Durable decoratively coated substrates and process for obtaining the same

Technical Field

[0001]The present invention relates to a decorative coating system deposited onto a substrate. This coating system comprises at least two coating sub-systems, a PVD coating sub-system obtained by physical vapor deposition (PVD), which is deposited above a basecoat sub-system, based on carbon, in contact with the substrate, and optionally a topcoat sub-system, based on silicon, deposited above the PVD coating sub-system.

[0002]According to the invention, the PVD coating sub-system comprises one or more layers and may be an alternating layer system. In particular the PVD coating sub-system may comprise at least one layer giving a decorative, in particular a metallic, aspect. In particular the PVD coating sub-system may comprise at least two layers having a different composition.

[0003] The coating system according to the present invention is particularly suited for non-metallic substrates and can be used as a solution for various problems. Such a layer system is particularly interesting in relation to decorative coatings having improved durability.

Background Art

[0004] It is known to apply decorative coatings to a variety of substrates by physical vapor deposition. Many substrates, in particular polymer substrates require the use of a primer to ensure sufficient adhesion of the PVD decorative coating. Some primers are based on a wet coating technology, using essentially a kind of paint or lacquer. These primers however require lengthy curing times. Furthermore the substrates need to be transferred to a separate coating line for the physical vapor deposition of the decorative coating system, which is performed under vacuum.

[0005] Surface activation by UV radiation is not compatible with all polymer substrates and may lead in polymers such as for example poly-methyl methacrylate (PMMA) to significant degradation. Similar surface degradation may be observed when certain polymer substrates are exposed to certain plasma sources that generate UV light, even to the plasma a magnetron sputtering source.

[0006] Many plasma activation processes are inefficient or must be run at low intensities to avoid overheating the substrates and therefore slow down the overall coating process.

[0007] Even though plasma activation processes improve the adhesion of a subsequent PVD deposited coating, it was found that the mechanical durability of these coatings is still insufficient.

Summary of invention

[0008] It is an objective of the present invention to provide a fast and efficient process for coating substrates with decorative coating systems that provide mechanically durable PVD based decorative coatings, in particular on non- metallic substrates.

[0009] The substrates with decorative coating systems obtained by the process of the present invention may be used as decorative elements in a wide variety of applications, on appliances, electronic devices, furniture, or building elements for example. Their enhanced durability makes them particularly well suited for use on vehicles, for example on cars. This latter application is particularly interesting when the substrate is polymer-based and to be used as a replacement of metallic parts that fulfil at least a decorative function.

[0010] It is another objective of the present invention to obtain substrates provided with a decorative coating system that is mechanically durable, having good adhesion properties and being in particular resistant to abrasion.

[0011] In the processes of the present invention linear hollow cathode plasma sources are used. Such a plasma sources are for example described in WO2010017185A1 .

[0012]The present invention relates, in an embodiment, to a process for depositing decorative coating systems on substrates comprising: a. providing a substrate in a vacuum chamber; b. exposing at least part of the surface of the substrate to an activation plasma generated by a first plasma source, of linear hollow-cathode type; c. depositing a basecoat sub-system comprising a layer which is based on carbon on the activated surface of the substrate, using a second plasma source, of linear hollow- cathode type; d. depositing by physical vapor deposition a PVD coating sub-system on the basecoat.

[0013] The layer based on carbon comprises at least 50 atomic % of carbon and up to 50 atomic % of hydrogen. It comprises sp2 and sp3 hybridizations in the carbon-carbon bonds. Such amorphous carbon based layers are also known as hydrogenated amorphous carbon layers and frequently abbreviated a-C:H according to for example the guidelines VDI 2840 (2012) of the Association of German Engineers (Verein Deutscher Ingenieure, VDI).

[0014] In the present invention, all surface treatment and coating steps may be performed in the same vacuum chamber, thus avoiding having to transfer substrates from one surface treatment or coating apparatus to another apparatus. Furthermore, the use of hollow cathode plasma sources allows for highly efficient surface treatments and coatings without overheating the substrates.

[0015] The inventors have found that, by the use of the process of the present invention, it is possible to obtain in an efficient manner decorative coating systems that are highly durable, in particular from a mechanical point of view, on a variety of substrates. It was found in particular that the use hollow cathode plasma sources results in high deposition rates or short deposition durations but without degradation of the substrates, even when these are textile and/or polymer based substrates.

[0016] “Plasma source of hollow cathode type,” is taken to mean a plasma or ion source comprising one or more electrodes configured to produce hollow cathode discharges. One example of a hollow cathode plasma source is described in US8652586B2 to Maschwitz, incorporated herein by reference in its entirety. The AC power source supplies a varying or alternating bipolar voltage to the two electrodes. The AC power supply initially drives the first electrode to a negative voltage, allowing plasma formation, while the second electrode is driven to a positive voltage in order to serve as an anode for the voltage application circuit. This then drives the first electrode to a positive voltage and reverses the roles of cathode and anode. As one of the electrodes is driven negative, a discharge forms within the corresponding cavity. The other electrode then forms an anode, causing electrons to escape the plasma through the outlet and travel to the anodic side, thereby completing an electric circuit. A plasma having a curtain shape is thus formed in the region between the first and the second electrodes above the substrate . Substrate is presently illustrated as a single sheet of fabric, it may however also be in the shape of a long ribbon, for instance in a roll-to-roll type coating device, or in a more or less complex three dimensional shape. This method of driving hollow cathodes with AC power contributes formation of a uniform linear plasma that spans across the substrate, perpendicular to the travelling direction of the substrate. For the purpose of the present patent, the electron emitting surfaces may also be called plasma generating surfaces.

