Aviation laminated glass having electric heating system, use of aviation laminated glass as aircraft cockpit glass, and associated aircraft

Abstract

The invention relates to an aeronautical laminated glass (1) comprising a first sheet (2) on an outer side and at least one second structural sheet (3a, 3b) on an inner side, the aeronautical laminated glass (1) further comprising at least one electric heating system (9) arranged facing an inner face of the first sheet (2), the aeronautical laminated glass (1) further comprises an equipotential layer (10) applied to the inner face of the first sheet (2).

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of aeronautics, and in particular to an aeronautical laminated glass with an integrated electrical heating system, the use of such aeronautical laminated glass as a cockpit glass of an aircraft, and an aircraft comprising such aeronautical laminated glass as a cockpit glass. BACKGROUND

[0002] Aeronautical laminated glass is generally made of an electrically insulating material such as mineral glass, PMMA (Polymethyl methacrylate), PC (Polycarbonate), etc., which tends to become electrically charged in certain charged environments, which can be of two types, namely: - triboelectric loads associated with the impact of particles such as dust, snow, ice crystals, etc. on the outer surface of the laminated glass (facing the aircraft), and - charges associated with lightning (less common).

[0003] Under these conditions, the outer surface of the laminated glass can generate very high potentials of several kV or even tens of kV (relative to the ground potential of the aircraft).

[0004] The surface potential of the laminated glass is thus different from the surface potential of the aircraft structure, which is generally equipped with passive dissipators (for example, corona effect at the tips), allowing the accumulated charges to flow over the entire conductive structure of the aircraft.

[0005] In addition, the aircraft cockpit laminated glass generally contains an electrical heating system covering all or part of the inner face of the panels (also called "layers") on the outer side of the laminated glass (facing away from the aircraft).

[0006] There are two categories of laminated aircraft cockpit glass with integrated heating systems: on the one hand, the windshield or front window, which is equipped with an electrical heating system for de-icing purposes; and on the other hand, the side windows, which are generally equipped with an electrical heating system for anti-fog purposes only. These two heating systems (de-icing and anti-fog) differ in terms of specific power delivered, with the anti-fog heating system generating a lower electric field.

[0007] The high potential generated on the outer surface of the laminated glass creates a strong electric field, which can discharge by dielectric breakdown, etc.: either in air (between the outer surface of the glass and the conductive structure of the aircraft at the periphery of the laminated glass); or in the thickness of the panels on the outer side of the laminated glass, between their outer face and the electrical heating system (for example, the heating layer) arranged on their inner face.

[0008] The air discharge can be localized, or develop into a surface discharge (generally known in aeronautics as Saint Elmo's fire).

[0009] Thus, the two mechanisms compete with each other, so that the first of the two mechanisms to be triggered prevents the occurrence of the other one by completely or partially neutralizing the outer surface of the outer ply. However, the consequences of surface discharges and dielectric breakdown in the outer ply are radically different. Surface discharges generate glare and electrical transients in the glass circuit, but both phenomena are accepted or managed on many aircrafts. In contrast, dielectric breakdown in the thickness of the outer ply can lead to perforation and / or breakage, which are both glass failure modes requiring replacement.

[0010] Therefore, glass designers aim at avoiding reaching the dielectric breakdown field in the outer ply. This can be achieved by draining the surface charges with an antistatic layer. In the case of heat-coated glass, this is of course managed by surface discharges. However, the local intensity effect in the heating system increases the electric field in the outer ply locally to very high levels and can lead to dielectric breakdown in the outer ply before surface discharges occur.

[0011] A first known case of electric field concentration occurs with heating by thin metal wires. The need for wires invisible to the pilot implies that wires with a diameter typically of 20 to 30 pm are used. Due to the small radius of the wires, these wires highly concentrate the electric field and, in the absence of a dedicated system for minimizing the surface potential, lead to breakage in the outer ply.

[0012] A second, more rare, case of electric field concentration is found at the edges of the heating layer.

[0013] In both cases, the occurrence of dielectric breakdown is all the more increased because the concerned areas are difficult to neutralize by surface discharges. This is mainly the case for heating meshes positioned far from the metallic structure of the aircraft.

[0014] Indeed, in the area where the electric heating system, such as a heating layer, forms a capacitance with the charged outer surface of the laminated glass, surface discharges are admitted. Typically, this capacitance can be compared to a planar capacitor whose dielectric separating the charged planes is formed by the thickness of the sheet on the outer side of the laminated glass, for example 3 mm of glass. Surface discharges dissipate electrical energy by neutralizing the surface. This energy feeds the propagation of an arc in the ionized air until the arc resistance in the air, a function of the arc length, no longer ensures a sufficient potential difference between the arc head and the outer surface of the glass to ionize the air.

[0015] In the case of an electric heating system, such as a heating layer, lacking an indirect link to the ground potential of the aircraft, the glass surface is capacitively coupled to a much more distant ground plane, so that the energy stored by the surface charges is significantly reduced and cannot power a surface discharge.

[0016] In order for a surface discharge to occur, there must be a sufficient electric field in the air between the periphery of the laminated glass and the edge of the opposite electric heating system. Thus, locations where the electric heating system is closer to the periphery of the glass are more prone to trigger a surface discharge than locations where the electric heating system is further away from the periphery of the glass.

