Production of ceramic parts

Abstract

The invention relates to a method for producing a zirconia-based part of a timepiece or jewelry part, said method being characterized in that it comprises the following steps: shaping and sintering a zirconia-based part (E1) in order to obtain a zirconia-based part in the form of a finished or semi-finished product; then depositing on at least a portion of the surface of the zirconia-based portion a layer (E2) comprising a material as getter, the material having a greater affinity to oxygen than the zirconium of the zirconia-based portion; heating the zirconia-based portion (E3) in a vacuum or neutral atmosphere to obtain that at least a portion of the zirconia-based portion is darkened, or coloured to black or gray; the layer (E4) containing the material as getter is removed.

Description

Technical Field

[0001] The present invention relates to a timepiece or jewelry component comprising at least a part of a sintered technical ceramic based on zirconium oxide ZrO₂. The present invention also relates to a timepiece comprising such a timepiece component. Finally, the present invention relates to a method for manufacturing this part of a timepiece or jewelry component made of a sintered technical ceramic based on zirconium oxide ZrO₂ and a method for manufacturing such a timepiece component. Background Art

[0002] In the field of horology, as in the jewelry field, it is known to use components made of technical ceramics (also simply referred to as ceramics). The adjective "technical" refers to the high-performance characteristics of the selected ceramics. This is because these technical ceramics can achieve very good mechanical, thermal, even electrical and / or biochemical properties, as well as chemical inertness and magnetism, which makes them suitable for forming timepiece components, especially timepiece movement components, and watch exterior components. The technical ceramics used in this case differ from conventional ceramics in their composition, as they are produced from purified synthetic powders rather than natural mineral powders (such as feldspar or kaolin).

[0003] Among technical ceramics, ceramics based on zirconium oxide are commonly used because they have good mechanical properties. In addition to these mechanical properties, it is beneficial to provide methods for manufacturing such colored ceramics, especially for aesthetic reasons, since zirconium oxide-based ceramics are naturally white. This is because applications in horology and jewelry are also very demanding in terms of aesthetic appearance, especially in terms of color.

[0004] Therefore, a first object of the present invention is to provide a solution for zirconium oxide-based technical ceramics that can achieve high performance while achieving a desired and considered attractive color.

[0005] A second object of the present invention is to provide a solution for zirconium oxide-based technical ceramics that enables the zirconium oxide-based technical ceramics to be manufactured in a simple manner.

[0006] The present invention more generally also relates to a component comprising a part made of technical ceramics, which technical ceramics can be, for example, based on zirconium oxide or based on alumina. Summary of the Invention

[0007] To this end, the present invention is based on a method for manufacturing a zirconium oxide-based part of a timepiece or jewelry component, wherein the method comprises the following stages:

[0008] - Shaping and sintering the zirconium oxide-based part so as to obtain the zirconium oxide-based part in a finished or semi-finished form, and then

[0009] - Depositing a layer comprising a material exhibiting getter properties on at least a portion of the surface of the zirconia-based portion, the material exhibiting a greater affinity for oxygen than zircon of the zirconia-based portion;

[0010] - Heating the zirconia-based portion under vacuum or in a neutral atmosphere so as to obtain at least a portion of the zirconia-based portion darkened and even colored black or grey;

[0011] - Removing the layer comprising the material exhibiting getter properties.

[0012] This darkening or coloring is visible from the surface of the portion.

[0013] The invention is more precisely defined by the claims. Description of the Drawings

[0014] These objects, features and advantages of the invention will be elaborated in detail in the following description given in conjunction with the drawings but not limited to specific embodiments, wherein:

[0015] Figure 1 A logic diagram of a method for manufacturing a zirconia portion of a timepiece or jewelry component according to an embodiment of the invention is schematically shown.

[0016] Figures 2a to 2c The stages of a manufacturing method for coloring an example of a bezel disk according to an embodiment of the invention are schematically shown.

[0017] Figures 3a to 3d The stages of a manufacturing method for coloring an example of a disk according to an embodiment of the invention are schematically shown. Detailed Description

[0018] Subsequently, a "dense" ceramic is understood to mean a ceramic having a density between 95% and 100% of the theoretical density of the material under consideration. In this text, the terms "ceramic" or "technical ceramic" denote dense materials based on stabilized zirconia. The term "portion made of zirconia-based ceramic" or even more simply "zirconia-based portion" will be used to denote a portion made of zirconia-based sintered technical ceramic, thus forming all or part of a timepiece or jewelry component.

[0019] Furthermore, the term "zirconia-based" or "based on zirconia" shall be understood to mean, in all cases, a material that mainly contains a zirconia component, with a weight ratio of at least 50%, even at least 75%, and even at least 90%. Thus, the ceramic material used in the present invention contains at least 50% by weight of zirconia. The zirconia-based material may also include other compounds, particularly but not limited to all or part of the 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.

[0020] The "finished form" of a component or part of a component shall be understood to refer to the component or part of the component whose shape, dimensions, and surface finish have been finally determined. The term "semi-finished form" shall be understood to refer to a component or part of a component whose shape and dimensions are close to the final form, and whose surface finish may be different from the surface finish it will have at the end of the manufacturing process.

