SHEET GLASS FOR AIRCRAFT COCKPIT

Abstract

The invention relates to a laminated side or front glazing for an aircraft cockpit, comprising a first substrate (S1), a second substrate (S2), said first and second substrates being bonded together via a first polymer interlayer (I1), and a third substrate (S3) bonded to the second substrate (S2) via a second polymer interlayer (I2), in which at least one of said substrates is made of chemically toughened glass, characterized in that it comprises a heating coating (R1, R2, R3, R4) comprising at least one silver-based functional metal layer and at least two dielectric coatings, in which said heating coating is present on one face 2 to 5 of said glazing, in which the interlayer (I1, I2) in contact with said face coated with the heating coating is, on its other surface, directly in contact with the facing glass substrate and in which said heating coating has a resistance per square of between 1,5 and 8 Ohms / square.,

Description

Title of the invention: LAMINATED GLASS FOR AERIAL VEHICLE COCKPIT

[0001] The present invention relates to the field of glazing intended for aeronautics, in particular glazing for cockpits.

[0002] Cockpit glazing is a complex system that fulfills multiple roles. It provides physical, acoustic and thermal protection from the external environment.

[0003] For this purpose, these glazings are laminated glazings. A laminated glazing comprises at least one glass substrate, preferably several, for example two or three, glass substrates bonded together by means of polymer interlayers also called lamination interlayers. Glazings for aeronautics generally comprise at least three substrates and most often three substrates, preferably all made of glass.

[0004] Conventionally, the faces of a glazing are designated from the outside by numbering the faces of the substrates from the outside to the inside of the passenger compartment or room it equips. This means that the incident sunlight passes through the faces in increasing order of their number.

[0005] In the case of laminated glazing, all the faces of the substrates are numbered but the faces of the lamination interlayers are not numbered. Face 1 is on the outside of the building or vehicle and therefore constitutes the outer wall of the glazing. Faces 2 and 3 are in contact with the first lamination interlayer. In the case of laminated glazing comprising three substrates, faces 4 and 5 are in contact with the second lamination interlayer and face 6 is inside the building or vehicle and therefore constitutes the inner wall of the glazing.

[0006] Laminated glazing for aeronautics preferably has a structure of the first substrate / first polymer interlayer / second substrate / second polymer interlayer / third substrate type.

[0007] For these applications, at least one of said substrates, most often all of them, are curved and chemically toughened glass substrates. The substrates are made of chemically toughened glass, that is to say that they comprise a surface area in compression obtained by ion exchange. This surface area in compression is obtained by the surface substitution of an ion of the glass substrate (generally an alkali ion such as sodium or lithium) by an ion of larger ionic radius (generally an alkali ion, such as potassium or sodium). This makes it possible to create compressive stresses on the surface of the glass substrate, up to a certain depth. These superficial compressive stresses are in fact balanced by the presence of a central tension zone. There is therefore a certain depth at which the transition between compression and tension occurs, a depth called the superficial exchange depth.

[0008] These laminated glazings may further comprise coatings providing additional functionalities. For example, at least one of the substrates may be coated with a heating coating with an anti-frost or de-icing function comprising an electrically conductive layer.

[0009] Thus, a heating layer with a defrosting function may be present on one of the faces of the laminated glazing, this layer generally being based on ITO (transparent conductive layer of an indium and tin oxide), because the glazing must maintain a high light transmission, preferably greater than 70%. Conductive strips located on at least two opposite sides of the glazing make it possible to circulate an electric current in this ITO layer, generating heat by Joule effect, and thus making it possible either to avoid frost or fogging or to defrost and / or demist the glazing. Since aeronautical glazing often has complex shapes (trapezoidal or pentagonal), the conductive layer may have a conductivity gradient (i.e. a non-homogeneous resistance per square) in order to allow homogeneous heating (power density) across the entire glazing.The solution conventionally used consists of deliberately modulating the thickness of the ITO layer in order to obtain different and optimized resistances per square according to the areas of the glazing, which often turns out to be quite complex. Another original solution was proposed in the SGG application FR2956556A1: the conductivity gradient is obtained by subjecting a uniformly thick ITO layer to a plasma treatment having an oxidizing power adapted to each area whose resistance per square is to be modulated.

[0010] Due to the intended application, these glazings must also necessarily have high light transmission and low light absorption. However, if these glazings allow the visible part of the solar spectrum to pass into the cockpit, they also allow most of the infrared radiation to pass through. This results in excessive heating of the cockpit and an increase in its temperature which must be compensated for by an energy-consuming air conditioning system.

[0011] To overcome this problem, it is possible to introduce, into these cockpit windows, an element having a solar control (or protection) function.

[0012] The “solar control” function or property corresponds to the capacity of a glazing to let visible light in while blocking infrared radiation. The selectivity “S” and the solar factor (FS or g) make it possible to evaluate this property. The selectivity corresponds to the ratio of the light transmission TLvis in the visible of the glazing on the solar factor FS of the glazing (S = TLvis / FS). The solar factor "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 heating the "room". The smaller the solar factor, the lower the solar gains.

[0013] The purpose of adding an element with a solar control function is to prevent excessive overheating. However, the addition of this element must not be to the detriment of light transmission and light absorption.

