watch parts

Abstract

To provide a horology component that does not produce a large amount of scattered debris when it breaks.SOLUTION: A horology component based on a fragile material is provided, the component comprising at least one surface part of the fragile material covered with a coating (10) comprising at least two layers CE of an elastic material (11) separated by a layer CR of a material (12) stronger than the elastic material (11).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a timepiece part made of brittle material, in particular silicon. The invention also relates to a timepiece movement and a timepiece, in particular a wristwatch, comprising at least one such timepiece part. [Background technology]

[0002] Silicon is a material that offers numerous advantages in the manufacture of watch components. On the one hand, silicon allows for the simultaneous production of numerous miniature parts with micrometer-level precision. On the other hand, silicon has low density and diamagnetic properties. However, this material also has the following drawbacks: Silicon has little or no plastic deformation zone, making it relatively brittle in nature. Mechanical stress or impact can damage the components. The fragility of silicon watch components is accentuated by the fact that these components are typically cut from silicon substrates using deep etching techniques, such as deep reactive ion etching (DRIE). A characteristic of this type of etching is that, while the openings are formed, their sides are lightly grooved, resulting in a lack of flatness due to ripples known as "scalloping." This means that the etched sides have a certain degree of roughness, which reduces the mechanical strength of the component. Furthermore, the lack of flatness can lead to cracks, especially when subjected to mechanical stress, potentially resulting in component failure. If a silicon part breaks within a watch movement, not only will the watch movement no longer function, but large amounts of silicon debris from the broken watch part will be scattered throughout the watch movement. Summary of the Invention [Problem to be solved by the invention]

[0003] The object of the present invention is to propose a timepiece component that does not have the drawbacks of the prior art.

[0004] More specifically, a first object of the present invention is to propose a watch component that does not generate a large amount of scattered fragments when broken. [Means for solving the problem]

[0005] For this reason, the invention relates to a watch part based on brittle material, said part comprising a layer C of material stronger than the elastic material. R The invention relies on a watch component comprising at least one surface portion of a brittle material coated with a coating, the coating comprising at least two layers of said elastic material separated by a

[0006] The invention is more particularly defined in the claims.

[0007] The objects, features and advantages of the present invention will be illustrated in detail in the following description of specific embodiments, given by way of non-limiting example in connection with the accompanying drawings. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a schematic cross section of a timepiece component according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing a schematic cross section of a timepiece component according to a second embodiment of the present invention. [Figure 3] FIG. 3 is a close-up photograph of a test piece made of a brittle material and coated with a coating according to an embodiment of the present invention, taken at the moment of failure. [Figure 4] FIG. 4 is an enlarged photograph of a specimen made of a brittle material similar to that of FIG. 3 but without the coating according to this embodiment, taken at the moment of failure. [Figure 5] FIG. 5 shows the strengths obtained for different batches of watch components, demonstrating the positive results obtained with the implementation of an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] As mentioned above, the present invention particularly relates to timepiece components based on brittle materials, i.e., materials that tend to break and generate large amounts of debris that detach from the timepiece component and spread throughout the timepiece movement. By brittle material, we mean a non-ductile material that breaks without prior or residual plastic deformation. Such materials are preferably micromachinable, i.e., obtained by micromanufacturing techniques, including photolithography. The present invention is particularly suited to all forms of silicon, such as doped or porous silicon, but may alternatively be adapted to other materials, such as diamond, quartz, glass, silicon carbide, alumina- or zirconia-based ceramics, brittle amorphous metals, or sapphire. Such timepiece components may be entirely or almost entirely made of the brittle or brittle material, except for the fine coating described below. Alternatively, the timepiece component may be based on such a material, i.e., contain at least 51% by weight of the material, or at least 80% by weight of the component. Thus, they may be hybrid materials with a brittle or brittle effect. In a broader sense, the term "brittle material" is used herein to mean the entire core of a watch component, even if parts of the core are not directly made of the brittle material on which the watch component is based.

