Decorative coated polymer substrate and method for obtaining same

Abstract

The present invention relates to a polymer substrate with a decorative coating comprising a protective top layer of a boron-doped silicon oxide wherein the boron-doped silicon oxide comprises Si, O, B, H, and OH groups wherein the boron content is between 4 at% and 12 at%. The invention further comprises a method for depositing a boron-doped silicon oxide layer on a polymer substrate by means of PECVD of the linear hollow cathode type, said boron-doped silicon oxide layer comprising Si, O, B, H and OH groups, and wherein the boron content is between 4 at% and 12 at%.

Description

Technical Field

[0001] The present invention relates to a polymer substrate with a decorative coating, the decorative coating comprising a boron-doped silicon oxide protective top layer. The present invention also relates to a plasma enhanced chemical vapor deposition method for depositing a decorative coating comprising a boron-doped silicon oxide protective top layer on a polymer substrate. Background Art

[0002] Uncoated polymer substrates, such as acrylonitrile butadiene styrene (ABS) or polycarbonate (PC) possibly blended with ABS, typically have a dull appearance and therefore are typically provided with a coating to increase the amount of reflected light to make it more aesthetically pleasing.

[0003] Furthermore, such polymer substrates are frequently used in applications where they are exposed to mechanical wear, in particular scratching.

[0004] It is known that lacquer layers can be added to polymer substrates for both mechanical protection and aesthetic purposes. However, it has been found that the protection provided by these lacquer layers still needs improvement, at least in terms of scratch resistance. In addition, such lacquer layers are thick, with thicknesses far exceeding 1 μm, and require large amounts of chemicals in a time-consuming deposition process.

[0005] Some polymer substrates are provided with a metal layer to give them the appearance of metal parts. Such coated polymer substrates can be used as replacements for metal parts, in particular metal parts with a decorative function, in particular on vehicles. These metal layers also need to be protected from mechanical wear and chemical attack (e.g. oxidation).

[0006] Therefore, there is a need in the art for layers that increase the resistance of polymeric substrates to chemical and / or mechanical degradation and improve their aesthetic appearance. Summary of the invention

[0007] The object of the present invention is to produce a usable polymeric substrate which is mechanically durable, has good adhesion properties, and is particularly wear-resistant, while providing a desirable aesthetic appearance.

[0008] The present invention therefore relates to a polymer substrate with a coating comprising a protective top layer of boron-doped silicon oxide, wherein the boron-doped silicon oxide comprises Si, O, B and OH groups and wherein the boron content is between 4 and 12 atomic %.

[0009] In certain embodiments of the present invention, the protective top layer of boron-doped silicon oxide is the only layer of the decorative coating.

[0010] In certain embodiments of the present invention, the decorative coating includes one or more layers between the substrate and the protective top layer of boron-doped silicon oxide.

[0011] Another object of the present invention is to provide a fast and efficient method for depositing a coating on a polymer substrate, the coating comprising a protective top layer of boron-doped silicon oxide, wherein the boron-doped silicon oxide contains Si, O, B and OH groups and wherein the boron content is between 4 atomic % and 12 atomic %.

[0012] In certain embodiments of the present invention, a method for depositing a boron-doped silicon oxide protective layer (comprising Si, O, B and OH groups, and wherein the boron content is between 4 atomic % and 12 atomic %) on a polymer substrate comprises:

[0013] a. providing a polymer substrate,

[0014] b. providing a linear hollow cathode type plasma source, the length of which includes at least one pair of hollow cathode plasma generating electrodes, and the plasma source includes at least one electrode pair connected to an AC, DC or pulsed DC generator power supply for depositing the protective layer on the substrate,

[0015] c. injecting a plasma containing oxygen into the electrode of the plasma source to generate a reactive gas at a flow rate of 125 sccm to 750 sccm per meter of plasma source length,

[0016] d. applying an electric power of 10 kW to 50 kW per meter of plasma source length to the plasma source, and

[0017] e. injecting a precursor gas at a flow rate of 500 sccm to 2500 sccm per linear meter of plasma source length, wherein the precursor gas is injected into the plasma at least between the electrodes of each electrode pair of the plasma source, and depositing the protective layer on the polymer substrate by exposing the substrate to the plasma of the plasma source. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] For a more complete understanding of the nature of the present invention, reference is made to the following detailed description in conjunction with the accompanying drawings, in which:

[0019] Figures 1 to 3 Different polymer substrates with decorative coatings including a protective top layer of boron-doped silicon oxide according to embodiments of the present invention are shown.

[0020] Figure 4 Shown is a cross section of a hollow cathode type linear plasma source comprising an electrode pair for depositing the protective layer of the present invention.

[0021] Figure 5 A deposition cross-sectional view of a hollow cathode type linear plasma source is shown for continuously depositing the protective layer of the present invention relative to a substrate. DETAILED DESCRIPTION

[0022] The inventors have surprisingly found that the protective top layer of the present invention provides an improved aesthetic appearance to a polymeric substrate by increasing the gloss of the polymeric substrate (as determined by gloss measurements) and furthermore provides good mechanical resistance in abrasion tests.

[0023] Preferably, the decorative coating does not include any organic adhesion layer or polymer primer. If present, the metallic coating may be in direct contact with the substrate, or the protective top layer may be in direct contact with the substrate. Figure 1 A polymer substrate (10) is shown, wherein a protective top layer (1) is in direct contact with the substrate. Figure 2 A polymer substrate (10) is shown, wherein a metal coating (2) is in direct contact with the substrate and a protective top layer (1) is in direct contact with the metal coating (1).

[0024] The polymer substrates of the invention can be used as decorative elements in various applications, for example on electrical appliances, electronic devices, furniture or architectural elements. Their enhanced durability makes them particularly suitable for use on vehicles, for example on cars. This latter application is particularly interesting when the substrate is polymer-based and is used as a replacement for metal parts that fulfill at least a decorative function.

[0025] Decorative coatings on polymeric substrates may also include a metallic coating between the substrate surface and the protective top layer.

