Curved laminated glazing

Abstract

The invention relates to a curved laminated glazing (10) in which a second main face (F2) of a first glass sheet (11) is adhesively bonded to a first main face (F3) of a second glass sheet (12) by means of a lamination interlayer (14), the second main face (F2) comprising an enamelled area (Z1), in which the second main face (F2) is coated with a coating successively comprising an enamel layer (15) and then a stack of thin layers (16), and a non-enamelled area (Z2), in which the second main face (F2) is at most coated only with the stack of thin layers (16), and the enamel layer (15) comprises an amorphous phase and pigments, the content by weight of silica in the amorphous phase being greater than 30%.

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, typically 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 manufacturing of laminated glass, the two glass sheets 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 bears the enamel. It is therefore essential that the enamel possess non-stick properties to prevent the two glass sheets from sticking together during the curving process. To achieve this, bismuth-containing enamels are typically used; these are obtained from glass frits containing bismuth oxide. Such frits have the unique characteristic of forming bismuth silicate crystals during a pre-baking stage of the enamel, prior to curing.

[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 stacks of layers are generally arranged on face 3 of the laminated glazing, therefore also in contact with the lamination interlayer.

[0009] However, it can be advantageous to place the enamel layer and the thin-film stack on the same sheet of glass, and therefore on the same face of the glass sheet (generally face 2), so that these coatings are protected within the laminated glass. This is the case, for example, when another thin-film stack is also to be deposited on face 4. One possible solution is to deposit the thin-film stack on top of the enamel layer.

[0010] The inventors have, however, pointed out that in this case, undesirable interactions between the enamel layer and the thin-layer stack could occur during the curvature, leading to at least partial deterioration of the stack, with consequences for the aesthetic appearance of the enamel, particularly its color, and for the properties of the stack. The invention aims to remedy these problems.

[0011] 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, from said second main face of the first sheet of glass, a layer of enamel and then a stack of thin layers, 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,in which the enamel layer comprises an amorphous phase and pigments, the silica content by weight in said amorphous phase being greater than 30%.

[0012] 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 main face and a second main face, then - depositing a layer of enamel on an area, called the enameled area, of the second main face of the first sheet of glass, said second main face of the first sheet of glass being devoid of said enamel layer in an area called the un-enameled area, then - pre-firing the enamel layer at a temperature between 500 and 650°C, 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 enamel layer, as well as in at least a part of the un-enameled area, then - supplying a second sheet of glass comprising a first main face and a second main face.then - the first and second sheets of glass are curved, said first and second sheets of glass being curved together so that the second main face of the first sheet of glass is turned towards the first main face of the second sheet of glass; then - the first and second sheets of glass are laminated by means of a laminating interlayer, so that the second main face of the first sheet of glass is adhesively bonded to the first main face of the second sheet of glass.

[0013] 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.

[0014] 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 glass sheet preferably includes not more than 0.20%, in particular not more than 0.15% by weight, of iron oxide, expressed as Fe₂O₃.

[0015] 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.

[0016] 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 (and therefore also the final glazing) preferably has a surface area of ​​at least 1 m².

[0017] The enamel layer is applied by depositing an enamel composition. An enamel composition is a fluid or paste-like mixture comprising a glass frit and pigments dispersed or suspended in an organic medium. This medium is removed during the pre-firing of the enamel. In the case of digital printing, the enamel composition is sometimes called "ink."

[0018] 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 or borosilicate, preferably a bismuth and zinc borosilicate. 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.

[0019] In one example, the enamel layer is based on bismuth silicate or bismuth borosilicate. In another example, the 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.

[0020] The pigments preferably comprise one or more oxides selected from among the oxides of chromium, copper, iron, manganese, cobalt, and nickel. Examples include copper and / or iron chromates, for instance, with the formula CuCr2O4 or CuMn. x Cr 2-x O4.

[0021] 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.

[0022] The enamel layer 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.

[0023] 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.

[0024] Examples of digital printing techniques include inkjet printing or laser transfer printing.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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 can 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.

[0030] The enamel layer is preferably black. The clarity L* of the enamel layer, measured in reflection on the glass side, is preferably less than 10, in particular less than 5.

