm, preferably greater than 100 nm, preferably greater than 200 nm, preferably greater than 0.5 pm, and more preferably greater than 1 pm.

[0034] In the present invention, the size or dimension of a particle is defined as its equivalent diameter, that is, the diameter of the sphere that would behave identically during particle size analysis of the particles (or of the powder formed from said particles or agglomerates of these powders), the particle size distribution (the set of particle sizes) being measured in particular by laser granulometry according to ISO 13320:2009. For example, if the particles are spherical, the diameter in the plane of the observed surface of the material is the diameter of the spheres. If the particles have another shape, for example pyramidal, the largest surface area of ​​the particle in the plane of the observed surface of the material can be determined.

[0035] The particle sizes indicated in this application correspond to the D95 percentile, meaning that 95% of the particles (or agglomerates of these particles) in the set of particles considered have a size less than D95.

[0036] Furthermore, the particles based on said precious metal of the material of the watch or jewelry component are dispersed homogeneously in the matrix, that is to say in the mass.

[0037] Furthermore, the matrix and particles based on said precious metal are chosen such that at least one of the matrix and particles based on the precious metal is configured to exhibit a final hue predefined by its coordinates a*, b*, and L* in the CIE L*a*b* space and such that the color difference AE* in the CIE L*a*b* color space between the final predefined hue of said at least one of the matrix and particles based on the precious metal and the hue of said pure native precious metal (i.e., the hue of the metal in its pure state in its traditional form and in standard dimensions) is greater than 15, preferably greater than 20, preferably greater than 50, more preferably greater than 100.

[0038] Furthermore, the quantity of particles based on said precious metal dispersed in the matrix, and whose size is within the limits indicated above, is predetermined during the manufacture of said component so that said material has the desired fineness and such that said material appears to have a hue identical or close to the predetermined final hue of said at least one of the matrix and the particles based on the precious metal to the same observer placed at least 30 cm, and preferably at least 10 cm, from the surface of said material under the same illumination conditions by an illuminant, said hue of the material being such that the AE* color difference in the CIE L*a*b* color space between the hue of the material and the predetermined final hue of said at least one of the matrix and the particles based on the precious metal, taken alone, is less than 10, preferably less than or equal to 8, preferably less than or equal to 7,preferably less than or equal to 5, preferably less than or equal to 4, more preferably less than or equal to 3, more preferably less than or equal to 2, and more preferably less than or equal to 1, and such that the AE* color difference in the CIE L*a*b* color space between the hue of the material and the hue of the pure native precious metal is greater than 15, preferably greater than 20, preferably greater than 50, more preferably greater than 100.

[0039] In a particularly preferred manner, the predefined final tint of at least one of the matrix and precious metal-based particles is a dark or black tint, such that the material comprising the matrix and the precious metal particles dispersed in the matrix appears dark or black. In the present invention, a dark or black tint means a color defined in the CIE L*a*b* color space by the parameters -10 <a*< 10, -10 <b*< 10 et 0 <L*< 50, de préférence -5 <a*< 5, -5 <b*< 5 et L*< 30, de préférence -5 <a*< 5, -5 <b*< 5 et L*< 15, plus préférentiellement -1 <a*< 1 , -1 <b*< 1 et 0 < L*< 10, et plus préférentiellement -1 <a*< 1 , -1 < b*< 1 et 0< L*< 6.

[0040] The color difference or AE* color deviation in the CIE L*a*b* color space is defined as a measure of difference between two colors by equation (I):

[0041] L, a^, b are the coordinates in the CIE L*a*b* color space of the first color to be compared and L2, ci 2, b2 are the coordinates in the CIE L*a*b* color space of the second color to be compared.

[0042] These values ​​L, a, and L2, a2, b2 in the CIE L*a*b* color space are measured objectively using a colorimeter under the same illumination conditions by a standardized illuminant of type D65.

[0043] An AE* color difference between two colors of less than 10, preferably less than or equal to 8, preferably less than or equal to 7, preferably less than or equal to 5, preferably less than or equal to 4, more preferably less than or equal to 3, more preferably less than or equal to 2, and more preferably less than or equal to 1, measured objectively using a colorimeter, indicates that the two colors are almost or even identical to the same observer under the same illumination conditions by an illuminant.

[0044] When said at least one of the matrix and precious metal-based particles configured to exhibit the predefined final tint is the matrix, the colorimeter measures the tint (coordinates a*, b*, and L*) of a sample of a material made in a similar manner to the material used in the invention but comprising only the matrix, without precious metal-based particles, and the tint (coordinates a*, b*, and L*) of a sample corresponding to the projection of a sample of the material used in the invention into a parallel plane placed at least 30 cm, and preferably at least 10 cm, from the surface of said material, and compares the two tints to calculate the color difference AE* between the two samples.