[0026] The metal coating may comprise one or more metal layers. The layers of the metal coating may have a thickness of up to 1 μm. Such a metal coating provides a metallic appearance to the polymer substrate, allowing it to be used as a substitute for metal parts. The protective top layer protects the metal layer from scratches and chemical attack. Preferably, the one or more layers of the metal coating are deposited by magnetron sputtering.

[0027] Advantageously, the metal coating is in direct contact with the polymer substrate and / or the protective top layer.

[0028] According to an embodiment of the present invention, the metal coating comprises one or more layers comprising a material selected from Ag, Cu, Al, Cr, Zr, Ti, Si, NiCr alloy or NiCrW alloy.

[0029] In an advantageous embodiment of the invention, the metal coating comprises two layers. Advantageously, a first adhesion metal layer of NiCr is in direct contact with the polymer substrate and in direct contact with a second layer of a metal selected from Ag, Cu, Al, Cr, Zr, Ti, Si or a NiCrW alloy. The first layer can then provide improved adhesion between the second layer and the substrate.

[0030] The boron doped silicon oxide protective top layer of the present invention contains OH groups. The presence of OH groups is a feature that distinguishes these coatings from magnetron sputtered coatings (which do not provide the same level of protection). To the best of the inventors' knowledge, the protective ability of the boron doped silicon oxide layer of the present invention may be due at least in part to this combination of OH groups and boron doping. The presence of OH groups can be determined by Fourier transform infrared spectroscopy (FTIR) on an equivalent protective top layer deposited on a silicon substrate. The presence of OH groups in the protective top layer is determined by the presence of OH groups at 3300 cm -1 Up to 3500cm -1 The absorption peak corresponding to the stretching vibration of -OH can be detected by the presence of an absorption peak at the wave number of , which corresponds to the stretching vibration of -OH. Another absorption peak corresponding to the stretching vibration of Si-OH can be detected at 900cm -1 Up to 1000cm -1 However, these peaks can overlap with the more intense peaks of Si-O stretching vibrations.

[0031] In an embodiment of the present invention, -OH stretching vibration (A OH ) and Si-O-Si stretching vibration (A SiOSi )'s FTIR absorption peak area is A OH / A SiOSi The absorption peak of -OH stretching vibration appears at 3300 cm -1 Up to 3500cm -1 The absorption peak of Si-O-Si stretching vibration appears at 1080 cm -1 Up to 1090cm -1 The wave number of .

[0032] In SiO2-based coatings deposited by sputtering, some hydrogen may be present inadvertently in the gas phase, but in decorative coatings, the FTIR absorption peak area is found to be larger than A. OH / A SiOSi Less than 0.05. In addition, SiO2-based coatings deposited by sputtering usually contain aluminum because aluminum is added to silicon sputtering targets to improve their electrical conductivity. The boron-doped silicon oxide layer of the present invention may be free of aluminum.

[0033] The boron-doped silicon oxide layer of the present invention was found to be amorphous and non-porous, as seen, for example, by transmission electron microscopy.

[0034] The boron-doped silicon oxide layer of the present invention includes, or may consist essentially of, silicon, boron, oxygen, and hydrogen.

[0035] In any of the above embodiments, the boron content of the boron-doped silicon oxide layer may be 4 to 12 atomic % B. In this doping range, the refractive index can be kept very low, i.e., 1.4 to 1.5 at a wavelength of 633 nm, in particular if the SiO2 weight content is at least 80%. At the same time, good chemical resistance of the multilayer coating is obtained, and the haze level after thermal strengthening can be kept low, in particular, can be kept at a value below 0.3%.

[0036] The boron content in the boron-doped silicon oxide layer is preferably determined by quantitative evaluation by x-ray photoelectron spectroscopy (XPS) or by secondary ionization mass spectroscopy (SIMS) using appropriate standards.

[0037] According to an embodiment of the present invention, the boron-doped silicon oxide protective top layer may have a thickness of at least 80 nm to show a more significant durability improvement. The thickness may be adjusted within a wide range to adjust the optical properties of the final coated product. Thus, the boron-doped silicon oxide layer may have a thickness of at most 400 nm, in particular at most 350 nm, more particularly at most 300 nm. Due to the slow deposition rate of silicon oxide-based coatings, such a high thickness is not suitable for magnetron sputtering deposition.

[0038] According to an embodiment of the present invention, the boron-doped silicon oxide layer of the present invention may have an O / Si atomic ratio between 1.9 and 2.6. It was found that at lower boron doping levels, the O / Si atomic ratio was lower.

[0039] According to an embodiment of the invention, the boron-doped silicon oxide coating of the invention may in particular be free of carbon. The absence of carbon is particularly interesting for reducing the absorptivity of the layer and helps to reduce the number of defects that occur when the coated product is thermally strengthened. In addition to the complexity of integrating the sol-gel coating process in a multilayer coating process, the presence of carbon is also a significant disadvantage of sol-gel coatings.

[0040] For the purposes of the present invention, a layer is considered to be free of carbon when no carbon signal is detectable above the signal noise of carbon in the X-ray fluorescence spectrum or the secondary ion mass spectrometry signal. It should be noted that surface contamination, especially carbon, which is naturally present on the coating when exposed to free air should be ignored during the analysis.

[0041] The boron-doped silicon oxide protective top layer of any embodiment or combination of the above embodiments can be advantageously deposited using plasma enhanced chemical vapor deposition (PECVD), in particular using a linear plasma source (e.g., a hollow cathode plasma source). By operating under vacuum, PECVD can be easily integrated into a vacuum coating production line (e.g., a magnetron sputtering production line).

[0042] The present invention relates in an embodiment to a method of depositing a decorative coating on a polymer substrate, the decorative coating comprising a protective top layer of boron-doped silicon oxide, wherein the protective top layer comprises Si, O, B and OH groups, and wherein the boron content is between 4 atomic % and 12 atomic %, the method comprising:

[0043] a. providing a polymer substrate,

[0044] b. providing a linear hollow cathode type plasma source having a length comprising at least one pair of hollow cathode plasma generating electrodes connected to an AC, DC or pulsed DC generator power supply for depositing said protective top layer on a substrate,

[0045] c. injecting a plasma containing oxygen into the electrode of the plasma source to generate a reactive gas at a flow rate of 125 sccm to 750 sccm per meter of plasma source length,

[0046] d. applying an electric power of 10 kW to 50 kW per linear meter of plasma source length to the plasma source to generate plasma, and

[0047] e. injecting a precursor gas containing boron, silicon and hydrogen at a flow rate of 500 sccm to 2500 sccm per linear meter of plasma source length, wherein the precursor gas is injected into the plasma at least between the electrodes of each electrode pair of the plasma source, and depositing a protective top layer on the polymer substrate by exposing the substrate to the plasma of the plasma source.

