Transparent glass article for cold compartment and multiple glazing incorporating said article.

Abstract

Glass article comprising a glass substrate on which a heatable coating is deposited, said heatable coating comprising, from the surface of said substrate a first layer of dielectric material comprising silicon nitride, with a thickness of between 1 and 20 nm, a layer of a transparent electrically conductive oxide (TCO), with a thickness of between 1 nm and 40 nm, a second layer of dielectric material comprising silicon nitride, with a thickness of between 1 and 20 nm, a layer comprising a titanium oxide, a zirconium oxide or a zirconium and titanium oxide, with a thickness of between 1 nm and 15 nm.

Description

Title of the invention: Transparent glass article for cold compartment and multiple glazing incorporating said article.

[0001] The invention relates to a glass article comprising a glass substrate on which a heating coating is deposited and intended to form part of a multiple glazing unit used in particular as anti-condensation glazing, in particular in a transparent refrigerator or freezer door, as well as its production.

[0002] Heated (or heatable) windows, windows and doors using substantially transparent coatings are known per se. Often, the heating coating contains an electrically conductive layer, such as silver layers or a pyrolytic layer of the fluorine-doped tin oxide type, on which the Joule effect heating is based (functional layer), as well as other dielectric layers which act as anti-reflective layers to preserve good light transmission, or even barrier layers to protect the functional layer from external aggressions such as the diffusion of alkali ions from the glass substrate or oxidation by oxygen in the air during heat treatment in particular.The disadvantage of coatings containing silver is also their high sensitivity to corrosion, which means that these coatings can only be used on surfaces of multiple glazing (multiple or laminated glazing) which have no contact with the surrounding atmosphere, for example on face 2 or 3 of multiple glazing, the faces being conventionally numbered from the outside to the inside of the equipment fitted with said multiple glazing.

[0003] Transparent Conductive Oxide (TCO) heating coatings are also known as a less corrosion-sensitive alternative. These can even be used on the exposed surfaces of the windows to the atmosphere. Due to the lower conductivity of TCOs compared to silver, it has long been thought that TCO layers, particularly ITO (Indium Tin Oxide) layers, had to be relatively thick to achieve adequate thermal efficiency. However, this significantly increases the production costs of glass windows. TCO-based heating coatings are known, for example, from WO2012168628A1, WO2007018951A1, US Pat. No. 5,852,284A, and US2004214010A1.

[0004] For example, WO2015091016 discloses a vehicle window having an electrically heatable coating. The coating preferably contains silver layers, but transparent conductive oxides are also mentioned as an alternative. The window is preferably a windshield, i.e., a composite window, wherein the heating coating is arranged on an interior surface, where it is protected from the surrounding atmosphere.

[0005] Publication WO2007018951A1 discloses a glass with a TCO coating. A silicon nitride barrier layer is disposed above the TCO layer, which is intended to protect the TCO layer against oxidation during a tempering process. The appropriate or necessary thickness of the barrier layer is not disclosed.

[0006] Patent application WO2018 / 192727 describes a heatable coating whose TCO functional layer is much thinner, in the order of 1 to 40 nm. Through this publication, the applicant company has demonstrated that a very thin conductive layer of TCO, in particular 1TTO (Indium Tin Oxide) allows a sufficient heating effect despite this very low thickness, even using usual supply voltages. Production costs are considerably reduced. Thanks to such a heating effect of its coating, the window equipped with the described coating can sufficiently heat its physical environment and can be freed from condensation or frost, which creates a particularly beneficial effect in refrigeration applications.

[0007] During the stages of manufacturing multiple glazings incorporating such a coating on face 2 of said glazing, the applicant company has however observed that due to this very low thickness of the functional layer, problems of homogeneity of the heating thereof result in increased variability of the total resistance of the coating after toughening, with certain samples sometimes even falling outside the required specification.

[0008] The object of the present invention is first of all to resolve this problem of inhomogeneity of heating of these glazings, having a very thin heating layer of TCO, that is to say of the order of 1 nanometer to 40 nanometers.

[0009] The object of the present invention is achieved by implementing a glass article comprising a glass substrate on which a heatable coating is deposited, said heatable coating comprising at least the following succession of layers, from the surface of said substrate:

[0010] - a first layer of dielectric material comprising silicon nitride, with a thickness between 1 and 20 nm, preferably between 1 and 10 nm,

[0011] - a layer of an electrically conductive transparent oxide (TCO), of thickness between 1 nm and 40 nm, preferably between 5 and 35 nm,

[0012] - a second layer of dielectric material comprising silicon nitride, with a thickness of between 1 and 20 nm, preferably between 1 and 15 nm, preferably between 5 and 15 nm,

[0013] - a layer comprising a titanium oxide, a zirconium oxide or a zirconium oxide zirconium and titanium, with a thickness between 1 nm and 15 nm, preferably between 1 and 10 nm, or more preferably between 1 and 5 nm.

[0014] According to certain preferred embodiments of the present invention:

[0015] - The electrically conductive layer comprises and preferably is based on a indium tin oxide.

[0016] - The electrically conductive layer has a thickness of 8 nm to 15 nm.

[0017] - The electrically conductive layer has a thickness of 15 nm to 30 nm.

[0018] - Said first dielectric layer consists essentially of nitride of silicon, optionally doped with an element chosen from Al, Zr, B, preferably Al, said layer possibly being partially oxidized under the effect of heat treatment.

