Glass sheet comprising an enamelled zone

Abstract

The invention concerns a material comprising a glass sheet (10), one face of which comprises an enamelled zone (2), such that in said enamelled zone (2), the glass sheet (10) is coated with an opaque mineral layer (12) and, under at least a part of said opaque mineral layer (12), with a transparent mineral coating (14) which is not an enamel, said transparent mineral coating (14) comprising, in said enamelled zone (2), a first zone (Z1) in which the transparent mineral coating (14) has a first thickness (e1), and a second zone (Z2) in which the transparent mineral coating (14) has a second thickness (e2), said first and second thicknesses being different.

Description

Glass sheet including an enamelled area

[0001] The invention relates to the field of glazing, in particular glazing for buildings or for transport vehicles.

[0002] It is known to coat glass sheets, over all or part of their surface, with opaque mineral layers, in particular opaque enamel layers. An enamel is a layer comprising a vitreous or vitrocrystalline binder and pigments, obtained by depositing a fluid enamel composition comprising a glass frit, pigments and an organic medium and then by firing. Enamel layers are often decorative but can also provide masking and protective functions, for example against ultraviolet radiation.

[0003] The aim of the invention is to provide enamelled glazing having a decorative appearance seen from the face opposite the face bearing the opaque layer and which can be manufactured simply and economically.

[0004] To this end, the subject of the invention is a material comprising a glass sheet, one face of which comprises an enamelled zone, such that in said enamelled zone the glass sheet is coated with an opaque mineral layer and, under at least part of said opaque mineral layer, with a transparent mineral coating which is not an enamel, said transparent mineral coating comprising, in said enamelled zone, a first zone in which the transparent mineral coating has a first thickness and a second zone in which the transparent mineral coating has a second thickness, said first and second thicknesses being different.

[0005] The invention also relates to a method for obtaining such a material, comprising the deposition, on one face of a glass sheet and in a zone called the enameled zone, of a transparent mineral coating which is not an enamel, then, on this transparent mineral coating, of an opaque mineral layer, said transparent mineral coating comprising, in said enameled zone, a first zone in which the transparent mineral coating has a first thickness and a second zone in which the transparent mineral coating has a second thickness, said first and second thicknesses being different.

[0006] The invention also relates to glazing comprising a material according to the invention.

[0007] The inventors were able to demonstrate that the presence of a transparent mineral coating and the existence of a plurality of zones in which the transparent mineral coating has a different thickness made it possible to form a decoration visible from the face opposite the enameled face. The reflected appearance of the enamel is modulated by the thickness of the underlying coating, and the contrast between the different zones makes it possible to create a decoration. This decoration is also obtained in a very simple manner, using a single opaque mineral layer (in particular enamel) and possibly after a single firing step.

[0008] The glass sheet is preferably made of soda-lime-silica glass. It is advantageously obtained by floating. Other glass compositions are however possible, for example borosilicate or aluminosilicate compositions.

[0009] The glass sheet may be clear glass or tinted glass, for example green, gray, bronze or blue. In the case of tinted glass, the chemical composition of the glass sheet advantageously comprises iron oxide, in a weight content ranging from 0.5 to 2.5%. It may also comprise other coloring agents, such as cobalt oxide, chromium oxide, nickel oxide, erbium oxide, or selenium. In the case of clear glass, the chemical composition of the glass sheet advantageously comprises iron oxide in a weight content ranging from 0.01 to 0.15%.

[0010] The glass sheet has a thickness preferably between 0.7 and 19 mm, in particular between 1 and 6 mm, or even between 2 and 4 mm. The glass sheet preferably has a surface area of ​​at least 1 m².

[0011] The glass sheet can be flat or curved. It is generally flat during the deposition stages of the transparent mineral coating and the opaque mineral layer. However, certain deposition techniques, particularly digital printing, allow these coatings to be deposited on a curved sheet. In the case of vehicle glazing, particularly for motor vehicles, it is preferably then curved and therefore has a curved shape in the final glazing.

