Method for changing the surface condition of a component by ion bombardment

Abstract

The present invention relates to a method for plasma treating a target surface of a component, comprising the following steps: - obtaining a target surface on the component, - placing the component in a chamber of a plasma generator, - evacuating the chamber to a pressure of between 10 ‑6 and 10 mbar, - injecting a suitable gas into the chamber until the pressure in the chamber reaches between 10 ‑4 and 10 2 mbar, - generating an electric current discharge in the chamber via an electric generator to generate a plasma, - exposing the target surface of the component to the plasma for a predetermined time, depending on the power of the electric current discharge, the gas injected into the chamber and the material of the target surface, thereby deteriorating the surface condition of the target surface in order to increase its roughness to matte or more matte the target surface.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of surface treatment, in particular to a method for modifying the surface condition of a component by ion bombardment. BACKGROUND

[0002] In some applications, in particular in the case of exterior components, it is desirable to obtain a visible surface having a matt (i.e. non-shiny) appearance for aesthetic reasons.

[0003] In other words, it is desirable to mattify the surface of certain exterior components, i.e. to increase their degree of mattification.

[0004] Generally, the matt appearance of a surface of a component is obtained by increasing the roughness of the component. More specifically, the shininess of a surface depends on the extent to which it reflects light radiation. In particular, a surface having a shiny appearance specularly reflects light rays, whereas a surface having a matt appearance diffusely reflects light rays.

[0005] In order to mattify the surface of a component, known solutions consist in projecting abrasive particles onto the surface at a defined pressure and over a given period of time, the particle size of the abrasive particles varying according to the desired result. The abrasive particles can be beads made of glass, ceramic or alumina, etc.

[0006] However, the drawback of these solutions is that the abrasives are easily worn and require special waste treatment after use. This is because the abrasive particles are contaminated with particles of the material from the component whose surface is to be mattified as a result of its use. Furthermore, there is a significant risk of variation in the particle size of the abrasive particles. Finally, depending on the thickness of the component, the projected particles can cause irreversible damage or deformation.

[0007] In other cases, it is possible to modify the material properties of the whole or part of the component in order to mattify its surface. In particular, in the case where the surface to be mattified is that of a varnish coating deposited on the component, it is possible to add a suitable resin or additive to the varnish composition.

[0008] However, this solution is limited because it is only applicable in the presence of a varnish coating surface. Furthermore, with the change in its composition, the varnish coating can no longer meet certain requirements, such as being able to withstand mechanical or chemical stresses, being able to withstand a certain degree of temperature, or being able to withstand exposure to ultraviolet radiation, etc. Another drawback of this solution is that it adds an additional step to the production of exterior components, which involves modifying the composition of the varnish, which is particularly restrictive when it is necessary to produce such components on an industrial scale. SUMMARY

[0009] The present invention overcomes the above-mentioned disadvantages by providing a solution for matting a target surface (i.e. increasing its matteness) without generating oxides or any coating on the surface.

[0010] In other words, this invention only allows changing the surface conditions / conditions of the target surface to make it matte.

[0011] Therefore, the present invention relates to a method for plasma treatment of a target surface of a component, comprising the following steps:

[0012] - Obtaining a target surface on a component, including the operation of depositing a varnish coating on a dedicated area of ​​the target surface and the operation of pre-crosslinking at least a portion of the varnish coating by exposing at least a portion of the target surface to ultraviolet radiation;

[0013] - Place the component into the chamber of the plasma generator.

[0014] - Evacuate the chamber to 10°C -6 The pressure between 10 mbar and 10 mbar

[0015] - Inject the appropriate gas into the chamber until the pressure in the chamber reaches 10. -4 and 10 2 Between mbar,

[0016] - A current discharge is generated within the chamber via an electric generator to produce plasma.

[0017] - Depending on the power of the current discharge, the gas injected into the chamber, and the material of the target surface, the target surface of the component is exposed to plasma for a predetermined period of time, thereby changing the surface condition of the target surface to increase its roughness to make the target surface matte or more matte. Even if it is matte, the step of exposing the target surface of the component to plasma is performed to complete the crosslinking of part of the pre-crosslinked varnish coating.

[0018] In certain embodiments, the invention may also include one or more of the following features, viewed individually or in any technically feasible combination.

[0019] In a specific implementation, the target surface is exposed to ultraviolet radiation for 5 to 10 seconds during the pre-crosslinking process.

