Elastic return member for timepiece movement

Abstract

An elastic return part, in particular a helical spring, for an inertial element of a timepiece movement, characterised in that it comprises a base body on which is deposited a coating comprising: a first oxide or nitride or carbide primer layer; and a second layer of hydrophobic and / or oleophobic material formed from a self-assembled monolayer (SAM).

Description

Technical Field

[0001] This invention relates to a resilient return component, particularly a helical spring, for an inertial element in a watch movement. The invention also relates to a watch movement or timepiece, particularly a watch, including such a resilient return component. Finally, the invention relates to a method for manufacturing such a resilient return component, particularly a method for treating the surface of such a component. Background Technology

[0002] The phenomenon of frequency drift over time in inertial elements used in watch movements (especially balance wheel-hairspring oscillators) is well known to watchmakers. Therefore, an oscillator equipped with a helical spring made of a coarse ferromagnetic alloy may see its frequency gradually increase, reaching a rate change of approximately 10 seconds per day after a year. To reduce this drift, a heat treatment called oven treatment is typically performed, which reduces the rate drift to less than 1 second per day during the initial years.

[0003] As reported in document EP1039352, the same drift phenomenon was observed in helical springs made of paramagnetic alloys, particularly Nb-Zr alloys. In the case of paramagnetic alloy helical springs, the same type of annealing reduced the drift to approximately 5 seconds / day after one year. Another solution proposed in document EP1039352 is to grow an alloy oxide layer on the surface of the helical spring, particularly by anodizing. The advantage of this process is that the oxide layer is formed at low temperatures without altering the crystal structure of the helical spring, where the thickness (and therefore the color) is fully reproducible. However, the anodizing solution is sometimes insufficient or even unsuitable for certain materials. It cannot be performed on helical springs with collets and / or assembled studs.

[0004] The above phenomenon is an example of irreversible drift. There are also reversible drifts, for example, caused by climatic conditions such as changes in temperature and pressure.

[0005] The purpose of this invention is to provide a solution for improving the frequency stability of an elastic return component of an inertial element used in a watch movement. Summary of the Invention

[0006] Therefore, the present invention is based on an elastic return component for an inertial element in a watch movement, particularly a helical spring, wherein it includes a substrate on which a coating is deposited, the coating comprising:

[0007] - A first primer layer of oxides, nitrides, or carbides; and

[0008] - A second layer of hydrophobic and / or oleophobic material formed by self-assembled monolayers (SAM).

[0009] The thickness of the first primer layer can be between 1 and 20 nm, or between 1 nm and 10 nm, or between 1 nm and 6 nm, or between 1 nm and 5 nm, or between 1 nm and 3 nm.

[0010] The thickness of the coating can be less than or equal to 20 nm, or even less than or equal to 10 nm, or even less than or equal to 7 nm, or even less than or equal to 6 nm, or even less than or equal to 5 nm.

[0011] The first primer layer can be made of a single material. Alternatively or additionally, the first primer layer may comprise aluminum oxide (Al2O3), titanium dioxide (TiO2), hafnium dioxide (HfO2), zirconium dioxide (ZrO2), niobium pentoxide (Nb2O5), or zinc oxide (ZnO).

[0012] The second layer of hydrophobic and / or oleophobic material may include fluorinated, perfluorinated, or aliphatic hydrophobic molecules.

[0013] Fluorinated or perfluorinated hydrophobic and / or oleophobic molecules may be selected from perfluorodecyltrichlorosilane (FDTS), fluorooctyltrichlorosilane (FOTS), perfluorodecanoic acid (PFDA), and pentafluorobenzenethiol (PFBT). Alternatively, the aliphatic hydrophobic and / or oleophobic molecules may be selected from octyltrichlorosilane, dodecyltrichlorosilane (DTS), and octadecyltrichlorosilane (OTS). Alternatively, the hydrophobic and / or oleophobic molecules may be selected from dichlorodimethylsilane (DDMS) and 1,2-bis(trichlorosilyl)ethane (BTSCE).