[0014] To provide this solar protection function, different types of elements can be considered. It is particularly known to use lamination interlayers with a solar control function. For example, we can cite the Saflex® Solar interlayers made of polyvinyl butyral “PVB” of type SH and SG. These interlayers with high light transmission absorb infrared rays (IR). Laminated glazing for cockpits comprising such solar control interlayers is not satisfactory. Indeed, they are not selective enough.

[0015] To overcome these drawbacks, the applicant has developed a laminated glazing having a configuration particularly suitable for use as cockpit glazing comprising a single coating having a dual role of heating and solar control. The particular structure of the invention makes it possible to obtain an excellent compromise between low light absorption and light transmission and high selectivity. The invention makes it possible in particular to obtain a high selectivity which is not accessible by other technologies.

[0016] In the remainder of the description, such a coating according to the invention will be described by the generic term “heating coating” for simplification, it being understood that it also has an anti-solar function.

[0017] The invention therefore relates to a laminated lateral or frontal glazing of an aircraft cockpit, comprising, from the outside to the inside, a first substrate, a second substrate, said first and second substrates being bonded together by means of a first polymer interlayer, and a third substrate bonded to the second substrate by means of a second polymer interlayer, the successive glass faces of said glazing being numbered from 1 to 6 from the outside to the inside of said glazing, in which at least one of said substrates, preferably the second and / or the third substrate, is made of chemically toughened glass, characterized in that it comprises a heating coating comprising at least one silver-based functional metal layer and at least two dielectric coatings, each dielectric coating comprising at least one dielectric layer,so that each functional metal layer is arranged between two dielectric coatings.

[0018] According to the present invention:

[0019] - said heating coating is present on an internal face of said glazing, that is to say one side 2 to 5,

[0020] - the interlayer in contact with said face coated with the heating coating is, on its other surface, directly in contact with the facing glass substrate (by directly in contact, we mean in particular that no coating (or layer) is placed between the interlayer and the glass face in question),

[0021] - said heating coating has a resistance per square of between 1.5 and 8 Ohms / square, preferably between 2 and 6 Ohms / square and very preferably between 2 and 5 Ohms / square, or even between 2.5 and 4 Ohms / square.

[0022] According to preferred embodiments of the present invention: - Said heating coating (RI) is present on face 2 of said glazing between the surface of said first substrate (SI) and the surface of said first polymer interlayer (II), the other surface of said first polymer interlayer being in direct contact with the surface of said second substrate (S2). - said heating coating (R2) is present on face 3 of said glazing between the surface of said second substrate (S2) and the surface of said first polymer interlayer (II), the other surface of said first polymer interlayer being in direct contact with the surface of said first substrate (SI). - Said heating coating (R3) is present on face 4 of said glazing respectively between the surface of the second substrate (S2) and the surface of the second polymer interlayer (12), the other surface of said second polymer interlayer being in direct contact with the surface of said third substrate (S3). - Said heating coating (R4) is present on face 5 of said glazing respectively between the surface of the third substrate (S3) and the surface of the second polymer interlayer (12), the other surface of said second polymer interlayer being in direct contact with the surface of said second substrate (S2). - All internal faces (2 to 5) other than the one covered with said heating coating are in direct contact with a polymer interlayer.

[0023] One of the features of the invention is that at least one of the substrates is chemically hardened.

[0024] These chemically toughened glass substrates can be defined as follows: - they include a surface area in compression obtained by ion exchange, and / or - they have a surface exchange depth greater than 50 pm and / or - they have surface compression stresses greater than 100 MPa.

[0025] Chemical hardening processes are perfectly known. Reference may in particular be made to patent application WO1994008910.

[0026] Preferably at least the second substrate or the third substrate is chemically hardened. More preferably the second and third substrates are chemically hardened.

[0027] The heating coating according to the invention is necessarily deposited after the chemical reinforcement step. This coating therefore does not undergo a heat treatment step after deposition. It must therefore preferably have acquired its definitive properties directly after its deposition.

[0028] According to the invention, the heating coating comprises at least one silver-based functional metal layer and at least two dielectric coatings, each dielectric coating comprising at least one dielectric layer, such that each functional metal layer is arranged between two dielectric coatings.

[0029] According to a preferred embodiment, the solar control coating comprises a single silver-based functional layer. Such coatings make it possible to obtain an optimal compromise between a significant reduction in the solar factor and a minimal reduction in light transmission. Coatings with a single silver layer thus make it possible to obtain the highest light transmissions of the glazing according to the invention, well above 70% (minimum value required in the aeronautics field).

[0030] It is possible to obtain light transmissions of the glazing according to the invention greater than 70% with coatings with several layers of silver, in particular with two silver-based layers despite the absorption necessarily generated by such layers.

[0031] If obtaining maximum light transmission is not the essential criterion sought, it is therefore possible to use a heating coating comprising at least two silver-based functional layers. Such coatings make it possible to obtain higher selectivity but result in a reduction in light transmission.

[0032] The particular structure based on at least three substrates bonded together by two polymer interlayers is particularly suitable for aeronautical applications. In the case of an air vehicle, the first substrate is not held by a vehicle bonding system. Only the other two substrates, called structural, are held. The first substrate constitutes the outer part of the glazing. It is not generally structurally fixed to the aircraft it equips. It is simply held to the second substrate by the polymer interlayer. The second and third substrates are mechanically fixed in the aerial vehicle. It is these two substrates that ensure the protection of people inside the vehicle. The assembly formed by the second substrate, the second polymer interlayer and the third substrate must therefore have excellent impact resistance.

