Plastic substrate coated with a black or rich black coating and identifiable by near-infrared spectroscopy

Abstract

The invention relates to a substrate (2) made of a plastic that can be identified by near-infrared spectroscopy, coated with a coating (3c), having a specific color lying within black or rich black, said coating (3c) comprising: - optionally a tie layer (5); - a finishing layer (4), if the coating (3c) comprises pigments, the weight content thereof: - does not exceed 10.00% for pigments from among black-colored metal oxides and perylene black, - does not exceed 1.14% for pigments chosen from carbon black, graphite and aniline black, and the thickness of the coating (3c) is between 3 μm and 30 μm.

Description

DESCRIPTION TITLE: Plastic material substrate coated with a black or deep black coating and identifiable by near-infrared spectroscopy

[0001] The present invention relates to a plastic material substrate of black or deep black color identifiable by near-infrared spectroscopy.

[0002] In the context of the present invention, the substrate can be any part made of plastic (or, in other words, polymeric) material with a thickness of at least 0.6 mm onto which a coating can be deposited. This may include parts obtained by injection molding or injection blow molding. Preferably, the substrate is packaging made of plastic material obtained by injection molding or injection blow molding. Most preferably, this is packaging for a cosmetic product.

[0003] Nowadays, for economic and environmental reasons, plastic packaging is increasingly being recycled.

[0004] To achieve this, waste sorting centers are generally equipped with machines that perform optical sorting using near-infrared spectroscopy. This technique uses wavelengths in the near-infrared range, specifically wavelengths between approximately 600 nm and approximately 2800 nm. More precisely, the sorting machine includes a near-infrared light emitter and a near-infrared light detector. It directs beams of near-infrared light onto the plastic items (for example, packaging) to be sorted, which are conveyed on a conveyor belt. Each piece of plastic to be sorted absorbs some of this emitted light and, more importantly, re-emits it within a range of near-infrared wavelengths that is characteristic of the specific plastic material from which the item is made.In other words, the range of wavelengths of light re-emitted by the part to be sorted constitutes its "spectroscopy signature" and can be easily compared to reference spectra, allowing for a quick, reliable, and certain determination of the plastic material from which the part to be sorted is made.

[0005] The black coloration of plastic parts can be achieved through the incorporation of dyes and / or pigments (such as carbon black). For example, carbon black may have been incorporated as an additive in the masterbatch of polymeric materials from which the plastic part to be sorted originates.

[0006] However, carbon black has the disadvantage of absorbing near-infrared radiation, making its identification by near-infrared spectroscopy difficult, if not virtually impossible, and therefore hindering the sorting of plastic materials from parts containing it. Furthermore, the use of carbon black is on the verge of being banned due to evolving regulations concerning chemical products.

[0007] This is why, in waste sorting centers, black plastic parts must be sorted using techniques other than near-infrared spectroscopy; which is not at all advantageous from an economic and logistical point of view.

[0008] To overcome the drawbacks of using carbon black to color plastic materials black, it has been proposed to replace carbon black with pigments that absorb less near-infrared radiation. Thus, oxides such as black iron oxide, chromium, and manganese, used alone or in mixtures, have been employed as additives in masterbatches to replace carbon black for coloring plastic materials throughout.

[0009] However, this alternative solution using other pigments has the following drawbacks: - problems with reproducibility and uniformity of the black coloring; - the desired black or deep black colour is not always obtained with polymers such as polyethylene (hereinafter abbreviated "PE"), as well as recycled polymeric raw materials such as recycled polyethylene terephalate (hereinafter abbreviated "PET").

[0010] This alternative solution is therefore not entirely satisfactory.

[0011] In view of the drawbacks of using carbon black and its alternatives—other pigments that absorb less near-infrared radiation than carbon black—the inventors of the present invention sought to develop an alternative technical solution for producing black or deep black plastic parts that could be quickly, reliably, and accurately sorted in recycling centers using near-infrared spectroscopy. To this end, the inventors of the present invention conceived the idea of ​​developing a coating that covers the surface of a plastic substrate in such a way that the coated substrate is black or deep black, and the plastic material can be identified by near-infrared spectroscopy as detailed above.

[0012] The invention thus relates to a substrate made of at least one plastic material that is identifiable by near-infrared spectroscopy, at least a portion of said substrate having a thickness of at least 0.6 mm and being coated wholly or partly with a coating characterized in that: the assembly consisting of at least a portion of said substrate and the coating has a specific color (in other words, a "target color") in the black or deep black range, and in that the coating comprises: - optionally at least one bonding coat; - at least one topcoat which is applied to the substrate or, where the coating includes at least one primer, said at least one topcoat is applied to said at least one primer, at least one of the coating layers includes at least one colouring agent selected from the group consisting of pigments and dyes, taken alone or in mixtures thereof, if the coating includes pigments, the mass content of said pigments, expressed in relation to the total mass of the coating: - does not exceed 10.00%, preferably not exceeding 6.50%, when it comes to selected pigments among the black metallic oxides and perylene black, - does not exceed 1.14%, preferably does not exceed 1.00%, when it comes to pigments chosen from carbon black, graphite and aniline black, the thickness of said coating is between 3 pm and 30 pm.

[0013] In the context of the present invention, "pigments" means colored particles.

[0014] In the context of the present invention, among the various types of pigments that exist, "near-infrared absorbing pigments" refers to pigments that can absorb near-infrared rays totally or partially. In other words, the expression "near-infrared absorbing pigments" can refer to pigments that partially absorb near-infrared rays as well as pigments that completely absorb near-infrared rays. In the context of the present invention, "partially absorbing near-infrared rays" is the opposite of "totally absorbing near-infrared rays." Thus, in the context of the present invention, pigments that partially absorb near-infrared rays mean that they absorb a portion of the infrared rays, even a very small portion.

[0015] The absorption of pigments by near-infrared rays can be determined using spectrometric measurements of pigment absorbance at wavelengths in the near-infrared range. This determination is perfectly within the capabilities of a person skilled in the art.

[0016] Among the different kinds of pigments that exist, a person skilled in the art is perfectly capable of selecting pigments that do not absorb near-infrared rays, pigments that partially absorb near-infrared rays, and pigments that totally absorb near-infrared rays.

[0017] It is thus perfectly known to the man of the trade that examples of pigments which totally absorb near-infrared rays include carbon black, graphite and aniline black (namely a synthetic azinic pigment).

[0018] It is also well known to those skilled in the art that examples of pigments that partially absorb near-infrared radiation include black metallic oxides (e.g., black iron oxide, manganese oxide, or chromium oxide). Perylene black (a synthetic organic pigment) is another example.

[0019] In other words, pigments that absorb near-infrared radiation are distinguished from one another by their ability to absorb near-infrared radiation based on their concentration. For example, a smaller quantity (or concentration) of carbon black is required than black iron oxide to absorb the same amount of near-infrared radiation.