[0014] The substrate may be: a paramagnetic alloy based on niobium or titanium, optionally oxidized, such as a niobium-zirconium (Nb-Zr) or niobium-titanium (Nb-Ti) alloy; or a ferromagnetic alloy, optionally oxidized; or monocrystalline or polycrystalline silicon, optionally coated with a silicon oxide (SiO2) layer; or glass; or ceramic; or a carbon-containing compound, such as carbon nanotubes or diamond.

[0015] The substrate may be made of a paramagnetic alloy based on niobium or titanium and covered with an anodic oxide layer with a thickness between 5 nm and 200 nm, the anodic oxide layer itself being covered by a coating.

[0016] The elastic return component can be a helical spring with or without a bridle and / or clamp.

[0017] The coating can be deposited on the entire surface of the elastic return component.

[0018] The present invention also relates to a watch oscillator or watch movement comprising the elastic return component as described above.

[0019] The present invention also relates to a clock, particularly a watch, comprising at least one resilient return component as described above.

[0020] The present invention also relates to a method for treating the surface of a substrate for an elastic return member (particularly a helical spring) of an inertial element in a watch movement, wherein the method comprises depositing a coating on the substrate surface by means of the following steps:

[0021] - The first step of depositing a first primer layer of oxides, nitrides, or carbides by atomic layer deposition (ALD), physical vapor deposition (PVD), or chemical vapor deposition (CVD); and

[0022] - A second step to deposit hydrophobic and / or oleophobic materials via self-assembled monolayers (SAM).

[0023] The processing may include the step of oxidizing the elastic return component, particularly by anodizing, which is performed before the first deposition step.

[0024] The processing may include an oven treatment step for the elastic return component, which is performed before the first deposition step or after the second deposition step.

[0025] The first and second steps, as well as the optional oven treatment step, can be carried out continuously in the same chamber, especially at the same temperature.

[0026] The first and second steps can be performed at temperatures below 300°C or even below 200°C and / or at temperatures above 80°C.

[0027] This invention is more precisely defined by the claims. Attached Figure Description

[0028] These objects, features, and advantages of the present invention will be explained in detail in the following description of specific embodiments with reference to the accompanying drawings, which are provided by way of example and are not intended to be limiting, in which:

[0029] Figure 1 The variation of the daily rate M of the hairspring according to an embodiment of the present invention (2) over time T is shown compared with a reference hairspring (spiral) (1).

[0030] Figure 2 The effect of the Al2O3 layer thickness E on the maximum rate change VM of the hairspring is shown. Graph (3) shows the maximum rate change VM of the reference hairspring. Graph (4) shows the maximum rate change VM of the hairspring according to an embodiment of the present invention. Detailed Implementation

[0031] This invention relates to a method for manufacturing an elastic return component for an inertial element in a watch movement, the method specifically comprising a method of treating the surface of a substrate of the component, wherein the method includes depositing a coating on the substrate surface by the following steps:

[0032] - The first step of depositing a first primer layer of oxides, nitrides, or carbides, for example by atomic layer deposition (ALD), physical vapor deposition (PVD), or chemical vapor deposition (CVD); and

[0033] - A second step to deposit hydrophobic and / or oleophobic materials via self-assembled monolayer (SAM) deposition.

[0034] The following description will be detailed in the case of a resilient return component for an inertial element in a watch movement, which is a helical spring, more simply referred to as a "hairspring," intended for integration into a balance wheel-hairspring type oscillator. Naturally, the invention remains generally applicable to any resilient return component for an inertial element in a watch movement. For example, the helical spring can be replaced by one or more blades that provide resilient return and may guide the inertial element.

