Temperable solar-control glazing

Abstract

A transparent glass article for solar-control glazing, comprising at least one glass substrate provided on at least one of its faces with a stack comprising the following succession of layers, starting from the surface of said substrate: a first layer comprising silicon nitride, a functional layer comprising niobium and nitrogen, and a second layer comprising silicon nitride, wherein the functional layer comprising niobium and nitrogen is divided into at least two distinct parts, including a part A comprising niobium and optionally nitrogen and a part B comprising niobium and nitrogen, the nitrogen content in said part A being less than the nitrogen content in said part B.

Description

[0001] DESCRIPTION

[0002] TITLE Tempered solar-resistant glazing

[0003] The invention relates to insulating glazing known as solar control glazing, provided with stacks of thin layers, at least one of which is functional, i.e. it acts on solar radiation essentially by reflection and / or absorption of near infrared (solar) radiation. The present invention relates more particularly to glazing with layer(s), in particular those intended for anti-solar use, i.e. making it possible to limit the internal heating of the rooms of a building with respect to solar radiation. The glazing according to the invention can also have a low-emissive function in winter, i.e. make it possible to retain heat inside the building.

[0004] "Functional" or "active" layer(s) are understood to mean, within the meaning of the present application, the layer(s) of the stack which gives the stack the majority of its thermal insulation properties. Most often, the stacks of thin layers equipping the glazing give it improved solar control properties essentially through the intrinsic properties of this or these active layer(s). A functional layer acts on the flow of solar radiation passing through said glazing, as opposed to the other layers of the stack, generally made of a dielectric material such as silicon oxide, titanium oxide or silicon nitride, having the function of chemical or mechanical protection of said functional layer.

[0005] Such glazings equipped with stacks of thin layers act on the incident solar radiation either essentially by the absorption of the incident radiation, in particular near infrared radiation (solar) or far infrared radiation (heat) by the functional layer, or essentially by reflection by this same layer of said infrared radiation. Most often, said functional layer reflects part of the incident infrared radiation and absorbs another part.

[0006] They are grouped under the name of solar control glazing. They are marketed and used primarily either to essentially ensure protection of the home from solar radiation and prevent overheating, or essentially to ensure thermal insulation of the home and prevent heat loss. By antisolar, we therefore mean, within the meaning of the present invention, the ability of the glazing to limit the energy flow, in particular solar infrared radiation (1RS), typically of wavelengths between 780 and 2500 nm, passing through it from the outside to the inside of the home or passenger compartment.

[0007] In a known manner, and as indicated previously, the solar control properties, in particular anti-solar properties, of a glazing are given to it by a stack of layers of which at least one is said to be functional, that is to say that it has properties of reflection and / or absorption of solar infrared rays (in general both absorption and reflection) while allowing at least part of the visible radiation to pass through.

[0008] This capacity can for example be estimated by measuring the direct transmission factor of solar energy (also called energy transmission): TE in % is measured according to the EN410 standard (2011).

[0009] To estimate the thermal (far) infrared reflection capacity of glazing equipped with a stack of thin layers (including at least one functional layer in the sense described above), the measurement of emissivity is often used in the field, for example the emissivity at normal incidence 8 n as described in Annex A of ISO10292:1994.

[0010] Such functional layers may be, according to a first family, layers consisting entirely of precious metals, such as Ag, Au, Pt. The stacks according to the present invention do not include such layers based on silver, gold or platinum, or only in very negligible quantities, in particular in the form of unavoidable impurities. Similarly, the functional layers, or even the stacks, of the glass articles according to the invention are free of nickel or copper.

[0011] Alternatively, patent application WO01 / 21540 A1 has proposed a transparent substrate provided with a stack of thin layers consisting of a functional layer of niobium or niobium nitride surrounded by a sub-layer and an over-layer of silicon nitride. This solution is relatively satisfactory since the stack is "bendable", "temperable", mechanically resistant and has good optical characteristics.

[0012] By bendable or toughenable, we mean that the glazing shows little or no change in its appearance in general after the heat treatment of the glazing, and in particular the properties of light transmission and reflection, as well as colorimetry in transmission and reflection, which are substantially unchanged.

