[0001] The present invention relates to a coated substrate provided with a functional coating and a magnetron sputtered topcoat of a mixed metal oxide comprising at least TiO _y and ZrO _z , and optionally SiO _x , for a method to provide for said coated substrate and to the use of a topcoat.

[0002] Functional coatings such as those comprising magnetron sputtered dielectric layers are typically known to be sensitive to chemical and mechanical damages during their production, transport, processing, storage and/or handling. This limited mechanical, chemical and corrosion resistance usually limits their possible uses in contact with the external environment.

[0003] Various attempts were made at providing glazings with coatings having high chemical durability or mechanical durability, or both chemical and mechanical durability.

[0004] WO2009115596A1 relates to an essentially transparent glazing including an assembly of thin layers deposited in a vacuum with a magnetron, and having sun-proof and/or low-emission properties, wherein the surface protection layer comprises a layer containing titanium oxide and at least one other high-hardness metal oxide selected from the group including ZrC>2, SiC>2, C^Ch. The glazing of the disclosure is capable of withstanding a thermal treatment at 550°C for 5 minutes without generating optical defects such as discolouring or iridescence. In the mixed oxide, the titanium oxide is present at least 40% by weight. The surface layer contains zirconium oxide in a proportion of 15 to 50% by weight.

[0005] W02010031808A1 relates to a glazing that comprises at least one layer deposited by cathodic spraying under vacuum, said layer containing one or more oxides and a proportion in weight of titanium oxide of at least 40% and not exceeding 95%. The thickness of the layer in question and optionally the thickness of the other layers containing metal oxide is/are selected so that on a clear “float” glass sheet having a thickness of 4 mm, said layer(s) would yield a reflection of at least 15% and a light transmission of at least 60%. The layer or layer system in question further has a mechanical and/or chemical resistance comparable to that of layers produced by pyrolysis for obtaining products having the same kind of optical properties. An amount of at least 40 %weight of titanium oxide typically amounts to at least 50 %atomic of titanium in the deposited layer.

[0006] The above solutions however fail to provide for satisfactory mechanical durability against abrasion, encountered during transport and storage conditions, beyond typical dry brush test and/or Automatic Wet Rub Test (AWRT).

[0007] WO2018202595A1 relates to a coated substrate comprising: a substrate; a soft coating provided on at least a part of at least one face of the substrate; a protective sol-gel coating provided on at least a part of said face above the soft coating, to a process for making such coated substrate and to glazing units comprising such coated substrate. The sol-gel coating comprises a mixture of titanium oxide, silicon oxide and optionally bismuth oxide and/or cerium oxide in theoretical weight ratios of titanium oxide TiC>2 /silicon oxide SiC>2 ranging from 0.10 to 3. When zirconium oxide is present, the ratio zirconium oxide/silicon oxide ranges from 0.10 to 3. The ratio titanium oxide/zirconium oxide ranges from 0.10 to 10. The thickness of the sol-gel coating typically ranges from 50 to 500 nm. This solution has the main drawbacks of providing for a significantly thick layer of the protective layer and requires an additional mandatory step of heating for curing the sol-gel coating, together with additional production constraints, as a change of production line is required. That is, intermediate steps which may impart damages, are required before any protection is provided to the coated substrate by the sol-gel coating.

[0008] Pending application PCT/EP2021/058666 relates to a coated substrate comprising a transparent substrate having two major opposing first and second surfaces, wherein at least one surface is provided with a functional coating, characterized in that the transparent substrate is provided, above and in contact with the functional coating, with a magnetron sputtered topcoat of a mixed metal oxide comprising at least SiOx, TiOy, and ZrOz wherein x, y, z range from 1.8 to 2.2, wherein the topcoat comprises from 10 to 65 at% silicon, from 8 to 38 at% titanium, from 25 to 80 at% zirconium, for a total of 100 at% of the metals, and wherein the topcoat has a thickness from 0.1 to 10 nm, to methods to provide for said coated substrates and to uses thereof.

[0009] There remains a need to develop coated substrates, particularly glass substrates provided with a functional coating having improved mechanical, chemical and corrosion resistance while not significantly impacting the emissivity and/or the aesthetics of the coating.

[0010] There remains a need to develop coated substrates, particularly glass substrates provided with a functional coating having improved mechanical, chemical and corrosion resistance while not significantly impacting the emissivity, nor the aesthetics of the coating, that is, preserving the optical properties of said functional coating.

[0011] The present invention aims at providing for a coated substrate comprising a transparent substrate having two major opposing first and second surfaces, wherein the first surface is provided with a functional coating, characterized in that the transparent substrate is provided, above and in contact with the functional coating, with a magnetron sputtered topcoat of a mixed metal oxide comprising at least TiO _y and ZrO _z , and optionally SiO _x , wherein x, y, z range from 1.8 to 2.2, wherein the topcoat comprises

- from 8 to 49 at% titanium,

- from 51 to 92 at% zirconium,

- from 0 to 9 at% silicon, for a total of 100 at% of the metals, and wherein the topcoat has a thickness from 0.1 to 10 nm.

[0012] A method to provide for said coated substrate is also provided.

[0013] Heat treated coated substrates and multiple glazing units are provided.

[0014] The present topcoat is a magnetron sputtered mixed metal oxide comprising at least TiO _y , and ZrOz , and optionally SiO _x , wherein x, y, z range from 1.8 to 2.2, wherein the topcoat comprises

- from 8 to 49 at% titanium (Ti),

- from 51 to 92 at% zirconium (Zr),

- from 0 to 9 at% silicon (Si), for a total of 100 at% of the metals including impurities, and wherein the topcoat has a thickness from 0.1 to 10 nm.

[0015] Impurities are considered as the additional metals that may be practically indissociable from the preceding metals. This is particularly the case for yttrium and/or hafnium (both transition metals). When these additional metals are present, their content remains relatively limited and does not exceed 1 at% of the mixed metals as claimed, and usually remains below 0.8 at%. They are not considered in the calculation of the topcoat active metal content of Ti, Zr and Si. Said active content is considered as the sum of only the contributions of titanium, zirconium and optional silicon, as providing for the mechanical durability in the scope of the present invention. Aluminium may be present in titanium based or silicon based targets, preferably as a minor element in amounts < 5.0 at%, alternatively < 2.0 at%, alternatively < 1.0 at%. Again, such aluminium is herein considered as an impurity and not taken into account for the active content of titanium, zirconium and optional silicon.

[0016] Alternatively, the present topcoat may be a magnetron sputtered mixed metal oxide comprising at least TiO _y , and ZrO _z , and optionally SiO _x , wherein x, y, z range from 1.8 to 2.2, wherein the topcoat comprises

- from 8 to 49 at% titanium (Ti),

- from 51 to 92 at% zirconium (Zr),

- from 0 to 9 at% silicon (Si),

- from 0 to 5 at% impurities, for a total of 100 at% of the metals including impurities, and wherein the topcoat has a thickness from 0.1 to 10 nm.

[0017] In the scope of the present invention, the Si element will be assimilated to a metal due its characteristics in the present topcoat, although it is chemically a metalloid material.

[0018] In some embodiments of the invention, the above ranges for the Ti, Zr and Si, in the topcoat may independently vary for one from the other. The amount of Ti may alternatively range from 10 to 47 at%, alternatively from 12 to 46 at%. The amount of Zr may alternatively range from 53 to 90 at%. The amount of Si may alternatively range from 1 to 8 at%, alternatively from 2 to 7 at%. The amount of impurities may alternatively range from 0.1 to 3 at%, alternatively from 0.2 to 2 at%. These amounts may thus vary independently for each metal, provided the total is 100 at% of the metals, including impurities.

