Ceramic parts manufacturing

Abstract

1. A method for producing a zirconia-based part of a watch or jewelry part, comprising the steps of: (E1) shaping and sintering a zirconia-based part to obtain a zirconia-based part in a finished or semi-finished shape; then (E2) depositing on at least a part of the surface of the zirconia-based part a layer comprising a material that acts as a getter and that exhibits a higher affinity for oxygen than the zirconium of the zirconia-based part; (E3) heating the zirconia-based part under vacuum or in a neutral atmosphere to obtain a darkening of at least a part of the zirconia-based part, even a black or gray coloration; and (E4) removing the layer comprising the material that acts as a getter.

Description

[Technical Field]

[0001] The present invention relates to a watch or jewelry part comprising at least a part based on a sintered technical ceramic based on zirconia (ZrO2). The invention also relates to a watch comprising such a watch part. Finally, the invention relates to a method for manufacturing a watch or jewelry part made of a sintered technical ceramic based on zirconia (ZrO2) and a method for manufacturing such a watch part. [Background technology]

[0002] In the watch industry, as in jewelry, it is known to use components made of technical ceramics, also referred to simply as ceramics. The adjective "technical" refers to the high-performance properties of the selected ceramic. This is because technical ceramics can achieve very good mechanical, thermal, and even electrical and / or biochemical properties, as well as chemical inertia and non-magnetic properties, making them suitable for use in forming watch components, particularly watch movement components, but also external components for small watches. The technical ceramics used in this case are distinguished from conventional ceramics by their composition, since they are obtained from purified synthetic powders rather than from natural mineral powders, such as feldspar or kaolin.

[0003] Among technical ceramics, ceramics based on zirconia are commonly used due to their good mechanical properties. Apart from these mechanical properties, zirconia-based ceramics are naturally white, so it would be advantageous to provide a method for producing colored zirconia-based ceramics, especially for aesthetic reasons, since applications in watches and jewelry are demanding in terms of aesthetic appearance, especially color. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Swiss Patent Application Publication No. 707424 [Non-patent literature]

[0005] [Non-Patent Document 1] "Technical Report of Colorimetry", CIE 15, 2004 Summary of the Invention [Problem to be solved by the invention]

[0006] The primary objective of the present invention is to provide a zirconia-based technical ceramic solution that allows for achieving high performance whilst also making it possible to achieve desired colours that are considered attractive.

[0007] A second object of the present invention is to provide a zirconia-based technical ceramic solution that can be manufactured in a simple manner.

[0008] The invention more generally relates to components including parts made of technical ceramics, which may be based on zirconia or alumina, for example. [Means for solving the problem]

[0009] The present invention therefore provides a method for producing a zirconia-based part of a watch or jewellery part, comprising the steps of: shaping and sintering the zirconia-based part to obtain the zirconia-based part in finished or semi-finished form, thereafter depositing a layer over at least a portion of the surface of the zirconia-based portion, the layer including a material exhibiting gettering properties, the material exhibiting a higher affinity for the oxygen than the zirconium of the zirconia-based portion; heating the zirconia-based portion under vacuum or in a neutral atmosphere to darken at least a portion of the zirconia-based portion, and even to obtain a black or gray coloration; removing the layer containing the material exhibiting gettering properties; Including stages, Based on a method for manufacturing zirconia-based parts of watch or jewelry components. The darkening or coloring is visible from the surface of the part.

[0010] The invention is more particularly defined by the claims.

[0011] The objects, features and advantages of the present invention will be explained in detail in the following description of specific embodiments, given without limitation with reference to the accompanying drawings. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 shows a schematic logic diagram of a method for manufacturing a zirconia portion of a watch or jewelry piece according to one embodiment of the present invention. [Figure 2] 2a to 2c show diagrammatically steps in a manufacturing method for an example of coloring a bezel disc according to an embodiment of the present invention. [Figure 3] 3a to 3d show diagrammatically steps in a manufacturing method for an example of disc coloring according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] In the following, "high density" ceramic is understood to mean a ceramic whose density is between 95% and 100% of the theoretical density of the material under consideration. In this specification, the term "ceramic" or "technical ceramic" means a high density material based on stabilized zirconium oxide. The term "part made of zirconia-based ceramic", or even simply "zirconia-based part", is used to mean a part made of sintered zirconia-based technical ceramic that forms all or part of a watch or jewelry part.

[0014] Additionally, the terms "zirconia-based" or "zirconia-based" are understood in all cases to mean a material that primarily comprises zirconia, in a proportion of at least 50% by weight, or even at least 75% by weight, or even at least 90% by weight. Thus, the ceramic material used in the present invention comprises at least 50% by weight of zirconia. The zirconia-based material may also contain other compounds, in whole or in part, in particular, without limitation, compounds selected from yttrium oxide, cerium oxide, magnesium oxide, calcium oxide, scandium oxide, lanthanum oxide, niobium oxide, ytterbium oxide, neodymium oxide, terbium oxide, or erbium oxide.

[0015] The term "finished form" of a part or part of a part is understood to mean a part or part of a part whose shape, dimensions and surface finish are completed. The term "semi-finished form" is understood to mean a part or part of a part whose shape and dimensions are close to the final form, but whose surface finish may differ from that obtained at the end of the manufacturing process.