[0013] The solution proposed by application W001 / 21540 makes it possible to solve such a technical problem by using either metallic niobium or niobium nitride as a functional layer, between two dielectric layers based on silicon nitride. However, in the past, the use of purely metallic niobium (from a few nanometers to a few tens of nanometers) in this type of stack revealed a discrepancy in terms of light transmission level and color after quenching. However, this type of stack requires, due to its use, a perfect adjustment of the light transmission and reflection characteristics as well as the associated colors before and after quenching. Such problems did not arise with niobium nitride.Niobium nitride deposition is currently carried out using magnetron-assisted sputtering techniques from a niobium target in a nitrogen atmosphere (most often a mixture of argon and nitrogen gas N2). Such deposition is relatively slow and requires the use of several niobium cathodes in successive compartments of the sputtering device, which ultimately results in a slower production rate and a significant additional cost for the glazing. There is therefore a need to find a toughenable or bendable stack that does not have the disadvantages previously explained and in particular that is simple, reproducible and economical to deposit.

[0014] Such a stack on its glazing must also present an appearance showing little or no changes after heat treatment and give said glazing the best infrared reflection properties.

[0015] More specifically, the present invention relates to a transparent glass article for solar-protection glazing, comprising at least one preferably clear glass substrate provided on at least one of its faces with a coating consisting of a stack of thin layers, said stack comprising the following succession of layers, starting from the surface of said substrate:

[0016] - a first layer comprising silicon nitride,

[0017] - a functional layer comprising niobium and nitrogen,

[0018] - a second layer comprising silicon nitride, in which the functional layer comprising niobium and nitrogen is divided into at least two distinct parts, including a part A comprising niobium and optionally nitrogen and a part B comprising niobium and nitrogen, the nitrogen content in said part A of the functional layer being lower than the nitrogen content in said part B of the functional layer.

[0019] According to advantageous embodiments of the present invention, which can of course be combined with each other where appropriate:

[0020] - The first layer comprising silicon nitride has a physical thickness of between 1 and 100 nm, preferably between 2 and 50 nm, and more preferably between 5 and 30 nm.

[0021] - The second layer comprising silicon nitride has a physical thickness of between 1 and 100 nm, preferably between 10 and 70 nm, more preferably between 20 and 50 nm.

[0022] - The layer comprising niobium and nitrogen has a total physical thickness of between 5 and 50 nm, preferably between 10 and 30 nm.

[0023] - Said part A of the functional layer is closer to the surface of the substrate than said part B of the functional layer.

[0024] - Said part B of the functional layer is closer to the surface of the substrate than said part A of the functional layer.

[0025] - Part A of the functional layer has a thickness greater than part B of the functional layer. In particular, part A of the functional layer is preferably at least twice as thick as part B, and more preferably at least three times as thick as part B of the functional layer.

[0026] - Part A of the functional layer has a thickness between 4 nm and 35 nm, preferably between 10 and 20 nm.

[0027] - Part B of the functional layer has a thickness of between 1 and 15 nm, preferably between 1 and 10 nm, more preferably between 2 and 4 nm.

[0028] - Said part A of the functional layer comprises between 0 and 20 atomic% of nitrogen, preferably between 0% and 5% of nitrogen.

[0029] - Said part A of the functional layer does not contain nitrogen other than in the form of unavoidable impurities.

[0030] - Said part B of the functional layer comprises between 20% and 60 atomic% of nitrogen, preferably between 40% and 55 atomic% of nitrogen. - Niobium represents at least 50% of the metal atoms present in said functional layer, preferably at least 70% of the metal atoms present in said functional layer.

[0031] - The functional layer is made up of niobium and nitrogen, and possibly other minority metallic elements notably chosen from zirconium, titanium, tantalum, said minority metallic atoms being present in a quantity less than 30% of the quantity of niobium atoms present in said layer.

[0032] - Said first layer comprising silicon nitride, functional layer comprising niobium and nitrogen, and second layer comprising silicon nitride are successively and directly in contact with each other.

[0033] - The stack further comprises, above the second layer comprising silicon nitride, a protective layer comprising titanium oxide, zirconium oxide or a titanium and zirconium oxide, said layer preferably having a thickness of less than 10 nm, preferably less than 5 nm.

[0034] - The stack comprises or preferably consists of the succession of the following layers, each layer preferably being in direct contact with the next, starting from the surface of said substrate:

[0035] SiN1 / NbN / SiN2 / possibly TiO or ZrO or TiZrO

[0036] (i.e. either a TiO layer, a ZrO layer, or a TiZrO layer), wherein SiN1 denotes the first layer comprising silicon nitride, NbN denotes the functional layer comprising niobium and nitrogen, SiN2 denotes the second layer comprising silicon nitride, TiO denotes a layer comprising a titanium oxide, ZrO denotes a layer comprising a zirconium oxide, and TiZrO denotes a layer comprising a titanium and zirconium oxide.