[0035] As is well known, hairsprings can be made from various materials, particularly micromachinable materials. Micromachinable materials are those that allow for the fabrication of watch components using microfabrication techniques, particularly those involving photolithography or the use of lasers. Thus, such watch movement components, particularly their general shape, can be obtained, for example, at least in part, through deep reactive ion etching (DRIE) steps. Alternatively, such watch movement components, particularly their general shape, can be obtained, for example, at least in part, through UV-Liga (Litographie Galvanik Abformung (photolithography, electroplating, and molding)) techniques. Alternatively, hairsprings can be made from metal alloys, obtained, for example, by melting and solidifying the constituent elements, shaping the alloy to the desired shape and size through drawing and rolling steps, and then forming and fixing it through drawing and heat treatment. For example, hairsprings can be made entirely of paramagnetic alloys or based on paramagnetic alloys, such as niobium-zirconium (Nb-Zr) or niobium-titanium (Nb-Ti) alloys, and / or titanium-based alloys. Alternatively, the material may be a ferromagnetic alloy (e.g., a Nivarox-type alloy), or monocrystalline or polycrystalline silicon with or without a SiO2 layer (as described below), glass, ceramic, or a compound containing various forms of carbon (e.g., carbon nanotubes or diamond).

[0036] Finally, the manufacturing process includes a preparatory step, which includes obtaining a hairspring based on one of the aforementioned materials, i.e., the hairspring comprising at least 50% by weight of such material, or being made entirely of such material.

[0037] On the other hand, the present invention is compatible with or even complementary to solutions in the prior art, and such a hairspring can undergo the first known treatments as described above, such as oven treatment and / or anodizing. The hairspring produced by this preparatory step forms or includes a matrix comprising surfaces that will be treated by the present invention to further improve its performance. Thus, such a matrix can be based on one of the aforementioned materials, the surface layer of which can be oxidized (anodic oxidation and / or thermal oxidation).

[0038] The present invention then proposes a treatment of the surface of the substrate, which may optionally have undergone other pretreatments. It should be noted that this treatment is preferably applied to the entire outer surface of the hairspring. Alternatively, only a portion of the surface may be treated.

[0039] The first step in this surface treatment involves depositing a first primer layer of oxide, nitride, or carbide. Since this first layer is intended to bond the second layer, it is selected from materials suitable for bonding the second layer and the substrate formed by the hairspring. It should be noted that, in addition to its primary bonding function, the first primer layer preferably also performs a secondary function of improving the stability of the hairspring itself, which will be detailed below.

[0040] Preferably, for paramagnetic alloy hairsprings made of, for example, Nb-Zr or Nb-Ti, with or without anodization, the material of the first primer layer may advantageously be an oxide selected from the oxides Al2O3, TiO2, HfO2, ZrO2 or Nb2O5.

[0041] Furthermore, the first primer layer can be deposited by physical or chemical deposition, advantageously by ALD, PVD, or CVD techniques. Alternatively, electrochemical deposition or thermal or thermochemical treatment or any other technique known to those skilled in the art can be used.

[0042] The first primer layer is preferably deposited in a facility that sequentially allows for a first step of depositing the primer layer followed by a second step of depositing SAM (e.g., a chamber that allows for CVD or ALD deposition and SAM deposition).

[0043] The thickness of the first primer layer represents a trade-off between the various functions and advantages it provides. Therefore, this thickness is preferably chosen to be between 1 nm and 20 nm, or even between 1 nm and 10 nm, or even between 1 nm and 6 nm, or even between 1 nm and 5 nm, or even between 1 nm and 3 nm. This trade-off satisfies the following objectives:

[0044] - Ensure the effectiveness of sediments, especially the effectiveness of their two functions (i.e., adhesion and stabilization);

[0045] - The properties of the component are not degraded, and the effects on its physical and mechanical properties (such as stiffness, thermoelastic coefficient, and natural oscillation frequency) are negligible. Therefore, minimum thickness is advantageous.

[0046] - The impact on color is negligible. Therefore, minimum thickness is advantageous;

[0047] - To minimize the risk of primer cracking and delamination due to residual stress generated at the interface during deposition. This is important for components subjected to mechanical stress during tension / compression and / or bending (e.g., watch hairsprings);

[0048] - In addition to its color, it also minimizes the aesthetic impact on the helical spring, for example by minimizing the impact on the shape of the limiter and chuck, since the shape is not affected by the very thin coating.

[0049] ALD technology is preferred for depositing the first primer layer because it allows for the deposition of the final layer at a perfectly consistent low temperature, which continuously covers rough surfaces and uneven areas with a very thin, continuous layer. For example, the low temperature respects the structure of the substrate and does not alter its crystallographic structure.