[0019] - Said second dielectric layer consists essentially of nitride of silicon, optionally doped with an element chosen from Al, Zr, B, preferably Al, said layer possibly being partially oxidized under the effect of heat treatment.

[0020] - The glass article further comprises at least two current supply strips arranged above said heatable coating and in contact with it.

[0021] - Said at least two current supply strips are arranged in two opposite ends of said article, preferably in the direction of its greatest length.

[0022] - Said coating has a resistance per square of between 50 ohms per square and 400 ohms per square.

[0023] - The substrate is a thermally prestressed glass pane, before or after the deposit of said coating.

[0024] The invention also relates to multiple glazing, comprising a glass article according to one of the preceding claims and at least one other glass substrate separated from said article by a gas layer or a thermoplastic sheet, in particular PVB, said coating being in contact with the gas layer or the thermoplastic sheet.

[0025] According to possible and preferred modes of such multiple glazing:

[0026] - Said coating is deposited on face 2 or face 3 of said glazing, preferably said coating is deposited on face 2 of said glazing.

[0027] - The glazing comprises, in addition to a low-emissivity stack, preferably deposited on the face 3 of said glazing.

[0028] - The glazing is double glazing, preferably in which said coating is deposited on face 2 of said glazing and preferably a low-emissivity stack is deposited on face 3 of said glazing.

[0029] - The glazing is triple glazing, in which said coating is deposited on face 2 or face 5 of said glazing, preferably on face 2 of said glazing.

[0030] - Said coating is deposited on face 2 of said triple glazing and said glazing comprises a low-emissivity coating, said low-emissivity coating being arranged on face 3 and / or on face 5, preferably on face 3 or face 5 of said glazing.

[0031] - Said coating is deposited on face 5 of said triple glazing and said glazing comprises a low-emissivity coating, said low-emissivity coating being arranged on face 2 and / or on face 4, preferably on face 2 of said glazing.

[0032] - Said low-emissive stack(s) comprises at least one layer in silver and layers of dielectric materials.

[0033] - Said low-emissivity stack(s) comprises an ITO layer and layers of dielectric materials.

[0034] A glass article according to the present invention and as described above can advantageously be used in the manufacture of any refrigerating element and in particular as a front element of a refrigerator door or a freezer door. Thanks to the heating effect of the coating, the article whose uncovered face is in contact with the external environment, allows heating of its physical environment and prevents condensation on the external side, which creates a particularly beneficial effect in these applications. The coating according to the invention is distinguished in particular by its very thin TCO conductive layer, the thickness of which is much thinner than those usually used in the art.The inventors have discovered that a homogeneous heating effect over the entire surface of the glass article can be obtained with the coating described above, even when using the usual supply voltages used in different countries, for example between 40 and 250 volts, in particular between 100 and 240 volts. Production costs are considerably reduced by the use of reduced materials, in particular the TCO layer, preferably TITO.

[0035] The glass article according to the invention preferably has a transmission in the visible spectral range of at least 40%. By "visible spectral range" is meant the spectral range from 380 nm to 780 nm. The transmission factor is preferably determined according to standard EN 410 (2011).

[0036] The coating according to the invention has a resistance per square of 50 ohms / square to 400 ohms / square, preferably of 50 ohms / square to 300 ohms / square. Such a resistance can be obtained with the thin TCO layers according to the invention and makes it possible to obtain an appropriate thermal efficiency with usual operating voltages described above.

[0037] The substrate is generally made of flat glass. The substrate contains, in a preferred embodiment, soda-lime glass but may, however, in principle, also contain other types of glass, for example, borosilicate glass or quartz glass. The substrate preferably has a thickness of 1 mm to 20 mm, typically 2 mm to 6 mm. The substrate may be flat or even curved. In a particularly advantageous embodiment, the substrate is a pane of thermally prestressed glass.

[0038] The coating is according to the invention advantageously arranged on an unexposed surface of the substrate, that is to say it is present on the face of the substrate which will be turned towards the inside of the final glazing, which may be of the multiple glazing type (also called insulating glazing) or laminated. Thus the glass article according to the invention is part, in operation, of an assembly comprising several sheets (or substrates) of glass which comprises at least one other glass substrate in addition to that of the article according to the invention.

[0039] By multiple glazing is meant a glazing in which a succession of glass sheets or substrates are spaced by gas blade(s). In such multiple glazings, the article according to the invention is connected to one or more other panes by means of a peripheral spacer often called a spacer in the field, so that an intermediate space filled with gas such as air or more rarely argon or Krypton (or even more rarely a vacuum) is created between the panes.

[0040] Laminated glazing means glazing in which a succession of glass sheets or substrates are bonded by a thermoplastic interlayer. In laminated glazing, the article according to the invention is laminated with one or more other glass sheets by means of a thermoplastic intermediate layer, in particular made of PVB (polyvinyl butyral).

[0041] The coating according to the invention as described above is typically applied over the entire surface of the substrate, possibly with the exception of a circumferential edge region and / or another locally limited region which may serve, for example, for data transmission. The coating may also be structured by uncoated lines through which the current flow can be suitably directed. The coated portion of the substrate surface preferably amounts to at least 90%.