[0016] The watch or jewelry part comprises at least a zirconia-based part, i.e. a part made of sintered technical ceramic based on zirconia ZrO2. Such a part may correspond to all or part of the watch or jewelry part. A method for manufacturing such a part of a watch or jewelry part according to one embodiment of the present invention comprises the steps shown diagrammatically in the logic diagram of Figure 1. Optional steps are indicated by dotted lines. The method allows in particular to manufacture parts made of zirconia-based ceramic that are at least locally black or dark in color, which are considered very attractive by watch and jewelry aestheticians. The method for manufacturing a zirconia-based part according to the present invention comprises the following steps: - E1 shaping and sintering said zirconia-based part to obtain said zirconia-based part in finished or semi-finished form, then - E2 depositing a layer comprising a material exhibiting gettering properties over at least a portion of the surface of said zirconia-based portion; E3 heating the zirconia-based part under vacuum or in a neutral atmosphere in order to obtain a darkening, even a black or gray coloration, at least locally, i.e. over at least a portion, of the zirconia-based part, and then E4, removing the layer containing the material exhibiting gettering properties.

[0017] More specifically, the production method includes a method for coloring the zirconia-based moiety formed in steps E2 to E4.

[0018] The first stage is carried out starting from a zirconia-based technical ceramic. This stage involves the preparation of a ceramic powder with a binder, which is then shaped and sintered in a known manner to obtain the zirconia-based technical ceramic part. The technical ceramic may be based on yttria-stabilized zirconia, optionally dyed. The zirconia-based part obtained in this first stage is therefore a high-density technical ceramic, the density of which is between 95% and 100% of the theoretical density of the technical ceramic. According to one embodiment, the sintered technical ceramic contains zirconia (ZrO) in a weight percentage of 80% or more, even 85% or more, or even 90% or more. According to one embodiment, the sintered technical ceramic contains zirconia (ZrO) in a weight percentage of 94% or less, even 93% or less.

[0019] More specifically, the invention may be advantageously applied to yttria-stabilized zirconia stabilized with 3 mol% Y2O3, with or without added cerium oxide. Alternatively, zirconia stabilized with 2 mol% Y2O3, or even with 1.8 mol% Y2O3, or even with 1.6 mol% Y2O3 may be used.

[0020] As a further alternative, the present invention may advantageously be applied to yttria-stabilized and dyed zirconia that initially has a color other than black, for example, green or blue. For example, the zirconia may advantageously contain a pigment prepared starting from spinel, in particular cobalt aluminate. Also by way of example, the zirconia may contain a pigment prepared starting from nickel oxide, iron oxide, cobalt aluminate, alumina, or mixtures thereof. Alternatively, other methods of coloring ceramics may be used, such as elements in solid solution. Regardless of the method by which the ceramic is colored, its initial color (at the completion of the E1 stage) is distinct from its final color (the color obtained at the completion of the E4 stage, which is at least partially modified from the initial color, as explained below).

[0021] For the second stage of layer deposition, a material is selected that exhibits oxygen pumping properties, i.e., in this context, a material that exhibits a higher affinity for oxygen than the zirconia of the zirconia-based ceramic, especially at the temperatures of the heat treatments described below. This is understood to mean that the oxygen present in the zirconium oxide tends to diffuse towards the material during the applied heat treatment, rather than remaining in the zirconium oxide. For simplicity's sake, the term "material exhibiting gettering properties" refers to such a material, since this specification uses a principle similar to that of a non-evaporable oxygen pump (NEG or "non-evaporable getter"), whose surface adsorbs oxygen, in particular from the vacuum chamber, until it is completely oxidized.

[0022] The thickness of the deposited layer can be selected within a wide range. Preferably, the thickness is as thin as possible, with the lower limit of the layer thickness being determined by the capacity of the material of which the layer is composed to store a sufficient amount of oxygen extracted from the ceramic. This sufficient amount is determined, in particular, by the effect on the final color of the zirconia-based ceramic surface and the depth to which the ceramic is darkened relative to its initial color due to oxygen extraction. The thicker the layer of material containing gettering properties, the darker the resulting color of the ceramic will be, even reaching black, and / or the darkened color will extend further through a significant depth of the associated ceramic. The maximum thickness of the layer of material exhibiting gettering properties is additionally determined by the requirement for good adhesion of the layer to the ceramic. This is because too thick a layer may encounter adhesion problems, which may be detrimental to the coloring effect in areas of weak adhesion and may cause non-uniform coloring, which is undesirable for aesthetic reasons. In addition, the effectiveness of the gettering properties of the material also depends on its specific structure; for example, a nanocrystalline morphology increases its storage capacity compared to a crystalline morphology.

[0023] A person skilled in the art can therefore define, on a case-by-case basis, the appropriate parameters of the layer exhibiting getter properties as a function of the desired result. In general, and without limitation, the thickness of the layer may be between 50 nm and 6 μm.

[0024] Furthermore, the material exhibiting gettering properties may be titanium, or a titanium alloy, or hafnium, or a hafnium alloy, or zirconium, or a zirconium alloy, or a combination of these materials, or other more complex materials that include at least one of these materials.