[0021] The timepiece or jewelry component at least includes 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 timepiece or jewelry component. According to one embodiment of the present invention, the method for manufacturing such a part of the timepiece or jewelry component includes the steps shown in the Figure 1 logic diagram; the optional steps are shown in dotted lines therein. In particular, it is possible to manufacture at least a locally black or dark-colored part made of zirconia-based ceramic, which is considered very attractive by experts in watchmaking and jewelry aesthetics. The method for manufacturing the zirconia-based part according to the present invention includes the following steps:

[0022] - Shaping and sintering the zirconia-based part E1 to obtain the zirconia-based part in finished or semi-finished form, and then

[0023] - Depositing a layer E2 containing a material exhibiting getter properties on at least a part of the surface of the zirconia-based part;

[0024] - Heating the zirconia-based part E3 under vacuum or in a neutral atmosphere to darken the zirconia-based part at least locally (i.e., visibly in at least a part), or even color it black or gray; and then

[0025] - Removing the layer E4 containing the material exhibiting getter properties.

[0026] As a note, thus the manufacturing method includes a method for coloring the zirconia-based part, more specifically formed by the above steps E2 to E4.

[0027] The first stage starts with a zirconia-based technical ceramic. It involves pre-preparing a bonding ceramic powder, which is shaped and sintered in a known manner to obtain the said part made of zirconia-based technical ceramic. The technical ceramic can be based on yttria-stabilized zirconia, which is optionally colored. Thus, the zirconia-based part produced by this first stage is a dense technical ceramic with a density of 95%-100% of the theoretical density of the technical ceramic. According to one embodiment, the sintered technical ceramic contains a weight proportion of zirconia ZrO2 greater than or equal to 80%, even greater than or equal to 85%, even greater than or equal to 90%. According to one embodiment, the sintered technical ceramic contains a weight proportion of zirconia ZrO2 less than or equal to 94%, even less than or equal to 93%.

[0028] More precisely, the present invention can be advantageously applied to yttria-stabilized zirconia, which is stabilized with 3 mol% of Y2O3, with or without the addition of cerium oxide. In another form, zirconia stabilized with 2 mol% Y2O3 can be used, even 1.8 mol% of Y2O3, even 1.6 mol% of Y2O3.

[0029] In another form, the present invention can be advantageously applied to yttria-stabilized and colored zirconia, initially having a color other than black; for example, green or blue can be used. For example, the zirconia can advantageously contain a pigment prepared from spinel, especially cobalt aluminate. Also for example, the zirconia can include a pigment produced from nickel oxide, iron oxide, cobalt aluminate, alumina, and / or a mixture thereof. In another form, other ways of coloring the ceramic can be used, such as placing the element in a solid solution or other means. Regardless of the way the ceramic is colored, its initial color (at the end of stage E1) is distinguished from its final color (the color obtained at the end of stage E4, at least locally modified with respect to the initial color, as described below).

[0030] For the implementation of the second stage of layer deposition, a material showing oxygen pumping properties is selected, that is, in this case, a material showing a greater affinity for oxygen than zirconium in the zirconia-based ceramic, especially at the heat treatment temperature to be described in detail below; this is understood to mean that the oxygen present in the zirconia will tend to diffuse towards this material during the applied heat treatment rather than remaining in the zirconia. For the sake of simplicity in the description, the term "material showing getter properties" will denote such materials. This is because this application uses a principle similar to that of a non-evaporable getter (NEG or "non-evaporable getter"), whose surface adsorbs oxygen, especially from the vacuum chamber, until it is completely oxidized.

[0031] The thickness of the deposition layer can be selected within a wide range. Preferably, the thickness of the deposition layer will be as thin as possible, and the lower limit of the layer thickness depends on the ability of the material constituting it to store a sufficient amount of oxygen extracted from the ceramic. This sufficient amount depends in particular on its effect on the final obtained color of the surface of the zirconia-based ceramic and on the depth of the darkening of the ceramic relative to its initial color due to the extraction of oxygen. The thicker the material layer with getter properties, the darker the obtained color of the ceramic will be until it becomes black, and / or the darker color will extend further at a relatively large depth of the relevant ceramic. The maximum thickness of the layer of the material exhibiting getter properties additionally depends on the requirement of good adhesion of the layer to the ceramic. This is because too thick a layer can encounter adhesion problems, which can impair its coloring effect in areas of poor adhesion and result in uneven coloring, which is not preferred for aesthetic reasons. Additionally, it should be noted that the effectiveness of the getter properties of the material will also depend on its specific structure, for example, the nanocrystalline morphology increases its storage capacity compared to the crystalline morphology.

[0032] Therefore, those skilled in the art will be able to determine the appropriate parameters of the layer exhibiting getter properties according to the specific situation based on the desired results. Generally, the thickness of the layer can be between 50 nm and 6 μm, but is not limited thereto.

[0033] In addition, the material exhibiting getter properties can 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 containing at least one of these materials.

[0034] In addition, the stage of depositing layer E2 containing the material exhibiting getter properties is preferably 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 any other suitable method.