[0019] The amounts of each metal may be determined by methods available to the skilled person, such as X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF), and others. These analysis may be carried out on the magnetron sputtering deposited topcoat using the usual procedures known in the art.

[0020] The amounts are provided for an optimal topcoat, surprisingly providing for a superior mechanical durability against abrasion, for functional coatings having to be transported or stored, that is, when the amount of oxide of titanium is < 40%, when combined with zirconium, optionally in presence of silicon. Contrary to the teaching of W02009115596A1 , it was unexpectedly found that an amount of oxide of titanium > 40% is not providing the necessary durability when the titanium is combined with zirconium.

[0021] The present topcoat may have a thickness ranging from 0.1 to 10.0 nm, alternatively from 0.5 to 5.0 nm, alternatively from 2.0 to 5.0 nm.

[0022] Such a thickness allows for an improved mechanical durability while minimizing the optical contribution to the functional coating underneath. The topcoat is permanent, in that it is not removed or modified upon optional heat treatment of the coated substrate. There is also no detrimental impact on the optical properties of the underlying functional coating.

[0023] The refractive index n of the present topcoat material in the ranges as claimed may range of from 1.8 to 2.3, at a wavelength of 550 nm, depending on its final composition. The silicon may serve to finetune the refractive index of the topcoat material while not impairing the initial protective function of the topcoat.

[0024] The transparent substrate may be a glass substrate, or a plastic substrates, such as poly(methyl meth)acrylate (PMMA), polycarbonates, polyethyleneterephthalate (PET), polyolefins, polyvinyl chloride (PVC), or mixtures thereof. Transparency of a substrate is considered when T is superior to 10%, alternatively superior to 20%, alternatively superior to 30%.

[0025] In most preferred instances, the transparent substrate is a glass substrate.

[0026] The glass may be of any type, such as conventional float glass or flat glass, and may be of any composition having any optical properties, e.g., any value of visible transmission above 10%, ultraviolet transmission, infrared transmission, and/or total solar energy transmission.

[0027] The glass substrate may be a soda-lime, a borosilicate, a leaded glass, or an aluminosilicate glass. The substrate may be regular clear, colored or extra-clear (i.e. lower Fe content and higher transmittance) glass substrate. Further examples of glass substrates include clear, green, bronze, or blue-green glass substrates.

[0028] The glass may be annealed, tempered or heat strengthened glass.

[0029] The transparent glass substrate may have a thickness ranging from 0.5 mm to about 15 mm, alternatively from 1 mm to about 10 mm, alternatively from 1 mm to about 8 mm.

[0030] The transparent glass substrate may also be considered suitable for the present invention, when having a thickness ranging from 0.5 to 2 mm.

[0031] The transparent substrate typically has two major opposing first and second surfaces, where at least a part of the first surface is provided with the functional coating. [0032] The present topcoat is deposited over, and in contact with, at least a part of the functional coating provided on a least one surface of the transparent substrate, to protect said functional coating from mechanical and/or chemical damage during shipment, storage, handling, processing and/or in final use.

[0033] The second surface of the transparent substrate may be coated with the same ora different functional coating. In such instances, the protective topcoat of the present invention may also be provided on the functional coating provided on the second surface.

[0034] In the scope of the present invention, the term "functional coating" refers to a coating which modifies one or more physical properties of the substrate, e.g., optical, thermal, chemical or mechanical properties. Such a functional coating is not intended to be removed from the substrate during subsequent processing. The functional coating is typically a permanent or "non-removable" coating.

[0035] The functional coating on the first and optionally on the second surface, may independently be a solar control coating, a conductive coating, an antireflective coating, a decorative coating and/or a low emissivity coating.

[0036] The functional coating may be a single layer or a stack of thin layers, that is, a multiple layer functional coating, and may include one or more metals, non-metals, semi-metals, dielectrics, semiconductors, or alloys, compounds, composites, combinations, or blends thereof. [0037] When discussing a stack of thin layers in the present invention, it is typically understood that a first layer be the first applied on the substrate, a second being the second layer applied on the substrate, above the first layer. The successive order of the positions is considered relative to the substrate onwards, up to the uppermost layer.

[0038] In the scope of the present invention, the terms “below”, “underneath”, “under” indicate the relative position of a layer vis a vis a next layer, within the layer sequence starting from the substrate. In the scope of the present invention, the terms “above”, “upper” indicate the relative position of a layer vis a vis a next layer, within the layer sequence starting from the substrate.

[0039] In the scope of the present invention, the relative positions of the layers within the stack do not necessarily imply direct contact between the layers. That is, some intermediate layer may be provided between the first and second layer. For example, a first layer "deposited over" the substrate does not preclude the presence of one or more other coating layers of the same or different composition located between that first layer film and the substrate, provided the objective of the present invention is not jeopardized.

[0040] In some instances, a layer may actually be composed of several multiple individual layers. [0041] The present topcoat is understood to be in an upper position relative to the functional coating provided on the first surface of the transparent substrate. That is, the present topcoat is situated the furthest away from the transparent substrate relative to the first deposition surface of the substrate, typically in contact with air. [0042] The present topcoat is the uppermost layer above the functional coating, non-permanent layers excluded, in direct contact with the last layer of said functional coating. In most instances, the last layer of the functional coating does not provide for mechanical and/or chemical durability. In such instances, the present topcoat provides for mechanical and chemical durability of the functional coating.

[0043] The present topcoat is not intended to be removed, and is thus not considered a removable or non-permanent protective layer.

[0044] In some instances, the functional coating may itself comprise an uppermost layer providing for some mechanical and/or chemical durability. In such instances, the present topcoat provides for even superior mechanical and chemical durability of the functional coating, particularly in view of abrasion.

[0045] The functional coating may have a thickness ranging from 10 to 1000 nm.

[0046] Unless stated otherwise, all layer thicknesses herein are geometrical layer thicknesses.

[0047] In certain embodiments of the invention, the functional coating may be a solar control coating, where the solar control coating includes visible, infrared and/or ultraviolet energy reflecting or absorbing coatings.

[0048] In certain embodiments of the invention, the functional coating may be an electrically conductive coating such as an electrically conductive heated window coating or a single-film or multi-film coating capable of functioning as an antenna.

[0049] A functional coating may be a low emissivity coating typically allowing visible wavelength energy, e.g., about 400 nm to about 780 nm, to be transmitted through the coating but reflecting shorter-wavelength solar infrared energy and/or thermal infrared energy, typically intended to improve the thermal insulating properties of architectural glazings. By "low emissivity" is meant emissivity less than about 0.3, alternatively less than about 0.2.

[0050] The functional coating may be a single layer metal oxide coating, a multiple layer metal oxide coating, a non-metal oxide coating, or a multiple layer functional coating.

[0051] In certain embodiments of the invention, single layer metal oxide coatings include those coatings comprising a zinc oxide doped with aluminium, gallium or hafnium; a mixed oxide of zinc and tin; tin oxide possibly doped with fluor or antimony; indium oxide possibly doped with tin; or the like.

[0052] In certain embodiments of the invention, multiple layer metal oxide coatings include those coatings comprising at least one layer of high refractive index material, and at least one layer of low refractive index material, that is, those coatings having layers of materials having alternating refractive indices. Such coatings are typically represented with a coating comprising a first layer of material having a low or high refractive index, a second layer of material having a high or low refractive index, a third layer of material having a low or high refractive index, a fourth layer of material having a high or low refractive index, and optional protective layer. A low refractive index is typically a refractive index < 1.7, or typically < 1.6, while a high refractive index is typically a refractive index > 1.8, or typically > 1.9 or > 2.0. Some layers may have intermediate refractive indices comprised of from 1 .7 to 1.8. Refractive indices are typically considered at a wavelength of 550 nm.

