External element made of zirconia with selectively conductive zones for electronic applications

Abstract

An external element made from a first material for a wearable object, the first material being an insulating ceramic, wherein a surface of the external element is at least partially treated to include at least one conversion with an electrical conductivity.

Claims

1. An external element for a wearable object, the external element being made from a first material, the first material being an insulating ceramic, wherein a peripheral surface of the external element is treated locally so that the surface includes an insulating zone and a conductive zone, the conductive zone including at least one conversion with a non-zero electrical conductivity, wherein the surface includes at least one protruding portion protruding above a top surface of the external element, wherein an entirety of the peripheral surface is configured to be treated to be converted into carbide or nitride, and wherein of the entirety of the peripheral surface of the external element, only a top surface of the protruding portion does not include the carbide or nitride.

2. The external element as claimed in claim 1, wherein the first material is zirconia.

3. The external element as claimed in claim 1, wherein the peripheral surface is selectively treated to be converted into carbide.

4. The external element as claimed in claim 1, wherein the peripheral surface is selectively treated to be converted into nitride.

5. The external element as claimed in in claim 1, wherein the peripheral surface comprises at least one recess, the peripheral surface being treated to be converted into carbide or nitride and polished to localize the conversion to the recess.

6. A wearable object comprising the external element as claimed in claim 1.

7. The wearable object as claimed in claim 6, wherein the wearable object is a timepiece comprising a case formed by a middle, including a bezel, closed by a back and a glass, the wearable object further comprising controlling means, and a strap fastened to the case middle via two pairs of horns, and wherein the external element is arranged in one of the case middle, the bezel, the controlling means, the back, the strap, or a clasp.

8. The wearable object as claimed in claim 7, wherein the wearable object further comprises an electronic module configured to use the peripheral surface treated to include the at least one conversion with a non-zero electrical conductivity to provide at least one function.

9. The wearable object as claimed in claim 6, wherein the peripheral surface treated to include the at least one conversion with a non-zero electrical conductivity is an antenna to provide a communication function.

10. The wearable object as claimed in claim 6, wherein the peripheral surface treated to include the at least one conversion with a non-zero electrical conductivity is an electrode to provide a control function.

11. The wearable object as claimed in claim 6, wherein the peripheral surface treated to include the at least one conversion with a non-zero electrical conductivity is a partition used in a shielding function allowing an electronic component or module to be isolated from interference from another electronic component or module.

12. The wearable object as claimed in claim 6, wherein the peripheral surface treated to include the at least one conversion with a non-zero electrical conductivity is at least one conductive track allowing an electronic component or module to be electrically connected to at least one other electronic component or module.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The aims, advantages and features of the invention will become more clearly apparent from the following detailed description of at least one embodiment of the invention, which is given merely by way of non-limiting example and illustrated by the appended drawings, in which:

(2) FIGS. 1 and 2 schematically show the wearable object according to the invention;

(3) FIGS. 3 to 5 schematically show a first embodiment of the process according to the invention;

(4) FIGS. 6 to 20 schematically show a second embodiment of the process according to the invention; and

(5) FIGS. 21 and 22 schematically show a third embodiment of the process according to the invention.

DETAILED DESCRIPTION

(6) FIGS. 1 and 2 illustrate a wearable object 1 according to the invention. An example wearable object according to the invention is a timepiece. Such a timepiece comprises a case 2 formed by a middle 21 closed by a back 22 and a glass 3. This case 2 encloses an electronic module that may be an electromechanical or electronic watch movement 5. This electronic module may be associated with another element such as a mechanical movement. This wearable object may also comprise a strap 4 comprising two strap halves 4′ or a plurality of links. An external element according to the invention is therefore included in the list comprising the middle, the bezel, the back, the strap, the clasp, the folding buckle or the pin buckle necessary to close the strap. Of course, the watch may also comprise a bezel 23, which is optionally rotatable and optionally integrated into the middle, and controlling means such as a crown head 24 or pushbuttons 24′. The middle 21 will possibly be equipped with an integrated or added bezel.

(7) The external element according to the invention is made from a first material. This material is chosen to be of ceramic type. The ceramic used here is zirconium oxide ZrO.sub.2, which is also called zirconia.

(8) Advantageously, according to the invention, the surface of this ceramic external element 10 is treated. This surface treatment is carried out so as to be selective, i.e. the entirety of the surface of the external element 10 is not necessarily treated. This surface treatment is used in order to obtain a change in electrical conductivity in specific zones.

(9) In a first embodiment, which is shown in FIGS. 3 to 5, the treatment according to the present invention consists in a selective carburization/nitridation of the external element 10 with a focused heat source such as a laser. It will be recalled that a carburization/nitridation consists in activating the part to be carburized/nitrided by heating it in an atmosphere heavy with atoms of carbon or nitrogen.

