Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B17/00—Layered products essentially comprising sheet glass, or glass, slag, or like fibres
  • B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
  • B32B17/10—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin
  • B32B17/10005—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing
  • B32B17/10009—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing characterized by the number, the constitution or treatment of glass sheets
  • B32B17/10036—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing characterized by the number, the constitution or treatment of glass sheets comprising two outer glass sheets
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60J—WINDOWS, WINDSCREENS, NON-FIXED ROOFS, DOORS, OR SIMILAR DEVICES FOR VEHICLES; REMOVABLE EXTERNAL PROTECTIVE COVERINGS SPECIALLY ADAPTED FOR VEHICLES
  • B60J1/00—Windows; Windscreens; Accessories therefor
  • B60J1/002—Windows; Windscreens; Accessories therefor with means for clear vision, e.g. anti-frost or defog panes, rain shields
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B17/00—Layered products essentially comprising sheet glass, or glass, slag, or like fibres
  • B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
  • B32B17/10—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin
  • B32B17/10005—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing
  • B32B17/10165—Functional features of the laminated safety glass or glazing
  • B32B17/10174—Coatings of a metallic or dielectric material on a constituent layer of glass or polymer
  • B32B17/1022—Metallic coatings
  • B32B17/10229—Metallic layers sandwiched by dielectric layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B17/00—Layered products essentially comprising sheet glass, or glass, slag, or like fibres
  • B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
  • B32B17/10—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin
  • B32B17/10005—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing
  • B32B17/10165—Functional features of the laminated safety glass or glazing
  • B32B17/10339—Specific parts of the laminated safety glass or glazing being colored or tinted
  • B32B17/10348—Specific parts of the laminated safety glass or glazing being colored or tinted comprising an obscuration band
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B17/00—Layered products essentially comprising sheet glass, or glass, slag, or like fibres
  • B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
  • B32B17/10—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin
  • B32B17/10005—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing
  • B32B17/1055—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing characterized by the resin layer, i.e. interlayer
  • B32B17/10761—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing characterized by the resin layer, i.e. interlayer containing vinyl acetal
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C17/00—Surface treatment of glass, not in the form of fibres or filaments, by coating
  • C03C17/34—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions
  • C03C17/36—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C17/00—Surface treatment of glass, not in the form of fibres or filaments, by coating
  • C03C17/34—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions
  • C03C17/36—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal
  • C03C17/3602—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal the metal being present as a layer
  • C03C17/3668—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal the metal being present as a layer the multilayer coating having electrical properties
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C17/00—Surface treatment of glass, not in the form of fibres or filaments, by coating
  • C03C17/34—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions
  • C03C17/36—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal
  • C03C17/3602—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal the metal being present as a layer
  • C03C17/3681—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal the metal being present as a layer the multilayer coating being used in glazing, e.g. windows or windscreens
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B3/00—Ohmic-resistance heating
  • H05B3/84—Heating arrangements specially adapted for transparent or reflecting areas, e.g. for demisting or de-icing windows, mirrors or vehicle windshields
  • H05B3/86—Heating arrangements specially adapted for transparent or reflecting areas, e.g. for demisting or de-icing windows, mirrors or vehicle windshields the heating conductors being embedded in the transparent or reflecting material
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
  • H05B2203/013—Heaters using resistive films or coatings

Definitions

• the present invention relates to heated "automobile” glazings. More specifically, the invention relates to glazings comprising a heating assembly consisting of thin conductive layers and dielectric layers applied to the glass substrate. Heating "automotive" glazings comprising a set of thin conductive layers, are well known. Glazing of this type is especially proposed for implementation in windshields. In these applications the conductive layers are mainly used as an infrared filter to prevent heating of vehicles exposed to solar radiation. The layer systems used must meet the optical requirements specific to these uses. For windshields, a light transmission of at least 70% is required. The presence of these layer systems should not lead to undesirable colorations especially in reflection and this regardless of the angle at which the glazing is observed.
• the layer systems in question traditionally include one or more thin metal layers that develop their power by joule effect.