[0017] Because a surface discharge is not able to extend over the entire surface of the glass (due to the arc resistance increasing with the size of the arc), the edge of the electric heating system further away from the edge of the glass can reach a higher potential than the rest of the surface of the glass. These areas are thus more likely to observe a dielectric breakdown in the thickness of the laminated glass panel on the outside, which can cause the panel to break, thus causing the laminated glass to fail.

[0018] Furthermore, the edge of the electric heating system creates an electric field singularity, i.e. a local intensity effect, which promotes a dielectric breakdown in the laminated glass.

[0019] These problems are generally solved by applying an electrostatic discharge layer, called an antistatic layer, to the outer surface of the laminated glass, which gives the glass a surface conductivity. The resistivity of this antistatic layer generally ranges in order of magnitude from a few tens of kOhm to a few tenths of a megaOhm. This antistatic layer is generally electrically connected to the aircraft structure, in order to dissipate the weak charging currents and to maintain the outer surface of the laminated glass at the ground potential of the aircraft.

[0020] However, this antistatic layer is exposed to the external environment of the aircraft (impacts from water droplets, dust, water, aircraft ground cleaning, for example) and can eventually come off the outer surface of the laminated glass. There is thus a risk of panel breakage on the outside of the laminated glass in a loaded environment. SUMMARY

[0021] The aim of the present invention is to overcome the drawbacks of the prior art by providing an aircraft laminated glass with an integrated electric heating system, comprising an equipotential layer applied to the inner face of the panel on the outside, in order to obtain a lasting solution for preventing dielectric breakdown of the panel on the outside of the laminated glass in a charged environment.

[0022] The aim of the present invention is thus an aircraft laminated glass comprising a first panel on the outside, at least one second structural panel on the inside and an intermediate layer arranged between the first panel and the at least one second structural panel, the first panel and the at least one second structural panel being made of at least one of inorganic glass or organic glass, the aircraft laminated glass further comprising at least one electric heating system arranged facing the inner face of the first panel, characterized in that the aircraft laminated glass further comprises an equipotential layer applied to the inner face of the first panel.

[0023] The term "panel on the outside" designates the panel (or layer) of laminated glass on the outside of the aircraft on which it is mounted, and the term "panel on the inside" designates the panel (or layer) of laminated glass on the inside of the aircraft on which it is mounted. In this way, the outer face of the first laminated glass panel is in contact with the outside environment of the aircraft.

[0024] The interlayer of the laminated glass serves as a spacer between the first panel and the at least one second structural panel of the laminated glass.

[0025] It should be noted that, in the case where the laminated glass comprises a plurality of second structural panels, an interlayer of the interlayer type is also arranged between each pair of adjacent second structural panels.

[0026] The first and second structural panels of the laminated glass can either be mineral glass (for example soda-lime, borosilicate, aluminosilicate, etc.), or organic glass (for example PMMA (polymethyl methacrylate), PC (polycarbonate), etc.). It should be noted that the at least one second structural panel can also be made of organic glass, such as a PET (polyethylene terephthalate) film, without departing from the scope of the application.

[0027] The equipotential coating applied to the inner face of the first panel on the outside of the laminated glass has a uniform potential over its entire surface. Note that "equipotential" here means a uniform potential with respect to the charge potential of several tens of kV, so that all potentials between 0 V and 500 V will be considered uniform with respect to a charge potential of several tens of kV (typically, a potential of 200 V will thus be considered equivalent to a potential of 0 V on an equipotential layer).

[0028] The equipotential layer is encapsulated within the laminated glass, so it is not susceptible to attack, dissolution or scratching. This lower susceptibility makes it possible to consider thinner layers, which can be easier to deposit or have less optical impact.

[0029] The application thus makes it possible to obtain a durable solution (not subject to attack of the antistatic layer) to eliminate the risk of rupture or perforation of the heating layer of the aeronautical glass (characterized by a reduced heating zone) due to dielectric breakdown in the thickness of the outer panel in a charged environment.

[0030] According to one embodiment of the application, the at least one electric heating system is applied to the equipotential layer and has a first actual or equivalent surface resistivity, and the equipotential layer has a second actual or equivalent surface resistivity, which is greater than the first actual or equivalent surface resistivity.

[0031] Since the equipotential layer applied to the inner face of the first sheet on the outer side up to the edge of the glass (possibly except one peripheral edge) has a higher surface resistivity than the at least one electrical heating system applied to the equipotential layer, the equipotential layer is substantially less conductive than the at least one electrical heating system, so that it does not interfere with the flow of the heating current in the electrical heating system. By interposing the equipotential layer between the electrical heating system and the inner surface of the glass, the high potential on the outer surface of the glass (whether from triboelectric loading or lightning) is shielded out, thus eliminating the field concentration within the first sheet on the outer side due to the local intensity effect of the electrical heating system.

[0032] If an arc strikes the outer side of the laminated glass, its surface potential rises and the arc rapidly adheres to the structure. This rapid rise in potential can lead to the risk of electric field concentration at the edges of the electrical heating system, leading to dielectric breakdown in the first sheet on the outer side of the laminated glass. By applying an equipotential layer that is significantly more resistive, these field concentrations are eliminated without interfering with the heating process.

[0033] The equipotential layer ensures that the entire inner face of the first sheet on the outer side of the laminated glass remains at the aircraft ground potential (within a few hundred volts).

