CH716916A2 - A method of manufacturing a decorative surface, a decorative object with a multicolored surface, and a watch comprising such objects. - Google Patents

Abstract

According to the present invention, a layer of lanthanum boride of LaBx stoichiometry with x between 9 and 12 is deposited on a substrate, for example a stainless steel dial of a watch, and then treated by a laser, so that the portions of the layer treated by the laser change color depending on the power of the laser. This method makes it possible to produce multi-colored surfaces having a high resistance to corrosion and abrasion. Preferably, the LaB x layer is deposited by PVD (Physical Vapor Deposition) and by cathode sputtering, from a purple-violet color LaB 6 target, so that the color of the deposited layer differs from the color of target. The laser treatment at specific powers changes the stoichiometry of the layer in the treated portions, so that the color of these portions changes depending on the stoichiometry obtained. At higher powers, the laser will essentially remove the LaBx layer, so the color of the processed portions is determined by the material of the substrate.

Description

Technical area

The invention relates to the field of the manufacture of decorative surfaces for luxury items, such as watches or jewelry. The invention relates more particularly to the use of lanthanum hexaboride (LaB6) for the production of such decorative surfaces.

Technological background

Lanthanum hexaboride is one of the rare earths. Due to its very low “work-function”, around 2.4 eV, this material is widely used in electronics. One of the main uses is the manufacture of hot cathodes.

[0003] The LaB6 stoichiometry has an intense purple-violet color, and the neighboring stoichiometries can take, for example, blue or green colors. This ceramic has a very high hardness (around 2500 HV), and a high resistance to corrosion.

Summary of the invention

According to the present invention, a layer of lanthanum boride of LaBx stoichiometry is deposited on a substrate, for example a stainless steel dial of a watch, and then treated by a laser, so as to modify said stoichiometry of said portion of the LaBx layer subjected to the LaBy laser treatment and to give it a color, said color obtained being determined by the parameters of the laser. Switching from LaBx to LaBy is done by adjusting the laser parameters. The parameters of the laser are in particular the duration of the pulses, the average power of the laser beam, the energy per pulses, the repetition frequency, the diameter of the spot, the overlap of the spots in the longitudinal and transverse direction and the fluence per pulse.

Advantageously, the LaBx layer is transformed by the laser treatment into LaByavec including between 9 and 12.

This method makes it possible to produce multicolored surfaces having a high resistance to corrosion and abrasion. Preferably, the LaBx layer is deposited by PVD (Physical Vapor Deposition), and preferably by cathodic sputtering, from a purple-violet color LaB6 target, so that the color of the deposited layer differs from the color of the target. The laser treatment at specific powers changes the stoichiometry of the layer in the treated portions, so that the color of these portions changes depending on the stoichiometry obtained. At higher powers, the laser will essentially remove the LaBx layer, so the color of the processed portions is determined by the material of the substrate.

The invention also relates to a decorative object produced by the method of the invention, in particular an object comprising a substrate provided with a layer, the layer comprising at least two portions of different colors with respect to one another. other, the portions consisting at least at their surface of lanthanum boride determined by different lanthanum boride stoichiometries in the different portions. Preferably, one of the portions of the surface of said layer comprises a LaByavec including between 9 and 12.

Detailed description of the invention

A detailed embodiment of the invention will be described below. This embodiment does not limit the scope of the invention, but serves only as an example of an implementation of the method according to the invention.

[0009] The target is prepared by depositing LaBx with x = 6 in the form of a powder of violet purple color on a sole, preferably made of copper. The powder is sintered and brazed to the sole, so that a solid layer, still purple-violet in color, is formed on the sole, which can serve as a target for the application of a PVD coating by sputtering. Typically the thickness of the solid layer is of the order of 500 nm (0.5 µm). Footings provided with LaB6 and prepared in advance are available for PVD applications. In the example of the method described below, the inventors used a sole provided with a circular layer of LaB6 having a diameter of approximately 75 mm.

A 20 mm X 30 mm stainless steel substrate is introduced into a reactor of the RF-CCP (Radio-Frequency Capacitively Coupled Plasma) type, and is placed on a platform inside the reactor chamber. The reactor comprises a support capable of holding the target and a standard RF source. The reactor is provided with means for reducing and regulating the pressure inside the chamber, and means for introducing a flow of a gaseous fluid, such as argon, into the chamber.

In the current example, the reactor is operated in confocal mode. This implies that the target is placed at an angle of preferably 30 ° relative to the central axis and perpendicular to the platform. The platform is rotatably mounted and can rotate around this central axis.

A step of cleaning the substrate is first performed, by subjecting it to a pickling process (etching), for example by means of an argon plasma created in the reactor chamber, after the installation of the target. The parameters of this pickling step are for example the following: pressure 1.5 10 <-2> mbar; duration 5 min; acceleration voltage 600 V.