[0045] Thus, the said material of the watch or jewelry component will have the desired purity and will appear, in the mass, to be of the same or close hue to the predefined final hue of the matrix to the same observer placed at least 30 cm, and preferably at least 10 cm, from the surface of said material, under the same illumination conditions by an illuminant, by an optical effect, the particles based on the precious metal, and in particular the gold-based particles, without plasmonic effect, of dimensions such that the maximum dimension of the particles based on said precious metal in the plane of the observed surface of the material is preferably less than 100 pm and the minimum dimension of said particles based on said precious metal in the plane of the observed surface of the material is greater than 100 nm, preferably greater than 150 nm, or even 200 nm, visually blending with the matrix, an observer perceiving the surface of the material as being a uniform surface,for example, a dark or black shade, corresponding to the predefined final shade of the matrix.

[0046] When said at least one of the matrix and precious metal-based particles configured to exhibit the predefined final hue is made up of precious metal-based particles, the colorimeter measures the hue (coordinates a*, b*, and L*) of a sample of said precious metal-based particles chosen in a form enabling them to exhibit said predefined final hue, and the hue (coordinates a*, b*, and L*) of a sample corresponding to the projection of a sample of the material used in the invention onto a parallel plane placed at least 30 cm, and preferably at least 10 cm, from the surface of said material, and compares the two hues to calculate the color difference AE* between the two samples.

[0047] In the present invention, the illuminant is standardized to type D65, as defined in the CIE class of standard illuminants. It is also specified that the present invention relates only to optical effects in the visible range of the spectrum, defined between 400 nm and 790 nm.In a first embodiment of the invention, said at least one of the matrix and the precious metal-based particles configured to exhibit the predefined final hue is the matrix, said matrix comprising, if necessary, a coloring agent chosen to give the matrix said predefined final hue, and the precious metal-based particles are plasmonic-free, and of hue such that the AE* color difference in the CIE L*a*b* color space between the predefined final hue of the matrix and the hue of the precious metal-based particles in the matrix is ​​greater than 15, preferably greater than 20, preferably greater than 50, more preferably greater than 100.

[0048] In this first embodiment, the predefined final hue of the matrix can be arbitrary. The size and quantity of precious metal-based particles, particularly gold-based particles, without plasmonic effect, are selected and adjusted within the limits indicated above by a person skilled in the art to obtain, through an optical effect, a material with the desired fineness and the desired AE* value, as defined above. For example, in the case of gold-based particles, pure yellow gold particles are defined in the CIE L*a*b* color space by the parameters L* = 86.9, a* = -1.9, b* = 87.1. This means that the AE* color difference in the CIE L*a*b* color space between the predefined final hue of the matrix alone and the hue of pure yellow gold particles can be greater than 15, preferably greater than 20, preferably greater than 50, or even 80, or even 100.Thus, by an optical effect, the tint of the material perceived by the same observer placed at least 30 cm, and preferably at least 10 cm, from the surface of said material, under the same conditions of illumination by an illuminant, is such that the AE* color difference in the CIE L*a*b* color space between the tint of the material and the predefined final tint of the matrix taken alone is less than 10, preferably less than or equal to 8, preferably less than or equal to 7, preferably less than or equal to 5, preferably less than or equal to 4, more preferably less than or equal to 3, more preferably less than or equal to 2, and more preferably less than or equal to 1, whereas the AE* color difference in the CIE L*a*b* color space between the tint of the material and the tint of pure native gold is greater than 15, preferably greater than 20, preferably greater than 50, more preferably greater than 100.

[0049] Therefore, in this first embodiment, the maximum size of the precious metal-based particles, and in particular the gold-based particles, in the plane of the observed material surface is less than 100 pm, preferably less than 60 pm, preferably less than 50 pm, preferably less than 30 pm, preferably less than 20 pm, preferably less than 10 pm, and more preferably less than 5 pm. The minimum size of the precious metal-based particles, and in particular the gold-based particles, in the plane of the observed material surface can be greater than 200 nm, preferably greater than 0.5 pm, and more preferably greater than 1 pm, so that the precious metal-based particles, and in particular the gold-based particles formed in the material, are micrometer-sized and have no plasmonic effect, the material's color being obtained by an optical effect.It is also possible that the minimum dimension of the precious metal-based particles, and in particular the gold-based particles, in the plane of the observed material surface is greater than 1 nm and less than 200 nm, but due to the distance between particles, their sizes or other reasons occurring during the manufacture of the material, the plasmonic effect does not occur for these precious metal-based particles, and in particular for these gold-based particles, so that, for these precious metal-based particles, and in particular for these gold-based particles, the color of the material is linked solely to an optical effect.Thus, by an optical effect, and depending on the resolving power of his eye, an observer no longer perceives the particles based on the precious metal, and in particular the gold-based particles embedded in the matrix of predefined final tint, for example dark or black, and perceives the surface of the material as a uniform surface, for example dark or black, corresponding to the predefined final tint of the matrix.