[0050] We will describe in detail how to achieve the first layer deposition using ALD. One or more helical springs to be treated are placed on metal supports (e.g., stainless steel or aluminum) or plastic supports that are resistant to the temperatures required for deposition (up to 200°C) and suitable for vacuum operation. Such plastic supports are made of, for example, PEEK (polyetheretherketone) or PPS (polyphenylene sulfide). The supports holding one or more springs are then placed inside the ALD reactor.

[0051] Once the deposition temperature is reached within the loaded reactor, a stabilization step is performed, followed by alternating exposure of one or more filaments to the chemical precursor. Deposition is preferably carried out under a continuous flow of nitrogen (N2), for example, at about 20 sccm (standard cubic centimeters per minute) and / or, for example, at a pressure of about 20 Pa. One or more filaments are sequentially or alternately exposed to vapors of trimethylaluminum (TMA) and water (H2O) vapor to form an Al2O3 oxide layer (in a continuous partial layer), the oxide layer having an average thickness of, for example, 0.1 nm per exposure cycle, until the desired thickness is achieved by repeating the exposure cycles.

[0052] The baseline pressure achieved in the reactor when there is no precursor or gas flow can depend on the characteristics of the vacuum chamber and the pump. For example, for small reactors, it can be less than or equal to 0.1 Torr (<20 Pa), preferably less than 0.01 Torr (<2 Pa).

[0053] For example, the pressure reached in the chamber under a nitrogen flow is typically 20 Pa, with an operating window between 5 Pa and 50 Pa. The pressure may depend on the deposition chamber and the nature and surface area of ​​the part to be coated.

[0054] Then, the second step of depositing a second layer of hydrophobic and / or oleophobic material by self-assembled monolayer (SAM) is achieved using the substrate surface treatment process according to the invention. It should be noted that, depending on the material chosen, the thickness of this second layer is very small, approximately 1 nm.

[0055] This second layer can be deposited at different stages of the hairspring manufacturing process, as long as the hairspring does not undergo any subsequent heat treatment at temperatures above 300°C.

[0056] Therefore, the surface treatment of this invention allows for the deposition of coatings comprising two stacked layers. This coating deposition process has the advantage of compatibility with different hairspring configurations. For example, it can be deposited with:

[0057] - On a shaped hairspring without a limiter and without a chuck; or

[0058] - On the hairspring after assembling the limiter and / or chuck; and / or

[0059] - On the hairspring after the end bend is formed; and / or

[0060] - On the hairspring after heat treatment (called oven treatment) following the formation of the end bend.

[0061] In particular, given the very thin thickness of the coating, it can be applied to the finished hairspring ready for assembly without any risk of coloring or altering the limiter and chuck.

[0062] A variety of hydrophobic and / or oleophobic materials can be used to form the second layer, including, for example, fluorinated, perfluorinated, or aliphatic hydrophobic and / or oleophobic molecules. In particular, FDTS (perfluorodecyltrichlorosilane) is very suitable. Alternatively, other materials are possible, such as FOTS (fluorooctyltrichlorosilane), DDMS (dichlorodimethylsilane), PFDA (perfluorodecanoic acid), PFBT (pentafluorobenzenethiol), BTSCE (1,2-bis(trichlorosilyl)ethane), or compounds that allow alkyl / olefin / aliphatic chain grafting, such as octyltrichlorosilane, dodecyltrichlorosilane (DTS), and octadecyltrichlorosilane (OTS). Such steps can be followed, for example, by following the teachings of document EP1927648.

[0063] Furthermore, test results (contact angle and timing measurements on control samples) indicate that the two steps of ALD and SAM deposition can be performed independently before or after oven treatment at 200°C without affecting the hairspring's performance. According to an advantageous embodiment, oven treatment can be performed in the ALD reactor prior to ALD and / or SAM deposition in the same reactor. Therefore, an oven is no longer required. The advantages of this method are that it allows for excellent control of oven treatment conditions and the sequence of operations within the same reactor, saving time and simplifying operations, as well as reducing handling and lowering the risk of hairspring contamination.

