Curved laminated glazing

Abstract

The invention relates to curved laminated glazing (10) comprising a first glass sheet (11) comprising a second main face (F2), and a second glass sheet (12) comprising a first main face (F3), the second main face (F2) of the first glass sheet (11) being adhesively bonded to the first main face (F3) of the second glass sheet (12) by means of a lamination interlayer (14). The second main face (F2) of the first glass sheet (11) comprises an enameled zone (Z1), in which the second main face (F2) is coated with a coating successively comprising a first enamel layer (15), a stack of thin layers (16), then a second enamel layer (17), and a non-enameled zone (Z2), in which the second main face (F2) is at most coated only with said stack of thin layers (16).

Description

Curved laminated glass

[0001] The invention relates to the field of glazing, more particularly glazing for vehicles, especially automobiles. It concerns more specifically a curved laminated glass and its manufacturing process.

[0002] Laminated glass is glazing in which two sheets of glass are bonded together with an adhesive interlayer. This interlayer helps to hold glass fragments together in case of breakage, but also provides other functionalities, particularly in terms of burglary resistance and improved acoustic properties.

[0003] These windows often include coatings of various types, designed to impart different properties.

[0004] Layers of enamel, usually black and opaque, are often applied to part of the glazing, generally as a peripheral band designed to conceal and protect against ultraviolet radiation the polymer seals used to fix and position the glazing to the body frame. Enameled areas also conceal the mounting points for the interior rearview mirror and various connectors and sensors.

[0005] In laminated glass, these enamel layers are generally arranged on surface 2, with surfaces traditionally numbered starting from the surface intended to face the exterior of the vehicle. Surface 2 is therefore in contact with the interlayer. The aesthetic appearance of the enamel layer as seen from the outside of the vehicle is of particular importance to car manufacturers. The enamel is generally obtained by firing a composition containing a glass frit and pigments at temperatures above 500°C. A glass frit consists of fine particles of low-melting-point glass, which, under the effect of a firing heat treatment, softens and adheres to the glass sheet. This forms a mineral layer, generally opaque, with high chemical and mechanical resistance, adhering perfectly to the glass while retaining the pigment particles.The baking stage is usually carried out simultaneously with the curving of the glass sheet.

[0006] In the context of laminated glass manufacturing, the two glass sheets of the glazing are often curved together, with the glass sheet intended for the interior of the vehicle generally positioned on top of the other glass sheet, which carries the enamel coating. In other processes, each glass sheet is curved separately. In all cases, the enamel must possess non-stick properties to prevent any adhesion between the two glass sheets or between the glass sheet and the curving tools during the bending process. To achieve this, bismuth-containing enamels are typically used; these are obtained from glass frits containing bismuth oxide.

[0007] Coatings, generally in the form of stacked thin layers, can also be present on one of the glass panes of laminated glazing. These may include electrically conductive layers, which can provide two types of functionality. Firstly, when current is supplied, these electrically conductive layers can dissipate heat through the Joule effect. These are then heating layers, useful, for example, for defrosting or demisting. Secondly, these layers, by reflecting infrared radiation, offer solar control or low-emissivity properties. These layers are therefore valued for improving thermal comfort or for the energy savings they provide by reducing heating or cooling consumption.

[0008] These layer stacks are generally placed on surface 3 of the laminated glass, and therefore also in contact with the lamination interlayer. However, it can be advantageous to place the enamel layer and the layer stack on the same sheet of glass, and thus on the same surface of the glass sheet in question, so that these coatings are protected within the laminated glass.

[0009] The inventors, however, pointed out that in this latter case, the presence of the stacked thin films was likely to create defects. When the two glass panes of the glazing are frequently curved together, material transfer from the stack to the opposite glass pane can be observed during the curving process. When each glass pane is curved separately, material transfer from the stack to the curving tools, such as presses, can occur, leading to contamination of these tools and a risk of transfer to the panes that are subsequently curved. These defects are particularly visible in the case of glazing that can be illuminated, as they create a bluish halo. The invention aims to remedy these problems.

[0010] To this end, the invention relates to a curved laminated glazing comprising: - a first sheet of glass comprising a first main face and a second main face, and - a second sheet of glass comprising a first main face and a second main face, the second main face of the first sheet of glass being bonded adhesively to the first main face of the second sheet of glass by means of a lamination interlayer, and the second main face of the first sheet of glass comprising: - an enameled area, in which the second main face of the first sheet of glass is coated by a coating comprising successively a first layer of enamel, a stack of thin layers, then a second layer of enamel, and - an un-enameled area, in which the second main face of the first sheet of glass is at most coated only with said stack of thin layers.