(10) The first step therefore consists in providing the external element 10 to be treated and in placing it in a chamber E. This chamber E is hermetically sealed and contains an atmosphere A that is heavy with atoms of carbon C or of nitrogen N depending on whether a carburization or nitridation is being carried out. This atmosphere A heavy with atoms of carbon C or of nitrogen N may be created by dissociating compounds such as methane CH.sub.4, dinitrogen N.sub.2 or ammonia NH.sub.3. This dissociation is carried out by heating the raw components in order to break their molecular bonds and to obtain atomic atmospheres.

(11) The second step consists in selectively carburizing or nitriding the external element 10 by activating it by heating the surface of the part in chosen zones 10′. In order to be able to selectively heat said surface in the chosen zones 10′, a focused heat source S, e.g. a laser delivering a laser beam L, is used. This laser beam is preferably pulsed. The surface of the external element 10 is then heated locally in the zones 10′ to a temperature of between 700 and 1100° C. for a time of 30 to 180 minutes. Under the effect of this temperature, the atoms of carbon or nitrogen of the atmosphere A of the chamber E combine with the zirconia surface in the zones 10′ of the external element 10. It is a question of a conversion of the surface of the zones 10′ of the external element 10, over a small thickness of about 10 to 500 nm, into zirconium carbide or zirconium nitride having a metallic aspect of platinum color or of a color close to that of yellow gold, respectively, and a non-zero conductivity. It is therefore a question of superficially modifying the structure of the zirconia to obtain a new crystal structure corresponding to that of zirconium carbide/zirconium nitride and not of adding a coating that is liable to be torn off or to detach from the surface of the article, in particular when the latter is subjected to severe wear conditions. More particularly, the surface layer that has the zirconium-carbide or zirconium-nitride structure extends from the surface to a depth of between 10 and 500 nm.

(12) In point of fact, zirconium carbide and zirconium nitride have a non-zero electrical conductivity in contrast to zirconia, which is considered to be an insulator. Thus, the zones that are carburized or nitrided have a non-zero electrical conductivity. As the rest of the external element is not converted, conductive zones encircled by insulating zones result.

(13) To carry out the various steps, a plurality of methods of execution may be employed.

(14) In a first method of execution, the dissociation of the gas to obtain an atmosphere that is heavy with atoms of carbon C or of nitrogen N and the local activation of the surface of said external element use the same laser.

(15) In a second method of execution, the dissociation of the gases to obtain an atmosphere that is heavy with atoms of carbon C or of nitrogen N is carried out with a first heat source whereas the local activation of the surface of said external element 10 uses the laser.

(16) In a third method of execution, the dissociation of the gases to obtain an atmosphere that is heavy with atoms of carbon C or of nitrogen N is carried out with a first heat source, and the external element 10 is heated via a second heat source whereas the local activation of the surface of the external element uses the laser. This third method of execution allows the external element 10 to be preheated uniformly and a smaller temperature difference to be obtained in the zone of the surface of the external element 10 treated by the focused heat source.

(17) One advantage of this first embodiment is that it easily allows the surface of the external element 10 to be activated selectively. Specifically, a laser beam has the advantage of having an adjustable beam diameter.

(18) In a second embodiment, which is shown in FIGS. 6 to 20, the process uses a selective metallization as mask to obtain a selective carburization or nitridation of the surface of the external element 10.

(19) The first step therefore consists in providing the external element 10 and in depositing a metallization 11 on its surface. This metallization is selective, i.e. it is carried out on the one or more zones that it is desired to carburize or to nitride. This metal deposit is for example made from a material comprised in the list including chromium, tantalum, molybdenum, tungsten, niobium, titanium and silicon and is produced using one of a number of methods of execution.

(20) In a first method of execution, which is shown in FIGS. 7 and 8, the metallization is produced by masking the surface of the external element 10 via a mask 12, then depositing a metal via a physical-vapor-deposition (PVD) process. Thus, only those zones Z that are not covered by the mask receive the metal deposit 11.

(21) In a second method of execution, which is shown in FIGS. 9 to 12, the metallization is produced by depositing a masking layer 13, such as a layer of Kapton or a layer of ink or of lacquer or of resin, on the surface of the external element. This layer 13 is then selectively etched depending on the desired esthetic appearance, causing apertures 13′ to appear. The whole lot is then covered with a metal layer 11 by PVD deposition, the layer being deposited both on the masking layer 13 and in the recesses formed in said mask. Lastly, the masking layer 13 is removed by chemical etching, leaving the metal layer 11 only in the zones Z corresponding to the locations of the recesses 13′ of the removed mask.

(22) In a third method of execution, which is shown in FIGS. 13 to 15, the selective metal deposition consists in depositing a metal 11 over the entire surface of the external element 10 in order then to use a focused heat source S such as a laser to structure the deposited metal layer 11. This structuring consists in etching the surface of the external element 10 in order to remove the metal layer 11 in undesired locations and to leave the metal layer 11 in the desired zones Z.

