Transparent substrate with a coating of a thin-layer stack

Description

[0001] The invention relates to a transparent substrate coated with a stack of thin layers comprising a silver-based functional layer as well as a glazing comprising such a substrate.

[0002] The invention relates more particularly to the use of such substrates for manufacturing reinforced thermal insulation glazing with a high solar factor. Such glazing is, for example, intended for cold climates to equip buildings, in particular with a view to reducing heating efforts in winter (so-called "low-emissivity" glazing) and maximizing free solar gain.

[0003] The SHGC solar factor is defined as the ratio between the solar energy gain entering the room through the glazing and the incident solar energy. According to the NFRC 200-2017 standard, the solar energy gain is the sum of the energy flux transmitted directly through the glazing and the energy flux absorbed and then re-emitted to the interior by the glazing.

[0004] One type of thin-film stack known to provide such thermal insulation properties consists of a silver-based functional layer (or silver layer).

[0005] Silver-based functional layers are useful for several reasons: by reflecting infrared, thermal, or solar radiation, they impart low-emissivity or solar control functions to the material. Being electrically conductive, they also make it possible to produce conductive materials, such as heated glazing or electrodes.

[0006] The silver-based functional layers are deposited between coatings based on dielectric materials (hereinafter dielectric coating) which generally comprise several dielectric layers allowing the optical properties of the stack to be adjusted and high transmission in the visible range to be maintained. These dielectric layers also protect the silver layers from chemical or mechanical attack.

[0007] Application WO 2012 / 127162, belonging to the applicant, discloses a transparent substrate provided with a stack of thin layers comprising a silver layer arranged between two particular non-metallic dielectric coatings making it possible to increase the solar factor of a glazing equipped with such a substrate and to obtain an acceptable coloring, in particular in transmission. To this end, the stack preferably comprises: a lower dielectric coating, located below the silver layer, comprising at least one high refractive index layer, made of a material with a refractive index greater than or equal to 2.20, an upper dielectric coating, located above the silver layer comprising at least the sequence of high and low index thin layers deposited in the following order above the silver-based layer: at least one high refractive index layer, made of a material with a refractive index greater than or equal to 2.20, at least one low refractive index layer, made of a material with a refractive index less than or equal to 1.70.

[0008] Application WO2017 / 42463, also belonging to the applicant, also relates to coated transparent substrates making it possible to increase the solar factor of the glazing. The following stack is for example described in Example 1: Substrate / Si 3 N 4 / TiOx / SiZrN / ZnO / Ag / NiCr / ZnO / TiOx / SiO 2 . The solar factor is however insufficient.

[0009] Also known is document WO 2018 / 165357 (Guardian) which discloses an article coated with a low-emissivity stack, and in particular the following stack: Substrate / SiN / ZrSiN / TiO 2 / ZnAlO / Ag / barrier TiO 2 / ZrSiN / SiN / SiO 2 . The ZrSiN layer must contain more Zr than Si and therefore has an index close to that of the TiO 2 layer.

[0010] WO 2018 / 047037 A1 (Guardian) also discloses a transparent substrate coated with a low-emissivity stack.

[0011] Application WO 2007 / 101964 discloses, in the case where the dielectric coating located below the silver layer comprises at least one dielectric layer based on nitride, in particular silicon and / or aluminum nitride, dielectric coatings comprising: wetting layers intended to promote wetting and nucleation of the silver layer, for example a layer based on crystallized zinc oxide, smoothing layers of a mixed oxide located below the wetting layer contributing to the adequate growth of the silver layer above the wetting layer.

[0012] In this paper, all thin layers of the upper dielectric coating, having a thickness greater than 5 nm, have substantially equal refractive indices.

[0013] Therefore, dielectric coatings made of such thin layers form a medium with a substantially homogeneous refractive index although the materials that constitute them are different.

[0014] There is a strong demand for glazing combining the following properties: high light transmission, notably at least 70%, 75% or even 78%, a high solar factor, low emissivity, and low heat loss resulting in low Ug coefficients.

[0015] The solar factor of the glazing "FS or g" corresponds to the ratio in % between the total energy entering the room through the glazing and the incident solar energy. The solar factor therefore measures the contribution of a glazing to the heating of the "room". The lower the solar factor, the lower the solar gains.

[0016] The heat loss coefficient, also known as the "Ug value," expresses the heat flow per square meter of glazing caused by a temperature difference between the exterior environment and the interior separated by the glazing. The lower this value, the lower the heat loss and the better the insulation.

[0017] The performance of low-emissivity glazing is based on the compromise between the solar factor that must be maximized (solar energy input) and the Ug value that must be obtained as low as possible (thermal transmission coefficient indicating the thermal losses of the glazing).

[0018] Achieving a low solar factor and low heat loss in combination is challenging. To achieve low heat loss, particularly with single-layer silver-based functional stacks, the stack's emissivity must be reduced without increasing absorption or reflection.

[0019] However, it is very difficult to reduce emissivity without reducing light transmission. Indeed, increasing the thickness of the silver layers allows for lowering emissivity and therefore obtaining a lower thermal transmission coefficient Ug, but this is to the detriment of light transmission. Since reducing light transmission also leads to a reduction in the solar factor, this solution does not allow for maximizing solar gain.