[0020] Thus, within the framework of the present invention, it is essential that if the coating comprises pigments, their mass content expressed in relation to the total mass of said coating must not exceed: - 10.00%, preferably 6.50%, when it comes to pigments chosen from black metallic oxides and perylene black, namely pigments that partially absorb near-infrared rays, - 1.14%, preferably 1.00%, when it comes to pigments chosen from carbon black, graphite and aniline black, namely pigments that totally absorb near-infrared rays.

[0021] This maximum content combined with a coating thickness that must be between 3p and 30 pm makes it possible to identify by near-infrared spectroscopy the plastic material which, once coated with said coating, has a black or deep black color appearance.

[0022] In one embodiment of the invention, the coating may comprise pigments selected from carbon black, graphite and aniline black, namely pigments totally absorbing rays in the near-infrared, the mass content of which, expressed as a percentage of the total mass of the coating, may be between 0.05% and 1.14%, preferably between 0.08% and 1.00%.

[0023] In one embodiment of the invention, the coating may comprise pigments selected from black metallic oxides and perylene black, namely pigments partially absorbing rays in the near-infrared, the mass content of which, expressed in relation to the total mass of the coating, may be between 2.00% and 10.00%, preferably between 2.00% and 6.50%.

[0024] In the context of the present invention, "colorants" means colored substances soluble in the medium in which they are incorporated (for example, a colored topcoat, primer or undercoat formulation as detailed below).

[0025] The mass content of the colorants, expressed in relation to the total mass of the coating, can be between 0.01% and 3.50%, preferably between 0.08% and 3.30%.

[0026] The determined color, or in other words the target color of the assembly consisting of the substrate and the coating, can range from black to deep black (also known as "piano black").

[0027] Black results from the total or near-total absorption of visible light, as well as light in the infrared and near-infrared ranges. Deep black is a very intense black that reflects very little received radiation.

[0028] In general, colors are defined and characterized within the CIELAB color space (also known as "CIE L*a*b*"). A glossy finish will always be perceived as more intense (deeper) than a satin or matte finish. Deep, glossy blacks have lightness (L*) values ​​below 5%, corresponding to a light reflectance of less than 0.1%, which is too low for accurate characterization. Therefore, other parameters have been developed to better characterize black and deep blacks.

[0029] Among these parameters is the blackness parameter (abbreviated "My"), which determines only the brightness of a sample without taking into account the color shade. From a A value of 200 is described as black, and above 300 it is described as "deep black".

[0030] In this regard, the article, in German entitled "Schwarz - der feine Unterschied" (translating as "Black - the ultimate difference") by Kai Krauss et al., published in January 2019 in the journal Farbe und Lack, precisely defines this parameter of blackness to characterize the colours black and deep black.

[0031] The blackness My can be determined according to the DIN 55979 standard.

[0032] Thus, the whole consisting of the part of the substrate coated with the coating has a determined color that is in the black or deep black, that is to say whose blackness My is greater than or equal to 200.

[0033] The determined color of the entire assembly, consisting of the portion of the substrate coated with the coating that lies in black or deep black, is obtained by: - a selection of a plastic substrate material having a certain original color (in other words, the color of the plastic material in the absence of the coating) which is combined with - a suitable selection of a coating with a thickness between 3 µm and 30 µm, containing colorants and / or pigments in specific quantities such that the mass content in said coating does not exceed 1.14% for pigments selected from carbon black, graphite, and aniline black (i.e., pigments that totally absorb infrared radiation), and 10.00% for pigments selected from black metal oxides and perylene black (i.e., pigments that partially absorb infrared radiation), if such pigments are present in said coating. These selections of the plastic material, colorants, and pigments are perfectly within the capabilities of a person skilled in the art, with a view to producing a plastic substrate coated with a black or deep black coating.

[0034] At least one plastic material in the substrate is identifiable by near-infrared spectroscopy. It may advantageously be selected from polyethylene (hereinafter abbreviated as "PE"), polyethylene terephthalate (hereinafter abbreviated as "PET"), high-density PE, low-density PE, polypropylene, polystyrene, polyamide, acrylonitrile butadiene styrene, ethylene vinyl acetate, styrene acrylonitrile, polymethyl methacrylate, styrene methyl methacrylate, and polyethylene terephthalate glycol. The plastic material may also be one of the bio-based polymers, namely polylactic acid, polyhydroxyalkanoate, or polyhydroxybutyrate. This plastic material may be one of these polymers, alone or in a mixture thereof.

[0035] It can be virgin plastic material or recycled plastic material (e.g., mechanically or chemically recycled).

[0036] Advantageously, said plastic material of the substrate has as such (i.e. in the absence of the coating) a color close to the determined color of the whole consisting of the substrate and the coating.

[0037] In the context of the present invention, "close color" means that the plastic material of the substrate can have a color having a blackness value My of at least 130. For example, it may be a color described as grey to the naked eye.

[0038] The plastic substrate may have been colored throughout.

[0039] However, unlike the state of the art, the black or deep black coloration of the assembly consisting of the substrate and the coating does not result solely from a coloration in the mass of the substrate but is mainly obtained thanks to the coating specifically designed so that the plastic material of the substrate can be identified by near-infrared spectroscopy.

[0040] In addition to the fact that, thanks to a coating specifically designed to make the assembly consisting of at least a portion of the coated substrate appear black or deep black to the naked eye, and to allow the plastic material to be identified by near-infrared spectroscopy, the present invention also offers the advantage that said coated substrate can be perfectly recycled after grinding. Indeed, while it may contain pigments that could be subject to current or future regulatory restrictions (in particular, pigments that absorb near-infrared rays such as carbon black, as mentioned above), these pigments are present in very small quantities and therefore below the acceptable threshold values ​​for recycling ground plastic materials containing such pigments.In other words, the quantities of these pigments subject to regulatory restrictions which are implemented in the coating of the present invention are so minute that said pigments are not likely to constitute a source of pollution of the plastic material of the substrate which has been coated with such a coating and thus do not hinder the recycling of said plastic material.

[0041] The portion of the substrate coated with the coating has a thickness of at least 0.6 mm. In one embodiment of the invention, said thickness may be between 0.6 mm and 6 mm. Thus, within the scope of the present invention, at least one portion of the substrate that is coated with a coating has a certain thickness and is clearly distinct from a film.

[0042] The present invention differs from a film (for example a flexible film) which is coated with a coating.

[0043] Advantageously, at least a portion of the substrate that is coated may have a Young's modulus between 0.4 GPa and 5 GPa. In other words, at least a portion of the substrate with a thickness of at least 0.6 mm and coated with a material exhibits a certain rigidity. The Young's modulus can be determined according to ISO 527.

[0044] The thickness of the part of the substrate that is coated with the coating may be the same over all of said part of said substrate or it may vary within said part of said substrate.