(23) In a fourth method of execution, which is shown in FIGS. 16 to 18, the selective metal deposition consists in depositing the metal over the entire surface of the external element 10. Subsequently, a photolithography step is used with a mask 12 to locally modify the deposited metal layer 11. This local modification is followed by a chemical etching step in order to remove the metal layer 11 in the undesired locations and to leave it in the desired zones Z.

(24) Once this metal deposition has been carried out, the following step consists in carburizing or nitriding the external element 10 with the metal layer 11 in the zones Z of its surface. To do this, the external element 10 is placed in a chamber E that contains an atmosphere A that is heavy with atoms of carbon C or of nitrogen N, as indicated in FIG. 19. The whole lot is then heated using a plasma technique such as described in patent EP 0 850 900. However, the metal deposit 11 here plays the role of a shield preventing the carburization/nitridation of the zones covered with this metal deposit 11 and allowing the non-covered zones 10′ to be converted, as shown in FIG. 20.

(25) In a following step, the metal deposit 11 is chemically dissolved in order to let the zirconia appear in its original color. Therefore, an external element having an exposed zone and a carburized/nitrided, and therefore conductive, zone is obtained.

(26) In a third embodiment, the selective conversion of the surface of the external element into a conductive zone uses the principle of carburization/nitridation and structuring.

(27) In a first method of execution, which is shown in FIG. 21, the first step consists in providing the zirconia external element 10. This first step also consists in structuring this external element 10. This structuring may be carried out in two different ways: during the manufacture of the external element 10 or subsequent to this manufacture.

(28) In the case where the structuring is carried out during the manufacture of the external element, it will be understood that this manufacture consists in mixing together powders in order, subsequently, to place them in a mold and to sinter them, i.e. to subject them to a temperature and a pressure such that a conversion occurs. Thus, the mold in which the powders are placed may have a shape that includes the desired reliefs and structures.

(29) In the case where the structuring is carried out subsequent to the manufacture of the external element, laser or mechanical machining is envisionable.

(30) In a second step, the external element is carburized or nitrided. To do this, the structured external element 10 is placed in a chamber E in which there is an atmosphere A that is heavy with atoms of carbon or nitrogen. The whole lot is then heated via a plasma for a set time in order to convert the surface of the external element 10 into conductive zirconium carbide or conductive zirconium nitride, respectively. This carburization/nitridation is therefore carried out over the entirety of the surface of the external element.

(31) In a third step, the external element undergoes a polishing step. This polishing step consists in removing the surface layer of the external element 10. However, the external element 10 is equipped with structures 17 that take the form of recesses 17b or protruding portions 17a, these recesses 17b or protruding portions 17a themselves being carburized/nitrided. Therefore, the polishing does not concern the whole of the surface of the external element 10. Specifically, in the case where the structures 17 are recesses, the polishing operation leaves the carbonization/nitridation, i.e. the conductive portions, in the recesses. In the case where the structures 17 are protruding portions, the polishing operation removes the carbonization/nitridation from these protruding portions.

(32) Thus, a relief is obtained the recesses of which are selectively conductive.

(33) In a second method of execution, which is shown in FIG. 22, the first step consists in providing the zirconia external element.

(34) In a second step, said external element is carburized/nitrided. To do this, the structured external element 10 is placed in a chamber in which there is an atmosphere that is heavy with atoms of carbon or nitrogen. The whole lot is then heated via a plasma for a set time in order to convert the surface of the external element into conductive zirconium carbide or conductive zirconium nitride, respectively. This carburization/nitridation is therefore carried out over the entirely of the surface of the external element.

(35) In a third step, the external element 10 undergoes a structuring step. This step consists in removing material from the external element. To do this, laser or mechanical machining is used. The removal of material may be carried out so as to locally remove only the surface layer of 10 to 500 nm thickness that has been converted into carbide or nitride. However, the removal of material may be carried out so as to accentuate the relief in the conductive zones.

(36) This conversion of the surface of the external element to achieve zones having an electrical conductivity allows electrical tracks to be produced in order to electrically connect an electronic component or module to at least one other electronic component or module, integrated antennas to be produced, and electrodes for touch controls or buttons to be produced. These zones having a non-zero electrical conductivity will be used by the electronic module of the wearable object. These zones having a non-zero electrical conductivity also allow a shielding function, i.e. a function allowing one electronic component or module to be isolated from interference from another electronic component or module, to be provided.

(37) It will be understood that various modifications and/or improvements and/or combinations that will be obvious to those skilled in the art may be added to the various embodiments of the invention described above without departing from the scope of the invention such as defined in the appended claims.

(38) Thus, it will be understood that the external element may be treated in various locations on its surface.