• the strength of the layers depends on their thickness.
• the voltage applicable in vehicles is regulated. It does not normally exceed 14v. Under these conditions it goes without saying that the power is limited by the intensity that can pass in these layers. Intensity is itself a function of resistance. Consequently, the tendency is to increase the thickness of the conductive metal layers, but this thickness is limited by the need to maintain a regulatory light transmission.
• the inventors have tried to find glazing structures having a set of properties satisfying all these conditions.
• the inventors have thus made laminated windshields whose glass thicknesses do not exceed 3.8 mm and preferably are less than 3.5 mm and may even be smaller than 3.2 mm.
• Such windshields are advantageously obtained by the combination of glass sheets of different thicknesses.
• the thicker leaves are normally facing outwards. This arrangement improves in particular the mechanical resistance to "gravel".
• the thinnest leaves In practice the implementation of the sheets requires that the thinnest leaves remain conveniently manipulated, whether manually or by mechanical means robots.
• the thinnest leaves should also lend themselves without undue difficulty to the treatments leading to the products according to the invention. This is particularly the case of treatments that cause an increase in their temperature. This is for example the formation of functional layer systems. Deposits Even if the temperatures remain relatively low, they can lead to deformations leading to unevenness of the layers.
• the shaping operations of the sheets and their subsequent assembly also require a minimum of initial stiffness, especially for the conveying and the good positioning of the sheets.
• the thickness of the thinnest sheets used is not less than 0.8 mm, and preferably not less than 1.0 mm.
• the glazings according to the invention comprise at least one glass sheet whose thickness is not greater than 1, 6 mm and advantageously is not greater than 1.4 mm.
• the leaves associated with the thinnest sheets have a thickness which is not greater than 2.5 mm, and is preferably less than 2.1 mm. and may be equal to or less than 1.9mm.
• the assembly is made by means of a thermoplastic sheet of material traditionally used for these laminated assemblies. These are mainly polyvinyl butyral (PVB) sheets, but also ethylene vinyl acetate (EVA) or polyurethane (PU). This material has a much lower density than glass. A change in the thickness of the intermediate sheet to lighten the glazing does not offer significant improvement especially as this thickness must provide resistance against the ejection of sufficient passengers.
• the traditional thicknesses of the PVB sheets used in automotive glazings are at least 0.38 mm and most often 0.76 mm for single interlayers. Separate products are sometimes offered to integrate additional functions.
• HUD head up display
• the spacers usually have a variable thickness in the height of the windshield.
• the production of thin laminated glazing also has some singularities as regards the techniques used for their forming.
• the lightening of the sheets does not facilitate their handling due in particular to reduced rigidity.
• the use of sheets of different thicknesses leads to the need to adapt the techniques that are dependent on the thermal properties of the sheets. These do not absorb the energy used to drive them in the state of softening proper to their shaping.
• the inventors have further progressed in the properties of the heating layer systems, reaching even lower strengths.
• the inventors have reached layer systems whose resistance may be less than ⁇ / D and may even be equal to or less than 0.8 ⁇ /
• the glazings having these properties also retain a satisfactory light transmission, are not or very slightly colored in reflection whatever the angle of observation, and withstand without altering the heat treatment shaping.
• the heating layer system is in contact with the spacer, that is to say in position 2 or 3 according to the usual designation, the position 1 corresponding to the face of the glazing facing the outside of the vehicle.
• the presence of the heating layer system in position 3 promotes the warming of the face of the window facing the passenger compartment.
• the function of eliminating the fog, or even frost formed by extremely low temperatures is substantially improved. It is all the more so since the glass sheet turned inwardly is advantageously the thinnest, and as a result the thermal conduction is increased towards the passenger compartment.
• the arrangement of the layer system in position 2 leads to the superposition on the same side of the glass sheet of this layer system and the enameled edges used to conceal the gluing of the layers. glazing.
• This superposition of an enamel and the layer system requires very controlled conditions of preparation of these glazings to avoid defects that may result from the contact of these two kinds of materials. It is also necessary to add in the superposition, the conductive elements ("busbar") supplying the layer system.
