Article, such as timepiece assembly, comprising substrate and coating absorbing visible light

Abstract

One aspect of the invention relates to an article (10) comprising a substrate (1) and a multilayer coating (20) deposited on the substrate (1), the multilayer coating (20) being formed by combining a plurality of layers (21, 22, 23, 24) comprising a binder and a pigment, the coating (20) comprising pigments of different particle sizes.

Description

Field of the Invention

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

[0002] The present invention further relates to an article coated with such a coating that absorbs visible light, such as a watch component.

[0003] The present invention has a particularly interesting application in the field of horology for decorating articles or components used in watches, such as plates, cocks, bridges, gear trains, screws, oscillating weights, dials, indexes, appliqués, aperture discs, hands or any other component of the movement or external components of the watch. Background Art

[0004] There are coatings that absorb visible light and have a light absorption rate of more than 99.8%.

[0005] In particular, coatings are known that are based on carbon nanotubes oriented perpendicular to the surface of the substrate and pressed against each other. Such coatings provide a black color with a visible light absorption coefficient of 99.965%.

[0006] However, coatings based on carbon nanotubes are very expensive and pose health risks, as these particles are known to be carcinogenic, mutagenic or reprotoxic.

[0007] Easier to use and apply Acrylic paints have a visible light absorption rate of up to 99.4% and a brightness component L* close to 10. However, this type of coating has the particularity of being very fragile, and slight contact with the coating can easily cause peeling of the coating or deterioration of its absorption rate. For example, if dust or fibers are deposited on it, it is very difficult to clean this type of coating without compromising its aesthetics. Such paints are not easily applicable in, for example, the watchmaking industry.

[0008] Therefore, there is a need to improve these coatings that absorb visible light so that they can be used on articles that can be processed, such as watch components, without health risks and without the risk of damage to the coating due to simple contact or handling of the article. Summary of the Invention

[0009] In this context, the object of the present invention is to provide an article with a coating having a very high light absorption rate while avoiding the use of carbon nanotubes and / or graphene particles.

[0010] To this end, the present invention relates to an article comprising a substrate and a multi-layer coating deposited on the substrate, the multi-layer coating being formed by combining a plurality of layers comprising a binder and a pigment, the coating comprising pigments of different particle sizes.

[0011] According to the present invention, an article coated with a decorative coating that absorbs visible light can achieve a brightness component L* of less than 20 using various types of substrates.

[0012] In addition to the features mentioned in the foregoing paragraphs, and taking into account individual cases or any technically possible combinations, the article according to the present invention may have one or more of the following supplementary features:

[0013] - The multi-layer coating comprises nano- and micro-sized pigments;

[0014] - The multi-layer coating comprises glass beads;

[0015] - The multi-layer coating comprises a primer coating covering at least a part of the substrate, the primer coating comprising a pigment having a d90 percentile of nano size;

[0016] - The multi-layer coating comprises a stack of a plurality of continuous layers, the continuous layers being superposed on one another and at least partially covering the primer coating, each of the continuous layers of the stack comprising a pigment having a d90 percentile different from the d90 percentile of the pigment in the layer it covers;

[0017] - Each of the continuous layers in the stack comprises a pigment having a d90 percentile greater than the d90 percentile of the pigment in the layer it covers;

[0018] - Each layer n of the stack has a pigment with a d90 percentile equal to n*k / 10 μm, where k is a homothetic factor between the d90 percentiles of the pigments of two consecutive layers of the stack;

[0019] - The multi-layer coating comprises a plurality of layers of different particle sizes, the layers being juxtaposed relative to one another and each covering a predetermined part of the primer coating;

[0020] - The size of the pigments in the plurality of layers covering the primer coating is in the micron range;

[0021] - The multi-layer coating comprises a first layer at least partially covering a first part of the primer coating and a second layer juxtaposed with the first layer and at least partially covering a second part of the primer coating, the second part being different from the first part, and the pigment of the second layer having a d90 percentile greater than the d90 percentile of the pigment in the first layer;

[0022] - The multi-layer coating includes a first layer that at least partially covers the base coating, and the first layer contains pigment aggregates composed of a mixture of pigments with different particle sizes;

[0023] - The first layer contains pigment aggregates composed of a mixture of pigments with a d90 percentile in the nanometer size range and pigments with a d90 percentile in the micrometer size range;

[0024] - The pigment aggregates in the first layer are composed of a central pigment in the micrometer size range, and a plurality of pigments in the nanometer size range are chemically grafted onto the central pigment in the micrometer size range on the periphery;

[0025] - The binder of the multiple layers of the coating is a polymer;

[0026] - The binder of the multiple layers of the multi-layer coating is acrylic, epoxy polymer or polyurethane;

[0027] - The pigment of the multiple layers of the multi-layer coating is carbon black;

[0028] - The multi-layer coating has a lightness component L* of less than 20;

[0029] - The article is a clock component.