[0045] In one embodiment of the invention, the entire substrate has a thickness of at least 0.6 mm (for example between 0.6 mm and 6 mm) and the coating is present on the entire substrate.

[0046] In one embodiment of the invention, the entire substrate has a thickness of at least 0.6 mm (for example between 0.6 mm and 6 mm) and the coating is present on a part of said substrate.

[0047] In one embodiment of the invention, a portion of the substrate has a thickness of at least 0.6 mm (for example, between 0.6 mm and 6 mm) and the coating is present on a portion of this portion of the substrate which has a thickness of at least 0.6 mm (for example, between 0.6 mm and 6 mm).

[0048] In one embodiment of the invention, a portion of the substrate has a thickness of at least 0.6 mm (for example, between 0.6 mm and 6 mm) and the coating is present over the entirety of this portion of the substrate, which has a thickness of at least 0.6 mm (for example, between 0.6 mm and 6 mm).

[0049] As explained above, the coating includes dyes and / or pigments. If the coating includes pigments, their mass percentage relative to the total mass of the coating has been selected so that it does not exceed: - 1.14%, preferably 1.00%, when it comes to pigments chosen from carbon black, graphite and aniline black, namely pigments that totally absorb near-infrared rays, - 10.00%, preferably 6.50%, when it comes to pigments chosen from black metallic oxides and perylene black, namely pigments partially absorbing near-infrared rays, so that the plastic material of the substrate can be identified by near-infrared spectroscopy.

[0050] In an embodiment of the invention in which the coating comprises as a coloring agent only pigments selected from black metallic oxides, perylene black, carbon black, graphite and aniline black, namely pigments totally or partially absorbing near-infrared rays, the thickness of said coating is advantageously between 5 pm and 25 pm.

[0051] In an embodiment of the invention in which the coating comprises only dyes as a coloring agent, the thickness of said coating is advantageously between 10 pm and 28 pm.

[0052] In other words, when the coating consists only of pigments, its thickness can advantageously be slightly thinner than when it consists only of dyes.

[0053] In one embodiment of the invention, the coating may further comprise at least one colored basecoat (also referred to in English as a "basecoat") which is disposed between the substrate and at least one topcoat, or, where the coating comprises at least one tack coat, said at least one colored basecoat is disposed between the at least one tack coat and the at least one topcoat. The at least one colored basecoat contributes to the color of the coating applied to the plastic substrate.

[0054] At least one colored underlayer may include dyes and / or pigments.

[0055] At least one coloured undercoat is obtained, after application (for example by spraying) onto the plastic material substrate or, where appropriate, onto at least one tack coat when the coating includes such at least one tack coat, of a coloured undercoat formulation designed for coating a plastic material substrate and perfectly within the grasp of a person skilled in the art, followed by drying (for example, drying under infrared rays, under hot air convection or at room temperature), and then cross-linking under ultraviolet rays.

[0056] The thickness of at least one colored underlayer can be between 5 pm and 12 pm, preferably between 7 pm and 10 pm.

[0057] In the context of the present invention, "topcoat" means a varnish or lacquer coating which is obtained, after application (for example by spraying) onto the plastic material substrate or, where applicable, onto the tack coat when the coating includes such a tack coat or onto the colored undercoat when the coating includes such a colored undercoat, of a varnish or lacquer formulation designed for coating a plastic material substrate and perfectly within the grasp of a person skilled in the art, followed by drying (for example, drying under infrared rays, under hot air convection or at room temperature), and then cross-linking under ultraviolet rays.

[0058] The thickness of at least one finishing layer may be between 3 pm and 22 pm, preferably between 3 pm and 20 pm, more preferably between 3 pm and 14 pm, even more preferably between 5 pm and 10 pm.

[0059] At least one topcoat can be coloured or colourless.

[0060] Besides the possible coloring when it contains pigments and / or dyes, the said finishing layer mainly provides resistance to the coating, in particular scratch resistance.

[0061] When the topcoat is a varnish, that varnish can be colored or colorless. If it's a colored varnish, it may contain colorants. If it's a colorless varnish, it contains no colorants. The varnish is transparent, meaning it's possible to see through it.

[0062] When the topcoat is a colorless varnish layer, its thickness is advantageously less than 20 pm.

[0063] When the topcoat is a lacquer layer, that lacquer layer is colored. The lacquer layer contains pigments, including opacifying pigments (for example, carbon black, aniline black, and black iron oxide) and optionally colorants. Unlike a varnish layer, the lacquer layer is therefore opaque. Indeed, all or Part of the pigments it contains limit the passage of light and make the topcoat opaque to the human eye.

[0064] Due to the absence of pigments, a layer of varnish is more resistant (especially scratch-resistant) than a layer of lacquer.

[0065] Any scratches will be more visible in a colored varnish layer than in a clear varnish layer. Therefore, it is advantageous for the coating to include a colored primer and / or undercoat, as well as a clear varnish topcoat. The clear varnish layer provides scratch resistance, and any scratches will be less noticeable than if the varnish layer were colored.

[0066] In the context of the present invention, "adhesion layer" means a layer of the coating which is designed to facilitate adhesion to the substrate of the topcoat or, where the coating includes a coloured undercoat, to facilitate adhesion of said coloured undercoat.

[0067] At least one primer coat is obtained after applying (for example, by spraying) a primer formulation designed for coating a plastic substrate and readily applicable by a person skilled in the art, followed by drying (for example, by drying under infrared light, hot air convection, or at ambient temperature). To aid the formation of a film that can be coated with a topcoat or a colored undercoat and then a topcoat, the primer coat may contain hardeners. The presence of these hardeners also has the advantage of reducing the drying time of the primer coat, since these hardeners react under the action of heat (for example, under infrared light or hot air convection).

[0068] The thickness of at least one tack coat may be between 1 pm and 12 pm, preferably between 1 pm and 10 pm, more preferably between 1 pm and 5 pm, even more preferably between 1 pm and 3 pm.

[0069] At least one bonding layer may be colored or colorless. The bonding layer may include dyes and / or pigments.

[0070] As explained above, the substrate can be any part made of plastic (or, in other words, polymer) material. This can include parts produced by injection molding or injection blow molding. Preferably, the substrate is plastic packaging produced by injection molding or injection blow molding. Most preferably, this is packaging for a cosmetic product.

[0071] Different embodiments of substrates coated with a coating according to the invention are now described.

[0072] In a 1 erAccording to the embodiment of the invention, the coating comprises at least one colored topcoat which is disposed on the substrate. The colored topcoat is a layer of lacquer or a layer of colored varnish as described above in the description of the layer of finishing. In this 1 er In this embodiment of the invention, the coating may comprise one or more finishing layers, at least one of which is colored.

