Method for applying a visible light-absorbing coating to a substrate

Abstract

One aspect of the invention relates to a method for applying (100), to a substrate (1), a visible light-absorbing coating (20) to form an article (10), such as a timepiece component, said application method (100) being characterized in that it comprises: a first step (110) of providing a substrate (1); a second step (120) of applying a first layer (21) covering at least one portion of the substrate (1) by application of a first formulation comprising a binder, a solvent and pigments having an average size in the nanometric range, the first layer being formed by evaporation of said solvent; a third step (130) of applying a second layer (22) at least partially covering the first layer (21), by application of a second formulation comprising a binder, a solvent, pigment agglomerates dispersed in the binder and a coupling agent, the agglomerates being composed of a mixture of pigments having different particle sizes, and the second layer being formed by evaporation of said solvent.

Description

METHOD FOR DEPOSITING A VISIBLE LIGHT ABSORBING COATING ON A SUBSTRATE Technical field of the invention

[0001] The field of the invention relates to surface treatments of articles, such as decorative articles or watch components.

[0002] The invention relates more particularly to a method of depositing a decorative coating which has the optical characteristic of absorbing visible light.

[0003] The invention also relates to an article, for example a watch component, coated with such a decorative coating absorbing visible light.

[0004] The invention finds a particularly interesting application in the field of watchmaking, for the decoration of articles or components used in timepieces, for example plates, bridges, cogs, screws, oscillating masses, dials, indexes, appliques, window discs, hands or any other component of the movement or external casing of a timepiece. Technological background

[0005] There are visible light absorbing coatings that have a light absorption greater than 99.8%.

[0006] A well-known coating is Vantablack®, which is made from carbon nanotubes oriented perpendicular to the substrate surface and packed tightly together. This coating produces a black color with an absorption coefficient of 99.965% of visible light.

[0007] However, such a coating based on carbon nanotubes is very expensive and presents health risks, as these particles are recognized as carcinogenic, mutagenic or reprotoxic.

[0008] Musou® acrylic paint is also known, which is easier to use and apply and has an absorption of up to 99.4% of visible light and a clarity component L* close to 10. However, this coating has the particularity of being very fragile and light contact with the coating can easily cause the coating to peel or its absorption to deteriorate. For example, it is very complicated to clean this type of coating without damaging its aesthetic appearance if dust or a fiber is deposited on it. Such a paint is not easily applicable, for example, in the watchmaking field.

[0009] Therefore, there is a need to improve these visible light absorbing coatings, allowing their use on items that can be handled, for example watch components, without risk to health and without risk of degradation of the coating by simple contact or handling of the item. Summary of the invention

[0010] In this context, the invention aims to propose an article comprising a coating with very high light absorption while avoiding the use of carbon nanotubes and / or graphene particles.

[0011] According to the invention, one of the aims of the invention is to propose a method for depositing a decorative coating absorbing visible light which is easy to implement and makes it possible to obtain surface coatings with a clarity component L* of less than 20 with substrates of various types.

[0012] To this end, the invention relates to a method of depositing a visible light-absorbing coating on a substrate for the formation of an article, such as a watch component, said deposition method being characterized in that it comprises: a first step of providing a substrate; - a second step of depositing a first layer covering at least a portion of the substrate by applying a first formulation comprising a binder, a solvent and pigments whose average size is of nanometric dimension, the first layer being formed by evaporation of said solvent; - a third step of depositing a second layer at least partially covering the first layer, by applying a second formulation comprising a binder, a solvent, agglomerates of pigments dispersed in the binder and a coupling agent, the agglomerates being composed of a mixture of pigments with different particle sizes, the second layer being formed by evaporation of said solvent.

[0013] Preferably, the second formulation comprises agglomerates composed of a mixture of pigments whose average size is nanometric and pigments whose average size is micrometric.

[0014] Preferably, the coupling agent of the second formulation is a silane.

[0015] Preferably, the pigment agglomerates of the second formulation consist of a central pigment of micrometric dimension onto which a plurality of pigments of nanometric dimensions are chemically grafted at the periphery.

[0016] Preferably, the second formulation comprises between 4 and 8% by mass of pigment agglomerates.