[0017] “Closed circuit electron drift” is taken to mean an electron current caused by crossed electric and magnetic fields. In many conventional plasma forming devices the closed circuit electron drift forms a closed circulating path or “racetrack” of electron flow.

[0018] “AC power” is taken to mean electric power from an alternating source wherein the voltage is changing at some frequency in a manner that is sinusoidal, square wave, pulsed or some other waveform. Voltage variations are often from negative to positive, i.e. with respect to ground. When in bipolar form, power output delivered by two leads is generally about 180° out of phase.

[0019] “Electrodes” provide free electrons during the generation of a plasma, for example, while they are connected to a power supply providing a voltage. The electron-emitting surfaces of a hollow cathode are considered, in combination, to be one electrode. Electrodes can be made from materials well-known to those of skill in the art, such as steel, stainless steel, copper, or aluminum. However, these materials must be carefully selected for each plasma-enhanced process, as different gasses may require different electrode materials to ignite and maintain a plasma during operation. It is also possible to improve the performance and/or durability of the electrodes by providing them with a coating.

[0020] According to the present invention at least part of the surface of the substrate is exposed to a plasma generated by a first hollow cathode plasma source in order to activate the surface of the substrate. This activation step, in combination with the following basecoat sub-system deposition step, was found to be essential for obtaining mechanically durable products.

Description of embodiments

[0021] Exposing at least part of the surface of a provided substrate to an activation plasma generated by a first plasma source, of linear hollow-cathode type, may comprise: a. providing a first plasma source, of linear hollow-cathode type, comprising at least one pair of hollow-cathode plasma generating electrodes connected to an AC, DC or pulsed DC generator, for the activation of the substrate; b. injecting a first plasma generating gas in the first plasma source’s electrodes at a flow rate of between 1000 seem and 5000 seem per linear meter of plasma of the first plasma source; c. applying a first electrical power to the first plasma source, so that the first power density of the plasma is between 2 kW and 20 kW per linear meter of plasma of the first plasma source; d. activating at least part of the substrate’s surface by exposing the substrate to the plasma of the first plasma source.

[0022] In certain embodiments of the present invention, the first plasma source is connected to a generator providing an AC or pulsed DC current at a frequency comprised between 5 kHz and 150kHz, alternately between 5 kHz and 100kHz.

[0023] In certain embodiments of the present invention, the first plasma source provides a plasma having a power density comprised between 4 kW and 15 kW per linear meter of plasma source, preferably comprised between 5 kW and 10 kW per linear meter of plasma source.

[0024] In certain embodiments of the present invention, the first plasma generating gas is injected in the first plasma source’s electrodes at a flow rate of between 1500 seem and 4500 seem per linear meter of plasma of the first plasma source, preferably between 2000 seem and 4000 seem per linear meter of plasma of the first plasma source. [0025] In certain embodiments, the first plasma generating gas is selected among O2, N2, He, Ar or among a mixture of two or more of these gases.

[0026] In certain embodiments of the present invention, the distance between the substrate surface and the outlets of the first plasma source is comprised between 50 mm and 150 mm, advantageously between 60 mm and 120 mm, more advantageously between 80 mm and 100 mm.

[0027] According to certain embodiments, the substrate may be exposed to the first plasma for a duration of up to 12s, advantageously up to 10s, more advantageously up to 8s. Furthermore the substrate may be exposed to the first plasma for at least 4s, advantageously at least 5s, more advantageously at least 6s.

[0028] The activation of the present invention is advantageously performed at a pressure comprised between 0.005 Torr and 0.050 Torr, more advantageously comprised between 0.010 Torr and 0.040 Torr, even more advantageously between 0.020 Torr and 0.030 Torr.

[0029] Depositing a basecoat sub-system comprising a layer which is based on carbon on the activated surface of the substrate, using a second plasma source, of linear hollow- cathode type may comprise: a. providing a second plasma source, of linear hollow-cathode type, comprising at least one pair of hollow-cathode plasma generating electrodes connected to an AC, DC or pulsed DC generator, for the deposition of said basecoat on the activated surface of the substrate; b. injecting a second plasma generating gas in the second plasma source’s electrodes at a flow rate of between 1000 seem and 5000 seem per linear meter of plasma of the second plasma source; c. applying a second electrical power to the second plasma source, so that the second power density of the plasma is between 2 kW and 20 kW per linear meter of plasma of the second plasma source; d. injecting a gaseous precursor of carbon at a flow rate of between 50 seem and 600 seem per linear meter of plasma of the second plasma source, the gaseous precursor being preferably injected into the plasma at least between the electrodes of each electrode pair of the second plasma source; e. exposing the substrate to the plasma of the second plasma source, thereby depositing a basecoat comprising a layer which is based on carbon on the activated surface of the substrate.

[0030] The inventors have found that, the combination of the surface activation and basecoat deposition allows for particularly good adhesion of the following magnetron sputtered coating. This adhesion leads to particularly good scratch resistance of the final coating.

[0031] In certain embodiments, the second plasma source is connected to a generator providing an AC or pulsed DC current at a frequency comprised between 5 kHz and 150 kHz, alternately between 5 kHz and 100 kHz.

[0032] In certain embodiments of the present invention, the second plasma source provides a plasma having a power density comprised between 4 kW and 15 kW per linear meter of plasma source, preferably comprised between 5 kW and 10 kW per linear meter of plasma source.

[0033] In certain embodiments, the gaseous precursor of carbon is injected, preferably in between the second plasma source’s electrodes, at a flow rate of between 100 seem and 500 seem per linear meter of plasma of the second plasma source, preferably between 200 seem and 400 seem per linear meter of plasma of the second plasma source.