[0033] As a result, the edge of the first substrate may be set back relative to that of the second substrate to prevent delamination phenomena due to deformations of the glazing subjected to the pressure of the aircraft or to the mechanisms of tearing and / or peripheral shearing of the external substrate.

[0034] The first polymer interlayer is preferably based on polyurethane. The specific choice of this material for this polymer interlayer is justified because it is less hygroscopic, that is to say that it has less tendency to absorb and / or retain water than other polymer interlayers, for example PVB. This first interlayer keeps the substrate furthest outwards and therefore most likely to be subjected to extreme climatic conditions. The second polymer interlayer is preferably based on polyvinyl butyral. The specific choice of this material for this polymer interlayer is justified by its better mechanical properties, particularly impact resistance. In addition, due to its "internal" position, its chemical durability is less critical than that of the first polymer interlayer.

[0035] The glazing according to the invention may have the following characteristics alone or in combination: - the coating comprises a single silver-based metallic layer, - the coating comprises at least two silver-based metal layers,

[0036] - it has a selectivity greater than 1.4,

[0037] - it has a light transmission greater than 60%, preferably greater than 65% or even higher than 70%,

[0038] - the glazing does not contain a conductive oxide layer such as a layer indium tin oxide (ITO) or SnO2:F, in particular as a heating layer,

[0039] - the glazing does not include other coatings with an anti-solar function and / or heating. - the polymer interlayers are chosen from polyurethane (PU) and polyvinyl butyral (PVB) sheets, - the first polymer interlayer is chosen from polyurethane (PU) sheets, - the second polymer interlayer is chosen from polyvinyl butyral (PVB) sheets,

[0040] - the second interlayer is directly bonded to the second and third substrates, - the thickness of the first polymer interlayer is between 3 and 10 mm, preferably 4 and 8 mm, - the thickness of the second polymer interlayer is between 0.5 and 4 mm, between 0.5 and 2 mm, - the thickness of the first substrate is between 2 and 4 mm and the thickness of the second substrate is between 4 and 8 mm or between 5 and 7 mm,

[0041] - the glazing also comprises means for collecting and distributing a electric current, electrically connected to the heating stack and in particular to at least one silver-based layer, in particular in the form of current supply strips (busbars).

[0042] - said collection and distribution means are constituted by a set of bars current supply (busbars) located on at least two opposite edges of said glazing, said bars being in contact with at least one layer of silver of said heating stack.

[0043] - the heating coating has a conductivity gradient, said gradient being adjusted to maintain a homogeneous power density over the entire surface of said heating coating, for example the conductivity gradient is obtained by a thickness gradient of at least one silver-based layer.

[0044] The invention also relates to the use of the laminated glazing according to the invention as cockpit glazing for an air vehicle, and an airplane or helicopter characterized in that it is equipped with said glazing, as side or front glazing for a cockpit or even an airplane or helicopter equipped with the glazing according to one of the preceding characteristics, as side or front glazing for a cockpit.

[0045] 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.

[0046] Conventionally, refractive indices are measured at a wavelength of 550 nm.

[0047] Unless otherwise stated, the thicknesses mentioned in this document without further details are physical, real or geometric thicknesses called Ep and are expressed in nanometers (and not optical thicknesses).

[0048] The coating according to the invention is deposited by magnetic field-assisted sputtering (magnetron process). According to this advantageous embodiment, all the layers of the coatings are deposited by magnetic field-assisted sputtering.

[0049] 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) layer(s) interposed between these two layers (or layer and coating).

[0050] In the present 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 he or she comprises is at least 50%, in particular at least 70%, preferably at least 90%.

[0051] According to the invention: - light reflection corresponds to the reflection of solar radiation in the visible part of the spectrum, - light transmission corresponds to the transmission of solar radiation in the visible part of the spectrum, - light absorption corresponds to the absorption of solar radiation in the visible part of the spectrum.

[0052] Ordinary clear glass 2 to 6 mm thick has the following luminous characteristics: - a light transmission between 85 and 91.5%, - a light reflection of between 7 and 9.5%, - a light absorption of between 0.3 and 5%.

[0053] The silver-based metal functional layers preferably comprise 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, a 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.

[0054] The silver-based metal functional layers have a thickness: - greater than 5 nm, 6 nm, 7 nm, 8 nm or 9 nm, and / or - less than 25 nm, 22 nm, 20 nm, 18 nm, 16 nm, 15 nm, 14 nm or 13 nm.

[0055] The heating coating may comprise one or more blocking layers located in contact below and / or above one or more functional layers.

[0056] The blocking layers traditionally have the function of protecting the functional layers from possible degradation during the deposition of the upper anti-reflective coating and during possible high temperature heat treatment.

[0057] 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, - metal oxide layers of one or more elements chosen from titanium, nickel, chromium and niobium.

[0058] The blocking layers may in particular be layers of Ti, TiN, TiOx, Nb, NbN, Ni, NiN, Cr, CrN, NiCr, NiCrN, NiCrOx, SnZnN. When these blocking layers are deposited in metallic, nitrided or oxynitrided 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 next layer or by oxidation in contact with the underlying layer.

[0059] Preferably, the blocking layers are titanium layers, i.e. these layers have been deposited in the form of metallic titanium.