[0011] Another object of the invention is a method for obtaining laminated curved glass according to the invention. Such a method comprises: - supplying a first sheet of glass comprising a first principal face and a second principal face, then - depositing a first layer of enamel on an area, called the enameled area, of the second principal face of the first sheet of glass, said second principal face of the first sheet of glass being devoid of said first layer of enamel in an area called the un-enameled area, then - depositing a stack of thin layers on the second face of the first sheet of glass, in at least a part of the enameled area, on the first layer of enamel, as well as in at least a part of the un-enameled area, then - depositing a second layer of enamel in the enameled area, on the stack of thin layers.then the supply of a second sheet of glass comprising a first main face and a second main face, then the curvature of the first and second sheets of glass, then the lamination of the first and second sheets of glass using a laminating interlayer, so that the second face of the first sheet of glass is adhesively bonded to the first face of the second sheet of glass. Preferably, the first and second sheets of glass are curved together so that the second face of the first sheet of glass faces the first face of the second sheet of glass.

[0012] The first sheet of glass is generally flat at the time of enamel deposition and thin-layer stacking, and is subsequently curved. It is therefore curved in the glazing according to the invention. The glass of the first sheet is typically a soda-lime silicate glass, but other glasses, for example borosilicates or aluminosilicates, can also be used. The first sheet of glass is preferably obtained by flotation, that is, by a process consisting of pouring molten glass onto a bath of molten tin.

[0013] The first sheet of glass may be clear or tinted, preferably clear. When tinted, for example green, gray, or blue, the chemical composition of the glass sheet advantageously includes iron oxide, in a weight content of 0.5 to 2.0%, and possibly other coloring agents, such as cobalt oxide, chromium oxide, nickel oxide, erbium oxide, or selenium. In the case of a first sheet of clear glass, the chemical composition of the first sheet of glass preferably includes not more than 0.20%, in particular not more than 0.15% by weight, of iron oxide, expressed as Fe₂O₃.

[0014] The first sheet of glass preferably has a thickness in the range of 0.7 to 19 mm, in particular 1 to 10 mm, particularly 2 to 6 mm, or even 2 to 4 mm.

[0015] The lateral dimensions of the first sheet of glass must be adapted according to those of the laminated glass into which it is intended to be integrated. The sheet of glass preferably has a surface area of ​​at least 1 m².

[0016] The first layer of enamel is applied by depositing an enamel composition. An enamel composition is defined as a fluid or paste-like mixture comprising a glass frit and pigments dispersed or suspended in an organic medium. This medium is removed at the latest during the enamel firing, i.e., when the glass sheets are bent. It is removed during a pre-firing stage when the process includes one.

[0017] The enamel composition comprises at least one glass frit. It may comprise a single frit, or alternatively, several glass frits of different compositions. The glass of the (or, where applicable, one or each) glass frit of the enamel composition is preferably a bismuth and / or zinc silicate, borosilicate, or borate. The enamel layer preferably does not contain lead or cadmium oxide. At least one glass frit preferably has a glass transition temperature below 500°C. Low glass transition temperatures allow the frit to soften sufficiently to adhere to the first sheet of glass and bind the pigment particles. The enamel composition may comprise two different glass frits, at least one, and in particular both, having a glass transition temperature below 500°C.

[0018] In one example, the first enamel layer is based on bismuth silicate, bismuth borosilicate, or bismuth borate. In another example, the first enamel layer is based on zinc borosilicate. Each glass frit in the enamel composition preferably comprises 4–10% by weight of B₂O₃, 15–40% by weight of SiO₂, 40–70% by weight of Bi₂O₃, and 0–12% by weight of ZnO.

[0019] The pigments preferably comprise one or more oxides selected from among the oxides of chromium, copper, iron, manganese, cobalt and nickel. These may be, for example, copper and / or iron chromates.

[0020] The organic medium is designed to facilitate the application of the composition to the substrate and its temporary adhesion to the substrate. It generally includes solvents, diluents, oils, and / or resins.

[0021] The first layer of enamel is preferably applied by screen printing or digital printing. Digital printing is advantageous because this technique allows for a lower surface roughness, which is beneficial during the subsequent application of the stacked thin layers.

[0022] In the case of screen printing, a screen printing screen is placed on the sheet of glass, which includes meshes, some of which are blocked, then the enamel composition is deposited on the screen, then a squeegee is applied to force the enamel composition through the screen in the areas where the screen meshes are not blocked, so as to form a layer of wet enamel.

[0023] Examples of digital printing techniques include inkjet printing or laser transfer printing.

[0024] Inkjet printing is preferably carried out using a print head whose movement (in particular its position and speed) is computer-controlled, or using a series of fixed print heads past which the glass moves at a controlled speed. To achieve this, the print head(s) include nozzles through which ink droplets are locally projected onto the glass sheet. This technique is sometimes called "drop on demand" (DOD). Advantageously, the glass frit and pigments in this case have a volumetric particle size distribution such that the D90 is at most 2 µm, for example, between 0.5 and 2.0 µm. The D90 is determined, for example, by laser particle size analysis. The ink viscosity is preferably between 1 and 50 mPa·s.