[0025] In addition, the step E2 consisting of depositing a layer comprising a material exhibiting getter properties is advantageously carried out by physical vapor deposition (PVD), or by chemical vapor deposition (CVD), or by atomic layer deposition (ALD), or by pulsed laser deposition (PLD), or by any other suitable method.

[0026] The material exhibiting getter properties may be deposited over the entire surface of the part. In an advantageous alternative, the material may be deposited over only a portion of the surface. In this alternative, a mask may be used to mask the surface portions on which the layer is not to be deposited. This may be, for example, a matter of masking with a photosensitive resin (in which case a layer of resin is deposited over the surface portion to be masked) or "mechanical" masking (in which case a free-standing object serving as the mask is pressed against or even placed directly above the surface portion to be masked). Thus, in this alternative, the method includes an intermediate step consisting of masking E15 at least a portion of the surface of the zirconia-based part in finished or semi-finished form in order to deposit E2 a layer of getter material in a localized manner. In this alternative, the method also includes another intermediate step consisting of removing E25 the mask after depositing E2 the getter layer and before heat treatment E3 of the part. In the case of a mask compatible with the heat treatment step E3, the mask may be removed after said step E3 (for example for a mechanical mask) or during the removal step E4 (for example for a plastic mask). In an alternative, it is possible to foresee any method that makes it possible to perform the deposition of getter material in a localized manner over part of the surface of the part, even if no masking needs to be performed.

[0027] The method then carries out a step E3 consisting of heating the zirconia-based part, in which the gettering properties of the deposited material layer are exerted by absorbing at least a portion of the oxygen contained in the ceramic, and for this purpose the zirconia-based part can be heated to a temperature between 900°C and 1300°C, or even between 1000°C and 1150°C.

[0028] The heating is 10 -2 mbar and 10 -10The heating may be carried out at a pressure between 1000 and 10000 mbar, under vacuum, or at atmospheric pressure, in a neutral atmosphere based on argon, xenon, or krypton, or a mixture of these gases. Any heating conditions that minimize the presence of oxygen in the chamber, excluding the ceramic, may be advantageous and may be implemented. It may also be desirable to minimize the presence of carbon, nitrogen, and / or any element that can react with zirconia during the process.

[0029] The diffusion of oxygen from the zirconia into the getter layer appears to affect the associated zirconia-based part, which becomes at least partially substoichiometric in oxygen (i.e., oxygen-depleted compared to the initial situation of stoichiometric equilibrium). This change leads to, at least locally, a black or dark gray coloration of the zirconia-based part, or more generally, at least locally, a darkening of the zirconia-based part. This change occurs at the surface, in a region within the volume of the part starting from the surface. Since this change is noticeable at the surface of the part, it is used particularly for decorative purposes. For this reason, the coloring method preferentially allows for the production of black coloration of ceramics. In an alternative form, the method allows for the production of gray coloration. These black and gray colors are particularly obtained starting from a substantially white semi-finished or finished part (produced by the first step of the method).

[0030] Alternatively, many other colors are possible. This is because, conventionally, a zirconia-based portion may exhibit any initial color if it contains a coloring pigment. Incidentally, the initial color may alternatively be obtained by any method other than dyeing. Ceramics having an initial color are hereinafter referred to as "dyed zirconia" or "colored zirconia." The method then allows for the initial color to be darkened. Thus, the method has the overall effect of darkening the treated zirconia-based portion. The darkening obtained by the method according to the present invention is due to the fact that the zirconia is made substoichiometric in oxygen and / or the pigment is modified. The zirconia-based portion obtained by the method according to the present invention is described as a portion "based on substoichiometric zirconia with a darkened appearance." The coloring according to the present invention is performed in a "subtractive" manner, in the sense that the initial chemical composition of the zirconia-based portion is depleted of oxygen and no element is enriched (e.g., carbon does not contribute to the coloring). The darkening is therefore understood in comparison with the color that would be obtained without the implementation of the invention (i.e. the initial color upon completion of the molding and sintering step E1). The coloring method according to the invention thus makes it possible to darken ceramics, or to obtain black or gray colors. Preferentially, the coloring method according to the invention is used to obtain black coloring of dyed zirconia.

[0031] The duration of the treatment is highly variable and depends on the desired result. The heat treatment may be between 10 minutes and 10 hours. Likewise, the temperature of the treatment is highly variable and depends on the desired result.