[0034] In certain embodiments, the second plasma generating gas is injected in the second plasma source’s electrodes at a flow rate of between 1500 seem and 4500 seem per linear meter of plasma of the second plasma source, preferably between 2000 seem and 4000 seem per linear meter of plasma of the second plasma source.

[0035] In certain embodiments, the second plasma generating gas is selected among N2, He, Ar or among a mixture of two or more of these gases. [0036] In certain embodiments of the present invention the distance between the substrate surface and the outlets of the second plasma source is comprised between 50 mm and 150 mm, advantageously between 60 mm and 120 mm, more advantageously between 80 mm and 100 mm.

[0037] In certain embodiments of the present invention, basecoat subsystem deposition is advantageously performed at a pressure comprised between 0.005 Torr and 0.050 Torr, more advantageously comprised between 0.010 Torr and 0.040 Torr, even more advantageously between 0.020 Torr and 0.030 Torr.

[0038] In certain embodiments of the present invention, the carbon precursor gas may be a hydrocarbon gas, that is a gaseous organic compound consisting entirely of hydrogen and carbon, for example selected among CPU, C2H4, C2H2, C3H8, C4H10. In certain advantageous embodiments the carbon precursor gas is

CH .

[0039] In certain embodiments of the present invention, the thickness of the basecoat subsystem is comprised between 2 nm and 200nm. Advantageously the thickness of the of the basecoat subsystem may be comprised between 2 nm and 200nm, more advantageously between 2 nm and 100nm.

[0040] In certain embodiments of the present invention, the hybridization ratio sp3/sp2 of the basecoat subsystem’s carbon based layer is comprised between 0.6 and 0.8. This corresponds to a sp3/(sp3+sp2) ratio of between 37.5% and 44.4%

[0041] In embodiments of the present invention the deposition of the decorative PVD coating sub-system on the basecoat is performed using conventional magnetron sputtering processes, well known in the art. Representative descriptions of sputter-depositing processes and equipment may be found in for example US4204942A, US4948087A, US5589280A, US20110275262A1 ,

KR20120026936A, and EP0546470A1 which are incorporated by reference. In other embodiments of the present invention the deposition of the decorative PVD coating sub-system on the basecoat is performed using evaporation, such as thermal evaporation or e-beam evaporation. The material deposited by any physical vapor deposition technique may advantageously be selected among Ag, Cu, Al, Cr, Ti, or silicon, or metal alloys as NiCr-alloys or NiCrW alloys. [0042] In certain embodiments of the present invention, the targets used for magnetron sputtering may be circular target or linear targets, linear targets being particularly useful in continuous coating processes. The targets used may be metallic targets, comprising for example metals chosen among Ag, Cu, Al, Cr, Ti, or silicon based targets, or metal alloy targets comprising for example NiCr- alloys or NiCrW alloys.

[0043] In certain embodiments evaporation is performed using ingots of the same materials as the targets mentioned hereinabove for magnetron sputtering.

[0044] In certain embodiments of the present invention, the PVD coating sub-system comprises a first layer comprising or essentially consisting of Ag, Cu, Al, Cr, NiCr-alloy, Ti, titanium nitride, silicon, or NiCrW alloy. Nitrides may require the addition of N2 to the process when sputtering from a metal or silicon target.

[0045] In certain embodiments of the present invention, the thickness of the decorative PVD coating subsystem is comprised between 20 nm and 300nm. Advantageously the thickness of the decorative PVD subsystem coating may be comprised between 30 nm and 150nm, more advantageously between 40 nm and 120nm.

[0046] In certain embodiments of the present invention, the physical vapor deposition step may be performed applying a power comprised between 1 kW and 20 kW per linear meter of target.

[0047] In certain embodiments of the present invention the plasma generating gas used for physical vapor deposition is advantageously Argon. The plasma generating gas may be supplied at a flow rate comprised between 50 seem and 500 seem.

[0048] In certain embodiments of the present invention, physical vapor deposition is advantageously performed at a pressure comprised between 0.002 Torr and 0.050 Torr, more advantageously comprised between 0.003 Torr and 0.020 Torr, even more advantageously between 0.004 Torr and 0.010 Torr.

[0049] In certain embodiments of the present invention the PVD coating sub-system comprises one or more additional layers, above or below the first layer. These additional layers may comprise or essentially consist of an oxide or a nitride of a metal, of a metal alloy or of silicon. Oxide layers may advantageously be deposited from a ceramic target, in particular when deposited above the first layer. Metals and metal alloys may be chosen among Al, Cr, NiCr-alloy, Ti, or NiCrW alloy. These additional layers may protect the first layer from oxidation and/or increase gas and/or vapor barrier properties of the coated substrate.

[0050] The terms before, after, above, below, on and under, indicate the sequence of the layers starting from the substrate.

[0051] The PVD coating subsystem provides mainly the decorative aspect of the resulting coated substrate. In particular the resulting decorative coating may provide a metallic aspect to a substrate which is non-metallic. This metallic aspect may be achieved by the deposition of metallic layers in the PVD coating subsystem, but also by certain other layer materials such as titanium nitride for example which can be used to provide a metallic aspect with a golden tint.

[0052] In certain optional embodiments of the present invention, the process further comprises, after depositing the PVD coating subsystem, depositing a topcoat sub-system comprising a layer which is based on silicon oxide on the PVD coating sub-system, using a third plasma source, of linear hollow- cathode type.