[0020] Thus, the development of low Ug value glazing with a high solar factor is essential to improve the energy efficiency of buildings incorporating these glazings.

[0021] The applicant has surprisingly discovered that when the dielectric coating under the functional layer is formed of layers which form an increasing index gradient starting from the substrate and the dielectric coating above the functional layer is formed of layers which form a decreasing index gradient, it is possible to increase the solar factor while maintaining low emissivity. It is then also possible to reduce the thickness of the functional layer.

[0022] The invention relates to a transparent substrate coated with a thin-film stack as defined in the set of claims. The thin-film stack comprises, starting from the substrate, a lower dielectric coating, a silver-based functional metal layer and an upper dielectric coating, each dielectric coating comprising several dielectric layers. The lower dielectric coating comprises a succession of at least three dielectric layers having increasing refractive indices, the index difference between the three layers being at least 0.15, a smoothing layer and a wetting layer, preferably based on zinc oxide (ZnO). The upper dielectric coating comprises a zinc oxide-based layer and a succession of at least two layers having decreasing refractive indices.

[0023] The solution of the invention consisting of the choice of particular sequences of dielectric layers makes it possible to optimize the optical filter and to increase the conductivity of the silver. These two improvements contribute to increasing the solar factor without impacting the heat loss coefficient Ug.

[0024] The transparent substrate coated according to the invention may have the following characteristics alone or in combination: the three dielectric layers having increasing refractive indices of the lower dielectric coating each have a thickness greater than 3 nm, the two dielectric layers having decreasing refractive indices of the lower dielectric coating each have a thickness greater than 3 nm, the smoothing layer is based on a mixed oxide comprising at least two metals chosen from tin Sn, zinc Zn, gallium Ga and indium In, preferably a mixed oxide layer based on Sn and Zn, the smoothing layer has a thickness greater than 4 nm, each dielectric coating comprises at least one high-index layer based on an oxide or nitride, having a refractive index greater than 2.20, preferably greater than 2.25 and a thickness greater than 5 nm, each dielectric coating comprises at least one dielectric layer based on oxide or nitride and having a refractive index less than 2.15,preferably less than 2.05 and a thickness greater than 3 nm, the upper dielectric coating comprises a succession of at least three layers of decreasing indices, each with a thickness greater than 5 nm, the index difference of which is greater than 0.15, or even greater than 0.20, the upper dielectric coating comprises a layer with a refractive index of less than 1.70 and having a thickness greater than 5 nm or 10 nm, the upper dielectric coating comprises three layers of dielectric, successively of high index, intermediate index and low index; the intermediate index layer having a thickness: greater than the thickness of the high index layer, and greater than the thickness of the low index layer, the lower dielectric coating comprises: a dielectric layer having a refractive index of less than 2.20, a dielectric layer having a refractive index of between 2.20 and 2.40,a dielectric layer having a refractive index greater than 2.40, a smoothing layer, a wetting layer, the lower dielectric coating comprises: a dielectric layer having a refractive index less than 2.20 chosen from layers based on silicon nitride, a dielectric layer having a refractive index of between 2.20 and 2.40 chosen from layers based on silicon nitride and zirconium, preferably located in contact with the silicon nitride layer, a dielectric layer having a refractive index greater than 2.40 chosen from layers based on oxide, preferably located in contact with the silicon nitride and zirconium layer, a smoothing layer based on zinc and tin oxide, preferably located in contact with the oxide-based layer, a wetting layer based on zinc oxide, preferably located in contact with the layer based on zinc oxide and tin,the lower dielectric coating comprises: a dielectric layer having a refractive index lower than 2.20 chosen from silicon nitride-based layers having a thickness of between 2 and 15 nm or between 2 and 10 nm, a dielectric layer having a refractive index of between 2.20 and 2.40 chosen from silicon nitride and zirconium-based layers having a thickness of between 5 and 20 nm or between 10 and 20 nm, preferably located in contact with the silicon nitride layer, a dielectric layer having a refractive index greater than 2.40 chosen from oxide-based layers having a thickness of between 5 and 20 nm or between 10 and 20 nm, preferably located in contact with the silicon nitride and zirconium layer, a smoothing layer based on zinc and tin oxide having a thickness of between 2 and 15 nm, between 3 and 10 nm or between 3 and 8 nm,preferably located in contact with the oxide-based layer, a zinc oxide-based wetting layer having a thickness of between 2 and 15 nm, between 3 and 10 nm or between 3 and 8 nm, preferably located in contact with the zinc and tin oxide-based layer, the upper dielectric coating comprises: a zinc oxide-based layer, a dielectric layer having a refractive index greater than 2.20, a dielectric layer having a refractive index less than 2.20, the upper dielectric coating comprises: a zinc oxide-based layer, a dielectric layer having a refractive index greater than 2.20, a dielectric layer having a refractive index less than 2.20, optionally a dielectric layer having a refractive index less than 1.70, the upper dielectric coating comprises: a zinc oxide-based layer, a dielectric layer having a refractive index greater than 2,20 chosen from layers based on silicon nitride and zirconium, preferably located in contact with the zinc oxide-based layer, a dielectric layer having a refractive index of less than 2.20 chosen from layers based on silicon nitride, preferably located in contact with the silicon nitride-based layer and zirconium, a dielectric layer having a refractive index of less than 1.70 chosen from layers based on silicon oxide, preferably located in contact with the silicon nitride-based layer, the upper dielectric coating comprises: a zinc oxide-based layer having a thickness of between 2 and 15 nm, between 3 and 10 nm or between 5 and 10 nm, a dielectric layer having a refractive index greater than 2.20 chosen from layers based on silicon nitride and zirconium having a thickness of between 5 and 40 nm, between 5 and 20 nm or between 10 and 15,preferably located in contact with the zinc oxide-based layer, a dielectric layer having a refractive index of less than 2.20 chosen from silicon nitride-based layers having a thickness of between 5 and 60 nm, between 10 and 50 or between 20 and 40, preferably located in contact with the silicon nitride and zirconium-based layer, a dielectric layer having a refractive index of less than 1.70 chosen from silicon oxide-based layers having a thickness of between 5 and 150 nm, between 10 and 100 or between 15 and 100, preferably located in contact with the silicon nitride-based layer, the stack further comprises an upper protective layer, the stack further comprises a single functional metal layer, the stack further comprises a blocking layer deposited directly on the silver-based functional metal layer, the thickness of which is less than 5.0 nm, less than 4,0 nm, less than 3.0 nm, less than 2.5 nm, less than 2.0 nm, more preferably less than 1.5 nm, the silver-based functional metal layer has a thickness of between 5 and 20 nm, preferably between 6 and 10 nm, more preferably between 7 and 8.5 nm.