[0034] In this way, we benefit from three effects that prevent dielectric breakdown in the first sheet on the outer side of the laminated glass: - Facilitate surface discharging; - If the electrical heating system is of the resistive heating layer type, eliminate the local electrostatic intensity at the edges of the heated surface, since the adjacent layers are at very close potentials; - If the electrical heating system is a network of thin resistive heating wires, eliminate the local intensity effect around each thin wire.

[0035] Relevant in terms of the risk of short-circuiting of the heating current through the equipotential layer is the comparison of the equivalent resistivity of the electrical heating system and the equipotential layer. The concept of surface resistivity is strictly defined for homogeneous conductive layers only, and for a homogeneous square conductive layer corresponds to the resistance between two electrodes placed on opposite sides of the square. The equivalent surface resistivity is defined as the resistivity of a homogeneous layer that connects two electrodes. Thus, a wire heating system whose wires connect two electrodes can be described as an equivalent homogeneous layer. Similarly, a globally homogeneous discontinuous layer can induce an equivalent resistivity higher than the resistivity of the same layer where it is continuous, due to the tortuosity of the current flow. Finally, if the continuous electrical path linking two electrodes is completely open, the equivalent resistivity tends to infinity.

[0036] According to a particular feature of the invention, the ratio between the second actual or equivalent surface resistivity and the first actual or equivalent surface resistivity is greater than or equal to 10, preferably greater than or equal to 100.

[0037] This high ratio means that the equipotential layer does not short-circuit at least one electric heating system.

[0038] The equipotential layer thus has a surface resistivity or apparent surface resistivity significantly higher than the resistivity of the electric heating system (for example obtained by partial ablation of the layer).

[0039] According to a particular feature of the application, the equipotential layer is a transparent conductive layer configured to be directly or indirectly connected to the ground of the mounting structure of the aeronautical laminated glass.

[0040] In this way, the transparent, equipotential, high-resistivity conductive layer is either directly connected to the ground of the aircraft on which the laminated glass is mounted via electrical means (such as wires, screen printing, welding, conductive bonding, etc.), or indirectly connected via an impedance. The ground connection can also be made via at least one electric heating system.

[0041] According to a particular feature of the application, the transparent conductive layer is made of a material chosen from doped oxides (such as indium tin oxide or aluminum zinc oxide), non-stoichiometric oxides (such as tin dioxide), diamond-like carbon, and silver.

[0042] According to a particular feature of the application, the at least one electric heating system is one of a mesh of at least one electrically resistive heating wire arranged between the at least two supply electrodes and at least one electrically resistive heating layer arranged between the at least two supply electrodes.

[0043] In this way, the mesh of at least one electrically resistive heating wire or the at least one electrically resistive heating layer enables the laminated glass to have an anti-icing function by providing Joule heating when the laminated glass is traversed by an electric current from the at least two supply electrodes.

[0044] For example, the laminated glass can comprise, in the case of single-phase supply, a single electric heating system (mesh of electrically resistive wires or electrically resistive layer) arranged between the two supply electrodes.

[0045] The laminated glass can also comprise, in the case of three-phase supply, three electric heating systems (mesh of electrically resistive wires or electrically resistive layer) arranged adjacent to each other between the four supply electrodes, each electric heating system being arranged between a respective pair of the four supply electrodes.

[0046] Each electric supply electrode is in practice an element sufficiently conductive with respect to the electrical elements connected to it to consider that the potential is constant over the entire electrode.

[0047] In the case of a grid of resistive heating wires, it should be noted that the first surface resistivity will not be isotropic, but apparent or equivalent surface resistivity. Indeed, if the current flow occurs in a direction from power supply electrode to power supply electrode, the grid of resistive wires can be compared to a conductive layer having an electrical conductivity. In the orthogonal direction, there is no electrical conductivity.

[0048] The equipotential layer can be grounded to the aircraft either directly via an electrical lead (possibly with an insulating impedance which ensures equipotentiality without the possibility of draining any power current), either indirectly via the power supply electrodes of the electrical heating system, either via the contact between the electrical heating system and the equipotential layer.

[0049] In the case of an electrical heating system with a grid of resistive heating wires, the equipotential layer must have a resistivity significantly higher than that of the grid of metal wires. Because the grid of metal wires generally has a very low resistivity (0.1 to a few Ohms per square), an equipotential layer with a resistivity of 100 Ohms per square to 1 MegaOhm per square can be considered. The grid of resistive wires is applied in contact with the equipotential layer, which forms an electrical shield with respect to the electrical potential of the resistive wires, so that either the local intensity effect associated with the edges of the heating grid, or the size of the resistive wires (a few tens of microns), does not create a local increase in the electrical field in the first sheet on the outer side of the laminated glass.

[0050] In the case of an electrical heating system with a resistive heating layer, the equipotential layer must have a resistivity significantly higher than that of the resistive heating layer. A typical ITO-based layer can have a resistivity ranging from a few Ohms per square to a few hundred Ohms per square. An equipotential layer with a resistivity of a few tens of kOhms to a few tenths of a MegaOhm per square can thus be considered. The equipotential layer thus ensures the continuity of the electrical potential in the plane of the heated resistive layer, without short-circuiting the latter.

[0051] Because the equipotential layer and the resistive heating layer are located on the same internal face of the first sheet on the outer side of the laminated glass, they can be deposited in the same step of the process, which reduces manufacturing costs and eliminates the technical complexity associated with deposited layers on both faces of the first sheet of the laminated glass (in particular, the risk of scratching is eliminated).