[0017] Preferably, the first formulation comprises pigments whose average size is less than 100 nm.

[0018] Preferably, the first formulation contains between 5 and 10% by mass of pigments.

[0019] Preferably, the first layer and the second layer are applied by spraying, spraying, dipping, screen printing, printing or pad printing of the corresponding formation.

[0020] Preferably, the binder of the first formulation and / or of the second formulation is a polymer.

[0021] Preferably, the binder of the first formulation and / or the second formulation is an acrylic, an epoxy polymer or even a polyurethane.

[0022] Preferably, the first formulation and the second formation are colored inks.

[0023] Preferably, the pigments of the first formulation and / or the pigments of the agglomerates of the second formulation are carbon black.

[0024] Preferably, the method comprises a fourth step of depositing a third layer at least partially covering the second layer, by applying a third formulation comprising a binder, a solvent, pigment agglomerates dispersed in the binder and a coupling agent, the agglomerates being composed of a mixture of pigments with different particle sizes, the proportion by mass of agglomerates in the third formulation being lower than the proportion by mass of agglomerates in the second formulation, said third layer being formed by evaporation of said solvent.

[0025] Preferably, the average size of the pigments forming the agglomerates of the third formulation is identical to the average size of the pigments forming the agglomerates of the second formulation.

[0026] The invention also relates to an article comprising a substrate and a coating applied to the substrate by the method according to the invention.

[0027] Such an article has a light-absorbing surface coating with a lightness component L* of less than 20.

[0028] Preferably, the article is a watch component.

[0029] The invention also relates to a timepiece comprising such a timepiece component. Brief description of the figures

[0030] The aims, advantages and characteristics of the present invention will appear on reading the detailed description below with reference to the following figures: - figure 1 schematically illustrates a sectional view of an article, such as a watch component, comprising a substrate and a visible light absorbing coating according to the invention; - figure 2 illustrates the main successive steps of an exemplary embodiment of a method for depositing a visible light-absorbing coating on a substrate for producing an article, such as a watch component, according to the invention; - figure 3 illustrates an exemplary embodiment of an article according to the invention. Detailed description of the invention

[0031] In the present description, the colorimetric properties of the light-absorbing coating obtained according to the method of depositing a coating according to the invention are expressed using the CIE L*a*b* color space and measured according to the CIE 1976 standard on polished samples with a KONICA MINOLTA CM-3610-A spectrophotometer, with the following parameters: CIE D65 illumination source (daylight 6500°K), 10° tilt, SCI measurements (specular reflection included), 4 mm diameter measuring area.

[0032] A CIELAB color space (compliant with CIE standards No. 15, ISO 7724 / 1, DIN 5033 Teil 7, ASTM E-1164) has a component of clarity L*, representative of the way in which the material reflects light, similar to clarity, with an a* component which is the green / red component and a b* component which is the blue / yellow component.

[0033] In the present application, the average size of the particles and pigments is characterized with respect to the d90 value of a particle size distribution.

[0034] Figure 1 schematically illustrates a sectional view of an article 10, such as a watch component, comprising a substrate 1 as well as a decorative coating 20 and having visible light absorption properties.

[0035] The coating 20 covers at least a portion of the substrate 1. Such a coating 20 according to the invention forms a non-uniform structure composed of pigment agglomerates of different particle sizes. The coating 20 may comprise several stacked layers composed of these pigment agglomerates.

[0036] Preferably, the density of the pigment agglomerates between the different layers of the coating 20 is also variable, preferably decreasing with the increase in the number of layers.

[0037] Article 10 is for example a watch component, for example a plate, a bridge, a wheel, a screw, an oscillating weight, a dial, an index, an applique, a window disc, a hand or any other component or organ of a watch movement or of a component of a timepiece to which one wishes to give an impression of deep and intense color, without light reflection, with a clarity component L* less than 20.

[0038] Figure 3 illustrates a timepiece 200 comprising an article 10 according to the invention. In this exemplary embodiment, the article 10 according to the invention is a dial.

[0039] The substrate 1 may be of a variable nature, for example made of metallic material, polymer material or even ceramic material, or even composite material.