[0053] In certain embodiments of the invention, the functional coating may also be a multiple layer functional coating comprising an alternating arrangement of n infrared reflective (IR) layers and n + 1 dielectric layers, with n > 1 , such that each IR layer is surrounded by two dielectric layers.

[0054] The IR layers may be made of silver, gold, palladium, platinum or alloys thereof. The IR layers may have a thickness from 2 to 30 nm, alternatively from 5 to 20 nm, alternatively from 7 to 18 nm. These thickness ranges may enable the desired low emissivity and/or solar control function and/or conductivity to be achieved while retaining a good light transmission.

[0055] The dielectric layers may typically comprise oxides, nitrides, oxynitrides or oxycarbides of Zn, Sn, Ti, Zr, Si, In, Al, Bi, Ta, Hf, Mg, Nb, Y, Ga, Sb, Mg, Cu, Ni, Cr, Fe, B or mixtures thereof. [0056] In certain embodiments of the present invention, the dielectric layers may comprise oxides, nitrides, oxynitrides or oxycarbides of Zn, Sn, Ti, Zr, Si, In, Al, Nb, Sb, Ni, Cr, or mixtures thereof. Alternatively, the dielectric layers may comprise oxides, nitrides, oxynitrides of Zn, Sn, Ti, Zr, Si, In, Al, Nb, Sb, Ni, Cr, or mixtures thereof.

[0057] These materials may be eventually doped, where examples of dopants include aluminium, zirconium, or mixtures thereof. The dopant or mixture of dopants may be present in an amount up to 15 wt %.

[0058] Typical examples of dielectric materials include, but are not limited to, silicon based oxides, silicon based nitrides, zinc oxides, tin oxides, mixed zinc-tin oxides, silicon nitrides, silicon oxynitrides, titanium oxides, aluminum oxides, zirconium oxides, niobium oxides, aluminum nitrides, bismuth oxides, mixed silicon-zirconium nitrides, and mixtures of at least two thereof, such as for example titanium-zirconium oxide.

[0059] The dielectric layer may consist of a plurality of individual layers comprising or essentially consisting of the above materials.

[0060] The dielectric layers may each have a thickness ranging from 0.1 to 200 nm, alternatively from 0.1 to 150 nm, alternatively from 1 to 120 nm, alternatively from 1 to 80 nm. Different dielectric layers may have different thicknesses. That is, the first dielectric layer may have a thickness that is the same or different, greater or smaller, compared to the thickness of the second or third or any other dielectric layer.

[0061] When there are two IR layers (when n = 2), the second dielectric layer may be referred to as the “internal dielectric layer”, as it is sandwiched between two IR layers.

[0062] When there are three IR layers (when n = 3), the second and third dielectric layers may be referred to as “internal dielectric layers”, as they are respectively sandwiched between two IR layers.

[0063] The multiple layer functional coating may comprise a seed layer underneath at least one IR layer, and/or the coating may comprise a barrier layer on at least one IR layer. A seed layer is typically provided to assist in forming a good quality film of the IR material, that is, providing for a homogeneous and stable layer of IR material. A barrier layer is typically provided to assist in protecting the IR material from degradation induced by the formation of any layer above it, for example to protect it from oxygen or oxygenated species which may deteriorate the quality of the IR layer and also from deterioration due to heat treatments.

[0064] A given IR layer may be provided with either a seed layer, or a barrier layer or both. A first IR layer may be provided with either one or both of seed and barrier layers, and a second IR layer may be provided with either one or both of seed and barrier layers and further so. These constructions are not mutually exclusive. The seed and/or barrier layers may have a thickness from 0.1 to 35 nm, alternatively 0.5 to 25 nm, alternatively 0.5 to 15 nm, alternatively 0.5 to 10 nm.

[0065] The multiple layer functional coating may also comprise a thin layer of sacrificial material having a thickness < 15 nm, alternatively < 9 nm, provided above and in contact with at least one IR layer. Examples of sacrificial material include titanium, zinc, nickel, chrome, oxides of Ni, oxides of Ni alloys, oxides of Cr, oxides of Cr alloys, NiCrO _x , NiCrO _x N _y , zinc oxide, tin oxide, or other suitable material or mixture thereof.

[0066] A dielectric layer may be provided with an absorbing layer adjusted in order to selectively alter transmission of the coated article. In certain examples, the thickness of said absorbing layer can be adjusted to significantly adjust the transmission of the coated article without adversely affecting coloration thereof. Examples of absorbing layer include Ni, Cr, NiCr, NiCrN _x , NiCrW, CrN, ZrN, TiN, Ti, Zr, NiO _x , or the like. Such an absorption layer may located such that at least one of the IR layer is located over the absorption layer, optionally, such an absorbing layer may be sandwiched between and contacting a first and a second layer comprising silicon nitride. The absorbing layer may have a thickness ranging from 0.5 to 10 nm.

[0067] The multiple layer functional coating may optionally already comprise a uppermost layer including oxides of Ti, Zr, or mixed oxide of Ti and Zr with 45-65 %wt Ti; or oxides of Si, Al; or oxide of Zr and Al; or nitrides of Si, Al. Such uppermost layer may be replaced or topped by the present topcoat.

[0068] A first example of multiple functional layer coating serving as a low emissivity coating comprises at least one silver layer, and a sequence : substrate/MeO/ZnO:AISi/Ag/AISi-MeO where MeO is a metallic oxide such as SnC>2, TiC>2, I^Ch, Bi2Oa, ZrC>2, Ta2Os, SiC>2 or AI2O3 or a mixture thereof.

[0069] An second example of multiple layer functional coating serving as low emissivity coating, includes a first dielectric layer including silicon nitride; first Ni or NiCr inclusive layer; an infrared (IR) reflecting layer comprising silver; a second Ni or NiCr inclusive layer; and a second dielectric layer including silicon nitride. Such a multiple layer functional coating may optionally comprise a topcoat of a mixed (oxi)nitride of SiZr, or mixed oxide of TiZr.

[0070] A third example of multiple layer functional coating comprises * an infrared (IR) reflecting layer contacting and sandwiched between first and second layers, said second layer comprising NiCrOx; and

* wherein at least said second layer comprising NiCrOx is oxidation graded so that a first portion of said second layer close to said infrared (IR) reflecting layer is less oxidized than a second portion of said second layer that is further from said infrared (IR) reflecting layer.

[0071] A fourth example of multiple layer functional coating comprises: a dielectric layer; a first layer comprising zinc oxide located over the dielectric layer; an infrared (IR) reflecting layer comprising silver located over and contacting the first layer comprising zinc oxide; a layer comprising an oxide of NiCr located over and contacting the IR reflecting layer; a second layer comprising zinc oxide located over and contacting the layer comprising the oxide of NiCr; and another dielectric layer located over the second layer comprising zinc oxide.

[0072] A fifth example of multiple layer functional coatings comprises: a first dielectric layer; a first infrared (IR) reflecting layer comprising silver located over at least the first dielectric layer; a first layer comprising zinc oxide located over at least the first IR reflecting layer and the first dielectric layer; a second IR reflecting layer comprising silver located over and contacting the first layer comprising zinc oxide; a layer comprising an oxide of NiCr located over and contacting the second IR reflecting layer; a second layer comprising zinc oxide located over and contacting the layer comprising the oxide of NiCr; and another dielectric layer located over at least the second layer; comprising zinc oxide.