[0032] Incidentally, some alternative embodiments have different advantages. This is because certain alternative embodiments of the present invention make it possible to obtain selective coloring, i.e., coloring that is applied only to a portion of the surface of a zirconia-based part. This is especially true in alternatives in which the layer containing the material exhibiting gettering properties is not applied over the entire surface of the part. For example, the coloring according to the present invention is selective when applied to zirconia colored with a pigment, such as a green or blue pigment, obtained from spinal, in particular from cobalt aluminate, or from a mixture of oxides (the mixture containing, for example, cobalt aluminate and other oxides), and when the layer containing the material exhibiting gettering properties is not applied over the entire surface of the part. In this case, only the portion of the surface of the part that is vertically aligned with the locally deposited getter layer is colored according to the principles of the present invention. On the other hand, in other alternative embodiments, the coloring according to the present invention is observed over the entire surface of the part, even if the entire surface is not covered with a layer made of a material exhibiting gettering properties. This is the case, for example, under the conditions tested in accordance with the fourth example described below, when starting from a section made of zirconia colored brown with a pigment based on iron oxide Fe2O3, for example, and a section made of white yttria-stabilized zirconia containing alumina Al2O3. In other words, the at least partial application of a layer containing a material exhibiting gettering properties makes it possible in all cases to obtain a certain volumetric coloration of the zirconia-based section, which may correspond exactly to the surface section where the material exhibiting gettering properties is found, i.e., vertically aligned over a certain depth of the surface section, or alternatively, may not correspond exactly to the surface section but may be more extensive. This is due to the dynamics of the oxygen diffusion phenomenon. Preferentially, the coloration method according to the invention is used to obtain a selective coloration of zirconia. More specifically, the method is used to obtain a black coloration that is preferentially visible over the surface section vertically aligned with the locally deposited getter layer, while the initial color of the dyed zirconia is maintained over the remainder of the surface.

[0033] The color of technical ceramics is measured spectrophotometrically. Measurements are performed in reflection through a 7 mm aperture with a 4 mm measuring diameter. The geometry of the measuring device corresponds to diffuse illumination and spectral measurement at 8°. If the part does not exhibit a sufficiently flat surface, a reference disk is used to perform the measurement. Reflectance measurements are performed between 360 nm and 740 nm, and color evaluation is performed assuming an observer angle of 10° and illuminant D65. As shown in [Non-Patent Document 1], lightness L*, color values ​​a*, b*, chroma C*, and hue angle h* are evaluated in the CIE L*a*b* space defined by the International Commission on Illumination. Measurements are performed in SCI (specular reflection included) and SCE (specular reflection excluded) modes. Additionally, spectrophotometric measurements are preferably performed on parts with a polished surface finish, exhibiting a roughness defined by the standard roughness parameter Ra, preferably with a value of 2 nm ± 0.2 nm. Incidentally, the parameter Ra is measured according to ISO standard 4287.

[0034] Thus, more particularly, according to the standard approach described above, the invention makes it possible to produce two-tone, and even polychromatic, ceramic watch parts which may include at least dark, and in particular black, areas defined by the following colorimetric parameters in SCI mode: L* below 47.0, or even below 45.6, or even below 45.4; or L* between 43.0 and 47.0, or even between 44.3 and 45.6, or even between 45.0 and 45.4; a* between −0.1 and 1, or even between −0.5 and 1.0, or even between 0.3 and 0.9; b* between −1 and 1.6, or even between −0.8 and 1.4, or even between 0.3 and 1.1; and L* between 5.0 and 12.0, a* between 1.4 and 5.7, b* between 5.5 and 10.8 in SCE mode; and the other parts have their own initial color unchanged.

[0035] Incidentally, the step consisting of depositing a layer containing a material exhibiting gettering properties on the one hand and the step consisting of heating the zirconia-based part on the other hand can advantageously be carried out in two different chambers or in the same chamber, and if the method includes an intermediate masking step as described above, the possibility of carrying them out in the same chamber remains, provided that the masking is properly handled.

[0036] In this case, the following steps may also be performed in the same chamber. - E2 depositing a layer comprising a material exhibiting gettering properties over at least a portion of the surface of said zirconia-based portion; - optionally E25 with mechanical masking removal (as in some cases the masking may be removed at a later stage); E3 heating the zirconia-based portion under vacuum or in a neutral atmosphere in order to obtain a darkening, even a black or gray coloration, over at least a portion of said zirconia-based portion.

[0037] The step E4 consisting of removing the layer containing the material exhibiting getter properties is carried out by chemical cleaning, in particular by chemical dissolution, or by mechanical cleaning, in particular by grinding, sandblasting, machining or brushing steps, of the surface of the part in question, possibly accompanied by laser treatment.

[0038] According to one embodiment, the preceding step E4 consisting of removing the layer containing the material exhibiting gettering properties makes it possible at the same time to proceed to finishing the surface of the component part. In an alternative, the method may also include any separate final finishing step, for example finishing and / or polishing and / or sandblasting and / or satin finishing.

[0039] As follows from the above explanation, the zirconia-based part does not necessarily contain a material with getter properties in its volume. For this reason, the present invention does not apply to incorporating a getter material in its volume, for example during the formation of the ceramic powder. The getter material is necessarily used in the form of a sacrificial layer that is added to the surface of the part. However, according to an alternative embodiment, such a material may also be incorporated into the body in the area of ​​the part for staining purposes, in order to achieve a complementary coloring other than the blackening aimed at by the present invention.