• the masking enamels are usually "fired" during the windshield shaping step to perform a single heat treatment operation.
• the cooking operation operated in the at the same time that the formatting is only feasible if the functional layers are not on the face carrying the enamel.
• the layer system must be in position 3. If the layer system is placed in position 2, the enamel must be baked before the deposition of the functional layer system. But even in this case it must be ensured that the heating layer system has a good electrical continuity between the part applied to the enamelled strips and that which extends over the part of the glazing which is not coated with enamel.
• the power supply is provided by conductors "busbar" resistance as low as possible not to lead to the development of a Joule effect sensitive and therefore a lowering of the voltage available for conductive layer systems.
• the busbars are arranged on two opposite edges of the glazing corresponding to the smallest distance. In the most common windscreen configurations, this smallest distance corresponds to their height. This height tends to increase, the disposition of the busbars on the sides of the windshields can become equal or even lower. In this case the busbars will be arranged on the sides.
• the busbars used according to the invention are of traditional materials for this use. It is very thin metal ribbons, including copper ribbons. It is even more frequently conductive enamel bands, including silver-based. Whatever the nature or the position of the busbars on the windshield, these conductors are masked towards the outside of the vehicle by the enamelled strips which also hide the traces of bonding. It is also traditional to ensure that the layer systems do not extend to the edge of the glazing to avoid alteration in contact with atmospheric moisture. So that the limit of these functional layers is not perceptible it is located preferably behind these masking enamels, which, at least in places, can be made in the manner of a gradient of dots from a completely coated area of the enamel at the edge of the glazing, until the part perfectly devoid of this enamel.
• the total amount of silver per unit area remains limited in particular to not excessively reduce the light transmission. But the total allowable quantity is a function of the quality of the composition of the system as a whole.
• the total amount of silver is not less than 300mg / m 2 and preferably is not less than 320mg / m 2 and most preferably is greater than 350mg / m 2 .
• the total amount of silver per unit area can reach 400mg / m 2 or even 450mg / m 2 .
• each of the silver layers comprises a minimum of 100 mg / m 2 , and advantageously greater than 110 mg / m 2 .
• each silver layer comprises at most 160mg / m 2 , and preferably at most 150mg / m 2 .
• Transparent dielectric layers are well known in the applications under consideration. Adequate materials are numerous and it is not useful to list them here. These are generally oxides, oxy-nitrides or metal nitrides. Among the most common, there may be mentioned as examples SiO 2 , TiO 2 , SnO 2 , ZnO, ZnAlOx, Si 3 N 4 , AlN, Al 2 O 3 , ZrO 2 , Nb 2 O 5 , YO x TiZrYOx, TiNbOx , HfOx, MgOx, TaOx, CrOx and Bi 2 O 3 , and mixtures thereof.
• AZO refers to a zinc oxide doped with aluminum or to a mixed oxide of zinc and aluminum, preferably obtained from a ceramic cathode formed by the oxide to be deposited in an atmosphere neutral or slightly oxidizing.
• ZTO or GZO refer respectively to mixed oxides of titanium and zinc or zinc and gallium, obtained from ceramic cathodes in a neutral atmosphere or slightly oxidizing.
• TXO refers to titanium oxide obtained from a titanium oxide ceramic cathode.
• ZSO refers to a zinc-tin mixed oxide obtained either from a metal cathode of the alloy deposited under an oxidizing atmosphere or from a ceramic cathode of the corresponding oxide in a neutral or slightly oxidizing atmosphere.
• TZO, TNO, TZSO, TZAO or TZAYO refer respectively to mixed titanium-zirconium, titanium-niobium, titanium-zirconium-silicon, titanium-zirconium-aluminum or titanium-zirconium-aluminum-yttrium oxides, obtained from ceramic cathodes, either in neutral or slightly oxidizing atmosphere.
• the materials for entering the composition of the systems used according to the invention are chosen according to multiple criteria. They must be sufficiently transparent to the thicknesses that their refractive index commands.