[0012] The term "glazed area" generally means the area covered by the opaque mineral layer, which is most often a layer of enamel, but not necessarily, as detailed in the rest of the text.

[0013] The enamelled area may cover all or part of the surface of the glass sheet, depending on the intended application. It may cover the entire surface of the glass sheet, for example in the case of spandrels. Alternatively, it may cover only part of the surface of the glass sheet, in particular from 2 to 80%, or even from 5 to 50% or from 10 to 25%. In the case of vehicles, in particular motor vehicles, the enamelled area is preferably in the form of a peripheral strip. By "peripheral strip" is meant a strip closed on itself which, from each point on the periphery of the glass sheet, extends towards the inside of the glass sheet over a certain width, typically between 1 and 20 cm.This peripheral strip is intended to conceal and protect against ultraviolet radiation the polymer seals used for fixing and positioning the glazing in the bodywork bays, as well as various mechanical or electrical elements (heating circuits, rearview mirror bases, sensors or cameras, etc.).

[0014] According to one embodiment, the transparent mineral coating is in contact with the glass sheet. In this case, the glass sheet is preferably coated, in the enameled area, only with the coating and with the opaque mineral layer.

[0015] Alternatively, other layers or stacks of layers may be interposed between the glass sheet and the transparent mineral coating. These may, for example, be thin layers or stacks of thin layers comprising at least one functional layer, for example an electrically conductive or low-emissivity layer, in particular based on silver or based on a transparent electrically conductive oxide (TCO) such as indium tin oxide or doped tin or zinc oxides. Such layers or stacks may, in particular, perform heating (defrosting, demisting) and / or solar control and / or thermal insulation functions.

[0016] The opaque mineral layer is preferably in contact with the transparent mineral coating.

[0017] The transparent mineral coating is present under at least part of the opaque mineral layer. It may be present under the entire opaque mineral layer, therefore in the entire enameled area. Alternatively, it may be present under only part of the opaque mineral layer, for example under 2 to 80%, in particular 10 to 60% of the opaque mineral layer. This is the case, for example, when the transparent mineral coating is intended to form a decoration in only part of the enameled area.

[0018] In both cases described above, the transparent mineral coating may also be present on all or part of the unglazed area, when the latter exists. It may then be present on the entire glass sheet. This is the case, for example, when the transparent mineral coating has another function, also useful in the clear view of the glazing, for example an optical function, in particular anti-reflective. Alternatively, the transparent mineral coating may not be present in the unglazed area.

[0019] The presence of a transparent mineral coating makes it possible to modify the appearance of the enamel seen in reflection through the glass sheet. It appeared that this appearance differed depending on the thickness of the coating. The existence of a plurality of zones where the coating has different thicknesses thus makes it possible to obtain a different appearance in each zone, giving the possibility of obtaining a decoration.

[0020] The decor can be of any nature: various patterns, for example geometric, logos etc. For example, the decor can create a transition zone between the bodywork of a vehicle and the clear view of the glazing.

[0021] In order to obtain an attractive rendering, the transparent mineral coating preferably has a high light transmission. The transparent mineral coating is preferably such that, when deposited on a sheet of clear glass, the light transmission factor is at least 70%, in particular at least 80%, or even at least 88%. Clear glass means a glass whose chemical composition comprises, as the sole colorant, iron oxide in a weight content of between 0.05 and 0.12%. An example of clear glass is Planiclear® glass marketed by the Applicant.

[0022] The transparent mineral coating is preferably colorless (in other words, untinted). In particular, the colorimetric coordinates a* and b* (illuminant D65, observer CIE-1964) in transmission of the transparent mineral coating seen through a sheet of clear glass are preferably between 0 and 5, in particular between 0 and 2, or even between 0 and 1.

[0023] According to one embodiment, the transparent mineral coating comprises a single layer. The existence of zones of different thicknesses is then obtained by locally varying the thickness of the single layer during its deposition.