[0040] The manufacturing method thus includes a phase of coloring, in particular to black, of the part made of zirconia-based ceramic, which additionally exhibits the following advantages: - there is no need to incorporate color pigments into the powder, as is customary in the state of the art, and even no need to add additional elements to the ceramic, for example no impregnation with additional elements, as is customary in the state of the art, since the coloring according to the invention is obtained directly from the physical phenomenon of modification of the ceramic itself by oxygen extraction. The result is a non-destructive one-piece ceramic part, in particular the colouring according to the invention is not obtained by a layer of colouring added to the surface, which would risk delamination. The coloring step according to the invention is carried out at the end of the manufacturing process on an already sintered semi-finished or finished product. The step can be applied in different ways to the same semi-finished or finished part to obtain a monochromatic or locally (selectively) colored result. The step does not require any upstream adaptation of the manufacturing process. The coloring step does not require intervention with respect to the initial powder used to manufacture the watch part, and does not require specific powder recipes for each desired color, making it a simple method. - The coloring step according to the invention is, in addition, reversible. Therefore, in the event of an unsatisfactory result, it is possible to return to the high heat treatment (which requires reaching several hundred degrees in an oxidizing atmosphere, and is therefore not something that a small watch wearer would encounter in their daily life) to restore the initial stoichiometric form and possibly carry out another coloring phase with modified parameters. In state-of-the-art coloring solutions, the coloring is irreversible. In the event of an unsatisfactory result, the part is lost and must be scrapped, which is a major disadvantage.

[0041] The present invention also relates to a watch or jewelry part obtained by the manufacturing method described above. For this reason, the present invention relates to a watch or jewelry part comprising at least a zirconia-based portion, with at least a portion of the surface of the zirconia-based portion being substoichiometric with respect to oxygen, exhibiting a dark, even black or grey, appearance.

[0042] Thus, the ceramic exhibits an oxygen-depleted zone, with the zirconia aligned perpendicular to the surface of the zirconia-based part having the modified color according to the invention. This zone is formed to a depth below the surface. This depth can be selected within a wide range, defined in part by a layer of material exhibiting gettering properties applied during the manufacturing process. Generally, this zone is selected to be deep enough to ensure that the color remains unchanged during use of the part, i.e., to prevent the initial color of the zirconia (present beneath the colored zone according to the invention) from appearing, for example, due to frictional wear of the part or in the event of surface scratches. However, the depth is advantageously selected to be relatively thin, to avoid complicating the manufacturing process. For example, the depth is selected to be at least 0.015 mm, and preferably between 0.015 mm and 1 mm. Alternatively, the color according to the invention is formed throughout the entire thickness of the part.

[0043] According to an alternative embodiment, the watch or jewelry piece may comprise a pigmented (or otherwise colored) body portion having a first area that is given a first color (an initial color not altered by the present invention) and a second area that exhibits a darkening, even a black or gray appearance, as a result of the sub-stoichiometric oxygen induced by the present invention in the area, a second, different color (the above-mentioned final color induced by the present invention).

[0044] The zirconia-based portion of the watch or jewelry piece may be a high density technical ceramic, the density of which is between 95% and 100% of the theoretical density of the technical ceramic.

[0045] The darkening, for example obtaining a black, grey or more generally dark colour according to the invention, may concern only a portion of the surface of the part made of sintered technical ceramic based on zirconia ZrO2 of the watch or jewellery part ("selective" colouring) or it may extend over the entire surface of the part.

[0046] The zirconia-based portion may be based on yttria-stabilized zirconia, optionally dyed with a pigment comprising, in particular, an aluminate, especially cobalt aluminate.

[0047] Preferentially, obtaining the black color according to the invention concerns only a portion of the surface of the part of the watch or jewelry piece made of sintered technical ceramic based on dyed zirconia ZrO2 ("selective" coloring), while the rest of the surface maintains its initial color. In this advantageous alternative, the method makes it possible to obtain a two-color part, comprising a first part, treated according to the invention and black, and a second, untreated part, white or of another color, in particular starting from conventional pigments, that maintains its initial color.

[0048] For this reason, the present invention also relates to a method for producing a zirconia-based part of an at least two-tone watch or jewellery part, comprising the following steps: - E1 shaping and sintering the optionally colored, in particular dyed, zirconia-based part to obtain said zirconia-based part in finished or semi-finished form and of initial color, then depositing E2 a layer comprising a material exhibiting gettering properties over only a first portion of the surface of said zirconia-based portion, the second portion being left uncoated; E3, heating the zirconia-based portion under vacuum or in a neutral atmosphere to darken the zirconia-based portion in the first portion, and even to obtain a black or gray coloration, while the second portion maintains its initial color, and then E4, removing the layer containing the material exhibiting gettering properties.

[0049] In this way, the second portion maintains its initial color, and more generally remains unchanged in the step consisting of heating the zirconia-based portion.

[0050] A timepiece part may be any external element of a small timepiece, such as a bezel, bezel disc, case, back, body, dial, decorative plate or bracelet link, etc. Alternatively, a timepiece part may be a part of a timepiece movement.

[0051] The invention also relates to a timepiece, in particular a wristwatch, including at least one timepiece component as described above.

[0052] The watch component may be a single piece or may comprise an assembled combination of different parts, thus the watch component may be of a single chemistry or a combination of chemistries, thus the watch component may comprise one material or several different materials, necessarily including at least a portion made of zirconia-based ceramic as described above.

[0053] The parts sought to be treated according to the invention, whether single-color, two-color or multi-color, are preferably made of a single piece, in the form of a one-piece cast, and are of a single color, for example of a color called initial color.

[0054] The parts treated according to the invention are advantageously at least two-colored. For this reason, in the case of parts treated to have two colors, it is advantageous to obtain a first part that is locally black and a second part that is locally the initial color, without a weak boundary or interface between the black part and the initial color part, as would be the case if the two colors were obtained by elements that were at least partially produced separately and then assembled.