[0020] In a particular implementation, the chamber is evacuated to a pressure between 0.1 and 1 mbar.

[0021] In a particular embodiment, argon gas is injected during the gas injection step. The gas is injected into the chamber at a mass flow rate between 15 and 25 sccm until the pressure in the chamber reaches between 0.6 and 0.8 mbar.

[0022] Advantageously, choosing argon as the plasma-generating gas means that the target surface is only affected mechanically. In other words, the plasma does not chemically degrade the surface condition of the target surface.

[0023] In a particular implementation, the electric generator produces power between 2,000W and 2,600W during the step of generating a current discharge and performs the step of exposing the target surface for 1 to 2 minutes.

[0024] In a specific implementation, the gloss unit of the varnish coating measured at 60° is less than 5 GU.

[0025] In a particular implementation, at the end of the step of obtaining the target surface on the component, a step of depositing a masking layer is performed on a portion of the target surface referred to as the “masking region”, the remaining portion of the target surface referred to as the “exposed region”, the masking layer being designed to protect the masking region from the effects of plasma.

[0026] In a particular embodiment, during the pre-crosslinking operation of the varnish coating, only a portion of the coating is pre-crosslinked, while another portion is fully crosslinked. Attached Figure Description

[0027] Other features and advantages of the invention will become apparent after reading the following detailed description, given by way of non-limiting example, with reference to the accompanying drawings:

[0028] - Figures 1 to 4 Different sequential steps of a method for plasma treatment of a target surface of a component according to a preferred embodiment of the present invention are illustrated schematically.

[0029] - Figure 5 A cross-sectional view is schematically shown of an alternative to a preferred exemplary embodiment of the method according to the invention, illustrating the step of exposing a target surface of a component to plasma;

[0030] - Figure 6 A cross-sectional view is schematically shown of the step of exposing the target surface of a component to plasma according to another exemplary embodiment of the method according to the invention.

[0031] It should be noted that, for clarity, the accompanying drawings are not drawn to scale. Detailed Implementation

[0032] Figures 1 to 4 Different sequential steps of a method for plasma treatment of a target surface 11 of a component 10 according to a preferred embodiment of the invention are illustrated schematically.

[0033] The method according to the invention aims to make the target surface 11 matte.

[0034] The method includes the preliminary step of obtaining the target surface 11 on the component 10.

[0035] This initial step may include operations involving depositing coatings (such as electroplating), placing inlays, printing decorations, or washing.

[0036] Figure 1 The component 10 is shown schematically, which includes an inlay 12 designed to receive a varnish coating 13.

[0037] In a preferred embodiment of the invention, during this first step, an operation is performed to deposit a clear varnish coating 13 on a designated area of ​​the outer surface of the component 10, such as... Figure 2 As shown. More specifically, the dedicated area may be formed on the inlay 12 pre-placed on the outer surface of the component and / or directly formed on the outer surface of the component 10, such as... Figures 2 to 5 As shown.

[0038] Still in this preliminary step, this operation of depositing the varnish coating 13 is followed by an operation of pre-crosslinking the varnish coating 13 by exposing it to ultraviolet radiation, as... Figure 3 As shown. In this exemplary embodiment of the invention, the target surface 11 is the visible surface of the varnish coating 13.

[0039] The varnish coating 13 can be deposited manually by an operator or automatically by a suitable robot. Furthermore, the varnish coating 13 may include synthetic resins, acrylic resins, polyurethane resins, or epoxy resins, or luminescent materials, etc.

[0040] During the pre-crosslinking process of the varnish coating 13, the target surface 11 may be exposed to ultraviolet radiation for a few seconds or tens of seconds, preferably between 5 and 10 seconds.

[0041] Ultraviolet radiation can be emitted in any manner known to those skilled in the art, such as light-emitting diodes or mercury lamps, with wavelengths between 100 and 400 nm.

[0042] Once the target surface 11 has been obtained, component 10 is placed in the chamber of plasma generator 20, such as... Figure 4 As shown. Specifically, component 10 is placed directly or via a substrate on the electrode of the electric generator of plasma generator 20. Preferably, component 10 is placed on the negative electrode of plasma generator 20, facing the positive electrode.