[0035] Materials presenting getter properties can be deposited on the entire surface of the said part. In an advantageous alternative form, it can be deposited only on a part of this surface. In this alternative form, a mask can be used to mask the surface parts on which the layer is not deposited. For example, masking can be carried out with a photosensitive resin (in this case, a layer of resin is deposited on the surface parts to be masked) or "mechanical" masking (in this case, a self - supporting object used as a mask is pressed onto the surface parts to be masked or even positioned directly above the surface parts to be masked). Thus, in this alternative form, the method includes an intermediate stage which includes masking at least a part of the surface of the zirconia - based part in finished or semi - finished form so as to deposit a layer E2 of getter material in a local manner. In this alternative form, the method also includes another intermediate stage which includes removing the mask E25 after the deposition E2 of the getter layer and before the heat treatment E3 of the said part. For possible cases of masks compatible with the heating stage E3, the mask can be removed after this stage E3 (for example, for a mechanical mask) or during the removal stage E4 (for example, for a mask made of resin). In alternative forms, any method of depositing the getter material in a local manner on parts of the surface of the said part can be envisaged, even if it does not require masking.

[0036] Subsequently, the method implements a stage which includes heating the zirconia - based part E3. During this stage, the getter properties of the deposited material layer will produce their effect by absorbing at least a part of the oxygen contained in the ceramic. To this end, the zirconia - based part can be heated to a temperature of 900 °C - 1300 °C, or even 1000 °C - 1150 °C.

[0037] This heating can be carried out under vacuum, at a pressure of 10 -2 mbar to 10 -10 mbar, or at atmospheric pressure in a neutral atmosphere (based on argon, based on xenon or based on krypton, or based on a mixture of these gases). Any heating conditions that minimize the presence of oxygen in the chamber other than in the ceramic are advantageous and can be implemented. It is also sought to minimize the presence of carbon, nitrogen and / or any element capable of reacting with zirconia during the course of the method.

[0038] It seems that the diffusion of oxygen from zirconia to the getter property layer affects the relevant zirconia-based part, at least part of the oxygen in which becomes sub-stoichiometric (that is, the oxygen decreases compared to the initial state of stoichiometric balance). This change at least locally colors the zirconia-based part black or dark gray, and more generally, at least locally darkens the zirconia-based part; these changes occur at the surface and in the region of the partial volume starting from this surface; since these changes are perceived at the surface of this part, they are particularly used for decorative purposes. Therefore, the coloring method can preferably obtain a black coloring of the ceramic. In an alternative form, a gray coloring can be obtained. These black and gray colors are particularly obtained starting from a semi-finished or finished part that is basically white (produced by the first stage of the method).

[0039] In an alternative form, many other colors can be presented. This is because, if the zirconia-based part contains a coloring pigment, any initial color can generally be presented. As a supplement, in an alternative form, this initial color can be obtained by any other method other than pigmentation. In the rest of this text, the ceramic given the initial color is called "colored zirconia" or "colored zirconium oxide". Then, the method can darken this initial color. Therefore, the method has the general effect of darkening the treated zirconia-based part. This darkening produced by the method of the present invention is due to the fact that the oxygen in zirconia becomes sub-stoichiometric and / or the pigment is modified. The zirconia-based part obtained by the method according to the present invention will be described as a part that "presents a darkened appearance based on sub-stoichiometric oxygen in zirconia". The coloring according to the present invention is carried out in a "subtractive" manner, that is, oxygen is depleted in the initial chemical composition of the zirconia-based part, and no elements are enriched (for example, the coloring does not require the contribution of carbon elements). Therefore, this darkening can be understood by comparison with the color obtained when the present invention is not implemented (that is, the initial color at the end of the shaping and sintering stage E1). Therefore, the coloring method according to the present invention can enable the ceramic to obtain a darkened, or black, or gray coloring. Preferably, the coloring method according to the present invention is used to obtain a black coloring of the colored zirconia.

[0040] The duration of the treatment is highly variable and depends on the desired result. The heat treatment can be from 10 minutes to 10 hours. Similarly, the treatment temperature is highly variable and depends on the desired result.

[0041] As a complement, several alternative embodiments produce different effects. This is because certain alternative embodiments of the present invention can achieve selective coloring, that is, it is only applied to a partial surface of the zirconia-based part. In the case of a particular alternative form, the layer containing the material exhibiting getter properties is not applied to the entire surface of the said part. For example, when the coloring of the present invention is applied to zirconia colored by pigments, such as green and blue pigments produced by spinels (especially cobalt aluminate) or by mixtures of oxides (the mixture contains, for example, cobalt aluminate and other oxides), and in the case where the layer containing the material exhibiting getter properties is not applied to the entire surface of the said part, the coloring of the present invention is selective. In this case, according to the principle of the present invention, only a part of the surface of the said part perpendicular to the locally deposited getter layer is colored. On the other hand, in other alternative embodiments, the coloring according to the present invention can be observed on the entire surface of a part of the component even if the entire surface of the component has not been coated with a layer made of the material exhibiting getter properties. For example, under the tested conditions, such as according to the fourth embodiment to be described later, starting from a part made of zirconia dyed brown with a pigment based on iron oxide Fe2O3, and starting from a part made of zirconia stabilized with yttrium oxide containing alumina Al2O3. In other words, at least partially coating a layer containing the material exhibiting getter properties can obtain coloring in a specific volume of the zirconia-based part in all cases, and this coloring can completely correspond to the surface part where the material exhibiting getter properties exists, that is, it is vertically aligned with the said surface part at a certain depth, or in an alternative form, it may not completely correspond to this surface part and is wider. This is due to the kinetic reasons of the oxygen diffusion phenomenon. Preferably, the coloring method according to the present invention is used to obtain selective coloring of zirconia. More specifically, this method is preferably used to obtain black coloring, which is selectively visible on the surface part vertically aligned with the locally deposited getter layer, and the initial color of the colored zirconia remains on the rest of the surface.