[0025] Digital printing can also be a transfer printing technique, particularly laser transfer. For example, a substrate, often a rotating one, coated with ink is placed next to the sheet of glass, and the print head emits a focused laser beam onto a portion of the substrate, creating a droplet of ink that is deposited onto the sheet of glass.

[0026] In one preferred embodiment, the enamel composition comprises 10-30%, in particular 15-25%, by weight of organic medium, 50-70%, in particular 55-65%, by weight of glass frit, and 10-30%, in particular 15-25%, by weight of pigments. This embodiment is particularly well-suited for screen printing. In another preferred embodiment, the enamel composition comprises 30-60%, in particular 40-50%, by weight of organic medium, 20-50%, in particular 30-40%, by weight of glass frit, and 10-40%, in particular 20-30%, by weight of pigments. This embodiment is particularly well-suited for digital printing, especially inkjet printing.

[0027] The enameled area preferably represents 2 to 30%, or even 3 to 25%, of the surface of the second main face of the first sheet of glass.

[0028] Preferably, the enameled area forms a band around the periphery of the first pane of glass. This peripheral band is preferably a self-enclosed strip that extends inward from each point on the periphery of the glass pane to a certain width, typically between 1 and 30 cm. This width may vary depending on the area of ​​the glazing. For example, the width may be greater in the lower part of the glazing (in the operating position) than in the lateral sections. As explained previously, the main purpose of this peripheral band is to conceal and / or protect various components, including the glazing mounting joints in the vehicle's body frame and the base of the interior rearview mirror.The peripheral band may provide openings, particularly in the upper part of the glazing (in the position of use), to allow the use of sensors, such as rain sensors, light sensors, cameras or lidars.

[0029] The first layer of enamel is preferably black. The clarity L* of the first layer of enamel, measured in reflection on the glass side, is preferably less than 10, in particular less than 5.

[0030] The thickness of the first layer of wet enamel (after deposition or after possible drying) is preferably between 5 and 35 µm, especially between 10 and 30 µm.

[0031] The application of the first layer of enamel is preferably followed by a drying stage, typically at a temperature between 100 and 200°C, intended to remove at least some of the solvents from the wet enamel layer.

[0032] Preferably, the process also includes, after deposition or after possible drying, a pre-firing step of the first enamel layer before the deposition of the stack of thin layers. The pre-firing step is preferably carried out at a temperature between 300 and 800°C, particularly between 500 and 700°C. Such pre-firing eliminates the organic medium, or more generally any organic component that may be present in the enamel layer. Pre-firing also promotes adhesion of the enamel layer to the glass sheet, achieving the desired shade (often black), and in some cases can lead to partial devitrification of the glass frit, notably through the crystallization of bismuth silicate phases, thereby reducing or preventing, during bending, any adhesion of the enamel to the second glass sheet or to the bending tools.

[0033] The stacking of thin layers is preferably in contact with the first enamel layer, within the glazed area. In this text, "contact" means physical contact. The expression "based on" preferably means that the layer in question comprises at least 50% by weight of the material in question, and in particular 60%, or even 70%, 80%, or 90%. The layer may even consist essentially of this material. "Essentially consists" means that the layer may contain impurities without affecting its properties. The terms "oxide" or "nitride" do not necessarily mean that the oxides or nitrides are stoichiometric. They may, in fact, be substoichiometric, overstoichiometric, or stoichiometric.

[0034] A thin film stack is defined as an assembly consisting of a plurality of superimposed thin films. Thin films are generally layers with a physical thickness between 0.5 and 1000 nm, particularly between 1 and 800 nm.

[0035] The thin-film stack is deposited in at least part of the glazed area and in at least part of the unglazed area. Preferably, the unglazed area is coated with the thin-film stack over at least 70%, and in particular over at least 90%, or even over its entire surface. Certain areas may be left uncoated, notably to provide communication windows allowing the transmission of radio waves. In the unglazed area, the thin-film stack is preferably in contact with the first sheet of glass.

[0036] The thin-film stack can be deposited over the entire glazed area. Alternatively, the thin-film stack may not cover the entire glazed area. For example, it is possible to leave an area of ​​uncoated glaze at the periphery of the first glass sheet, for example, with a width of 0.1 to 10 mm, in order to reduce edge corrosion of the stack. However, the thin-film stack preferably covers at least 80%, and ideally at least 90%, of the glazed area.

[0037] The thin-film stack preferably includes at least one functional layer, in particular an electrically conductive functional layer. The functional layer is preferably located between two dielectric thin films.