[0064] Typically, the minimum deposition temperature for SAM processes is limited to 80°C. Below this temperature, the reaction with the bonding surface becomes too slow. Due to significant degradation of the SAM layer and / or the substrate, the maximum temperature is limited to 300°C.

[0065] The temperature for both stages of ALD and SAM layer deposition was set at 100°C, yielding performance identical to that obtained according to our tests at 80°C (contact angle on silicon between 110-115°). Higher temperatures would also be suitable, with the advantage of accelerating the deposition time of the first primer layer. In the case of depositing the first Al2O3 layer via ALD, an acceptable temperature range is between 30°C and 300°C, preferably between 80°C and 300°C, and more preferably between 80°C and 200°C.

[0066] More generally, it is advantageous to perform the first and / or second steps, along with the optional oven treatment step, at temperatures below 300°C or even below 200°C and / or above 80°C. This low temperature has no effect on the crystal structure of the hairspring.

[0067] The beneficial effects of the surface treatment according to the invention will now be illustrated in certain cases chosen as examples, based on hairsprings made of an Nb-Zr alloy containing 15% element Zr and prepared according to the method described in document EP0886195. These hairsprings are first coated with an anodic oxide layer of approximately 70 nm thickness obtained according to the anodizing principle described in document EP1039352.

[0068] These hairsprings were coated with a first Al2O3 primer layer using ALD technology. For this purpose, they were placed in a vacuum reactor at 100°C for 2 hours before depositing the first ALD layer. They were freely arranged on a grid within the ALD reactor. It should be noted that various tests were conducted by depositing the first Al2O3 layer at higher temperatures (i.e., 80°C, 100°C, and 170°C). No performance differences were observed between the hairsprings obtained at these different temperatures.

[0069] In addition, various tests were conducted by depositing Al2O3 ALD layers at 200°C using water or ozone as co-reactants. No significant performance differences were observed between the hairsprings obtained using these different co-reactants.

[0070] Finally, a second layer was formed by SAM deposition using the chemical reagent perfluorodecyltrichlorosilane or FDTS (CAS 78560-44-8) at a deposition temperature of 100°C and an incubation time of 15 minutes. The operating conditions are summarized in the table below.

[0071] SAM conditions used for testing

[0072]

[0073] In addition, the effect of FDTS incubation time in the reactor during the deposition of the second coating was evaluated. Four batches of 20 shakers were produced.

[0074] Incubation time during SAM deposition was tested by FDTS with and without a first Al2O3 primer layer.

[0075]

[0076] Test results (contact angle on the control sample, but also time-dependent measurements) indicate that the standard incubation time (15 minutes) is sufficient, and a shorter time (5 minutes) is already satisfactory in terms of the effect of the resulting coating. A longer duration (45 minutes) does not provide any significant improvement. The contact angles (water) measured on the silicon control sample with accompanying deposits were 111°, 114°, and 115° for incubation times of 5, 15, and 45 minutes, respectively. Finally, it should be noted that FDTS molecules alone provide poor performance in terms of oscillator stability without the Al2O3 undercoat. Therefore, the first primer layer, in combination with the second layer according to the invention, also achieves the secondary function of stabilizing the oscillator.

[0077] Prior to depositing the coating according to the invention, further tests were conducted on the hairsprings prepared as described above, which were started from Nb-Zr hairsprings coated with an oxide layer of about 70 nm thickness by anodizing. The coating according to the invention comprises a first Al2O3 layer deposited by ALD and a second layer produced by SAM deposition of FDTS.

[0078] It should be noted that a silica reference tile, typically with a 1-2 nm natural oxide layer located near the hairspring to be coated, is used to check the consistency of the deposit. Thickness (elliptic gauge) and contact angle (DSA – droplet shape analyzer) measurements are performed on these hairsprings. The target contact angle (water) is between 100° and 115°.