[0030] The present invention further relates to a clock including such a clock component. Description of the Drawings

[0031] The objects, advantages and features of the present invention will be better understood after reading the following detailed description with reference to the accompanying drawings:

[0032] Figure 1 A cross-sectional view schematically showing a first exemplary embodiment of an article according to the present invention, the article being, for example, a clock component, which includes a substrate and a coating that absorbs visible light;

[0033] Figure 2 A cross-sectional view schematically showing a second exemplary embodiment of an article according to the present invention, the article being, for example, a clock component, which includes a substrate and a coating that absorbs visible light;

[0034] Figure 3 A cross-sectional view schematically showing a third exemplary embodiment of an article according to the present invention, the article being, for example, a clock component, which includes a substrate and a coating that absorbs visible light;

[0035] Figure 4 An exemplary embodiment of an article according to the present invention is shown. Detailed Description

[0036] In this specification, the chromaticity properties of the light-absorbing coating obtained by the method of depositing a coating according to the invention are represented using the CIE L*a*b* color space and are measured on a polished sample using a KONICA MINOLTA CM-3610-A spectrophotometer according to the CIE 1976 standard with the following parameters: illumination light source CIE D65 (daylight 6500°K), 10° inclination, SCI measurement (including specular reflection), measurement area diameter 4 mm.

[0037] The CIELAB color space (according to CIE standard no. 15, ISO 7724 / 1, DIN 5033 Teil 7, ASTM E-1164) has a luminance component L*, which represents the way the material reflects light and is assimilated to luminance, and an a* component as the green / red component and a b* component as the blue / yellow component.

[0038] In the present application, the sizes of the particles and pigments are characterized relative to the d90 value of the particle size distribution. In the particle size distribution, the use of the d90 percentile means that at least 90% of all the particles or pigments used have a size below this d90 value.

[0039] First exemplary embodiment

[0040] Figure 1 A cross-sectional view of a first exemplary embodiment of an article 10, such as a clock assembly, is schematically shown, which includes a substrate 1 and a visible light-absorbing coating 20 covering at least a portion of the substrate 1 by a deposition method 100 according to the invention. Such a light-absorbing coating 20 according to the invention forms a multi-layer structure containing pigments, and the pigments have a particle size that varies between the layers, preferably increasing with the increase in the number of layers.

[0041] Preferably, the pigment density between the layers of the coating 20 is also variable, preferably decreasing with the increase in the number of layers.

[0042] The article 10 is, for example, a clock assembly, such as a main board, pallet, wheel, screw, balance weight, dial, hour marker, lettering block, window disc, pointer or any other component or part of a clock movement or an external component of a clock, which is intended to have a deep and intense color impression without light reflection and the luminance component L* is less than 20.

[0043] Figure 4 A clock 200 including the article 10 according to the invention is shown. In this exemplary embodiment, the article 10 according to the invention is a dial.

[0044] The substrate 1 can be of any nature, for example, it can be made of metal, polymer, ceramic or even composite material.

[0045] Using various substrates, article 10 includes a non-uniform coating 20 having a transparency component L* of less than 20. In comparison, due to the topology of the deposited layer, a coating method using physical vapor deposition (PVD) of a uniform thin film cannot be used to produce a coating having a luminance component L* of less than 20. In the case of PVD, the luminance component L* of a matte coating is 25 to 30.

[0046] The specific multi-layer structure of the light-absorbing coating 20 according to the present invention can avoid the reflection phenomenon on the visible surface of the coating. The coating 20 also allows light to be scattered in the structure generated by the particle size difference of the pigments constituting the coating until it is trapped, thereby obtaining the maximum light absorption rate.