[0024] According to another embodiment, the transparent mineral coating comprises, at least in the first or in the second zone, a plurality of superimposed layers, in particular two, three or four layers. In this case, the thickness of the coating in a zone corresponds approximately to the sum of the thicknesses of each of the layers forming the coating in this zone. The thickness of the coating may not correspond exactly to the sum of the thicknesses of each of the layers when the deposition of a layer results in a slight reduction in the thickness of the lower layer. These layers are generally of identical chemical nature, but they can alternatively be of different chemical natures. The existence of zones of different thicknesses is then obtained by depositing a different number of layers depending on the zones. Thus, the number of layers forming the coating in a first zone is different from the number of layers forming the coating in a second zone.For example, the coating may be formed of a single layer in a first zone and two layers in a second zone, the thickness of the coating in the second zone then being different from that of the coating in the first zone, typically double if the layers have the same thickness.

[0025] Regardless of the embodiment, the number of zones corresponding to different thicknesses is not limited to two. The transparent mineral coating may therefore have, in addition to a first and a second zone, a third zone in which the coating has a third thickness, different from the first and second thicknesses. In general, the transparent mineral coating may comprise N zones Z x (N being at least 2 and x ranging from 1 to N), the thickness e x transparent mineral coating in zone Z x being different from the thickness e ytransparent mineral coating in zone Z y , for all x different from y. For reasons of simplicity, N is preferably at most 10, or even at most 8 and even at most 5.

[0026] By zone we mean areas located in the plane of the coating.

[0027] The visual appearance in reflection of the opaque layer seen through the glass sheet can be varied depending on the thickness of the transparent mineral coating and its refractive index.

[0028] The thickness of the transparent mineral coating in each zone (first, second, or even third and more) is preferably between 30 and 1000 nm, in particular between 50 and 500 nm, or even between 60 and 300 nm.

[0029] Preferably, the ratio between the second thickness and the first thickness is at least 1.2, in particular at least 1.5, or even at least 1.8. It is generally at most 4, or even at most 3. Generally, when the transparent mineral coating comprises N zones Z x , the ratio between the thickness in the Z zone x and the thickness in the Z zone x-1 is preferably at least 1.2, in particular at least 1.5, or even at least 1.8, and often at most 4 or at most 3.

[0030] The refractive index of the transparent mineral coating (typically for a wavelength of 550 nm) is preferably between 1.3 and 2.4, in particular between 1.4 and 2.0. The refractive index, as well as the thickness of the transparent mineral coating, can influence the perceived color. In the case where the transparent mineral coating is formed from a plurality of layers of different chemical natures, the refractive index of the coating corresponds to the average of the refractive indices of each of the layers, weighted by the thickness of each of the layers.

[0031] The transparent mineral coating is preferably based on oxide, nitride or oxynitride of one or more elements selected from Si, Zr, Ti, Zn, Sn and Al. It is preferably based on oxide of one or more elements selected from Si, Zr, Ti, Zn, Sn and Al. The preferred oxides are silicon, zirconium and titanium oxides. Preferably, the transparent mineral coating is based on silicon oxide, in particular is made of silicon oxide. The choice of the element makes it possible to adjust the refractive index of the coating. Silicon oxide (also called silica) has a refractive index of approximately 1.4.

[0032] The transparent mineral coating is preferably a sol-gel coating. In this case, the coating is deposited using a sol-gel process. The sol-gel coating is preferably based on or even composed of silicon oxide. By "based on", we mean that the coating comprises at least 50% by weight of silicon oxide. It may contain other oxides, for example titanium or zirconium, in order to vary the refractive index of the coating.

[0033] A sol-gel process is a process in which a sol containing precursors of the coating to be produced is deposited on the glass sheet by various means, such as spraying, curtain, laminar coating, roller, screen printing, inkjet deposition, etc. Screen printing or inkjet deposition is preferred here since it easily allows the coating to be deposited only in the desired parts.

[0034] The sol preferably contains organometallic precursors of the coating to be produced, for example tetraethyl orthosilicate (TEOS). The coating is then generally dried before depositing the enamel layer and then annealed to densify it. Annealing preferably takes place during the same step as the enamel firing, generally during bending and / or tempering of the glass sheet.