[0052] According to another embodiment of the application, the at least one electrical heating system is at least one resistive heating layer, having a flat geometry with its periphery forming a simple closed curve, arranged between at least two power supply electrodes and applied to a portion of the internal face of the first sheet, and the equipotential layer is applied to the remaining portion of the internal face of the first sheet and is made of the same material as the at least one resistive heating layer.

[0053] In this other embodiment, the equipotential layer is applied to the area of the internal face of the first sheet that does not face the at least one resistive heating layer, and thus is able to manage the electric field present at the edges of the resistive heating layer.

[0054] According to a particular feature of this other embodiment of the application, the equipotential layer is made of one of the following: indium tin oxide, gold, silver and aluminum-doped zinc oxide (same as the at least one resistive heating layer).

[0055] According to a first variant of this other embodiment, the equipotential layer comprises at least one of the following: at least one zigzag strip arranged between the at least two power supply electrodes; and at least one comb arrangement, the equipotential layer being made of the same material as the at least one resistive heating layer and electrically connected to the at least one resistive heating layer.

[0056] In this way, the equipotential layer is a layer of the same nature as the resistive heating layer, but whose apparent resistivity is artificially increased by a patterning process (zigzag or comb).

[0057] For example, the equipotential layer electrically coupled to the resistive heating layer can be ablated (for example using a laser) to significantly increase its electrical resistance.

[0058] According to a particular feature of this first variant, the at least one resistive heating layer having a flat geometry with its perimeter forming a simple closed curve, and the equipotential layer, are created on the internal face of the first sheet by: - applying an electrically conductive layer to the internal face of the first sheet; - defining on the electrically conductive layer at least one heating area having a flat geometry with its perimeter forming a simple closed curve; - ablating (in particular by laser ablation) the electrically conductive layer to form the at least one defined heating area as a resistive heating layer; and - ablating (in particular by laser ablation) the electrically conductive layer outside the at least one formed heating area to form, outside the at least one formed heating area, at least one of the at least one zigzag strip and the at least one comb arrangement as an equipotential layer, so that the equivalent resistivity of the equipotential layer is greater than the equivalent resistivity of the formed heating area.

[0059] Once the electrically conductive layer has been applied to the entire surface of the internal face of the first sheet of laminated glass (possibly except for the peripheral edges), the ablation strategy (or mask before deposition) creates a uniform resistive heating layer, and a patterned equipotential layer at the edges of the glass.

[0060] Laser ablation does not change the surface resistivity of the conductive layer. On the other hand, the patterning process / tortuosity of the equipotential layer imposes a longer path and therefore a higher resistance from the power supply electrode to the power supply electrode. This area becomes equivalent to a layer of higher resistivity.

[0061] According to a second variant of this other embodiment, the equipotential layer is electrically insulated from the at least one resistive heating layer and is configured to be directly or indirectly connected to the ground of the mounting structure of the aeronautical laminated glass, and wherein the at least one resistive heating layer and the equipotential layer are created on the internal face of the first sheet by ablation of a conductive layer applied to the internal face of the first sheet, in particular by laser ablation.

[0062] Once the conductive layer has been applied to the entire surface of the internal face of the first laminated glass sheet, possibly except for the peripheral edges, an ablation (or mask before deposition) strategy is used to create an electrical insulation between the resistive heating layer and the equipotential layer. The equipotential layer at the edge of the glass can then be grounded to the aircraft by electrical means such as wires, screen printing, soldering, conductive bonding, etc.

[0063] The invention also relates to the use of an aeronautical laminated glass as described above as a cockpit glass of an aircraft, in particular as a windshield, in particular for medium- and long-haul commercial aircraft, commercial aircraft and tourist aircraft.

[0064] Another object of the invention is an aircraft, such as an airplane or a helicopter, the cockpit glass of which is an aeronautical laminated glass as described above. BRIEF DESCRIPTION OF DRAWINGS

[0065] For a better illustration of the invention, some preferred embodiments are described hereafter by way of example and not limitation, with reference to the appended drawings.

[0066] In these drawings: Figure 1 is a cross-sectional view of an aeronautical laminated glass according to a first embodiment of the invention; Figure 2 is a cross-sectional view of an aeronautical laminated glass according to a second embodiment of the invention; Figure 3 is a cross-sectional view of an aeronautical laminated glass according to a third embodiment of the invention; Figure 4 is a view of the internal face of a first glass sheet of an aeronautical laminated glass according to a fourth embodiment of the invention; Figure 5 is a view of the internal face of a first glass sheet of an aeronautical laminated glass according to a fifth embodiment of the invention; Figure 6 is a front view of a three-phase, delta-connected electrical heating system assembly; Figure 7 is a front view of a three-phase, star-connected electric heating system assembly; and Figure 8 is a schematic view of an aircraft equipped with an aeronautical laminated glass according to the application. DETAILED DESCRIPTION

[0067] With reference to Figure 1 It can be observed that it illustrates an aeronautical laminated glass 1 according to a first embodiment of the application.

[0068] The aeronautical laminated glass 1 can be used as an aircraft cockpit glass and comprises a first sheet 2 arranged on the outer side with respect to the aircraft, two second structural sheets 3a, 3b arranged on the inner side with respect to the aircraft, an adhesive interlayer 4 of the spacer type arranged between the first sheet 2 and the second structural sheet 3a, and another adhesive interlayer 5 of the spacer type arranged between the two second structural sheets 3a and 3b.