[0055] In addition, the coloring according to the invention makes it possible to obtain a coloring not only superficially but throughout a considerable depth of the part, so that even in the event of wear on the surface, the color of the part is not affected.

[0056] The production of technical ceramics will now be described in accordance with an embodiment of the present invention.

[0057] The first example consists of a frustoconical bezel disc made of blue tetragonal zirconia (zirconia stabilized with 3 mole % Y2O2, designated "3Y ZrO2"). The blue color is a body coloration obtained by adding a pigment (spinel CoAl2O4). Mechanical masking of half of the disc is carried out. The disc is then placed in a PVD deposition chamber where a 5 μm thick titanium deposit is formed on its top surface, forming a layer made of a material that exhibits gettering properties. The mechanical masking is removed. The disc thus half coated is then subjected to 10 -5 The bezel disc is then placed in a vacuum furnace where it is subjected to a heat treatment at a pressure of 1000 mbar and a temperature hold of 1035°C for 30 minutes. The getter layer is then removed (by simple brushing) and the disc is polished on its top surface. The half disc that was covered by the getter layer now has a black appearance. Incidentally, the finished bezel disc does not exhibit a metallic appearance in the black-coloured parts according to the invention. The rest of the disc remains blue. Figures 2a to 2c show diagrammatic views of the top surface of the bezel disc 1 at various stages of the colouring method according to the embodiment of the invention described above. FIG. 2a shows diagrammatically the blue monochromatic one-piece bezel disc 1 at the completion of the step consisting of molding and sintering E1. FIG. 2b shows diagrammatically the disk 1, the first half 3 of which is coated with a titanium layer and the second half 2 of which is uncoated, at the completion of the step E2 consisting of depositing a titanium layer. FIG. 2c shows diagrammatically the disc 1, after the step consisting of heating E3, and upon completion of the step consisting of removing the titanium layer E4, in which the first half 3 is black and the second half 2 remains blue.

[0058] The second example embodiment concerns a disk made of blue tetragonal zirconia (3Y ZrO2) with a diameter of 3 cm and a thickness of 5 mm. The blue color is obtained by adding a pigment (spinel CoAl2O4) or by impregnation with cobalt and aluminum salts according to the teachings of US Pat. No. 5,649,499. The upper surface is polished (this promotes good resolution of the settings). The disk then undergoes partial masking of its upper surface, carried out with a photosensitive resin, so that the visible portions of the blue zirconia are only present in selected locations, for example corresponding to a selected design, such as a butterfly shape. The disk is placed in a PVD deposition chamber, where a 5 μm thick titanium deposit is formed on its upper surface, forming a layer made of a material exhibiting gettering properties. The masking photosensitive resin is dissolved. The locally titanium-coated disk is then subjected to 10 -5 The disk is placed in a vacuum furnace where it is subjected to a heat treatment with a pressure of 1000 mbar and a temperature hold of 1035°C for 30 minutes. Finally, the disk is immersed in a suitable chemical solution that makes it possible to remove the titanium coating. Alternatively, the disk can be subjected to polishing to remove the getter coating. The result obtained is a disk showing a setting consisting of a black butterfly on a blue background, the assembly having a polished surface finish. Figures 3a to 3c show diagrams of the top surface of the disk 4 during the steps of the coloring method according to the invention. FIG. 3a shows diagrammatically the blue monochromatic one-piece bezel disc 4 at the completion of the step consisting of molding and sintering E1. FIG. 3b shows diagrammatically the disc 4, at the completion of the intermediate masking step E15, with the surface of the first part 6 coated with masking resin and the second part 5 uncoated. Figure 3c shows diagrammatically the disk 4, at the completion of the step E2 consisting of depositing a titanium layer and the step E25 consisting of removing the mask, with the surface of the second portion 5 covered with a titanium layer and the surface of the first portion 6 uncovered. FIG. 3d shows diagrammatically the disk 4, after the step consisting of heating E3, and upon completion of the step consisting of removing the titanium layer E4, in which the surface of the first portion 6 remains blue while the surface of the second portion 5 is black.

[0059] The third example is a bezel disc made of green tetragonal zirconia (3Y ZrO2). This green color is the color of the body obtained by adding a pigment formed from a combination of oxides. Its upper surface is polished. The bezel disc is subjected to partial masking of the upper surface, carried out with a photosensitive resin, so that the visible part of the green zirconia corresponds to half of its surface. The bezel disc is placed in a PVD deposition chamber, where a 5 μm thick titanium deposit is formed on its upper surface, forming a layer made of a material that exhibits gettering properties. The masking photosensitive resin is dissolved. The bezel disc, locally coated with titanium, is then heated for 10 -5 The bezel disc is then placed in a vacuum furnace, where it is subjected to a heat treatment at a pressure of 1000 mbar and a temperature hold of 1035°C for 30 minutes. The bezel disc is then subjected to a partial machining process that obtains a satin surface finish, which allows both to remove the coating made of a material that exhibits gettering properties and to proceed to finish the surface of that part of the bezel disc. The result is a bezel disc with half of its top surface satin-finished black and the other half polished green. Alternatively, machining may be performed over the entire surface of the disc to obtain a totally satin-finished, half green, half black disc.