[0073] In a 2 ème In an embodiment of the invention, the coating comprises: - at least one coloured or colourless bonding layer that is placed on the substrate; - at least one colored or colorless topcoat that is applied over said colored or colorless primer. In this 2 èmeIn this embodiment of the invention, the coating may comprise one or more bonding layers, as well as one or more coloured or colourless finishing layers.

[0074] In a 3 ème In an embodiment of the invention, the coating comprises: - at least one coloured or colourless bonding layer that is placed on the substrate; - at least one coloured undercoat which is placed on said at least one colourless or coloured bonding coat; - at least one coloured or colourless topcoat which is placed on said at least one coloured undercoat.

[0075] In this 3 ème In this embodiment of the invention, the coating may comprise one or more bonding layers, one or more coloured undercoats, and one or more coloured or colourless topcoats.

[0076] In a 4 èmeIn an embodiment of the invention, the coating comprises: - at least one colored underlayer which is placed on the substrate; - at least one coloured or colourless topcoat which is placed on said at least one coloured undercoat.

[0077] In this 4 ème In this embodiment of the invention, the coating may comprise one or more colored undercoats, as well as one or more colored or colorless topcoats.

[0078] In these 4 embodiments of the invention, the bonding layer, the colored undercoat and the finishing layer may have the technical characteristics that have been described above.

[0079] The invention also relates to a method for manufacturing a plastic material substrate coated with a coating according to the invention and as described above; said manufacturing method is characterized in that it comprises at least the following steps: 1) We have a substrate made of plastic material identifiable by near-infrared spectroscopy, 2) Optionally, at least one tack coat formulation is applied to the substrate to obtain at least one tack coat, or at least one coloured undercoat formulation is applied to the substrate to obtain at least one coloured undercoat, or at least one tack coat formulation is applied to the substrate to obtain at least one tack coat, and then at least one coloured undercoat formulation is applied to said at least one tack coat to obtain at least one coloured undercoat, 3) at least one topcoat formulation is applied to the substrate, where appropriate when the coating includes at least one tack coat and is without a coloured undercoat, at least one topcoat formulation is applied to said at least one tack coat, where appropriate when the coating includes at least one coloured undercoat, at least one topcoat formulation is applied to said at least one coloured undercoat, the application of at least one topcoat being followed by a crosslinking step under ultraviolet rays so as to obtain said substrate coated with a coating.

[0080] The formulations of at least one topcoat and the optional layers, namely at least one bonding coat and at least one coloured undercoat, are perfectly within the reach of a person skilled in the art and are chosen appropriately so that the coating thus obtained has the technical characteristics as detailed above.

[0081] Advantageously, prior to optional steps 2 and 3, the plastic substrate undergoes surface treatment. This surface treatment may consist of flame treatment, plasma treatment, or corona treatment. The surface treatment increases the surface tension of the plastic substrate, providing adequate wettability for the application of a primer, a colored undercoat, or a topcoat, thus ensuring good adhesion of the coating to the substrate.

[0082] Advantageously, the applications of the tack coat, colored undercoat and topcoat formulations are carried out by spraying.

[0083] Advantageously, after each application (preferably by spraying) of a primer, colored undercoat, or topcoat formulation, a drying process is carried out. This allows for desolvation. In other words, it removes the solvents present in these primer, colored undercoat, or topcoat formulations. Drying can be performed under infrared light, with hot air (for example, in an oven), or at ambient temperature.

[0084] The execution of steps 2) and 3) of the manufacturing process according to the invention is perfectly within the reach of a person skilled in the art, as they correspond to steps usually implemented during the coating of a substrate with plastic material.

[0085] In step 3) of the manufacturing process according to the invention, cross-linking is carried out under ultraviolet rays. This allows the topcoat and the optional colored undercoat to be cross-linked simultaneously.

[0086] The originality of the manufacturing process according to the invention lies in the appropriate choice of formulations of the bonding layer, coloured undercoat and topcoat so that the coating has the technical characteristics as described above and which are essential for obtaining a substrate in plastic material coated with this coating in black or deep black colour and whose plastic material can be identified by near-infrared spectroscopy.

[0087] The invention will be better understood with the aid of the detailed description set forth below with reference to the attached drawing representing, by way of non-limiting example, embodiments of substrates coated with a coating according to the invention.

[0088] Figure 1 is a schematic cross-sectional view of a 1 er method of embodiment of a substrate coated with a coating according to the invention.

[0089] Figure 2 is a schematic cross-sectional view of a 2 ème method of embodiment of a substrate coated with a coating according to the invention.

[0090] Figure 3 is a schematic cross-sectional view of a 3 ème method of embodiment of a substrate coated with a coating according to the invention.

[0091] Figure 4 is a schematic cross-sectional view of a 4 ème method of embodiment of a substrate coated with a coating according to the invention.

[0092] Figure 1 shows a schematic cross-sectional view of a 1 er A method of embedding a plastic material substrate 2 coated with a coating 3a according to invention 1a. The coating 3a comprises a colored topcoat 4 which is disposed on the substrate 2. The topcoat 4 may be a lacquer layer or a colored varnish layer as described above in the description of the topcoat. As explained above, if the topcoat 4 is a lacquer layer, said lacquer layer 4 comprises opacifying pigments and optionally dyes, said opacifying pigments being pigments that absorb or do not absorb near-infrared rays. If the topcoat 4 is a colored varnish layer, said varnish layer comprises dyes.

[0093] Figure 2 shows a schematic cross-sectional view of a 2 èmeA method for embodying a plastic material substrate 2 coated with a coating 3b according to invention 1b. The coating 3b comprises: - an adhesion layer 5 which is placed on the substrate 2; - a finishing layer 4 which is placed on said bonding layer 5.

[0094] The tack coat 5 is a tack coat as described above in the tack coat description. It may be colorless or colored. If tack coat 5 is colored, it includes dyes and / or pigments, which may or may not absorb near-infrared radiation.

[0095] The finishing layer 4 of the 2 ème The embodiment of the invention may be colored or colorless. If the finishing layer 4 of this 2 ème If the embodiment of the invention is colored, it can have the same technical characteristics as those of the finishing layer 4 of the 1 erembodiment of the invention described above. If the top layer 4 of this 2 ème the embodiment of the invention is colorless, it is a layer of colorless varnish.

[0096] If in this 2 ème In this embodiment of the invention, the tack coat 5 is a colorless tack coat, the top coat 4 is colored and it can have the technical characteristics described just above.

[0097] If in this 2 èmeIn this embodiment of the invention, the primer 5 is a colored primer, and the topcoat 4 can be colored or colorless. It can thus exhibit the technical characteristics described above, depending on whether it is a colored or colorless topcoat 4. Advantageously, the topcoat 4 is colorless. It is therefore preferably a colorless varnish layer. This has the advantage that the coating 3b has a scratch-resistant topcoat 4, and any scratches will be less visible than if the varnish layer were colored.