[0040] By means of the method according to the invention, it is possible to obtain an article 10 with a coating 20 whose clarity component L* is less than 20. For comparison, a coating method using physical vapor deposition (PVD) does not allow a coating to be obtained with a clarity component L* less than 20 due to the topology of the deposited layers. With PVD deposition, the clarity component L* of a matte coating is between 25 and 30.

[0041] The non-uniform structure of the coating 20 makes it possible to avoid reflection phenomena with the visible surface of the coating. The coating 20 also makes it possible to diffuse light in the non-uniform structure created by the different agglomerates of pigments of different particle sizes and possibly by the variations in density of these agglomerates between the different superimposed layers. This has the effect of trapping the light as much as possible, so as to obtain high absorption of the light.

[0042] The coating 20 according to the invention proposes a solution making it possible to trap the incident visible light arriving on the coating by a “chaotic” surface topology in joint on the distribution, the size of the different agglomerates.

[0043] The coating 20 comprises a first layer 21 forming a base layer, configured to cover the substrate 1, at least on a portion of the substrate 1.

[0044] Preferably, the first layer 21 completely covers at least one surface of the substrate 1.

[0045] The first layer 21 has a sufficient thickness for it to be homogeneous and opaque and for the optical disturbance of the substrate 1 to no longer be active. The first layer 21 has, for example, a thickness equal to or greater than 1 μm and less than 20 μm, and more preferably a thickness of between 5 μm and 10 μm.

[0046] Preferably, the first layer 21 is formed by the deposition on the substrate 1 of a first formulation which is a liquid mixture comprising a binder, pigments, and a solvent.

[0047] For example, the first layer 21 is formed by the deposition of a first liquid mixture comprising, by mass, 30 to 40% binder, 50 to 60% solvent and between 5 and 10% pigments.

[0048] For example, the first layer 21 is formed by the deposition of a first liquid mixture consisting, by mass, of 40% acrylic binder, 50% solvents and 10% Emperor® 1600 carbon black pigments.

[0049] Optionally, the first formulation may also include a matting agent, for example a nanosilica, to further accentuate the intensity of the coating 20.

[0050] Optionally, the first formulation may also include a dispersing agent facilitating the suspension of the pigments in the formulation.

[0051] Preferably, the binder of the first formulation is a polymer, for example an acrylic, an epoxy polymer or even a polyurethane.

[0052] For example, the first formulation is a colored ink.

[0053] For example, the first formulation is a black ink featuring carbon black pigments.

[0054] The first formulation is for example applied by spraying, by spraying, by dipping, by screen printing, by printing or even by pad printing on the substrate 1.

[0055] Once the first formulation is applied to the substrate 1, the solvent evaporates, the binder shrinks around the pigments thus creating the first layer 21 of the coating 20.

[0056] Preferably, the pigments of the first layer 21 have an average size (d90) of nanometric dimension, for example between 20 and 120 nm, preferably less than 100 nm. Thus, the first layer 21 is a homogeneous layer with low roughness.

[0057] The first layer 21 is covered, at least partially, by a second layer 22. This second layer 22 may be part of a stack 25 of several layers superimposed on one another, the stack 25 at least partially covering the first layer 21.

[0058] The second layer 22 is formed by depositing, on the first layer 21, a second formulation comprising a binder, pigment agglomerates dispersed in the binder, a solvent and a coupling agent.

[0059] Once the second formulation is applied to the first layer 21, the solvent evaporates, the binder shrinks around the pigment agglomerates thus creating the second layer 22 of the coating 20.

[0060] The second layer 22 consists of a plurality of pigment agglomerates composed of a mixture of pigments with different particle sizes.

[0061] Preferably, the second layer 22 is made up of pigment agglomerates composed of the mixture of pigments whose average size is of nanometric dimension and pigments whose average size is of micrometric dimension.

[0062] Preferably, the pigment agglomerates of the second layer 22 are composed of a central pigment of micrometric dimension onto which is chemically grafted (by the coupling agent of the formulation) a plurality of pigments of nanometric dimensions, the nanometric pigments being coupled at the periphery of the central pigment.

[0063] The coupling agent will allow a strong chemical interaction between the different pigments.