[0025] According to an advantageous embodiment, the upper dielectric coating comprises at least the sequence of thin layers deposited in the following order above the functional layer: at least one high refractive index layer (hereinafter "high index layer"), made of material with a refractive index greater than or equal to 2.20, the physical thickness of the high refractive index layer being between 10 and 40 nm, at least one low refractive index layer (hereinafter "high index layer"), made of material with a refractive index less than or equal to 2.00, the physical thickness of the low refractive index layer being between 15 and 100 nm.

[0026] According to an advantageous embodiment, the upper dielectric coating, located above the silver-based functional metal layer, comprises: a zinc oxide-based layer, a high-index layer, a layer having an intermediate refractive index, and a layer having a refractive index less than 2.0.

[0027] Preferably all dielectric layers of the upper dielectric coating, deposited above the zinc oxide layer, form a decreasing index gradient.

[0028] In particular, each layer of the lower dielectric coating having a thickness greater than 3 nm other than the wetting layer and the smoothing layer, forms an increasing index gradient.

[0029] The stack is deposited by magnetic field-assisted sputtering (magnetron process). According to this advantageous embodiment, all layers of the stack are deposited by magnetic field-assisted sputtering.

[0030] The invention also relates to: a glazing according to the invention mounted on a vehicle or on a building, and the method for preparing a laminated glazing according to the invention, the use of a laminated glazing according to the invention as solar control glazing for the building or vehicles, a building, a vehicle comprising a glazing according to the invention.

[0031] The preferred characteristics which appear in the remainder of the description are applicable both to the substrate according to the invention and, where appropriate, to the glazing, the method, the use, the building or the vehicle according to the invention.

[0032] All the luminous characteristics described are obtained according to the principles and methods of the ISO 9050 standard relating to the determination of the luminous and solar characteristics of glazing used in glass for construction.

[0033] Conventionally, refractive indices are measured at a wavelength of 550 nm.

[0034] According to the invention, two elements such as layers or substrates have substantially equal refractive indices, when the absolute value of the difference between the refractive indices of the two materials constituting said layers or substrates at 550 nm is less than or equal to 0.15.

[0035] According to the invention, layers are considered to have different refractive indices when the absolute value of the difference between the refractive indices measured at 550 nm of the two materials constituting them is greater than or equal to 0.15, greater than or equal to 0.25, greater than 0.30, greater than 0.40, greater than 0.50, greater than 0.60, greater than 0.70 or greater than 0.80.

[0036] In the absence of a specific stipulation, the expressions "above" and "below" do not necessarily mean that two layers and / or coatings are placed in contact with each other. When it is specified that a layer is deposited "in contact" with another layer or coating, this means that there cannot be one (or more) layer(s) interposed between these two layers (or layer and coating).

[0037] In this description, unless otherwise indicated, the expression "based on", used to qualify a material or a layer as to what it contains, means that the mass fraction of the constituent that it comprises is at least 50%, in particular at least 70%, preferably at least 90%.

[0038] Thus, the total optical thickness of the antireflective coating is made up of the sum of all the optical thicknesses of the dielectric layers constituting this coating.

[0039] The stack is deposited by magnetic field-assisted sputtering (magnetron process). According to this advantageous embodiment, all layers of the stack are deposited by magnetic field-assisted sputtering.

[0040] Unless otherwise stated, thicknesses referred to in this document are physical thicknesses and layers are thin layers. A thin layer is defined as a layer with a thickness between 0.1 nm and 100 micrometers.