[0042] As a complement, the color of the technical ceramic is measured by spectrophotometry. For a measurement diameter of 4 mm, reflection measurements are carried out with an aperture of 7 mm; the geometry of the measuring device corresponds to diffuse illumination and the spectrum is measured at 8°. If the part does not exhibit a sufficiently flat surface, a reference disk is used for the measurement. Reflectance measurements are carried out between 360 nm and 740 nm, and color evaluation is assumed with the observer located at 10° and under light source D65. The luminance L*, the chromaticity values a* and b*, the chroma C* and the hue angle h* are evaluated in the CIE L*a*b* space defined by the International Commission on Illumination, as shown in the "Technical Report of Colorimetry" CIE 15:2004. The measurements are carried out in SCI (including the specular reflection component) and SCE (excluding the specular reflection component) modes. In addition, the spectrophotometry measurements are carried out on parts in a polished surface state, the roughness of which is preferably defined by the standard roughness parameter Ra, which has a value of 2 nm ± 0.2 nm. As a complement, the parameter Ra is measured according to the standard ISO 4287.

[0043] Thus, more precisely, according to the standardization method explained above, the invention can form a timer part made of two-color, or even multicolor, ceramic, which can include at least one dark-colored part, in particular a black part, defined by the following colorimetric parameters in the SCI mode: L* is less than 47.0, even L* is less than 45.6, even L* is less than 45.4, or L* is between 43.0 and 47.0, even L* is between 44.3 and 45.6, even L* is between 45.0 and 45.4, a* is between -0.1 and 1, even a* is between -0.5 and 1.0, even a* is between 0.3 and 0.9, b* is between -1 and 1.6, even b* is between -0.8 and 1.4, even b* is between 0.3 and 1.1, and L* is between 5.0 and 12.0, a* is between 1.4 and 5.7, b* is between 5.5 and 10.8, in the SCE mode, the original color of the rest is not modified.

[0044] As a complement, the stage of depositing on the one hand a layer containing a material presenting getter properties and on the other hand heating the zirconia-based part can advantageously be carried out in two separate chambers or in the same chamber. In the case where the method includes the above-mentioned intermediate masking stage, it is still possible to implement it in the same chamber if the masking is appropriately treated.

[0045] In this case, the following stages can be processed in the same chamber:

[0046] - depositing a layer E2 comprising a material presenting getter properties on at least a portion of the surface of the zirconia-based part;

[0047] - optionally, removing the mechanical mask E25 (since in some cases, masking can be removed at a subsequent stage);

[0048] - heating the zirconia-based part E3 under vacuum or in a neutral atmosphere so as to obtain at least a portion of the zirconia-based part darkened and even colored black or grey.

[0049] The stage of removing the layer E4 comprising the material presenting getter properties is carried out by chemically cleaning (in particular by chemical dissolution) or mechanically cleaning (in particular by polishing, sandblasting, machining or brushing stages) the surface of the part, possibly involving laser treatment

[0050] According to one embodiment, the foregoing stage of removing the layer E4 comprising the material presenting getter properties can simultaneously finish the surface of the part of the component. In an alternative form, the method can include an optional separate final finishing stage, such as rectification and / or polishing and / or sandblasting and / or satin finishing.

[0051] As appears from the foregoing, the zirconia-based part does not need to contain a getter property material in its volume. Thus, the present invention is not applied by incorporating a getter material in the volume (for example during the formulation of ceramic powder); the getter material must be added in the form of a sacrificial layer at the surface of the part for use. However, according to an alternative embodiment, such a material can be incorporated into the body, in the region of the part, for coloring purposes in order to achieve complementary coloring in addition to the blackening targeted by the present invention.

[0052] Thus, the manufacturing method includes a coloring stage of a part made of zirconia-based ceramic, in particular colored black, and this coloring stage additionally presents the following advantages:

[0053] - it is not necessary to incorporate a coloring pigment in the powder as is usually done in the prior art, and it is not even necessary to add other elements to the ceramic, for example, it is not necessary to impregnate other elements as in the prior art. This is because the coloring according to the present invention directly results from the physical phenomenon of modification of the ceramic itself by oxygen extraction;

[0054] - what is finally obtained is a part made of a single-piece complete ceramic. Specifically, the coloring according to the present invention is not obtained by adding a coloring layer on the surface, and adding a coloring layer would carry the risk of delamination;

[0055] - The coloring stage according to the present invention occurs at the end of the manufacturing method on the already sintered semi-finished or finished component part. Thus, it can be applied in different ways to the same semi-finished or finished part in order to obtain a monochromatic or local (selectively) colored result. It does not require upstream adjustment of the manufacturing method;

[0056] - The coloring stage does not require intervention on the initial powder used to manufacture the timer component, which results in a simple method as it does not require formulating powders specifically for each desired color;

[0057] - Additionally, the coloring stage according to the present invention is reversible. Thus, in the case where the result is not satisfactory, it can be returned to the initial stoichiometric form by reverting to high-temperature heat treatment (not common in the daily life of a watch wearer as it requires reaching several hundred degrees Celsius in an oxidizing atmosphere), and another coloring stage with modified parameters can be carried out again. For the coloring solutions of the prior art, the coloring is irreversible: if the result is not satisfactory, the component is lost and has to be discarded, which is thus less advantageous.