[0060] According to advantageous embodiments of the invention, the blocking layer(s) satisfy one or more of the following conditions: - each functional metal layer is in contact with a blocking overlayer, and / or - the blocking layers are layers of titanium deposited in metallic form, and / or - the thickness of each blocking layer is at least 0.05 nm, or between 0.08 and 2.00 nm, between 0.10 and 1.00 nm or between 0.05 and 0.50 nm.

[0061] The sum of the thicknesses of all the blocking layers may be less than 2.0 nm, less than 1.5 nm, less than 1.0 nm or less than 0.5 nm.

[0062] By "dielectric layer" within the meaning of the present invention, it is to be understood that from the point of view of its nature, the material is "non-metallic", that is to say 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.

[0063] Preferably, each dielectric coating consists solely of one or more dielectric layers. Preferably, there is therefore no absorbent layer in the dielectric coatings so as not to reduce the light transmission.

[0064] The improvement of properties such as selectivity results from the precise control of the optical interference effects between the different layers making up the coating. This control is obtained by the choice of the nature, thickness and sequences of dielectric layers constituting the dielectric coatings.

[0065] The dielectric layers of the coatings have the following characteristics alone or in combination: - they are deposited by magnetic field-assisted sputtering, - they have a thickness greater than 2 nm, preferably between 4 and 200 nm.

[0066] The dielectric layers are conventionally chosen from oxide-based, nitride-based or oxynitride-based layers. The oxide-based layers of one or more elements comprise essentially oxygen and very little nitrogen. The oxide-based layers comprise in particular at least 90% in atomic percentage of oxygen relative to the oxygen and nitrogen in said layer. The nitride-based layers comprise essentially nitrogen and very little oxygen. Nitride-based layers comprise at least 90 atomic percent nitrogen relative to oxygen and nitrogen in said layer. Oxynitride-based layers comprise a mixture of oxygen and nitrogen. Silicon oxynitride-based layers comprise 10 to 90 atomic percent nitrogen relative to oxygen and nitrogen in said layer.

[0067] The amounts of oxygen and nitrogen in a layer are determined as atomic percentages relative to the total amounts of oxygen and nitrogen in the layer under consideration.

[0068] The dielectric layers are conventionally chosen from: - layers comprising silicon, aluminum and / or zirconium, optionally doped with at least one other element, - layers based on zinc and tin oxide, - layers based on titanium oxide, - zinc oxide-based layers.

[0069] Dielectric layers, in addition to their optical function, can have various other functions. For example, stabilizing layers, smoothing layers, and barrier layers can be mentioned.

[0070] Dielectric layers with barrier function (hereinafter barrier layer) are understood to mean a layer made of a material capable of acting as a barrier to the diffusion of oxygen and water at high temperature, coming from the ambient atmosphere or from the transparent substrate, towards the functional layer. Such dielectric layers are chosen from: - layers comprising silicon such as layers chosen from oxides such as SiO2 and Al2O3, nitrides such as Si3N4 and AlN, and oxynitrides such as SiO xNy> AlOxNy optionally doped with at least one other element, - layers containing aluminum, - layers based on zinc and tin oxide, - layers based on titanium oxide.

[0071] The layers comprising silicon comprise at least 50% by mass of silicon relative to the mass of all the elements constituting the layer comprising silicon other than nitrogen and oxygen.

[0072] The layers comprising silicon may be chosen from oxide-based, nitride-based or oxynitride-based layers such as silicon oxide-based layers, silicon nitride-based layers and silicon oxynitride-based layers.

[0073] The silicon oxide-based layers comprise at least 90 atomic percent oxygen relative to the oxygen and nitrogen in the silicon oxide-based layer. The silicon nitride-based layers comprise at least 90 atomic percent nitrogen relative to the oxygen and nitrogen in the silicon nitride-based layer. of silicon nitride. The silicon oxynitride-based layers comprise 10 to 90% (limits excluded) in atomic percentage of nitrogen relative to the oxygen and nitrogen in the silicon oxide-based layer. Preferably, the silicon oxide-based layers are characterized by a refractive index at 550 nm of less than or equal to 1.55. Preferably, the silicon nitride-based layers are characterized by a refractive index at 550 nm of greater than or equal to 1.95.

[0074] The layers comprising silicon may comprise or consist of elements other than silicon, oxygen and nitrogen. These elements may be chosen from aluminum, boron, titanium, and zirconium. The layers comprising silicon may comprise at least 2%, at least 5% or at least 8% by mass of aluminum relative to the mass of all the elements constituting the layer comprising silicon other than oxygen and nitrogen.

[0075] The layers comprising aluminum may be chosen from oxide-based, nitride-based or oxynitride-based layers such as aluminum oxide-based layers such as Al2O3, aluminum nitride-based layers such as AlN and aluminum oxynitride-based layers such as AlOxNy.

[0076] Preferably, the barrier layers are layers chosen from layers comprising silicon, layers based on titanium oxide and layers based on zinc and tin oxide.

[0077] The dielectric layers may be so-called stabilizing layers. For the purposes of the invention, “stabilizing” means that the nature of the layer is selected so as to stabilize the interface between the functional layer and this layer. This stabilization leads to strengthening the adhesion of the functional layer to the layers surrounding it. The stabilizing layers are preferably layers based on zinc oxide, optionally doped, for example, with 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.

[0078] The stabilizing dielectric layer(s) may be directly in contact with a functional layer or separated by a blocking layer.