[0043] The method according to the invention then includes the step of evacuating / vacuuming the chamber using a vacuum pump known to those skilled in the art. The term "vacuuming" herein is understood, for linguistic simplicity, to mean placing the chamber under a low pressure, typically 10... -6 The pressure is between 10 mbar and 10 mbar, and preferably between 0.1 mbar and 1 mbar.

[0044] Then, the gas injection step is performed until the gas level in the chamber reaches 10. -4 mbar and 10 2 The working pressure is between mbar, and preferably between 0.6 mbar and 0.8 mbar.

[0045] For example, gas is injected at a mass flow rate between 15 and 25 sccm until the chamber reaches the working pressure.

[0046] The step of generating a current discharge within the chamber is performed via an electric generator to generate plasma within the chamber. The plasma flow is advantageously directed toward component 10 to induce ion bombardment on the target surface 11, such as... Figure 4 As shown schematically. In particular, the potential difference between the electrodes of the electric generator causes gas atoms to be ionized and bombard the target surface 11 of the component 10.

[0047] The gas suitable for implementing the method according to the invention may be selected from Ar, He, O2, CO, CO2, H2, Cl2, CF4, Ne, N2, and NO2. Ar is the preferred gas because it is easily ionized, allowing plasma to be generated with reduced electrical input. Furthermore, the effect of the plasma on the target surface 11 is more important when using Ar, as the plasma is particularly suitable for altering the surface condition of the target surface 11 and crosslinking the optional varnish coating 13 deposited on the component 10. Finally, Ar has the advantages of being inexpensive and readily available.

[0048] Specifically, depending on the power of the current discharge, the gas in the injection chamber, and the material of the target surface 11, the target surface 11 is exposed to plasma for a predetermined period of time, thereby altering the surface condition of the target surface 11 to increase its roughness and thus its matte finish. In this invention, the exposure of the target surface 11 to plasma, particularly ion bombardment, has the effect of altering the surface condition of the target surface 11 through mechanical or physicochemical action, depending on the gas injected into the chamber.

[0049] In a preferred embodiment of the invention, the step of exposing the target surface 11 of the component 10 to plasma is performed to complete the crosslinking of the varnish coating 13.

[0050] For example, in the step of generating a current discharge, the electric generator can produce power between 2000W and 2600W, and can expose the target surface 11 for 1 to 2 minutes.

[0051] For example, after implementing this method, the gloss of the varnish coating 13 measured at 60° (measurement angle) is less than 5 GU. In other words, the above parameters have been specifically determined by the inventors so that the target surface 11 of the varnish coating 13 has such a gloss unit.

[0052] One advantage of this invention is that when component 10 is exposed to plasma, it allows the varnish coating 13 to be cross-linked while simultaneously matting the target surface 11. Therefore, in addition to significantly reducing production time by avoiding the need for subsequent cross-linking steps, this invention also reduces the time spent exposed to ultraviolet radiation, thus limiting the risks associated with the use of ultraviolet radiation.

[0053] According to any exemplary embodiment of the invention under consideration, the invention also allows for increasing the matteness of any surface, regardless of its surface condition, such as even if it has cavities of submicron or micron size.

[0054] Advantageously, at the end of the step of obtaining the target surface 11 on the component 10, a step of depositing a masking layer can be performed on a portion of the target surface 11 referred to as the “masking region”, the remaining portion of the target surface 11 referred to as the “exposed region”. The masking layer is designed to protect the masking region from the effects of plasma to obtain the component 10 with two different gloss levels on its target surface 11.

[0055] The step of depositing the masking layer can therefore be used to obtain a component 10 with both gloss and matte finish on its target surface 11.

[0056] The masking layer can be produced by polymer coating, electroplating coating or coating made by physical vapor deposition.

[0057] After the step of exposing the target surface 11 to plasma, the masking layer can be removed by a solution suitable for the properties of the deposited coating. For example, if the masking layer is made of a polymer material, it can be removed with a suitable solvent; if it is made of a metallic material, it can be removed with an acidic solution, etc.

[0058] If necessary, the portion of the varnish coating 13 protected by the masking layer can be crosslinked in a subsequent crosslinking step.

[0059] In a preferred embodiment of the invention, during the pre-crosslinking operation of the varnish coating 13, only a portion of the varnish coating 13 may be pre-crosslinked, thus allowing the other portion to be fully crosslinked. Since the fully crosslinked portion of the varnish coating 13 is not plasma crosslinked, its surface condition remains unchanged or changes in a manner imperceptible to the naked eye, such as... Figure 5 As shown schematically in the diagram.