[0010] The concept of the present invention is to cover at least a portion of the surface of a watch component, preferably the surface subject to the greatest stress in the traction zone of the watch component, with a multi-layer coating comprising at least two layers of elastic material separated by a layer of material stronger than the elastic material. The coating forms a protective layer on the watch component to hold together the various fragments and prevent them from scattering in the event of breakage of the component. A coating is considered to encapsulate a watch component if it extends over substantially the entire circumference of the watch component or over the zones subject to stress due to deformation.

[0011] FIG. 1 shows a schematic diagram of a watch component 1 according to a first embodiment of the invention. The watch component 1 comprises a main body or core 2 made of silicon, resulting for example from a cutting step from a silicon wafer. The watch component 1 further comprises a coating 10 extending over its entire outer surface, more particularly over the periphery of its core 2. According to an advantageous manufacturing method, which will be explained in more detail below, this outer surface is formed by cutting the wafer and comprises three main surfaces: a first surface 3, which is substantially planar and corresponds to the upper surface of the cut wafer; an opposite second surface 4, which is substantially planar and parallel to the first surface 3, and corresponds to the lower surface of the cut wafer; and finally, a third surface 5, which forms a side surface continuously connecting the two aforementioned surfaces 3, 4.

[0012] The coating 10 comprises a first layer C made of elastic material, which is in contact with the silicon core 2 of the watch part 1. E The coating 10 is a multi-layer coating including a third outer layer C made of the same elastic material 11. E These two layers are joined by a second layer C made of a stronger material 12. R In the first embodiment, layer C E is made of Parylene, and layer C R is made of aluminum oxide deposited using ALD.

[0013] FIG. 2 shows the intermediate layer C of the coating, made of silicon oxide, a high strength material 12. R 1 illustrates a second embodiment of the present invention, which differs from the first embodiment in that it has a variable thickness at the side 5. The intermediate layer further has a constant thickness at the first and second surfaces 3, 4, the thickness being greater at the first surface 3 than at the second surface 4. Two layers C of elastic material 11 are E The intermediate layer is completed to form a coating of uniform thickness as a whole. E is made of Parylene, and layer C R is silicon oxide deposited using PVD.

[0014] 1 and 2, the thickness of the coating 10 is not drawn to scale. It has been greatly exaggerated to better visualize the coating, which is actually very fine. This thickness E tends to vary within a certain range. In general, the coating 10 comprises at least one layer C of elastic material 11 having a thickness of 0.05 μm or more, or 0.3 μm or more. E The coating 10 also advantageously comprises at least one layer C of elastic material 11 having a thickness of 5 μm or less, or 3 μm or less. E Finally, various layers C of elastic material of the coating 10 E The sum of the thicknesses of the various layers C of elastic material 11 is advantageously greater than or equal to 0.1 μm, or 0.6 μm, and / or less than or equal to 20 μm, or less than or equal to 12 μm. E Note that the thicknesses may or may not be the same. The thickness may or may not be variable.

[0015] Furthermore, the layer C of the high strength material 12 of the coating 10 R has a thickness of 15 nm or more, or 30 nm or more. The coating 10 also advantageously includes a layer of high strength material 12 having a thickness of 150 nm or less, or 100 nm or less, or 70 nm or less. Finally, the various layers C of high strength material 12 R The total thickness of the first and second electrodes is 15 nm or more, or 30 nm or more, and / or 450 nm or less, or 300 nm or less, or 210 nm or less.

[0016] To complement this, the material of the coating 10 may be different from that used in the above-described embodiments. In any case, the elastic material 11 has an elastic modulus of 10 GPa or less, or 5 GPa or less, or 3 GPa or less. Alternatively or additionally, the elastic material 11 has a breaking elongation of 10% or more, or 20% or more, or 30% or more. The elastic material 11 is parylene, or alternatively, PTFE, acrylic, silicone, or a polymer of the urethane family. The various layers of elastic material 11 in the same coating 10 may be made of the same elastic material or different elastic materials.