[0050] In a second embodiment, said at least one of the matrix and the precious metal-based particles configured to exhibit the predefined final hue consists of the precious metal-based particles, said precious metal-based particles being nanoparticles which have dimensions and shapes giving them a plasmonic effect corresponding to the predefined final hue at least in the visible range.

[0051] Preferably, the precious metal-based particles are nanoparticles with dimensions less than 200 nm, preferably between 10 nm and 200 nm, or even dimensions less than 150 nm or 100 nm, giving them the said plasmonic effect, while being invisible to the naked eye.

[0052] Advantageously, the matrix may include, in this second embodiment, a coloring agent chosen to give the matrix a tint such that the color difference AE* in the CIE L*a*b* color space between the tint of the colored matrix and the predefined final tint of said precious metal-based particles is less than 10, preferably less than or equal to 5, preferably less than or equal to 4, more preferably less than or equal to 3, more preferably less than or equal to 2, and more preferably less than or equal to 1.

[0053] The final predefined hue associated with precious metal-based particles depends on the hue obtained through the plasmonic effect generated by said particles. The quantity of precious metal-based particles, and in particular gold-based particles with plasmonic effect, and the hue of the matrix are chosen and adjusted within the limits indicated above by a person skilled in the art to obtain, notably through the plasmonic effect associated with the precious metal-based particles, a material with the desired fineness and the desired AE* value, as defined above. For example, in the case of gold-based particles, pure yellow gold particles are defined in the CIE L*a*b* color space by the parameters L* = 86.9, a* = -1.9, b* = 87.1. This means that the difference in AE* color in the CIE L*a*b* color space between the final predefined hue of gold-based nanoparticles, generated by their plasmonic effect,and the tint of pure yellow gold particles can be greater than 15, preferably greater than 20, preferably greater than 50, or even 80, or even 100. And in particular thanks to this plasmonic effect of the precious metal nanoparticles, which have the dimensions defined above and are invisible to the naked eye, and to the choice of a resin of appropriate tint, the tint of the material perceived by the same observer placed at least 30 cm, and preferably at least 10 cm, from the surface of said material, under the same illumination conditions by an illuminant, is such that the AE* color difference in the CIE L*a*b* color space between the tint of the material and the predefined final tint of the gold-based nanoparticles is less than 10, preferably less than or equal to 8, preferably less than or equal to 7, preferably less than or equal to 5, preferably less than or equal to 4, more preferably less than or equal to 3,more preferably less than or equal to 2, and more preferably less than or equal to 1, whereas the AE* color difference in the CIE L*a*b* color space between the hue of the material and the hue of pure native gold is greater than 15, preferably greater than 20, preferably greater than 50, more preferably greater than 100.

[0054] Regardless of the embodiment, when the matrix includes a coloring agent to give the matrix the predefined final shade or a shade close to or identical to the predefined final shade of the precious metal-based particles, said coloring agent may be a pigment, for example in the form of oxides or salts, in particular metallic oxides or salts such as chromium oxide, iron oxide, cobalt oxide, carbonates, sulfates, mica powder, or in the form of carbon, for example nanotubes or carbon black, particularly suitable for giving a black or dark shade. Said coloring agent may also be an organic dye or pigment.

[0055] Preferably, the coloring agent is chosen to give the matrix a final dark or black tint, said coloring agent being, for example, carbon black, carbon nanotubes, and / or at least a suitable oxide.

[0056] Regardless of embodiments, the precious metal-based particles may comprise said precious metal and at least one other metal, the amount of said other metal being chosen so that the hue of the precious metal-based particles in the matrix is ​​such that the AE* color difference in the CIE L*a*b* color space between the final hue of the matrix and the hue of the precious metal-based particles is less than the AE* color difference in the CIE L*a*b* color space between the final hue of the matrix and the hue of the pure native precious metal.

[0057] Preferably, the other metal is palladium, platinum, iridium, ruthenium, nickel, iron, chromium, silver, copper, zinc, rhodium, aluminum, tin, indium, magnesium, manganese, titanium, zirconium, or osmium, the other metal being chosen according to the precious metal to be alloyed and the desired hue. For example, gold can be alloyed with palladium, platinum, nickel, iron, chromium, manganese, zinc, or rhodium to change from the standard yellow color of pure native yellow gold to a whiter hue.

[0058] The use of such an alloyed precious metal is particularly advantageous in the first embodiment because it allows the precious metal-based particles to achieve a hue that closely matches the predetermined final color of the matrix. For example, with gold-based particles, without plasmonic effects, using gold alloyed with one of the metals mentioned above reduces the yellow or reddish color of the gold particles, resulting in a more neutral color than the yellow gold of pure native gold.