[0047] Coating 20 includes a bottom coating 21 that forms a base layer and is configured to cover substrate 1 at least on a part of substrate 1.

[0048] Preferably, the bottom coating 21 completely covers at least one surface of substrate 1.

[0049] The bottom coating 21 has a thickness sufficient to ensure its uniformity and opacity and that optical interference from substrate 1 no longer has an effect. For example, the bottom coating 21 has a thickness equal to or greater than 1 μm and less than 20 μm, and more preferably a thickness of 5 μm to 10 μm.

[0050] Preferably, the bottom coating 21 is formed by depositing a first liquid mixture that includes a binder, a pigment, and a solvent. When the first liquid mixture dries, the solvent evaporates and the binder shrinks around the pigment, thereby producing the bottom coating 21 of coating 20.

[0051] For example, the bottom coating is formed by depositing a first liquid mixture that includes 30 to 40 wt% of a binder, 50 to 60 wt% of a solvent, and 5 to 10 wt% of a pigment.

[0052] For example, the bottom coating is formed by depositing a first liquid mixture consisting of 30 wt% acrylic binder, 60 wt% solvent, and 10 wt% 1600 carbon black pigment.

[0053] Optionally, the bottom coating 21 may further include a matting agent, such as nano-silica, to further enhance the strength of the coating 20.

[0054] Optionally, the bottom coating 21 may further include a dispersant to help the pigment suspend in the liquid mixture.

[0055] Preferably, the binder of the bottom coating 21 is a polymer, such as acrylic, epoxy polymer, or polyurethane.

[0056] For example, the undercoat layer 21 is formed by applying a colored ink.

[0057] For example, the undercoat layer 21 is formed by applying a black ink containing carbon black pigment.

[0058] The undercoat layer 21 is formed by sputtering, spraying, dipping, screen printing, printing or pad printing a first liquid mixture onto the substrate 1.

[0059] Preferably, the pigment in the undercoat layer 21 has a nano-size, for example, a d90 percentile of 20 to 120 nm, preferably less than 100 nm. Thus, the undercoat layer 21 is a uniform layer with low roughness.

[0060] The undercoat layer 21 is covered by a stack 25 of a plurality of layers 22, 23, 24 stacked on top of each other, and each layer of the stack 25 has a pigment with a d90 percentile different from that of the pigment in the layer it covers.

[0061] Preferably, the stack 25 has a pigment distributed according to the d90 percentile increasing from the substrate to the surface of the coating 20. Thus, each layer of the stack 25 has a pigment with a d90 percentile greater than that of the pigment in the layer it covers.

[0062] Preferably, each layer n of the stack 25 has a pigment with a d90 percentile equal to n*k / 10 μm, where k is the similarity factor between the d90 percentile of the pigment in the previously deposited layer n - 1 and the d90 percentile of the pigment in the layer n to be deposited (i.e., between two consecutive layers of the stack 25).

[0063] Preferably, the similarity factor is 5 to 1000.

[0064] In Figure 1 the exemplary embodiment shown, the stack 25 includes three consecutive layers 22, 23, 24. It goes without saying that the stack 25 can include at least two consecutive layers or more than three consecutive layers to form a specific structure of the stack 25 covering the undercoat layer 21.

[0065] The first layer 22 of the stack 25 contains a pigment with a d90 percentile greater than that of the pigment in the undercoat layer 21, for example, it is in the micron size and less than 20 μm, preferably approximately 15 μm.

[0066] The second layer 23 of the stack 25 that at least partially covers the first layer 22 of the stack 25 contains a pigment with a d90 percentile, for example, approximately 80 μm.

[0067] The third layer 24 of the stack 25 that at least partially covers the second layer 23 of the stack 25 contains a pigment with a d90 percentile, for example, approximately 250 μm.

[0068] Each of the layers 22, 23, 24 is formed by successively depositing a liquid mixture comprising a binder, a pigment, and a solvent. The d90 percentile of the pigment in the various liquid mixtures varies according to the above ratios to form respective layers having an improved particle size distribution, thereby increasing the overall roughness of the coating.

[0069] After applying each mixture by sputtering, spraying, dipping, screen printing, printing, or pad printing, the solvent evaporates to allow the binder around the pigment to polymerize and shrink, thereby forming a solid layer that at least partially covers the previous layer or the primer coat 21. The new layer has a greater roughness than the previous layer.