[0073] A sixth example of multiple layer functional coating comprises: a first dielectric layer; a first layer comprising zinc oxide located over the dielectric layer; an infrared (IR) reflecting layer comprising silver located over and contacting the first layer comprising zinc oxide; a second layer comprising zinc oxide located over the IR layer; and a second dielectric layer located over the second layer comprising zinc oxide. The first and second dielectric layers may comprise several layers, among which layers of varying composition in zinc oxide, that is, layers of zinc oxide, zinc oxide doped with aluminium, or layers of mixed oxide of zinc and tin, having a ratio Sn/Zn ranging from 0.5 to 2 by weight, or having a ratio Sn/Zn ranging from 0.02 to 0.5 by weight; layers of silicon nitride; layers of titanium oxide; among others. The first and second layers comprising zinc oxide may also have varying composition in zinc oxide, that is, layers of zinc oxide; zinc oxide doped with aluminium; mixed oxide of zinc and tin; mixed oxide of zinc, titanium and aluminium; among others.

[0074] A seventh example of multiple layer functional coating comprises, in sequence: a first dielectric layer; a first IR layer comprising silver; a second dielectric layer; a second IR layer; a third dielectric layer. The first, second and third dielectric layers may comprise several layers, among which layers of varying composition in zinc oxide, that is, layers of zinc oxide, zinc oxide doped with aluminium, or layers of mixed oxide of zinc and tin, having a ratio Sn/Zn ranging from 0.5 to 2 by weight, or having a ratio Sn/Zn ranging from 0.02 to 0.5 by weight; layers of mixed oxide of zinc, titanium and aluminium; layers of silicon nitride; layers of titanium oxide; among others. In some instances, the IR layers may be independently provided with a metallic barrier layer such as Ti, Ni, NiCr, or the like.

[0075] An eight example of multiple layer functional coating comprises, in sequence: a first dielectric layer; a first IR layer comprising silver; a second dielectric layer; a second IR layer; a third dielectric layer; a third IR layer; a fourth dielectric layer. The first, second, third and fourth dielectric layers may comprise several layers, among which layers of varying composition in zinc oxide, that is, layers of zinc oxide, zinc oxide doped with aluminium, or layers of mixed oxide of zinc and tin, having a ratio Sn/Zn ranging from 0.5 to 2 by weight, or having a ratio Sn/Zn ranging from 0.02 to 0.5 by weight; layers of mixed oxide of zinc, titanium and aluminium; layers of silicon nitride; layers of titanium oxide; among others. In some instances, the IR layers may be independently provided with a metallic barrier layer such as Ti, Ni, NiCr, or the like.

[0076] A wide variety of multiple layer functional coatings may be provided with the present coated substrate, benefitting from the topcoat providing for protection against mechanical damages. At the same time, optical properties, such as light transmission, light reflection and colors, remain within an acceptable variation as compared to the coating without the topcoat, that is, Delta TTC < 2%, Delta RTC < 2%, and Delta E*TC < 5, where “TC” relates to the effect the topcoat may have on the selected optical parameter (T, R or Delta E*) for said functional coating.

[0077] A method to prepare a coated substrate comprises, in sequence, at least the steps of:

1 . Providing for a transparent substrate having two major opposing first and second surfaces

2. Depositing a functional coating on at least a part of the first surface of the transparent substrate,

3. Depositing, above and in contact with the functional coating, a topcoat comprising a mixed metal oxide comprising at least TiO _y and ZrO _z , and optionally SiO _x , wherein x, y, z range from 1.8 to 2.2, by a magnetron sputtering technique, wherein the topcoat comprises

- from 8 to 49 at% titanium,

- from 51 to 92 at% zirconium,

- from 0 to 9 at% silicon, for a total of 100 at% of the metals, and wherein the topcoat has a thickness from 0.1 to 10 nm.

[0078] The deposition step of the topcoat using magnetron sputtering allows for the process to be integrated easily into an existing production line providing for the functional coating already on the transparent substrate. The magnetron deposition also allows for the deposition of a topcoat layer having a thickness from 0.1 to 10 nm. Such a thin layer is found effective in providing for the necessary mechanical durability, without negatively impacting the chemical durability and optical properties of the functional coating. [0079] The functional coating may typically be deposited over the substrate by chemical vapor deposition (CVD), atmospheric pressure CVD (APCVD), low-pressure CVD (LPCVD) , plasma- enhanced chemical vapor deposition (PECVD), LPCVD (low pressure chemical vapor deposition), physical vapor deposition, magnetron sputtering, ion assisted deposition.

[0080] Individual layers of the same functional coating may be provided by different deposition methods. Typically, they may however be deposited using the same technique.

[0081] In some instances, at least one layer of the functional coating may be deposited by magnetron sputtering. In some instances, all the layers of the functional coating are deposited by magnetron sputtering.

[0082] The protective topcoat of the present invention is deposited using magnetron sputtering. The efficiency of the topcoat to provide for the mechanical and chemical durability is optimal if it is deposited by magnetron sputtering, compared to a CVD or solgel method. The layer deposited by magnetron sputtering is effective without any prior heating or additional process step, at a thickness ranging of from 0.1 to 10 nm, alternatively from 0.5 to 5.0 nm, alternatively from 2.0 to 5.0 nm. The layer so deposited also does not significantly impact the optical properties of the functional coating, with Delta TTC < 2%, Delta RTC < 2%, and Delta E*TC < 5, where “TC” relates to the effect the topcoat may have on the selected optical parameter (T, R or Delta E*) for said functional coating.

[0083] The deposition of the topcoat using magnetron sputtering may be effected using either metallic or ceramic targets to provide for the at least three titanium, zirconium or silicon elements. [0084] The at least there elements may be independently provided from either one or more of a ceramic or a metallic target. Various combinations and co-sputtering alternatives may exist, provided the magnetron sputtered topcoat deposited on the functional coating comprises a mixed metal oxide comprising at least TiO _y and ZrO _z , and optionally SiO _x , wherein x, y, z range from 1.8 to 2.2, and wherein the topcoat comprises

- from 8 to 49 at% titanium,

- from 51 to 92 at% zirconium,

- from 0 to 9 at% silicon, for a total of 100 at% of the metals, and wherein the topcoat has a thickness from 0.1 to 10 nm. [0085] As discussed above, impurities may be present in the topcoat, as a consequence of their presence in the selected target. The composition of the topcoat amounts for a total of 100 at%, including impurities. The active content of the topcoat is however only taking into account the amounts of titanium, zirconium and optional silicon.

[0086] A metallic target may comprise at least one of titanium, zirconium or silicon. A metallic target may comprise two or more of titanium, zirconium or silicon.

[0087] A ceramic target may comprise at least one oxide of titanium, zirconium or silicon. A ceramic target may comprise two or more oxides of titanium, zirconium or silicon. [0088] A ceramic target may comprise two element selected from titanium, zirconium or silicon, and a metallic target may comprise the third element.

[0089] In some instances, one element of the sputtered topcoat may be provided from both a ceramic target and a metallic target at the same time.

[0090] A ceramic target may comprise at least one oxide of a metal, and a metallic form of at least one other metal.

[0091] A ceramic target may comprise at least one oxide of titanium or zirconium, and a metallic form of silicon.

[0092] In those instances, the three elements may be provided from multiple independent targets, used in conjunction, also called co-sputtering, where the targets may each be a ceramic or a metallic target.