[0037] - The stack does not include functional layers based on Ag, Au, Pt, Cu, Ni or stainless steel.

[0038] - The niobium / nitrogen atomic ratio in the first part of the layer comprising niobium and nitrogen is greater than the niobium / nitrogen ratio in the second part of the layer comprising niobium and nitrogen, preferably by at least a factor of 2 (i.e. the ratio between the two ratios is greater than or equal to 2), or even more preferably by a factor of 10.

[0039] - A metallic layer of titanium or a metallic alloy containing titanium is deposited between the niobium-based layer and the first and / or second silicon nitride-based layer, said metallic layer being in direct contact with said silicon nitride-based and niobium and nitrogen-based layers.

[0040] - The first and second layers comprising silicon nitride are in direct contact with the layer comprising niobium and nitrogen.

[0041] - Part A is made of niobium, excluding unavoidable impurities, and part B is made of niobium nitride, excluding unavoidable impurities. According to a still preferred embodiment, the molar ratio Nb / N is close to 1, in particular between 0.7 and 1.1.

[0042] - The item is thermally hardened and / or curved.

[0043] - The article presents in external reflection at least one parameter a* between 0 and -5, and a parameter b less than -10, in the colorimetric system L, a*, b*, under an angle of 10° and under illuminant D65.

[0044] - The difference AE(TL) after heating at 620°C for 10 minutes followed by quenching is less than 2.

[0045] - The difference AE(RLINT) after heating at 620°C for 10 minutes followed by quenching is less than 1.2.

[0046] - The difference AE(RLEXT) after heating at 620°C for 10 minutes followed by quenching is less than 1.5.

[0047] - The clear glass substrate has a thickness between 2 mm and 10 mm, preferably between 3 mm and 8 mm, in particular 4 mm or 6 mm.

[0048] - The first layer comprising silicon nitride is in contact with the glass substrate.

[0049] In a glazing according to the invention, the so-called solar control stack can be arranged on the face of the glazing facing the interior of the building or the passenger compartment that it equips and in particular on face 2 of a single glazing, the faces being conventionally numbered from the outside to the inside.

[0050] By stack side, we mean the face of the glazing on which the stack is deposited. By glass side we mean the face of the glazing opposite that on which the stack is deposited, in principle not covered. For the purposes of the present invention, the terms "external face" (or "external") and "internal face" or ("internal") refer to the position of the glazing when it is fitted to the building or vehicle for which it is intended.

[0051] We distinguish in this respect:

[0052] - the external light reflection Ri_ext, i.e. the light reflection measured on the face of the glazing exposed to the outside of the building or passenger compartment, and

[0053] - the interior light reflection Runt, i.e. the light reflection measured on the face of the glazing facing inwards.

[0054] In other words, the interior light reflection Runt is measured on the face with the stack of layers while the exterior light reflection Ri_ext is measured on the bare face of the glazing.

[0055] In general, all the luminous characteristics presented in this description, in particular, the luminous transmission TL and the luminous reflections RL, as well as the factor g, are obtained according to the principles and methods described in the standard NF EN 410 (2011) relating to the determination of the luminous and energy characteristics of glazing used in glass for construction.

[0056] In certain building glazing configurations, glazing is sought which also has a blue or neutral coloration in external reflection, i.e. on the side of the bare face of the glazing, opposite to that on which the stack is deposited, and visible from the outside of the building when the glazing is positioned.

[0057] To obtain such a property, it is necessary that the values ​​of a* and b*, and in particular of b*, in the international system L, a*, b* (typically under a viewing angle of 10° and under the illuminant Des), are negative or neutral in external reflection. Values ​​close to 0 are characteristic of a neutral coloration. A neutral or slightly negative value of a* and negative values ​​of b* reflect a blue coloration, the coloration appearing all the more blue as b* is negative.

[0058] To obtain a pronounced blue color, the value of a* should ideally be between 0 and -5 in external reflection. Values ​​of a* lower than -5 are not desired because they result in a cyan color tending towards green, which is less aesthetically desirable. Similarly, the value of b* should be lower than -10 and as negative as possible for a better rendering of the blue color.

[0059] Throughout the description, thicknesses are physical (geometric) thicknesses, unless otherwise stated.