[0059] In the second embodiment, the use of such an alloyed precious metal is also advantageous because it allows the precious metal-based particles, which might otherwise lose their plasmonic effect during the material's manufacture, to have a more neutral hue than the pure native precious metal, by reducing the yellow or reddish color of the gold particles that have lost their plasmonic effect. Nanoparticles can lose their plasmonic effect due to their size, for example, due to agglomeration, lighting, or other conditions. Gold-based nanoparticles can, for example, comprise a core made of one of the metals mentioned above and a gold shell.

[0060] Regardless of the embodiment, the material may also comprise between 0% and 10% by weight, inclusive, of at least one additional component, such as reinforcing fillers like carbon fibers, a coupling agent, a ceramic, or any other additive that allows for adjusting the chemical, physical, or rheological properties of the composition. Such additional components may be chosen to improve particle distribution, viscosity, or adhesion between material components, such as the matrix and precious metal-based particles.

[0061] Advantageously, this additional component is a ceramic in the form of nano- or microparticles. Preferably, the ceramic nano- or microparticles are made of alumina, zirconia, or silica, for example. They improve mechanical strength, particularly scratch resistance. Preferably, ceramic nanoparticles are used so that they are invisible to the naked eye while improving the overall properties of the material. For example, they produce smoother surfaces. These ceramic nanoparticles can be pigmented or can acquire color under various conditions (e.g., oxidation, carbon addition during the process or by post-processing) and can also be used to adjust the color of the matrix.

[0062] Preferably, according to the first embodiment, the matrix is ​​derived from a thermosetting resin of a predetermined dark or black final shade, and the precious metal-based particles are at least gold-based particles without plasmonic effect, having the dimensions defined above and in the predetermined quantity as defined above, the matrix also comprising various additives, including ceramic nano- or micro-particles, and preferably ceramic nanoparticles, and reinforcing fillers, such as carbon fibers.

[0063] Preferably, according to the second embodiment, the matrix is ​​made from a thermosetting resin, which may optionally have a predefined dark or black final color, and the precious metal-based particles are at least gold-based nanoparticles with a predefined dark or black final color achieved through plasmonic coagulation. The matrix also comprises various additives, including ceramic nano- or microparticles, and preferably ceramic nanoparticles and reinforcing fillers, such as carbon fibers. Thus, all the particles present in the matrix, i.e., at least the gold-based particles and the ceramic particles, are of nanometric dimensions and are therefore invisible to the naked eye. For example, a composition for obtaining a material containing 18k gold as described above comprises, by weight relative to the total weight of the composition:

[0064] - at least 75% by weight of gold in the form of plasmonic nanoparticles generating a black tint and / or in the form of microparticles intended to cooperate with the matrix by optical effect, as described above;

[0065] - between 5 and 24% by weight of black-tinted thermosetting resin, as described above;

[0066] - between 1 and 10% by weight of ceramic nanoparticles, as described above;

[0067] - between 0 and 10% by weight of other additives, as described above.

[0068] It is quite clear that the two embodiments of optical effect / plasmonic effect described above can be combined. For example, the resin configured to exhibit the predefined final tint, constituting the matrix, may comprise, dispersed in said matrix, first particles based on precious metal, in particular gold-based, of micrometric size, as defined above, enabling the tint to be obtained essentially by optical effect in cooperation with the matrix, as well as second particles based on precious metal, in particular gold-based, of nanometric size, chosen to exhibit a plasmonic effect of a tint identical or close to that of the matrix in order to promote the tint of the matrix and to reinforce the optical effect obtained with the first particles based on precious metal, in particular gold-based.The material obtained comprising the first and second particles based on the precious metal, in particular based on gold dispersed in the matrix has the desired fineness by the contribution of the first and second particles and a tint such that the color difference AE* is always as defined above.