[0053] Depositing a topcoat sub-system comprising a layer which is based on silicon oxide on the PVD coating sub-system, using a third plasma source, of linear hollow- cathode type, may comprise: a. providing third plasma source, of linear hollow- cathode type, which is a low-pressure PECVD device comprising at least one linear hollow-cathode plasma source, each source comprising at least one pair of electrodes connected to an AC, DC or pulsed DC generator, for the deposition of said layer based on silicon oxide on the PVD coating sub-system, b. applying an electrical power to the plasma source, so that the power density of the plasma is between 1 kW and 50 kW per linear meter of plasma source, and, c. applying, to the substrate, a gaseous precursor of oxides of silicon at a flow rate of between 50 seem and 700 seem per linear meter of the plasma source, the gaseous precursor being preferably injected in between the electrodes of each electrode and a third plasma generating gas, based on oxygen or on oxygen comprising derivatives at a flow rate of between 1500 seem and 5000 seem per linear meter of the plasma source, this reactive third plasma generating gas being injected in the electrodes of the third plasma source, of linear hollow- cathode type.

[0054] In certain embodiments of the present invention the third plasma source is connected to a generator providing an AC current at a frequency comprised between 5 kHz and 150 kHz, alternately between 5 kHz and 100 kHz.

[0055] In certain embodiments of the present invention the third plasma source provides a plasma having a power density comprised between 2 kW and 30 kW per linear meter of plasma source, preferably comprised between 3 kW and 15 kW per linear meter of plasma source.

[0056] In certain embodiments, the gaseous precursor of silicon is injected, preferably in between the third plasma source’s electrodes, at a flow rate of between 150 seem and 500 seem per linear meter of plasma of the third plasma source, preferably between 200 seem and 500 seem per linear meter of plasma of the third plasma source.

[0057] In certain embodiments, the third plasma generating gas is injected in the third plasma source’s electrodes at a flow rate of between 1500 seem and 4500 seem per linear meter of plasma of the third plasma source, preferably between 2000 seem and 4000 seem per linear meter of plasma of the third plasma source.

[0058] In certain embodiments the third plasma generating gas is selected among O2, N2, He, Ar or among a mixture of two or more of these gases.

[0059] In certain embodiments of the present invention the distance between the substrate surface and the outlets of the third plasma source is comprised between 50 mm and 150 mm, advantageously between 60 mm and 120 mm, more advantageously between 80 mm and 100 mm.

[0060] In certain embodiments of the present invention, topcoat subsystem deposition is advantageously performed at a pressure comprised between 0.005 Torr and 0.025 Torr, more advantageously comprised between 0.010 Torr and 0.020 Torr, even more advantageously between 0.013 Torr and 0.015 Torr. [0061]The silicon oxide precursors that may be used in any embodiment of the present invention depend on the nature of the layer which will be deposited. These are gaseous or volatile products, in particular at the temperatures and pressures at which the process is carried out. The precursors of silicon oxide are typically SihU (silane), TMDSO (tetramethyldisiloxane) and HMDSO (hexamethyldisiloxane) this list not being exhaustive.

[0062] In certain embodiments of the present invention, the thickness of the topcoat subsystem is comprised between 20 nm and 200 nm. Advantageously the thickness of the of the topcoat subsystem may be comprised between 30 nm and 150 nm, more advantageously between 40 nm and 120 nm.

[0063] The presence of the optional top-coat subsystem further improves the mechanical durability of the coating on the substrate.

[0064] High dynamic deposition rates may be obtained by the processes for the deposition of the basecoat and the optional topcoat of the present invention. In particular, by the use of the process, it is possible to obtain, at high dynamic deposition rates, carbon based and silicon oxide based layers which strongly adhere to the substrate and PVD coating subsystem respectively as can be seen in the greatly improved abrasion test results.

[0065] The present invention is applicable to a great variety of substrates. In certain embodiments of the present invention the substrate may be selected among substrates based on polymers, on ceramics, on metals or on glass. The substrate may be flexible or rigid.

[0066] In certain embodiments of the present invention the substrate is a glass substrate, for example chosen among soda-lime glass, aluminosilicate glass or borosilicate glass.

[0067] In certain embodiments of the present invention the substrate may be a metal substrate. The metal substrate may comprise any one or a combination of the following: aluminium; aluminium alloy; magnesium; magnesium alloy; steel; aluminium; stainless steel; zinc or zinc alloy or titanium or titanium alloy. In particular embodiments of the present invention the metal substrate comprises a lightweight metal or metal alloy and particularly those typically used for the aerospace and aviation industries. [0068] In particular embodiments of the present invention, the metal substrate is based on magnesium, aluminium, zinc or titanium, or is based on alloys of magnesium, aluminium, zinc or titanium. In certain particular embodiments, the metal substrate may be anodized by any anodizing process known in the art.

[0069] In certain embodiments of the present invention the substrate may be a polymer substrate. The polymer substrates of the present invention may be homogeneous sheets of polymer, but other shapes are also possible.

[0070] In certain embodiments of the present invention, a polymer substrate of may comprise acrylic polymers, polymethylmethacrylate (PMMA) and its copolymers, CR-39 or allyl diglycol carbonate (ADC), polycarbonate, poly propylene (PP), biaxially oriented polypropylene (BOPP), Polyethylene (PE), Polyvinylchloride (PVC) polyethylene terephthalate (PET), polystyrene, cyclic olefin co-polymers (COC's) and polyethylene terephthalate glycol (PETG), and combinations of the foregoing. Polymer substrates of the present invention may comprise thermoplastic elastomers (TPE), sometimes referred to as thermoplastic rubbers, which are a class of copolymers or a physical mix of polymers, usually a plastic and a rubber, that consist of materials with both thermoplastic and elastomeric properties. In particular the polymer substrates may comprise Styrenic block copolymers, TPS (TPE-s), Thermoplastic polyolefinelastomers, TPO (TPE-o), Thermoplastic Vulcanizates, TPV (TPE-v or TPV), Thermoplastic polyurethanes, TPU (TPU), Thermoplastic copolyester, TPC (TPE-E), Thermoplastic polyamides, TPA (TPE-A).