[0058] The present invention also relates to a timer or jewelry component produced by the above manufacturing method. Thus, the present invention relates to a timer or jewelry component comprising at least a zirconia-based part, wherein at least a part of the surface of the zirconia-based part of the timer or jewelry component comprises sub-stoichiometric oxygen and exhibits a darkened, even black or grey appearance.

[0059] Thus, perpendicular to the surface of the zirconia-based part (wherein the zirconia has a modified color according to the present invention), the ceramic exhibits an oxygen-depleted region. This region forms at a certain depth below the said surface. This depth can be selected from a wide range, which is partly defined by the layer made of a material exhibiting getter properties applied during the manufacturing method. Generally, this region is selected to be deep enough to ensure that the color remains unchanged during the use of this part of the component, that is, in particular, to prevent the initial color of the zirconia (present below the colored region of the present invention) from appearing, for example, due to wear of this part or in the case of surface scratching. However, in order not to complicate the manufacturing method, it is advantageously selected to be relatively thin. For example, this depth can be selected to be at least 0.015 mm, preferably 0.015 mm - 1 mm. In an alternative form, the coloring effect according to the present invention covers the total thickness of the component.

[0060] According to an alternative embodiment, the timepiece or jewelry component may include a portion within the body that is colored by a pigment (or colored by any other method), presenting a first region having a first color (the initial color, which is not altered by the present invention), and a second region presenting a different second color (the aforementioned final color induced by the present invention), which presents a darkened, even black or gray appearance due to the sub-stoichiometric oxygen induced by the present invention in this region.

[0061] The zirconia-based portion of the timepiece or jewelry component may be a dense technical ceramic, having a density between 95% and 100% of the theoretical density of the technical ceramic.

[0062] The darkening according to the present invention, for example to obtain black, gray or more generally a dark color, may concern only a portion of the surface (“selective” coloring) of the portion made of sintered technical ceramic based on zirconia ZrO2 of the timepiece or jewelry component, or may extend over the entire surface of this portion.

[0063] The zirconia-based portion may be yttria-stabilized zirconia, optionally colored, in particular with a pigment containing aluminate, in particular cobalt aluminate.

[0064] Preferably, obtaining black according to the present invention concerns only a portion of the surface (“selective” coloring) of the portion made of sintered technical ceramic based on colored zirconia ZrO2 of the timepiece or jewelry component, the remaining portion of the surface retaining its initial color. In this advantageous alternative form, the method can thus obtain a two-color portion, which includes a first portion colored black by treatment according to the present invention and a second untreated portion (retaining its initial color, white or any other color, in particular starting from a conventional pigment).

[0065] Thus, the present invention also relates to a method for manufacturing a zirconia-based portion of a timepiece or jewelry component that is at least two-color, the method comprising the following stages:

[0066] - Shaping and sintering the zirconia-based portion E1, which is optionally colored, in particular by a pigment, in order to obtain the zirconia-based portion in finished or semi-finished form and having an initial color, then - depositing a layer E2 containing a material presenting getter properties only on a first portion of the surface of the zirconia-based portion, a second portion remaining uncovered;

[0067] - Heating the zirconia-based portion E3 under vacuum or in a neutral atmosphere in order to obtain darkening, even coloring to black or gray, of the zirconia-based portion at the first portion, the second portion retaining its initial color; then

[0068] - Removing the layer E4 containing the material presenting getter properties.

[0069] In this method, the second part thus retains its initial color. Additionally, this second part not only retains its initial color, but also generally remains unchanged even through the stage of heating the zirconia-based part.

[0070] The timer part can be any external watch element, such as a bezel, bezel disc, case, case back, center part of the middle plate, dial, decorative plate or bracelet link. In an alternative form, the timer part can be a part of a watchmaking movement.

[0071] The present invention also relates to a timer, in particular a wristwatch, which comprises at least one timer part as described above.

[0072] The timer part can be a one-piece part or can comprise a combination of different parts assembled together. Thus, it can be of a single chemical nature or a combination of multiple chemical natures. Thus, it can comprise one material or multiple different materials, naturally including at least a part made of the zirconia-based ceramic described above.

[0073] The monochromatic, bichromatic or polychromatic part to be treated according to the invention is preferably in a monolithic form, made of a one-piece part, for example monochromatic, having a color called the initial color.

[0074] The part treated according to the invention is advantageously at least bichromatic. Thus, in the case where the part is treated to be bichromatic, it is advantageous to obtain a first part that is locally black and a second part that is locally of the initial color. In this way, there is no weak boundary or interface between the black part and the initial color part, which would occur if the two colors were obtained by elements that are at least partially manufactured separately and then assembled.