[0060] The fourth example concerns a disk made of white zirconia (containing Al2O3) with a diameter of 3 cm and a thickness of 5 mm. Its upper surface is polished. The disk is placed in a PVD deposition chamber where a 3 μm thick titanium deposit is formed on its upper surface, forming a getter layer. The titanium-coated disk is then heated for 10 min. -4 The disk is placed in a vacuum furnace where it is subjected to a heat treatment with a pressure of 1000 mbar and a temperature hold of 1035 °C for 10 minutes. Finally, the disk is immersed in a suitable chemical solution that makes it possible to remove the getter coating (alternatively, the disk is subjected to polishing). The result obtained is a dark gray disk.

[0061] Incidentally, in all of these examples, the same material exhibiting gettering properties, titanium, was used in order to compare the examples with one another. Of course, the invention is not limited to titanium, and as already mentioned above, other materials exhibiting gettering properties may be used in the alternative. Similarly, the other parameters selected in these examples are provided without limitation. It will become apparent throughout this specification that these parameters may be varied without departing from the scope of the invention.

[0062] The invention also relates to a method for manufacturing a watch component comprising at least a part based on a zirconia-based sintered technical ceramic, the ceramic being bichromatic, or even polychromatic, and comprising at least a first treated surface portion exhibiting a dark color, in particular black, defined by colorimetric parameters in SCI mode: L* lower than 47.0, or even lower than 45.6, or even lower than 45.4, a* between -0.1 and 1, or even between -0.5 and 1.0, or even between 0.3 and 0.9, b* between -1 and 1.6, or even between -0.8 and 1.4, or even between 0.3 and 1.1, and wherein the spectrophotometric measurements are carried out on a part with a polished surface finish. The part may additionally comprise at least a second untreated surface portion of unchanged initial color.

[0063] The invention also relates to a ceramic watch part, which is based on zirconia and is a continuous, two-tone, or even multi-tone, one-piece part, comprising at least a first portion of a first color and a second portion of a second color different from the first color, in particular a first blue or green and a second black color.

[0064] The invention also relates to a ceramic watch part obtained from the manufacturing method, comprising a black first portion defined by colorimetric parameters in SCI mode: L* lower than 47.0, even lower than 45.6, even lower than 45.4, a* between -0.5 and 1, even between -0.1 and 1.0, even between 0.3 and 0.9, b* between -1 and 1.6, even between -0.8 and 1.4, even between 0.3 and 1.1, wherein the spectrophotometric measurements are performed on a part with a polished surface finish. The part may comprise a second untreated surface portion of unchanged initial color.

[0065] In accordance with the present invention, technical ceramics other than zirconia-based ceramics have also been tested, and it has been found that the present invention works equally well with other technical ceramics, particularly alumina-based ceramics. Thus, all of the above-described embodiments can be implemented with an alumina-based portion instead of a zirconia-based portion.

[0066] For this reason, the invention also relates to a method for producing a part based on technical ceramic, in particular on alumina, of a watch or jewellery part, comprising: - E1, forming and sintering a part based on technical ceramics to obtain a part based on technical ceramics in finished or semi-finished form, - depositing E2, over at least a portion of the surface of the technical ceramic-based part, a layer comprising a material exhibiting gettering properties, which material exhibits a higher affinity for oxygen than the technical ceramic of the technical ceramic-based part; E3, heating the technical ceramic-based part under vacuum or in a neutral atmosphere in order to darken at least part of the technical ceramic-based part, and even to obtain a black or gray coloration, - E4: Remove the layer containing the material that exhibits gettering properties The present invention relates to a method comprising the steps of:

[0067] The invention also relates to a method for producing an at least two-colored watch or jewelry part based on technical ceramics, in particular based on alumina, comprising the steps of: - E1 shaping and sintering of an optionally colored, in particular dyed, part based on technical ceramic to obtain a part based on technical ceramic in finished or semi-finished form, with an initial color, and then depositing E2 a layer comprising a material exhibiting gettering properties over only a first portion of the surface of the technical ceramic-based part, leaving a second portion of the surface uncoated; E3, heating the technical ceramic-based part under vacuum or in a neutral atmosphere in order to darken the technical ceramic-based part in the first part, and even to obtain a black or gray coloration, while the second part maintains its initial color, and then - E4: Remove the layer containing the material that exhibits gettering properties The present invention relates to a method comprising the steps of:

[0068] The invention also relates to a watch or jewelry part comprising at least a part based on technical ceramic, in particular on alumina, which part is based on technical ceramic with sub-stoichiometric oxygen, exhibiting a dark, even black or grey, appearance.

[0069] The invention also relates to a watch or jewelry part, wherein the part based on technical ceramic is a high-density technical ceramic, the density of which is between 95% and 100% of the theoretical density of the technical ceramic, and / or the part based on technical ceramic is based on an yttria-stabilized technical ceramic, optionally dyed, in particular with a pigment comprising an aluminate, in particular cobalt aluminate.