[0071] In certain embodiments of the present invention a polymer substrate may be a thin polymer film, having a thickness comprised between 5 pm and 300 pm, alternately between 10 pm and 250 pm, alternately between 20 pm and 200 pm, alternately between 25 pm and 150 pm. These polymer thin films may be processed in a roll-to-roll manner.

[0072] In certain embodiments of the present invention the substrate may be a fabric substrate. The fabric substrate may be selected among textiles based on one or more of the following fibrous materials or fibers: synthetic fibers, for example Polyester, Polyethylene, Polypropylene, or Aramid, natural fibers, for example wool, cotton, silk, or linen. The textile substrate may be a woven or a non-woven textile. [0073] In certain embodiments of the present invention, the fabric substrate can include any textile, fabric material, fabric clothing, felt, or other fabric structure. The term "fabric" can be used to mean a textile, a cloth, a fabric material, fabric clothing, or another fabric product. The term "fabric structure" is intended to mean a structure having warp and weft that is woven, non-woven, knitted, tufted, crocheted, knotted, and/or pressured, for example. The terms "warp" and "weft" refer to weaving terms that have their ordinary means in the textile arts, as used herein, e.g., warp refers to lengthwise or longitudinal yarns on a loom, while weft refers to crosswise or transverse yarns on a loom.

[0074]Additionally, fabric substrates useful in the present invention can include fabric substrates that have fibers that can be natural and/or synthetic. It is notable that the term "fabric substrate" does not include materials commonly known as any kind of paper (even though paper can include multiple types of natural and synthetic fibers or mixture of both types of fibers). Furthermore, fabric substrates include both textiles in its filament form, in the form of fabric material, or even in the form of fabric that has been crafted into finished article (clothing, blankets, tablecloths, napkins, bedding material, curtains, carpet, shoes, etc.). In some examples, the fabric substrate has a woven, knitted, non-woven, or tufted fabric structure.

[0075] In an embodiment of the present invention the fabric substrate can be a woven fabric where warp yarns and weft yarns are mutually positioned at an angle of about 90°. This woven fabric can include, but is not limited to, fabric with a plain weave structure, fabric with a twill weave structure where the twill weave produces diagonal lines on a face of the fabric, or a satin weave. The fabric substrate can be a knitted fabric with a loop structure including one or both of warp-knit fabric and weft-knit fabric. The weft- knit fabric refers to loops of one row of fabric are formed from the same yarn. The warp-knit fabric refers to every loop in the fabric structure that is formed from a separate yarn mainly introduced in a longitudinal fabric direction. The fabric substrate can also be a non-woven product, for example a flexible fabric that includes a plurality of fibers or filaments that are bonded together and/or interlocked together by a chemical treatment process (e.g. a solvent treatment), a mechanical treatment process (e.g. embossing), a thermal treatment process, or a combination of two or more of these processes.

[0076] In an embodiment of the present invention the fabric substrate can include one or both of natural fibers and synthetic fibers. Natural fibers that can be used include, but are not limited to, wool, cotton, silk, linen, jute, flax or hemp. Additional fibers that can be used include, but are not limited to, rayon fibers, or those of thermoplastic aliphatic polymeric fibers derived from renewable resources, including, but not limited to, corn starch, tapioca products, or sugarcanes. These additional fibers can be referred to as "natural" fibers. In some examples, the fibers used in the fabric substrate includes a combination of two or more from the above-listed natural fibers, a combination of any of the above-listed natural fibers with another natural fiber or with synthetic fiber, a mixture of two or more from the above-listed natural fibers, or a mixture of any thereof with another natural fiber or with synthetic fiber.

[0077] In an embodiment of the present invention the synthetic fibers that can be used in the fabric substrate can include glass fibers or polymeric fibers such as, but not limited to, polyvinyl chloride (PVC) fibers, polyvinyl chloride (PVC)-free fibers made of polyester, polyamide, polyimide, polyacrylic, polyacrylonitrile, polypropylene, polyethylene, polyurethane, polystyrene, polyaramid, e.g. para- aramid known as Kevlar® for example, (trademark of E. I. du Pont de Nemours and Company), fiberglass, poly(trimethylene terephthalate), polycarbonate, polyester terephthalate, polyethylene or polybutylene terephthalate. In some examples, the fiber used in the fabric substrate can include a combination of two or more fiber materials, a combination of a synthetic fiber with another synthetic fiber or natural fiber, a mixture of two or more synthetic fibers, or a mixture of synthetic fibers with another synthetic or natural fiber. In some examples, the fabric substrate is a synthetic polyester fiber or a fabric made from synthetic polyester fibres.

[0078] In an embodiment of the present invention the fabric substrate can include both natural fibers and synthetic fibers. In some examples, the amount of synthetic fibers represents from about 20 wt% to about 90 wt% of the total amount of fibers. In some other examples, the amount of natural fibers represents from about 10 wt% to about 80 wt% of the total amount of fibers. In some other examples, the fabric substrate includes natural fibers and synthetic fibers in a woven structure, the amount of natural fibers is about 10 wt% of a total fiber amount and the amount of synthetic fibers is about 90 wt% of the total fiber amount. In some examples, the fabric substrate can also include additives such as, but not limited to, one or more of colorant (e.g., pigments, dyes, tints), antistatic agents, brightening agents, nucleating agents, antioxidants, UV stabilizers, fillers, lubricants, and combinations thereof.