[0079] Preferably, the last dielectric layer of each dielectric coating located below a functional layer is a stabilizing dielectric layer. Indeed, it is advantageous to have a stabilizing layer, for example, based on zinc oxide below a functional layer, because it facilitates the adhesion and crystallization of the silver-based functional layer and increases its quality and stability.

[0080] It is also advantageous to have a stabilizing layer, for example, based on zinc oxide above a functional layer, to increase its adhesion and optimally oppose diffusion on the side of the stack opposite the substrate.

[0081] The stabilizing dielectric layer(s) may therefore be located above and / or below at least one functional layer or each functional layer, either directly in contact with it or separated by a blocking layer.

[0082] Advantageously, each dielectric layer with barrier function is separated from a functional layer by at least one dielectric layer with stabilizing function.

[0083] The zinc oxide layers have, in order of increasing preference, a thickness: - of at least 3.0 nm, of at least 4.0 nm, of at least 5.0 nm, and / or - of at most 15 nm, of at most 10 nm, of at most 8.0 nm.

[0084] According to one embodiment, the sum of the physical thicknesses of all the oxide layers of each dielectric coating is greater than 50%, 60%, 70%, 80%, 90%, 95% or 99% of the total thickness of the dielectric coating.

[0085] A particularly advantageous embodiment relates to a substrate coated with a coating comprising, starting from the substrate: - a first dielectric coating comprising at least one layer with a barrier function and one dielectric layer with a stabilizing function, - a first functional layer, - possibly a blocking layer, - a second dielectric coating comprising at least one dielectric layer with a stabilizing function and a layer with a barrier function.

[0086] A particularly advantageous embodiment relates to a substrate coated with a coating comprising, starting from the substrate: - a first dielectric coating comprising at least one layer with a barrier function and one dielectric layer with a stabilizing function, - a first functional layer, - possibly a blocking layer, - a second dielectric coating comprising at least a first dielectric layer with a stabilizing function, a layer with a barrier function and a second dielectric layer with a stabilizing function, - a second functional layer, - possibly a blocking layer, - a third dielectric coating comprising at least one dielectric layer with a stabilizing function and a layer with a barrier function.

[0087] Heating of the stack containing the silver-based layer(s) is achieved by the Joule effect. The heating coating is powered via energized electrodes. Homogeneous heating of a non-rectangular or square shape is impossible with a continuous layer of homogeneous electrical conductivity.

[0088] In the case where the coating according to the invention comprises several silver-based layers, one or more, or even all of the layers may be heating, i.e. connected to said electrodes.

[0089] To homogenize heating on complex surfaces, the silver-based conductive layer may have an electrical conductivity gradient. This gradient can be obtained by a thickness gradient. Large variations in layer thickness make it possible to limit the current density in certain parts of the heating surface.

[0090] To homogenize the heating, the silver-based conductive layer may also comprise ablation lines, called flux separation lines or more commonly flux lines as described in patent EP1897412-B1, which guide the flow of electric current.

[0091] These two strategies can be used in combination.

[0092] Preferably, the mineral glass substrates which constitute the glazing are made of soda-lime, aluminosilicate or borosilicate glass.

[0093] Preferably, the lamination interlayers comprise one or more sheets of organic polymers.The organic polymers are chosen from polyvinyl butyral (PVB), polyurethanes (PU), polyureas, ethylene vinyl acetate (EVA), polyolefins (including polyethylene (PE), polypropylene (PP) or polyisobutylene (P-IB)), polyvinyl chloride and its derivatives (for example poly(vinyl dichloride) (PVDC)), styrenic polymers (for example polystyrene (PS), acrylostyrene butadiene (ABS), styrene acrylonitrile (SAN)), polyacrylics (including polyacrylonitrile (PAN) and poly(methyl methacrylate) (PMMA)), polyesters (including poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT)), polyoxymethylene (POM), polyamides (PA), fluorinated polymers such as polychlorotrifluoroethylene (PCTFE), polycarbonates (PC), aromatic polysulfones including polysulfone (PSU), polyphenylene ether (PPE), epoxy (EP) alone or in mixtures and / or copolymers of several of them.

[0094] According to preferred characteristics of the laminated glazing of the invention: - the laminated glazing comprises a third sheet of glass connected to the second sheet of glass by a second interlayer, and / or - the first glass substrate has a thickness of between 0.5 and 5 mm, preferably between 2 and 4 mm, and / or - the second glass substrate, and where applicable the third glass substrate, are made of glass with a thickness of between 4 and 10 mm, and / or - said interlayers are made of polyurethane (PU), polyvinyl butyral (PVB), ethylene vinyl acetate (EVA) or equivalent, and / or - the first interlayer is made of polyurethane, and / or - the second interlayer is made of polyvinyl butyral (PVB), and / or - the thickness of the first interlayer is between 2 and 10, preferably 4 and 8 mm, and / or - the thickness of the second interlayer is between 0.5 and 4, preferably at most equal to 2 mm, and / or - it has a selectivity greater than 1.4 or 1.5, and / or - it has a light transmission of at least 65% or at least 68%.

[0095] Figures 1 to 4 which follow illustrate different possible embodiments of the invention.