[0017] Furthermore, the high-strength material 12 is referred to as being "stronger" than the strength of a material referred to as "elastic." The high-strength material 12 has an elastic modulus of 30 GPa or more, or 45 GPa or more, or 60 GPa or more. Alternatively, the high-strength material 12 has an elastic modulus between the elastic modulus of the brittle material of the core of the watch component and the elastic material of the elastic layer. The high-strength material advantageously has an elastic modulus that is 50% or more greater than the elastic modulus of the adjacent layer of elastic material 11. Thus, the present invention is applicable to any pair of comparatively "elastic" and "strong" materials, where the "elastic" and "strong" materials are defined by the difference in their elastic moduli, and the high-strength material has an elastic modulus that is 50% or more greater than the elastic modulus of the elastic material of at least one adjacent layer. The high-strength material 12 may be a metal, alloy, graphite, or oxide, more specifically, silicon oxide or silicon nitride. The various layers of high-strength material 12 in the same coating 10 may be made of the same or different materials.

[0018] Of course, the invention is not limited to the above-described embodiment. Thus, the coating 10 may include a number of layers other than the three shown. For example, it may include at least two, or at least three, or four layers of elastic material 11 and at least one, or at least two, or three layers of high-strength material 12. To limit the impact on the dimensions and properties of the component, the coating advantageously includes a maximum of four layers of elastic material 11 and a maximum of three layers of high-strength material 12, although more layers are possible. The coating advantageously includes alternating layers of elastic material 11 and high-strength material 12. Even more advantageously, the coating includes a first inner layer of elastic material 11 and a last outer layer of elastic material 11. The adjectives "inner" and "outer" are used in any direction from the core 2 of the watch component 1 toward the outside of the watch component 1.

[0019] The invention is particularly useful in the case of a timepiece component 1 selected from toothed wheels, escape wheels, hands, impulse jewels, anchors, levers, pallet jewels, leaf springs such as spiral springs, systems including flexible blades, or other components with a spring function.

[0020] Figures 3 and 4 illustrate the specific effect of a layer of elastic material 11 on a silicon watch part 1. Figure 3 illustrates the breakage of a silicon test piece coated with a coating according to the second embodiment, as illustrated in Figure 2. For comparison, Figure 4 illustrates the breakage of the same silicon oxide test piece without a coating. As can be seen in Figure 4, a large amount of debris 22 is scattered. On the other hand, the same test piece coated with a layer according to the second embodiment is able to prevent debris from scattering, as shown in Figure 3. The first advantage of using several Parylene layers is that the effectiveness of the coating is more reliable. If one layer is damaged, the other layers theoretically guarantee its effectiveness. Furthermore, at least one Parylene layer is not in direct contact with the outside world and is protected from potential external attacks by at least one high-strength layer of the coating.

[0021] Comparative bending tests were carried out on silicon test pieces obtained by DRIE cutting from silicon wafers, using methods known to those skilled in the art. It should be noted that due to the fragile nature of the material, the same treatment applied to the same test piece will produce different results from one identical watch component to another, theoretically subjected to the same stress load. Therefore, to determine whether there is an effect, it is necessary to carry out tests on several batches of the same test piece, followed by a statistical analysis.

[0022] The results obtained from six different batches of specimens are shown in Figure 5. The flexural strength of each part (specimen) from each batch was measured, as shown on the vertical axis. The figure shows, among other things, the average, minimum, and maximum breaking strength for each batch.

[0023] The first two batches, OXY1 and OXY3, consisted of 30 silicon oxide specimens with a 1 μm and 3 μm thick silicon oxide layer on the surface, respectively. The average bending strength of these two batches was approximately 2000 MPa. Furthermore, upon failure, all of these specimens produced a large amount of scattered debris.

[0024] The next two batches correspond to specimens similar to batch OXY3, but coated with a uniform coating of a pure monolayer of Parylene, with thicknesses of 0.5 μm and 5 μm, respectively. Surprisingly, the addition of a coating of such a low-strength elastic material made it possible to significantly increase the fracture strength of the specimens. In particular, the average strength was approximately 5000 MPa.

[0025] The fifth batch corresponds to silicon specimens coated with a metallic coating consisting of a 15 nm thick titanium bonding layer and an 80 nm thick gold layer. This robust coating provides a slight increase in average strength compared to the first two batches, but is significantly weaker than the two batches with parylene coatings. Furthermore, this coating does not retain the fragments when the specimen breaks.