[0093] The sputtering or deposition from more than one target has the advantage of providing for a variety of topcoats comprising at least silicon, titanium and zirconium, tunable for the desired mechanical durability. This also has the advantage of allowing the modulation of the deposition rates and/or allowing easy replacement of one target or another depending on the material consumption during processing. This also has the advantage of modulating the stoichiometry of the topcoat as a function of the gas used during sputtering.

[0094] In other instances, the three elements Ti, Si, and Zr may be provided from one single target. [0095] A ceramic target may comprise at least the oxides of the three elements Ti, Si, and Zr, or a metallic target may comprise at least the three elements in metallic form.

[0096] A ceramic target may comprise the oxides of titanium and zirconium, and a metallic form of silicon.

[0097] The sputtering or deposition from one single target comprising at least silicon, titanium and zirconium, has the advantage of providing for a reproducible and homogeneous topcoat.

[0098] The topcoat is typically sputtered in a gas flow containing argon or oxygen or both. Various mixtures may be provided for each gas, to provide for the required stoichiometry of the topcoat.

[0099] A further advantage of the present topcoat is that it may be subjected to a heat treatment, and as such, provide for protection of the functional coating through such heat treatment.

[0100] The heat treatment step is only optional, and will be considered as requires the end use of the coated substrate, since the topcoat itself will provide protection even though it is not heat treated.

[0101] A method to prepare a heat treated coated substrate comprises, in sequence, at least the steps of:

1. Providing for a transparent substrate having two major opposing first and second surfaces,

2. Depositing a functional coating on at least a part of the first surface of the transparent substrate, 3. Depositing, above and in contact with the functional coating, a topcoat comprising a mixed metal oxide comprising at least TiO _y and ZrO _z , and optionally SiO _x , wherein x, y, z range from 1 .8 to 2.2, by a magnetron sputtering technique, wherein the topcoat comprises

- from 8 to 49 at% titanium,

- from 51 to 92 at% zirconium,

- from 0 to 9 at% silicon, for a total of 100 at% of the metals, and wherein the topcoat has a thickness from 0.1 to 10 nm,

4. Submitting the coated substrate to a heat treatment.

[0102] In some embodiments of the present method, compatible with other embodiments of the present invention, the above ranges for the Ti , , Zr and Si in the topcoat may independently vary for one from the other. The amount of Ti may alternatively range from 10 to 47 at%, alternatively from 12 to 46 at%. The amount of Zr may alternatively range from 53 to 90 at%. The amount of Si may alternatively range from 1 to 8 at%, alternatively from 2 to 7 at%. These amounts may thus vary independently for each metal, provided the total is 100 at% of the metal, including impurities.

[0103] In the scope of the present invention, when steps are in sequence, it is intended to mean that they are effected in the order listed. There may however be additional intermediate steps added within the sequence. Such additional intermediate steps may be of washing, transporting displacing, measuring, cutting, or the like.

[0104] The heat treatment may be one of those encountered in a bending (also known as curving), annealing (also known as strengthening) or tempering process.

[0105] A suitable thermal treatment comprises heating the coated glass sheet to a temperature of at least 560°C in air, for example between 560°C and 700°C, in particular around 640°C to 670°C, during around 3, 4, 6, 8, 10, 12 or even 15 minutes according to the heat-treatment type and the thickness of the glass sheet. The treatment may comprise a rapid cooling step after the heating step, to introduce a stress difference between the surfaces and the core of the glass so that in case of impact, the so-called tempered glass sheet will break safely in small pieces. If the cooling step is less strong, the glass will then simply be heat-strengthened and in any case offer a better mechanical resistance.

[0106] Further heat treatment may be implied in process steps like 1) bending, 2) tempering, 3) sintering of colored ceramic print or silver bus bar print, 4) vacuum sealing of vacuum double glazing and 5) calcination of a wet-coated low reflective coating or antiglare coating.

[0107] A first method to prepare a double side coated substrate comprises, in sequence, at least the steps of: 1. Providing for a transparent substrate having two major opposing first and second surfaces, wherein the first surface is exposed,

2. Depositing a first functional coating on at least a part of the first surface of the transparent substrate,

3. Depositing, above and in contact with the first functional coating, a first topcoat comprising a mixed metal oxide comprising at least TiO _y and ZrO _z , and optionally SiO _x , wherein x, y, z range from 1 .8 to 2.2, by a magnetron sputtering technique, wherein the first topcoat comprises

- from 8 to 49 at% titanium,

- from 51 to 92 at% zirconium,

- from 0 to 9 at% silicon, for a total of 100 at% of the metals, and wherein the first topcoat has a thickness from 0.1 to 10 nm,

4. Optionally flipping the substrate such as to expose the second surface,

5. Depositing a second functional coating on at least a part of the second surface of the transparent substrate, to provide for a double side coated transparent substrate,

6. Optionally depositing a second topcoat,

7. Optionally submitting the double side coated transparent substrate to a heat treatment.

[0108] A second method to prepare a double side coated substrate comprises, in sequence, at least the steps of:

1. Providing for a transparent substrate having two major opposing first and second surfaces, wherein the first surface is exposed,

2. Depositing a first functional coating on at least a part of the first surface of the transparent substrate,

3. Depositing, above and in contact with the first functional coating, a first topcoat comprising a mixed metal oxide comprising at least TiO _y and ZrO _z , and optionally SiO _x , wherein x, y, z range from 1 .8 to 2.2, by a magnetron sputtering technique, wherein the first topcoat comprises

- from 8 to 49 at% titanium,

- from 51 to 92 at% zirconium,

- from 0 to 9 at% silicon, for a total of 100 at% of the metals, and wherein the topcoat has a thickness from 0.1 to 10 nm,

4. Optionally flipping the substrate such as to expose the second surface, 5. Depositing a second functional coating on at least a part of the second surface of the transparent substrate, to provide for a double side coated transparent substrate,

6. Optionally depositing, above and in contact with the second functional coating, a second topcoat comprising a mixed metal oxide comprising at least TiO _y and ZrO _z , and optionally SiO _x , wherein x, y, z range from 1.8 to 2.2, by a magnetron sputtering technique, wherein the second topcoat comprises

- from 8 to 49 at% titanium,

- from 51 to 92 at% zirconium,

- from 0 to 9 at% silicon, for a total of 100 at% of the metals, and wherein the topcoat has a thickness from 0.1 to 10 nm,

7. Optionally submitting the double side coated transparent substrate to a heat treatment.

[0109] Such first and second methods may thus provide for a transparent substrate provided with a first functional coating on at least a part of a first surface, and a second functional coating on at least a part of the second surface, wherein the first and optionally the second functional coating is provided with a protective topcoat of the present invention.

[0110] In such circumstances, the first and second functional coatings may be the same or different, selected, among others, from the functional coatings described above.

[0111] The present topcoat finds further usefulness in that it provides the functional coating with sufficient mechanical durability to allow for the coating of the transparent substrate on the second opposite surface.

[0112] In some instances, compatible with other methods described above, a step of heat treatment may be effected before or after the optional flipping step, that is, the coated transparent substrate may be subjected to heat treatment before being provided with the second functional coating.

[0113] The invention thus also provides for a heat treated coated glazing comprising a functional coating and a magnetron sputtered mixed metal oxide topcoat comprising at least titanium, zirconium and silicon, wherein the topcoat comprises at least TiO _y and ZrO _z , and optionally SiO _x , wherein x, y, z range from 1 .8 to 2.2, wherein the topcoat comprises

- from 8 to 49 at% titanium,

- from 51 to 92 at% zirconium,

- from 0 to 9 at% silicon, for a total of 100 at% of the metals including impurities, and wherein the topcoat has a thickness from 0.1 to 10 nm. [0114] When the coated substrate can withstand a heat-treatment of the type tempering or bending without losing the optical and/or energetical properties for which they have been manufactured, said functional coating and/or the coated substrate may be called "heat-treatable" or "temperable".