[0064] Optionally, the second formulation may also include a matting agent, for example a nanosilica, to further accentuate the intensity of the coating 20.

[0065] Preferably, the second formulation forming the second layer 22 comprises between 4 and 8% by mass of pigment agglomerates in the formulation.

[0066] Preferably, the binder of the second formulation is a polymer, for example an acrylic, an epoxy polymer or even a polyurethane.

[0067] For example, the binder in the second formulation is identical to the binder in the first formulation.

[0068] For example, the second formulation is a colored ink.

[0069] For example, the second formulation is a black ink featuring carbon black pigments.

[0070] For example, the coupling agent in the second formulation is a silane.

[0071] The second formulation is for example applied by spraying, by spraying, by dipping, by screen printing, by printing or even by pad printing on the first layer 21.

[0072] As shown by way of example in FIG. 1, the coating 20 may comprise a third layer 23 covering at least partially the second layer 22. This third layer 23 forms a second layer of the stack 25, this stack being able to comprise a plurality of layers.

[0073] This third layer 23 is also made up of a plurality of pigment agglomerates composed of a mixture of pigments with different particle sizes.

[0074] Preferably, the third layer 23 is made up of pigment agglomerates composed of the mixture of pigments whose average size is of nanometric dimension and pigments whose average size is of micrometric dimension.

[0075] Preferably, the pigment agglomerates of the third layer 23 are composed of a central pigment of micrometric dimension onto which a plurality of pigments of nanometric dimensions are chemically grafted, the nanometric pigments being coupled to the periphery of the central pigment.

[0076] Preferably, the average size of the pigments constituting the agglomerates of the second formulation is identical to the average size of the pigments constituting the agglomerates of the third formulation.

[0077] Optionally, the third formulation may also include a matting agent, for example a nanosilica, to further accentuate the intensity of the coating 20.

[0078] Preferably, the third formulation forming the third layer 23 comprises between 1% and 4% by mass of pigments in the formulation.

[0079] Preferably, the third formulation comprises a mass proportion of agglomerates lower than the mass proportion of agglomerates of the second formulation so as to increase the overall roughness of the coating.

[0080] Preferably, the third formulation forming the third layer 23 comprises between 1% and 4% by mass of pigments in the formulation and the second formulation forming the second layer 22 comprises between 4 and 8% by mass of pigments in the formulation.

[0081] Preferably, the binder of the third formulation is a polymer, for example an acrylic, an epoxy polymer or even a polyurethane.

[0082] For example, the binder in the third formulation is identical to the binder in the second formulation.

[0083] For example, the third formulation is a colored ink.

[0084] For example, the third formulation is a black ink featuring carbon black pigments.

[0085] For example, the coupling agent in the third formulation is a silane.

[0086] The third formulation is for example applied by spraying, by spraying, by dipping, by screen printing, by printing or even by pad printing on the second layer 22.

[0087] Figure 2 illustrates the main steps of the method 100 for depositing a coating 20 absorbing visible light on a substrate 1 according to the invention.

[0088] The deposition method 100 according to the invention comprises a first step 110 of providing a substrate 1.

[0089] The deposition method 100 according to the invention comprises a second step 120 of deposition of a first layer 21, called the base layer, completely covering at least a portion of the substrate 1. This first deposition step 120 is carried out by spraying, by spraying, by dipping, by screen printing, by printing or even by pad printing of a first formulation comprising a binder, a solvent and between 5 and 10% in mass of pigments of an average size (d90) of nanometric dimension, for example less than 100 nm.

[0090] This second step 120 of depositing a first layer 21 comprises a sub-step of evaporation of the solvent of the first formulation applied to the substrate 1 so that the binder shrinks around the pigments to form the first layer 21 of the coating 20.

[0091] The deposition method 100 also comprises a third step 130 of deposition of a second layer 22 at least partially covering the first layer 21 previously deposited. This second layer 22 is composed of a plurality of pigment agglomerates composed of a mixture of pigments with different particle sizes.

[0092] This second layer 22 is deposited by spraying, by spraying, by dipping, by screen printing, by printing or even by pad printing of a second formulation comprising a binder, a solvent, pigment agglomerates, and a coupling agent.