Then, the target is used in the support so as to play the role of cathode during PVD deposition, and so that the distance between the target and the center of the substrate is typically 110 mm. The deposition of a lanthanum boride layer approximately 500 nm thick by PVD in argon, via cathodic sputtering of the target, takes place under the following typical conditions: • Power applied to the cathode: 250 W (ie 404 V for 0.62 A in DC mode) • Ar pressure: 3 µbar. • Deposition temperature: 430 ° C (this temperature is a set point programmed on the machine, and not the actual temperature measured on the substrate). • Bias applied to the cathode with respect to the substrate: - 150V DC • Deposition time: 1500 seconds to obtain 300 nm (0.2 to 0.25 nm / s). • Substrate rotation speed: approximately 10 revolutions / minute

It is found that the color of the deposited layer differs from the purple-violet color of the target. The color of the deposited layer is slate gray-blue. The explanation for this difference in coloration is provided by the SEM-EDX analysis of the layer. It is no longer a layer of LaB6 stoichiometry like the target, but of a LaB9 to LaB12 stoichiometry, hereinafter called LaBy. This is because the spray rates of lanthanum and of boron are different, which leads to a layer enriched in boron and therefore depleted in lanthanum.

According to the invention, the local laser treatment of the layer deposited by PVD, will again change the color of the layer. A marking laser is used operating in the infrared field. The laser is controlled to scan a spot over a predefined portion of the surface of the LaBx layer. Depending on the parameters applied, three different colors can be obtained on adjacent areas of the same substrate: blue, purple and gray-white, so as to obtain a multicolored pattern on the substrate. The following table discloses the typical parameters applied in the three cases.

It has been found that it is first and foremost the power of the laser which defines the color obtained. Differences in frequency, overlap, and pulse duration have little or no influence on color, but may result in different shades of the same color.

SEM-EDX analysis established that the blue and purple layers consist of specific lanthanum boride stoichiometries which determine the colors in question. On the other hand, the gray-white layer contains little boron and lanthanum, but its color is determined by the presence of Fe and Ni in the stainless steel substrate. This means that the LaBy layer has essentially been removed or partially removed and the color is determined primarily by the color of the substrate.

A series of nano-indentations was able to show that the layer deposited by PVD had a hardness of about 2500 HV, and that after laser treatment it retained a hardness of 1500 HV for purple and 1000 HV for blue, which is sufficient for watch applications exposed to abrasion. On the other hand, a “tropical climate” test, ie exposure in an enclosure to a temperature of 60 ° C, with an RH% of 90% for 7 days, showed that the coating was in no way affected.

[0019] Thus, in a non-limiting manner and since the laser spot does not pass through the LaBx layer, it is possible to decorate according to this method a horological component such as a watch dial, hands, a watch case, a clasp element or bracelet link.

Of course, the present invention is not limited to the example illustrated but is susceptible to various variants and modifications which will appear to those skilled in the art. In particular, the invention cannot be limited to a piece of watchmaking trim or even to the watchmaking field. Thus, by way of example, nothing prevents the use of the method according to the invention for an application in the field of tableware, jewelry, jewelry, leather goods or even writing instruments. .

Claims (14)

1. Method of manufacturing a decorative surface on a substrate, characterized in that the method comprises the following steps: • deposit a layer of LaBx on the substrate having a first stoichiometry, • subjecting at least a portion of the LaBx layer to a laser treatment, so as to modify said LaBx stoichiometry of the said portion of the LaBx layer subjected to the laser treatment, in LaBy and give it a color said color obtained being determined by the type laser source, as well as the laser parameters. 2. Method according to claim 1, characterized in that the layer is deposited by PVD (Physical Vapor Deposition). 3. Method according to claim 2 characterized in that the layer is deposited by cathodic sputtering of a target comprising LaB6 in the form of a sintered powder and brazed on a sole. 4. Method according to claim 3, characterized in that the PVD deposition is carried out in a reactor of the RF-CCP (Radio-Frequency Capacitively Coupled Plasma) type. 5. Method according to any one of the preceding claims, characterized in that the LaBx layer is transformed by the laser treatment into LaByavec including between 9 and 12. 6. Method according to any one of the preceding claims, further comprising a step of etching the substrate, before the deposition of the LaBx layer. 7. Method according to any one of the preceding claims, characterized in that several adjacent portions of the layer are treated by the laser at different powers, so as to obtain a multicolored pattern on the substrate. 8. Method according to any one of the preceding claims, characterized in that the laser treatment uses a marking laser, operating in the infrared range, and by scanning a spot of the laser on said at least one. a portion of the surface of the deposited layer. 9. Method according to any one of the preceding claims, characterized in that the color of the portion treated by the laser is obtained by a change in the stoichiometry of the LaBx layer under the influence of the laser and as a function of the power of laser, or by the total or partial removal of the LaBx layer so that the color obtained is determined by the color of the substrate. 10. Decorative object with a multicolored surface comprising a substrate provided with a layer, characterized in that said layer comprises at least two portions of different colors with respect to each other, the portions consisting at least of their boride surface. of lanthanum determined by different lanthanum boride stoichiometries in the different portions. 11. Decorative object according to claim 10, characterized in that one of the portions of the surface of said layer comprises a LaByavec including between 9 and 12. 12. Object according to claim 10 or 11, characterized in that the portions of different colors are adjacent portions. 13. Object according to one of claims 10 to 12, characterized in that the surface of the substrate further comprises one or more additional portions, the color of which is determined by the substrate itself. 14. Watch characterized in that the watch comprises one or more components according to any one of claims 10 to 13.