• At least one of the dielectric layers is based on a zinc-tin mixed oxide containing at least 20%, and preferably at least 40% by weight of tin, for example about 50% to form Zn 2 SnO 4 .
• This oxide is very useful as a dielectric coating in a stack capable of undergoing heat treatment.
• the lower dielectric coating disposed between the glassy material sheet and the first silver reflective layer comprises at least one zinc-tin mixed oxide containing at least 20% by weight of tin, and the outer dielectric coating also comprises at least one zinc-tin mixed oxide containing at least 20% by weight of tin.
• the dielectric layer disposed under one or under each silver reflecting layer is a layer based on a zinc oxide, optionally doped for example with aluminum, magnesium or gallium. This layer is in direct contact with the layer (s) of silver.
• the zinc oxide-based layers can have a particularly favorable effect on the stability and corrosion resistance of the functional layer. They are also favorable to the improvement of the conductivity.
• the mixed oxides of zinc and tin offer the required stability during heat treatments, it has appeared more advantageous for the conductivity of the silver layers to be formed on a zinc oxide layer with essentially no other constituent than those present possibly in the state of impurities.
• the proportion by weight of these elements present in the zinc oxide remains in all cases less than 5% by weight and is advantageously less than 3%, and particularly preferably less than 1%.
• zinc oxide has different crystalline growths depending on whether one operates with a mixed oxide or an almost pure oxide. Mixed oxides would be less sensitive to changes at high temperature, the structure being less crystalline, or if we want more amorphous. This is what X-ray crystallographic analyzes seem to show. The traditional peaks of zinc crystals are less intense.
• the promoting effect of the layer of silver related to the presence of the substantially pure zinc oxide layer and the thermal stability of this layer can be simultaneously provided as long as the layer of question is not too thick.
• the zinc oxide layer on which the silver layer is deposited is not of a thickness greater than 110 ° and preferably not greater than 90 °.
• This layer to improve the properties of the silver layer must nevertheless have a certain thickness that achieves the desired crystallinity.
• the substantially pure zinc oxide layer has a thickness of at least 40 °, and preferably at least 50 °.
• these layers are thin metal layers optionally partially oxidized, whose role is to prevent oxidation of the underlying layer by oxidizing themselves. These layers should be sufficiently thin and of as transparent material as possible so as not to significantly diminish the light transmission of the whole. To achieve the best possible transmission these layers are preferably completely oxidized in the heat treatment operations.
• the metals most commonly used to form these barrier layers include Ti, Zn, Al, Nb and NiCr alloys.
• the thicknesses of the barrier layers are not usually greater than 8 nm, and most often are less than or equal to 6 nm.
• the thickness is preferably less than 4 nm.
• FIG. 1 is a schematic representation of a section of a glazing according to the invention.
• FIG. 2 is a representation of a glazing according to the invention having another structure
• FIG. 3 shows in section a layer system used in the composition of a glazing according to the invention
• FIG. 4 is a graph showing the evolution of a deicing operation as a function of time, for a glazing unit according to the invention, according to the position of the heating system;
• FIG. 5 is a graph illustrating the power developed as a function of the resistance / square of the layer system, and the distance between the busbars;
• FIG. 6 is a graph showing the influence of the thickness of the ZnO layer on the quality of the silver layers;
• FIG. 7 illustrates the stability of the neutrality in reflection of coated glass sheets, by varying the angle of observation relative to the normal.
• the glazings both comprise a set of two glass sheets 1, 2, joined by a thermoplastic interlayer sheet 3.
• the glass sheets are of different thickness. If this structure is advantageous, it is not exclusive of structures in which the sheets have identical thicknesses. The choice of different thicknesses answers questions of optimization of the total thickness, taking into account the respective distinct roles of each of these sheets.
• the glazings according to the invention thus preferably comprise the thickest sheet facing the outside of the vehicle.
• the thickest sheet is sheet 1.
• a system of heating layers and infrared filtering is shown generally at 4.
• the layer system is in position 3, between sheet 2 and tab 3.
• Busbars are schematized in 5.