[0035] Alternatively, the coating can be deposited using PVD or CVD (chemical vapor deposition) methods, for example sputtering, or plasma-enhanced chemical vapor deposition (PECVD), possibly under atmospheric pressure (APPECVD). Masks can then be arranged to deposit the coating only in the desired areas. However, these methods are more complex than screen printing or inkjet.

[0036] In the case where the transparent mineral coating comprises, at least in the first or in the second zone, a plurality of superimposed layers, the deposition of the coating comprises successive steps of deposition of each of the layers. It is for example possible to carry out successive screen printing passes using different screen printing screens. A drying step is preferably implemented between two successive layer deposition steps, typically at a temperature between 120 and 200°C.

[0037] When the transparent mineral coating comprises a single layer, the deposition of the coating comprises only one deposition step. In the case of screen printing deposition, obtaining areas of different thicknesses in one step can be achieved by various means, in particular described in application W2018 / 229449.

[0038] Generally speaking, the opaque mineral layer is usually a layer comprising pigments in a mineral binder. The opaque mineral layer is preferably an enamel or a silicate paint.

[0039] The layer is opaque, which means that the light transmission factor in the enameled area is less than 0.1%, namely zero.

[0040] At least one, in particular each, pigment is preferably based on an oxide, or a sulfide, of iron, chromium, copper, cobalt, titanium and / or manganese. The color of the pigments, and therefore of the opaque mineral layer, is not limited: white, black, blue, red, yellow, green, etc. In the case of glazing for vehicles, in particular automobiles, the pigments are preferably black. The opaque mineral layer is then black, and advantageously has a colorimetric coordinate L* in reflection on the enameled face side of less than 5, in particular 3. This measurement excludes specular reflection.

[0041] The term "silicate paint" means a layer obtained from an aqueous paint composition comprising pigments and an aqueous solution of alkali silicate. The layer therefore comprises pigments bound together by a silicate binder.

[0042] The aqueous alkali silicate solution preferably comprises at least one sodium, potassium, and / or lithium silicate. The aqueous alkali silicate solution may consist of a mixture of aqueous solutions of different alkali silicates, for example a mixture of at least one aqueous sodium solution and at least one aqueous potassium solution.

[0043] The paint composition preferably comprises at least one mineral filler, in particular chosen from colloidal silica, feldspars, alumina and lamellar fillers. The lamellar fillers are preferably chosen from talc, mica and clays, in particular silicate or aluminosilicate-based clays such as kaolinite, illite, montmorillonite and sepiolite. The paint composition advantageously comprises a mixture of several of these mineral fillers.

[0044] Mineral fillers and pigments preferably have a particle size distribution (by volume) such that their d90 is less than 10 µm.

[0045] The paint composition may also include a base, in particular an alkali hydroxide.

[0046] The paint composition may further contain various additives, such as at least one dispersing agent, at least one anti-foaming agent, at least one thickening agent, at least one stabilizing agent and / or at least one hardening agent.

[0047] In the mineral paint layer, the weight content of alkali silicate is preferably between 7% and 60%, in particular between 15 and 55%. The total weight content of pigments and mineral fillers is preferably between 20 and 90%, in particular between 30 and 70%. The total content of additives is preferably between 0.1 and 5%. These contents also apply to the aqueous paint composition (it is then a percentage relative to the dry extract).

[0048] By enamel layer we mean both the layer before firing and after firing.

[0049] Before firing, the enamel layer comprises a glass frit, pigments and an organic medium. After firing, the enamel layer comprises pigments and a vitreous or glass-crystalline matrix obtained by melting the glass frit. The glass frit and / or vitreous matrix preferably consists of a zinc and / or bismuth borosilicate glass.

[0050] The enamel layer is preferably obtained by screen printing a fluid enamel composition comprising a glass frit, pigments and an organic medium. To do this, the enamel composition is deposited, in particular using a doctor blade, on the glass sheet through meshes of a screen printing screen. The meshes of the screen are closed in the part corresponding to the areas of the glass sheet that are not to be coated, so that the enamel composition can only pass through the screen in the areas to be printed, according to a predefined pattern. Other deposition techniques such as digital printing techniques, for example by inkjet, are also possible.