[0096] The figures attached to this description schematically represent a cross-sectional view of a preferred embodiment of the laminated glazing of the invention for a cockpit. A laminated glazing according to the invention therefore comprises: - a first SI glass substrate constituting an outer face of the curved and chemically toughened glazing, for example 3 mm thick, - a first interlayer II of polyurethane (PU), for example 5 mm thick, - a second substrate of curved and chemically toughened S2 glass, for example 6 mm thick, - a second interlayer 12 of polyvinyl butyral (PVB) 1.1 mm thick, - a third substrate of curved and chemically toughened glass, for example 6 mm thick, - a heating and solar control coating RI comprising at least one silver-based layer,

[0097] - two current supply conductive bars or strips (busbars) B deposited from on either side respectively on the substrate SI and electrically connected to at least one silver layer of the heating coating R

[0098] It should be noted that the dimensions (length, width) of these different elements, as shown in [Fig.l], are not representative of their real and relative dimensions. Furthermore, in the figures, the same numbers represent elements of the same nature as previously indicated.

[0099] Preferably, the entire peripheral edge of the laminated glazing is covered by a seal (J). This includes the edge of the first glass substrate, the edge of the first interlayer, a portion of the surface of the second glass substrate extending beyond the first glass substrate, the edge of the second glass substrate, the edge of the second interlayer, and the edge of the third glass substrate.

[0100] In [Fig.l], according to a first preferred configuration, the heating and solar control coating RI (and the associated busbars B1) are in contact with the first lamination interlayer II, and is deposited on the surface of the first substrate SI (face 2 of the glazing). In such an embodiment, the other face of the interlayer II is directly in contact with the substrate S2.

[0101] According to a second alternative embodiment shown diagrammatically in [Fig.2], the heating and solar control coating R2 (and the associated busbars B2) are in contact with the first lamination interlayer II, and are deposited on the surface of the second substrate S2 (face 3 of the glazing). In such an embodiment, the other face of the interlayer II is then directly in contact with the substrate SI.

[0102] According to a third alternative embodiment shown diagrammatically in [Fig. 3], the heating and solar control coating R3 (and the associated busbars B3) are in contact with the second lamination interlayer 12, and are deposited on the surface of the second substrate S2 (face 4 of the glazing). In such an embodiment, the other face of the interlayer 12 is then directly in contact with the substrate S3.

[0103] According to a fourth alternative embodiment shown diagrammatically in [Fig. 4], the heating and solar control coating R4 (and the associated busbars B4) are in contact with the second lamination interlayer 12, and are deposited on the surface of the third substrate S3 (face 5 of the glazing). In such an embodiment, the other face of the interlayer 12 is then directly in contact with the substrate S2.

[0104] According to a preferred embodiment of the invention and as shown in the attached figures 1 to 4, the faces 2 to 5 other than that covered with said heating coating are directly in contact with a polymer interlayer, i.e. either II or 12. Examples I. Materials and coatings

[0105] 1. ITO-based heating coatings (comparative examples)

[0106] According to a first comparative example 1, a first heating coating made of ITO according to the prior art (mixture of indium(III) oxide In2O3 and tin(IV) oxide SnO2, in a mass proportion of 90% of the first and 10% of the second), configured in a known manner to act as an anti-frost and anti-fog element for a front window of an aircraft, consists of a layer of indium tin oxide of 500 nm. This layer was deposited by magnetron sputtering on a 3 mm glass SI substrate, on the face corresponding to face 2 of the glazing. It has a resistance per square of 4 Q / D, as measured by the 4-point method or Van der Pauw method (see for example the reference work “Techniques de l'Ingénieur”, C3635 point 4.1, 1999)”. A second heating coating according to the prior art (comparative example 2), more particularly configured to act as an anti-fog element for a side window of an aircraft, consists of a 40 nm layer of indium tin oxide. This layer is deposited by magnetron sputtering on the external face of a 6 mm glass substrate, corresponding to face 3 of the glazing. It has a resistance by square of 50 Q / D measured by induction.

[0107] 2. Heating / solar control coatings comprising a silver layer (examples according to the invention)

[0108] The functional metal layer of the coating is this time a silver (Ag) layer. The blocking layer is a titanium (Ti) metal layer. The dielectric coatings include barrier layers and stabilizing layers. The barrier layers are based on titanium oxide and zinc tin oxide. The stabilizing layers are based on zinc oxide (ZnO). The deposition conditions of the layers, which were deposited by sputtering (so-called “magnetron cathode sputtering”), are summarized in Table 1.

[0109] [Tableauxl] Target Layer Used Deposition Pressure Gas ZnO Zn:Al at 98:2 wt% 1.8.10 3 mbar Ar / (Ar + 02) at 63% SnZnO Zn:Sn at 64:36% at 2.103 mbar Ar / (Ar + O2) at 50% TiO2 TiOx 2.10-3 mbar Ar / (Ar + 02) at 95% Ti Ti 2-3.10-3 mbar Ar at 100% Ag Ag 8.10-3 mbar Ar at 100%

[0110] Pds: Weight; at: Atomic

[0111] According to a first example 3 according to the invention, a front glazing of an aircraft cockpit is configured. The heating and solar control coating defined below is thus deposited on the glass substrate SI, 3 mm thick, on the face corresponding to face 2 of the glazing. It has a layer resistance of 3 Q / D, as measured by the Van der Pauw method.

[0112] According to a second example 4 according to the invention, a side glazing of an aircraft cockpit is configured. The heating and solar control coating defined below is thus deposited on the glass substrate S2, 6 mm thick, on the face corresponding to face 3 of the glazing. It has a layer resistance of 3 Q / D, as measured by the Van der Pauw method.