[0098] Figure 3 shows a schematic cross-sectional view of a 3 ème A method for embodying a plastic material substrate 2 coated with a coating 3c according to invention 1c. The coating 3c comprises: - an adhesion layer 5 which is placed on the substrate 2; - a colored undercoat 6 which is placed on said bonding layer 5; - a finishing layer 4 which is placed on said underlayer 6.

[0099] The tack coat 5 is a tack coat as described above in the tack coat description. It can be colorless or colored. If tack coat 5 is colored, it includes dyes and / or pigments; these pigments may or may not absorb near-infrared radiation.

[0100] The colored undercoat 6 is a colored undercoat as described above in the description of the colored undercoat. It is colored to enhance the color of the coating 3c. It comprises dyes and / or pigments, said pigments either absorbing or not absorbing near-infrared rays.

[0101] The finishing layer 4 of the 3 èmeThe embodiment of the invention may be colored or colorless and may thus have technical characteristics identical to those of the topcoat 4 of the 2 ème embodiments of the invention that have been described above. The finishing layer 4 of the 3 ème The method of application can be a layer of lacquer or a layer of colorless or colored varnish. Preferably, the finishing layer 4 of the 3 ème An embodiment of the invention is a layer of colorless or colored varnish, and more preferably a layer of colorless varnish. This has the advantage that the coating 3c has a scratch-resistant topcoat 4, and any scratches will be less visible than if the varnish layer were colored.

[0102] Figure 4 shows a schematic cross-sectional view of a 4 èmeA method for embodying a plastic material substrate 2 coated with a 3D coating according to invention 1d. The 3D coating comprises: - a colored underlayer 6 which is placed on the substrate 2; - a finishing layer 4 which is placed on the said underlayer 6.

[0103] The colored undercoat 6 is a colored undercoat as described above in the description of the bonding coat. It may have technical characteristics identical to those of 3. ème embodiment of the invention and which have been described above.

[0104] The fourth finishing layer of the fourth ème The embodiment of the invention may be colored or colorless and may thus have technical characteristics identical to those of the finishing coats 4 of the 2 ème and 3 ème embodiments of the invention that have been described above. The finishing layer 4 of the 4 èmeThe method of application can be a layer of lacquer or a layer of colorless or colored varnish. Preferably, the finishing coat 4 of 4 ème An embodiment of the invention is a layer of colorless or colored varnish, and more preferably a layer of colorless varnish. This has the advantage that the 3D coating has a scratch-resistant top layer, and any scratches will be less visible than if the varnish layer were colored.

[0105] EXPERIMENTAL SECTION

[0106] The following experiments were carried out.

[0107] A - Coatings composed of a lacquer finish layer

[0108] 8 lacquer compositions (namely compositions A1 to A8) comprising the following components: - a basic formulation of colorless lacquer; - a thinner; - a lacquer coloring formulation which comprised 5% by mass of carbon black, said mass percentage of 5% being expressed in relation to the mass of said formulation, were prepared.

[0109] The basic lacquer formulation was a basic lacquer formulation classically used for application on plastic substrates.

[0110] The thinner was a thinner commonly used to dilute lacquer formulations applied to plastic substrates.

[0111] The lacquer coloring formulation that included 5% by mass of carbon black was a formulation classically used to color lacquer black.

[0112] Table 1 below details, for each of the compositions A1 to A8, the mass percentages of the basic lacquer formulation and the lacquer coloring formulation, these mass percentages being expressed in relation to the sum of the masses of the basic lacquer formulation and the lacquer coloring formulation. Table 1

[0113] The quantity of thinner used in each of these compositions A1 to A8 was adjusted by the operator at the time of application of these compositions A1 to A8 on plastic substrates as detailed below in order to ensure proper application of said compositions and good coverage of the coating on the plastic substrate.

[0114] A-1: Experiments at the same coating thickness of 13 µm + / - 2 µm

[0115] First, each of the compositions A2 to A8 was spray-applied to the surface of a high-density polyethylene (HDPE) substrate, hereinafter referred to as "HDPE," with a rectangular shape and dimensions of 8 cm x 5 cm x 0.2 cm, to form a layer 13 µm ± 2 µm thick on said substrate. Next, the resulting layers were first dried in a hot air oven. After drying, the layers were cured by exposure to ultraviolet light to obtain seven substrates coated with a topcoat consisting of a lacquer layer, hereinafter referred to as Tests A-1-1 to A-1-7.

[0116] The blackness (My) of substrates A2 to A8 was determined according to the DIN 55979 standard.

[0117] Table 2 below summarizes, for Tests A-1-1 to A-1-7, the blackness value (My) and whether substrate identification by near-infrared spectroscopy was successful ("OK") or not ("not OK") by comparing the near-infrared spectra obtained for these Tests A-1-1 to A-1-7 with a near-infrared reference spectrum of HDPE. The 1 ère column of table 2 indicates the mass content of carbon black in the lacquer layer (in other words the coating) thus obtained. Table 2

[0118] In view of the results detailed in Table 2, it can be noted that increasing the carbon black content in the coating increases the blackness of the substrates thus coated and that at a mass content of 1.15% carbon black, the coated substrate is no longer identifiable by near-infrared spectroscopy.

[0119] A-2: Experiments with increasing coating thicknesses and a fixed carbon black content

[0120] Composition A1 was spray-applied to the surface of the same substrate as for the experiments in point A-1 above, but in two different thicknesses (10 µm and 18 µm). The two substrates thus coated with a finish layer of colored varnish, hereinafter referred to as "Tests A-2-1 and A-2-2", was carried out in the same manner as for the experiments of point A-1 above.

[0121] Composition A2 was spray-applied to the surface of the same substrate as for tests A-1, but in three different thicknesses (6 µm, 13 µm, and 16 µm). The fabrication of the three substrates thus coated with a lacquer layer, hereinafter referred to as Tests A-2-3 to A-2-5, was carried out in the same manner as for the experiments in point A-1 above.

[0122] Composition A3 was spray-applied to the surface of the same substrate as for the experiments in section A-1 above, but in two different thicknesses (9 µm and 14 µm). The fabrication of the two substrates thus coated with a lacquer layer, hereinafter referred to as Tests A-2-6 and A-2-7, was carried out in the same manner as for the experiments in section A-1 above.

[0123] Table 3 below summarizes, for Tests A-2-1 to A-2-7, the blackness value (My) and whether substrate identification by near-infrared spectroscopy was successful ("OK") or not ("not OK") by comparing the near-infrared spectra obtained for these Tests A-2-1 to A-2-7 with a near-infrared reference spectrum of HDPE. The 1 ère Column 3 of Table 3 shows the mass percentages of carbon black in the coating. Column 2 èmeColumn 3 of table shows the thickness of the coating. Table 3

[0124] In view of the results detailed in Table 3 above, it can be noted that at the same mass content of carbon black in the coating, the thickness of said coating does not have a significant impact on the blackness.