[0075] Furthermore, the coloring according to the invention can achieve coloring at a considerable depth of the part, rather than just on the surface. Thus, in the case of surface wear, it has no effect on the color of the part.

[0076] The manufacture of technical ceramics will now be described according to an example of the implementation of the present invention.

[0077] The first embodiment consists of a frustum-shaped bezel disc made of blue tetragonal zirconia (zirconia stabilized with 3 mol% of Y2O3, denoted as "3Y ZrO2"). Its blue color is a coloring obtained by adding a pigment (spinel CoAl2O4) in the body. Mechanical masking is carried out on half of the dial. Subsequently, the disc is placed in a PVD deposition chamber, where a titanium deposit with a thickness of 5 μm is produced on its upper surface, forming a layer made of a material with getter properties. The mechanical mask is removed. Subsequently, the half-coated disc is placed in a vacuum furnace, where it undergoes heat treatment, at 10 -5Under a pressure of mbar and at 1035 °C for 30 minutes. Subsequently, the getter layer is removed (by simple brushing) and the upper surface of the polishing disc. Thereafter, the half-disc coated with the getter layer has a black appearance. As a supplement, the finished bezel disc does not exhibit a metallic appearance in the colored part (black) according to the invention. The remaining part of the bezel disc remains blue. Figures 2a to 2c Schematic view of the upper surface of the bezel disc 1 showing different stages of the coloring method according to an embodiment of the invention as described above:

[0078] Figure 2a Schematically shows the blue monolithic bezel disc 1 at the end of the forming and sintering stage E1;

[0079] Figure 2b Schematically shows the disc 1 at the end of the stage E2 of depositing the titanium layer, where the first half 3 of the disc 1 is covered with the titanium layer and the second half 2 of the disc 1 is not covered with the titanium layer;

[0080] Figure 2c Schematically shows the disc 1 at the end of the stage of heating E3 and then removing E4 the titanium layer, where the first half 3 of the disc 1 turns black while the second half 2 of the disc 1 remains blue.

[0081] The second embodiment relates to a disc made of blue tetragonal zirconia (3Y ZrO2), with a diameter of 3 cm and a thickness of 5 mm. According to the teachings of document CH707424, its blue color is obtained by adding a pigment (spinel CoAl2O4) or by impregnating with cobalt salts and aluminum salts. Its upper surface is polished (which helps to set good resolution). Subsequently, a part of the upper surface of the disc is masked with a photosensitive resin such that the only visible part of the blue zirconia is in the selected positions, for example corresponding to a selected design, such as a butterfly shape. The disc is placed in a PVD deposition chamber where a titanium deposit with a thickness of 5 μm is produced on its upper surface, forming a layer made of a material with getter properties. The masked photosensitive resin is dissolved. Subsequently, the disc locally coated with titanium is placed in a vacuum furnace where it undergoes heat treatment, at 10 -5 Under a pressure of mbar and at 1035 °C for 30 minutes. Finally, the disc is immersed in a suitable chemical solution which makes it possible to remove the titanium coating. Alternatively, it is polished to remove the getter coating. What is finally obtained is a tablet presenting a scene composed of a black butterfly on a blue background, and the assembly has a polished surface state. Figures 3a to 3c Schematic view of the upper surface of the disc 4 during the various stages of the coloring method according to the invention:

[0082] Figure 3a Schematically shows the blue monolithic disc 4 at the end of the forming and sintering stage E1;

[0083] Figure 3b Schematically shows the disk 4 at the end of the intermediate masking stage E15. The first part 6 of the surface of the disk 4 is covered with masking resin, while the second part 5 is not covered;

[0084] Figure 3c Schematically shows the disk 4 at the end of the stage of depositing the titanium layer E2 and removing the mask E25. The second part 5 of the surface of the disk 4 is covered with the titanium layer, and the first part 6 of the surface of the pressing disk 4 is not covered;

[0085] Figure 3d Schematically shows the disk 4 at the end of the stage of heating E3 and then removing the titanium layer E4. The first part 6 of the surface of the disk 4 remains blue, while the second part 5 of the surface of the disk 4 is black.

[0086] The third embodiment is a bezel disk made of green tetragonal zirconia (3Y ZrO2). Its green color is a coloring obtained in the body by adding pigments produced by an oxide combination. Polish its upper surface. A part of the upper surface of the bezel disk is masked with a photosensitive resin so that the visible part of the green zirconia corresponds to half of its surface. Place the bezel disk in a PVD deposition chamber and produce a titanium deposit with a thickness of 5 μm on its upper surface to form a layer made of a material presenting getter properties. Dissolve the masked photosensitive resin. Subsequently, place the bezel disk locally coated with titanium in a vacuum furnace, where it is heat-treated and held at 1035 °C for 30 minutes under a pressure of 10 -5 mbar. Subsequently, the bezel disk is locally processed so that its surface presents a satin finish, which can both remove the coating made of the material presenting getter properties and finish the surface of this part of the bezel disk. The finally obtained bezel disk has half of its upper surface satin black and the other half polished green. Alternatively, processing can be carried out on the entire surface of the disk to obtain a completely satin disk, half green and half black.