[0031] The thickness of the wet enamel layer (after deposition or after possible drying) is preferably between 5 and 35 µm, especially between 10 and 30 µm.

[0032] The deposition of the enamel layer 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.

[0033] The process also includes, after deposition or after possible drying, a pre-firing step of the enamel layer before the deposition of the stack of thin layers. This 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, thus reducing or preventing any adhesion of the enamel to the second glass sheet during the bending process.

[0034] Preferably, the silica content by weight in the amorphous phase after pre-firing and / or in the final glazing is at least 32%, in particular at least 33%, or even at least 35%, 37%, or 38%. It is preferably between 32% and 55%, in particular between 35% and 50%, or even between 39% and 49%, both after pre-firing and in the final glazing. For glass compositions, it is customary to express the mass proportions of elements as oxides. For example, the silicon content is expressed as silica, in other words, silicon dioxide, or SiO2.

[0035] During pre-firing, the frit of the enamel composition forms a vitreous or vitreous binder that binds the pigments. This binder comprises an amorphous phase and possibly crystalline phases obtained by partial devitrification of the frit. The inventors were able to demonstrate that the presence of a sufficient quantity of silica in this amorphous phase results in a particularly viscous amorphous phase, which is therefore less aggressive towards the stacking of thin layers. This makes it possible to avoid damaging the stack during the curving process.

[0036] The silica content by weight in the amorphous phase is preferably determined as follows. The overall chemical composition of the enamel layer can be determined by known techniques, for example, inductively coupled plasma spectroscopy (ICP) and / or X-ray fluorescence spectroscopy (XRF). Since the latter method is not capable of analyzing light elements such as boron and lithium, it cannot be used alone and must be supplemented by other methods, such as ICP. The amount of amorphous phase and the composition of the crystals can be determined by X-ray diffraction using the Rietveld method. Knowing the amount of silica in the enamel and that present in the crystals, as well as the amount of amorphous phase, it is then possible to calculate the silica content in the amorphous phase by difference.

[0037] The silica content by weight in the amorphous phase depends primarily on the composition of the glass frit(s), particularly the silica content, and, for frits capable of devitrification, the pre-firing temperature. In the latter case, pre-firing at a higher temperature leads to an increase in the silica content in the amorphous phase because this promotes devitrification, which consumes more bismuth than silicon. Regarding the composition of the glass frit(s), the silica content must be sufficient, especially to ensure that even after devitrification, enough silica remains in the amorphous phase.

[0038] Preferably, the amorphous phase of the enamel layer also includes at least one element selected from boron, bismuth, and zinc. The content of these elements will be expressed as oxides, B₂O₃, Bi₂O₃, and ZnO. Other elements potentially present in the amorphous phase include sodium, lithium, and barium.

[0039] According to a preferred embodiment, the enamel layer further comprises bismuth silicate crystals. The bismuth silicate crystals are preferably Bi4Si3O crystals. 12The enamel layer then comprises, in particular, an amorphous phase, bismuth silicate crystals, and pigments. As mentioned previously, such crystals, which form during pre-firing, prevent the two glass sheets from sticking together and / or the enamel from transferring to the second glass sheet during the bending process. The risk of sticking or transfer exists particularly when the stack of thin layers is not deposited across the entire enameled area, for example, when it is not deposited at the very edge of the glass sheet, in order to reduce the risk of corrosion.

[0040] Alternatively, the enamel layer may consist of an amorphous phase and pigments. This is the case when no glass frit in the composition is capable of devitrifying.

[0041] Preferably, the weight content of the amorphous phase in the enamel layer is 30 to 80%, in particular 40 to 75%, or even 50 to 70%. The weight content of pigments in the enamel layer is preferably 15 to 50%, in particular 20 to 40%. The content of crystals other than pigments, in particular bismuth silicate crystals, in the enamel layer is preferably 0 to 40%, in particular 2 to 35%, or even 4 to 30%.

[0042] The stacking of thin layers is preferably in contact with the 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.