[0125] B - Coatings composed of a primer layer comprising carbon black and black iron oxide and a topcoat of colorless varnish

[0126] A B1 bonding layer composition comprising the following components: - a black-coloured tack coat formulation that contained between 10% and 20% by mass of black-coloured iron oxide; - a thinner; - a hardener; - a colorant formulation of the tack coat formulation which included 5% by mass of carbon black, was prepared.

[0127] The tack coat formulation was a formulation classically used to obtain a tack coat for a plastic substrate.

[0128] The thinner was a thinner typically used to dilute a tack coat formulation as described above.

[0129] The color formulation of the tack coat formulation that included 5% by mass of carbon black was a formulation classically used to color a tack coat formulation black.

[0130] Table 4 below details for composition B1 the mass percentages of the tack coat formulation, the hardener and the tack coat colour formulation, these mass percentages being expressed in relation to the sum of the masses of the tack coat formulation, the hardener and the tack coat colour formulation. Table 4

[0131] The quantity of thinner used in composition B1 was adjusted by the operator at the time of application of said composition B1 to plastic substrates as detailed below in order to ensure proper application of said compositions and good coverage of the coating on the plastic substrate.

[0132] Composition B1 was sprayed onto the surface of an HDPE substrate identical to that used in experiments at point A above, so as to form a 1 ère a layer of the thickness defined in Table 5 below on said HDPE substrate. Then, the layers thus obtained were dried in a hot air oven.

[0133] Following this drying period, a colorless varnish composition was sprayed onto the surface of the layers thus obtained from composition B1 in order to form a 2 èmelayer of a thickness as defined in Table 5 below on said 1 ère layer. Then, the 2 èmes The resulting layers were dried in a hot air oven. Following this drying, the 2 èmes The layer was cross-linked by exposure to ultraviolet rays to obtain 4 substrates coated with a composite coating: - of a 1 ère layer called tack coat; - of a 2 ème layer called clear varnish topcoat, and hereafter referred to as Tests B-1 to B-4.

[0134] Table 5 below summarizes, for Tests B-1 to B-4, the thicknesses of the 1 ère and 2 ème layers, total coating thickness, blackness value (My), mass content of carbon black expressed relative to the total mass of the coating considered and whether the substrate identification by near-infrared spectroscopy could be carried out ("OK") or not ("not OK"). Table 5

[0135] Based on the detailed results in Table 5 above, we note that: - the HDPE substrate can be identified by near-infrared spectroscopy, with a coating thickness between 6 pm and 25 pm; - by comparing the blackness of tests B-1 and B-3 on the one hand and tests B-2 and B-4 on the other hand, the thickness of the primer layer has no impact on the blackness.

[0136] C - Coatings composed of a bonding layer comprising black iron oxide and a topcoat of colorless varnish

[0137] A C1 composition was prepared which included the following components: - a black-coloured tack coat formulation that contained between 10% and 20% by mass of black-coloured iron oxide; - a thinner; - a hardener.

[0138] Table 6 below details for composition C1 the mass percentages of the tack coat formulation and the hardener, these mass percentages being expressed in relation to the sum of the masses of the tack coat formulation and the hardener. Table 6

[0139] The quantity of thinner used in composition C1 was adjusted by the operator at the time of application of said composition C1 to plastic substrates as detailed below in order to ensure proper application of said compositions and good coverage of the coating on the plastic substrate.

[0140] The tack coat formulation, thinner and hardener were identical to those used in the experiments at point B above.

[0141] Composition C1 was sprayed onto the surface of 3 HDPE substrates identical to those used in experiments A and B above to form a 1 ère a 5 µm thick layer on said HDPE substrate. Then, the 3 layers thus obtained were dried in a hot air oven.

[0142] After this drying period, the same colorless varnish composition as that used in the experiments at point B above was sprayed onto the surface of these 3 layers thus obtained from composition C1 in order to form a 2 ème layer of a thickness as defined in Table 7 below on said 1 ère layer. Then, the 2 èmes The resulting layers were dried in a hot air oven. Following this drying process, the two èmesThe layers were cross-linked by exposure to ultraviolet rays to obtain 3 substrates coated with a composite coating: - of a 1 ère layer called tack coat; - of a 2 ème layer called clear varnish topcoat, and hereafter referred to as Tests C-1 to C-3.

[0143] Table 7 below summarizes, for Tests C-1 to C-3, the thickness of the 1 ère layer and each of the 2 èmes layers, the total coating thickness, as well as the blackness value (My) and whether the substrate identification by near-infrared spectroscopy could be carried out ("OK") or not ("not OK"). Table 7

[0144] In Table 7 above, "OK limit" means that the identification of the plastic material by near-infrared spectroscopy is not totally reliable.

[0145] Based on the detailed results in Tables 6 and 7 above, we note that: - by comparing the blackness values ​​of tests B-1 and C-1 on the one hand and tests B-2 and C-2 on the other hand, the presence of carbon black in the adhesion layer makes it possible to intensify the black (in other words to increase the blackness); - the thickness of the colorless varnish topcoat is advantageously less than 20 pm so as not to make the coating opaque to near-infrared rays in order to be able to properly identify the plastic material of the coated substrate by near-infrared spectroscopy.

[0146] D- Coatings consisting of a primer coat containing a colorant and a topcoat of colorless varnish or containing a colorant

[0147] 6 compositions (namely compositions D1 to D6) comprising the following components: - a ready-to-use tack coat formulation for coating plastic material substrates; - a 1 ère solution or a 2 ème black colour solution comprising black dyes and designed to colour a ready-to-use tack coat formulation, were prepared according to the mass percentages, expressed relative to the total mass of the composition considered, which are detailed in Table 8 below.

[0148] The ready-to-use tack coat formulation for coating plastic material substrates was a formulation classically used to obtain a tack coat for a plastic material substrate.

[0149] The 1 ère and 2 èmeBlack color solutions were designed to color a ready-to-use tack coat formulation. They were pigment-free. They contained black dyes, namely substances soluble in the ready-to-use tack coat formulation. The dry extract of these black dyes ranged from 0.1% to 10% in these solutions. ère and 2 ème solutions. The 2 ème the black colour solution was twice as concentrated in black dyes as the 1 ère black color solution. Table 8

[0150] Compositions D1 and D6 were sprayed onto the surface of a black-tinted HDPE substrate of the same geometric shape and dimensions as the substrate used in experiments A to C above, so as to form a 1 èrea 3 µm thick layer on said black-tinted HDPE substrate. Then, the resulting layer was dried in a hot air oven.

[0151] Following this drying, composition B6, as described in point B above, was sprayed onto the surface of the layers thus obtained from compositions D1 and D6 in order to form 2 èmes layers with a thickness of 14 pm on said 1 ère layer. Then, the 2 èmes The resulting layers were dried in a hot air oven. Following this drying process, the two èmes The layers were cross-linked by exposure to ultraviolet rays to obtain substrates coated with a composite coating: - of a 1 ère layer called coloured tack coat; - of a 2 ème layer called clear varnish topcoat, and hereinafter respectively designated Tests D-1 and D-2.