[0069] The quantity of precious metal-based particles, particularly gold-based particles, dispersed in the matrix is ​​predetermined so that the material has the desired purity. With reference to Figure 1, the present invention relates to a method for manufacturing a watch or jewelry component as described above, here for example, of a dark or black tint, said method comprising the following steps: a) providing a material for forming the matrix selected from the group comprising at least one thermoplastic resin, one thermosetting resin, and one elastomer; b) providing at least some initial precious metal-based particles, particularly gold-based particles; at least one of the matrix and the precious metal-based particles being configured to have a final tint predefined by its coordinates a*, b*,and L* in the CIE L*a*b* color space and such that the color difference AE* in the CIE L*a*b* color space between the predefined final hue of said at least one of the matrix and the precious metal-based particles and the hue of said pure native precious metal is greater than 15, preferably greater than 20, preferably greater than 50, more preferably greater than 100; (c) optionally supply at least one additional component intended to constitute between 0% and 10% by weight of the material, inclusive; (d) combine the material intended to form the matrix supplied in step (a) with the initial precious metal-based particles supplied in step (b) and optionally with said at least one additional component supplied in step (c), in order to obtain a homogeneous mixture of precious metal-based particles, in particular gold-based, and optionally with said at least one additional component in the matrix; (e) produce by molding,from the mixture obtained in step d), the watch component, in whole or in part, made of a material comprising between 37.5% and 95% by weight of the precious metal, inclusive, relative to the total weight of the material, and in which the precious metal-based particles, in particular gold-based particles, have dimensions such that the maximum dimension of said precious metal-based particles, in particular gold-based particles, in the plane of the observed surface of the material is less than 100 pm, preferably less than 60 pm, preferably less than 50 pm, preferably less than 30 pm, and the minimum dimension of said precious metal-based particles, in particular gold-based particles, in the plane of the observed surface of the material is greater than 1 nm, preferably greater than 5 nm, preferably greater than 10 nm, preferably greater than 50 nm, preferably greater than 100 nm, preferably greater than 200 nm, preferably greater than 0.5 pm,and more preferably greater than 1 pm, the matrix and particle size, within the limits indicated above, being chosen and the quantity of precious metal-based particles, and in particular gold-based particles, dispersed in the matrix having been predetermined in step b) so that said material has the desired fineness and such that said material appears to have the same or close hue to the predetermined final hue of said at least one of the matrix and precious metal-based particles, here for example dark or black, to the same observer placed at least 30 cm, and preferably at least 10 cm, from the surface of said material under the same illumination conditions by an illuminant, said hue of the material being such that the AE* color difference in the CIE L*a*b* color space between the hue of the material and the predetermined final hue of said at least one of the matrix and precious metal-based particles, taken alone,is less than 10, preferably less than or equal to 8, preferably less than or equal to 7, preferably less than or equal to 5, preferably less than or equal to 4, more preferably less than or equal to 3, more preferably less than or equal to 2, and more preferably less than or equal to 1, and such that the AE* color difference in the CIE L*a*b* color space between the hue of the material and the hue of the pure native precious metal is greater than 15, preferably greater than 20, preferably greater than 50, more preferably greater than 100.

[0070] In a preferred embodiment, the final predefined shade of said at least one of the matrix and precious metal-based particles is globally uniformly dark or black and is defined by its coordinates a*, b*, and L* in CIE L*a*b* space such that -10 <a*< 10, -10 <b*< 10 et 0 <L*< 50, de préférence -5 <a*< 5, -5 <b*< 5 et 0 <L*< 30, et plus préférentiellement -5 <a*< 5, -5 <b*< 5 et L*< 15.

[0071] As described above for the watch or jewelry component, according to a first embodiment, said at least one of the matrix and the precious metal-based particles configured to exhibit the predefined final hue is the matrix, said matrix comprising, if necessary, a coloring agent selected to give the matrix said predefined final hue, and the precious metal-based particles are plasmonic-free, and of hue such that the AE* color difference in the CIE L*a*b* color space between the hue of the matrix and the hue of the precious metal-based particles in the matrix is ​​greater than 15, preferably greater than 20, preferably greater than 50, more preferably greater than 100.

[0072] Preferably, the precious metal-based particles, especially gold-based, initials provided in step b) have dimensions between 1 nm and 1 pm, for example between 10 nm and 1 pm.The dimensions of the initial precious metal-based particles are chosen so that the precious metal-based particles formed in the matrix have the desired dimensions, i.e. dimensions such that the maximum dimension of the gold particles in the plane of the observed material surface is less than 100 pm, preferably less than 60 pm, preferably less than 50 pm, preferably less than 30 pm, preferably less than 20 pm, preferably less than 10 pm, preferably less than 5 pm, and the minimum dimension of the precious metal-based particles in the plane of the observed material surface is greater than 1 nm, preferably greater than 10 nm, preferably greater than 50 nm, preferably greater than 100 nm, preferably greater than 200 nm, preferably greater than 0.5 pm, and more preferably greater than 1 pm.Indeed, the dimensions of the initial precious metal-based particles can increase due to the agglomeration of the precious metal-based particles during the manufacturing of the component.

[0073] The initial precious metal-based particles supplied in step b) may be in pure metal form, for example 24-carat pure gold, or in an alloyed form, notably to attenuate the hue of the pure metal, as described above.

[0074] According to the second embodiment, said at least one of the matrix and the precious metal-based particles configured to exhibit the predefined final tint consists of the precious metal-based particles, said precious metal-based particles supplied in step b) being nanoparticles which have dimensions and shapes giving them a plasmonic effect corresponding to the predefined final tint at least in the visible range, while being invisible to the naked eye.

[0075] Advantageously, the quantity of initial precious metal-based particles supplied in step b) is determined from the quantity of precious metal-based particles in the material which is predetermined by prior tests using a colorimeter in order to establish a correlation between the particle size of the precious metal-based particles formed in the material, the desired color of the material, the desired fineness, and the volume ratio between the precious metal-based particles and matrix 2.