[0042] When a layer "comprises" a material, this includes, in the context of the invention, the case in which the layer consists essentially of or even consists of said material, which is, in principle, also preferable. The compounds described in the context of the present invention, in particular the oxides, the nitrides, can, in principle, be stoichiometric, substoichiometric or superstoichiometric, even if the stoichiometric molecular formulas are often cited for better understanding.

[0043] In particular, the layers comprising silicon nitride predominantly comprise silicon and nitrogen as main constituents. In particular, silicon and nitrogen together represent more than 50%, more than 60% or even more than 70% or even more than 80% of the atoms present in a layer, or even more than 90% of the atoms present in a layer. Preferably, said layers comprising silicon nitride are essentially made up of silicon and nitrogen and optionally of at least one element chosen from aluminum, boron or zirconium, preferably aluminum, apart from unavoidable impurities. Said layers comprising silicon nitride are in principle free of oxygen apart from unavoidable impurities after their deposition, for example they comprise less than 5 mol% of elemental oxygen, in particular less than 1 mol% of elemental oxygen.However, the layers comprising silicon nitride may ultimately comprise a much larger quantity of oxygen, in particular after heat treatment in air of the glass articles according to the invention, such as quenching which will often lead to partial oxidation of said layers. Preferably, said layers have an N / Si ratio greater than 1.25 and are stoichiometric layers. By "stoichiometric", it is meant that the N / Si ratio is equal to 1.33 for these silicon-based nitride layers, corresponding to the Si3N4 compound. By "substantially stoichiometric", it is meant, for example, that the value measured for this Si3N4 compound differs by less than 5% from this theoretical value.Indeed, it should be noted that the layers comprising silicon nitride according to the invention are obtained by a magnetron-assisted sputtering process from a metallic silicon target which may comprise a minor amount of another element such as aluminium and / or zirconium, for example around 8 atomic% of aluminium, in a reactive atmosphere containing nitrogen. In such a case, the N / Si ratio may vary substantially from the theoretical value 1.33 (= 4 / 3) (corresponding to the defined compound Si3N4) taking into account the stoichiometries of the defined compounds AIN and Si3N4.For example, for a layer of silicon nitride comprising a little aluminum, obtained with the target described previously (8% aluminum), the N / Si ratio of the stoichiometric layer theoretically corresponds to a formulation: 92% (SiNl,33) / 8% (AIN) or an N / Si ratio of 1.41 (based on a theoretical formula 0.92 SiNl,33 0.08 AIN, or a ratio: N / Si = [(0.92x1.33+0.08x1 ) / (0.92)] = 1.41).

[0044] The values indicated for the refractive indices are measured at a wavelength of 550 nm.

[0045] The electrically conductive layer contains, according to the invention, at least one transparent and electrically conductive oxide (TCO) and has a thickness of 1 nm to 40 nm, preferably 5 nm to 35 nm. Even with these low thicknesses, an effect of Adequate heating can be achieved with an appropriate voltage. The conductive layer most preferably contains indium tin oxide (ITO), which has proven particularly useful, especially due to its low specific resistance. Furthermore, by applying the principles of the invention, a very uniform heating effect can be ensured with such a material.

[0046] Conventionally, the composition of the ITO layers is of the order of 90% by weight of In2O3 and 10% by weight of SnO2, it being understood that the present invention is of course not limited to such proportions and that these percentages can of course fluctuate around this composition, for example in a range between 70 and 95% by weight of In2O3 and between 30 and 5% of SnO2.

[0047] However, the conductive layer may also contain, for example, mixed indium zinc oxide (IZO), gallium-doped tin oxide (GZO), fluorine-doped tin oxide (SnO2:F) or antimony-doped tin oxide (SnO2:Sb). The refractive index of the transparent and electrically conductive oxide is preferably between 1.7 and 2.3.

[0048] According to the invention, the coating comprises, under the electrically conductive TCO layer, a first layer of a dielectric material which allows blocking against the diffusion of alkalis, in particular during a heat treatment of the article. The blocking layer reduces or prevents the diffusion of alkali ions from the glass substrate into the layer system. Alkali ions can have a negative impact on the properties of the coating. The blocking layer more particularly comprises a silicon nitride. As indicated previously, the silicon nitride can be doped and, in a preferred development, is doped with aluminium, zirconium or boron. The amount of Al, Zr or B replacing the silicon is usually of the order of 8 atomic% but can vary around this value, without departing from the scope of the present invention.The thickness of this first layer of alkali-blocking dielectric material is preferably between 1 nm and 50 nm, particularly preferably between 2 nm and 20 nm, in particular between 3 and 10 nm.

[0049] It is known that the oxygen content of the electrically conductive layer, in particular TITO, has a substantial influence on its properties, in particular its transparency and its conductivity. The production of the glass article according to the invention generally comprises a heat treatment during which oxygen can diffuse towards the conductive layer and oxidize it. According to the present application, a barrier layer of a dielectric material, comprising silicon nitride, makes it possible to limit the diffusion of oxygen and the degradation of the electrical properties of the conductive layer. According to the present invention, and as for the first dielectric layer, the silicon nitride can be doped with different elements, and in a preferred development, it is doped with aluminum, zirconium or boron, generally in the proportions previously described.

[0050] For the purposes of the present invention, as indicated above, in particular as a result of a heat treatment after application of the coating according to the invention, the silicon nitride may be partially oxidized. A barrier layer deposited in the form of silicon nitride may therefore contain a significant portion of oxygen after the heat treatment, the oxygen content being able to be up to 35 atomic%.