[0038] At least one functional layer is advantageously chosen from: - metallic layers, in particular based on silver or niobium, or even gold, and - layers of a transparent conductive oxide, in particular chosen from indium tin oxide, doped tin oxides (for example with fluorine or antimony) and doped zinc oxides (for example with aluminium or gallium).

[0039] The metallic functional layer is preferably silver-based, specifically made of silver. It has been observed that silver ions can migrate during bending from the first glass sheet to the second glass sheet or the bending tools, creating the aforementioned defects.

[0040] These coatings are particularly valued for their low emissivity, which gives the glazing excellent thermal insulation properties. In glazing for land vehicles, including cars, trains, aircraft, and ships, low-emissivity glazing reflects some of the solar radiation outwards in hot weather, thus limiting the heating of the vehicle's interior and, where necessary, reducing air conditioning costs. Conversely, in cold weather, this glazing helps retain heat inside the vehicle, consequently reducing heating energy consumption. The same principle applies to glazing used in buildings.

[0041] According to a preferred embodiment, the thin-film stack comprises at least one silver layer, in particular one, two, three, or even four silver layers. The physical thickness of the silver layer, or where appropriate the sum of the thicknesses of the silver layers, is preferably between 2 and 50 nm, in particular between 3 and 40 nm.

[0042] To protect the electrically conductive thin layer(s) (whether metallic or based on a transparent conductive oxide) during the bending step, each of these layers is preferably sandwiched between at least two dielectric layers. The dielectric layers are preferably based on an oxide, nitride, and / or oxynitride of at least one element selected from silicon, aluminum, titanium, zinc, zirconium, and tin.

[0043] Thin film deposition is preferably achieved by sputtering, particularly magnetically assisted sputtering. In this process, a plasma is created under high vacuum near a target containing the chemical elements to be deposited. The active species in the plasma, by bombarding the target, detach these elements, which are then deposited onto the glass sheet, forming the desired thin film. This process is called "reactive" when the film is composed of a material resulting from a chemical reaction between the elements detached from the target and the gas contained in the plasma. The major advantage of this process lies in the ability to deposit a highly complex stack of layers on a single line by successively passing the glass sheet under different targets, generally within a single device.

[0044] The aforementioned stacks possess electrical conductivity and infrared reflection properties useful for providing a heating function (defrosting, demisting) and / or a thermal insulation function.

[0045] When the stack of thin films is intended to provide a heating function, current supply lines must be provided. These may consist of silver paste strips screen-printed onto the stack of thin films at two opposite edges of the glass sheet.

[0046] All preferred embodiments described in relation to the first enamel layer also apply to the second enamel layer, particularly the details concerning composition, thickness, and application method. As with the first enamel layer, the second enamel layer is preferably applied by digital printing.

[0047] The second layer of enamel is preferably black. The clarity L* of the second layer of enamel, measured in reflection on the glass side, is preferably less than 10, and in particular less than 5.

[0048] The application of the second layer of enamel is preferably followed by a drying stage, typically at a temperature between 100 and 200°C, intended to remove at least some of the solvents from the enamel layer.

[0049] Preferably, the process also includes a pre-firing step of the second enamel layer before the bending step. This pre-firing step is preferably carried out at a temperature between 300 and 800°C, particularly between 500 and 700°C. Such pre-firing eliminates the organic medium, or more generally any organic component that may be present in the enamel layer. Pre-firing also promotes adhesion of the enamel layer to the glass sheet, achieving the desired shade (often black), and in some cases can lead to partial devitrification of the glass frit, notably through the crystallization of bismuth silicate phases, thereby reducing or preventing any adhesion of the enamel to the second glass sheet during bending.

[0050] According to one embodiment, the second layer of enamel is deposited only in the enameled area. This results in a perfect match between the two layers of enamel.

[0051] However, this is not always possible due to industrial tolerances. Therefore, in another embodiment, the first glass sheet comprises, in addition to the glazed and unglazed areas, a transition zone in which the second main face of the first glass sheet is coated only with the stack of thin layers and the second glaze layer. Preferably, such a transition zone covers at most 2%, in particular at most 1%, or even at most 0.5%, of the surface of the second main face of the first glass sheet. In this case, the second glaze layer is deposited in both the glazed area and the transition zone.On the other hand, the second layer of enamel is not deposited in the un-enameled area, since in this area the second main face of the first sheet of glass is at most only coated with said stack of thin layers, that is to say it is either only coated with the stack of thin layers or uncoated.

[0052] The second layer of enamel is normally in contact with the stack of thin layers, in the enameled area as well as in the possible transition area.