• Busbars are located on both sides of the glazing. Their position and dimensions are chosen to establish a current in the layer system, over the entire surface of the glazing extending between these busbars. As mentioned before, the busbars are arranged in the smallest dimension of the glazing to maintain the highest power. high possible given the available voltage applied, and the resistance of the layer system.
• the busbars 5 are chosen to provide as little electrical resistance as possible in order to have the highest voltage for feeding the layer system 4.
• glazings such as windshields are glued to the bodywork on their side facing the cockpit, ie in position 4.
• strips dark enamel 6 are arranged opposite the locations of the dashes of glue.
• the busbars 5 being located at the periphery of the glazing so as not to obscure the viewing zone of the glazing, they are located as shown in the areas also covered by the enamelled strips 6, and are simultaneously masked by these enamelled strips 6.
• the enamelled strips 6 are arranged in position 2 on the sheet 1.
• the layer system 4 is applied in position 3 on the sheet 2.
• the separation of enamels and functional layers facilitates the shaping possibly simultaneous of the two leaves in bending or tempering treatment. Even if the positions 2 and 3 of the sheets are face to face during this treatment, it is possible without too restrictive precautions to avoid alterations caused by the contact of the enamel 6 and the layer system 4, and / or that busbars. For this various measures are possible.
• enamelled areas can be "precooked” to remove all the solvents initially contained in the pasta applied. This precooking also solidifies the enamelled strips that are no longer "sticky” to the superposition of the glass sheets during the bending heat treatment.
• enamelled strips 6 can be interpose a powder nonstick which is removed after the thermal shaping of the glass sheets.
• Figure 2 shows another structure.
• the enamelled strips 6 and the heating layer system 4 with the busbars 5, are all on the face 2 of the outer sheet 1.
• the layer system 4 is applied to the sheet 1 after the enamelled strips 6 were precooked.
• the busbars as before are applied to the previously constituted layer system.
• FIG. 3 is an example of a heating layer system that can be used according to the invention.
• the system is presented applied on a glass sheet as for example in the structure of FIG.
• the illustrated system comprises three layers 7, 8, 9, infrared reflecting conductors. It is most often metal layers based on silver.
• the silver is pure, but it may be doped with a few percent of palladium, aluminum or copper, for example from 0.1 to 10 at%, preferably from 0.3 to 3.0%.
• the silver layers are three in number to achieve a resistance / square as low as possible without compromising the optical properties, including the reflection and neutrality of the color in reflection regardless of the angle of observation.
• Dielectric layers complete the system between the glass substrate 2 and the first silver layer 7, between the silver layers 7 and 8 on the one hand and 8 and 9 on the other hand, finally above the layer of silver. money 9.
• the silver layers are covered with a barrier layer (10, 11, 12) composed of a metal that may be partially oxidized.
• the barrier layers are very thin and protect the silver against oxidation by oxidizing themselves in the successive reactive deposits of the superimposed dielectric layers, and in thermal shaping treatments.
• the barrier layers are advantageously titanium, because of the good transparency of the titanium oxide layers, but other metals are also possible which are traditionally used for these layers.
• these layers contribute significantly to the quality and structure of the silver layers.
• These layers are based on zinc oxide.
• the layers in question may optionally be composed of a mixed oxide of zinc and tin with a limited proportion of tin to stabilize the structure of the layer, and prevent its modification especially during heat treatments.
• substantially pure zinc oxide layers that is to say an oxide whose foreign components are not greater than 5%, preferably not more than 3% and more particularly not more than 1% by weight.
• the presence of these layers of zinc oxide when they are of well-defined thicknesses, leads to layers of silver offering the best conductivity.
• the systems also comprise at least one dielectric layer supplementing the "dereflective" system between the glass sheet (16) and the first layer of silver, between the silver layers (17, 18), and above the third layer of silver (19).
• the preferred additional layer is a zinc-tin mixed oxide layer, the proportions of which are advantageously of the order of 50% by weight of each of the constituent oxides.
• the system still often comprises a protective surface layer (20) advantageously still an oxide of good mechanical strength such as titanium oxide. This surface layer is relatively thin to limit its influence in the interferential system.