[0070] Preferably, the binder and pigment properties in each of the layers 22, 23, 24 of the stack 25 are the same.

[0071] Optionally, the layers 22, 23, 24 of the stack 25 may contain a matting agent, such as nano-silica, to further strengthen the stack 25 and, more generally, the strength of the coating 20.

[0072] Optionally, the layers 22, 23, 24 of the stack 25 may contain glass beads to further increase the roughness of the stack. Preferably, the glass beads are used in the last layer of the stack 25.

[0073] Optionally, the layers 22, 23, and 24 of the stack 25 may contain a dispersant to help suspend the pigment in the liquid mixture.

[0074] Preferably, the binder in the layers 22, 23, 24 forming the stack 25 is a polymer, such as acrylic, epoxy polymer, or polyurethane.

[0075] For example, the layers 22, 23, 24 forming the stack 25 are formed by applying a colored ink.

[0076] Preferably, the binder, pigment properties, and solvent used to form the layers of the stack 25 are the same as those used to manufacture the primer coat 21.

[0077] The pigment used to form the layers of the stack 25 may also have properties different from those of the pigment used to manufacture the primer coat 21.

[0078] Preferably, the density of the pigment in each of the layers 22, 23, 24 is variable.

[0079] Preferably, the pigment density in the layers 22, 23, 24 of the stack 25 decreases as the d90 percentile size of the pigment in the layers 22, 23, 24 increases.

[0080] For example, the first layer 22 of the stack 25 is made of a liquid mixture containing 4 to 10% by weight of a pigment, preferably 4 to 8% by weight of a pigment.

[0081] For example, the second layer 23 of the stack 25 is made of a liquid mixture containing 1 to 4% by weight of a pigment.

[0082] For example, the third layer 24 of the stack 25 is made of a liquid mixture containing 0.5 to 4% by weight of a pigment, preferably 0.5 to 1% by weight of a pigment.

[0083] For example, the substrate 1 is made of brass, such as for forming a dial, and the light-absorbing coating according to the present invention is applied thereto. The brass substrate is, for example, 0.27 mm thick.

[0084] The undercoat 21 is applied to the brass substrate by dipping in a first liquid mixture consisting of 2 g of polyurethane resin (Berlacryl), 0.5 g of Emperor 1600 carbon black pigment, and 2.8 g of Berlaflex diluent. This layer is dried for 20 minutes to evaporate the diluent.

[0085] The first layer 22 of the stack 25 is applied to the undercoat 21 by dipping in a second liquid mixture consisting of 2 g of polyurethane resin (Berlacryl), 0.3 g of Living Ink pigment, and 3.5 g of Berlaflex diluent. This layer is dried for 20 minutes to evaporate the diluent.

[0086] The second layer 23 of the stack 25 is applied to the first layer 22 by dipping in a third liquid mixture consisting of 2 g of polyurethane resin (Berlacryl), 0.2 g of NoritA ultra E153 pigment, and 4 g of Berlaflex diluent. This layer is dried for 20 minutes to evaporate the diluent.

[0087] The third layer 24 of the stack 25 is applied to the second layer 23 by dipping in a fourth liquid mixture consisting of 2 g of polyurethane resin (Berlacryl), 0.2 g of NoritSX super E153 carbon pigment, 1.5 g of 90 - 150 μm glass beads, and 4 g of Berlaflex diluent. This layer is dried for 20 minutes to evaporate the diluent.

[0088] Such a coating 20 is made to have a black surface coating and a brass dial with a luminance component L* of 15.9.

[0089] Second exemplary embodiment

[0090] Figure 2A cross-sectional view schematically shows a second exemplary embodiment of an article 10’, such as a clock assembly, which includes a substrate 1 and a decorative coating 20’ having visible light absorption properties.

[0091] The coating 20’ covers at least a portion of the substrate 1. In this second exemplary embodiment, the coating 20’ according to the present invention forms a non-uniform structure composed of a plurality of regions having variable roughness, and different regions of the coating have pigments with different particle sizes.

[0092] Preferably, the density of the pigment between the respective regions of the coating 20’ is also variable, preferably decreasing as the size of the pigment increases.