[0113] The structure of the heating stack of examples 3 and 4 according to the invention is given below:

[0114] Glass / TiO2 (20nm) / ZnO (lOnm) / Ag (13nm) / Ti (0.2nm) / ZnO (lOnm) / TiO2 (18nm) / ZnSnOx (lOnm). II. Configurations: glazing for aeronautics

[0115] In all examples, the glass substrates are Solidion® chemically toughened and curved glass substrates marketed by the applicant company.

[0116] The first lamination interlayers are 6.5 polyurethane interlayers mm. The second interlayers are 1.1 mm thick PVB interlayers. The laminated glazings have the following configuration: a first 3 mm thick SI glass substrate coated on face 2 with said heating coating / a first polyurethane (PU) interlayer / a second 6 mm thick S2 glass substrate / a second polyvinyl butyral (PVB) interlayer / a third 6 mm thick substrate. III. Results and analysis:

[0117] The heating power required to ensure the defrosting function in an aircraft cockpit window is different between a front window and a side window of an aircraft cockpit. It is of the order of:

[0118] - 70 W / dm2 for front glazing

[0119] - 10 to 20 W / dm2 for side glazing

[0120] The formula giving the dissipated power P in a conductive layer as a function of the applied voltage U, the square resistance R / D and the distance d between the bus bars is as follows:

[0121] P (W / m2) = U2 / (R / D x d2)

[0122] Table 2 below shows the different configurations tested and the results obtained.

[0123] [Tables2] Example 1 2 3 4 Type of glazing front side front Side According to Prior art Prior art Invention Invention ITO coating position Face 2 Face 3 none none Ag coating position None None Face 2 Face 3 Stack resistance 4 Ohms / square 50 Ohms / square 3 Ohms / square 3 Ohms / square Electrical voltage 115 V 115 V 115 V 28 V Distance between busbars 7 dm 5 dm 7 dm 5 dm Heating power 67.5 W / dm2 10.6 W / dm2 90 W / dm2 10.5 W / dm2

[0124] The results reported in Table 2 show that:

[0125] - a stack comprising a silver layer and having a resistance by square substantially equal to or slightly less than that of an ITO layer can allow, by electrically connecting it, to achieve a heating power comparable or even greater than that of an ITO layer for an identical geometry and applied voltage, by comparing the front glazings of example 3 (invention) with that of example 1 (comparative). The comparison of these two examples also shows that obtaining a resistance per square of the order of 4 ohms requires the use of a layer of conductive ITO oxide of substantial thickness (400 nm) whereas the total thickness of a stack comprising a silver layer necessary to obtain the same resistance per square and therefore the same heating power for an identical glazing geometry is less than a hundred nanometers, which results in a significantly lower manufacturing cost.

[0126] - This same stack comprising a silver layer can advantageously be used as a heating coating for a cockpit side glazing: by applying a voltage of only 28V to the thin silver layer, a similar heating power (here 10.5 W / dm2) can be achieved as if a voltage of 115V is applied to the ITO layer, as can be seen from the comparison of the glazings of example 4 (invention) with that of example 2 (comparative).

[0127] Furthermore, it has been measured that the glazings according to the examples according to the invention show a light transmission of the order of 73%, a solar factor value of 48% and a selectivity greater than 1.5.

[0128] Measurements carried out on glazing whose coating comprises the following sequence:

[0129] Glass / TiO2 (20nm) / ZnO (lOnm) / Ag (7nm) / Ti (0.2nm) / ZnO (lOnm) / TiO2 (18nm) / ZnSnOx (lOnm),

[0130] with a resistance greater than 8 Ohms / square lead to a solar factor greater than 58% and a selectivity less than 1.3, i.e. insufficient solar protection of the cockpit.

[0131] Similarly, measurements carried out on glazing whose coating comprises the following sequence: Glass / Si3N4 (31nm) / ZnO (6nm) / Ag (lOnm) / Ti (0.3nm) / ZnO (6nm) / Si3N4 (52nm) / ZnO (9nm) / Ag (15nm) / Ti (0.3nm) / ZnO (5nm) / Si3N4 (41nm) / ZnSnOx (14nm) / ZnO (9nm) / Ag (20nm) / Ti (0.3nm) / ZnO (5nm) / Si3N4 (24nm) / ZnSnOx (5nm),

[0132] with a resistance of less than 1.5 Ohm / square, lead to a light transmission of less than 60%, and consequently insufficient transparency of the cockpit.

[0133] Thus, the object of the present invention has the following advantages:

[0134] - The absence of indium allows substantial savings to be made because this metal is Dear.

[0135] - A silver layer according to the invention, with a resistance of less than 8 ohms per square, allows for certain glazings to achieve, at a lower manufacturing cost, similar heating powers with a lower electrical voltage than for an ITO-based stack, which may mean that an electrical transformer is not required in the aircraft specifically for the cockpit anti-icing function.

[0136] - The coating according to the invention also has a solar control function. and the absence of an ITO layer makes it possible to gain in transparency of the glazing. This gain in transparency can also make it possible to further optimize the silver stack and further improve its selectivity. In the absence of an ITO layer, the silver-based heating coating can be advantageously positioned on face 2, which can make it possible to gain in solar control performance and in particular in selectivity compared to the case where such a silver coating would be used only as solar control on face 3, coupled with an ITO-based heating layer on face 2.