• the infrared reflecting layers, but also the dielectric layers associated with them must satisfy defined ratios to constitute the most effective interference systems.
• the reports in question are detailed in particular in the BE2010 / 0311 application, filed on May 25, 2010 by the applicant, which application is incorporated by reference, in particular for the most advantageous conditions as regards the thickness ratios of the different layers.
• a first example of a particularly preferred reflective system is constituted in the following manner in which the thicknesses are expressed in angstroms: glass / Zn 2 SnC> 4 / ZnO / Ag / Ti / Zr ⁇ SnCyZnO / Ag / Ti / Zr ⁇ SnCyZnO / Ag / Ti / Zn 2 SnC> 4 / Ti0 2 ep. 310 70 141 20 660 80 144 30 630 80 131 20 293 54 ex.l
• the system is applied to a standard 1.25mm thick "float" glass sheet.
• the sheet is subjected to heat treatment at 650 ° C for 8 minutes.
• the optical properties are measured on the glass side (face 1 of the glazing) before assembly in the laminated glazing.
• the illuminant is D65, under 10 ° for normal incidence.
• the light transmission (measured as the other optical quantities according to the EN410 standard) TL is 78.6%
• the reflection RL is 6.3%
• the colorimetric data (expressed in the CIELAB 1976 system) are L * 91, l , a * 0.0, b * 2.6.
• the resistance measurements made on the glazing lead to a value of 0.85 ⁇ / ⁇ .
• the available power is then about 410w / m 2 .
• the resistances of these layer assemblies are respectively 0.85 ⁇ / ⁇ and 0.9 ⁇ / D.
• the reflection color variation was established according to the angle of observation. This property is sensitive for automotive glazing especially for windshields. These are in effect both very inclined and bulging. It is highly desirable that the appearance of these windows is as neutral as possible regardless of the position of the observer and that this appearance is evenly uniform for the entire glazing although it is seen from different angles simultaneously according to the part observed.
• the colorimetric coordinates L *, a * and b * as well as the variation AC * (which is the square root of the squares of the variations of a * and b *) are expressed as a function of the angle of observation. The angle is indicated as normal to the glazing.
• Another layer system according to the invention is the following, the thicknesses as previously being expressed in angstrom: glass / AlN / AZO / Ag / ZnAl / AZO / Ag / ZnAl / AZO / Ag / ZnAl / AZO / A1N
• AZO denotes the ZnAlOx layer with 5 atomic% of aluminum relative to the ZnAl set; ZnAl barriers are a 12 atomic% Al alloy.
• the formation of the frost layer is conducted in a refrigerated chamber at -18 ° C.
• the amount of water applied to the surface of the sample is 0.5 kg / m 2 .
• the percentage of de-iced surface, the sample being maintained in the refrigerated chamber, is measured as a function of the application time of the power adjusted to 410w / m 2 'by adjusting the voltage to the dimensions of the sample.
• the results are shown in FIG. 4.
• the curves correspond to positions 2 and 3 of the heating layer system. It can be seen that the defrost takes place more quickly in the case of the heating layer system placed in position 2.
• the gain is of the order of one minute in obtaining the complete defrosting. This difference obviously comes from mode of conduction of heat in the glazing.
• the proximity of the heat source favors the heating of the face to defrost.
• FIG. 5 schematically illustrates the incidence of available power as a function of the resistance of the layer system for three values thereof, and the distance between the busbars on the glazing. If with a resistance of 0.85 / ⁇ , as in the previous case, the distance can be greater than 75cm to have a power of the order of 400w / m 2 , we see that this distance decreases very quickly when the resistance rises. Thus for a resistance of 1.5 ⁇ / ⁇ this distance, in other words the height of the effectively defrosted windshield is only about 60 cm.
• Figure 6 shows the influence of the thickness of the zinc oxide layer on the performance of the silver layers in the system described above by simultaneously varying the three layers of zinc oxide present.
• the graph represents the change in quality of silver, which is defined as the product of the square resistance expressed in ohm, by the amount of silver per unit area expressed in milligrams per square meter.

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