[0041] Throughout the description, the substrate according to the invention is considered to be laid horizontally. The stack of thin layers is deposited above the substrate. The meaning of the expressions "above" and "below" and "lower" and "upper" is to be considered in relation to this orientation. In the absence of a specific stipulation, the expressions "above" and "below" do not necessarily mean that two layers and / or coatings are arranged in contact with each other. When it is specified that a layer is deposited "in contact" with another layer or a coating, this means that there cannot be one or more layers interposed between these two layers.

[0042] The silver-based metal functional layer comprises at least 95.0%, preferably at least 96.5% and more preferably at least 98.0% by mass of silver relative to the mass of the functional layer. Preferably, the silver-based metal functional layer comprises less than 1.0% by mass of metals other than silver relative to the mass of the silver-based metal functional layer.

[0043] In particular, the silver-based functional metal layer has a thickness of between 5 and 20 nm, preferably between 6 and 10 nm, more preferably between 7 and 8.5 nm. The silver-based functional metal layers have a thickness: greater than 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm or 16 nm, and / or less than 25 nm, 22 nm, 20 nm, 18 nm.

[0044] The stack may also further comprise a blocking layer deposited directly on the silver-based functional metal layer. According to this embodiment, the blocking layer is chosen from metal layers, metal nitride layers, metal oxide layers and metal oxynitride layers based on one or more elements chosen from niobium Nb, tantalum Ta, titanium Ti, chromium Cr or nickel Ni or based on an alloy obtained from at least two of these metals. When these blocking layers are deposited in metallic, nitrided, oxynitrided or under-oxidized form, these layers may undergo partial or total oxidation depending on their thickness and the nature of the layers surrounding them, for example, at the time of deposition of the following layer or by oxidation in contact with the underlying layer.

[0045] The blocking layers are chosen from: metallic layers based on a metal or a metallic alloy, metallic nitride layers, and metallic oxynitride layers of one or more elements chosen from titanium, zinc, tin, nickel, chromium and niobium, metallic oxide layers of one or more elements chosen from titanium, nickel, chromium and niobium.

[0046] The blocking layers may in particular be, as deposited, layers of Ti, TiN, TiOx, Nb, NbN, Ni, NiN, Cr, CrN, NiCr, NiCrOx, NiCrN, SnZnN.

[0047] Preferably, the blocking layers are titanium-based and are metal layers or metal oxide layers, preferably under stoichiometric oxygen.

[0048] According to an advantageous embodiment, the stack does not comprise a blocking layer located below and in contact with the silver-based metallic functional layer.

[0049] The thickness of the blocking layer is generally between 0.1 and 5.0 nm, preferably: of at least 0.1 nm or at least 0.5 nm and / or at most 5.0 nm or at most 2.0 nm, at most 1.0 nm.

[0050] Dielectric coatings comprise dielectric layers. By "dielectric layer" for the purposes of the present invention, it is to be understood that from the point of view of its nature, the material is "non-metallic", i.e. is not a metal. In the context of the invention, this term designates a material having an n / k ratio over the entire visible wavelength range (from 380 nm to 780 nm) equal to or greater than 5. n designates the real refractive index of the material at a given wavelength and k represents the imaginary part of the refractive index at a given wavelength; the n / k ratio being calculated at a given wavelength identical for n and for k.

[0051] The thickness of a dielectric coating corresponds to the sum of the thicknesses of the layers constituting it. Preferably, the dielectric coatings have a thickness greater than 10 nm, greater than 15 nm, between 15 and 200 nm, between 15 and 100 nm or between 15 and 70 nm.

[0052] For the purposes of the invention, the term "total optical thickness" means the sum of all the optical thicknesses of the layers considered, each optical thickness being, as explained above, the product of the physical (or real) thickness of the layer with its refractive index measured at 550 nm.

[0053] The dielectric layers of the coatings have the following characteristics alone or in combination: they are deposited by magnetic field-assisted cathode sputtering, they are chosen from oxides, nitrides or oxynitrides of one or more elements chosen from titanium, silicon, aluminum, zirconium, tin and zinc, they have a thickness generally greater than or equal to 1 nm, greater than 2 nm, preferably between 4 and 200 nm, preferably between 5 and 100 nm.

[0054] Dielectric layers, in addition to their optical function, can have various other functions. Examples include stabilizing layers, smoothing layers, and barrier layers.

[0055] Among the dielectric layers, a distinction is made, depending on their refractive index at 550 nm, between low refractive index layers, intermediate refractive index layers and high refractive index layers. The low refractive index layers have a refractive index of less than 2.00, preferably less than 1.70. The intermediate refractive index layers have a refractive index of between 2.0 and 2.2. The high refractive index layers have a refractive index of greater than 2.2.

[0056] A wetting layer is understood to mean a layer made of a material capable of stabilizing the interface with the functional layer. The wetting layers are based on zinc oxide, optionally doped with at least one other element, such as aluminum. The zinc oxide is crystallized. The zinc oxide-based layer comprises, in increasing order of preference, at least 90.0%, at least 92%, at least 95%, at least 98.0% by mass of zinc relative to the mass of elements other than oxygen in the zinc oxide-based layer.

[0057] The wetting layers have, in order of increasing preference, a thickness: of at least 3.0 nm, of at least 5.0 nm, and / or of at most 25 nm, of at most 10 nm, of at most 8.0 nm.

[0058] The wetting layer can be in direct contact with the silver-based functional metal layer.