[0069] It should be noted that the aeronautical laminated glass 1 can also comprise a single second structural sheet or at least three second structural sheets without departing from the scope of the application.

[0070] The thickness of the first sheet 2 can be between 1 and 5 mm.

[0071] The thickness of each of the second sheets 3a, 3b can be between 4 and 20 mm (in practice, between 4 and 8 mm for mineral glass and between 6 and 20 mm for organic glass).

[0072] Thus, the first sheet 2, the outer face of which is in contact with the outside environment of the aircraft, is a relatively thin surface sheet, unlike the second sheets 3a and 3b which constitute the structural block of the laminated glass 1, they are relatively thick in order to guarantee the mechanical properties required of the laminated glass 1, in particular in the case where the laminated glass 1 must delimit a pressurized volume on the inside of the aircraft. It should be noted that, for example, when the structural block comprises only one glass second sheet 3a, it is considered to be structural as long as its elastic modulus is at least equal to 1500 MPa.

[0073] Each of the first sheet 2 and the second structural sheets 3a, 3b can be either a mineral glass (for example soda-lime, borosilicate, aluminosilicate, etc.) or an organic glass (for example PMMA (polymethyl methacrylate), PC (polycarbonate), etc.). It should be noted that the second structural sheets 3a, 3b can also be made of an organic glass, such as a PET (polyethylene terephthalate) film, without departing from the scope of the application.

[0074] Each of the sandwich-type adhesive interlayer 4 and the sandwich-type other adhesive interlayer 5 may be made of a thermoplastic polymer selected from polyvinyl butyral (PVB), thermoplastic polyurethane (TPU), ethylene-vinyl acetate copolymer (EVA), casting resin, and ionomer resin.

[0075] The thickness of the adhesive intermediate layer 4 may be between 2 and 10 mm, preferably between 3 and 8 mm (depending on the aircraft manufacturer's attachment strategy and the thickness of the outer layer).

[0076] The thickness of the further adhesive intermediate layer 5 of the sandwich type is, for example, between 0.5 and 6 mm, preferably at most 3 mm.

[0077] The laminated glazing 1 rests against an inner retainer 6 ′, which may be an aircraft structure, with spacers 7 interposed therein. The laminated glazing 1 is attached to the aircraft's mounting structure by means of an outer retainer 6 (consisting of a window pane retainer) which, when bolted to the aircraft structure, exerts pressure on the edges of the structural blocks 3 a, 3 b via silicone rubber seals 8.

[0078] The aviation laminated glazing 1 further comprises an electric heating system of the resistive heating layer type 9 , which is arranged between the inner face of the first sheet 2 and the intermediate layer 4 .

[0079] The resistance heating layer 9 is arranged between the two power supply electrodes ( Figure 1 The resistive heating layer 9 is located between the first plate 2 and the second plate 2 (not visible in the figure), and covers the (center) portion of the inner face of the first plate 2. Thus, the resistive heating layer 9 enables the laminated glass 1 to have an anti-icing function by providing Joule effect heating when current from the two power supply electrodes passes through the laminated glass 1.

[0080] The resistance heating layer 9 made of one of indium tin oxide (ITO), gold, silver, and aluminum-doped zinc oxide has a first real surface resistivity.

[0081] The resistive heating layer 9 may have a thickness between 10 and 200 nm and a surface resistivity between 1 and 500 Ohm per square.

[0082] The aviation laminated glazing 1 further comprises an equipotential layer 10 applied to the (peripheral) areas of the inner face of the first sheet 2 , those areas not facing the electric heating system of the resistive heating layer 9 type.

[0083] Therefore, the equipotential layer 10 is encapsulated within the laminated glass 1 so that it is not easily affected by corrosion, dissolution or scratching.

[0084] The equipotential layer 10 is an electrically conductive layer of the same nature as the resistive heating layer 9 (thus, both layers 9 and 10 have the same actual surface resistivity), the equipotential layer 10 is completely electrically insulated from the resistive heating layer 9, and is electrically grounded to the aircraft mounting structure via an electrical lead 11 (optionally having an insulating impedance ensuring equipotentiality without having the ability to drain high currents).

[0085] It should be noted that the equipotential layer 10 can also be connected either directly to the ground potential of the aircraft via other electrical means (such as screen printing, soldering, conductive bonding, etc.), or indirectly to the ground potential of the aircraft via an impedance, without departing from the scope of the invention. The ground connection can also be achieved by connecting to one of the two power electrodes of the resistive heating layer 9.

[0086] Because the equipotential layer 10 and the resistive heating layer 9 are located on the same internal face of the first sheet 2 of laminated glass 1, they can be deposited in the same step of the process, which reduces manufacturing costs and eliminates the technical complexity associated with depositing layers on both faces of the first sheet 2 of laminated glass 1.

[0087] The resistive heating layer 9 and the equipotential layer 10 can be deposited on the inside of the first sheet 2 by means of physical vapor deposition (for example, magnetron field- assisted sputtering at low pressure) or liquid deposition (for example, sol-gel).

[0088] In practice, a single electrically conductive layer is deposited on the internal face of the first sheet 2, then the equipotential layer 10 and the resistive heating layer 9 are created by ablating the deposited electrically conductive layer, so that the equipotential layer 10 is completely insulated from the resistive heating layer 9.