[0060] This feature allows for the acquisition of components 10 with target surfaces 11 having different gloss levels, as an alternative to masking layer deposition.

[0061] exist Figure 6 In an exemplary embodiment illustrated schematically, with Figures 1 to 4 In contrast to the exemplary embodiment shown, the target surface 11 is formed by the surface of the component 10 or by the surface of the coating of the component 10. In other words, in this exemplary embodiment of the invention, the surface to be matted is the surface of the component 10 or the surface of the coating of the component 10, rather than the surface of the varnish 13 deposited on the component 10.

[0062] Such exemplary embodiments are particularly suitable when the target surface 11 is the surface of a component made of a metal alloy such as a copper alloy, iron alloy, aluminum alloy, or titanium alloy, a ceramic material or composite material such as a metallic material bonded with oxides, nitrites, or silicates, or a polymer material. This exemplary embodiment of the invention is also particularly suitable when the target surface 11 is the surface of a coating of component 10 such as gold, silver, nickel, copper, rhodium, ruthenium, or silver.

[0063] Depending on the material of component 10 or the material of the coating of component 10 having target surface 11, the parameter values ​​of the method according to the invention can vary. For example, the gas mass flow rate injected into the chamber can be up to 1,000 sccm, the power of the electric generator can be up to 4 kW, and the duration of plasma exposure can be between a few seconds and a few minutes, for example, between 5 seconds and 10 minutes.

[0064] This invention is advantageously applicable to the field of watchmaking, particularly when component 10 is an external component 10 of a watch (e.g., a dial).

[0065] More generally, it should be noted that the implementation methods and embodiments considered above have been described by way of non-limiting example, and other variations are therefore possible.

Claims

1. A treatment method for plasma treating a target surface (11) of a component (10), comprising the steps of: - obtaining said target surface (11) on said component (10), comprising an operation of depositing a varnish coating (13) on a dedicated area of said target surface (11) and a pre-crosslinking operation of pre-crosslinking at least a portion of said varnish coating (13) by exposing at least a portion of said target surface (11) to ultraviolet radiation; - placing said component (10) in a chamber of a plasma generator (20), - evacuating the chamber to a pressure of between 10 -6 and 10 mbar, - injecting a suitable gas into the chamber until the pressure in the chamber reaches between 10 -4 mbar and 10 2 mbar, - generating an electric current discharge in said chamber via an electric generator to generate a plasma, - exposing said target surface (11) of said component (10) to plasma for a predetermined time, according to at least the power of the electric current discharge, the gas injected into said chamber and the material of said target surface (11), so as to deteriorate the surface condition of said target surface (11) to increase its roughness, so as to matte said target surface (11), the step of exposing said target surface (11) of said component (10) to plasma being performed to complete the crosslinking of said portion of pre-crosslinked varnish coating (13).

2. The treatment method of claim 1, wherein, During said pre-crosslinking operation, said target surface (11) is exposed to ultraviolet radiation for 5 to 10 seconds.

3. The treatment method according to claim 1 or 2, wherein, Said chamber is evacuated to a pressure of between 0.1 mbar and 1 mbar.

4. The treatment method according to any one of claims 1 to 3, wherein, During the gas injection step, argon is injected into said chamber at a mass flow of between 15 seem and 25 seem until the pressure in said chamber reaches between 0.6 mbar and 0.8 mbar.

5. The treatment method of claim 4, wherein, During the step of generating an electric current discharge, said electric generator generates a power of between 2000 W and 2600 W and the step of exposing said target surface (11) is performed for 1 to 2 minutes.

6. The treatment method according to any one of claims 1 to 5, wherein, The varnish coating (13) has a gloss measured at 60° of less than 5 GU.

7. The treatment method according to any one of claims 1 to 6, wherein, At the end of the step of obtaining said target surface (11) on said component (10), a step of depositing a masking layer is performed on a portion of said target surface (11) called "masked area", the remaining portion of said target surface (11) being called "exposed area", said masking layer being intended to protect said masked area from the plasma.

8. The treatment method of claim 1, wherein, During the pre-crosslinking operation of said varnish coating (13), only a portion of said varnish coating is pre-crosslinked, the other portion being fully crosslinked.

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