[0079] The carbon based layer of the basecoat subsystem of the present invention comprises at least 50 atomic % (at%) of carbon and up to 50 at% of hydrogen. In certain embodiments of the present invention the carbon content of carbon based layers of the present invention may be comprised between 50 at% and 100at%, in particular between 60 at% and 95 at%.

[0080] The carbon based layers of the present invention optionally comprise one or more dopants selected among W, Ti, Si, O, N, B. Any dopants may be present in the carbon based layer at a dopant/carbon ratio comprised between 1at% and 20 at%. When hydrogen is present in the carbon based layer, the dopant content, in atomic percent, may in particular be lower than the hydrogen content, in atomic percent.

[0081] Dopants may be introduced with dopant precursor gases such as for example SihU, TMDSO, HMDSO, Bhh, The flow rates of carbon precursor gases and dopant gases are adapted so as to reach the desired composition of the coating, depending of the respective reactivities of the precursor gases.

[0082] The carbon based layer of the present invention comprises sp2 and sp3 hybridizations in the carbon-carbon bonds. In certain embodiments of the present invention in particular, the hybridization ratio sp3/(sp3+sp2) of carbon in the carbon based coating, that the percentage of sp3 hybridized C-C bonds may be comprised between 5% and 80%, in particular between 10% and 70% in particular between 30% and 60%. Herein the hybridization ratio was determined by Raman spectroscopy.

[0083] Preferably, the silicon oxide based layers of the topcoat subsystem of the present invention comprise or essentially consist of S1O2- _X , x being between 0 and 0.5. A layer may be considered ‘silicon oxide based’ if it comprises at least 50 mol% of Si0 _2-x. Preferably the silicon oxide layer of the topcoat subsystem comprises at least 80 mol% S1O2- _X , more preferably at least 90 mol% of SiC -x. In certain embodiments the silicon oxide based layers comprise or essentially consist of Si0 ₂ . The silicon oxide based layers of the present invention may comprise up to 10 atom% of dopants or precursor residues, in particular from the group consisting of H, C, N, Cl, CH _y derivatives, NH _y derivatives and OH _y derivatives, y being between 1 and 4. This content is preferably determined by photoelectron spectroscopy XPS or by secondary ionization mass spectrometry SIMS; it can also be determined by Raman spectroscopy, by ion beam analysis analytical techniques, such as NRA and RBS, and others. Dopants may be chosen among one or more of Al, Sn or B.

[0084] The silicon oxide based layers of the topcoat subsystem of the present invention are preferably amorphous and homogeneous throughout the layer thickness, as may be determined by cross-sectional transmittance electron microscopy (TEM). In particular, there is no detectable transition in the silicon oxide based layer from a composition comprising more organic residues to a composition of devoid of any organic residues.

[0085] In a coating process of the present invention a single plasma source of hollow cathode type may be used sequentially for activation, basecoat subsystem deposition and topcoat subsystem deposition, by adapting as required the deposition parameters, gases and precursors.

[0086]The present invention in certain embodiments concerns the following items:

Item 1. Process for depositing decorative coating systems on substrates comprising: a. providing a substrate in a vacuum chamber; b. exposing at least part of the surface of the substrate to an activation plasma generated by a first plasma source, of linear hollow-cathode type; c. depositing a basecoat sub-system comprising a layer which is based on carbon on the activated surface of the substrate, using a second plasma source, of linear hollow- cathode type; the layer based on carbon being a hydrogenated amorphous carbon film comprising at least 50 at% of carbon and up to 50 at% of hydrogen and carbon-carbon bonds with sp2 and sp3 hybridizations; d. depositing by physical vapor deposition a PVD coating sub-system on the basecoat, the PVD coating sub-system comprising a first layer comprising Ag, Cu, Al, Cr, a NiCr-alloy, Ti, titanium nitride, silicon, or a NiCrW alloy.

Item 2. Process for depositing decorative coating systems on substrates according to item 1 wherein the substrate is selected among substrates based on polymers, on ceramics, on metals or on glass.

Item 3. Process for depositing decorative coating systems on substrates according to any one preceding item wherein depositing by physical vapor deposition a PVD coating sub-system is performed by magnetron sputtering.

Item 4. Process for depositing decorative coating systems on substrates according to any one preceding item wherein exposing at least part of the surface of the substrate to an activation plasma generated by a first plasma source, of linear hollow-cathode type comprises: a. providing a first plasma source, of linear hollow-cathode type, comprising at least one pair of hollow-cathode plasma generating electrodes connected to an AC, DC or pulsed DC generator, for the activation of the substrate; b. injecting a first plasma generating gas in the first plasma source’s electrodes at a flow rate of between 1000 seem and 5000 seem per linear meter of plasma of the first plasma source; c. applying a first electrical power to the first plasma source, so that the first power density of the plasma is between 2 kW and 20 kW per linear meter of plasma of the first plasma source; d. activating at least part of the substrate’s surface by exposing the substrate to the plasma of the first plasma source.

Item 5. Process for depositing decorative coating systems on substrates according to any one preceding item wherein depositing a basecoat sub-system comprises: a. providing a second plasma source, of linear hollow-cathode type, comprising at least one pair of hollow-cathode plasma generating electrodes connected to an AC, DC or pulsed DC generator, for the deposition of said basecoat on the activated surface of the substrate; b. injecting a second plasma generating gas in the second plasma source’s electrodes at a flow rate of between 1000 seem and 5000 seem per linear meter of plasma of the second plasma source; c. applying a second electrical power to the second plasma source, so that the second power density of the plasma is between 2 kW and 20 kW per linear meter of plasma of the second plasma source; d. injecting a gaseous precursor of carbon at a flow rate of between 50 seem and 600 seem per linear meter of plasma of the second plasma source, the gaseous precursor being preferably injected into the plasma at least between the electrodes of each electrode pair of the second plasma source; e. exposing the substrate to the plasma of the second plasma source.