[0089] The equipotential layer 10 has a uniform potential with respect to the charge potential of several tens of kV over its entire surface.

[0090] Reference Figure 2 It can be observed that it illustrates an aeronautical laminated glass 12 according to a second embodiment of the invention.

[0091] Figure 1 The common elements between the first embodiment of the invention and this second embodiment of the invention in are denoted with the same reference numerals, and will not be described in more detail here when they are structurally identical.

[0092] The aeronautical laminated glass 12 according to the second embodiment is identical to the aeronautical laminated glass 1 according to the first embodiment, except that the equipotential layer 10 is a transparent conductive layer applied to the entire internal face of the first sheet 2 (possibly except for the peripheral strip), and ensures that the entire internal face of the first sheet 2 remains at the aircraft ground potential (within a few hundred volts), with the resistive heating layer 9 applied to a (central) portion of the equipotential layer 10.

[0093] Moreover, in this second embodiment, the equipotential transparent conductive layer 10 has a second effective surface resistivity greater than the first effective surface resistivity of the resistive heating layer 9, the equipotential transparent conductive layer 10 being one of: a doped oxide such as indium tin oxide or aluminum zinc oxide, a non-stoichiometric oxide such as tin dioxide, a diamond-like carbon, and silver.

[0094] The ratio between the second and the first actual surface resistivity is greater than or equal to 10, preferably greater than or equal to 100.

[0095] The equipotential transparent conductive layer 10 can be between 10 and 100 nm thick.

[0096] Because the equipotential layer 10 has a higher surface resistivity than the resistive heating layer 9, the equipotential layer 10 is substantially less conductive than the resistive heating layer 9, so that the equipotential layer 10 ensures the continuity of the potential in the plane of the resistive heating layer 9 without short-circuiting the latter, and makes it possible to initiate a surface discharge from the entire periphery of the glass, and to eliminate the local intensity effect at the border of the resistive heating layer 9 which contributes to the dielectric breakdown in the first sheet 2 of laminated glass 1.

[0097] Reference is made to Figure 3 It can be observed that it illustrates an aeronautical laminated glass 13 according to a third embodiment of the application.

[0098] Figure 2 The common elements between the second embodiment of the application and this third embodiment of the application in

[0099] The laminated aeronautical glass 13 according to the third embodiment is identical to the laminated aeronautical glass 12 according to the second embodiment, except that the electrical heating system of resistive heating layer 9 type is replaced by an electrical heating system of resistive heating wire mesh 9' type applied to the transparent equipotential conductive layer 10. The mesh of resistive heating wires 9' is arranged between two supply electrodes (not visible in Figure 3 ) and enables the laminated glass 13 to have an anti-icing function by providing Joule heating when its resistive wires are crossed by the current coming from the two supply electrodes. For example, one of the two supply electrodes can be at 0 V potential and the other of the two supply electrodes can be at 28 V potential.

[0100] It should be noted that the surface resistivity of the heated grid of resistive wires 9' will not be isotropic, but will be considered as an apparent or equivalent surface resistivity, the value of which will be substantially lower than that of the equipotential layer 10. If we consider the current flow in the direction from supply electrode to supply electrode, the grid of resistive heating wires 9' will in fact be understood as a conductive layer having a conductivity. On the other hand, in the orthogonal direction, there will be no conductivity.

[0101] Because the grid of resistive wires 9' generally has a very low resistivity (1 to a few Ohms per square), the equipotential layer 10 can be chosen to have a surface resistivity ranging from 100 Ohms per square to 1 MegaOhm per square.

[0102] The grid of resistive wires 9' is applied in contact with the equipotential layer 10, which forms an electrical shield with respect to the potential of the resistive wires, so that the local intensity effect, either associated with the edges of the heating grid 9' or with the size of the resistive wires (a few tens of microns), does not generate a local increase in the electric field 2 in the first sheet on the outside of the laminated glass 13.

[0103] Reference is made to Figure 4 It can be observed that it illustrates an aeronautical laminated glass 14 according to a fourth embodiment of the application.

[0104] Figure 1 The common elements between the first embodiment of the application and this fourth embodiment of the application in are provided with the same reference numerals and will not be described in more detail here when they are identical in structure.

[0105] Similarly to the first embodiment, the aeronautical laminated glass 14 according to the fourth embodiment comprises a resistive heating layer 9 in the form of a simple polygon, applied to an (central) portion of the inner face of the first sheet 2 of the laminated glass 14 and arranged between two single-phase supply electrodes 15a and 15b, respectively applied to the upper and lower portions of the inner face of the first sheet 2 of the laminated glass 14.

[0106] It should be noted that the resistive heating layer 9 can also have any other flat geometry of which the periphery forms a simple closed curve, without departing from the scope of the application.

[0107] Each of the two supply electrodes 15a and 15b is in practice a rod-shaped element, sufficiently conductive with respect to the electrical elements connected thereto to consider that the potential is constant over the entire electrode.

