WO2024079021A1

WO2024079021A1 - Glass sheet comprising an enamelled zone

Info

Publication number: WO2024079021A1
Application number: PCT/EP2023/077846
Authority: WO
Inventors: Pauline GLATZ; Pauline GIRARD
Original assignee: Saint-Gobain Glass France
Priority date: 2022-10-11
Filing date: 2023-10-09
Publication date: 2024-04-18
Also published as: FR3140624A1

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

Sheet of glass including an enameled area

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

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 deposition of a fluid enamel composition comprising a glass frit, pigments and an organic medium then by firing. Enamel layers are often decorative but can also provide masking and protection functions, for example against ultraviolet radiation.

The aim of the invention is to propose enameled glazing having a decorative appearance seen from the side opposite the side carrying the opaque layer and which can be manufactured in a simple and economical manner.

For this purpose, the subject of the invention is a material comprising a sheet of glass, one side of which comprises an enameled zone, such that in said enameled zone the sheet of glass is coated with an opaque mineral layer and, under at least part of said opaque mineral layer, of a transparent mineral coating which is not an enamel, 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.

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

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

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 side opposite the enameled side. . The reflective 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 decor. This decoration is also obtained in a very simple manner, using a single opaque mineral layer (notably enamel) and possibly after a single firing step.

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 compositions of the borosilicate or aluminosilicate type.

The glass sheet can 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 include other coloring agents, such as cobalt oxide, chromium oxide, nickel oxide, erbium oxide, or even 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%.

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.

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, notably by digital printing, allow these coatings to be deposited on a curved sheet. In the case of glazing for vehicles, particularly for motor vehicles, it is preferably then curved and therefore has a curved shape in the final glazing.

By “enamel zone” we generally mean 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.

The enameled area can cover all or part of the surface of the glass sheet, depending on the intended application. It can cover the entire surface of the glass sheet, for example in the case of spandrels. Alternatively, it can 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, particularly motor vehicles, the enameled zone 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 polymeric seals used for fixing and positioning the glazing in the bodywork windows, as well as various mechanical or electrical elements (heating circuits, mirror bases, sensors or cameras). …).

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

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

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

The transparent mineral coating is present under at least part of the opaque mineral layer. It can 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 for example the case when the transparent mineral coating is intended to form a decoration in only part of the enameled area.

In the two cases previously described, the transparent mineral coating can also be present on all or part of the unglazed zone, when the latter exists. It can then be present on the entire sheet of glass. This is for example the case 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.

The presence of a transparent mineral coating makes it possible to modify the appearance of the enamel seen in reflection through the sheet of glass. It appeared that this aspect 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.

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

In order to obtain an interesting result, the transparent mineral coating preferably has high light transmission. The transparent mineral coating is preferably such that, 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%. By clear glass we mean glass whose chemical composition includes iron oxide as the only coloring agent in a weight content of between 0.05 and 0.12%. As an example of clear glass, we can cite Planiclear® glass marketed by the Applicant.

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.

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.

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 one layer results in a slight reduction in the thickness of the layer below. These layers are generally of the same 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 can be formed of a single layer in a first zone and of 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.

Whatever the embodiment, the number of zones corresponding to different thicknesses is not limited to two. The transparent mineral coating can 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 the second thickness. 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 of the transparent mineral coating in the zone Z _x being different from the thickness e _y of the transparent mineral coating in zone Z _y , for any x different from y. For reasons of simplicity, N is preferably at most 10, or even at most 8 and even at most 5.

By zone we must understand zones located in the plane of the covering.

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

The thickness of the transparent mineral coating in each zone (first, second, 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.

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 zone Z _x and the thickness in zone Z _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.

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 of 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 .

The transparent mineral coating is preferably based on oxide, nitride or oxynitride, of one or more elements chosen from Si, Zr, Ti, Zn, Sn and Al. It is preferably based on oxide of one or more elements chosen 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 consists of silicon oxide. The choice of element allows you to adjust the refractive index of the coating. Silicon oxide (also called silica) has a refractive index of approximately 1.4.

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 or even made up 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.

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

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 in order to densify it. Annealing preferably takes place during the same stage as the firing of the enamel, generally during the bending and/or tempering of the glass sheet.

Alternatively, the deposition of the coating can be carried out by PVD or CVD (chemical vapor deposition) methods, for example by cathode sputtering, or by plasma-assisted chemical vapor deposition (PECVD) optionally under atmospheric pressure ( APPECVD). It is then possible to arrange masks in order to deposit the coating only in the desired parts. However, these methods are more complex than screen printing or inkjet.

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 stages of deposition of each of the layers. For example, it is possible to carry out successive screen printing passes using different screen printing screens. A drying step is preferably carried out between two successive layer deposition steps, typically at a temperature between 120 and 200°C.

When the transparent mineral coating comprises a single layer, the deposition of the coating includes only one deposition step. In the case of deposition by screen printing, obtaining zones of different thicknesses in one step can be obtained by different means, in particular described in application W2018/229449.

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

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

At least one, in particular each, pigment is preferably based on an oxide, or a sulphide, 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, particularly 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 less than 3. This measurement excludes specular reflection.

“Silicate paint” means a layer obtained from an aqueous paint composition comprising pigments and an aqueous alkaline silicate solution. The layer therefore comprises pigments linked together by a silicate binder.