Item 6. Process for depositing decorative coating systems on substrates according to any one preceding item comprising after depositing the PVD coating subsystem: a. depositing a topcoat subsystem comprising a layer which is based on silicon oxide using a third plasma source, of linear hollow- cathode type.

Item 7. Process for depositing decorative coating systems on substrates according to any one preceding item wherein the basecoat subsystem consists of a single carbon based layer.

Item 8. Process for depositing decorative coating systems on substrates according to any one preceding item wherein the PVD coating subsystem consists of a single metal layer.

Item 9. Process for depositing decorative coating systems on substrates according to any one preceding item wherein the topcoat subsystem consists of a single silicon oxide based layer.

Item 10. Process for depositing decorative coating systems on substrates according to any one preceding item wherein the basecoat subsystem is deposited directly on the substrate.

Item 11. Process for depositing decorative coating systems on substrates according to any one preceding item wherein the PVD coating subsystem is deposited directly on the basecoat subsystem.

Item 12. Process for depositing decorative coating systems on substrates according to any one preceding item wherein the topcoat subsystem is deposited directly on the PVD coating subsystem.

Item 13. Substrate bearing a decorative coating system characterized in that the substrate is selected among substrates based on polymers, on ceramics, on metals or on glass and in that the coating comprises in sequence starting from the substrate surface a. a basecoat subsystem, comprising a layer based on carbon; the layer based on carbon being a hydrogenated amorphous carbon film comprising at least 50 at% of carbon and up to 50 at% of hydrogen and carbon-carbon bonds with sp2 and sp3 hybridizations; b. a physical vapor deposition coating subsystem, comprising a layer based on a material is selected among Ag, Cu, Al, Cr, Ti, Titanium nitride, Si, NiCr-alloys or NiCrW alloys;

Item 14. Substrate bearing a decorative coating system according to item 13 characterized in that it further comprises, above the physical vapor coating subsystem, a topcoat subsystem which comprises a layer based on silicon oxide.

Item 15. Substrate bearing a decorative coating system according to any one of items 13 to 14 characterized in that the physical vapor deposition coating further comprises at least one additional layer, above or below the silicon oxide based layer, the additional layer comprising an oxide or a nitride of a metal, metal alloy or of silicon.

Item 16. Substrate bearing a decorative coating system according to any one of items 13 to 15 characterized in that the thickness of the physical vapor deposition coating subsystem is comprised between 20 nm and 300nm.

Item 17. Substrate bearing a decorative coating system according to any one of items 13 to 16 characterized in that the thickness of the basecoat subsystem is comprised between 2 nm and 200nm.

Item 18. Substrate bearing a decorative coating system according to any one of items 14 to 17 characterized in that the thickness of the topcoat subsystem is comprised between 20 nm and 200nm.

Item 19. Substrate bearing a decorative coating system according to any one of items 13 to 18 characterized in that the hybridization ratio sp3/sp2 of the basecoat subsystem’s layer based on carbon is comprised between 0.6 and 0.8.

Item 20. Substrate bearing a decorative coating system according to any one of items 13 to 19 characterized in that the carbon based layer of the basecoat subsystem is deposited by hollow cathode plasma enhanced chemical vapor deposition.

Item 21. Substrate bearing a decorative coating system according to any one of items 14 to 20 characterized in that the silicon oxide based layer of the topcoat subsystem is deposited by hollow cathode plasma enhanced chemical vapor deposition.

Item 22. Substrate bearing a decorative coating system according to any one of items 13 to 21 wherein the basecoat subsystem consists of a single carbon based Substrate bearing a decorative coating system according to any one of items 9 to 15 wherein the PVD coating subsystem consists of a single metal layer.

Item 23. Substrate bearing a decorative coating system according to any one of items 14 to 22 wherein the topcoat subsystem consists of a single silicon oxide based layer.

Item 24. Substrate bearing a decorative coating system according to any one of items 13 to 23 wherein the basecoat subsystem is in direct contact with the substrate.

Item 25. Substrate bearing a decorative coating system according to any one of items 13 to 25 wherein the PVD coating subsystem is in direct contact with the basecoat subsystem.

Item 26. Substrate bearing a decorative coating system according to any one of items 14 to 25 wherein the topcoat subsystem is in direct contact with the PVD coating subsystem.

[0087] It is noted that the invention relates to all possible combinations of process or substrate features recited in the claims and embodiments mentioned hereinabove and also to substrates bearing a decorative coating that may be obtained by any possible combination of process features recited in the embodiments mentioned hereinabove.

[0088] For the purpose of the present invention any value ranges indicated herein are intended to encompass the boundary values of these value ranges.

Examples

[0089] For the examples below, all deposition conditions were first performed on 4mm thick clear soda lime glass substrates, followed for selected deposition conditions on substrates selected among the following: a. Polyethyleneterephtalate (PET) foils, 125 pm thick b. Textile 1 , 87 % Polyester and 13 % Elastane c. Textile 2, 100% Polyamide d. Textile 3, Polyester e. Textile 4, PVC coated polyester f. Textile 5, glass-fiber based

[0090] The textiles may be woven or non-woven. The prior deposition on glass susbtrates allows for an easier determination and tuning of layer thicknesses.