[0093] The article 10’ is, for example, a clock assembly, such as a motherboard, pallet, wheel, screw, balance weight, dial, time scale, lettering block, window disc, pointer, or any other component or member of a clock movement or an external component of a clock, which is intended to have a deep and intense color impression without light reflection, and the brightness component L* is less than 20.

[0094] The multi-region structure of the coating 20’ according to the present invention can produce a pattern by changing different levels of visible light absorption. Preferably, the multi-region structure of the coating 20’ according to the present invention can produce a monochromatic pattern having different visible light absorption levels.

[0095] The coating 20’ includes a primer coat 21 that forms a base layer and is configured to cover the substrate 1 at least on a part of the substrate 1. The primer coat 21 is the same as the primer coat described previously with reference to Figure 1 description.

[0096] The multi-region structure of the coating 20’ is formed by a plurality of juxtaposed layers that respectively cover defined portions of the primer coat 21.

[0097] The primer coat 21 is covered by a first layer 22’ at a first defined portion of the primer coat 21. The first layer 22’ has a pigment with a d90 percentile greater than the d90 percentile of the pigment in the primer coat 21.

[0098] The primer coat 21 is covered by a second layer 23’ at a defined second portion of the primer coat 21, and the second portion is different from the first portion covered by the first layer 22’. The second portion may or may not be juxtaposed with the first portion.

[0099] The second layer 23’ has a pigment with a d90 percentile greater than the d90 percentile of the pigment in the first layer 22’.

[0100] The primer coat 21 may also be covered by other layers at various specific portions of the primer coat 21 to produce a specific pattern having specific optical characteristics and a light absorption level that varies according to the size of the pigment used.

[0101] For illustrative purposes, Figure 2 the exemplary embodiments shown in Figure 2 include a third layer 24' locally deposited on the primer coat 21 at a defined third portion. This third portion is different from the first portion covered by the first layer 22' and the second portion covered by the second layer 23'. This third portion may be juxtaposed with the first portion and / or the second portion. These different layers applied to the primer coat 21 are not superimposed on each other in any case.

[0102] The third layer 24' has a pigment with a d90 percentile greater than that of the pigment in the second layer 23'.

[0103] For example, the pigments in the layers 22', 23', 24' covering the primer coat 21 have micron sizes.

[0104] For example, the first layer 22' contains a pigment having a d90 percentile with a micron size less than 20 μm, for example approximately 15 μm.

[0105] For example, the second layer 23' contains a pigment having a d90 percentile from 20 μm to 100 μm, preferably approximately 80 μm.

[0106] For example, the third layer 24' contains a pigment having a d90 percentile from 100 μm to 300 μm, preferably approximately 250 μm.

[0107] Each of the layers 22', 23', 24' that partially covers the primer coat 21 is formed by depositing a liquid mixture via one or more masks applied to the primer coat 21, thereby masking certain areas and exposing other areas intended to receive layers with a predetermined particle size.

[0108] Each of the layers 22', 23', 24' that partially covers the primer coat 21 is formed by depositing a liquid mixture containing a binder, a pigment, and a solvent, and the d90 percentile of the pigment in the different liquid mixtures varies between the different layers.

[0109] Each of the layers 22', 23', 24' that partially covers the primer coat 21 is formed by depositing the liquid mixture by sputtering, spraying, dipping, screen printing, printing, or pad printing.

[0110] After each mixture is applied to the primer coat 21, the solvent evaporates to allow the binder to polymerize and shrink around the pigment, thereby forming the respective layers with different particle sizes.

[0111] Preferably, the binder and pigment properties in the respective layers 22', 23', 24' are the same.

[0112] Optionally, each layer of the coating 20' may contain a matting agent, such as nano-silica, to further enhance the strength of the coating 20'.

[0113] Optionally, each layer of the coating 20' may contain glass beads to further increase the roughness of the stack.

[0114] Preferably, the binder in each layer of the coating 20' is a polymer, such as acrylic, epoxy polymer or polyurethane.

[0115] For example, each layer of the coating 20' is formed by applying a colored ink, such as a black ink containing carbon black as a pigment.

[0116] Preferably, the binder and pigment properties in each layer of the coating 20' are the same.

[0117] However, the pigments in each layer of the coating 20' may be different in nature between the layers and different from the pigments in the undercoat 21.

[0118] The pigment density between the respective layers 22', 23', 24' may be variable, preferably decreasing with an increase in pigment size.