[0048] Standard cubic centimeter per minute (sccm) is a unit of flow measurement that represents the volume of a fluid at standard conditions of temperature and pressure. 3 These standard conditions are applicable to the present invention and are fixed at a temperature of 0° C. (273.15 K) and a pressure of 1.01 bar.

[0049] According to an embodiment of the present invention, the multilayer coating further comprises one or more layers deposited, for example, by magnetron sputtering and / or PECVD. Optionally, additional coatings may be deposited by the same technique, for example after the protective top layer is deposited. Thus, a multilayer coating comprising a boron-doped silicon oxide protective layer as described above may be formed.

[0050] Step b) of the method of the present invention requires a low-pressure PECVD plasma source, the pressure of which is preferably between 0.13 Pa and 66.66 Pa (0.001 Torr and 0.5 Torr), preferably between 0.13 Pa and 4.00 Pa, more preferably between 0.40 Pa and 2.67 Pa, the device being provided with a hollow cathode type linear plasma source comprising at least one electrode pair connected to an AC or pulsed DC generator, the frequency of which is generally between 5 kHz and 150 kHz, preferably between 5 kHz and 100 kHz, or connected to a DC generator. The pressure is maintained by a vacuum pump.

[0051] Examples of PECVD devices are described below. The PECVD source is connected to a vacuum chamber or is arranged in a vacuum chamber. The vacuum chamber is arranged so that it can have multiple PECVD devices or other deposition sources with different deposition forms next to each other in the same vacuum chamber or in separate connected vacuum chambers. In some applications, these other deposition sources (which allow different deposition forms) are planar cathodes or rotating cathodes for magnetron sputtering deposition. The deposition sources are selected and combined in a coating machine to provide a deposition process of a multilayer coating including a protective top layer of the present invention, especially in a coating having a size of at least 3.2x6m 2 Deposition process on glass substrate.

[0052] The vacuum chamber may be part of a horizontal coater or a vertical coater and may also include a transfer chamber.

[0053] Linear plasma sources are particularly useful for depositing uniform layers on large substrates in dynamic or continuous coating processes. A linear plasma source is placed perpendicular to the direction of travel of the substrate so as to span across the width of the substrate in its longitudinal direction. The advantage of linear plasma sources is their scalability. Thus, their length can be adapted to span substrates of different widths, the applied power as well as the gas and precursor flow rates being adjusted proportionally to the length. The width of a linear plasma source extends parallel to the direction of travel of the substrate. Showerhead type plasma sources or point plasma sources are particularly less suitable for depositing uniform layers on large substrates larger than 1 x 1m 2 Large substrates that extend over large areas are often difficult to coat, as coating such large substrates requires complex arrangements, such as an array of multiple sources, and uniformity is difficult to achieve.

[0054] A "hollow cathode type plasma source" refers to a plasma or ion source comprising one or more electrodes configured to produce a hollow cathode discharge. An example of a hollow cathode plasma source is described in US8652586, the entire contents of which are incorporated herein by reference. Figure 4A hollow cathode type plasma source that can be used in the present invention is shown. The plasma source includes at least one pair of hollow cathode electrodes (41, 42) arranged in parallel and connected by an AC power supply (not shown). An electrically insulating material (43) is arranged around the hollow cathode electrode. Plasma generating gas is supplied via inlets (44) and (45). Precursor gas is supplied via a precursor gas inlet (46) and introduced into a plasma curtain (49) through a manifold (47) and a precursor injection slot (48) in the dark space between the electrodes. The AC power supply provides 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 to form, and drives the second electrode to a positive voltage to serve as the anode of the voltage application circuit. This then drives the first electrode to a positive voltage and reverses the role of the cathode and anode. When one of the electrodes is driven negative, a discharge (41a, 42a) is formed in the corresponding cavity. The other electrode then forms an anode, allowing electrons to escape the plasma through an outlet (41b, 42b) and travel to the anode side, thereby completing the circuit. Therefore, as Figure 5 As shown, a linear plasma (49) having a curtain shape is formed in the region above the substrate and between the first electrode and the second electrode. This method of driving the hollow cathode with an AC power source helps to form a uniform linear plasma across the substrate (10), wherein the length (L12) of the plasma source is perpendicular to the traveling direction (T) of the substrate, and the width (W12) of the plasma source is parallel to the traveling direction (T) of the substrate.

[0055] In a linear hollow cathode type plasma source, a uniform plasma can be generated without relying on closed-circuit electron drift. "Closed-circuit electron drift" refers to the electron flow caused by crossed electric and magnetic fields. In many conventional plasma forming devices, closed-circuit electron drift forms a closed loop path or "racetrack" for electron flow.

[0056] "Alternating current (AC)" refers to electrical power from an alternating current source in which the voltage varies at some frequency in a sinusoidal, square wave, pulsed, or some other waveform. The voltage variation is typically from negative to positive, i.e., relative to ground. When in bipolar form, the power output delivered by the two leads is typically about 180° out of phase.

[0057] An "electrode" provides free electrons during plasma generation, for example, when the electrode is connected to a power source that provides a voltage. The electron emitting surfaces of the hollow cathode are collectively considered to be one electrode. The electrodes can be made of materials well known to those skilled in the art, such as steel, stainless steel, copper, or aluminum. However, for each plasma enhanced process, these materials must be carefully selected because different gases may require different electrode materials to initiate and maintain a plasma during operation. By providing the electrodes with a coating, the performance and / or durability of the electrodes can also be improved.