[0076] The material intended to form the matrix, supplied in step a), is a thermosetting resin selected from the group comprising epoxy resins, polyurethane resins, and urethane dimethacrylate polymers (UDMA), and configured to crosslink in step e) by a hardener, by the application of heat, or by photopolymerization. Depending on the crosslinking system chosen, the material intended to form the matrix supplied in step a) may also include a hardener, an initiator, and a polymerization catalyst, which is mixed with the resin in step a). The use of a matrix made from a material selected from the group comprising at least one thermoplastic resin, one thermosetting resin, and one elastomer advantageously eliminates the sintering step traditionally used in the manufacture of a composite material comprising a ceramic matrix.Step e) of the process of the invention can therefore advantageously be carried out at temperatures below 500°C instead of above 800°C for sintering. Thus, the precious metal-based particles are not exposed to temperatures close to or even above their melting point, so they will not be transformed during the fabrication of the material. In particular, their dimensions and shapes will be preserved. Consequently, especially with regard to precious metal nanoparticles with a plasmonic effect, these nanoparticles will not be transformed during the fabrication of the material and will not lose their plasmonic effect. Similarly, when an optical effect is desired, the sizes of the precious metal-based particles mixed in the matrix will not be altered during the fabrication of the material.Thus, the process of the invention advantageously guarantees the preservation of the characteristics and properties of the precious metal-based particles in the material.

[0077] Furthermore, using a matrix made from a material chosen from the group including at least one thermoplastic resin, one thermosetting resin, and one elastomer allows for a low-density matrix, on the order of 1 g / cm³. 3 , so that the possible volume for the non-precious phase of the material is increased, which is particularly advantageous in the first embodiment.

[0078] The additional components supplied in step c) are those described above for the watch or jewelry component.

[0079] Step d) can preferably be carried out by progressively incorporating the precious metal-based particles supplied in step b) and optionally at least one additional component, such as ceramic micro- or nanoparticles, into the resin supplied in step a) using a mechanical mixer to ensure homogeneous mixing. The precious metal-based particles, particularly the nanoparticles, can be supplied by a solvent, in the form of a colloidal suspension.

[0080] Between steps d) and e), it is possible to carry out a pretreatment which, for example, allows for at least one cycle of removal of inaccessible chemical substances before molding. This pretreatment can be performed by pressure treatment, vacuum treatment, heat treatment, or a combination of these processes.

[0081] When the resin is a thermosetting resin, step e) is carried out by molding, using a suitable mold, by pouring the mixture prepared in step d) into said mold, and applying the chosen curing system. For example, the mixture can be left to harden in the mold at room temperature.

[0082] When the resin is a thermoplastic resin, step e) can be carried out by injection molding.

[0083] Step e) may include post-processing, for example mechanical machining and / or finishing treatment, such as sanding and / or polishing the surface of the component, to obtain said watch or jewelry component.

[0084] In the embodiment where the matrix has a predefined final shade of black or dark, the present invention advantageously makes it possible to obtain a watch or jewelry component made wholly or partly from a material comprising between 37.5% and 95% by weight of a precious metal relative to the total weight of the material, inclusive, said material appearing to an observer placed at least 30 cm, and preferably at least 10 cm, from the surface of said material, as having a uniform overall color defined in CIE L*a*b* space by its coordinates a*, b*, and L* in CIE L*a*b* space such as, for example, -10

Claims

Demands 1. A watch or jewelry component made wholly or partly from a material comprising between 37.5% and 95% by weight of a precious metal, inclusive, relative to the total weight of the material, said material comprising a matrix derived from a material selected from the group comprising at least one thermoplastic resin, one thermosetting resin, and one elastomer, and at least particles based on said precious metal dispersed in the matrix, characterized in that said particles based on the precious metal have dimensions such that the maximum dimension of said particles based on the precious metal in the plane of the observed surface of the material is less than 100 pm, preferably less than 60 pm, preferably less than 50 pm, preferably less than 30 pm, and the minimum dimension of said particles based on the precious metal in the plane of the observed surface of the material is greater than 1 nm, preferably greater than 5 nm,preferably greater than 10 nm, preferably greater than 100 nm, preferably greater than 200 nm, preferably greater than 0.5 pm, and more preferably greater than 1 pm, in that at least one of the matrix and the precious metal-based particles is configured to exhibit a final hue predefined by its coordinates a*, b*, and L* in the CIE L*a*b* color space and such that the color difference AE* in the CIE L*a*b* color space between the predefined final hue of said at least one of the matrix and the precious metal-based particles and the hue of said pure native precious metal is greater than 15, preferably greater than 20, preferably greater than 50, more preferably greater than 100, in that the precious metal-based particles are homogeneously dispersed in the matrix,and in that the quantity of precious metal-based particles dispersed in the matrix is ​​predetermined so that said material appears to be of the same or close hue to the predetermined final hue of said material, at least one of the matrix and the precious metal-based particles, to the same observer placed at least 30 cm, and preferably at least 10 cm, from the surface of said material, in, the same illumination conditions by an illuminant, said tint of the material being such that the AE* color difference in the CIE L*a*b* color space between the tint of the material and the predefined final tint of said at least one of the matrix and precious metal-based particles is less than 10, preferably less than or equal to 5, preferably less than or equal to 4, more preferably less than or equal to 3, more preferably less than or equal to 2, and more preferably less than or equal to 1, and such that the AE* color difference in the CIE L*a*b* color space between the tint of the material and the tint of the pure native precious metal is greater than 15, preferably greater than 20, preferably greater than 50, more preferably greater than 100.