[0119] For example, the first layer 22' is made of a liquid mixture containing 4 to 10% by weight, preferably 4 to 8% by weight, of a pigment.

[0120] For example, the second layer 23' is made of a liquid mixture containing 1 to 5% by weight, preferably 1 to 4% by weight, of a pigment.

[0121] For example, the third layer 24' is made of a liquid mixture containing 0.5 to 4% by weight, preferably 0.5 to 1% by weight, of a pigment.

[0122] For example, the substrate 1 is made of brass, such as for forming a dial, and the light-absorbing coating according to the present invention is applied thereto. The brass substrate is, for example, 0.27 mm thick.

[0123] The undercoat 21 is applied to the brass substrate by dipping in a first liquid mixture consisting of 2 g of polyurethane resin (Berlacryl), 0.5 g of Emperor 1600 carbon black pigment, and 2.8 g of Berlaflex diluent. The layer is dried for 20 minutes to evaporate the diluent.

[0124] The first layer 22' is applied to the undercoat 21 through a first selective mask by dipping in a second liquid mixture consisting of 2 g of polyurethane resin (Berlacryl), 0.3 g of Living Ink pigment, and 3.5 g of Berlaflex diluent. The layer is dried for 20 minutes to evaporate the diluent.

[0125] The second layer 23’ is applied onto the primer coat 21 through a second selective mask by dipping in a third liquid mixture composed of 2 g of polyurethane resin (Berlacryl), 0.2 g of Norit A ultraE153 pigment, and 4 g of Berlaflex thinner. This layer is dried for 20 minutes to evaporate the thinner.

[0126] The third layer 24’ is applied onto the primer coat 21 through a third selective mask by dipping in a fourth liquid mixture composed of 2 g of polyurethane resin (Berlacryl), 0.2 g of Norit SX superE153 carbon pigment, 1.5 g of 90 - 150 μm glass beads, and 4 g of Berlaflex thinner. This layer is dried for 20 minutes to evaporate the thinner.

[0127] Such a coating 20’ is made to have a brass dial with a black surface coating and a luminance component L* of 16.

[0128] Third Exemplary Embodiment

[0129] Figure 3 A cross - sectional view schematically shows an article 10”, such as a third exemplary embodiment of a clock assembly, which includes a substrate 1 and a decorative coating 20” having visible - light absorption properties.

[0130] The coating 20” covers at least a portion of the substrate 1. Such a coating 20” according to the present invention forms a non - uniform structure comprising aggregates of pigments with different particle sizes. The coating 20” may include a plurality of stacked layers containing these pigment aggregates.

[0131] The density of the pigment aggregates between the respective layers of the coating 20” is also variable, preferably decreasing with an increase in the number of layers.

[0132] Except that the layer contains aggregates composed of pigments of various different particle sizes, the third exemplary structure of the coating 20” is substantially equivalent to the structure of the coating 20 described with reference to Figure 1 description.

[0133] The non - uniform structure of the coating 20” prevents reflection phenomena from occurring on the visible surface of the coating. The coating 20” also allows light to scatter in the non - uniform structure produced by different aggregates of pigments of different particle sizes and optionally by the density variations of these aggregates between the respective superimposed layers. As a result, light is captured as much as possible, leading to a high light absorption rate.

[0134] The coating 20” includes a primer coat 21 that forms a base layer and is configured to cover the substrate 1 at least on a portion of the substrate 1. This primer coat 21 is the same as the primer coat described previously with reference to Figure 1 description.

[0135] The primer coat 21 is at least partially covered by the first layer 22”. The first layer 22” can form part of a stack 25 of multiple layers stacked on top of one another, and the stack 25 at least partially covers the primer coat 21.

[0136] The first layer 22” is formed by depositing a formulation comprising a binder, aggregates of pigments dispersed in the binder, a solvent, and a coupling agent onto the primer coat 21.

[0137] Once the formulation has been applied to the primer coat 21, the solvent evaporates and the binder shrinks around the pigment aggregates, producing the first layer 22” of the coating 20”.

[0138] The first layer 22” consists of multiple pigment aggregates, and the pigment aggregates are composed of a mixture of pigments with different particle sizes.

[0139] Preferably, the first layer 22” consists of pigment aggregates composed of a mixture of pigments with a d90 percentile in the nanometer size range and pigments with a d90 percentile in the micrometer size range.