[0053] The glazing according to the invention is preferably illuminable. Preferably, it further comprises a light source optically coupled to the second glass pane so as to allow the propagation of light radiation by total internal reflection within the second glass pane, and means for extracting the light radiation disposed on the second glass pane or on the lamination interlayer. As previously mentioned, it is in this type of glazing that defects due to the migration of particles from the first glass pane to the second glass pane during curvature are most pronounced.

[0054] In a preferred embodiment, optical coupling between the second glass pane and the light source is achieved by means of a light redirection element. In this embodiment, the glazing further comprises a light redirection element. Such an element is intended to facilitate the injection of light into the second glass pane and, in particular, to enable the propagation of light within this second glass pane. Specifically, the light redirection element can redirect the light ray into the second glass pane at an angle that allows the light radiation to propagate by total internal reflection within said second glass pane. In certain configurations, a portion of the light can also propagate into a portion of the lamination interlayer.

[0055] Such a light redirection element is in particular a reflective element, especially a reflective prism, disposed between the lamination interlayer and the second sheet of glass (i.e. on the side of face 3 of the glazing), or a transparent element, especially a transparent prism, disposed on the side of face 4 of the glazing.

[0056] The reflective prism can be, in particular, a textured polymer film or a film coated with a textured layer. The texturing can form an arrangement of microprisms. A film coated with a textured layer can be made by embossing a polymer layer (e.g., acrylic) deposited onto a substrate (e.g., polyethylene terephthalate) and then metallizing the layer. Metallization can be achieved, for example, by depositing a metallic layer, such as silver or aluminum. Various deposition processes are possible, including physical vapor deposition (PVD), such as sputtering or evaporation. The thickness of the reflective prism typically ranges from 30 to 500 µm. The microprisms, for example, have a triangular cross-section and are preferably contiguous.

[0057] According to other embodiments, the light source or each light source is optically coupled to the second sheet of glass by all or part of the edge of the second sheet of glass, or by the wall of a hole made in the second sheet of glass and in which the light source or each light source is disposed.

[0058] Each light source can be detached, added, sold separately or as a kit.

[0059] Each light source is, for example, positioned against the second sheet of glass (for example, by gluing), or close to it, for example at 10 cm or less, or even at 5 cm or less. Preferably, each light source is coupled directly to the second sheet of glass, or via an optical guide, for example, an optical fiber.

[0060] Each light source preferably comprises a light-emitting diode (LED) or a plurality of LEDs. Examples of LEDs include Lambertian emission diodes (LEDs) or diodes equipped with a collimating lens. Each light source can be monochromatic (emitting blue, green, red, etc.) or polychromatic. Several light sources can be adapted or combined to produce, for example, white light. The light source(s) can be extended linearly along a longitudinal edge of the glazing, for example, along two opposite longitudinal edges.

[0061] The presence of extraction devices allows light to be extracted at the points where these devices are located, generally through a diffusion process. The extraction devices can be positioned on the second glass pane, on its first main surface, or on its second main surface. Alternatively, the extraction devices can be positioned on or within the interlayer of the lamination.

[0062] Extraction methods can involve a diffusing coating or surface texturization (e.g., sandblasting or acid etching of the glass surface). The diffusing coating can be a layer of organic ink or a mineral layer, such as enamel.

[0063] The refractive index of the diffusing coating (for a wavelength of 550 nm) is preferably greater than or equal to the refractive index of the second glass sheet. It is advantageously at least 1.52, preferably at most 1.70.

[0064] The diffusing coating preferably comprises an organic or inorganic binder and diffusing particles. "Organic ink" refers to inks where the binder is organic in nature. The binder is, for example, a (meth)acrylic binder, notably obtained by cross-linking compounds containing (meth)acrylate groups under ultraviolet radiation. The diffusing particles are preferably mineral, colorless, and typically submicron in size; for example, oxide particles such as titanium dioxide, zinc oxide, aluminum oxide, zirconium oxide, or barium titanate.

[0065] For example, the diffusing coating can be a layer of organic ink printed on the interlayer of the lamination or on one of its folds, or a mineral layer, in particular an enamel, printed on the second sheet of glass, on its first and / or second main face.

[0066] Preferably, laminated glazing includes an optical insulation layer positioned between the second pane of glass and the extraction means. This optical insulation layer notably increases the range of angles between the light ray and the normal to the second pane of glass that allow propagation by total internal reflection within this second pane. This makes it possible to increase the amount of guided light, and therefore the illuminating power.

[0067] The optical insulation layer preferably has a refractive index of at most 1.45, in particular at most 1.42 and even at most 1.40, for example between 1.35 and 1.40, for a wavelength of 550 nm. Preferably, the difference between the refractive index of the second glass sheet and that of the optical insulation layer is at least 0.08, in particular at least 0.10.