[0087] The fourth embodiment relates to a disk made of white zirconia (containing Al2O3), with a diameter of 3 cm and a thickness of 5 mm. Polish its upper surface. Place the disk in a PVD deposition chamber and produce a titanium deposit with a thickness of 3 μm on its upper surface to form a getter layer. Subsequently, place the disk coated with titanium in a vacuum furnace, where it is heat-treated and held at 1035 °C for 10 minutes under a pressure of 10 -4 mbar. Finally, immerse the disk in a suitable chemical solution (alternatively, polish it) so that the getter coating can be removed. A dark gray disk is finally obtained.

[0088] As a supplement, in all these embodiments, the same material presenting getter properties - titanium - is used in order to compare the embodiments with one another. Naturally, the invention is not limited to titanium and, as mentioned above, any other material presenting getter properties can be used in alternative forms. Similarly, the other parameters chosen in these embodiments are provided without limitation. As can be seen from the entire specification, these parameters can vary without departing from the scope of the invention.

[0089] The invention also relates to a method of manufacturing a timer part including at least a partially zirconia-based sintered technical ceramic, wherein the ceramic is bicolor or even multicolor and includes at least a first surface part that has been treated and that presents a dark color, in particular black, the color of which is defined by colorimetric parameters in the SCI mode: L* is less than 47.0, even L* is less than 45.6, even L* is less than 45.4, a* is between -0.1 and 1, even a* is between -0.5 and 1.0, even a* is between 0.3 and 0.9, and b* is between -1 and 1.6, even b* is between -0.8 and 1.4, even b* is between 0.3 and 1.1, with spectrophotometric measurements being made on a part having a polished surface state. The part can additionally include at least a second untreated surface part with an unchanged initial color.

[0090] The invention also relates to a timer part made of ceramic, wherein it is zirconia-based, wherein it is a complete and bicolor or even multicolor one-piece part, including at least a first part of a first color and a second part of a second color different from the first color, in particular including a first blue or green and a second black.

[0091] The invention also relates to a timer part of ceramic made by this manufacturing method, wherein it includes a first black part, the color of which is defined by colorimetric parameters in the SCI mode: L* is less than 47.0, even L* is less than 45.6, even L* is less than 45.4, a* is between -0.5 and 1, even a* is between -0.1 and 1.0, even a* is between 0.3 and 0.9, and b* is between -1 and 1.6, even b* is between -0.8 and 1.4, even b* is between 0.3 and 1.1, with spectrophotometric measurements being made on a part having a polished surface state. The part can include an untreated second surface part with an unchanged initial color.

[0092] According to the invention, technical ceramics other than zirconia-based ceramics have been tested. The results show that the invention can be equally implemented with other technical ceramics, in particular alumina-based ceramics. Thus, all of the above embodiments can be achieved by replacing the zirconia-based part with an alumina-based part.

[0093] Accordingly, the present invention also relates to a method for manufacturing a timepiece or a jewelry component based on technical ceramics, in particular based on alumina, wherein the method comprises the following stages:

[0094] - Shaping and sintering a technical-ceramics-based part E1 so as to obtain the industrial-ceramics-based part in finished or semi-finished form, and then

[0095] - Depositing a layer E2 containing a material exhibiting getter properties on at least a part of the surface of the technical-ceramics-based part, the material showing a greater affinity for oxygen than the technical ceramics of the technical-ceramics-based part;

[0096] - Heating the technical-ceramics-based part E3 under vacuum or in a neutral atmosphere so as to obtain at least a part of the technical-ceramics-based part being darkened and even colored black or grey;

[0097] - Removing the layer E4 containing the material exhibiting getter properties.

[0098] The present invention also relates to a method for manufacturing a timepiece or a jewelry component based on technical ceramics, in particular based on alumina, having at least two colors, wherein the method comprises the following stages:

[0099] - Shaping and sintering the technical-ceramics-based part E1, which is optionally colored, in particular dyed, so as to obtain the industrial-ceramics-based part in finished or semi-finished form and having an initial color, and then

[0100] - Depositing a layer E2 containing a material exhibiting getter properties only on a first part of the surface of the technical-ceramics-based part, a second part of the surface remaining uncovered;

[0101] - Heating the technical-ceramics-based part E3 under vacuum or in a neutral atmosphere so as to obtain the technical-ceramics-based part being darkened and even colored black or grey on the first part, the second part remaining its initial color; and then

[0102] - Removing the layer E4 containing the material exhibiting getter properties.

[0103] The present invention also relates to a timepiece or a jewelry component comprising at least a part based on industrial ceramics, in particular alumina, wherein the timepiece or the jewelry component comprises at least a part of the industrial-ceramics-based part having sub-stoichiometric oxygen and presenting a darkened, even black or grey appearance.

[0104] The invention also relates to a timepiece or a jewellery component, wherein the part based on technical ceramics is dense technical ceramics having a density of 95%-100% of the theoretical density of the technical ceramics, and / or wherein the part based on technical ceramics is technical ceramics stabilized with yttrium oxide, which is optionally coloured, in particular with a pigment containing aluminate, in particular cobalt aluminate.