[0051] The thickness of the barrier layer or second dielectric layer is preferably 1 nm to 20 nm. If the barrier layer is thinner, it has too little or no barrier effect. If the barrier layer is too thick, it may then be problematic to electrically contact the underlying conductive layer, for example by means of a current supply strip (or busbar in English) applied to the barrier layer. The thickness of the barrier layer is preferably 2 nm to 15 nm. Thus, the oxygen content of the conductive layer is advantageously regulated.

[0052] In a possible but not preferred embodiment, the heatable coating according to the invention may contain other layers of dielectric materials than the two previously described, in particular to modulate the optics of the electrically conductive layer.

[0053] These optical adaptation layers are intended to improve the optical properties of the glazing. Thus, they can be introduced to reduce the degree of reflection and thus increase the transparency of the glazing. They can also be incorporated into the coating to ensure a neutral color impression. The optical adaptation layer and / or the antireflection layer have a refractive index lower than that of the electrically conductive layer, preferably a refractive index of 1.3 to 1.8. The optical adaptation layer and / or the antireflection layer preferably contain an oxide, preferably silicon oxide. The silicon oxide can be doped and is preferably doped with aluminum, boron or zirconium.

[0054] These optical adaptation layers can be arranged either above or below the conductive layer in the coating, and preferably are arranged in contact with the layers comprising silicon nitride, said layers comprising silicon nitride being kept in contact with the conductive TCO layer. In other words, the optical adaptation layers, often made of oxides, are not in contact with the TCO layer.

[0055] According to a preferred embodiment according to the invention, however, the coating according to the invention is constituted by the succession:

[0056] - of a first layer of dielectric material comprising silicon nitride,

[0057] - of an electrically conductive transparent oxide (TCO),

[0058] - a second layer of dielectric material comprising silicon nitride,

[0059] - a layer of a titanium oxide, a zirconium oxide or an oxide of zirconium and titanium,

[0060] without the presence of intermediate layer(s), that is to say that the successive layers are in direct contact with each other and that the coating does not contain other layers.

[0061] The coating according to the invention is thus completed in the outermost layer, that is to say the furthest from the surface of the substrate, by a layer comprising a titanium oxide, a zirconium oxide or a zirconium and titanium oxide. Said layer of zirconium and titanium oxide may contain between 1 and 99% by weight of titanium oxide and between 99% and 1% of zirconium oxide. Advantageously, said layer of zirconium and titanium oxide may contain between 70% and 80% by weight of titanium oxide and between 30% and 20% of zirconium oxide. The thickness of this layer is between 1 and 15 nm and advantageously between 2 and 10 nm. It was surprisingly discovered that the presence of this additional layer made it possible to guarantee the homogeneity of heating on the surface of the glazing, and in particular to limit the variability of the total resistance of the stack after tempering on a sample of a multitude of glazings thus formed.

[0062] A layer comprising a titanium oxide, a zirconium oxide or a zirconium and titanium oxide comprises said oxides as main constituents. Said Ti and / or Zr atoms represent more than 50%, more than 60% or even more than 70% or even more than 80% of the atoms present in a layer apart from oxygen, or even more than 90% or even more than 95% of the atoms present in a layer apart from oxygen. Preferably, said layers comprising a titanium oxide, a zirconium oxide or a zirconium and titanium oxide are essentially constituted by said oxides.

[0063] For its operation, the coating is brought into contact with current supply bars (or busbars in English) which can be connected to the poles of a voltage source in order to introduce current into said coating over the entire width of the window or at least a large part of the width of the window and thus heat it by the Joule effect.

[0064] The bars are preferably made in the form of printed and baked conductors which contain at least one metal, preferably silver. The electrical conductivity is preferably achieved by means of metal particles contained in said bars, and more particularly by means of silver particles. The metal particles may be located in an organic and / or inorganic matrix such as pastes or inks, preferably in the form of screen printing paste baked with glass frits. The layer thickness of the printed bus bars is preferably between 5 μm and 40 μm, particularly preferably between 10 μm and 20 μm. Printed busbars with these thicknesses are technically simple to produce and have an advantageous current-carrying capacity. In another possible embodiment, the current-carrying bars are implemented in the form of strips of an electrically conductive foil, in particular a metal foil, for example copper foil or aluminum foil. The foil strips can be laid or glued or welded. The thickness of the foil is preferably between 30 μm and 200 μm.

[0065] In operation, the glass article included in a glazing according to the invention is connected to a voltage source preferably having a voltage of 40 V to 250 V, for example 110 V in the USA and in many South American countries. When the glazing operates with these voltages, good thermal efficiencies are obtained, sufficient for the glazing to advantageously be quickly freed from condensation or to prevent it.

[0066] In a first preferred embodiment, the voltage is between 210 V and 250 V, for example between 220 V and 230 V. The glazing according to the invention can then operate with the standard network voltage, which is particularly suited to a heating power allowing the glazing to be quickly freed from condensation on the outside.

[0067] In a second preferred embodiment, the voltage is of the order of 110 to 120V, corresponding to the voltage applied to the mains sockets of countries such as the USA, Mexico or other Latin American countries.