[0108] Furthermore, in this fourth embodiment, the equipotential layer 10 is applied to the remaining portion of the inner face of the first sheet 2 (except for the peripheral edge of the inner face of the first sheet 2) and consists of two continuous zigzag (or serpentine) strips 16a and 16b arranged between the two power electrodes 15a and 15b, on both sides of the resistive heating layer 9 and forming a continuous path between the power electrodes 15a and 15b that is longer in distance than the path between the two power electrodes 15a and 15b at the level of the resistive heating layer 9 and thus has a higher resistivity. It will be understood that this is not the only way to form a path of higher resistivity through the equipotential layer and that other embodiments are envisaged in the present invention, for example, a different layer or additional layer that varies the resistivity of the equipotential layer with respect to the resistive heating layer.

[0109] The two zigzag strips 16a and 16b forming the equipotential layer 10 are made of the same material as the resistive heating layer 9 (i.e. one of indium tin oxide, gold, silver and aluminium-doped zinc oxide) and are electrically connected to the resistive heating layer 9.

[0110] In this fourth embodiment, the equipotential layer 10 is a layer of the same nature as the resistive heating layer 9, but whose apparent resistivity is artificially increased by a zigzag patterning process.

[0111] In practice, the resistive heating layer 9 and the patterned equipotential layer 10 can be created on the inner face of the first sheet 2 by: - applying a conductive layer to the inner face of the first sheet 2; - defining a heating area (corresponding to the future resistive heating layer 9) on the applied conductive layer; - ablating (in particular by laser ablation) the conductive layer to form the defined heating area as the resistive heating layer 9; and - ablating (in particular by laser ablation) the conductive layer outside the formed heating area to form, on both sides of the resistive heating layer 9, the two zigzag strips 16a and 16b as the equipotential layer 10, so that the equivalent resistivity of the zigzag strips 16a and 16b is greater than the equivalent resistivity of the resistive heating layer 9.

[0112] In this way, a complete or partial electrical insulation between the heated resistive layer 9 and the equipotential layer 10 (i.e. the two zigzag strips 16a and 16b) is achieved by laser ablation of the initial conductive layer.

[0113] Laser ablation does not change the surface resistivity of the conductive layer. On the other hand, the tortuosity (zigzag shape) imposes a longer path and therefore a higher resistance for the equipotential layer 10 from the power supply electrode 15a to the power supply electrode 15b, the equipotential layer 10 thus becoming equivalent to a higher resistivity layer.

[0114] Reference is made to Figure 5 It can be observed that it illustrates an aeronautical laminated glass 17 according to a fifth embodiment of the application.

[0115] Figure 4 Common elements between the fourth embodiment of the application and this fifth embodiment of the application in

[0116] In this fifth embodiment, the patterned equipotential layer 10 no longer consists of two zigzag strips 16a and 16b, but of two comb-like arrangements 18a and 18b extending on both sides of the resistive heating layer 9, the comb-like patterned equipotential layer 10 thus being equivalent to a higher resistivity layer.

[0117] In practice, the patterned equipotential layer 10 can be created on the inner face of the first sheet 2 by: - applying a conductive layer to the inner face of the first sheet 2; - defining heating areas (corresponding to future resistive heating layers 9) on the applied conductive layer; and - ablation (in particular by laser ablation) of the conductive layer outside the defined heating areas to form, on both sides of the resistive heating layer 9, two comb-like arrangements 18a and 18b as equipotential layer 10, so that the equivalent resistivity of the comb-like arrangements 18a and 18b is greater than the equivalent resistivity of the resistive heating layer 9.

[0118] Although in each of the first to fifth embodiments illustrated in Figures 1 to 5 Although in each of the first to fifth embodiments illustrated in

[0119] For example, Figure 6 An electrical heating system assembly with a three-phase power supply 19 arranged in a triangular arrangement is illustrated, comprising three electrical heating systems 9a, 9b and 9c (for example, three resistive heating layers) arranged adjacent between four power supply electrodes 20a, 20b, 20c and 20d.

[0120] The first electrode 20a is connected to the lower part of the first electric heating system 9a. The second electrode 20b is connected to the upper part of the first and second electric heating systems 9a and 9b. The third electrode 20c is connected to the lower part of the second and third electric heating systems 9b and 9c. The fourth electrode 20d is connected to the upper part of the third electric heating system 9c. And, the first and fourth electrodes are electrically connected by an electric lead 21.

[0121] In addition, for example, Figure 7 Another electric heating system assembly is illustrated with a three-phase power supply 22 arranged in a star arrangement, comprising three electric heating systems 9a, 9b and 9c (e.g. three electric resistance heating layers) arranged adjacent between four power supply electrodes 23a, 23b, 23c and 23d.

[0122] The first electrode 23a is connected to the lower part of the first electric heating system 9a. The second electrode 23b is connected to the lower part of the second electric heating system 9b. The third electrode 23c is connected to the lower part of the third electric heating system 9c. Finally, the fourth electrode 23d is connected to the upper part of the three electric heating systems 9a, 9b and 9c.

[0123] The invention also relates to the use of one of the above-described aeronautical laminated glasses 1, 12, 13, 14 and 17 as a cockpit glass of an aircraft, in particular as a windshield, in particular for medium- and long-haul commercial aircraft, commercial aircraft and tourist aircraft.

[0124] Another object of the invention is an aircraft, such as an airplane or a helicopter, the cockpit glass of which is one of the above-described aeronautical laminated glasses 1, 12, 13, 14 and 17.

[0125] Figure 8 An aircraft 24 (here an airplane, but the invention also applies to a helicopter) is schematically illustrated, the aircraft being equipped with a laminated glass 1 according to the invention on its windshield.