[0079] Figure 1 The combined effect of two layers of coating according to the invention is shown. The test involved measuring the daily rate M (in seconds per day) of two types of helical springs under variable climatic conditions over a 12-day cycle with time T [days], specifically involving controlled temperature variations of the two types of helical springs. The daily rate M was determined by taking a snapshot of the movement (an image of the position of an indicator such as the second hand) and measuring the cumulative difference between the time displayed by the movement and an external time reference over 24 hours (1 day). The rate change over time, represented by curve 1, is that of a first hairspring anodized according to the prior art, an Nb-Zr alloy hairspring. It serves as a reference hairspring. Curve 2 represents the rate change over time of a second hairspring corresponding to the first hairspring to which the coating according to the invention has been applied, comprising a first Al2O3 layer with a thickness of 10 nm and a second FDTS layer with a thickness of 1 nm. Therefore, Figure 1 The invention reduces the performance change to half of the original value, and curve 2 shows that the change is halved.

[0080] It should be noted that Figure 1Each point on curves 1 and 2 represents the average motion variation of a batch of 20 movements. Each batch undergoes the same cycle of exposure to different climatic conditions, particularly under controlled temperature variations.

[0081] Figure 2 This shows how the thickness of the first Al2O3 layer varies with the [data / data] layer. Figure 1 The maximum motion variation VM within different cycles. Curve 3 more precisely shows the maximum motion variation of a hairspring comprising only a single Al2O3 layer, which is not covered and therefore not part of the invention. Curve 4 represents the maximum step size variation of the same hairspring comprising a second FDTS layer on a first Al2O3 layer according to the invention.

[0082] More specifically, Figure 2 Each point in the table represents the maximum rate variation between different instantaneous rate measurements obtained during cycling in a climate chamber and averaged over a batch of 30 movements comprising helical springs with a given configuration of multiple protective layers. Each batch consisted of three sub-batches of 10 movements, each using hairsprings from three different production batches; measurements showed no significant deviation between the sub-batches. Each batch of 30 movements was cycled for 90 minutes under different conditions (specifically, temperature variations), with instantaneous rate measurements taken at the end of each cycle.

[0083] The maximum rate of change is calculated as the difference between the maximum and minimum values ​​among the individual values ​​measured during the climate cycle.

[0084] therefore, Figure 2 The effects of this invention compared to a helical spring consisting of only a single Al2O3 deposit are shown. This invention provides a very significant improvement for thicknesses of thin Al2O3 layers of approximately 6 nm or even less than 5 nm. Then, according to the tests conducted, it offers a slight advantage in terms of maximum variation in operation for thicknesses up to 10 nm, but naturally also provides the advantage of the hydrophobic properties provided by the FDTS layer.

[0085] therefore, Figure 2 This invention demonstrates the advantage of improving the stability of a hairspring comprising a very thin first layer. This has the advantage of minimal disturbance to the hairspring: changes in stiffness are, for example, roughly proportional to the thickness of the deposit. Therefore, small thicknesses have almost no effect on this stiffness. Naturally, depositing small thicknesses is also faster and less costly.

[0086] exist Figure 1 and Figure 2The reduced rate drift observed in other tests suggests that the combination of the two layers (the layer deposited in the first step and the SAM layer) synergistically forms a new barrier layer that is more effective than expected from a simple combination of the two layers used alone. One hypothesis explaining this surprising effect is that the ALD layer is not perfectly continuous, conformal, and dense, contrary to common belief, especially on rough surfaces and particularly for thin layers. This thinness is advantageous in the context of this invention because it minimizes the influence of the ALD layer on the mechanical properties and performance of the hairspring. Similarly, the SAM layer may not be perfectly continuous and dense, especially on rough surfaces. Therefore, adding a SAM layer on top of the ALD layer enhances its effect, particularly in areas where the ALD layer is not continuous, conformal, and / or dense.

[0087] Finally, the present invention more generally relates to any resilient return component, particularly a helical spring, for an inertial element in a watch movement, wherein the resilient return component includes a substrate on which a coating is deposited, the coating comprising:

[0088] - A first primer layer of oxides, nitrides, or carbides deposited by physical or chemical deposition (ALD, PVD, CVD); and

[0089] - A second layer of hydrophobic and / or oleophobic material deposited via self-assembled monolayer (SAM) deposition.