[0068] The optical insulation layer is transparent, preferably clear, with a light transmission preferably of at least 80% or 90%. It preferably covers the entire clear area of ​​the glazing.

[0069] The optical insulating layer is preferably a continuous layer, mineral, organic, or mineral / organic hybrid. It may, in particular, include an organic matrix, especially a polymer, for example, an acrylic polymer. Such a matrix can easily be deposited onto a polymer sheet of the lamination interlayer, for example, by liquid deposition of precursors of said polymer (e.g., monomers or oligomers containing acrylate groups) followed by polymerization or crosslinking, particularly under the effect of radiation, such as ultraviolet radiation. In the latter case, the precursors contain a photoinitiator. To further reduce its refractive index, the optical insulating layer may also include, in addition to an organic matrix, pores or particles, particularly porous particles such as hollow silica nanoparticles.Alternatively, the optical insulation layer can be made from a polymeric sheet of the lamination interlayer. For this purpose, a fluorinated polymer (e.g., hexafluoropropylene and tetrafluoroethylene copolymers or polytetrafluoroethylene) or a polysiloxane can be used, these polymers having refractive indices in the aforementioned ranges.

[0070] The curvature is preferably achieved by gravity (the glass deforming under its own weight) or by pressing, at temperatures typically ranging from 550 to 650°C. The two sheets of glass in laminated glazing are preferably curved together, so as to ensure that they have the same curvature.

[0071] During the curving process, the inner pane of glass (intended for the interior of the vehicle) is normally placed above the outer pane of glass. Thus, the first pane of glass is located beneath the second pane, with the enamel layer sandwiched between the two panes. In laminated curved glass, the first pane of glass is positioned on the convex side of the glazing, and its second main surface faces the lamination interlayer. The enamel layer is then positioned on surface 2 of the glazing.

[0072] During the bending process, the two glass sheets can be kept apart by placing an interlayer powder between them, creating a gap of a few tens of micrometers, typically 20 to 50 µm. This interlayer powder is, for example, based on calcium carbonate and / or magnesium carbonate, and its purpose is to reduce the risk of the glass sheets sticking together. Alternatively, the two glass sheets can be bent separately.

[0073] The lamination process can be carried out by autoclave treatment, for example at temperatures of 110 to 160°C and under a pressure of 10 to 15 bar. Prior to autoclave treatment, the air trapped between the glass sheets and the laminating interlayer can be removed by calendering or vacuum extrusion. The second glass sheet can (preferably) be made of soda-lime glass, or alternatively, borosilicate or aluminosilicate glass. It can be clear or tinted. Its thickness is preferably between 0.5 and 4 mm, particularly between 1 and 3 mm.

[0074] In one embodiment, the second glass pane carries on the face opposite the face facing the laminating interlayer (preferably face 4, the second glass pane being the inner pane) an additional stack of thin films, in particular a low-emissivity stack, comprising a transparent conductive oxide, in particular indium tin oxide (ITO). In this embodiment, the laminating interlayer and / or the second glass pane is preferably tinted, the glass pane bearing the coatings being able to be clear glass. The resulting glazing is preferably a motor vehicle roof.

[0075] The lamination interlayer preferably comprises at least one sheet of polyvinyl acetal, in particular polyvinyl butyral (PVB). Other polymers include ethylene-vinyl acetate copolymers and thermoplastic polyurethanes.

[0076] As previously mentioned, the extraction means can be deposited on a polymeric sheet of the lamination interlayer.

[0077] The lamination interlayer can be tinted or untinted in order to regulate the optical or thermal properties of the glazing if necessary.

[0078] The laminate interlayer can advantageously possess sound-absorbing properties to absorb airborne or structure-borne noise. It can, in particular, be composed of three polymer sheets, including two outer sheets of PVB framing an inner polymer sheet, possibly also made of PVB, with a lower hardness than the outer sheets.

[0079] The lamination interlayer can also possess thermal insulation properties, particularly infrared radiation reflection. For this purpose, it can comprise a low-emissivity thin-film coating, for example, a coating including a thin silver layer or a coating alternating dielectric layers with different refractive indices, deposited on an inner PET sheet sandwiched between two outer PVB sheets.

[0080] The thickness of the lamination interlayer is generally in the range of 0.3 to 1.5 mm, particularly 0.5 to 1 mm. The lamination interlayer may be thinner at one edge of the glazing than in the center of the glazing to avoid the formation of a double image when using a head-up display (HUD).

[0081] The glazing may incorporate additional functional elements, particularly within the lamination interlayer. This additional functional element may be sandwiched between two polymer sheets of the interlayer. The additional functional element may include an electrically controlled device, such as one with variable diffusion or tint. Examples include suspended particle devices (SPDs), polymer-dispersed liquid-crystal displays (PDLCs), and electrochromic devices.