[0051] Generally speaking, the opaque mineral layer, and therefore also the silicate paint layer, is advantageously deposited using these different techniques, in particular screen printing or digital printing, particularly inkjet.

[0052] Before firing, the opaque mineral layer, in particular the enamel layer, has a thickness preferably between 10 and 30 µm, in particular between 15 and 25 µm. After firing, the thickness of the opaque mineral layer, in particular the enamel layer, is preferably between 5 and 15 µm, in particular between 7 and 13 µm.

[0053] The method according to the invention preferably comprises a step of firing the opaque mineral layer, in particular the enamel layer, generally during the tempering and / or bending of the glass sheet. If necessary, this step also serves to densify the sol-gel underlayer. This step preferably involves temperatures ranging from 550 to 720°C. The invention then makes it possible to create a decoration with a single firing step.

[0054] In the case of silicate paint, the coated glass sheet may undergo a pre-baking step, intended to harden the paint layer before a possible tempering and / or bending step. Mineral paints based on alkali silicates can usually be hardened at moderate temperatures, in the order of 200 to 250°C.

[0055] Bending can be carried out by gravity (the glass deforms under its own weight) or by pressing, at temperatures typically ranging from 550 to 650°C. In the case of laminated glazing, the two sheets of glass can be bent together (which is the preferred method) or separately. The process can also, before the bending step, include a pre-baking step for the first sheet of glass coated with the opaque layer, preferably at a temperature between 450 and 600°C. Such pre-baking makes it possible to eliminate the organic medium, or generally any organic component possibly present in the opaque layer, and makes it possible to improve the non-stick properties of the latter. It is important to avoid any sticking between the opaque layer and the other sheet of glass, or between the opaque layer and the bending tools.

[0056] The glazing according to the invention may comprise a single sheet of glass. In this case, the glass sheet is preferably thermally toughened. It may alternatively be hardened or annealed.

[0057] Alternatively, the glazing may be laminated glazing, in which the glass sheet of the material according to the invention is adhesively bonded to another glass sheet by means of a lamination interlayer, for example made of polyvinyl butyral. In this case, the glass sheets are not thermally toughened.

[0058] In the case of laminated glazing, the opaque mineral layer, in particular the enamel layer, is preferably placed on face 2 or face 4, i.e. respectively the face opposite the face (called 1) facing the outside (of the vehicle or building) or the innermost face. In this case, the decoration is visible from the outside.

[0059] The glazing may also be multiple glazing, for example double or triple, in which the glass sheet of the material according to the invention is bonded to at least one other glass sheet by means of a peripheral interlayer frame, typically made of metal or polymeric material.

[0060] The glazing according to the invention may be vehicle glazing (land, air, maritime), in particular motor vehicle glazing, such as a rear window, windshield, side window, roof, roof or even quarter panel.

[0061] The glazing can alternatively be building glazing, for example used on a facade or in a window, or be furniture or decorative glazing (partitions, doors, tables, etc.).

[0062] The following examples illustrate the invention in a non-limiting manner.

[0063] illustrates an embodiment of the invention, used in the example. More specifically, it illustrates a schematic sectional view of a material according to the example. The thicknesses of the different elements are obviously not shown to scale.

[0064] A sol-gel silica coating 14 was deposited on a portion of a sheet of clear float glass (sold under the reference Planiclear® by the Applicant). This transparent mineral coating 14 was deposited by screen printing and comprised three zones Z1 to Z3.

[0065] In a first zone Z1, the coating 14 consisted of a single layer of silica 141. In a second zone Z2, the coating 14 consisted of two superimposed silica layers (141 and 142). In a third zone Z3, the coating consisted of three superimposed silica layers (141, 142 and 143). In the example, the thicknesses (e1, e2 and e3) of each of the silica layers were substantially identical. The deposition of the coating 14 was carried out in three successive screen printing steps, with a drying step at 160°C for 180 seconds after each screen printing step. Each layer had a wet thickness of approximately 10 µm.