[0090] As described above, the thickness of the first primer layer is advantageously between 1 nm and 20 nm, or even between 1 nm and 10 nm, or even between 1 nm and 6 nm, or even between 1 nm and 5 nm, or even between 1 nm and 3 nm. Advantageously, the total thickness of the coating of the present invention is less than or equal to 21 nm, or even less than or equal to 20 nm, or even less than or equal to 10 nm, or even less than or equal to 7 nm, or even less than or equal to 6 nm, or even less than or equal to 5 nm.

[0091] As described above, the first primer layer is advantageously made of a single material. Alternatively, it can be a combination of multiple materials and / or consist of multiple stacked sublayers of different materials. Similarly, as described above, the SAM layer is advantageously formed of a single molecule. Alternatively, it can be a combination of multiple molecules and / or consist of multiple stacked sublayers of the same and / or different molecules.

[0092] According to examples of implementation methods, the first primer layer may contain aluminum oxide (Al2O3), titanium dioxide (TiO2), hafnium dioxide (HfO2), zirconium dioxide (ZrO2), niobium pentoxide (Nb2O5), or zinc oxide (ZnO).

[0093] It should also be noted that after the first layer is deposited, the filaments are advantageously kept under vacuum in the same reactor, which ensures optimal cleanliness of the surfaces on which the first layer is coated, thus guaranteeing optimal deposition and coverage of the second layer.

[0094] Furthermore, depending on the implementation example, the hydrophobic and / or oleophobic material of the second layer may comprise fluorinated, perfluorinated, or aliphatic hydrophobic molecules. The fluorinated or perfluorinated hydrophobic molecules may be selected from perfluorodecyltrichlorosilane (FDTS), fluorooctyltrichlorosilane (FOTS), perfluorodecanoic acid (PFDA), and pentafluorobenzenethiol (PFBT). Aliphatic molecules may be selected from octyltrichlorosilane, dodecyltrichlorosilane (DTS), and octadecyltrichlorosilane (OTS). Molecules may also be selected from dichlorodimethylsilane (DDMS) and 1,2-bis(trichlorosilyl)ethane (BTSCE). Molecules may also be selected from aliphatic and / or perfluorinated molecules described in documents EP2084253 and EP2655577, and / or deposited by means other than ALD, such as by impregnation.

[0095] The substrate formed by the component can be: an optional oxidized paramagnetic alloy based on niobium or titanium, such as niobium-zirconium (Nb-Zr) or niobium-titanium (Nb-Ti) alloys; or an optional oxidized ferromagnetic alloy; or monocrystalline or polycrystalline silicon optionally coated with a silicon oxide (SiO2) layer; or glass; or ceramic; or a carbon-containing compound, such as carbon nanotubes or diamond. When the substrate is made of a niobium- or titanium-based paramagnetic alloy, the thickness of the optional anodic oxide layer can be between 5 nm and 200 nm. It forms the surface on which the coating of the present invention will be deposited.

[0096] The elastic return component can be a helical spring with or without a limiter and / or clamp.

[0097] The coating can be deposited on the entire surface of the elastic return component, or only on a portion of it.

[0098] The present invention also relates to a watch oscillator or watch movement comprising the elastic return component as described above.

[0099] The present invention also relates to a clock, particularly a watch, comprising at least one resilient return component as described above.

[0100] Finally, as stated above, the present invention achieves the desired objectives and provides numerous advantages. The following advantages can be mentioned again:

[0101] - It can improve many oscillators almost independently of the base material of the oscillator, so the base material can be selected from a wide range of materials;

[0102] - In addition, the selection of the preferred treatment (ALD / SAM) for coating formation makes it easy to tune the process and deposit the coating with very good reproducibility, especially to achieve the desired thickness in a reliable and uniform manner;

[0103] - The coating is applied at low temperatures without affecting the crystal structure of the hairspring;

[0104] - This uniformity of coating thickness is achieved even on substrates with complex shapes and / or on surfaces with scales and / or cracks and / or roughness.

[0105] - The coating thickness is very small, and its impact on various mechanical properties and overall aesthetics is negligible. For example, it does not cause any color change, while achieving a significant effect of stabilizing the parts over time.