[0058] For any plasma source of the present invention, the power density of the plasma is defined as the power consumed in the plasma generated at the electrode, referenced to the size of the plasma. In a linear hollow cathode type plasma source, the "power density of the plasma" can be defined as the total power applied to the plasma source divided by the total length of the plasma source.

[0059] "Plasma length in linear meters" refers to the length of the plasma, which is defined as the distance between the ends of the plasma generated by a pair of electrodes in a direction transverse to the direction of travel of the substrate to be coated. When the plasma source includes more than one pair of electrodes, the length of the plasma is defined as the sum of the distances between the ends of the plasma generated by each pair of electrodes in a direction transverse to the direction of travel of the substrate to be coated. It will be well understood by those skilled in the art that these linear hollow cathode plasma sources are scalable in that their length can be adjusted to span the width of the substrate to be treated. The plasma source length can be, for example, several meters. Therefore, it makes sense to express the flow rate and applied power in units based on the total length of the plasma source, because, for example, doubling the length of the plasma source obviously requires doubling the applied power and flow rate.

[0060] As used herein, the following terms have the following meanings: As used herein, "a," "an," and "the" refer to both the singular and the plural, unless the context clearly dictates otherwise. For example, a "cavity" refers to one or more cavities.

[0061] As used herein, "comprise", "comprising", "comprises" and "comprised of" are synonymous with "include", "including", "includes" or "contain", "containing", "contains", and are inclusive or open terms that specify the presence of the following content (e.g., components) but do not exclude or prevent the presence of other unrecorded components, features, elements, components or steps known in the art or disclosed therein.

[0062] The recitation of numerical ranges by endpoints includes all numbers and fragments subsumed within that range, as well as the recited endpoints.

[0063] The paired electrodes forming a chamber in which plasma discharge occurs are each connected to a pipe for introducing a plasma-generating reaction gas, and are provided with openings from which ionized gas (ie, plasma) is discharged.

[0064] The frequency of the power supply connected to the electrodes may be between 5 kHz and 150 kHz, preferably between 5 kHz and 100 kHz.

[0065] The at least one pair of electrodes of the linear plasma source may have a length of 250 mm to 4000 mm and a width of 100 mm to 800 mm.

[0066] Such values ​​have the advantage of ensuring that the amount of reactive gas is sufficiently greater than the amount of precursor so that carbon incorporation into the layer can be controlled and / or avoided.The applied power, reactive gas flow rate and precursor flow rate are adjusted in proportion to the length of the linear plasma source.

[0067] The power supplied by the power source is preferably between 5 kW and 50 kW per linear meter of plasma source length, advantageously between 10 kW and 35 kW per linear meter of plasma source length. Below a power of 5 kW per linear meter of plasma source, the presence of carbon in the protective top layer is observed, and above 50 kW per linear meter of plasma source, arc formation is observed, which is detrimental to the lifetime of the plasma source and / or the quality of the decorative coating.

[0068] The reaction gas comprises oxygen or an oxygen-containing derivative, which is preferably selected from the group consisting of ozone, hydrogen peroxide, water and CO2. According to an embodiment, the reaction gas may also advantageously comprise an inert gas, such as helium, nitrogen, argon, neon or krypton, to promote the chemical dissociation of the precursor and control the ion bombardment of the source. If present, the percentage of inert gas in the reaction gas is from 2% to 50% by volume, preferably from 3% to 10% by volume, more preferably from 4% to 7% by volume. This choice makes it possible to control the coverage of the obtained layer.

[0069] The reaction gas is preferably O2 or an O2-Ar mixture.

[0070] In an embodiment of the present invention, the flow rate of the reaction gas is 2000 sccm to 5000 sccm per linear meter of the plasma source length.

[0071] A precursor gas containing boron, silicon and hydrogen is injected into the plasma uniformly along the length of the plasma source. The precursor can be injected, for example, between electrodes of an electrode pair, and / or between adjacent electrode pairs if more than one electrode pair is present. The precursor gas is activated by the plasma. A substrate is brought close to the source and a thin layer is deposited on the substrate by the activated gas.

[0072] The flow rate of the precursor gas is preferably between 125 sccm and 750 sccm per linear meter of plasma source length. Typically, if the precursor gas comprises a mixture of precursors, the flow rate of the precursor gas is the sum of the flow rates of the precursors in the mixture.

[0073] The distance between the substrate surface and the opening of the plasma source through which the plasma is emitted from the source is preferably at least 2.0 cm to 20 cm, more preferably at least 4 cm to 15 cm.

[0074] Preferably, the ratio of the flow rate of the reactive gas to the flow rate of the precursor gas is at least 3, advantageously between 3 and 50.

[0075] The precursor gas comprises silicon, boron and hydrogen, and may in particular also comprise carbon and / or oxygen.

[0076] The precursor gas may include a single precursor, i.e. a single precursor, or may include a mixture of precursors, i.e. a mixture of different precursors of different compositions. The ratio of the precursors is adjusted to set the boron doping to a desired level, in particular a boron content of 4 to 12 atomic % B in the boron-doped silicon oxide layer.

[0077] According to an embodiment of the present invention, the precursor gas includes at least one precursor containing Si, at least one precursor containing B, and / or at least one precursor containing Si and B. Any precursor in the precursor gas may also contain hydrogen. Any precursor in the precursor gas may also contain carbon. Any precursor may also contain oxygen.

[0078] During the deposition of the protective top layer, the substrate may reach a temperature between 20° C. and 60° C., depending on the residence time of the substrate in the plasma, for example on the displacement speed of the substrate under the plasma source.

[0079] In an embodiment of the present invention, the silicon-containing precursor is free of boron, ie does not contain boron, and preferably has formula (I), formula (II), formula (III), formula (IV) or formula (V).