[0043] A thin-film stack is defined as an assembly consisting of a plurality of superimposed thin films. Thin films are typically layers with a physical thickness between 0.5 and 1000 nm, particularly between 1 and 800 nm. The thin-film stack comprises at least two thin films, preferably at least three, and even at least four or five. The number of thin films in the stack is preferably between 5 and 15. The thin-film stack is normally transparent. It is preferably a low-emissivity stack, particularly with a normal emissivity of less than 0.25, or even less than 0.15.

[0044] 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.

[0045] The thin-film stack can be deposited over the entire enameled area. Alternatively, the thin-film stack may not be deposited over the entire enameled area. For example, it is possible to leave an area of ​​enamel uncoated by the thin-film stack at the periphery of the first glass sheet, for example, over a width of 0.1 to 10 mm to reduce edge corrosion of the stack, or even over larger widths, for example, up to 300 mm or 500 mm, to create radio-frequency transparent areas. In this case, it is possible, for example, to mask the areas where the stack should not be deposited. However, the thin-film stack preferably covers at least 80%, or even at least 90%, of the enameled area.

[0046] 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.

[0047] 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).

[0048] The metallic functional layer is preferably silver-based, in particular is made of silver.

[0049] These coatings are particularly valued for their low emissivity, which gives the glazing excellent thermal insulation properties. In the glazing of land vehicles, particularly cars, trains, as well as 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 the energy required for heating.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] The aforementioned stacks possess electrical conductivity and infrared reflection properties useful for providing a heating function (defrosting, demisting) and / or a thermal insulation function.

[0054] 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.

[0055] 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 curved together, so as to ensure that they have the same curvature.

[0056] 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.

[0057] During the curving process, the two glass sheets can be kept apart by placing an interlayer powder between them, ensuring a gap of a few tens of micrometers, typically 20 to 50 µm. The interlayer powder is, for example, based on calcium carbonate and / or magnesium, and aims to reduce the risk of the glass sheets sticking together.

[0058] 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.

[0059] In a preferred embodiment, the second glass sheet carries on the face opposite the face facing the laminating interlayer (preferably face 4, the second glass sheet being the inner sheet) an additional thin-film stack, 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 sheet is preferably tinted, the glass sheet bearing the coatings (i.e., the enamel layer and the thin-film stack) possibly being made of clear glass. Having the thin-film stack and the additional thin-film stack on different glass sheets prevents damage to one of the stacks, which is frequently observed when a glass sheet is coated with a stack on both of its principal faces.The glazing obtained is preferably a motor vehicle roof.

[0060] 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.

[0061] The lamination interlayer can be tinted or untinted in order to regulate the optical or thermal properties of the glazing if necessary.

[0062] 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.

[0063] 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.

[0064] 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).

[0065] The glazing according to the invention is preferably an illuminable glazing. Preferably, it further comprises a light source optically coupled with the second glass pane so as to allow the propagation of light radiation by total internal reflection in the second glass pane, and means for extracting the light radiation disposed on the second glass pane or on the lamination interlayer.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] Each light source can be detached, added, sold separately or as a kit.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] As examples, 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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 (PDLC) displays, and electrochromic devices.

[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 principal 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 principal 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 principal face of the first sheet of glass F2 comprises, successively from this face, an enamel layer 15 and the stack of thin films 16. The stack of thin films 16 is, for example, a stack comprising at least one silver layer 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 10 represents a detail of a glazing according to the invention, more precisely a detail of the first sheet of glass 11, close to an edge of the glazing 10. This view shows the enamel layer 15 as well as the stack of thin layers 16. It can be observed that the stack of thin layers is not present at the extreme edge of the glazing, thus improving its resistance to corrosion.

[0091] Four commercial bismuth borosilicate enamel compositions were tested, designated A (Fenzi 1L6026), B (Vibrantz 14316), C (Fenzi 1EPB2140), and D (Tecglass 1A005). These compositions were deposited onto clear soda-lime-silica glass sheets to form enamel layers. Compositions A, B, and C were deposited by screen printing, and composition D by inkjet printing. The enamel layers were then pre-fired for 180 seconds at temperatures of 580°C, 600°C, and 620°C. The target thickness after pre-firing was 13 µm.