[0140] Preferably, the pigment aggregates of the first layer 22” consist of a central pigment in the micrometer size range, and multiple nanometer-sized pigments are chemically grafted (by the coupling agent of the formulation) onto the micrometer-sized central pigment, and the nanoscale pigments are coupled to the outer periphery of the central pigment.

[0141] The coupling agent will allow strong chemical interactions to occur between different pigments.

[0142] Optionally, the first layer 22” can contain a matting agent, such as nano-silica, to further enhance the strength of the coating 20”.

[0143] Preferably, the formulation for forming the first layer 22” contains 4 to 8 wt% of pigment aggregates in the formulation.

[0144] Preferably, the binder of the first layer 22” is a polymer, such as acrylic, epoxy polymer, or polyurethane. For example, the binder is the same as the binder in the primer coat 21.

[0145] For example, the first layer 22” is formed by applying a colored ink.

[0146] For example, the first layer 22” is formed by applying a black ink containing carbon black pigment.

[0147] For example, the coupling agent used to form the pigment aggregates in the formulation is a silane.

[0148] The first layer 22” is formed by sputtering, spraying, dipping, screen printing, printing, or pad printing the formulation onto the primer coat 21.

[0149] As Figure 3 shown in the example of Figure 3 , the coating 20” may include a second layer 23” that at least partially covers the first layer 22”. This second layer 23” forms the second layer of the stack 25, which may include multiple layers.

[0150] This second layer 23” is also composed of a plurality of pigment aggregates, which are composed of a mixture of pigments with different particle sizes.

[0151] Preferably, the second layer 23” is composed of pigment aggregates that are composed of a mixture of pigments with a d90 percentile in the nanometer size range and pigments with a d90 percentile in the micrometer size range.

[0152] Preferably, the pigment aggregates of the second layer 23” are composed of a central pigment in the micrometer size range, and a plurality of nanometer-sized pigments are chemically grafted onto the central pigment in the micrometer size range, and the nanometer-sized pigments are coupled to the outer periphery of the central pigment.

[0153] Preferably, the d90 percentile of the pigments in the aggregates of the second layer 23” is the same as the d90 percentile of the pigments in the aggregates that make up the first layer 22”.

[0154] Optionally, the second layer 23” may contain a matting agent, such as nano-silica, to further enhance the strength of the coating 20”.

[0155] Preferably, the formulation for forming the second layer 23” contains 1 wt% to 4 wt% of pigments in the formulation.

[0156] Preferably, the second layer 23” has a lower weight percentage of aggregates than the weight percentage of aggregates in the first layer 22”.

[0157] Preferably, the binder of the second layer 23” is a polymer, such as acrylic, epoxy polymer or polyurethane. Preferably, the binders in each layer of the stack 25 are the same.

[0158] For example, the second layer 23” is formed by applying a colored ink.

[0159] For example, the second layer 23” is formed by applying a black ink containing carbon black pigment.

[0160] The second layer 23” is formed by sputtering, spraying, dipping, screen printing, printing or pad printing the formulation onto the first layer 22”.

[0161] For example, the substrate 1 is made of brass, such as for forming a dial, and the light-absorbing coating 20” according to the present invention is applied thereto. The brass substrate is, for example, 0.27 mm thick.

[0162] The base coat 21 is applied to the brass substrate by dipping in a first formulation consisting of 2 g of polyurethane resin (Berlacry1), 0.5 g of Emperor 1600 carbon black pigment, and 2.8 g of Berlaflex thinner. The base coat 21 is dried for 20 minutes to evaporate the thinner.

[0163] The pigment aggregates constituting the second solution are pre-prepared from an isopropyl alcohol solution containing 5% of an organosilane (e.g., methoxysilane) suspending micron-sized and nano-sized pigments. The solution is dried and the aggregate powder is recovered.

[0164] The first layer 22” of the coating 20” is applied to the base coat 21 by dipping in a second formulation consisting of 2 g of polyurethane resin (Berlacryl), 0.3 g of the aggregate powder, and 2.8 g of Berlaflex thinner. The first layer 22” is dried for 20 minutes to evaporate the thinner.

[0165] Such a coating 20” is made to have a brass dial with a black surface coating and a brightness component L* of 16.