The aqueous alkaline silicate solution preferably comprises at least one sodium, potassium and/or lithium silicate. The aqueous alkaline 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.

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 clays based on silicate or aluminosilicate such as kaolinite, illite, montmorillonite and sepiolite. The paint composition advantageously comprises a mixture of several of these mineral fillers.

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

The paint composition may also include a base, in particular an alkaline hydroxide.

The paint composition may also contain different 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.

In the layer of mineral paint, 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 composition of aqueous paint (it is then a percentage relative to the dry extract).

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

Before firing, the enamel layer includes a glass frit, pigments and an organic medium. After firing, the enamel layer includes pigments and a vitreous or vitrocrystalline matrix obtained by fusion of the glass frit. The glass frit and/or the vitreous matrix is preferably made of zinc and/or bismuth borosilicate glass.

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 the mesh of a screen printing screen. The meshes of the screen are closed in the part corresponding to the areas of the glass sheet which we do not want to coat, so that the enamel composition can only pass through the screen in the areas to be covered. print, according to a predefined pattern. Other deposition techniques such as digital printing techniques, for example by inkjet, are also possible.

Generally speaking, the opaque mineral layer, therefore also the layer of silicate paint, is advantageously deposited by these different techniques, in particular by screen printing or by digital printing, in particular inkjet.

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 of the enamel layer, is preferably between 5 and 15 µm, in particular between 7 and 13 µm.

The process 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 sublayer. This step uses temperatures preferably ranging from 550 to 720°C. The invention then makes it possible to create a decor with a single cooking step.

In the case of a silicate paint, the coated glass sheet can 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 cured at moderate temperatures, around 200 to 250°C.

Bending can in particular be carried out by gravity (the glass deforming 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 curved together (which is the preferred method) or separately. The process can also, before the bending step, a step of pre-baking the first sheet of glass coated with the opaque layer, preferably at a temperature between 450 and 600°C. Such pre-cooking 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 indeed important to avoid any sticking between the opaque layer and the other sheet of glass, or between the opaque layer and the bending tools.

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

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

In the case of laminated glazing, the opaque mineral layer, in particular the enamel layer, is preferably placed on face 2 or on face 4, that is to say respectively the face opposite to the face (called 1 ) facing outwards (of the vehicle or building) or the innermost side. In this case, the decor is visible from the outside.

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

The glazing according to the invention can be vehicle glazing (land, air, sea), in particular motor vehicle glazing, such as rear window, windshield, side window, roof, roof or even quarter window.

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

The examples which follow illustrate the invention in a non-limiting manner.

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

On part of a sheet of clear float glass (sold under the reference Planiclear® by the Applicant) a coating 14 of sol-gel silica was deposited. This transparent mineral coating 14 was deposited by screen printing and comprised three zones Z ₁ to Z ₃ .

In a first zone Z ₁ , the coating 14 consisted of a single layer of silica 141. In a second zone Z ₂ , the coating 14 consisted of two superimposed layers of silica (141 and 142). In a third zone Z ₃ , the coating consisted of three superimposed layers of silica (141, 142 and 143). In the example, the thicknesses (e ₁ , e ₂ and e ₃ ) 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.

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

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

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

ZoneArea	LL	ahas	bb
Email seulEmail only	3,73.7	0,10.1	0,40.4
Z₁ Z ₁	4,04.0	0,10.1	-0,6-0.6
Z₂ Z ₂	6,46.4	-0,3-0.3	-1,1-1.1
Z₃ Z ₃	9,19.1	-0,6-0.6	-1,7-1.7

The results show that, in the case of a black enamel, the areas comprising the silica coating present a grayer tint in reflection, even more gray as the thickness of the coating is high. The contrast between the different zones is sufficient to make decorations perfectly visible.

Claims

Material comprising a sheet of glass (10) one side of which comprises an enameled zone (2), such that in said enameled zone (2) the sheet of glass (10) is coated with an opaque mineral layer (12) and, under at least part of said opaque mineral layer (12), of a transparent mineral coating (14) which is not an enamel, said transparent mineral coating (14) comprising, in said enameled zone (2), a first zone (Z 1 ) in which the transparent mineral coating (14) has a first thickness (e 1 ) and a second zone (Z 2 ) in which the transparent mineral coating (14) has a second thickness (e 2 ), said first and second thicknesses being different.
Material according to claim 1, in which 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 (Z 1 ) or in the second zone (Z 2 , Z 3 ) a plurality of layers (141, 142, 143) superimposed.
Material according to one of the preceding claims, in which the transparent mineral coating (14) comprises N zones Z x (Z 1 , Z 2 , Z 3 ), N being at least 2 and x ranging from 1 to N, l the thickness e x of the transparent mineral coating (14) in the zone Z x being different from the thickness e y of the transparent mineral coating in the zone Z y , for any 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 (e 2 ) and the first thickness (e 1 ) 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 an oxide of one or more elements chosen from Si, Zr, Ti, Zn, Sn and Al, in particular based on oxide of silicon.
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 sheet of glass (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), an opaque mineral layer (12), said transparent mineral coating (14) comprising, in said enameled zone (2), a first zone (Z 1 ) in which the transparent mineral coating (14) has a first thickness (e1) and a second zone (Z 2 ) in which the transparent mineral coating (14) has a second thickness (e 2 ), 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 inkjet.
Glazing comprising a material according to one of claims 1 to 11.