2. A watch or jewelry component according to claim 1, characterized in that the predefined final shade of said at least one of the matrix and precious metal-based particles is dark or black and is defined by its coordinates a*, b*, and L* in CIE L*a*b* space such that -10 <a*< 10, -10 <b*< 10 et 0 <L*< 50, de préférence -5 <a*< 5, -5 <b*< 5 et 0 <L*< 30, et plus préférentiellement -5 <a*< 5, -5 <b*< 5 et L*< 15.

3. A watch or jewelry component according to any one of the preceding claims, characterized in that said at least one of the matrix and precious metal-based particles configured to exhibit the predefined final hue is the matrix, said matrix comprising a coloring agent selected to give the matrix said predefined final hue, and in that the precious metal-based particles are plasmonic-free and of such a hue that the AE* color difference in the CIE L*a*b* color space between the predefined final hue of the matrix and the hue of the precious metal-based particles in the matrix is ​​greater than 15, preferably greater than 20, preferably greater than 50, more preferably greater than 100.

4. A watch or jewelry component according to any one of the preceding claims, characterized in that said component, at least one of the matrix and precious metal-based particles, is configured to exhibit the final hue. predefined is made up of particles based on the precious metal, said particles based on the precious metal being nanoparticles which have dimensions and shapes giving them a plasmonic effect corresponding to the final predefined tint at least in the visible range.

5. Watch or jewelry component according to claim 4, characterized in that the precious metal-based particles are nanoparticles with dimensions less than 200 nm, preferably between 10 nm and 200 nm.

6. Watch or jewelry component according to any one of claims 4 and 5, characterized in that the matrix comprises a coloring agent chosen to give the matrix a tint such that the color difference AE* in the CIE L*a*b* color space between the tint of the colored matrix and the predefined final tint of said precious metal-based particles is less than 10, preferably less than or equal to 5, preferably less than or equal to 4, more preferably less than or equal to 3, more preferably less than or equal to 2, and more preferably less than or equal to 1.

7. A watch or jewelry component according to any one of the preceding claims, characterized in that the precious metal-based particles comprise said precious metal and at least one other metal, the quantity of said other metal being chosen so that the tint of the precious metal-based particles in the matrix is ​​such that the AE* color difference in the CIE L*a*b* color space between the final tint of the matrix and the tint of the precious metal-based particles is less than the AE* color difference in the CIE L*a*b* color space between the final tint of the matrix and the tint of the pure native precious metal.

8. Watch or jewelry component according to claim 7, characterized in that said other metal is palladium, platinum, iridium, ruthenium, nickel, iron, chromium, silver, copper, zinc, rhodium, aluminum, tin, indium, magnesium, manganese, titanium, zirconium, osmium, said other metal being chosen according to said precious metal.

9. Watchmaking or jewelry component according to any one of the preceding claims, characterized in that the matrix is ​​derived from a thermosetting resin selected from the group comprising epoxy resins, polyurethane resins, dimethacrylate urethane polymers (IIDMA), and crosslinked by a hardener, by the addition of heat or by photopolymerization.

10. Watchmaking or jewelry component according to any one of the preceding claims, characterized in that the precious metal-based particles are particles based on gold, silver, palladium, platinum, rhodium, and mixtures thereof.

11. Watchmaking or jewelry component according to any one of claims 3 to 10, characterized in that the coloring agent is a pigment or dye.

12. Watch or jewelry component according to claim 11, characterized in that the coloring agent is chosen to give the matrix a final dark or black tint, said coloring agent being carbon black, carbon nanotubes, and / or at least one oxide.

13. Watchmaking or jewelry component according to any one of claims 2 to 12, characterized in that the matrix is ​​derived from a thermosetting resin of predefined dark or black final shade, and the precious metal-based particles are at least gold-based particles without plasmonic effect.

14. Watch or jewelry component according to any one of claims 2 to 12, characterized in that the matrix is ​​made from a thermosetting resin optionally of dark or black final color, and the precious metal-based particles are at least gold-based nanoparticles of predefined dark or black final color by plasmonic effect.

15. Watchmaking or jewelry component according to any one of the preceding claims, characterized in that the material comprises between 0% and 10% by weight relative to the total weight of the material, including terminals, of at least one additional component.

16. Watchmaking or jewelry component according to claim 15, characterized in that the additional component is a ceramic in the form of nano- or microparticles, preferably in the form of nanoparticles.