[0059] A smoothing layer is a layer whose function is to promote the growth of the wetting layer in a preferential crystallographic orientation, which promotes the crystallization of the silver layer by epitaxial phenomena. The smoothing layer is located below and preferably in contact with a wetting layer.

[0060] The mixed oxide smoothing layer can be described as "non-crystallized" in the sense that it can be completely amorphous or partially amorphous. The smoothing layer is not completely crystallized, throughout its thickness. It cannot be metallic in nature because it is based on mixed oxide (a mixed oxide is an oxide of at least two elements).

[0061] The advantage of such a smoothing layer is that it allows for an interface with the wetting layer that is not very rough. This low roughness can be observed under a transmission electron microscope. Furthermore, the wetting layer is better textured and also has a more marked preferential crystallographic orientation.

[0062] Each smoothing layer is thus made of a different material, both from a crystallographic and stoichiometric point of view, from that of the wetting layer under which it is directly placed.

[0063] Preferably, the smoothing layer is a layer based on a mixed oxide of at least two metals chosen from Sn, Zn, In, Ga. A preferred mixed oxide is zinc and tin oxide. The smoothing layer is preferably a layer of mixed oxide of zinc and tin, optionally doped.

[0064] The index of the smoothing layer is preferably less than 2.2. Furthermore, the smoothing layer preferably has a thickness between 0.1 and 30 nm and more preferably between 0.2 and 10 nm.

[0065] The smoothing layers have, in order of increasing preference, a thickness: of at least 0.5 nm, of at least 1.0 nm, and / or of at most 25 nm, of at most 15 nm, of at most 10 nm, of at most 8 nm.

[0066] The wetting layer is advantageously directly in contact with the silver-based metal layer. This means that, in this case, the stack does not include a blocking layer under the silver-based functional layer.

[0067] The upper dielectric coating further comprises a zinc oxide (ZnO)-based layer disposed between the silver-based functional metal layer and the succession of at least two layers with decreasing indices.

[0068] In particular, each dielectric coating may comprise at least one high-index layer based on an oxide or nitride, having a refractive index greater than 2.20, preferably greater than 2.25 and preferably having a thickness greater than 5 nm.

[0069] High refractive index layers can have a refractive index: greater than 2.25, greater than 2.30, greater than 2.35 or greater than 2.40. less than 2.60, less than 2.50, less than 2.40.

[0070] The high-index layer based on metal oxide may be chosen from layers based on titanium oxide or nitride, zirconium, niobium or an alloy of metals chosen from the group consisting of Ti, Zn, Zr, Sn, Si and AI.

[0071] High refractive index layers can be chosen from: layers based on titanium oxide (n550 = 2.4), layers based on mixed titanium oxide and another component selected from the group consisting of Zn, Zr and Sn, layers based on a layer of zirconium nitride (n 550 = 2.55), layers based on silicon and zirconium nitride (n550 nm = 2.20 - 2.40), layers based on a layer of zirconium oxide, layers based on manganese oxide MnO (n550 = 2.16), layers based on a layer of tungsten oxide (n550 = 2.15), layers based on a layer of niobium oxide (n550 = 2.30), layers based on a layer of bismuth oxide (n 550 = 2.60).

[0072] The thickness of the high-index layer is, in order of increasing preference, between 5 and 100 nm, between 8 and 40 nm, between 10 and 30 nm and between 15 and 25 nm.

[0073] In particular, each dielectric coating comprises at least one dielectric layer based on oxide or nitride and having a refractive index of less than 2.20, preferably less than 2.15, preferably less than 2.05. These layers may have a thickness greater than 3 nm. Such layers are layers of intermediate refractive index.

[0074] The low index layers may have a refractive index of less than 1.70, less than 1.6 or less than 1.5. The low index layers are preferably silicon oxide-based layers. The silicon oxide-based layers preferably consist of more than 80% by weight of silicon oxide based on the formulation of the simple oxide SiO 2 , and optionally of at least one other element preferably selected from the group consisting of Al, C, N, B, Sn, Zn and very preferably from Al, B or C. Preferably said layers consisting essentially of silicon oxide consist of more than 90% by weight of silicon oxide, based on the formulation of the simple oxide SiO 2 .

[0075] According to an advantageous embodiment, the upper dielectric coating comprises three layers of dielectric, successively a high index layer, an intermediate index layer and a low index layer; the intermediate index layer having a thickness: greater than the thickness of the high index layer, and greater than the thickness of the low index layer.

[0076] The thin film stack may comprise a single functional layer.