[0060] In the functional layer according to the invention comprising niobium and nitrogen, niobium represents at least 50% of the metal atoms present in said layer (i.e. excluding the heteroatoms present, in particular nitrogen), and preferably more than 80% or even more than 90% of the metal atoms of said layers. Other minority metal elements may in particular be present, such as zirconium, titanium, tantalum. By minority is meant that said metal atoms are present in an amount of less than 30%, preferably 20% of the niobium atoms.

[0061] According to an advantageous embodiment, the functional layer comprises only the metallic elements mentioned above and nitrogen, with the exception of unavoidable impurities. According to a preferred embodiment, the functional layer comprises only niobium and nitrogen, with the exception of unavoidable impurities.

[0062] The formulation of the layers and in particular the content of the different metals and nitrogen constituting it, can be obtained classically by X-ray Photoelectron Spectroscopy (XPS), according to techniques well known in the field of materials, or any other method known for this purpose.

[0063] The functional layer comprising niobium and nitrogen may further comprise a small amount of oxygen, for example such that the O / Nb atomic ratio is less than 0.2, preferably less than 0.1 or even less than 0.05. According to a preferred embodiment, however, the layer comprising niobium and nitrogen does not comprise oxygen other than in the form of unavoidable impurities.

[0064] In the layers according to the invention comprising silicon nitride according to the invention, silicon preferably represents more than 80% or even more than 90% by weight of the metal atoms present in said layers, in particular excluding nitrogen atoms. More preferably, said layers comprising silicon nitride consist essentially of silicon nitride, but may also comprise another metal such as aluminum and / or zirconium. Aluminum is used in a well-known manner, in proportions of up to 10 atomic%, based on the sum of the elements Si and Al, or even more and preferably between 1 and 8 atomic%, based on the sum of the elements Si Zr and Al, in silicon targets used for the deposition of layers by cathode sputtering assisted by a magnetic field (magnetron).

[0065] In the layers according to the invention comprising silicon nitride, it is also possible to insert zirconium, silicon and zirconium together representing more than 90% of the metal atoms present in said layers, that is to say in particular except for the nitrogen atoms. Based on a formulation Si x Zr yN, the x / y ratio in said layer (atomic ratio Si / Zr) is between 1.5 and 6.0, and preferably is between 2.0 and 5.5, or even between 2.5 and 5.0. More preferably, said layers consist essentially of silicon nitride and zirconium, but may also comprise another metal such as aluminum. Aluminum is used in a well-known manner, in proportions of up to 10 atomic%, based on the sum of the elements Si, Zr and Al, or even more and preferably between 1 and 8 atomic%, based on the sum of the elements Si Zr and Al, in silicon targets used for the deposition of layers by cathode sputtering assisted by a magnetic field (magnetron).

[0066] The coatings according to the invention are conventionally deposited by deposition techniques of the type of vacuum sputtering assisted by a magnetic field of a cathode of the material or of a precursor of the material to be deposited, often called magnetron sputtering technique in the field. Such a technique is today conventionally used in particular when the coating to be deposited consists of a more complex stack of successive layers with thicknesses of a few nanometers or a few tens of nanometers.

[0067] The present invention also relates to single glazing (i.e. comprising only a single glass substrate) or a spandrel-type facade cladding panel incorporating a glass article as previously described.

[0068] According to another embodiment, the glass article according to the invention and as described previously can be incorporated into multiple glazing such as double glazing (i.e. comprising two glass substrates separated by a gas layer) or even laminated glazing comprising two sheets of glass bonded by a thermoplastic sheet such as PVB.

[0069] If the application more particularly targeted by the invention is glazing for buildings, it is clear that other applications are conceivable, notably in vehicle glazing (apart from the windscreen where very high light transmission is required), such as side windows, car roofs, rear windows.

[0070] The invention and its advantages are described in more detail below by means of the non-limiting examples below, according to the invention and comparative. In the examples and the description, the thicknesses given are physical.

[0071] All substrates are made of 6 mm thick clear glass of the Planilux® type marketed by Saint-Gobain Glass France.

[0072] All layers are deposited in a known manner by magnetic field-assisted sputtering (often called magnetron).

[0073] As is well known, the different successive layers are deposited in the successive compartments of the cathode sputtering device, each compartment being provided with a specific metal target in Si, or Nb chosen for the deposition of a specific layer of the stack.

[0074] More specifically, silicon nitride-based layers are deposited in device compartments from silicon targets comprising 8% by mass of aluminum, in a reactive atmosphere containing nitrogen (40% Ar and 60% N2). The silicon nitride-based layers, denoted SiN for convenience, therefore contain a little aluminum.