[0066] On the coating 14, as well as on the part of the glass sheet 10 not coated with the coating 14, a layer of black enamel 12 was deposited. The deposition was also carried out by screen printing, and the thickness of the wet enamel was approximately 25 µm.

[0067] After drying (160°C, 180 seconds), the glass sheet was tempered by heating it to 690°C and then rapidly cooling it using air nozzles.

[0068] After quenching, the visual appearance seen from the uncoated sheet side was characterized in reflection (specular reflection excluded) using a spectrocolorimeter, and the results are presented in the table below.

[0069] ZoneL*a*b*Email only3,70,10,4Z14,00,1-0,6Z26,4-0,3-1,1Z39,1-0,6-1,7

[0070] The results show that, in the case of black enamel, the areas containing the silica coating have a grayer tint in reflection, which becomes grayer the thicker the coating. The contrast between the different areas is sufficient to make decorations perfectly visible.

Claims

Material comprising a glass sheet (10) one face of which comprises an enamelled zone (2), such that in said enamelled zone (2) the glass sheet (10) is coated with an opaque mineral layer (12) and, under at least part of said opaque mineral layer (12), with a transparent mineral coating (14) which is not an enamel, said transparent mineral coating (14) comprising, in said enamelled zone (2), a first zone (Z1) in which the transparent mineral coating (14) has a first thickness (e1) and a second zone (Z2) in which the transparent mineral coating (14) has a second thickness (e2), said first and second thicknesses being different. Material according to claim 1, wherein the opaque mineral layer (12) is an enamel or a silicate paint. Material according to one of the preceding claims, in which the opaque mineral layer (12) is in contact with the transparent mineral coating (14). Material according to one of the preceding claims, in which the transparent mineral coating (14) is such that, deposited on a sheet of clear glass, the light transmission factor is at least 70%, in particular at least 80%. Material according to one of the preceding claims, in which the transparent mineral coating (14) is colorless. Material according to one of the preceding claims, in which the transparent mineral coating (14) comprises, at least in the first (Z1) or in the second zone (Z2, Z3) a plurality of superimposed layers (141, 142, 143). Material according to one of the preceding claims, in which the transparent mineral coating (14) comprises N zones Z x (Z1, Z2, Z3), N being at least 2 and x ranging from 1 to N, the thickness e x transparent mineral coating (14) in zone Z x being different from the thickness e ytransparent mineral coating in zone Z y , for all x different from y. Material according to one of the preceding claims, in which the thickness of the transparent mineral coating (14) in each zone is between 30 and 1000 nm, in particular between 50 and 500 nm. Material according to one of the preceding claims, in which the ratio between the second thickness (e2) and the first thickness (e1) is at least 1.2, in particular at least 1.

5. Material according to one of the preceding claims, in which the transparent mineral coating (14) is based on oxide of one or more elements chosen from Si, Zr, Ti, Zn, Sn and Al, in particular based on silicon oxide. Material according to one of the preceding claims, in which the transparent mineral coating (14) is a sol-gel coating. Method for obtaining a material according to one of the preceding claims, comprising the deposition, on one face of a glass sheet (10) and in a zone called the enameled zone (2), of a transparent mineral coating (14) which is not an enamel, then, on this transparent mineral coating (14), of an opaque mineral layer (12), said transparent mineral coating (14) comprising, in said enameled zone (2), a first zone (Z1) in which the transparent mineral coating (14) has a first thickness (e1) and a second zone (Z2) in which the transparent mineral coating (14) has a second thickness (e2), said first and second thicknesses being different. Method according to the preceding claim, in which the deposition of the transparent mineral coating (14) is carried out by a sol-gel process, and in which the opaque mineral layer (12) is deposited by screen printing or by digital printing. Method according to the preceding claim, in which the deposition of the transparent mineral coating (14) is carried out by screen printing or by inkjet. Glazing comprising a material according to one of claims 1 to 11.

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