[0077] An example of a stack suitable according to the invention comprises from the substrate the following characteristics, alone or in combination: a lower dielectric coating comprising: three layers of increasing index with an index difference between each successive layer of at least 0.15, preferably at least 0.20; 2 to 15 nm, preferably 3 to 10 nm of a layer having an index between 1.45 and 2.00; 5 to 30 nm, preferably 10 to 20 nm of a layer having an index between 1.80 and 2.30; 5 to 30 nm, preferably 10 to 20 nm of a layer having an index between 2.20 and 2.50; a smoothing layer of 2 to 10 nm, preferably 3 to 8 nm; a wetting layer of 2 to 10 nm, preferably 3 to 8 nm; a silver-based functional metal layer of 6 to 10 nm, preferably 7 to 8.5 nm; a blocking layer of 0.2 to 3 nm, preferably 0.5 to 2.5 nm; a top dielectric coating, comprising: a ZnO layer of 4 to 15 nm, preferably 5 to 10 nm;three layers of decreasing index with an index difference between each successive layer of at least 0.15, preferably at least 0.20: 5 to 20 nm, preferably 10 to 15 nm of a layer having an index between 2.20 and 2.50; 5 to 50 nm, preferably 10 to 40 nm of a layer having an index between 1.80 and 2.30; 10 to 100 nm, preferably 15 to 80 nm of a layer having an index between 1.45 and 2.00; optionally a protective layer, for example based on 0.2 to 5 nm, preferably 0.5 to 3 nm of TiOx or SnZnO. ;

[0078] Advantageously: the silver-based functional metal layer is located above and in contact with the wetting layer, and / or the wetting layer is located above and in contact with the smoothing layer, and / or the smoothing layer is located above and in contact with a high index layer

[0079] The stack of thin layers may optionally comprise a protective layer. The protective layer is preferably the last layer of the stack, i.e. the layer furthest from the coated substrate of the stack (before heat treatment). These layers generally have a thickness of between 0.5 and 10 nm, preferably 1 and 5 nm. This protective layer may be chosen from a layer of titanium, zirconium, hafnium, zinc and / or tin, this or these metals being in metallic, oxidized or nitrided form.

[0080] According to one embodiment, the protective layer is based on zirconium and / or titanium oxide, preferably based on zirconium oxide or titanium and zirconium oxide.

[0081] The transparent substrates according to the invention are preferably made of a rigid mineral material, such as glass, or organic polymer-based (or polymer).

[0082] The transparent organic substrates according to the invention may also be made of polymer, rigid or flexible. Examples of polymers suitable according to the invention include, in particular: polyethylene, polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN); polyacrylates such as polymethyl methacrylate (PMMA); polycarbonates; polyurethanes; polyamides; polyimides; fluorinated polymers such as fluoroesters such as ethylene tetrafluoroethylene (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), ethylene chlorotrifluoroethylene (ECTFE), fluorinated ethylene-propylene copolymers (FEP); photocrosslinkable and / or photopolymerizable resins, such as thiolene, polyurethane, urethane-acrylate, polyester-acrylate resins and polythiourethanes.

[0083] The substrate is preferably a sheet of glass or glass-ceramic.

[0084] The substrate is preferably transparent, colorless (in which case it is clear or extra-clear glass) or colored, for example blue, gray or bronze. The glass is preferably of the soda-lime-silica type, but it can also be borosilicate or alumino-borosilicate glass.

[0085] The substrate advantageously has at least one dimension greater than or equal to 1 m, or even 2 m and even 3 m. The thickness of the substrate generally varies between 0.5 mm and 19 mm, preferably between 0.7 and 9 mm, in particular between 2 and 8 mm. The substrate can be flat or curved.

[0086] In double glazing (DGU), by using a second substrate (counter-glass) with a low iron content, with the same stack, the solar factor can be slightly increased. Similarly, with an extra-clear glass substrate, the solar factor is increased even more.

[0087] The invention also relates to multiple glazing, in particular laminated glazing, or double glazing or triple glazing, comprising at least two transparent substrates, at least one of which is according to the description above.

[0088] In multiple glazing, the faces are counted from the outside of the building to the inside of the building. In double glazing, faces 2 and 3 are on the inside of the double glazing.

[0089] Preferably, the multiple glazing has, in a 3 / 12 / 3 configuration; with the interlayer filled with a mixture of 90% argon and 10% air and the layer on face 3, a solar factor (SHGC) greater than 0.65, preferably greater than 0.70, and more preferably greater than 0.72.

[0090] In this same configuration, the glazing preferably has a Ug coefficient of less than 0.36, preferably less than 0.34 and even more preferably less than 0.32.

[0091] In particular, at least one of the substrates is made of glass, in particular soda-lime-silica containing a reduced iron content.

[0092] These materials can also be integrated into glazing with specific functions, such as heated glazing.

[0093] The invention also relates to a method for obtaining a material comprising a transparent substrate coated with a stack of thin layers according to the invention.

[0094] The coated substrate of the invention is suitable in all applications requiring the use of a low-emissivity stack comprising silver layers for which a high solar factor, low emissivity and good light transmission are key parameters.

[0095] The following examples illustrate the invention without, however, limiting it. Examples I. Nature of the layers and coatings deposited

[0096] Several types of thin film stacks defined below are deposited on clear soda-lime glass substrates with a thickness of 2.9 mm, in a known manner, on a cathode sputtering line (magnetron process) in which the substrate passes under different targets.