[0082] The enameled area, in addition to its function of concealing and protecting the polymer seals, can also serve as a display area for information, for example, in the case of a windshield, information useful for driving the vehicle. In this case, the presence of the second enamel layer improves the legibility of the information, which could be compromised by light reflection from the stacking of thin layers.

[0083] The glazing according to the invention is preferably vehicle glazing, in particular for motor vehicles, in particular a windscreen or a motor vehicle roof, in which the first main face of the first sheet of glass is intended to be located outside the vehicle.

[0084] The figures and examples that follow illustrate the invention in a non-limiting manner.

[0085] represents an exploded view of a glazing 10 according to the invention.

[0086] represents a partial exploded view of a glazing according to the invention.

[0087] Figures 1 and 2 are schematic exploded views of glazing units according to the invention. The views are exploded to show on which sheets the various elements are deposited. The figures are obviously not to scale, as the thickness of some elements is greatly enlarged for visualization. The glazing units are shown here in plan view for simplicity. The figures indicate faces 1 to 4 of the glass sheets, respectively labeled F1, F2, F3, and F4. In these examples, the first glass sheet is therefore the outermost sheet of the glazing unit, that is, the one intended to be on the outside of the vehicle. The glazing units will be described here in relation to an application as automotive roofs.

[0088] The glazing 10 comprises a first sheet of glass 11 and a second sheet of glass 12 bonded together by a lamination interlayer 14. The second main face of the first sheet of glass, here called face F2, includes an enameled area Z1, here in the form of a peripheral strip, and an un-enameled area Z2, corresponding in this example to the sight line of the glazing. In the un-enameled area Z2, the second main face of the first sheet of glass F2 is covered only by a stack of thin films 16. In the enameled area Z1, the second main face of the first sheet of glass F2 comprises, successively from this face, a first layer of enamel 15, the stack of thin films 16, and a second layer of enamel 17. The stack of thin films 16 is, for example, a stack comprising at least one layer of silver arranged between dielectric layers.

[0089] In the example shown, the glazing 10 is an illuminating glazing, which further comprises a light source 20, a light redirection element 21, here arranged on face F3, or the first principal face of the second glass pane 12, and extraction means 22. In the example shown, the light redirection element is a reflective prism, but other configurations are obviously possible. This redirection element 21 redirects the light emitted by the light source 20 at an angle that allows the light radiation to propagate by total internal reflection in the second glass pane 12, as shown by the arrows in the figure. The light source 20 may, for example, comprise at least one set of light-emitting diodes (LEDs) arranged near face F4, along a longitudinal edge of the glazing.Other configurations are obviously possible (different types of positioning, presence of multiple sources, different types of light sources, etc.). The extraction means 22 are here arranged on face F3, therefore on the first main face of the second glass pane, but as described previously, other configurations are possible. It goes without saying that the glazing according to the invention is not necessarily illuminating.

[0090] Figure 1 represents a detail of a glazing unit according to the invention, more precisely a detail of the first sheet of glass 11, near an edge of the glazing unit 10. This view shows the first enamel layer 15, the second enamel layer 17, and the stack of thin layers 16. Unlike the embodiment of Figure 1, where the correspondence between the two enamel layers was perfect, this figure shows a slight lateral offset, typically on the order of 1 mm, between the two enamel layers. The second enamel layer 17 is offset towards the center of the glazing unit, so as to create a transition zone Z3 between the enameled area Z1 and the un-enameled area Z2. In this transition zone, the first sheet of glass 11 is therefore coated only with the stack of thin layers 16 and the second layer of enamel 17. It is also observed that the stack of thin layers is not present at the extreme edge of the glazing, thus improving its resistance to corrosion.

[0091] In one example according to the invention, a first sheet of glass similar to the one shown in Figure 1 was manufactured. To do this, a 45 mm wide enamel frame was printed on the periphery of a first 2.1 mm thick sheet of clear soda-lime-silica glass. The first layer of enamel, with a wet thickness of 21 µm, was screen-printed using a composition commercially available under reference 14316 from Vibrantz. After pre-firing at 630°C for 180 seconds, a stack of thin films comprising two layers of silver was deposited by magnetron sputtering onto the enamel frame (enameled area) as well as onto the clear (unenameled area). A second enamel frame was then deposited onto the stack of thin films, slightly offset from the first enamel frame, as shown in Figure 1.The printing was also carried out by screen printing of a composition commercially available under reference 14316 from the company Vibrantz, and the second layer of enamel had a wet thickness of 19 µm. After a second pre-firing at 630°C for 180 seconds, the first sheet of glass was paired with a second sheet of clear soda-lime silico-glass so that the face of the first sheet of glass coated with the layers of enamel and the stack of thin layers was turned towards the second sheet of glass, and the assembly was domed at 640°C for 500 seconds.