[0068] The invention also comprises a method of producing a glass article having a heatable coating, comprising the following steps:

[0069] a) on a surface of a glass substrate, a coating comprising successively at least the following layers is deposited by vacuum magnetron deposition:

[0070] - a first layer of dielectric material comprising silicon nitride,

[0071] - an electrically conductive transparent oxide (TCO), in particular TITO,

[0072] - a second layer of dielectric material comprising silicon nitride,

[0073] - a layer of a titanium oxide, a zirconium oxide or an oxide of zirconium and titanium,

[0074] b) a current supply strip is deposited on said coating,

[0075] c) a heat treatment such as quenching is carried out to obtain a thermal prestressing of the glass substrate.

[0076] During this step c), the substrate is heated to a temperature of the order of 650 to 750°C and then subjected to an air flow which cools it rapidly. Compressive stresses form on the surface of the glass and tensile stresses at the core of the glass. The characteristic distribution of the stresses increases the resistance to breakage of the glass sheets. A bending process may also precede prestressing.

[0077] According to an alternative embodiment, the current supply bars are installed after the heat treatment step (reversal of the preceding steps b) and c).

[0078] However, the deposition of the conductive bars is preferably carried out before the heat treatment, so that the baking of the printing paste can be carried out during the heat treatment and does not need to be carried out as a separate step.

[0079] The current inlet strips are preferably printed, particularly preferably by screen printing, in the form of a paste containing silver with glass frits, or laid or glued or welded like strips of a conductive foil.

[0080] Multiple glazing can then be obtained according to the invention by sealing with another substrate and by means of a thermoformable spacer, as described previously and in the remainder of this description.

[0081] The individual layers of the heating coating are deposited by methods known per se, preferably by magnetron-assisted sputtering. This method is particularly advantageous in terms of simple, rapid, economical and uniform coating of the substrate. The sputtering is carried out in a protective gas atmosphere, for example argon, or in a reactive gas atmosphere, for example by the addition of oxygen or nitrogen. However, the layers can also be deposited by other methods known to those skilled in the art, for example by vapor deposition or chemical vapor deposition (CVD), atomic layer deposition (ALD), plasma-enhanced chemical vapor deposition (PECVD), or by wet chemical methods.

[0082] The invention also comprises the use of a glass substrate according to the invention having an operating voltage of 40 V to 250 V, preferably as a component of a refrigerator door. The operating voltage is preferably 110 V to 120 V, or 210 V to 250 V, for example about 220 V or 230 V. The article according to the invention is usable as part of a multiple glazing unit with an insulating function, in which it is connected to at least one other glass substrate by a peripheral, preferably circumferential, spacer or spacer, so that an intermediate space capable of being filled with gas is formed between the panes.

[0083] Preferably, this other substrate is itself provided, on its face facing inwards (face 3 of the multiple glazing), with a so-called low-emissive (or low-e in English) stack as described below. Such a stack advantageously makes it possible to reflect the infrared radiation from the heating coating towards the outside and not to heat the refrigerated interior space.

[0084] By low-emissivity coating, it is understood within the meaning of the present description a coating whose normal emissivity, as measured when it is deposited on clear glass and according to standard ISO10292 annex A (1994), is less than 0.2, preferably less than 0.1 or even less than 0.05.

[0085] Such stacks are well known and in particular most often (but not exclusively) comprise a combination of layers based on precious metals, in particular, based on silver and dielectric materials often called interference layers. In a known manner, these stacks are made up of a succession of layers of dielectric materials such as oxides and / or nitrides and metal layers including silver-based layers whose so-called "low emissive" properties make it possible to selectively reflect infrared and to let through the majority of the visible light of the solar spectrum (with a wavelength between 380 and 780 nm) and preferably more than 70%, or even more than 80% of the visible light, in particular by minimizing light reflection by means of said interference layers or combination(s) of interference layers.

[0086] The low-e stacks according to the invention are in particular selected in such a way that their resistance per square is less than 3.5 Ohms per square, preferably still less than 2.0 Ohms per square, or even less than 1.5 Ohms per square. The resistance per square can for example be measured using a device of the SRM-14T type from Nagy Mess-systems.

[0087] Such stacks can comprise up to several dozen layers whose thickness is of the order of 1 to 30 nm and are currently deposited by so-called cathode sputtering techniques, often assisted by magnetron. The preferred low-emissivity stacks according to the invention preferably comprise one or two silver-based layers, although it is of course possible to use stacks comprising three or even four silver-based layers.

[0088] Examples of low-emissive stacks comprising one or two layers of silver are notably described in publications FR2940272A1, EP1993965B1, EP1656328B1, EP718250, EP847965, or even WO03 / 01105.

[0089] Examples of low-emissive stacks comprising three or four layers of silver are notably described in publications WO2005 / 051858A1, WO2013 / 104439 or WO2013 / 107983 cited previously.

[0090] Without departing from the scope of the invention, the multiple glazing may be double glazing (2 glass substrates) or triple glazing (3 glass substrates).

[0091] In the following, the invention is explained in detail with reference to drawings and to possible but non-limiting embodiments of the present invention. The drawings are a schematic representation and are not to scale. The drawings do not limit the invention in any way.

[0092] [Fig.l] is a cross-section of an embodiment of a glass substrate according to the invention comprising a heating coating,

[0093] [Fig.2] is a cross-section of a double glazing unit according to the present invention.

[0094] [Fig.3] is a cross-section of a triple glazing unit according to the present invention.

[0095] [Fig.4] is a top view of a glass article according to the invention equipped with a heating coating according to the invention used to produce the following examples.