[0075] The deposition of metallic niobium in the functional layer is obtained by magnetron-assisted sputtering of a metallic niobium target in an argon atmosphere, according to conditions well known in the field.

[0076] The deposition of niobium nitride in the functional layer is obtained by magnetron-assisted sputtering of a metallic niobium target in an atmosphere of argon and nitrogen (volume ratio 50 / 50), according to conditions well known in the field. Under the deposition conditions, the atomic ratio Nb / N in the layer thus deposited is close to 1 (NbN formulation, 50 atomic% nitrogen in the layer), as determined by X-ray Photoelectron Spectroscopy (or ESCA for Electron Spectroscopy for Chemical Analysis).

[0077] Examples:

[0078] Example 1 (prior art)

[0079] This example complies with the teaching of application WO01 / 21540. In example 1 which follows, the glass substrate is successively covered with a stack of layers comprising a homogeneous functional layer of niobium nitride surrounded by layers based on silicon nitride (denoted SiN without assuming the N / Si ratio, i.e. 1.33 for a theoretical formulation SisN4 of the dielectric layer).

[0080] The stack therefore includes the succession of the following layers:

[0081] Glass / SiN (10 nm) / NbN (25 nm) / SiN (30 nm)

[0082] All layers are deposited in a known manner by magnetic field-assisted sputtering (often called magnetron) as previously indicated.

[0083] As is well known, the different successive layers are deposited in the successive compartments of the cathode sputtering device, each compartment being provided with a specific metal target in Si, or Nb chosen for the deposition of a specific layer of the stack.

[0084] Example 2 (according to the invention):

[0085] In Example 2 below, the glass substrate is this time successively covered with a stack of layers comprising a non-uniform thermal infrared absorbing / reflecting functional layer, i.e. comprising two parts (or portions) in the direction of its thickness, including a portion made of metallic niobium and a portion made of niobium nitride. Said functional layer is surrounded by dielectric layers based on silicon nitride (denoted SiN) without assuming the N / Si ratio.

[0086] The stack therefore includes the succession of the following layers:

[0087] Glass / SiN (10 nm) / NbN (3.5 nm) / Nb (14 nm) / SiN (30 nm)

[0088] The silicon nitride-based layers and the niobium nitride functional layer part are deposited using a procedure identical to that of example 1.

[0089] The metallic niobium functional layer part is also obtained by magnetron-assisted sputtering of a metallic niobium target in an argon atmosphere, according to conditions well known in the field. The glass articles thus synthesized according to conventional techniques are then heated and tempered according to conventional techniques in the field (heating at 620°C for 10 minutes followed by tempering).

[0090] The light transmission TL values ​​and the external light reflections Rext and internal light reflections Rint (stack side) are measured in the range 380 nm to 780 nm according to the methods described in the EN 410 (2011) standard on both glazings before and after toughening. The colorimetric values ​​in transmission, as well as in external reflection are measured according to the CIE LAB standard at an angle of 10° and with illuminant D65.

[0091] More precisely we measure:

[0092] - optical transmission TL: light transmission in % according to illuminant Des, as measured according to standard EN 410,

[0093] - the external reflection (i.e. that measured on the exterior side, when the coated glass is mounted in monolithic glazing in a room with the stack of layers on the face 2: external reflection RLEXT in %,

[0094] - the colorimetric data a*RLext, b*RLext in external reflection according to the colorimetry system (L, a*, b*)

[0095] - Inner reflection: the value of Runt in %,

[0096] All data obtained are shown twice in Table 1 below: before heat treatment and after heat treatment.

[0097] [Table 1]

[0098] *after soaking

[0099] It can be seen from the data reported in Table 1 that the optical and colorimetric properties are substantially the same for the two glazings (Example 2 according to the invention and comparative Example 1)

[0100] The thermal properties of glazing are measured according to the following parameters:

[0101] The value of emissivity 8 nof the two glazings is measured according to Annex A of the ISO10292:1994 standard - The direct transmission factor of solar energy (also called energy transmission): TE in % is measured according to the EN410 (2011) standard.

[0102] The variations in colorimetry in transmission, internal reflection and external reflection are then measured from the data reported in Table 2.

[0103] As indicated previously, a stack of layers in accordance with the present invention is considered bendable and / or temperable if, deposited on a preferably clear glass substrate, it undergoes a limited optical evolution which can in particular be quantified by placing itself in the CIE Lab color representation model (L, a*, b*) by a lower AE value less than 2.