[0115] In some instances, the functional coating may be "self-matchable". This means there is no or only few change in the optical and/or energetical properties, when the coated substrate undergoes a heat treatment of the type tempering or bending.

[0116] The Cl ELAB 1976 values (L*a*b*) are typically used to define the tints of the coated substrates. They are measured with illuminant D65/10 ⁰ .

[0117] A E*HT (Delta E* HT) = represents the tint variation during the heat treatment, i.e. the difference between before and after heat treatment colors.

[0118] "Self-matchability" may be considered when AE*HT 5, alternatively < 2 in transmission and in reflection and/or when there is no or little change in light transmission (T) and reflection (R) and energy values, that is, the difference between the values of THT, HT and color, before and after heat treatment remain < 5, alternatively < 2, in single glazing, where “HT” relates to the effect the heat treatment may have on the selected optical parameter (T, R or Delta E*) for the functional coating provided with the topcoat.

[0119] The present topcoat does not alter the self-matchability of the functional coating positioned underneath it, when such functional coating is self-matchable.

[0120] This has for advantage that non-heat treated and heat treated products can be placed next to each other for the same application, e.g. within a building fagade. This also has the advantage that the topcoat may be provided only on the product to be heat treated or only on the product which will not be heat treated, while self-matchability as defined, will be ensured between the nonheat treated and heat treated products.

[0121] The present topcoat is considered to be in contact with the surrounding environment, furthest away from the substrate. In only specific instances, compatible with other instances of the invention, may the coated substrate be further provided with at least one temporary protective layer over and in contact with the topcoat. Such “temporary” protective layer is typically removed upon washing or upon heat treatment of the substrate, as will be explained below.

[0122] In certain embodiments of the invention, temporary protective layers include carbon temporary protective layers, polymeric temporary protective layers, peelable protective layers.

[0123] Carbon protective layers include those layers provided by magnetron sputtering, usually having a thickness from 0.5 to 15 nm, alternatively from 1 to 10 nm, alternatively from 1 to 7 nm, and any value in-between. Such carbon protective coating is typically removed upon heat treatment of the transparent substrate, and thus eliminated at a rate of 99 - 100%, as may be measured by colorimetric methods. [0124] Polymeric temporary protective layers include those layers provided by the evaporation or reaction product of polymeric coating compositions containing polyvinyl alcohol, polyethylene, acrylic, or the like, which may be subsequently removed by aqueous washing, solvent washing, steam removal, thermal decomposition or combustion. Such polymeric coating compositions may be liquid solution, emulsion, suspension, slurry, or dispersion.

[0125] Peelable protective layers include those coatings formed from polyamide liquid compositions, or the like.

[0126] The temporary protective coating may thus be removed by washing, combustion, thermal decomposition, or peeling. The substrate can be processed, e.g., cut, trimmed, bent, shaped, and/or incorporated into a production article, before or after removal of the temporary protective coating.

[0127] Any of the above method may thus additionally comprise a step of depositing a carbon layer on the coated substrate.

[0128] A carbon protective topcoat has the advantage that is may also be deposited by a sputtering method, and may therefore be included in the same processing line without major technical constraint.

[0129] The present invention provides for a multiple glazing unit comprising at least one coated substrate as described in the various above embodiments.

[0130] The multiple glazing units include double or triple glazing or laminated glazing, wherein the coated substrate is associated with one or more other glass sheet(s), coated or not. The surfaces of a double glazing are typically indicated as follows: P1 is the surface of the outer sheet of glass, oriented towards the exterior; : P2 is the surface of the outer sheet of glass, oriented towards the inner space between the two glass sheets; P3 is the surface of the inner sheet of glass, oriented towards the inner space between the two glass sheets; P4 is the surface of the inner sheet of glass, oriented towards the interior. Such a nomenclature is also applicable for laminated glazing.

[0131] The coated surface of the glazing may be positioned in contact with the space between two sheets of glass, in the case of multiple glazing, or in contact with the adhesive layer, in the case of laminated glazing (P2 or P3).

[0132] Given its mechanical and chemical resistance, the coated surface of the coated substrate does not always need edge deletion prior to assembly into a multiple glazing unit and may even reach sufficient mechanical and chemical resistance to be positioned on an external surface of a multiple glazing unit, that is, facing and in contact with the exterior environment or interior environment of the building or vehicle (P1 or P4). The stack of thin layers may thus be provided on the surface of the glass substrate facing the interior of a building or vehicle (P2 of a single, non-laminated glass sheet, or P4 of a laminated glass or double glazing unit). In some instances, the coating stack may be positioned in contact with the exterior (P1). [0133] The coated substrate of the present invention may be useful in architectural glazings (door, window, vitrine, insulating glass (IG) window units, etc.), appliance applications (fridge door, oven door, etc.), and transportation applications (vehicle windows, skylights, windshield, side windows), where there is increasing need to have glasses with very pronounced curvatures and/or of complex shape (double curvature, S-shaped curvature, etc.).

[0134] In some instances, the coated substrate may be tempered. As a result of its safety and strength, tempered glass is used in a variety of demanding applications, including windows, shower doors, architectural glass doors and tables, refrigerator trays, as a component of bulletproof glass, and various types of plates and cookware.

[0135] The present coated substrate is thus highly durable, that is, is able to withstand certain chemical and/or mechanical tests detailed below, in some instances, both before and after an optional heat treatment. Optical parameters may be optimized without departing from the durability achieved by the functional coating applied on the presently claimed coated substrates. [0136] "Chemical durability" or "chemically durable" is used herein synonymously with the term of art "chemical stability" or "chemically resistant".

[0137] "Mechanical durability" or " mechanically durable" is used herein synonymously with the term of art "mechanical stability" or " mechanically resistant".

[0138] The present invention provides for the use of a topcoat for a transparent substrate provided with a functional coating, wherein the topcoat is a magnetron sputtered mixed metal oxide comprising at least TiO _y and ZrO _z , and optionally SiO _x , wherein x, y, z range from 1.8 to 2.2, wherein the topcoat comprises

- from 8 to 49 at% titanium,

- from 51 to 92 at% zirconium,

- from 0 to 9 at% silicon, for a total of 100 at% of the metals, and wherein the topcoat has a thickness from 0.1 to 10 nm; to improve durability by increasing the abrasion resistance by at least 20%, alternatively by at least 30%, alternatively by at least 40%.

[0139] Durability is assessed using the abrasion test as described in the below examples section. [0140] In some embodiments of the present use, compatible with other embodiments of the present invention, the above ranges for the Ti, Zr and Si in the topcoat may independently vary for one from the other. The amount of Ti may alternatively range from 10 to 47 at%, alternatively from 12 to 46 at%. The amount of Zr may alternatively range from 53 to 90 at%. The amount of Si may alternatively range from 1 to 8 at%, alternatively from 2 to 7 at%. These amounts may thus vary independently for each metal, provided the total is 100 at% of the metal, including impurities, as discussed above. EXAMPLES

[0141] Different stacks of functional layers were prepared, provided with a topcoat according to the present invention. In the bellow examples section, the composition of the topcoat is indicated in atomic percent of the Ti, Zr and optional Si elements, the sum of which will amount to 100 at%, as the defined active content. Said active content is thus considered as the sum of only the contributions of titanium, zirconium and optional silicon. Impurities present in the topcoats will thus not be listed nor their at% provided.