[0080] Y1-X-Y2 (I)

[0081] or -[Si(CH3) q (H) 2-q -X-] n - (II)

[0082] or CH2=C(R1)-Si(R2)(R3)-R4 (III)

[0083] or R5-Si(R6)(R7)-R8 (IV)

[0084] or CH2=C(R9)C(O)-O-(CH2) p -Si(R 10 )(R 11 )-R 12 (V)

[0085] Wherein, for formula (I), X is O or NH, Y1 is -Si(Y3)(Y4)Y5, and Y2 is Si(Y 3' )(Y 4' )Y 5' , among which, Y3, Y4, Y5, Y 3' , Y 4' and Y 5' Each is independently H, or an alkyl group of up to 10 carbon atoms; wherein at most one of Y3, Y4 and Y5 is hydrogen, Y 3' , Y 4' and Y 5' at most one of the carbon atoms is hydrogen; and the total number of carbon atoms does not exceed 20.

[0086] wherein formula (II) is cyclic, wherein n is 2 to 10, wherein q is 0 to 2, and wherein the total number of carbon atoms does not exceed 20.

[0087] wherein, for formula (III), R1 is H or an alkyl group, such as -CH3, and wherein R1, R2 and R3 are each independently H, an alkyl group of up to 10 carbon atoms, or an alkoxy group -OZ, wherein Z is preferably -C t H 2t+1 , where t is from 1 to 10.

[0088] wherein, for formula (IV), R5 is H or an alkyl group, such as -CH3, and wherein R6, R7 and R8 are each independently H, an alkyl group of up to 10 carbon atoms, or an alkoxy group -OZ, wherein Z is preferably -C t H 2t+1 , where t is from 1 to 10.

[0089] Wherein, for formula (V), R9 is H or alkyl, such as -CH3, wherein p is 0 to 10, and wherein R 10 , R 11 and R 12 Each is independently H, an alkyl group of up to 10 carbon atoms, or an alkoxy group -OZ, wherein Z is preferably -C t H 2t+1 , where t is from 1 to 10.

[0090] The alkyl group may be straight chain or branched, but a straight chain group is preferred. Such an alkyl group is suitably a methyl group or an ethyl group, wherein a methyl group is preferred. 3' , Y 4' or Y 5' All are alkyl.

[0091] The alkoxy group may be straight chain, branched or cyclic, but a straight chain group is preferred. Such an alkoxy group is suitably a methoxy group or an ethoxy group.

[0092] The silicon-containing precursor of formula I may be a precursor containing six methyl groups. Suitably, the silicon-containing precursor of formula I is hexamethyldisiloxane (HMDSO), hexamethyldisilazane or tetramethyldisiloxane (TMDSO).

[0093] The silicon-containing precursor of formula II may be a precursor wherein n is 3, or n is 4, or n is 5, or n is 6. Suitably, the silicon-containing precursor of formula II is octamethylcyclotetrasiloxane. Suitably, the silicon-containing precursor of formula II is hexamethylcyclotrisilazane.

[0094] The silicon-containing precursor of formula V may be wherein p is 2 and wherein R 10 , R 11 and R 12 Each of is a precursor of an alkoxy group (eg, methoxy group). Suitably, the silicon-containing precursor of formula V is 3-(trimethoxysilyl)propyl methacrylate. Suitably, the silicon-containing precursor of formula V is 3-(trimethoxysilyl)propyl acrylate.

[0095] In an embodiment of the present invention, the boron-containing precursor is free of silicon, meaning it contains no Si, and preferably has formula (VI):

[0096] R 13 -B(R 14 )(R 15 )(VI)

[0097] Among them, R 13 , R 14 and R 15 Each is independently H, an alkyl group of up to 10 carbon atoms, or an alkoxy group -OZ, wherein Z is preferably -C t H 2t+1 , where t is from 1 to 10.

[0098] The alkyl group may be straight chain or branched, but a straight chain group is preferred. Such an alkyl group is suitably a methyl group or an ethyl group, among which a methyl group is preferred.

[0099] The alkoxy group may be straight chain, branched or cyclic, but a straight chain group is preferred. Such an alkoxy group is suitably methoxy, ethoxy or isopropoxy.

[0100] In an embodiment of the present invention, for formula (VI), R 13 , R 14 and R 15 All are ethoxy, or R 13 , R 14 , R 15 All are isopropoxy.

[0101] In an embodiment of the present invention, the boron and silicon containing precursor has formula (VII):

[0102] R 16 OB(-OR 17 )(-OR 18 )(VII)

[0103] Among them, R 16 , R 17 and R 18 Each is independently an organosilicon group, in particular a trialkylsilyl group, an alkyl group of up to 10 carbon atoms. Suitably, the trialkyl group is a trimethylsilyl group, a triethylsilyl group, or a diethyl(methyl)silyl group. Suitably, the boron and silicon precursor is tris(trimethylsilyl)borate (TTMSB).

[0104] Preferably, boron, silicon, and / or any precursors of silicon and boron are delivered to the plasma source without the use of a carrier gas. However, in some embodiments, an additional gas may be used as a carrier gas to introduce the precursors into the plasma chamber.

[0105] Preferably, any precursor is supplied as a liquid which is subsequently vaporized and delivered to the plasma source in its vaporized form. Preferably, any vaporized precursor is delivered to the plasma chamber without the use of a carrier gas. Alternatively, if desired, a liquid precursor supply system delivers the vaporized precursor to the plasma chamber using a carrier gas.

[0106] Preferably, when a carrier gas is used, the carrier gas is selected from N2, He or Ar, and / or any mixture of these gases. In a preferred process, a single carrier gas is used. This is most preferably He or Ar.

[0107] Preferably, when a carrier gas is used, the amount of carrier gas is from about 5% to about 1500% carrier gas, preferably from about 10% to about 1000% additional gas, more preferably from 20% to 750%, such as 25% to 500%, such as 500%, 450%, 400%, 350%, 300%, 250%, 200%, 175%, 150%, 125%, 100%, 90%, 80%, 75%, 70%, 60%, 50%, 40%, 35%, 30% or 25% carrier gas based on the total flow of all silicon and boron precursors.

[0108] Any of the precursors may be gaseous at room temperature and pressure, or may be a vaporized liquid.

[0109] In order to obtain a high dynamic deposition rate of about 20 nm.m / min to 500 nm.m / min, the following flow rates of different precursors are necessary. Generally, higher precursor flow rates require higher power to be applied to the plasma source.