[0026] Finally, the final batch corresponds to the second embodiment of the present invention and includes a coating consisting of four layers of approximately 1 μm of Parylene alternating with three intermediate layers of silicon dioxide, each 0.01 μm thick, for a total coating thickness varying between 3.7 and 4.7 μm. The average strength of the batch appears to be greater than 6000 MPa, with a minimum value greater than 4000 MPa. The present invention thus optimizes the strength of watch components. The present invention thus relates to watch components having an average strength of 6000 MPa or greater, and / or a minimum strength of 3000 MPa or greater, or 4000 MPa or greater. Furthermore, the present invention prevents the scattering of debris.

[0027] Finally, a coating that combines a flexible material (elastic material as defined above) with a strong material (also defined above) appears to make it possible to utilize the synergistic effect between the two materials, not only addressing the technical problem of preventing scattering of fragments in the event of breakage, the effective protective effect offered by the elastic material, but also making it possible to simultaneously optimize the strength of the watch component, in particular by the addition of a material that is stronger than the elastic material within the thickness of the coating 10. This highly advantageous property is unexpected and surprising.

[0028] The invention also relates to a timepiece movement as such, and to a timepiece as such, which includes one or more of the timepiece components described above.

[0029] The method for manufacturing a watch component according to the present invention includes a first step of producing a rough mold of the watch component in a known manner. For example, this first step may involve the initial step of obtaining a substrate made of a brittle, micro-machinable material. The substrate is, for example, a silicon wafer. In a subsequent step, the wafer is coated, in particular on at least one of its two faces, referred to as the top and bottom faces, with a protective coating, for example, a photosensitive resin. The method continues with a step of forming a pattern in the protective coating. This pattern is produced by creating openings through the layer of photosensitive resin. The protective coating forming the openings constitutes a protective mask. Etching the silicon wafer through the protective mask, in particular by deep reactive ion etching (DRIE), allows for the production of openings in the silicon along the opening or openings in the mask, thereby obtaining a rough mold of the watch component made of silicon. Alternatively, the rough mold of the watch component may be produced by any method different from the above, for example by using laser cutting techniques. The resulting rough mold forms the core 2 of the watch component 1. The rough mold has a shape that approximates the shape of the final watch part.

[0030] The invention also relates to a second stage of manufacture, which consists in depositing the above-mentioned coating on all or part of the surface of the rough mold.

[0031] The step of depositing the coating is carried out by depositing alternating layers of resilient material and high strength material, respectively.

[0032] The deposition step may be carried out uniformly by evaporation, CVD or ALD. Alternatively, the deposition step may be carried out using a directional technique, such as physical vapor deposition, abbreviated as PVD, or plasma-enhanced chemical vapor deposition, abbreviated as PECVD. In this case, the coating flux is directed towards the first surface 3 perpendicularly. Such a directional method makes it possible to reach the second embodiment of FIG. 2.

[0033] The manufacturing method may include an intermediate step consisting of thermal oxidation and / or smoothing of the rough surface of the watch component prior to the step of depositing the coating, so that the core 2 of the watch component may be coated with an oxidation layer, for example of silicon oxide, prior to the deposition of the coating according to the invention. [Explanation of symbols]

[0034] 1. Watch parts 2 cores 3 1st surface 4 Second surface 5 Third surface 10 Coating 11 Elastic materials 12 High-strength materials

Claims

1. A watch component based on brittle materials, The watch component comprises at least one surface portion of a brittle material coated with a coating (10) comprising at least two layers CE of elastic material (11) separated by layers CR of a material (12) stronger than said elastic material (11), said stronger material (12) having an elastic modulus at least 50% greater than the elastic modulus of the adjacent layer made of elastic material (11); The elastic material (11) of the two layers CE has an elastic modulus of 10 GPa or less, or 5 GPa or less, or 3 GPa or less, and / or the elastic material (11) of the two layers CE has a breaking elongation of 10% or more, or 20% or more, or 30% or more. Watch parts.