[0152] The steps leading to the coated substrate designated Test D-2 were repeated identically, with the sole exception that the substrate was replaced by recycled PET dyed black to obtain a substrate coated with a composite coating: - of a 1 ère layer called coloured tack coat; - of a 2 ème layer called clear varnish topcoat, and hereafter referred to as Test D-3.

[0153] Table 9 below details, for each of these coated substrates, namely Tests D-1 to D-3: - the composition that resulted in the 1 ère layer with a thickness of 3 pm; - the composition that resulted in the 2 ème layer with a thickness of 14 pm; - the substrate material. Table 9

[0154] Furthermore, 5 compositions D7 to D11 comprising the following components: - a ready-to-use varnish formulation for coating plastic material substrates with a varnish finish layer, - a 1 ère solution or a 2 ème black colour solution comprising black dyes and designed to colour a ready-to-use varnish formulation, were prepared, according to the mass percentages expressed relative to the total mass of the composition which are detailed in Table 10 below.

[0155] The ready-to-use varnish formulation for coating plastic material substrates with a varnish topcoat was a formulation classically used to obtain a topcoat of varnish for a plastic material substrate.

[0156] The 1 ère and 2 ème Black color solutions were designed to color a ready-to-use varnish formulation. The dry extract of the black dyes ranged from 0.1% to 10% in these 1st e f 2nd solutions. The 2 ème the black colour solution was twice as concentrated in black dyes as the 1 ère black color solution. Table 10

[0157] 5 substrates coated with a coating as detailed in Table 11 below and hereafter designated Tests D-4 to D-8 were obtained in the same manner as the substrates of Tests D-1 to D-3.

[0158] Table 11 below details the following for each of the coated substrates: - the composition that resulted in the 1 ère layer with a thickness of 3 pm; - the composition that resulted in the 2 ème layer with a thickness of 14 pm; - the substrate material. Table 1 1

[0159] Table 12 below summarizes, for Tests D-1 to D-8, the blackness value (My) and whether the substrate identification by near-infrared spectroscopy could be carried out ("OK") or not ("not OK"). Table 12

[0160] Based on the detailed results in Table 12 above, we note that: - By comparing the blackness values ​​of tests D-2 and D-3, using the recycled and black-dyed PET substrate, we obtain a coated substrate with a higher blackness level and in deep black than with a HDPE substrate and dyed black; - by comparing, in particular, the blackness values ​​of tests D-6 and D-7, the 2 èmes black colour solutions comprising black dyes and designed to colour the primer and topcoat formulations of varnishes that were twice as concentrated in dyes as the 1 èresBlack colour solutions including black dyes and designed to colour the tack coat and topcoat formulations of varnishes have made it possible to obtain coated substrates of the highest blackness, and in particular in deep black for recycled and black-tinted PET substrates, while allowing the identification of the plastic material of the substrate by near-infrared spectroscopy.

[0161] E- Coatings composed of a primer coat containing a colorant, a colored undercoat containing a colorant, and a topcoat of colorless varnish.

[0162] 5 compositions (namely compositions E1 to E5) comprising the following components: - a ready-to-use coloured undercoat formulation for coating plastic material substrates with a coloured undercoat; - a 1 ère solution or a 2 èmeblack colour solution comprising dyes and designed to colour a coloured undercoat formulation, were prepared, according to the mass percentages expressed relative to the total mass of the composition which are detailed in Table 13 below.

[0163] The formulation of the ready-to-use colored undercoat for coating plastic material substrates with a colored undercoat was a formulation classically used for obtaining a colored undercoat for a plastic material substrate.

[0164] The 1 ère and 2 ème Black color solutions were designed to color a ready-to-use colored undercoat formulation. They were pigment-free. They contained black dyes, namely substances soluble in the ready-to-use colored undercoat formulation. The dry extract of these black dyes ranged from 0.1% to 10% in these solutions. èreand 2 ème solutions. The 2 ème the black colour solution was twice as concentrated in black dyes as the 1 ère black color solution. Table 13

[0165] Five coated substrates, hereinafter referred to as Tests E-1 to E-5, were obtained in the following manner:

[0166] A composition chosen from compositions D3, D5 and D6 described in point D above and as specified in Table 12 below in the column entitled "1 ère layer" was applied by spraying onto the surface of a substrate as defined in the last column of Table 12 so as to form a 1 ère a layer with a thickness of 3 µm on said substrate. Then, the layer thus obtained was dried in a hot air oven.

[0167] Following this drying process, a composition chosen from the compositions detailed in Table 12 below in the column entitled "2 ème "Layer" was applied by spraying to the surface of the 1 ères layers thus obtained to form 2 èmes layers of a thickness of 10 µm on said 1 ères Then, the 2 layers. èmes The resulting layers were dried in a hot air oven. Following this drying process, the two èmes The layers were cross-linked by exposure to ultraviolet rays.

[0168] Next, the same colorless varnish composition used in the experiments at point B above was sprayed onto the surface of the 2 èmes layers to form 3 èmes layers with a thickness of 10 µm on said 2 èmes Then, the 3 layers. èmesThe resulting layers were dried in a hot air oven. Following this drying process, the 3 èmes The layers were cross-linked by exposure to ultraviolet rays to obtain substrates coated with a composite coating: - of a 1 ère layer called tack coat; - of a 2 ème layer called coloured underlayer; - of a 3 ème layer called colorless varnish topcoat, and hereinafter respectively designated Tests E-1 to E-5.

[0169] Table 14 below details, for each of the coated substrates: - the composition that resulted in the 1 ère layer with a thickness of 3 pm; - the composition that resulted in the 2 ème layer with a thickness of 10 pm; - the total thickness of the coating - the substrate material.

[0170] In these E-1 to E-5 tests, the black-tinted HDPE and black-tinted recycled PET substrates were identical (i.e., same geometric shape and same dimensions) to the substrates in the tests at point D above. Table 14

[0171] Table 15 below summarizes, for Tests E-1 to E-5, the blackness value (My) and whether the substrate identification by near-infrared spectroscopy could be carried out ("OK") or not ("not OK"). Table 15

[0172] Based on the detailed results in Table 15 above, we note that: - the colored underlayer contributes to the blackness of the substrate coated with a coating; - the highest blackness value was obtained when the 2 èmeblack colour solutions designed to colour the ready-to-use coloured undercoat formulation and the ready-to-use tack coat formulation were used, namely black colour solutions which contained colourants in a concentrated form; - By comparing the blackness values ​​of tests D-1 to D-8 with those of tests E-1 to E-5, the clear varnish topcoat did not alter the blackness of the coated substrates, nor did it compromise the identification of the plastic material by near-infrared spectroscopy. Thanks to the clear varnish topcoat, the coated substrates from tests E-1 to E-5 are more scratch-resistant than the coated substrates from tests D-1 to D-8.