[0104] We define AE as follows, for transmission AE(TL), external reflection AE(RLEXT) and internal reflection AE(RuNT) as follows:

[0105] AE = (AL 2 + Aa 2 + Ab 2 ) 1 / 2 for transmission, with:

[0106] Aa = a* (after treatment) - a* (before treatment),

[0107] Ab = b* (after treatment) - b* (before treatment)

[0108] AL = L* (after treatment) - L* (before treatment)

[0109] The results are reported in Table 2 below: [Table 2]

[0110] The above results show that example 2 according to the invention exhibits remarkable stability to quenching in the sense previously described, with less colorimetry variations than for reference example 1, both in transmission and in external and internal reflection.

[0111] In addition, an improvement in the insulation capacities of the glazing is observed, as shown by the reduction in energy transmission and normal emissivity for example 2.

Claims

CLAIMS 1. Transparent glass article for solar-protection glazing, comprising at least one glass substrate provided on at least one of its faces with a coating consisting of a stack of thin layers, said stack comprising the following succession of layers, starting from the surface of said substrate: - a first layer comprising silicon nitride, - a functional layer comprising niobium and nitrogen, - a second layer comprising silicon nitride, in which the functional layer comprising niobium and nitrogen is divided into at least two distinct parts, including a part A comprising niobium and optionally nitrogen and a part B comprising niobium and nitrogen, the nitrogen content in said part A being lower than the nitrogen content in said part B and in which the stack comprises the succession of the following layers, each layer being in direct contact with the next, from the surface of said substrate: SiN1 / NbN / SiN2 / optionally TiO, ZrO or TiZrO in which SiN1 denotes the first layer comprising silicon nitride, NbN denotes the functional layer comprising niobium and nitrogen, SiN2 denotes the second layer comprising silicon nitride, TiO denotes a layer comprising a titanium oxide, ZrO denotes a layer comprising a zirconium oxide and TiZrO denotes a layer comprising a titanium and zirconium oxide.

2. Glass article according to claim 1, in which the first layer comprising silicon nitride has a physical thickness of between 1 and 100 nm.

3. Glass article according to one of the preceding claims, in which the second layer comprising silicon nitride has a physical thickness of between 1 and 100 nm.

4. Glass article according to one of the preceding claims, in which the layer comprising niobium and nitrogen has a total physical thickness of between 5 and 50 nm.

5. Glass article according to one of the preceding claims, wherein said part A of the functional layer is closer to the surface of the substrate than said part B of the functional layer.

6. Glass article according to one of claims 1 to 4, wherein said part B of the functional layer is closer to the surface of the substrate than said part A of the functional layer.

7. Glass article according to one of the preceding claims, in which part A of the functional layer has a thickness greater than part B of the functional layer.

8. Glass article according to one of the preceding claims, in which part A of the functional layer has a thickness of between 4 nm and 35 nm.

9. Glass article according to one of the preceding claims, in which part B of the functional layer has a thickness of between 1 and 15 nm.

10. Glass article according to one of the preceding claims, in which said part A of the functional layer comprises between 0 and 20 atomic% of nitrogen.

11. Glass article according to the preceding claim, in which said part A of the functional layer does not contain nitrogen other than in the form of unavoidable impurities.

12. Glass article according to one of the preceding claims, in which said part B of the functional layer comprises between 20% and 60 atomic% of nitrogen.

13. Glass article according to one of the preceding claims, in which niobium represents at least 50% of the metal atoms present in said functional layer, preferably at least 70% of the metal atoms present in said functional layer.

14. Glass article according to one of the preceding claims, in which the functional layer is made up of niobium and nitrogen, and optionally other minority metallic elements notably chosen from zirconium, titanium, tantalum, said minority metallic atoms being present in an amount less than 30% of the amount of niobium atoms present in said layer.

15. Glass article according to one of the preceding claims, in which said first layer comprising silicon nitride, functional layer comprising niobium and nitrogen, and second layer comprising silicon nitride are successively and directly in contact with each other.

16. Article according to one of the preceding claims, in which the stack further comprises, above the second layer comprising silicon nitride, a protective layer comprising titanium oxide, titanium oxide zirconium or a titanium and zirconium oxide, said layer preferably having a thickness of less than 10 nm.

17. Article according to one of the preceding claims, in which the stack is constituted by said succession of layers.

18. Article according to one of the preceding claims, characterized in that the stack does not comprise functional layers based on Ag, Au, Pt, Cu, Ni or stainless steel.

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