17. A watch or jewelry component according to any one of the preceding claims, characterized in that it consists of a watch casing element, a piece of jewelry.

18. A method for manufacturing a watch or jewelry component according to any one of claims 1 to 17, characterized in that it comprises the following steps: a) providing a material for forming the matrix selected from the group comprising at least one thermoplastic resin, one thermosetting resin, and one elastomer; b) providing at least some initial precious metal-based particles; at least one of the matrix and the precious metal-based particles being configured to exhibit a final hue predefined by its coordinates a*, b*, and L* in the CIE L*a*b* space and such that the color difference AE* in the CIE L*a*b* color space between the predefined final hue of said at least one of the matrix and the precious metal-based particles and the hue of said pure native precious metal is greater than 15, preferably greater than 20, preferably greater than 50, more preferably greater than 100;c) optionally provide at least one additional component intended to constitute between 0% and 10% by weight of the material, inclusive; d) combine the material intended to form the matrix with the initial precious metal-based particles and optionally with said at least one additional component in order to obtain a homogeneous mixture of precious metal-based particles and optionally said at least one additional component in the matrix; (e) to produce, by molding, from the mixture obtained in step (d), the watch or jewelry component, in whole or in part, from a material comprising between 37.5% and 95% by weight of the precious metal, inclusive, relative to the total weight of the material, and in which the precious metal-based particles have dimensions such that the maximum dimension of said precious metal-based particles in the plane of the observed surface of the material is less than 100 pm, preferably less than 60 pm, preferably less than 50 pm, preferably less than 30 pm, and the minimum dimension of said precious metal-based particles in the plane of the observed surface of the material is greater than 1 nm, preferably greater than 5 nm, preferably greater than 10 nm, preferably greater than 100 nm, preferably greater than 200 nm, preferably greater than 0.5 pm, and more preferably greater than 1 pm,and the quantity of precious metal particles dispersed in the matrix being predetermined such that said material appears to have the same or a similar hue to the predetermined final hue of said at least one of the matrix and the precious metal-based particles to the same observer placed at least 30 cm, and preferably at least 10 cm, from the surface of said material under the same illumination conditions by an illuminant, said hue of the material being such that the AE* color difference in the CIE L*a*b* color space between the hue of the material and the predetermined final hue of said at least one of the matrix and the precious metal-based particles is less than 10, preferably less than or equal to 5, preferably less than or equal to 4, more preferably less than or equal to 3, more preferably less than or equal to 2, and more preferably less than or equal to 1,and such that the AE* color difference in the CIE L*a*b* color space between the hue of the material and the hue of the pure native precious metal is greater than 15, preferably greater, at 20, preferably greater than 50, more preferably greater than 100.

19. A method for manufacturing a watch or jewelry component according to claim 18, characterized in that the predefined final shade of said at least one of the matrix and precious metal-based particles is dark or black and is defined by its coordinates a*, b*, and L* in CIE L*a*b* space such that -10 <a*< 10, -10 <b*< 10 et 0 <L*< 50, de préférence -5 <a*< 5, -5 <b*< 5 et 0 <L*< 30, et plus préférentiellement -5 <a*< 5, -5 <b*< 5 et L*< 15.

20. A method for manufacturing a watch or jewelry component according to one of claims 18 and 19, characterized in that the quantity of precious metal-based particles is predetermined by prior tests using a colorimeter in order to establish a correlation between the particle size of the precious metal-based particles, the desired color of the material and the volume ratio between the precious metal-based particles and the matrix.

21. A method for manufacturing a watch or jewelry component according to any one of claims 18 to 20, characterized in that said at least one of the matrix and the precious metal-based particles configured to exhibit the predefined final shade is the matrix, said matrix comprising a coloring agent chosen to give the matrix said predefined final shade, and in that the precious metal-based particles are plasmonic-free and of such a shade that the AE* color difference in the CIE L*a*b* color space between the shade of the matrix and the shade of the precious metal-based particles in the matrix is ​​greater than 15, preferably greater than 20, preferably greater than 50, more preferably greater than 100.

22. A method for manufacturing a watch or jewelry component according to any one of claims 18 to 21, characterized in that at least one of the matrix and precious metal-based particles configured to exhibit the predefined final color is constituted by the precious metal-based particles, said precious metal-based particles being nanoparticles having dimensions and shapes that give them an effect plasmonic corresponding to the final predefined tint at least in the visible range.

23. A method for manufacturing a watch or jewelry component according to any one of claims 18 to 22, characterized in that the material intended to form the matrix supplied in step a) is a thermosetting resin selected from the group comprising epoxy resins, polyurethane resins, dimethacrylate urethane polymers (IIDMA), and crosslinked in step e) by a hardener, by the addition of heat or by photopolymerization.

24. Method of manufacturing a watch or jewelry component according to any one of claims 18 to 23, characterized in that step e) comprises a mechanical machining and / or finishing treatment to obtain said watch or jewelry component.

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