Claims

DEMANDS 1. Substrate (2) made of at least one plastic material that is identifiable by near-infrared spectroscopy, at least a portion of said substrate (2) having a thickness of at least 0.6 mm and being coated wholly or partly with a coating (3a, 3b, 3c, 3d), characterized in that: the assembly (1a, 1b, 1c, 1d) consisting of at least a portion of said substrate (2) and the coating (3a, 3b, 3c, 3d) has a specific color in the black or deep black range and in that the coating (3a, 3b, 3c, 3d) comprises: - optionally at least one tack coat (5); - at least one topcoat (4) which is disposed on the substrate (2) or, where the coating (3c) includes at least one primer (5), said at least one topcoat (4) is disposed on said at least one primer (5), at least one of the layers (4,5) of the coating (3a, 3b, 3c, 3d) includes at least one colouring agent selected from the group consisting of pigments and dyes, taken alone or in mixtures thereof, if the coating (3a, 3b, 3c, 3d) includes pigments, the mass content of said pigments, expressed in relation to the total mass of the coating (3a, 3b, 3c, 3d): - does not exceed 10.00%, preferably not exceeding 6.50%, when it comes to pigments selected from black metallic oxides and perylene black, - does not exceed 1.14%, preferably does not exceed 1.00%, when it comes to pigments chosen from carbon black, graphite and aniline black, the thickness of said coating (3a, 3b, 3c, 3d) is between 3 pm and 30 pm.

2. Substrate (2) coated with a coating (3a, 3b, 3c, 3d) according to claim 1, characterized in that at least one plastic material is selected from polyethylene (hereinafter abbreviated as "PE"), polyethylene terephthalate, high-density PE, low-density PE, polypropylene, polystyrene, polyamide, acrylonitrile butadiene styrene, ethylene vinyl acetate, styrene acrylonitrile, poly methyl methacrylate acrylic, styrene methyl methacrylate, polyethylene terephthalate glycol, polylactic acid, polyhydroxyalkanoate and poly hydroxybutyrate, taken alone or in mixtures thereof.

3. Substrate (2) coated with a coating (3c, 3d) according to claim 1 or 2, characterized in that the coating (3c) further comprises at least one colored undercoat (6) which is disposed between the substrate (2) and at least one topcoat (4) or, where the coating (3d) comprises at least one tack coat (5), said at least one colored undercoat (6) is disposed between at least one tack coat (5) and at least one topcoat (4).

4. Substrate (2) coated with a coating (3a, 3b, 3c, 3d) according to any one of claims 1 to 3, characterized in that the coating (3a, 3b, 3c, 3d) comprises only dyes as a coloring agent and the thickness of said coating (3a, 3b, 3c, 3d) is between 10 pm and 28 pm.

5. Substrate (2) coated with a coating (3a, 3b, 3c, 3d) according to any one of claims 1 to 3, characterized in that the coating (3a, 3b, 3c, 3d) comprises as a colouring agent only pigments selected from black coloured metal oxides, perylene black, carbon black, graphite and aniline black and the thickness of said coating (3a, 3b, 3c, 3d) is between 5 pm and 25 pm.

6. Substrate (2) coated with a coating (3a, 3b, 3c, 3d) according to any one of claims 1 to 5, characterized in that the topcoat (4) is a colorless varnish layer and the thickness of said topcoat is less than 20 pm.

7. Substrate (2) coated with a coating (3a) according to claim 1 or 2, characterized in that the coating (3a) comprises at least one colored topcoat (4) which is disposed on the substrate (2).

8. Substrate (2) coated with a coating (3b) according to claim 1 or 2, characterized in that the coating (3b) comprises: - at least one coloured or colourless bonding layer (5) which is disposed on the substrate (2); - at least one coloured or colourless topcoat (4) which is disposed on said coloured or colourless tackcoat (5).

9. Substrate (2) coated with a coating (3c) according to claim 1 or 2, characterized in that the coating (3c) comprises: - at least one coloured or colourless bonding layer (5) which is disposed on the substrate (2); - at least one coloured undercoat (6) which is disposed on said at least one colourless or coloured bonding coat (5); - at least one coloured or colourless topcoat (4) which is disposed on said at least one coloured undercoat (6).

10. Substrate (2) coated with a coating (3d) according to claim 1 or 2, characterized in that the coating (3d) comprises: - at least one coloured underlayer (6) which is disposed on the substrate (2); - at least one coloured or colourless topcoat which is disposed on said at least one coloured undercoat (6).

11. Substrate (2) coated with a coating (3a, 3b, 3c, 3d) according to any one of claims 1 to 10, characterized in that the entire substrate (2) has a thickness of at least 0.6 mm and the coating (3a, 3b, 3c, 3d) is present on the entire substrate (2).

12. Substrate (2) coated with a coating (3a, 3b, 3c, 3d) according to any one of claims 1 to 11, characterized in that at least a part of the substrate (2) which is coated with a coating (3a, 3b, 3c, 3d) has a Young's modulus between 0.4 GPa and 5 GPa.

13. Substrate (2) coated with a coating (3a, 3b, 3c, 3d) according to any one of claims 1 to 12, characterized in that the substrate (2) is a plastic material packaging which has been obtained by injection or injection blow molding.

14. Substrate coated with a coating according to any one of claims 1 to 13, characterized in that the substrate (2) is a packaging for a cosmetic product.

15. A method for manufacturing a substrate (2) made of plastic material coated with a coating (3a, 3b, 3c, 3d) according to any one of claims 1 to 14, characterized in that it comprises at least the following steps: 1) We have a substrate (2) made of plastic material identifiable by near-infrared spectroscopy, 2) Optionally, at least one tack coat formulation (5) is applied to the substrate (2) so as to obtain at least one tack coat (5) or at least one coloured undercoat formulation (6) is applied so as to obtain at least one coloured undercoat (6) or at least one tack coat formulation (5) is applied to the substrate (2) so as to obtain at least one tack coat (5), then at least one coloured undercoat formulation (6) is applied to said at least one tack coat (5) so as to obtain at least one coloured undercoat (6), 3) at least one topcoat formulation (4) is applied to the substrate (2), where appropriate when the coating (3b) includes at least one tack coat (5) and is devoid of a coloured undercoat (6), at least one topcoat formulation (4) is applied to said at least one tack coat (5), where appropriate when the coating (3c, 3d) includes at least one coloured undercoat (6), at least one topcoat formulation (4) is applied to said at least one coloured undercoat (6), the application of at least one topcoat being followed by an ultraviolet curing step so as to obtain the substrate (2) coated with a coating (3a, 3b, 3c, 3d).

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