[0096] Figures 5 to 8 are graphs showing the electrical resistance measurements of the comparative examples and according to the invention, of double glazing and triple glazing according to the configurations described in Figures 2 and 3 respectively. Brief description of the drawings

[0097] [Fig.l] represents a cross-section of an embodiment of a glass article according to the invention comprising a glass substrate 1, a heating coating 2 and current supply bars 3. The substrate 1 is, for example, a soda-lime glass sheet and has a thickness of 3 to 4 mm. The heatable coating 2 consists of 4 successive layers starting from the surface of the substrate, including:

[0098] - a first layer 4 based on silicon nitride, with a thickness of between 1 and 20 nm,

[0099] - a layer 5 of an electrically conductive transparent oxide (TCO), in particular ITO, with a thickness between 1 nm and 40 nm,

[0100] - a second layer 6 based on silicon nitride with a thickness of between 1 and 20 nm,

[0101] - a layer 7 comprising a titanium oxide, a zirconium oxide or an oxide zirconium and titanium, with a thickness between 1 nm and 15 nm, preferably between 1 and 10 nm, or even between 1 and 5 nm, which is the last layer of the coating.

[0102] Above the coating and in contact with it, two current supply bars 3 are arranged on either side of the substrate as illustrated in [Fig.4]. The bars 3 are arranged along two opposite ends of said article, preferably in the direction of its greatest length.

[0103] [Fig.4] shows the position of the bars 3, in a top view of the glass article according to the invention.

[0104] In [Fig.2], a schematic view of a double glazing unit 10 is shown. comprising the glass article of figures 1 and 4 assembled with a second glass substrate 11 by means of a spacer 12 made of thermoformable material to delimit between the two glass sheets a cavity 13 comprising a gas which can conventionally be air but also a rare gas such as argon or krypton for better insulation. This second glass substrate is provided with a low-emissivity stack 14 of the type described above and preferably comprising at least one layer of silver surrounded by dielectric layers. The heatable coating 2 is connected to a device for energizing the current supply bars 3 (not shown in the figures), comprising connectors welded to the bars 3 and to electric cables (not shown) themselves connected in operation to a voltage generator, in particular a simple mains socket, for the passage of electric current through the heatable coating 2.

[0105] In such multiple glazing according to the invention, the heatable coating 2 is advantageously arranged on the face 2 of the multiple glazing, the faces being conventionally numbered from the outside to the inside of the glazing (in the case of a refrigerating door the inside being the body of the refrigerating element).

[0106] Similarly, the low-emissivity stack is arranged on face 3 of the multiple glazing.

[0107] Thus, according to the present invention, the heatable coating 2 and the low-emissivity stack 3 are turned towards the inside of the multiple glazing, that is to say in contact with the cavity 13 thereof.

[0108] When the coating 2 is heated, it increases the temperature of the outer surface of the glass substrate 1, thus preventing condensation on the outer surface of the refrigerator door. Similarly, the combination of the heating coating on face 2 of the glazing and the low-emissivity stack 14 on face 3 of the glazing prevents condensation. The presence of a low-emissivity stack keeps the outer face less cold, which results in lower energy consumption of the refrigerating element. According to the invention, it becomes possible to significantly reduce the heating power on the ITO layer to go above the dew point of the outer surface and thus prevent condensation.

[0109] Finally, the coatings according to the invention have high transmittance and low reflectivity, so that they do not critically reduce vision through the glass. Such a configuration is particularly well suited to the use of such glazing as a transparent door of a refrigerator, i.e. of a compartment whose interior space is maintained at a temperature of up to values of the order of -5°C.

[0110] However, it would not be outside the scope of the present invention if the heating coating 2 were arranged on face 3 of the double glazing, in particular to prevent condensation this time on the inner glass of the double glazing. In such a configuration, the low-emissivity coating 14 is advantageously deposited on face 2 to limit the energy consumption of the cooling element.

[0111] In the case where the glazing according to the invention is used as a door of a freezing device, that is to say for which the internal temperature is lower than -15°, or even lower than -20°C, the triple glazing configuration presented in [Fig.3] attached is suitable, although a double-glazed configuration as described above could also be used without departing from the scope of the invention. Triple glazing, however, appears to be less energy-consuming and remains a more economical solution in this case.

[0112] In such triple glazing, a third glass sheet 15 is used, which is connected to the other two by means of a second spacer 16 to delimit between the two glass sheets a second cavity 17 comprising a gas which can conventionally be air but also a rare gas such as argon or krypton for better insulation. This third glass substrate is provided with another low-emissivity stack 18 of the type described previously, or even identical to this one, and preferably comprising at least one layer of silver surrounded by dielectric layers, this stack being arranged on face 5 of the triple glazing.

[0113] However, it would not be outside the scope of the present invention if the heating coating were arranged on face 5 of the triple glazing, in particular to prevent condensation this time on the inner glass of the triple glazing.

[0114] In such a configuration, the low-emissive coating 18 is advantageously deposited on face 2, or face 4 or on faces 2 and on face 4 to limit the energy consumption of the refrigerating element.

[0115] According to the invention, for the two embodiments previously described (double or triple glazing), depending on the internal temperature of the cold compartment and the external conditions (in particular the external temperature and the external humidity level), it is possible to program the operation of the heating coating so that it is always above the dew point at the level of the external glass surface of the glazing (face 1 of the double glazing or triple glazing) and thus avoid the formation of condensation on the external face thereof.