[0110] In an embodiment of the present invention, the total flow rate of the silicon-containing precursor is 10 sccm to 500 sccm (standard cubic centimeters per minute) per linear meter of plasma length, preferably 50 sccm to 500 sccm, or 50 sccm to 400 sccm per linear meter of plasma length.

[0111] The unit "nm.m / min" is used in this application to express deposition rate. This unit is a combination of SI units and is commonly used to characterize the deposition rate of a dynamic or continuous coating process (i.e., a process in which the substrate moves continuously through the deposition device). The deposition rate of such a deposition device is usually called the "dynamic deposition rate" and is used to represent the deposition rate of the decorative coating device itself, regardless of the speed at which the substrate moves through the deposition device.

[0112] In an embodiment of the present invention, the total flow rate of the boron-containing precursor is 10 sccm (standard cubic centimeters per minute) to 500 sccm per linear meter of plasma length, preferably 50 sccm to 500 sccm, or 50 sccm to 400 sccm per linear meter of plasma length.

[0113] In an embodiment of the present invention, the total flow rate of the silicon and boron containing precursors is 10 sccm (standard cubic centimeters per minute) to 750 sccm per linear meter of plasma length, preferably 50 sccm to 750 sccm, or 50 sccm to 600 sccm per linear meter of plasma length.

[0114] Optionally, step c) may additionally comprise applying additional precursors to the substrate, for example in order to include specific additional oxides, such as titanium oxide or zirconium oxide, to further improve the mechanical and / or chemical durability and / or to increase the refractive index of the boron-doped silicon oxide protective top layer.

[0115] According to an embodiment of the present invention, the boron-doped silicon oxide protective top layer contains at least 80 wt % silicon oxide SiO 2 .

[0116] According to an embodiment of the present invention, the boron-doped silicon oxide protective top layer contains up to 15 wt % of titanium oxide, zirconium oxide or a mixture thereof.

[0117] The invention is defined in the appended independent claim. Preferred embodiments are defined in the dependent claims.

[0118] It should be noted that the present invention relates to all possible combinations of features recited in the claims or in the above-described embodiments.

[0119] In an embodiment of the invention, the decorative coating comprises a metal coating located between the substrate and the protective top layer. Preferably, the metal coating is deposited on the polymer substrate before depositing the protective top layer. The metal coating may comprise one or more metal layers.

[0120] The deposition of metal coating is preferably carried out using physical vapor deposition process, advantageously using conventional magnetron sputtering process well known in the art.Representative description of sputtering deposition process and equipment can be found in, for example, US4204942A, US4948087A, US5589280A, US20110275262A1, KR20120026936A and EP0546470A1, and these documents are incorporated herein by reference.In other embodiments of the present invention, evaporation (such as thermal evaporation or electron beam evaporation) is used to carry out the deposition of one or more thin metal layers.The material deposited by any physical vapor deposition technique can advantageously be selected from Ag, Cu, Al, Cr, Ti or silicon or metal alloy (such as NiCr alloy or NiCrW alloy).

[0121] In an embodiment of the present invention, the thickness of the metal coating is advantageously between 20 nm and 300 nm to achieve a desired level of opacity and a desired level of reflectivity for certain applications, in particular to achieve a metal-like appearance, advantageously between 30 nm and 150 nm, and more advantageously between 40 nm and 120 nm.

[0122] In a preferred embodiment of the invention, the metal coating comprises a reflective layer. The reflective layer is the topmost layer in the metal coating, i.e. the layer which is located furthest from the substrate surface. The reflective layer is therefore visible through any subsequent layers, in particular the protective top layer, and is largely responsible for the metallic appearance that the metal coating provides to the substrate. In an advantageous embodiment of the invention, the reflective layer is an aluminum layer. The thickness of the reflective layer may be between 10 nm and 25 nm, in particular the reflective layer may be the thickest layer in the metal coating.

[0123] In certain embodiments of the present invention, the target used for magnetron sputtering can be a circular target or a linear target, and the linear target is particularly useful in a continuous coating process. The target used can be a metal target (including, for example, a metal selected from Ag, Cu, Al, Cr, Ti or a silicon-based target), or a metal alloy target (including, for example, a NiCr alloy or a NiCrW alloy).

[0124] In an advantageous embodiment, in addition to the reflective layer, the metal coating also includes a metal base layer in direct contact with the polymer substrate. The metal base layer can improve the adhesion of the metal coating to the polymer substrate. The material of the metal base layer is different from the material of the reflective layer and can be selected from NiCr. The NiCr metal base layer can be composed of an alloy of Ni and Cr with a Ni / Cr weight ratio between 99 / 1 and 50 / 50, preferably 80 / 20. The metal base layer is advantageously in direct contact with the metal reflective layer. The inventors have found that this metal base layer further improves the mechanical and chemical resistance of the decorative coating.

[0125] In an alternative embodiment, the decorative coating includes a carbon adhesion layer located between the metal coating and the polymer substrate. The carbon adhesion layer can be in direct contact with the metal coating. The carbon adhesion layer can be in direct contact with the polymer substrate. The thickness of the carbon adhesion layer can be between 4nm and 10nm. Figure 3 A polymer substrate (10) is shown, wherein a carbon adhesion layer (3) is in direct contact with the substrate, a metal coating (2) is in direct contact with the adhesion layer, and a protective top layer (1) is in direct contact with the metal coating (2).

[0126] Deposition of a carbon adhesion layer on a polymer substrate using an alternative linear hollow cathode type plasma source may include:

[0127] a. providing an additional linear hollow cathode type plasma source comprising at least one pair of hollow cathode plasma generating electrodes connected to an AC, DC or pulsed DC generator for depositing the carbon adhesion layer on the polymer substrate;

[0128] b. injecting a plasma generating gas into the electrode of the additional plasma source at a flow rate of 1000 sccm to 5000 sccm, preferably 1500 sccm to 4500 sccm, more preferably 2000 sccm to 4000 sccm per linear meter of additional plasma source length, the plasma generating gas is preferably selected from N2, He, Ar or a mixture of two or more of these gases;

[0129] c. applying an electric power of 2kW to 20kW per meter of additional plasma source length to the additional plasma source;

[0130] d. injecting a gaseous precursor of carbon at a flow rate of 50 sccm to 600 sccm, preferably 100 sccm to 500 sccm, more preferably 200 sccm to 400 sccm per linear meter of additional plasma source length, the gaseous precursor of carbon being selected from, for example, CH4, C2H4, C2H2, C3H8, C4H 10 , preferably CH4, the gaseous precursor being preferably injected into the plasma at least between the electrodes of each electrode pair of the further plasma source;

[0131] e. exposing the substrate to plasma from another plasma source, thereby depositing a carbon adhesion layer including a carbon-based layer on the activated surface of the substrate.