[0097] For these examples, the deposition conditions of the layers deposited by sputtering (so-called “magnetron cathode sputtering”) are summarized in Table 1 below. [Table 1] Table 1 Targets used Deposit pressure Gas Hint If 3 N 4 Si:Al (92:8 wt. %) 2-15*10 -3< mbar Ar 47% - N 2 53% 1,98 SiZrAlN Si:Al:Zr (70:8:22% at.) 2 to 4.10 -3< mbar Ar 40-55% - N 2 45-60% 2,26 SnZnOx Sn:Zn (60:40% by weight) 1.5*10 -3< mbar Ar 40-60% - O2 40-60% 2,09 ZnO Zn:Al (98:2% by weight) 1.5*10 -3< mbar Ar 60% - O 2 40% 2,04 Ag Ag 5 to 8*10 -3< mbar Ar à 100 % - You You 3*10 -3< mbar Ar à 100 % - SiO 2 Si:Al (92:8 wt. %) 2-5*10 -3< mbar Ar 100% - O2 45-60% 1,50 TiO 2 TiOx 1.5.10-3 mbar Ar 88% - O2 12% 2,45 at.: atomic; pds: weight; Index: at 550 nm.

[0098] Tables 2 and 3 indicate for each coated substrate the physical thickness of the layers in the stack, expressed in nm (unless otherwise indicated). The first line corresponds to the layer furthest from the substrate, in contact with free air. [Table 2] Table 2 Comp. 1 Comp. 2 Comp.3 Protective layer TiO x 1 1 1 Low index layer SiO 2 - - - Intermediate index layer. SiN x - - - High index layer SiZrN x 41 45 44 ZnO 8 8 8 Blocking layer TiO x 1 1 1 Functional layer Ag 8 8 8 Wetting layer ZnO 5 5 5 Smoothing layer SnZnO - - 5 High index layer TiO x - 13 13 Intermediate index layer. SiZrN x 20 7 10 Low index layer SiN x 22 16 4 substrate SHGC (%) - 71,9 72,3 72,4 [Table 3] Table 3 Ex. 1 Ex. 2 Ex 3 Ex 4 Ex 5 Comp.6 Protective layer TiO x 1 1 1 1 1 1 Low index layer SiO 2 / 7 15 46 15 15 Intermediate index layer. SiN x 29 27 22 15 22 22 High index layer SiZrN x 14 14 14 14 14 14 ZnO 8 8 8 8 8 8 Blocking layer TiO x 1 1 1 1 1 1 Functional layer Ag 8 8 8 8 8 8 Wetting layer ZnO 5 5 5 5 5 5 Smoothing layer SnZnO 5 5 5 5 2 0 High index layer TiO x 13 13 13 13 13 13 Intermediate index layer. SiZrN x 14 14 14 14 14 10 Low index layer SiN x 4 4 4 4 4 12 substrate SHGC (%) - 72,7 72,8 72,9 73,6 72,7 72,5 Rsq (ohm / square) - 7,04 7,04 7,04 - 7,15 7,21

[0099] In the lower dielectric coating, the SiN x , SiZrN x , TiO x layers have respective indices of 1.98, 2.26 and 2.45, i.e. increasing.

[0100] In the upper dielectric coating, the SiZrN x , SiN x , SiO 2 layers have respective indices of 2.26, 1.98 and 1.50, i.e. decreasing. II. Configuration of double glazing

[0101] The coated substrates of the stack were assembled in double glazing, in a 3 / 12 / 3 configuration, with a second substrate (called counter-glass) made of clear soda-lime glass, placed on the exterior side of the building; the coated substrate being placed on the interior side of the building with the layer on face 3. The interlayer space is filled with a mixture of 90% argon and 10% air. III. Optical performance

[0102] The following characteristics were measured on the double-glazed configurations and are given in Table 2: the solar factor: SHGC (Solar Heat Gain Coefficient) according to the NFRI 200-2017 standard, the resistance per square (Rsq) (in Ω / square). This value is linearly related to the emissivity value.

[0103] The Ug coefficient is deduced from the emissivity.

[0104] An increase of 0.2 percentage points in solar factor constitutes a significant improvement.

[0105] Comparison of Comp.1 and Comp.2 glazings shows that the use in the lower dielectric coating of a sequence of at least 3 layers of increasing refractive index (Comp.2) vs 2 layers of increasing refractive index (Comp.1) allows an increase in the solar factor of 0.4 percentage points.

[0106] The use of a smoothing layer in the dielectric coating further improves the solar factor (comp.3 vs. comp.2).

[0107] The combined use of at least three layers with an increasing index gradient in the lower dielectric coating and at least two layers with a decreasing index gradient in the upper dielectric coating allows an increase in the solar factor of 0.8 percentage points (comp.1 vs. Inv.1).

[0108] The combined use of at least three layers with an increasing index gradient in the lower dielectric coating and at least 3 layers with a decreasing index gradient in the upper dielectric coating allows an increase in the solar factor of 0.9 to 1.7 percentage points (comp.1 vs. Inv.2, Inv.3 and Inv.4).

[0109] Finally, examples Inv.3, Inv.5 and Comp.6 highlight the influence of a SnZnO-based smoothing layer in the lower dielectric coating. Here again, we observe a gain in solar factor but above all a reduction in the resistance per square.

[0110] There fig.1 represents the relationship between the solar factor SHGC and the thermal insulation coefficient Ug for the different simulations according to the invention. The coefficient Ug varies from 0.22 to 0.31 Btu / hft 2< F when the solar factor SHGC varies from 0.720 to 0.757.

[0111] In the same double glazing configuration, with the stacking according to example 3 on face 3, if the clear soda-lime glass counterpane is replaced by low iron glass, the solar factor increases from 72.9 to 74.2, and if the counterpane is replaced by extra clear glass, the solar factor increases to 75.7.