[0116] The following examples, purely illustrative and non-limiting of the present invention, allow a better understanding of its advantages. A. Double glazing configuration#

[0117] Initially, two series of glass articles are synthesized using conventional and well-known vacuum magnetron deposition techniques.

[0118] According to a first series of reference articles, a stack comprising successively, starting from the glass surface, is deposited by magnetron-assisted cathodic sputtering on a clear glass substrate marketed by the applicant company under the reference Planilux, 3.15 mm thick and with dimensions L 684 mm x H 822 mm: - a layer based on silicon nitride with a thickness of 5 nanometers - a transparent conductive layer of ITO with a thickness of 10 nanometers - a layer based on silicon nitride with a thickness of 10 nanometers.

[0119] According to a second series of articles according to the invention, a stack according to the invention is deposited on the same glass substrate and successively comprising, from the glass surface: - a layer based on silicon nitride with a thickness of 5 nanometers - a transparent conductive layer of ITO with a thickness of 10 nanometers - a 10 nanometer thick silicon nitride layer - a layer of titanium and zirconium oxide 2 nanometers thick.

[0120] Said layer of titanium and zirconium oxide is obtained by sputtering a ceramic target comprising between 70% and 80% by mass of TiO2 and between 20% and 30% by mass of ZrO2, under an argon / oxygen atmosphere, according to the usual magnetron-assisted cathode sputtering techniques, perfectly known to those skilled in the art.

[0121] In both coating configurations, the measured resistance per square is of the order of 250 Ohms per square.

[0122] For all the articles thus obtained, the glasses are edged, edged and washed and current supply strips are manually screen-printed by depositing an Ag paste in a glass frit (88% silver by weight) marketed by the Ferro company, according to the diagram illustrated in [Fig.4]. The dimensions of the bars 3 are as follows: - width of the bars: 654 mm - distance between the bars: 734 mm

[0123] The article is then heated to 715°C and then quenched according to current techniques. Connectors are then soldered to each of the strips 3 and electrically connected via electrical cables to a multimeter to measure their total resistance.

[0124] The glass articles thus obtained are then assembled into double glazing with another glass substrate comprising a low-emissivity stack incorporating 1 silver layer as described in example 1 of publication FR2940272A1, according to the principles given previously and in accordance with [Fig.2] attached. The heating coating is arranged on face 2 and the low-emissivity stack is arranged on face 3 of the double glazing.

[0125] For each of the configurations obtained, the total resistance of the coating 2 is measured for the two series of glazing (according to the invention and reference).

[0126] Considering the dimensions of the current supply bars, the distance between them and the dimensions of the glazing, a resistance of the order of 280 Ohms is expected, with a tolerance margin of plus or minus 20 Ohms.

[0127] Figures 5 and 6 show the resistances obtained for the coatings for all the glazings measured (one point corresponding to one sample).

[0128] [Fig.5] corresponds to the glazing of the first series of reference articles and the [Fig.6] corresponds to the glazing of the second series of articles according to the invention.

[0129] It can be seen that the glazings according to the invention exhibit less variability in the total resistance of the stack after toughening.

[0130] Furthermore, some samples of the reference series are sometimes even outside the required specification as can be seen in [Fig.5] while all the samples according to the invention comply with said specification (see [Fig.6]).

[0131] Additional tests in real operation have shown that the application of such glazing as a transparent refrigerator door effectively prevents the appearance of condensation on the external surface of the glazing and perfect visibility through it in cold conditions of the order of -4°C, even if a relatively low voltage is applied to the heatable coating, in particular of the order of 110V. A. Triple glazing configuration#

[0132] According to a second series of experiments, glass articles configured for use in triple glazing suitable for use as a transparent door are manufactured.

[0133] According to a first series of reference articles, a stack comprising successively: - a layer based on silicon nitride with a thickness of 5 nanometers - a transparent conductive ITO layer 27 nanometers thick - a layer based on silicon nitride with a thickness of 10 nanometers.

[0134] According to a second series of articles according to the invention, a stack according to the invention is deposited on the same glass substrate and successively comprising: - a layer based on silicon nitride with a thickness of 5 nanometers - a transparent conductive ITO layer 27 nanometers thick - a 10 nanometer thick silicon nitride layer - a layer of titanium oxide 2 nanometers thick.

[0135] In both coating configurations, the measured resistance per square is of the order of 70 Ohms per square.

[0136] For all the articles thus obtained, the glasses are edged, edged and washed and current supply strips are manually screen-printed by depositing an Ag paste in a glass frit (88% silver by weight) marketed by the Ferro company, according to the diagram illustrated in [Fig.4]. The dimensions of the bars 3 are as follows: - width of the bars: 648 mm - distance between the bars: 1443 mm

[0137] The article is then heated to 715°C and then quenched according to current techniques. Connectors are then soldered to each of the strips 3 and electrically connected via electrical cables to a multimeter to measure their total resistance.

[0138] The articles thus obtained (reference and according to the invention) are then assembled in triple glazing with two other glass substrates comprising a low-emissive stack integrating a silver layer as described in example 1 of publication FR2940272A1, according to the principles given previously and in accordance with [Fig.3] attached. The heating coating is arranged on face 2 and the low-emissive stacks are arranged respectively on faces 3 and 5 of the triple glazing.