[0132] The inventors have found that the carbon adhesion layer improves the chemical resistance of the decoration.

[0133] In certain embodiments, the additional plasma source is connected to a generator providing AC or pulsed DC current at a frequency between 5 kHz and 150 kHz, alternatively between 5 kHz and 100 kHz.

[0134] In certain embodiments of the present invention, the distance between the substrate surface and the outlet of the further plasma source is between 50 mm and 150 mm, advantageously between 60 mm and 120 mm, more advantageously between 80 mm and 100 mm.

[0135] In certain embodiments of the present invention, the carbon adhesion layer deposition is performed at a pressure between 0.005 Torr and 0.050 Torr, more advantageously between 0.010 Torr and 0.040 Torr, and even more advantageously between 0.020 Torr and 0.030 Torr.

[0136] In certain embodiments of the present invention, the hybridization ratio sp3 / sp2 of the carbon adhesion layer is between 0.6 and 0.8.

[0137] In an advantageous embodiment of the invention, a barrier layer, for example a barrier layer of silicon nitride, is deposited directly on the topmost metal layer to protect the metal layer from oxidation when the protective top layer is deposited. The barrier layer may be in direct contact with the protective top layer.

[0138] In certain embodiments of the present invention, magnetron sputtering deposition of the metal layer may be performed by applying a power of 1 kW to 20 kW per linear meter of target.

[0139] In certain embodiments of the invention, the plasma generating gas used for physical vapor deposition of the metal layer is advantageously argon.

[0140] In certain embodiments of the invention, physical vapor deposition is advantageously performed at a pressure between 0.002 Torr and 0.050 Torr, more advantageously between 0.003 Torr and 0.020 Torr, and even more advantageously between 0.004 Torr and 0.010 Torr.

[0141] In certain embodiments, deposition of the metal layer by evaporation is performed using an ingot of the same material as the target for magnetron sputtering mentioned above.

[0142] The metallic coating primarily provides a decorative metallic appearance to the resulting coated substrate. The metallic appearance can be enhanced by a protective top layer.

[0143] In certain embodiments of the present invention, the polymer substrate may be a uniform polymer sheet, although other shapes, such as three-dimensional shapes, are possible.

[0144] In certain embodiments of the present invention, the polymer substrate may include acrylic polymers, polymethyl methacrylate (PMMA) and copolymers thereof, CR-39 or allyl diglycol carbonate (ADC), polycarbonate, polypropylene (PP), biaxially oriented polypropylene (BOPP), polyethylene (PE), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polystyrene, cyclic olefin copolymer (COC) and polyethylene terephthalate glycol (PETG), and combinations thereof. The polymer substrate of the present invention may include a thermoplastic elastomer (TPE), sometimes referred to as a thermoplastic rubber, which is a class of copolymers or physical mixtures of polymers, typically plastics and rubbers, consisting of materials having both thermoplastic and elastomeric properties. In particular, the polymer substrate may include styrene block copolymers, TPS (TPE-s), thermoplastic polyolefin elastomers, TPO (TPE-o), thermoplastic vulcanizates, TPV (TPE-v or TPV), thermoplastic polyurethanes, TPU (TPU), thermoplastic copolyesters, TPC (TPE-E), thermoplastic polyamides, TPA (TPE-A).

[0145] In certain embodiments of the present invention, the polymer substrate may be a thin polymer film having a thickness between 5 μm and 300 μm, alternatively between 10 μm and 250 μm, alternatively between 20 μm and 200 μm, alternatively between 25 μm and 150 μm. These polymer films may be processed in a roll-to-roll manner.

[0146] For the following examples, polymer substrates of a mixture of polycarbonate (PC) and acrylonitrile butadiene styrene (ABS), and polymer substrates of ABS alone were used. Both substrates produced comparable results. These substrates had a matte appearance, and the gloss values ​​of these uncoated substrates were low. It was found that the deposition of SiO2 on these substrates increased their glossiness.

[0147] The following Examples 1 and 3 are comparative examples, whereas Examples 2 and 4 are examples according to the present invention.

[0148] For Example 1, a SiO2 layer was deposited from a silicon target by magnetron sputtering in an Ar / O2 atmosphere. The thickness of the SiO2 layer was 130 nm.

[0149] For Example 2, a boron-doped silicon oxide (SiO2:B) layer was deposited by hollow cathode PECVD using O2 reactant gas and a mixture of TTMSB and TEB as precursor gas. The thickness of the SiO2 layer was 130 nm.

[0150] For Example 3, a metal coating consisting of a first adhesion metal layer of a NiCr alloy of 4 nm was deposited on the polymer substrate, followed by a 17 nm thick reflective metal layer of aluminum. A Si3N4 barrier layer was deposited on the metal coating. Both metal layers were deposited by magnetron sputtering from the corresponding metal targets in an Ar atmosphere. A Si3N4 layer of 9 nm to 10 nm was deposited by magnetron sputtering from a Si target in an Ar / N2 atmosphere. Then a SiO2 layer identical to that of Example 1 was deposited.

[0151] For Example 4, a metal coating consisting of a first adhesion metal layer of a NiCr alloy of 4 nm was deposited on the polymer substrate, followed by a 17 nm thick reflective metal layer of aluminum. A Si3N4 barrier layer was deposited on the metal coating. Both metal layers were deposited by magnetron sputtering from the corresponding metal targets in an Ar atmosphere. A 9 nm to 10 nm Si3N4 layer was deposited by magnetron sputtering from a Si target in an Ar / N2 atmosphere. Then a SiO2:B layer identical to that of Example 2 was deposited.