[0112] In the same double glazing configuration, with the stacking according to example 3 on face 3, with the 90-10 Argon-air mixture, the Ug coefficient is 0.263. If we replace the mixture with: 100% air, the Ug coefficient increases to 0.311, 100% Argon, the Ug coefficient increases to 0.258, 100% Krypton, the Ug coefficient increases to 0.242, 100% Xenon, the Ug coefficient increases to 0.226.

[0113] It is therefore demonstrated that the Ug coefficient depends strongly on the composition of the gas filling the cavity of the double glazing.

Claims

1. A transparent substrate coated with a stack of thin layers comprising, starting from the substrate, a bottom dielectric coating, a silver-based functional metal layer and a top dielectric coating, each dielectric coating comprising several dielectric layers, characterized in that: - the bottom dielectric coating comprises, starting from the substrate: a series of at least three dielectric layers having increasing refractive indices, the index difference between each successive layer being at least 0.15, a smoothing layer and a wetting layer, preferably based on zinc oxide, - the bottom dielectric coating comprises, starting from the substrate: a zinc-oxide-based layer and a series of at least two layers having decreasing refractive indices, the index difference between each successive layer being at least 0.15.

2. The substrate according to claim 1, characterized in that the three dielectric layers having increasing refractive indices of the bottom dielectric coating each have a thickness of greater than 3 nm.

3. The substrate according to any one of the preceding claims, characterized in that the two dielectric layers having decreasing refractive indices of the bottom dielectric coating each have a thickness of greater than 3 nm.

4. The substrate according to any one of the preceding claims, characterized in that the smoothing layer is based on a mixed oxide comprising at least two metals chosen from tin Sn, zinc Zn, gallium Ga and indium In, preferably a mixed oxide layer based on Sn and Zn.

5. The substrate according to any one of the preceding claims, characterized in that the top dielectric coating comprises a succession of at least three layers of decreasing indices, each of a thickness greater than 5 nm, the index difference of which is greater than 0.15, or even greater than 0.20.

6. The substrate according to any one of the preceding claims, characterized in that the top dielectric coating comprises a layer with a refractive index of less than 1.70 and having a thickness of greater than 5 nm or 10 nm.

7. The substrate according to any one of the preceding claims, characterized in that the bottom dielectric coating comprises: - a dielectric layer having a refractive index lower than 2.20 chosen from the layers based on silicon nitride, - a dielectric layer having a refractive index of between 2.20 to 2.40 chosen from the zirconium-silicon-nitride-based layers, preferably located in contact with the layer of silicon nitride, - a dielectric layer having a refractive index greater than 2.40 chosen from layers based on oxide, preferably located in contact with the layer of zirconium silicon nitride, - a smoothing layer based on zinc tin oxide, preferably located in contact with the oxide-based layer, - a wetting layer based on zinc oxide, preferably located in contact with the zinc-tin-oxide-based layer.

8. The substrate according to any one of the preceding claims, characterized in that the bottom dielectric coating comprises: - a zinc-oxide-based layer, - a dielectric layer having a refractive index greater than 2.20, - a dielectric layer having a refractive index lower than 2.20, - potentially a dielectric layer having a refractive index lower than 1.70.

9. The substrate according to any one of the preceding claims, characterized in that the bottom dielectric coating comprises: - a zinc-oxide-based layer, - a dielectric layer having a refractive index greater than 2.20 chosen from zirconium-silicon-nitride-based layers, preferably located in contact with the zinc-oxide-based layer, - a dielectric layer having a refractive index lower than 2.20 chosen from the layers based on silicon nitride, preferably located in contact with the zirconium silicon nitride-based layer, - a dielectric layer having a refractive index lower than 1.70 chosen from the layers based on silicon oxide, preferably located in contact with the silicon nitride-based layer.

10. The substrate according to any one of the preceding claims, characterized in that the stack further includes a blocking layer deposited directly on the silver-based functional metal layer, the thickness of which is less than 5.0 nm, less than 4.0 nm, less than 3.0 nm, less than 2.5 nm, less than 2.0 nm, even more preferably less than 1.5 nm.

11. The substrate according to any one of the preceding claims, characterized in that the silver-based functional metal layer has a thickness between 5 and 20 nm, preferably between 6 and 10 nm, and still more preferably between 7 and 8.5 nm.

12. A multiple glazed unit including at least two transparent substrates, at least one of which is according to any one of the preceding claims.

13. The glazed unit according to the preceding claim, characterized in that it has, in a 3 / 12 / 3 configuration, with the interlayer space filled with a mixture 90% argon and 10% air and the layer on Face 3, a solar factor (SHGC) greater than 0.65, preferably greater than 0.70, and even more preferably greater than 0.72.

14. The glazed unit according to one of claims 13 and 14, characterized in that it has, in a 3 / 12 / 3 configuration, with the interlayer space filled with a mixture 90% argon and 10% air and the layer on Face 3, a coefficient Ug less than 0.36, preferably less than 0.34, and even more preferably less than 0.32.

15. The glazed unit according to any one of claims 13 to 15, characterized in that at least one of the substrates is made of glass, in particular soda-lime-silica, including a reduced iron content.