Claims

1. A resilient return member for an inertial element in a watch movement, particularly a helical spring, wherein the resilient return member comprises a substrate on which a coating is deposited, the coating comprising: - A first primer layer of oxide, nitride, or carbide, the thickness of which is between 1 nm and 20 nm; as well as - A second layer of hydrophobic and / or oleophobic material formed by self-assembled monolayers (SAM).

2. The elastic return component according to the preceding claim, wherein, The thickness of the first primer layer is between 1 nm and 10 nm, or between 1 nm and 6 nm, or between 1 nm and 5 nm, or between 1 nm and 3 nm, and / or the thickness of the coating is less than or equal to 10 nm, or less than or equal to 7 nm, or less than or equal to 6 nm, or less than or equal to 5 nm.

3. The elastic return component according to any one of the preceding claims, wherein, The first primer layer is made of a single material, and / or the first primer layer comprises aluminum oxide (Al2O3), titanium dioxide (TiO2), hafnium dioxide (HfO2), zirconium dioxide (ZrO2), niobium pentoxide (Nb2O5), or zinc oxide (ZnO).

4. The elastic return component according to any one of the preceding claims, wherein, The hydrophobic and / or oleophobic material of the second layer includes fluorinated, perfluorinated, or aliphatic hydrophobic molecules.

5. The elastic return component according to claim 4, wherein, The fluorinated, perfluorinated hydrophobic and / or oleophobic molecules are selected from perfluorodecyltrichlorosilane (FDTS), fluorooctyltrichlorosilane (FOTS), perfluorodecanoic acid (PFDA), and pentafluorobenzenethiol (PFBT); or the aliphatic hydrophobic and / or oleophobic molecules are selected from octyltrichlorosilane, dodecyltrichlorosilane (DTS), and octadecyltrichlorosilane (OTS); or the hydrophobic and / or oleophobic molecules are selected from dichlorodimethylsilane (DDMS) and 1,2-bis(trichlorosilyl)ethane (BTSCE).

6. The resilient return component according to any one of the preceding claims, wherein, The substrate is made of the following materials: optionally oxidized paramagnetic alloys based on niobium or titanium, such as niobium-zirconium (Nb-Zr) or niobium-titanium (Nb-Ti) alloys; or optionally oxidized ferromagnetic alloys; or monocrystalline or polycrystalline silicon optionally coated with a silicon oxide (SiO2) layer; or glass; or ceramics; or carbon-containing compounds, such as carbon nanotubes or diamond.

7. The elastic return component according to the preceding claim, wherein, The substrate is made of a paramagnetic alloy based on niobium or titanium and is covered with an anodic oxide layer with a thickness between 5 nm and 200 nm, the anodic oxide layer itself being covered by the coating.

8. The resilient return component according to any one of the preceding claims, wherein, The resilient return component is a helical spring with or without a limiter and / or clamp, and the coating is deposited on the entire surface of the resilient return component.

9. A watch oscillator or watch movement comprising a resilient return element according to any one of the preceding claims.

10. A clock, particularly a watch, comprising at least one resilient return member according to any one of claims 1 to 8.

11. A method for treating the surface of a substrate of an elastic return member for an inertial element in a watch movement, the elastic return member being, in particular, a helical spring, wherein the method comprises depositing a coating on the surface of the substrate by means of the following steps: - A first step of depositing a first primer layer of oxides, nitrides, or carbides by atomic layer deposition (ALD), physical vapor deposition (PVD), or chemical vapor deposition (CVD), wherein the thickness of the first primer layer is between 1 and 20 nm; and - A second step to deposit hydrophobic and / or oleophobic materials via self-assembled monolayers (SAM).

12. The processing method according to claim 11, wherein, The processing method includes the step of oxidizing the elastic return component, particularly by anodizing, which is performed before the first deposition step, and / or the processing method includes an oven treatment step of the elastic return component, which is performed before the first deposition step or after the second deposition step.

13. The processing method according to any one of claims 11 and 12, wherein, The first step, the second step, and the optional oven treatment step are carried out continuously in the same chamber, particularly at the same temperature.

14. The processing method according to any one of claims 11 to 13, wherein, The first and second steps are performed at temperatures below 300°C or even below 200°C and / or at temperatures above 80°C.

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