[0093] Preferably, the second formulation comprises between 4 and 8% agglomerates by mass in the formulation.

[0094] The second formulation comprises a plurality of pigment agglomerates composed of a mixture of pigments with different particle sizes.

[0095] Preferably, the pigment agglomerates of the second formulation are composed of a mixture of pigments whose average size is nanometric and pigments whose average size is micrometric.

[0096] Preferably, the pigment agglomerates of the second formulation are composed of a central pigment of micrometric dimension onto which a plurality of pigments of nanometric dimensions are chemically grafted (via the coupling agent), the nanometric pigments being coupled at the periphery of the central pigment.

[0097] This third step 130 comprises a sub-step of evaporation of the solvent of the second formulation applied to the first layer 21 so that the binder shrinks around the pigments to form the second layer 22 of the coating 20.

[0098] The deposition method 100 also comprises a fourth step 140 of deposition of a third layer 23 at least partially covering the second layer 22 previously deposited.

[0099] This third layer 23 is also deposited by spraying, by spraying, by dipping, by screen printing, by printing or even by pad printing of a third formulation comprising a binder, a solvent, pigment agglomerates, and a coupling agent.

[0100] Preferably, the third formulation comprises between 1 and 4% agglomerates by mass in the formulation.

[0101] The third formulation comprises a plurality of pigment agglomerates composed of a mixture of pigments with different particle sizes.

[0102] Preferably, the pigment agglomerates of the third formulation are composed of a mixture of pigments whose average size is nanometric and pigments whose average size is micrometric.

[0103] Preferably, the pigment agglomerates of the third formulation are composed of a central pigment of micrometric dimension onto which a plurality of pigments of nanometric dimensions are chemically grafted (via the coupling agent), the nanometric pigments being coupled at the periphery of the central pigment.

[0104] Preferably, this third deposited layer 23 has an agglomerate size identical to the second layer 22 but with a lower density.

[0105] This fourth step 140 comprises a sub-step of evaporation of the solvent of the third formulation applied to the second layer 22 so that the binder shrinks around the pigments to form the third layer 23 of the coating 20.

[0106] Of course, the deposition method 100 may comprise other steps of depositing additional layers to form a stack 25 of a plurality of layers of pigment agglomerates as described previously. Preferably, the different layers forming the stack 25 have different densities of pigment agglomerates. Preferably, an upper layer covering a lower layer of the stack 25 has a density of pigment agglomerates lower than the density of pigment agglomerates of the lower layer.

[0107] According to a first exemplary embodiment of the invention, a brass substrate is used, for example for the formation of a dial, on which a light-absorbing coating according to the invention is applied.

[0108] The brass substrate, for example, has a thickness of 0.27 mm.

[0109] The first layer 21 is applied to the brass substrate by dipping from a first formulation consisting of 2 g of polyurethane resin (Berlacryl), 0.5 g of Emperor 1600 carbon black pigments and 2.8 g of Berlaflex diluent. The first layer 21 is left to dry for 20 minutes to allow the diluent to evaporate.

[0110] The pigment agglomerates composing the second solution are prepared beforehand from a 5% isopropyl alcohol solution in organosilane (for example Methoxysilane) with suspension of micrometric-sized pigments and nanometric-sized pigments. The solution is dried and the powder of agglomerates formed is recovered.

[0111] The second layer 22 of the coating 20 is applied to the first layer 21 by dipping from a second formulation consisting of 2 g of polyurethane resin (Berlacryl), 0.3 g of agglomerate powder and 2.8 g of Berlaflex diluent. The second layer 22 is left to dry for 20 minutes to allow the diluent to evaporate.

[0112] With such a coating, a brass dial with a black surface coating with a clarity component L* of 16 is obtained.