Claims

1. An article (10, 10', 10") comprising a substrate (1) and a multilayer coating (20, 20', 20") deposited on the substrate (1), the multilayer coating (20, 20', 20") being formed by combining a plurality of layers (21, 22, 22', 22", 23, 23', 23", 24, 24') comprising a binder and a pigment, the coating (20, 20', 20") comprising pigments of different particle sizes.

2. The article (10, 10', 10") according to claim 1, characterized in that The multi-layer coating (20, 20', 20") contains nano- and micro-sized pigments.

3. The article (10, 10', 10") according to claim 2, characterized in that The multi-layer coating (20, 20', 20") comprises glass beads.

4. The article (10, 10', 10") according to any one of claims 1 to 3, characterized in that The multi-layer coating (20, 20', 20") comprises a basecoat (21) covering at least a portion of the substrate (1), the basecoat (21) comprising a pigment having a d90 percentile of nanometer size.

5. The article (10) according to any one of claims 1 to 3, characterized in that The multilayer coating (20) comprises a stack (25) of a plurality of successive layers (22, 23, 24) superimposed on one another, which at least partially covers the base coating (21), each of the successive layers (22, 23, 24) of the stack (25) comprising a pigment having a d90 percentile different from the d90 percentile of the pigment in the layer it covers.

6. The article (10) according to claim 5, characterized in that Each of the successive layers (22, 23, 24) in the stack (25) comprises a pigment having a d90 percentile greater than the d90 percentile of the pigment in the layer it covers.

7. The article (10) according to claim 6, characterized in that Each layer (n) of the stack (25) has a pigment with a d90 percentile equal to n*k / 10 μm, where k is the similarity factor between the d90 percentiles of the pigments of two consecutive layers of the stack (25).

8. The article (10') according to any one of claims 1 to 3, characterized in that The multi-layer coating (20') comprises a plurality of layers (22', 23', 24') of different particle sizes, which are juxtaposed relative to each other and each cover a predetermined portion of the base coating (21).

9. The article (10') according to claim 8, characterized in that The size of the pigments in the multiple layers (22', 23', 24') covering the base coating (21) is in the micrometer range.

10. The article (10') according to claim 8, characterized in that The multi-layer coating (20') includes a first layer (22') at least partially covering a first portion of the base coating (21) and a second layer (23', 24') juxtaposed with the first layer (22') and at least partially covering a second portion of the base coating (21), the second portion being different from the first portion, and the pigment of the second layer (23', 24') having a d90 percentile greater than the d90 percentile of the pigment in the first layer (22').

11. Article (10") according to any one of claims 1 to 3, characterized in that The multi-layer coating (20") comprises a first layer (22") at least partially covering the base coating (21), wherein the first layer (22") comprises pigment aggregates composed of a mixture of pigments of different particle sizes.

12. The article (10") according to claim 11, characterized in that The first layer (22") comprises pigment aggregates consisting of a mixture of pigments having a d90 percentile of nanometer size and pigments having a d90 percentile of micrometer size.

13. The article (10") according to claim 11, characterized in that The pigment aggregates in the first layer (22") consist of a micron-sized central pigment to which a plurality of nanometer-sized pigments are chemically grafted at the periphery.

14. The article (10, 10', 10") according to any one of claims 1 to 3, characterized in that The binder of the multiple layers (21, 22, 22', 22", 23, 23', 23", 24, 24') of the multilayer coating (20, 20', 20") is a polymer.

15. The article (10, 10', 10") according to claim 14, characterized in that The adhesive of the multiple layers (21, 22, 22', 22", 23, 23', 23", 24, 24') of the coating (20, 20', 20") is acrylic, epoxy polymer or polyurethane.

16. The article (10, 10', 10") according to any one of claims 1 to 3, characterized in that The pigment of the multiple layers (21, 22, 22', 22", 23, 23', 23", 24, 24') of the multi-layer coating (20, 20', 20") is carbon black.

17. The article (10, 10', 10") according to any one of claims 1 to 3, characterized in that The multilayer coating (20, 20', 20") has a lightness component L* of less than 20.

18. The article (10, 10', 10") according to any one of claims 1 to 3, characterized in that The article is a timepiece component.

19. A timepiece (200), characterized in that It comprises a timepiece assembly according to claim 18 .

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