[0126] Of course, the invention is not limited in this respect and the laminated glass according to the invention can be applied to one or more of the openings (windshield, side window, door window) or optical devices (light) of the aircraft without departing from the scope of the invention.

[0127] It should be understood that the particular embodiments described just above are illustrative and non-limiting, and that further modifications can be added without departing from the scope of the invention.

Claims

1. An aeronautical laminated glass (1; 12; 13; 14; 17) comprising a first sheet (2) on the outer side, at least one second structural sheet (3a, 3b) on the inner side and an interlayer (4) arranged between the first sheet (2) and the at least one second structural sheet (3a, 3b), the first sheet (2) and the at least one second structural sheet (3a, 3b) being made of at least one of inorganic glass and organic glass, the aeronautical laminated glass (1; 12; 13; 14; 17) further comprising at least one electric heating system (9; 9') arranged facing the inner face of the first sheet (2), characterized in that, The aeronautical laminated glass (1; 12; 13; 14; 17) further comprises an equipotential layer (10) applied to the inner face of the first sheet (2).

2. The aeronautical laminated glass (12; 13) according to claim 1, characterized in that, The at least one electric heating system (9; 9') is applied to the equipotential layer (10) and has a first actual or equivalent surface resistivity, the equipotential layer (10) having a second actual or equivalent surface resistivity greater than the first actual or equivalent surface resistivity.

3. The aeronautical laminated glass (12; 13) according to claim 2, characterized in that, The ratio between the second actual or equivalent surface resistivity and the first actual or equivalent surface resistivity is greater than or equal to 10, preferably greater than or equal to 100.

4. The aeronautical laminated glass (12; 13) according to either of Claims 2 and 3, characterized in that, The equipotential layer (10) is a transparent conductive layer configured to be directly or indirectly connected to the ground of the mounting structure of the aeronautical laminated glass (12; 13).

5. The aeronautical laminated glass (12; 13) according to claim 4, characterized in that, The transparent conductive layer is made of one of the following: a doped oxide, such as indium tin oxide or aluminum zinc oxide; a non-stoichiometric oxide, such as tin dioxide; a diamond-like carbon; and silver.

6. The aeronautical laminated glass (12; 13) according to any one of claims 2 to 5, characterized in that, The at least one electric heating system is one of a mesh of at least one electrically resistive heating wire (9') arranged between at least two supply electrodes (15a, 15b) and at least one electrically resistive heating layer (9) arranged between at least two supply electrodes (15a, 15b).

7. - The aeronautical laminated glass (1; 14; 17) according to claim 1, characterised in that, The at least one electric heating system is at least one electrically resistive heating layer (9) having a flat geometry with its perimeter forming a simple closed curve, arranged between at least two supply electrodes (15a, 15b) and applied to a portion of the inner face of the first sheet (2), and the equipotential layer (10) is applied to the remaining portion of the inner face of the first sheet (2) and is made of the same material as the at least one electrically resistive heating layer (9).

8. The aeronautical laminated glass (1; 14; 17) according to claim 7, characterized in that, The equipotential layer (10) is one of indium tin oxide, gold, silver and aluminum-doped zinc oxide.

9. The aeronautical laminated glass (14; 17) according to claim 7 or 8, characterized in that, The equipotential layer (10) comprises at least one of: at least one zigzag strip (16a, 16b) arranged between the at least two supply electrodes (15a, 15b); and at least one comb arrangement (18a, 18b), the equipotential layer (10) being electrically connected to the at least one electrically resistive heating layer (9).

10. The aviation laminated glass (14; 17) according to claim 9, characterized in that The at least one electrically resistive heating layer (9) having a flat geometry with its perimeter forming a simple closed curve and the equipotential layer (10) are created on the inner face of the first sheet (2) by: - applying a conductive layer to the inner face of the first sheet (2); - defining at least one heating area having a flat geometry with its perimeter forming a simple closed curve on the conductive layer; - ablating the conductive layer, in particular by laser ablation of the conductive layer, to form the at least one defined heating area (9) as an electrically resistive heating layer; and - ablating the electrically conductive layer outside the formed at least one heating zone, in particular by laser ablating the electrically conductive layer, to form at least one of at least one zigzag strip (16a, 16b) and at least one comb arrangement (18a, 18b) as an equipotential layer (10) outside the formed at least one heating zone, such that the equivalent resistivity of the equipotential layer (10) is greater than the equivalent resistivity of the formed heating zone.

11. The aeronautical laminated glass (1) according to claim 7 or 8, characterized in that, The equipotential layer (10) is electrically insulated from the at least one electrically resistive heating layer (9) and is configured to be directly or indirectly connected to a ground of a mounting structure of the aeronautical laminated glass (1), and wherein the at least one electrically resistive heating layer (9) and the equipotential layer (10) are created on the inner face of the first sheet (2) by ablating electrically conductive layers applied to the inner face of the first sheet (2), in particular by laser ablation.

12. Use of the aeronautical laminated glass (1; 12; 13; 14; 17) according to any one of claims 1 to 11 as a cockpit glass of an aircraft, in particular as a windshield, in particular for medium- and long-haul commercial aircraft, commercial aircraft and tourist aircraft.

13. An aircraft, the cockpit glass of which is an aeronautical laminated glass (1; 12; 13; 14; 17) according to any one of claims 1 to 11.

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