[0139] As for the previous examples, for each of the configurations obtained, the total resistance of the coating 2 is measured for a plurality of glazings of the two series of glazings (according to the invention and comparative).

[0140] Considering the dimensions of the current supply bars, the distance between them and the dimensions of the glazing, a resistance of the order of 155 Ohms is expected, with a tolerance margin of plus or minus 10 Ohms.

[0141] Figures 7 and 8 show the resistances obtained for the coatings for all the glazings measured (one point corresponding to one sample).

[0142] [Fig.7] corresponds to the glazings of the first series of reference articles and [Fig.8] corresponds to the glazings of the second series of articles according to the invention.

[0143] It can be seen that the glazings according to the invention exhibit a lesser and very low variability in the total resistance of the stack after toughening.

[0144] Furthermore, some samples of the reference series are sometimes even outside the required specification as can be seen in [Fig.7] while all the samples according to the invention comply with said specification (see [Fig.8]).

[0145] Additional tests in actual operation have shown that the application of such glazing as a transparent door of a freezer effectively prevents the appearance of condensation on the external surface of the glazing and perfect visibility through it in cold conditions of the order of -24°C, even if a low voltage is applied to the heatable coating, in particular of the order of 110V or even less.

[0146] In particular, tests carried out show that no trace of condensation appears on the external surface of triple glazing according to the invention, under external temperature conditions of 35 to 40°C and a humidity level of the order of 75 to 85%, when the temperature of the refrigerated compartment is maintained at -24°C.

Claims

Claims

1. Glass article comprising a glass substrate on which a heatable coating is deposited, said heatable coating being constituted by the following succession of layers, from the surface of said substrate: - a first layer of dielectric material comprising silicon nitride, with a thickness of between 1 and 20 nm, preferably between 1 and 10 nm. - a layer of a transparent electrically conductive oxide (TCO), with a thickness of between 1 nm and 40 nm, preferably between 5 and 35 nm, - a second layer of dielectric material comprising silicon nitride, with a thickness of between 1 and 20 nm, preferably between 5 and 15 nm, - a layer comprising a titanium oxide, a zirconium oxide or a zirconium and titanium oxide, with a thickness of between 1 nm and 15 nm, preferably between 1 and 5 nm.

2. A glass article according to claim 1, wherein the electrically conductive layer comprises and preferably is based on an indium tin oxide.

3. Glass article according to one of claims 1 or 2, in which the electrically conductive layer has a thickness of 8 nm to 15 nm.

4. Glass article according to one of claims 1 or 2, in which the electrically conductive layer has a thickness of 15 nm to 30 nm

5. 11111. Glass article according to one of the preceding claims, in which said first dielectric layer consists essentially of silicon nitride, optionally doped with an element chosen from Al, Zr, B, preferably Al, said layer possibly being partially oxidized under the effect of a heat treatment.

6. Glass article according to one of the preceding claims, in which said second dielectric layer consists essentially of silicon nitride, optionally doped with an element chosen from Al, Zr, B, preferably Al, said layer possibly being partially oxidized under the effect of a heat treatment.

7. Glass article according to one of the preceding claims, further comprising at least two current supply strips arranged above said heatable coating and in contact with the latter.

8. Glass article according to the preceding claim, in which said at least two current supply strips are arranged along two opposite ends of said article, preferably in the direction of its greatest length.

9. A glass article according to any preceding claim wherein said coating has a resistance per square of between 50 ohms per square and 400 ohms per square.

10. Glass article according to one of the preceding claims, in which the substrate is a thermally prestressed glass pane, before or after the deposition of said coating.

11. Multiple glazing, comprising a glass article according to one of the preceding claims and at least one other glass substrate separated from said article by a gas layer or a thermoplastic sheet, in particular PVB, said coating being in contact with the gas layer or the thermoplastic sheet.

12. Multiple glazing according to the preceding claim, in which said coating is deposited on face 2 or face 3 of said glazing, preferably on face 2 of said glazing.

13. Glazing according to one of claims 11 to 12 further comprising a low-emissivity stack, preferably deposited on face 3 of said glazing.

14. Multiple glazing according to one of claims 11 to 13, in which the glazing is double glazing, preferably in which said coating is deposited on face 2 of said glazing and more preferably in which a low-emissivity stack is deposited on face 3 of said glazing.

15. Multiple glazing according to one of claims 11, in which the glazing is triple glazing.

16. Triple glazing according to the preceding claim, wherein said coating is deposited on face 2 or face 5 of said glazing, preferably on face 2 of said glazing.

17. Triple glazing according to one of claims 15 or 16, wherein said coating is deposited on face 2 of said glazing and wherein said glazing comprises a low-emissivity coating, said low-emissivity coating being arranged on face 3 and / or on face 5, preferably on face 3 of said glazing.

18. Triple glazing according to one of claims 15 or 16, wherein said coating is deposited on face 5 of said glazing and wherein said glazing comprises a low-emissivity coating, said low-emissivity coating being arranged on face 2 and / or on face 4, preferably on face 2 of said glazing.

19. Multiple glazing according to one of claims 13, 14, 17 or 18, in which said low-emissivity stack(s) comprises at least one silver layer and layers of dielectric materials.

20. Multiple glazing according to one of claims 13, 14, 17 or 18, in which said low-emissivity stack(s) comprises an ITO layer and layers of dielectric materials.

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