2. said coating comprises at least one layer CE made of an elastic material (11) such as parylene or PTFE, acrylic, silicone or a polymer of the urethane family; The watch component according to claim 1.

3. A watch component based on brittle materials, The watch component comprises at least one surface portion of a brittle material coated with a coating (10) comprising at least two layers CE of elastic material (11) separated by layers CR of a material (12) stronger than said elastic material (11), said stronger material (12) having an elastic modulus at least 50% greater than the elastic modulus of the adjacent layer made of elastic material (11); said coating comprises at least one layer CE made of an elastic material (11) such as parylene or PTFE, acrylic, silicone or a polymer of the urethane family; Watch parts.

4. The watch component has an average bending fracture strength of 6000 MPa or more, and / or the watch component has a minimum bending fracture strength of 3000 MPa or more. The timepiece component according to any one of claims 1 to 3.

5. A watch component based on brittle materials, The watch component comprises at least one surface portion of a brittle material coated with a coating (10) comprising at least two layers CE of elastic material (11) separated by layers CR of a material (12) stronger than said elastic material (11), said stronger material (12) having an elastic modulus at least 50% greater than the elastic modulus of the adjacent layer made of elastic material (11); The watch component has an average bending fracture strength of 6000 MPa or more, and / or the watch component has a minimum bending fracture strength of 3000 MPa or more. Watch parts.

6. The elastic materials (11) of the two layers CE are the same or different materials; The timepiece component according to any one of claims 1 to 5.

7. The coating has a thickness of 0.05 μm or more, or 0.3 μm or more, and / or at least one layer CE of elastic material (11) of less than or equal to 5 μm, or less than or equal to 3 μm, and / or the sum of the thicknesses of the various layers CE of the elastic material (11) of the coating is greater than or equal to 0.1 μm, or greater than or equal to 0.6 μm, and / or less than or equal to 20 μm, or less than or equal to 12 μm; A timepiece component according to any one of claims 1 to 6.

8. The high strength material (12) has an elastic modulus of 30 GPa or more, or 45 GPa or more, or 60 GPa or more, and / or has an elastic modulus between the elastic modulus of the adjacent layer of elastic material and the elastic modulus of the brittle material. A timepiece component according to any one of claims 1 to 7.

9. The high strength material is a metal, an alloy, an oxide, or a nitride. A timepiece component according to any one of claims 1 to 8.

10. the layer CR of high strength material (12) has a thickness of 15 nm or more, or 30 nm or more, and / or 150 nm or less, or 100 nm or less, or 70 nm or less; and / or the total thickness of the layer or layers CR of the high strength material (12) of the coating (10) is 15 nm or more, or 30 nm or more, and / or 450 nm or less, or 300 nm or less, or 210 nm or less; A timepiece component according to any one of claims 1 to 9.

11. The coating (10) extends over the entire surface of the periphery of the brittle material; and / or Each layer of elastic material (11) has a constant or variable thickness, and / or The layer of high strength material (12) has a constant or variable thickness, and / or It comprises alternating layers CE of elastic material (11) and layers CR of high strength material (12), and teeth and / or comprising at least two, three, or four layers of elastic material (11) and at least one, two, or three layers of high strength layer (12); comprising a first inner layer of elastic material (11) and a last outer layer of elastic material (11); The present invention has all or some of the above features. A timepiece component according to any one of claims 1 to 10.

12. the brittle material is silicon, oxide-coated silicon, quartz, glass, silicon carbide, alumina- or zirconia-based ceramics, or diamond, sapphire, or a brittle amorphous metal; A timepiece component according to any one of claims 1 to 11.

13. the timepiece part is one of the elements from the group including toothed wheels, escape wheels, hands, impulse jewels, anchors, levers, pallet stones, leaf springs such as spiral springs, flexible blade systems or other parts with a spring function, A timepiece component according to any one of claims 1 to 12.

14. A timepiece movement, said timepiece movement comprising a timepiece component according to any one of claims 1 to 13.

15. A timepiece, the timepiece comprising a timepiece component according to any one of claims 1 to 13 or a timepiece movement according to claim 14.

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