[0092] In a comparative test, the second layer of enamel was not deposited.

[0093] It is observed that in the enameled area, the second glass pane has taken on a slight yellow tint in the comparative example (transmission b* value of 1.1, compared to 0.2 in the example according to the invention, which corresponds to the value for the original clear glass). This yellowing is due to the transfer of silver ions into the second glass pane during the curvature. Viewed from face 1, the reflected appearance of the glazing is also different: the b* value is -1.1 for the example according to the invention and -0.1 for the comparative example. The transition zone between the enameled and un-enameled areas is very sharp, viewed from face 1, in the example according to the invention, due to the reflection of the stack of thin layers seen in front of the second enamel layer. In the comparative example, however, the silver transfer into the second glass pane creates a golden halo in this zone.

Claims

Curved laminated glazing (10) comprising: - a first sheet of glass (11) comprising a first main face (F1) and a second main face (F2), and - a second sheet of glass (12) comprising a first main face (F3) and a second main face (F4), the second main face (F2) of the first sheet of glass (11) being adhesively bonded to the first main face (F3) of the second sheet of glass (12) by means of a lamination interlayer (14), and the second main face (F2) of the first sheet of glass (11) comprising: - an enameled area (Z1), in which the second main face (F2) of the first sheet of glass (11) is coated by a coating comprising successively a first layer of enamel (15), a stack of thin layers (16), then a second layer of enamel (17), and - an un-enameled area (Z2),wherein the second principal face (F2) of the first sheet of glass (11) is at most solely coated with said stack of thin layers (16). Curved laminated glazing (10) according to claim 1, in which the enameled area (Z1) forms a band around the periphery of the first sheet of glass (11). Curved laminated glazing (10) according to any one of the preceding claims, wherein the stacking of thin layers (16) comprises at least one metallic functional layer, in particular silver-based. Curved laminated glazing (10) according to any one of the preceding claims, wherein the first layer of enamel (15) and the second layer of enamel (17) are black, their clarity L*, measured in reflection on the glass side being preferably less than 10. Curved laminated glazing (10) according to any one of the preceding claims, wherein the first sheet of glass (11) comprises, in addition to the enameled area (Z1) and the un-enameled area (Z2), a transition area (Z3) in which the second main face (F2) of the first sheet of glass (11) is coated only with the stack of thin layers (16) and the second layer of enamel (17). Curved laminated glazing (10) according to any one of the preceding claims, which is an illuminable glazing, further comprising a light source (20) optically coupled with the second sheet of glass (12) so as to allow the propagation of light radiation by total reflection in the second sheet of glass (12) and means for extracting the light radiation (22) disposed on the second sheet of glass (12) or on the lamination interlayer (14). Curved laminated glazing (10) according to any one of the preceding claims, which is glazing for a motor vehicle, in particular a windscreen or a roof of a motor vehicle, in which the first principal face (F1) of the first sheet of glass (11) is intended to be located outside the vehicle. A method for obtaining a curved laminated glazing (10) according to any one of the preceding claims, comprising: - supplying a first sheet of glass (11) comprising a first principal face (F1) and a second principal face (F2), then - depositing a first layer of enamel (15) on an area, referred to as the enameled area (Z1), of the second principal face (F2) of the first sheet of glass (11), said second principal face (F2) of the first sheet of glass (11) being devoid of said first layer of enamel (15) in an area referred to as the un-enameled area (Z2), then - depositing a stack of thin films (16) on the second face (F2) of the first sheet of glass (11), in at least a part of the enameled area (Z1), on the first layer of enamel (15), as well as in at least a part of the un-enameled area (Z2), then - depositing a second layer enamel (17) in the enameled zone (Z1), on the stack of thin layers (16),then- the supply of a second sheet of glass (12) comprising a first main face (F3) and a second main face (F4), then- the curvature of the first sheet of glass (11) and the second sheet of glass (12), then- the lamination of the first sheet of glass (11) and the second sheet of glass (12) by means of a lamination interlayer (14), so that the second face (F2) of the first sheet of glass (11) is adhesively bonded to the first face (F3) of the second sheet of glass (12). A method according to the preceding claim, wherein the first and second glass sheets are curved together so that the second face (F2) of the first glass sheet (11) is turned towards the first face (F3) of the second glass sheet (12). A method according to any one of claims 8 or 9, wherein the deposition of the first layer of enamel (15) is carried out by digital printing. A method according to any one of claims 8 to 10, further comprising a pre-firing step of the first enamel layer (15) before the deposition of the stack of thin layers (16). A method according to any one of claims 8 to 11, wherein the stack of thin films (16) is deposited by sputtering. A method according to any one of claims 8 to 12, wherein the second layer of enamel (17) is deposited by digital printing.

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