[0142] Mechanical stability was evaluated per the following abrasion test method, well known by the skilled person in the art.

[0143] The transparent substrate used in the present examples of glazing provided with a stack of thin layers stacks was standard float soda-lime, clear, 4 mm thickness, thoroughly cleaned before any coating deposition.

[0144] Other tests for chemical durability have been run, such as the Cleveland test (3, 7 and 10 days), the Climatic chamber test (3, 7 and 10 days), the Salt fog test (2, 5 and 10 days). The results are not outlined in details, as they are equivalent to standard results obtained with top layers such as those of comparative examples 1 and 2 below.

[0145] Typical tests for mechanical durability have been run, such as the Automatic Wet Rub Test (AWRT - 10, 50, 100, 250, 500 and 1000 cycles) or the Dry brush test (250, 500, 1000 cycles). The results are not outlined in details, as they are all passed successfully, leading to the present Abrasion test, inflicting harsher abrasion conditions.

[0146] The emissivity and the aesthetics of the functional coating were measured and were evidenced to not be impacted by the present topcoat.

[0147] Optical properties remain within an acceptable variation, with Delta TTC < 2%, Delta RTC < 2%, as measured using D65/2° llluminant and Delta E*TC < 5, as measured using D65/10 ⁰ I lluminant, when compared with the functional coating without the topcoat.

Dry Brush Test

[0148] The dry brush test (DBT) is run according to standard ASTM D2486-00 (test method “A”), for at least 250 cycles, alternatively for at least 500 cycles, here for 1000 cycles. This test may also be carried out on samples after they have been subjected to heat treatment (here referred to as “after bake”).

[0149] The results for each test described above are obtained by visually assessing samples in comparison with a defined scale of reference samples. An internal scale is set up for the DBT test, ranging from 0 to 10, with acceptable values of from 6 to 10. One value is typically the average of at least 3 samples for one experiment. Comparative examples in the tables below were prepared along the examples according to the invention as internal verification of the procedure for each “run” of experiment (set up in the below Tables). Abrasion Test

[0150] The abrasion test is a dry rub test performed as described in standard ISO11998:1998, using an abrasive pad of 900 g, for at least 1000 cycles. For the present invention the cycles are performed on a dry sample, without addition of any liquid.

[0151] This test may also be carried out on samples after they have been subjected to heat treatment (here referred to as “bake”). Typical test carried out take account of at least 250 cycles. [0152] The results for the test are obtained by visually assessing samples in comparison with a defined scale of reference samples. An internal scale is set up for the abrasion test, ranging from 0 to 10, with acceptable values from 7 to 10. One value is typically the average of at least 3 samples for one experiment. Comparative examples in the tables below were prepared along the examples according to the invention as internal verification of the procedure for each “run” of experiment (set up in the below Tables).

[0153] The present abrasion test is providing for harsher and more abrasive conditions than a typical AWRT or dry brush test known in the art.

[0154] The heat treatment conditions (or bake conditions) for the DBT and Abrasion tests involve placing the sample inside a convection furnace at a temperature of 670°C during 4 to 5 minutes.

[0155] In the following tables:

• Ag represents silver

• AZO2% represents a layer of aluminium doped zin oxide provided from a ceramic target comprising zinc oxide doped with 2%wt aluminium oxide

• SiN represents a layer of silicon nitride SisN4

• TiO is a layer of substoechiometric titanium oxide, provided from a ceramic target of TiOn with n equal to 1.65 up to 1.85.

• TZO is a layer of titanium zirconium mixed oxide, provided from a ceramic target of TiZrOx composed of TiO _x /ZrC>2 with proportions of 65 wt% TiC>2 and 35 wt% ZrC>2 (providing for 74 at% Ti and 26 at% Zr )

• ZnO represents a layer of zinc oxide without dopant, provided from a zinc metallic target

• ZSO5 represents a layer of zinc-tin mixed provided from a metallic target comprising Zn at 52 wt% and Sn at 48 wt%

• ZTAO as barrier layer (above and in contact with a silver layer) is a layer of zinc- titanium-aluminium oxide, provided from a ceramic target composed of ZnO: TiO _x :AhO3 in proportions of ZnO 85-95% wt, TiO _x 5-15% wt and AI2O3 1 .5-3 wt%, providing for composition of Zn:Ti:AI of 86.3:10.4:3.3 at% in the contact layer

• ZTAO as seed layer (under and in contact with a silver layer) is a layer of zinc-titanium- aluminium oxide, provided from a metallic target in proportions of Zn 88.8 wt%, Ti 9.5 wt% and Al 1 .7 wt% [0156] Unless otherwise indicated, standard deposition methods for the seed layers are based on a gas flow of a 80/20 mixture of oxygen and argon. Silicon nitride was sputtered in a gas flow of a mixture of argon and N2 with enough N2 to provide for a fully stoichiometric Sial^k [0157] Unless otherwise indicated, all thickness may have a thickness variation < 5%. [0158] Examples 1 to 7 correspond to the sixth example of multiple layer functional coatings comprising IR layers discussed above.

Example 1 - Comparative example C1

[0159] The following stack was provided:

Glass/ZSO5 (17.1 nm)/TZO (16.0 nm)/ZnO (5.0 nm)/Ag (10.5 nm)/ AZO (7.0 nm)/ZSO5 (16.1 nm)/SiN (17.0 nm)/ topcoat (4.0 nm)

[0160] In Example 1 , the topcoat was prepared according to one embodiment of the invention, using a ceramic target of 20 wt% TiOy and 80 wt% ZrOz, to provide for a topcoat comprising 27.8 at% of Ti and 72.2 at% of Zr, as provided in Table 1 , within the ranges as claimed, wherein y, z range from 1.8 to 2.2.

[0161] In Comparative example 1 , the topcoat was a typical TiZrO topcoat as provided in the art (0 at% Si), sputtered using a ceramic target of 65 wt% TiOy and 35 wt% ZrOz.

[0162] Results, provided in Table 1 , clearly indicate that the glazing of Example 1 offers the best mechanical resistance. The topcoat improves the durability by increasing the abrasion resistance by 65.0% (8.3 vs 5.0) without any negative impact on the optical performances of the coating.

TABLE 1

Examples 2 and 3 and Comparative example C2

[0163] The following stack was provided:

Glass/ZSO5 (24.5 nm)/ZTAO (9.0 nm)/Ag (18.0 nm)/ ZTAO (5.0 nm)/ZSO5 (16.5 nm)/SiN (20.0 nm)/ topcoat (5.0 nm).

[0164] In Example 2, the topcoat was prepared according to one embodiment of the invention, using the co-sputtering of a ceramic target of 20 wt% TiOy and 80 wt% ZrOz and a ceramic target of Si-ZrO2 in proportions of 65(Si)-35(ZrO2) wt%, to provide for a topcoat comprising Si, Ti and Zr in amounts of atomic %, as provided in Table 2, within the ranges as claimed, wherein x, y, z range from 1.8 to 2.2.

[0165] In Example 3, the topcoat was prepared according to one embodiment of the invention, using a ceramic target of 20 wt% TiOy and 80 wt% ZrOz, to provide for a topcoat comprising 27.8 at% of Ti and 72.2 at% of Zr, as provided in Table 2, within the ranges as claimed, wherein y, z range from 1.8 to 2.2.