[0152] For Example 5, a metal coating consisting of a first adhesion metal layer of a NiCr alloy of 4 nm was deposited on the polymer substrate, followed by a 17 nm thick aluminum reflective metal layer. A Si3N4 barrier layer was deposited on the metal coating. Both metal layers were deposited by magnetron sputtering from corresponding metal targets in an Ar atmosphere. A 9 nm to 10 nm Si3N4 layer was deposited by magnetron sputtering from a Si target in an Ar / N2 atmosphere. A polyurethane-based paint layer was then sprayed on the sputtered deposited layer.

[0153] For Example 6, a metal coating consisting of a 10 nm first adherent carbon layer was deposited on the polymer substrate by hollow cathode PECVD, followed by a 17 nm thick aluminum reflective metal layer. A Si3N4 barrier layer was deposited on the metal coating. The metal layer was deposited by magnetron sputtering from an aluminum metal target in an Ar atmosphere. A 9 nm to 10 nm Si3N4 layer was deposited from a Si target by magnetron sputtering in an Ar / N2 atmosphere. Then, a 130 nm thick undoped SiO2 layer was deposited by hollow cathode PECVD using O2 reaction gas and TMDSO (tetramethyldisiloxane).

[0154] The crockmeter test is a dry friction test carried out as described in standard ISO 11998:1998, using a cylindrical finger with a diameter of 15 mm and a 9 μm, 1200 grit sandpaper pad. For the present invention, 10 double strokes corresponding to 20 cycles are carried out on the dry sample without adding any liquid. The total weight on the abrasive pad is 900 g.

[0155] Gloss measurements were made according to ASTM standard D523-2014 at a specific angle of 60° using a certified black glass standard with a gloss of 96.0 at 60°.

[0156] After the rubbing test, the relative reduction in gloss expressed as a percentage of the initial gloss was determined.

[0157] For Example 1 and Example 5, the gloss was reduced by 30% to 40%. For Example 2 and Example 4, the gloss was reduced by 3% and 1% to 2%, respectively. For Example 6, the gloss was reduced by 3% to 4%.

[0158] Examples 2, 4 and 6 were subjected to a chemical durability test: the copper accelerated acetic acid salt spray test (CASS) according to standard ISO 9227-2006. In Example 6, delamination of the coating occurred already after 24 hours of testing, while for Examples 2 and 4, a reduction in gloss was observed after 48 hours, but the extent of the gloss reduction was less than 30%. Therefore, boron-doped SiO2 exhibits significantly better resistance to chemical attack.

Claims

1. A polymer substrate with a decorative coating, the decorative coating comprising a protective top layer of boron-doped silicon oxide, wherein: The boron-doped silicon oxide contains Si, O, B, H, and OH groups, wherein the boron content is between 4 atomic % and 12 atomic %.

2. The polymer substrate according to claim 1, wherein The protective top layer comprises at least 80 wt. % SiO2.

3. The polymer substrate according to any one of claims 1 and 2, wherein The O / Si atomic ratio of the protective top layer is between 1.9 and 2.

6.

4. A polymer substrate according to any one of the preceding claims, wherein The protective top layer is free of carbon.

5. A polymer substrate according to any one of the preceding claims, wherein The protective top layer has a thickness of at least 80 nm and / or at most 400 nm.

6. A polymer substrate according to any one of the preceding claims, wherein The protective top layer is in direct contact with the polymer substrate.

7. A polymer substrate according to any one of the preceding claims, wherein The decorative coating also includes a metallic coating including one or more metallic layers between the substrate and the protective top layer.

8. The polymer substrate according to claim 7, wherein The thickness of the metal coating is between 20 nm and 300 nm.

9. The polymer substrate according to any one of claims 7 to 8, wherein The metal coating comprises a reflective metal layer of a metal selected from Ag, Cu, Al, Cr, Zr, Ti, Si or NiCrW alloy, and optionally a metal base layer of NiCr in direct contact with the substrate and the reflective metal layer.

10. The polymer substrate according to any one of claims 7 to 9, wherein The decorative coating also includes a carbon adhesion layer between the substrate and the metal coating.

11. The polymer substrate according to any one of claims 7 to 10, wherein The decorative coating comprises a barrier layer of Si3N4 in direct contact with the metal coating and the protective top layer.

12. A method for depositing a decorative coating on a polymer substrate, the decorative coating comprising a protective top layer of boron-doped silicon oxide, wherein: The protective top layer comprises Si, O, B and OH groups, and wherein the boron content is between 4 atomic % and 12 atomic %, and the method comprises: a. providing a polymer substrate, b. providing a linear hollow cathode type plasma source, the length of the plasma source comprising at least one pair of hollow cathode plasma generating electrodes connected to an AC, DC or pulsed DC generator power supply for depositing the protective top layer on the substrate, c. injecting a plasma containing oxygen into the electrode of the plasma source to generate a reactive gas at a flow rate of 125 sccm to 750 sccm per meter of plasma source length, d. applying an electric power of 10 kW to 50 kW per meter of plasma source length to the plasma source to generate plasma, and e. injecting a precursor gas containing boron, silicon and hydrogen at a flow rate of 500 sccm to 2500 sccm per linear meter of plasma source length, wherein the precursor gas is injected into the plasma at least between the electrodes of each electrode pair of the plasma source, and depositing the protective top layer on the polymer substrate by exposing the substrate to the plasma of the plasma source.

13. The method according to claim 12, wherein: The precursor gas includes at least one precursor containing Si, at least one precursor containing B, and / or at least one precursor containing Si and B.

14. The method according to claim 12 or 13, wherein: The reaction gas is O2 or an O2-Ar mixture.

15. The method according to any one of claims 12 to 14, wherein: The flow rate of the reaction gas is 200 sccm to 500 sccm per linear meter of the plasma source length.

16. The method according to any one of claims 12 to 15, wherein: The precursor gas includes at least one precursor selected from a precursor containing silicon, a precursor containing boron, and / or a precursor containing silicon and boron, and wherein a total flow rate of each precursor is between 10 sccm and 500 sccm.

Images