[0137] - Adapting the conductivity of the silver-based coating to enable a homogeneous heating for complex-shaped glazing can be obtained with a more pleasant aesthetic result (less visible) than that currently obtained with an ITO layer of variable thickness, in which strong iridescence is observed in external reflection.

[0138] According to advantageous embodiments of the invention, in particular if the glass is flat, the geometric gradient of electrical conductivity of the silver-based stack and thus to any shape of the glazing can be adapted to allow uniform heating over the entire surface to be defrosted.

[0139] Such an electrical conductivity gradient can be obtained, for example, by a thickness gradient of the Ag layer and / or by modification of the other layers of the stack having an impact on the conductivity of the silver (such as the ZnO or Ti layers), for example by varying their thickness or their degree of oxidation.

Claims

Claims

1. Laminated side or front glazing for an aircraft cockpit, comprising a first substrate (S1), a second substrate (S2), said first and second substrates being bonded together via a first polymer interlayer (II), and a third substrate (S3) bonded to the second substrate (S2) via a second polymer interlayer (12), the successive glass faces of said glazing being numbered from 1 to 6 from the outside to the inside of said glazing, in which at least one of said substrates, preferably the second and / or the third substrate, is made of chemically toughened glass, characterized in that it comprises a heating coating (RI, R2, R3, R4) comprising at least one silver-based functional metal layer and at least two dielectric coatings, each dielectric coating comprising at least one dielectric layer,so that each functional metal layer is arranged between two dielectric coatings, said glazing being characterized in that said heating coating is present on one face of said glazing, said face being a face 2 to 5, in that the interlayer (II, 12) in contact with said face coated with the heating coating is, on its other surface, directly in contact with the facing glass substrate and in that said heating coating has a resistance per square of between 1.5 and 8 Ohms / square.,

2. Laminated glazing according to claim 1 characterized in that said heating coating (RI) is present on face 2 of said glazing between the surface of said first substrate (SI) and the surface of said first polymer interlayer (II), the other surface of said first polymer interlayer being in direct contact with the surface of said second substrate (S2).

3. Laminated glazing according to claim 1 characterized in that said heating coating (R2) is present on face 3 of said glazing between the surface of said second substrate (S2) and the surface of said first polymer interlayer (II), the other surface of said first polymer interlayer being in direct contact with the surface of said first substrate (SI).

4. Laminated glazing according to claim 1 characterized in that said heating coating (R3) is present on face 4 of said glazing respectively between the surface of the second substrate (S2) and the surface of the second polymer interlayer (12), the other surface of said second interlayer polymer being directly in contact with the surface of said third substrate (S3).

5. Laminated glazing according to claim 1 characterized in that said heating coating (R4) is present on face 5 of said glazing respectively between the surface of the third substrate (S3) and the surface of the second polymer interlayer (12), the other surface of said second polymer interlayer being in direct contact with the surface of said second substrate (S2).

6. Laminated glazing according to any one of the preceding claims, in which all the faces 2 to 5 other than that covered with said heating coating are directly in contact with a polymer interlayer.

7. Laminated glazing according to any one of the preceding claims, characterized in that the heating coating comprises a single silver-based functional metal layer.

8. Laminated glazing according to any one of claims 1 to 6, characterized in that the heating coating comprises at least two silver-based functional metal layers.

9. Laminated glazing according to any one of the preceding claims, characterized in that it has a selectivity greater than 1.

4.

10. Laminated glazing according to any one of the preceding claims, characterized in that it has a light transmission greater than 60%, preferably greater than 70%.

11. Laminated glazing according to any one of the preceding claims, characterized in that the polymer interlayers are chosen from polyurethane (PU) and polyvinyl butyral (PVB) sheets.

12. Laminated glazing according to any one of the preceding claims, characterized in that the first polymer interlayer is chosen from polyurethane (PU) sheets.

13. Laminated glazing according to any one of the preceding claims, characterized in that the second polymer interlayer is chosen from polyvinyl butyral (PVB) sheets.

14. Laminated glazing according to one of the preceding claims, characterized in that the thickness of the first polymer interlayer is between 3 and 10 mm and in that the thickness of the second polymer interlayer is between 0.5 and 4 mm.

15. Laminated glazing according to one of the preceding claims, characterized in that the thickness of the first substrate is between 2 and 4 mm and the thickness of the second substrate is between 4 and 8 mm or between 5 and 7 mm.

16. Laminated glazing according to one of the preceding claims, characterized in that it comprises means for collecting and distributing an electric current, electrically connected to the heating stack and in particular to at least one silver-based layer.

17. Laminated glazing according to one of the preceding claims in which said collection and distribution means consist of a set of current supply bars (busbars) located on at least two opposite edges of said glazing, said bars being in contact with at least one layer of silver of said heating stack.

18. Laminated glazing according to one of the preceding claims, characterized in that it does not contain a conductive oxide layer such as a layer of indium tin oxide (ITO) or SnO2:F, in particular as a heating layer.

19. Laminated glazing according to one of the preceding claims in which the heating coating has a conductivity gradient, said gradient being adjusted to maintain a homogeneous power density over the entire surface of said heating coating.

20. Laminated glazing according to the preceding claim in which the conductivity gradient is obtained by a thickness gradient of at least one silver-based layer.

21. Aircraft or helicopter characterized in that it is equipped with the glazing according to one of the preceding claims, as side or front glazing for the cockpit.

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