[0166] Comparative example 2 was a typical TiZrO topcoat as provided in the art (0 at% Si), sputtered using a ceramic target of 65 wt% TiOy and 35 wt% ZrOz. [0167] The present amounts of each of Si, Ti and Zr in the mixed metal oxide topcoat allow to significantly improve the performance of the topcoat with regard to abrasion resistance, up to levels which had not been achieved previously, both before and after bake.

[0168] The abrasion resistance is paired with equivalent performances for all chemical durability tests, and that, without any negative impact on the optical performances of the coating. The topcoat improves the durability by increasing the abrasion resistance of Examples 2 and 3 vs Comparative example 1 as indicated in Table 2 (abrasion resistance without bake).

TABLE 2

Example 4 and Comparative examples C3 and C4

[0169] The following stack was provided:

Glass/ZSO5 (24.5 nm)/ZTAO (9.0 nm)/Ag (18.0 nm)/ ZTAO (5.0 nm)/ZSO5 (16.5 nm)/SiN (20.0 nm)/ topcoat (5.0 nm).

[0170] In Example 4, the topcoat was prepared according to one embodiment of the invention, using the co-sputtering of a ceramic target of TiOy and of a ceramic target of ZrOz, to provide for a topcoat comprising 13.2 at% of Ti and 86.8 at% of Zr, as provided in Table 3, within the ranges as claimed, wherein y, z range from 1.8 to 2.2. The ceramic target of TiOy contained aluminium oxide, herein considered as an impurity, not taken into account in the active content composition of the topcoat. The ceramic targets of TiOy and ZrOz contained less than 0.5 wt% impurities, not taken into account in the active content composition of the topcoat.

[0171] Comparative example 3 was a typical TiZrO topcoat as provided in the art (0 at% Si), sputtered using a ceramic target of 65 wt% TiOy and 35 wt% ZrOz.

[0172] Comparative example 4 was a ZrO2 topcoat as provided in the art, sputtered using a ceramic target of ZrOz, wherein z ranges from 1.8 to 2.2.

[0173] The abrasion resistance is paired with equivalent performances for all chemical durability tests, and that, without any negative impact on the optical performances of the coating. The topcoat improves the durability by increasing the abrasion resistance of Example 4 vs Comparative example 3 as indicated in Table 3 (abrasion resistance without bake).

[0174] Comparative example 4 having only ZrO _z did not withstand the heat treatment, with DBT after bake and abrasion resistance after bake, both decreasing significantly. That is, adding a slight proportion of TiO _y to a ZrO _z based layer assists in maintaining a high DBT resistance and a high abrasion resistance also after bake.

TABLE 3

Examples 5 and 6 - Comparative example C5

[0175] The following stack was provided:

Glass/ZSO5 (24.5 nm)/ZnO (5.0 nm)/Ag (17.4 nm)/ AZO (7.0 nm)/ZSO5 (21.0 nm)/SiN (22.0 nm)/ topcoat (4.0 nm).

[0176] In Example 5, the topcoat was prepared according to one embodiment of the invention, using the co-sputtering of a ceramic target of TiOy and of a ceramic target of ZrOz, to provide for a topcoat comprising 14.6 at% of Ti and 85.4 at% of Zr, as provided in Table 4, within the ranges as claimed, wherein y, z range from 1.8 to 2.2.

[0177] In Example 6, the topcoat was prepared according to one embodiment of the invention, using a ceramic target of 35 wt% TiOy and 65 wt% ZrOz, to provide for a topcoat comprising provide for a topcoat comprising 45.4 at% of Ti and 54.6 at% of Zr, as provided in Table 4, within the ranges as claimed, wherein y, z range from 1.8 to 2.2.

[0178] In Comparative example 5, the topcoat was a typical TiZrO topcoat as provided in the art (0 at% Si), sputtered using a ceramic target of 65 wt% TiOy and 35 wt% ZrOz.

[0179] Results, provided in Table 4, clearly indicate that the glazing of Examples 5 and 6 offer a better mechanical resistance. The topcoat improves the durability by increasing the abrasion resistance without any negative impact on the optical performances of the coating.

TABLE 4 Example 7 - Comparative example C6

[0180] The following stack was provided:

Glass/TiO (23.5 nm)/ZnO (5.0 nm)/Ag (11.8 nm)/ AZO (5.5 nm)/ZSO5 (16.0 nm)/SiN (18.0 nm)/ topcoat (4.0 nm)

[0181] In Example 7, the topcoat was prepared according to one embodiment of the invention, using a ceramic target of 20 wt% TiOy and 80 wt% ZrOz, to provide for a topcoat comprising 27.8 at% of Ti and 72.2 at% of Zr, as provided in Table 5, within the ranges as claimed, wherein y, z range from 1.8 to 2.2.

[0182] In Comparative example 6, the topcoat was a typical TiZrO topcoat as provided in the art (0 at% Si), sputtered using a ceramic target of 65 wt% TiOy and 35 wt% ZrOz.

[0183] Results clearly indicate that the glazing of Example 7 offers the best mechanical resistance. The topcoat improves the durability by increasing the abrasion resistance by 34.3% (7.8 vs 5.8) without any negative impact on the optical performances of the coating.

TABLE 5

Example 8 - Comparative example C7

[0184] The following stack was provided:

Glass/ZSO5 (24.5 nm)/ZnO (5.0 nm)/Ag (17.4 nm)/ AZO (7.0 nm)/ZSO5 (21.0 nm)/SiN (22.0 nm)/ topcoat (4.0 nm).

[0185] In Example 8, the topcoat was prepared according to one embodiment of the invention, using a ceramic target of 20 wt% TiOy and 80 wt% ZrOz, to provide for a topcoat comprising 27.8 at% of Ti and 72.2 at% of Zr, as provided in Table 6, within the ranges as claimed, wherein y, z range from 1.8 to 2.2.

[0186] In Comparative example 7, the topcoat was a typical TiZrO topcoat as provided in the art (0 at% Si), sputtered using a ceramic target of 65 wt% TiOy and 35 wt% ZrOz.

[0187] Results, provided in Table 6, clearly indicate that the glazing of Example 8 offers the best mechanical resistance. The topcoat improves the durability by increasing the abrasion resistance by 34.3% (8.0 vs 5.9) without any negative impact on the optical performances of the coating. TABLE 6

Example 9 and Comparative example C8

[0188] The following stack was provided:

Glass/ZSO5 (24.5 nm)/ZTAO (9.0 nm)/Ag (18.0 nm)/ ZTAO (5.0 nm)/ZSO5 (16.5 nm)/SiN (20.0 nm)/ topcoat (5.0 nm).

[0189] In Example 9, the topcoat was prepared according to one embodiment of the invention, using a ceramic target of 35 wt% TiOy and 65 wt% ZrOz, to provide for a topcoat comprising provide for a topcoat comprising 45.4 at% of Ti and 54.6 at% of Zr, as provided in Table 7, within the ranges as claimed, wherein y, z range from 1.8 to 2.2.

[0190] Comparative example 8 was a typical TiZrO topcoat as provided in the art (0 at% Si), sputtered using a ceramic target of 65 wt% TiOy and 35 wt% ZrOz.

[0191] The present amounts of each of Ti and Zr in the mixed metal oxide topcoat allow to significantly improve the performance of the topcoat with regard to abrasion resistance, up to levels which had not been achieved previously, both before and after bake.

[0192] The abrasion resistance is paired with equivalent performances for all chemical durability tests, and that, without any negative impact on the optical performances of the coating. The topcoat improves the durability by increasing the abrasion resistance of Example 9 vs Comparative example 8 as indicated in Table 7 (abrasion resistance without bake).

TABLE 7