Claims

CLAIMS 1. Method for depositing (100) on a substrate (1) a coating (20) absorbing visible light for the formation of an article (10), such as a watch component, said deposition method (100) being characterized in that it comprises: - a first step (110) of providing a substrate (1); - a second step (120) of depositing a first layer (21) covering at least a portion of the substrate (1) by applying a first formulation comprising a binder, a solvent and pigments whose average size is of nanometric dimension, the first layer being formed by evaporation of said solvent; - a third step (130) of depositing a second layer (22) at least partially covering the first layer (21), by applying a second formulation comprising a binder, a solvent, agglomerates of pigments dispersed in the binder and a coupling agent, the agglomerates being composed of a mixture of pigments with different particle sizes, the second layer being formed by evaporation of said solvent.

2. Method for depositing (100) on a substrate (1) a coating (20) absorbing visible light for the formation of an article (10), according to the preceding claim, characterized in that the second formulation comprises agglomerates composed of the mixture of pigments whose average size is of nanometric dimension and pigments whose average size is of micrometric dimension.

3. Method of depositing (100) on a substrate (1) a coating (20) absorbing visible light for the formation of an article (10), according to one of the preceding claims, characterized in that the coupling agent of the second formulation is a silane.

4. Method for depositing (100) on a substrate (1) a coating (20) absorbing visible light for the formation of an article (10), according to one of the preceding claims, characterized in that the pigment agglomerates of the second formulation consist of a central pigment of micrometric dimension onto which a plurality of pigments of nanometric dimensions are chemically grafted at the periphery.

5. Method for depositing (100) on a substrate (1) a coating (20) absorbing visible light for the formation of an article (10), according to one of the preceding claims, characterized in that the second formulation comprises between 4 and 8% by mass of pigment agglomerates.

6. Method for depositing (100) on a substrate (1) a coating (20) absorbing visible light for the formation of an article (10), according to one of the preceding claims, characterized in that the first formulation comprises pigments whose average size is less than 100 nm.

7. Method for depositing (100) on a substrate (1) a coating (20) absorbing visible light for the formation of an article (10), according to one of the preceding claims, characterized in that the first formulation comprises between 5 and 10% by mass of pigments.

8. Method for depositing (100) on a substrate (1) a coating (20) absorbing visible light for the formation of an article (10), according to one of the preceding claims, characterized in that the first layer and the second layer are applied by spraying, by spraying, by dipping, by screen printing, by printing or by pad printing of the corresponding formation.

9. Method of depositing (100) on a substrate (1) a coating (20) absorbing visible light for the formation of an article (10), according to one of the preceding claims, characterized in that the binder of the first formulation and / or the second formulation is a polymer.

10. Method for depositing (100) on a substrate (1) a coating (20) absorbing visible light for the formation of an article (10), according to one of the preceding claims, characterized in that the binder of the first formulation and / or of the second formulation is an acrylic, an epoxy polymer or even a polyurethane.

11. Method for depositing (100) on a substrate (1) a coating (20) absorbing visible light for the formation of an article (10), according to one of the preceding claims, characterized in that the first formulation and the second formation are colored inks.

12. Method for depositing (100) on a substrate (1) a coating (20) absorbing visible light for the formation of an article (10), according to one of the preceding claims, characterized in that the pigments of the first formulation and / or the pigments of the agglomerates of the second formulation are carbon black.

13. Method for depositing (100) on a substrate (1) a coating (20) absorbing visible light for the formation of an article (10), according to one of the preceding claims, characterized in that the method comprises a fourth step (140) of depositing a third layer at least partially covering the second layer (22), by the application of a third formulation comprising a binder, a solvent, agglomerates of pigments dispersed in the binder and a coupling agent, the agglomerates being composed of a mixture of pigments with different particle sizes, the proportion by mass of agglomerates in the third formulation being lower than the proportion by mass of agglomerates in the second formulation, said third layer being formed by evaporation of said solvent.

14. Method for depositing (100) on a substrate (1) a coating (20) absorbing visible light for the formation of an article (10), according to the preceding claim, characterized in that the average size of the pigments forming the agglomerates of the third formulation is identical to the average size of the pigments forming the agglomerates of the second formulation.

15. Article (10) characterized in that it comprises a substrate (1) and a coating (20) absorbing visible light deposited by the deposition method (100) according to one of claims 1 to 14.

16. Article (10) according to the preceding claim characterized in that the article (20) is a watch component.

17. Timepiece (200) comprising a timepiece component (10) according to claim 16.

Images