[0092] The silica content in the amorphous phase was then determined using the method described previously. For X-ray diffraction, the patterns were determined between 5 and 100° with an angular step size of 0.01° and a step time of 0.68 s / step to ensure a good signal-to-noise ratio. Rietveld refinement was performed using HighScore software from Malvern Panalytical. After pre-firing, the four tested compositions contained Bi4Si3O crystals. 12 , copper chromate-based pigments and an amorphous phase.

[0093] Table 1 below indicates for each glaze and each pre-firing temperature T the silica content in the amorphous phase.

[0094] T (°C)SiO2(%)A58024,660026,862029,0B58035,860038,662039,9C58042,660044,462046,6D58044,760046,662048,9

[0095] Compositions A through D were deposited onto clear soda-lime-silica glass sheets to form 4.5 mm wide peripheral frames. Compositions A, B, and C were screen-printed, and composition D was inkjet-printed. The samples were then pre-fired at 620°C for 180 seconds. A thin-film stack consisting of two thin silver layers sandwiched between thin dielectric layers was then deposited by magnetron sputtering onto the enamel-coated side. After being paired with a 2.1 mm thick sheet of clear soda-lime-silica glass, the assembly was domed at 640°C for 500 seconds.

[0096] Table 2 below indicates for each enamel the following two parameters, noted ΔE and ΔR.

[0097] The parameter ΔE corresponds to the difference in reflected color of the glaze, viewed from the glass side, between the color before and after curving. To determine this, the colorimetric parameters L*a*b* in reflected glass-side light were measured after pre-firing (parameters with a subscript 1 in the following formula) and after curving (parameters with a subscript 2). The parameter ΔE therefore reflects a color variation in the glaze due to interactions with the stacking process during curving.

[0098]

[0099] The parameter ΔR corresponds to the difference in square resistance (in Ohms) of the thin-film stack between the unglazed and glazed areas. The parameter ΔR therefore also reflects the degradation of the stack in the glazed area.

[0100] EmailΔEΔR (Ω)A21.55.6B0.70.5C0.91.8D0.40.8

[0101] Enamel A, whose amorphous phase is low in SiO2, is particularly aggressive towards the stack, resulting in significant color variation and variation in square strength, indicating stack degradation and contamination of the enamel by the stack's constituents. In contrast, the high silica content of the amorphous phase of enamels B, C, and D prevents degradation of the thin-film stack.

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, from said second main face (F2) of the first sheet of glass (11), a layer of enamel (15) then a stack of thin layers (16), and - an un-enameled area (Z2),in which the second main face (F2) of the first sheet of glass (11) is at most coated solely with said stack of thin layers (16), in which the enamel layer (15) comprises an amorphous phase and pigments, the silica content by weight in said amorphous phase being greater than 30%. 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 weight content of silica in the amorphous phase is between 32 and 55%, in particular between 35 and 50%. Curved laminated glazing (10) according to any one of the preceding claims, wherein the amorphous phase of the enamel layer (15) further comprises at least one element selected from boron, bismuth and zinc. Curved laminated glazing (10) according to any one of the preceding claims, wherein the enamel layer (15) further comprises bismuth silicate crystals. 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 main face (F1) and a second main face (F2), then - depositing a layer of enamel (15) on an area, referred to as the enameled area (Z1), of the second main face (F2) of the first sheet of glass (11), said second main face (F2) of the first sheet of glass (11) being devoid of said enamel layer (15) in an area referred to as the un-enameled area (Z2), then - pre-firing the enamel layer (15) at a temperature between 500 and 650°C, 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 enamel layer (15), as well as in at least part of the unglazed area (Z2),then- the provision of a second sheet of glass (12) comprising a first principal face (F3) and a second principal face (F4), then- the curvature of the first sheet of glass (11) and the second sheet of glass (12), said first and second sheets of glass being curved together so that the second principal face (F2) of the first sheet of glass (11) is turned towards the first principal face (F3) of 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 principal face (F2) of the first sheet of glass (11) is adhesively bonded to the first principal face (F3) of the second sheet of glass (12). Method according to the preceding claim, wherein the deposition of the enamel layer (15) is carried out by digital printing. A method according to any one of claims 8 to 10, wherein the stack of thin films (16) is deposited by sputtering.

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