[0091] Activation and coating deposition rates and/or durations of exposure were adjusted by modifying travel speeds of the substrate underneath the plasma/sputtering sources and/or by repeating the treatment or coating.

[0092] For the purpose of the present examples, the following parameters were not varied. TMDSO is tetramethyl disiloxane. Two alternative types of basecoat subsystems were tested, one being a silicon oxide based basecoat, the other a carbon layer based basecoat. A pressure of between 0.020 Torr and 0.030 Torr was maintained for all process steps involving a hollow cathode plasma source.

[0093] Table 1

[0094] For the PVD subsystem a layer a linear aluminum target was sputtered using a magnetron sputtering device at a power of 1.25 kW/m and under an Argon flow rate of 123 sccm/m. The pressure was maintained at between 0.004 Torr and 0.010 Torr. The deposited Aluminum layer thicknesses are given in the Table 2 below.

[0095] For the different examples the layer thicknesses are given in Table 2 below. Basecoat ‘A’ is a silicon oxide based layer and basecoat ‘B’ is a carbon based layer of the present intvention. [0096] Table 2

[0097] Examples 1 to 6 and example 12 and 18 are comparative examples. Examples 7 to 11, 13 to 17 and example 19 are according to the present invention.

[0098] Mechanical durability was evaluated by abrasion tests using two different abrasion testing methods. One test method is the automatic wet rub test (AWRT), the other test method, which is harsher, is the crockmeter test. [0099] Table 3

[0100] Samples made without plasma activation were all less durable than those made with activation. This can be seen when comparing examples 1 and 2 or see for example 7 and 18. As can be seen in Table 3, examples with a Silicon oxide based basecoat were also less resistant than those with a carbon based basecoat.

[0101] Addition of the optional topcoat has a significant impact on the mechanical resistance, as can be seen when comparing example 19 with example 7.

[0102] The deposition conditions of example 16 were reproduced on all PET and textile substrates mentioned above. The deposited coatings were in all instances highly reflective and uniform. The adherence was evaluated by manually rubbing the samples on a flat surface with a paper towel and no delamination was observed. The visible light reflectance of the coated side of these samples was similar to the visible light reflectance of example 16.

[0103] For the Automatic Wet Rub Test (AWRT) a piston covered with a wet cotton cloth, that is kept wet with distilled water throughout the test, is brought into contact with the layer to be evaluated and moved back and forth over its surface. The piston bears a weight so as to apply a force of 33 N to a Teflon coated cylindrical finger having a diameter of 17 mm. The rubbing of the cotton over the coated surface damages and removes the layer after a certain number of cycles. For the purpose of the present invention the damage was assessed after 1000 cycles of the test unless otherwise noted. In the order of increasing durability, the coating would be completely removed, partially removed, scratched or show no visible damage. The samples were assessed by the naked eye under a uniform artificial sky at a distance of 80 cm from the sample.

[0104] The crockmeter test is a dry rub test performed as described in standard IS011998:1998 with a cylindrical finger having a diameter of 15mm and a 9pm, 1200 grain, sandpaper pad. For the present invention the cycles are performed on a dry sample, without addition of any liquid. The total weight on the abrasive pad is 900g.

[0105] Analysis of the carbon based basecoats in the examples 7 to 11 and 13 to 19 above showed that the carbon in these layers had a hybridization ratio sp3/sp2 comprised between 0.6 and 0.8. Flerein the hybridization ratio was determined by Raman spectroscopy using a LabRAM300 Raman spectrometer and three measurements per sample. Visible light reflectance of these samples on the coated side was comprised between 71% and 88%.

[0106] Further examples were prepared using Ag, Cu, and Al on different textile substrates. Flere the abrasion resistance with and without a carbon based basecoat were compared. Examples 20, 22, 24, 26, and 27 are comparative examples. Examples 21, 23, 25, 27, and 29 are in accordance with the present invention. Examples 20 to 29 were prepared without a topcoat. [0107] For the PVD subsystem a layer a linear metal target was sputtered using a magnetron sputtering device at a power of 1.25 kW/m for Ag and 2.5 kW/m for Al and Cu, and under an Argon flow rate of about 170 sccm/m. The pressure was maintained at between 0.003 Torr and 0.010 Torr.

[0108] In examples 20 to 29, activation was performed using the 1 ^st plasma source with a N2 plasma generating gas at a flow rate of 2500 sccm/m and a power of 4.4 kW/m. The carbon based layer was deposited using the 2 ^nd plasma source under the same conditions as for examples 7 to 11 and 13 to 19 above and also showed a hybridization ratio sp3/sp2 comprised between 0.6 and 0.8. Table 4 shows the susbtrates and PVD susbsystem metals used in examples 20 to 29.

[0109] Table 4

[0110] Table 5 below shows the basecoat layer thickness (if rpesent) anf PVD subsystem metal layer thickness for examples 20 to 29. [0111]Table 5

[0112]The abrasion resistance of examples 20 to 29 was evaluated by measuring the emissivity of these coatings before and after abrasion. For the abrasion the automatic wet rub test described hereinabove was performed at 400 cycles, 500 cycles or 1000 cycles. The emissivity was determined in accordance with standard EN15976:2011. A higher increase of emissivity indicates a higher level of abrasion. Example 20 can be compared to Example 21, Example 22 to 23, Example 24 to 25, Zxample 26 to 27, and Example 18 to 29.

[0113] Table 6

[0114] As can be seen from Table 6, the presence of the carbon based basecoat reduces the emissivity increase after AWRT abrasion, indicating an improvement of the mechanical durability of the coatings due to the carbon based basecoat, even without a protective topcoat.