Claims

1. A method for manufacturing a zirconia-based part for a timepiece or a jewelry component, wherein, The method comprises the following stages: - shaping and sintering the zirconia-based part (E1) so as to obtain the zirconia-based part in finished or semi-finished form, and then - depositing a layer (E2) comprising a material presenting getter properties on at least a portion of the surface of the zirconia-based part, the material exhibiting a greater affinity for oxygen than zircon of the zirconia-based part; - heating the zirconia-based part (E3) under vacuum or in a neutral atmosphere so as to obtain at least a portion of the zirconia-based part being darkened or even coloured black or grey; - removing the layer (E4) comprising the material presenting getter properties.

2. A method for manufacturing a zirconia-based part of a timer or jewelry component having at least two colors, wherein, The method comprises the following stages: - shaping and sintering an optionally coloured zirconia-based part (E1) so as to obtain the zirconia-based part in finished or semi-finished form and in its initial colour, and then - depositing a layer (E2) comprising a material presenting getter properties only on a first portion of the surface of the zirconia-based part, a second portion of the surface remaining uncovered; - heating the zirconia-based part (E3) under vacuum or in a neutral atmosphere so as to obtain the zirconia-based part being darkened or even coloured black or grey on the first portion, the second portion remaining in its initial colour; then - removing the layer E4 comprising the material presenting getter properties.

3. A method for manufacturing a zirconia-based part for a timepiece or a jewelry component as claimed in the preceding claims, wherein, The second portion of the zirconia-based part is kept unchanged by a stage comprising heating the zirconia-based part (E3).

4. A method for manufacturing a zirconia-based part for a timepiece or a jewelry component according to any one of the preceding claims, wherein, The stage comprising depositing a layer (E2) comprising a material presenting getter properties deposits a layer with a thickness of 50 nm to 6 μm.

5. A method for manufacturing a zirconia-based part for a timepiece or a jewellery component according to any one of the preceding claims, wherein, The stage comprising depositing a layer (E2) comprising a material presenting getter 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 presenting getter properties.

6. A method for manufacturing a zirconia-based part for a timepiece or a jewelry component according to any one of the preceding claims, wherein, The stage comprising depositing a layer (E2) comprising a material presenting getter properties is carried out by physical vapour deposition (PVD), or by chemical vapour deposition (CVD), or by atomic layer deposition (ALD), or by pulsed laser deposition (PLD).

7. A method for manufacturing a zirconia-based part for a timepiece or a jewelry component according to any one of the preceding claims, wherein, The stages comprising on the one hand depositing a layer (E2) comprising a material presenting getter properties and on the other hand heating the zirconia-based part (E3) are carried out in the same chamber or in two separate chambers.

8. A method for manufacturing a zirconia-based part for a timepiece or a jewelry component according to any one of the preceding claims, wherein, The method comprises an intermediate stage which comprises masking a portion of the surface of the part (E15) such that the layer (E2) comprising a material presenting getter properties is deposited on a portion of the part not masked by the intermediate stage.

9. A method for manufacturing a zirconia-based part of a timepiece or a jewelry component according to any one of the preceding claims, wherein, The stage comprising heating the zirconia-based part (E3) heats the zirconia-based part to a temperature of 900 °C to 1300 °C, even 1000 °C to 1150 °C.

10. A method for manufacturing a zirconia-based part for a timepiece or a jewelry component according to any one of the preceding claims, wherein, The stage of heating the zirconia-based part (E3) is carried out under a vacuum with a pressure of 10 -2 mbar to 10 -10 mbar, or in a neutral atmosphere based on argon, xenon or krypton.

11. A method for manufacturing a zirconia-based part of a timepiece or a jewelry component according to any one of the preceding claims, wherein, The stage comprising removing the layer (E4) comprising the material presenting getter properties is carried out by chemically cleaning the surface of the part, in particular by chemical dissolution, or mechanically cleaning, in particular by polishing, sandblasting, machining or brushing, optionally involving laser treatment.

12. A timer or jewelry component comprising at least a zirconia-based portion, wherein, The timer or jewelry component includes at least a portion of the zirconia-based portion with sub-stoichiometric oxygen, and at least a portion of the zirconia-based portion exhibits a darkened, even black or gray appearance.

13. The timer or jewelry component according to any one of the preceding claims, wherein, The zirconia-based portion is a dense technical ceramic, the density of the zirconia-based portion being 95% to 100% of the theoretical density of the technical ceramic, and / or wherein the zirconia-based portion is yttrium-stabilized zirconia, which is optionally colored, in particular with a pigment containing aluminate, in particular cobalt aluminate.

14. The timer or jewelry component according to claim 12 or 13, wherein, The zirconia-based portion includes a coloring pigment distributed in its body, and wherein the zirconia-based portion includes a first region colored by the coloring pigment in the body, the first region exhibiting a first color; and a second region corresponding to the zirconia-based region with sub-stoichiometric oxygen, the second region exhibiting the darkened, even black or gray appearance and exhibiting a second color different from the first color.

15. The timer component according to any one of claims 12 to 14, wherein, The timer component is an external element of the watch, such as a bezel, bezel disc, case, case back, center part of the dial, dial, decorative plate or bracelet link, or is a component of the timer movement.

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

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