Claims

1. 1. A method for producing a zirconia-based part of a watch or jewelry part, comprising the steps of: shaping and sintering said zirconia-based part (E1) to obtain said zirconia-based part in finished or semi-finished form, then depositing (E2) a layer containing a material exhibiting gettering properties over at least a portion of the surface of the zirconia-based portion, the material exhibiting a higher affinity for the oxygen than the zirconium of the zirconia-based portion; heating the zirconia-based portion under vacuum or in a neutral atmosphere in order to darken at least a portion of the zirconia-based portion, and even to obtain a black or gray coloration (E3); removing the layer containing the material exhibiting gettering properties (E4); Including stages, Method for manufacturing a zirconia-based part of a watch or jewelry component.

2. 1. A method for producing a zirconia-based part of a watch or jewelry part having at least two colors, comprising: shaping and sintering (E1) said zirconia-based part, optionally dyed, to obtain said zirconia-based part in finished or semi-finished form and of initial color, then depositing (E2) a layer comprising a material exhibiting gettering properties over only the first portion of the surface of the zirconia-based portion, leaving the second portion of the surface uncoated; E3) heating the zirconia-based portion under vacuum or in a neutral atmosphere to darken the zirconia-based portion in the first portion, while the second portion maintains its initial color, and to obtain a black or gray coloration, and then removing the layer containing the material exhibiting gettering properties (E4); Including stages, Method for manufacturing a zirconia-based part of a watch or jewelry component.

3. the second portion of the zirconia-based portion remains unchanged by the step consisting of heating (E3) the zirconia-based portion; 3. A method for producing a zirconia-based portion of a watch or jewelry part according to claim 2.

4. said step consisting of depositing (E2) a layer containing a material exhibiting getter properties, said layer having a thickness between 50 nm and 6 μm; A method for producing a zirconia-based part of a watch or jewellery part according to any one of claims 1 to 3.

5. said step consisting of depositing (E2) a layer containing a material exhibiting gettering properties uses titanium, or a titanium alloy, or hafnium, or a hafnium alloy, or zirconium, or a zirconium alloy, or a combination of these materials as the material exhibiting gettering properties; A method for producing a zirconia-based part of a watch or jewellery part according to any one of claims 1 to 4.

6. said step consisting of depositing (E2) a layer comprising a material exhibiting getter properties is carried out by physical vapor deposition (PVD) or by chemical vapor deposition (CVD) or by atomic layer deposition (ALD) or by pulsed laser deposition (PLD); A method for producing a zirconia-based part of a watch or jewellery part according to any one of claims 1 to 5.

7. the step consisting of depositing (E2) a layer containing a material exhibiting gettering properties, on the one hand, and the step consisting of heating (E3) the zirconia-based part, on the other hand, are carried out in the same chamber or in two separate chambers; A method for producing a zirconia-based part of a watch or jewellery part according to any one of claims 1 to 6.

8. an intermediate step consisting of masking (E15) a part of the surface of the part, the step comprising depositing (E2) a layer comprising a material exhibiting gettering properties being carried out on the part of the part not masked in the intermediate step, A method for producing a zirconia-based part of a watch or jewellery part according to any one of claims 1 to 7.

9. The step of heating the zirconia-based portion (E3) may comprise heating the zirconia-based portion to a temperature between 900°C and 1300°C, or even between 1000°C and 1150°C. A method for producing a zirconia-based part of a watch or jewellery part according to any one of claims 1 to 8.

10. The step consisting of heating the zirconia-based portion (E3) is carried out under vacuum for 10 －２ 10 from mbar －１０ mbar or under a neutral atmosphere based on argon, xenon or krypton, 10. A method for producing a zirconia-based part of a watch or jewellery part according to any one of claims 1 to 9.

11. the step consisting of removing (E4) the layer containing the material exhibiting getter properties is carried out by chemical cleaning, in particular chemical dissolution, or by mechanical cleaning, in particular a polishing, sandblasting, machining or brushing step, of the surface of the part, optionally accompanied by a laser treatment; A method for producing a zirconia-based part of a watch or jewellery part according to any one of claims 1 to 10.

12. 1. A watch or jewelry piece comprising a zirconia-based part, wherein at least a portion of said zirconia-based part is substoichiometric in oxygen, exhibiting a dark, even black or gray, appearance. Watch or jewellery parts.

13. the zirconia-based portion is a high-density technical ceramic, the density being between 95% and 100% of the theoretical density of the technical ceramic, and / or the zirconia-based portion is based on yttria-stabilized zirconia, optionally dyed with a pigment, in particular comprising an aluminate, in particular cobalt aluminate, A watch or jewellery piece according to claim 12.

14. The zirconia-based portion includes a color pigment distributed in a body, the zirconia-based portion including a first region where the body is colored by the color pigment, exhibiting a first color, and a second region corresponding to the zirconia-based portion where the oxygen is substoichiometric, exhibiting a second color different from the first color and exhibiting the dark color, even black or gray appearance. A watch or jewellery part according to claim 12 or 13.

15. An external element of a small watch, such as a bezel, bezel disc, case, back, body, dial, decorative plate or bracelet link, or a part of a watch movement, A timepiece component according to any one of claims 12 to 14.

16. A timepiece, in particular a wristwatch, comprising at least one timepiece component according to any one of claims 12 to 15.

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