EP4118043A1 - Glass sheet coated with a stack of thin layers and an enamel layer - Google Patents

Abstract

The invention relates to a material comprising a glass sheet coated on at least a part of one of its faces with a stack of thin layers, said stack being coated on at least part of its surface with an enamel layer that does not comprise bismuth, wherein said enamel layer is coated with an anti-adhesive layer.

Description

Glass sheet coated with a stack of thin layers and a layer of enamel

The invention relates to the field of materials comprising a glass sheet coated with a stack of thin layers and with a layer of enamel. Such materials are in particular intended to be incorporated into curved laminated glazing for motor vehicles, for example for roofs or windshields. Laminated glazing is glazing in which two sheets of glass are adhesively bonded by means of a lamination interlayer. The latter makes it possible in particular to retain shards of glass in the event of breakage, but also provides other functionalities, in particular in terms of resistance to burglary or improvement of acoustic properties.

These glazings often include coatings of various types, intended to impart different properties.

Enamel layers, generally black and opaque, are often deposited on part of the glazing, generally in the form of a peripheral strip intended to conceal and protect against ultraviolet radiation the polymeric seals used for fixing and positioning the glazing on the bodywork bay. Enamelled areas also conceal the fixing areas of the interior mirror and various connectors and sensors.

In laminated glazing, these enamel layers are generally placed on face 2, the faces being traditionally numbered from the face intended to be positioned outside the vehicle. Face 2 is therefore a face in contact with the lamination interlayer. The aesthetic appearance of the enamel layer seen from

SUBSTITUTE SHEET (RULE 26) the exterior of the vehicle is of particular importance to vehicle manufacturers. The enamel is generally obtained by firing above 500 ° C. of a composition comprising a glass frit and pigments. A glass frit consists of fine particles of a low-melting point glass, which under the effect of a heat-firing treatment softens and adheres to the glass sheet. A generally opaque mineral layer is thus formed, with high chemical and mechanical resistance, adhering perfectly to the glass while maintaining the pigment particles. The baking step is generally carried out simultaneously with the bending of the glass sheet.

In the context of the manufacture of laminated glazing, the two sheets of glass of the glazing are bent together, the sheet of glass intended to be positioned inside the vehicle being generally disposed above the other sheet of glass, which wears enamel. It is then necessary for the enamel to have non-stick properties in order to prevent any sticking between the two sheets of glass during bending. To do this, we usually use enamels containing bismuth, that is to say obtained from glass frits containing bismuth oxide.

Coatings, generally in the form of stacks of thin layers, can also be present on one of the glass sheets of the laminated glazing. They can in particular be electrically conductive layers, which can provide two types of functionalities. The electrically conductive layers can on the one hand, when current leads are provided, dissipate heat by the Joule effect. These are then heating layers, useful for example for defrosting or demisting. These layers have on the other hand, by their reflection of infrared radiation, properties of solar control or low emissivity. Layers are then appreciated for improving thermal comfort or for the energy savings they provide, by reducing consumption intended for heating or air conditioning. These stacks of layers are generally placed on face 3 of the laminated glazing, therefore also in contact with the lamination interlayer.

It may however be advantageous, in certain cases which will be detailed below, to have the enamel layer and the stack of thin layers on the same sheet of glass, and therefore on the same face of the sheet of glass in question. so that these coatings are protected inside the laminated glazing.

It was however observed that when a glass sheet coated with a stack of thin layers had to be provided with a layer of enamel containing bismuth (therefore non-stick), undesirable interactions occurred during the bending between the stack. and enamel, leading in particular to a degradation of the aesthetic appearance of the enamel. It was observed in particular, when the stack contained at least one nitride layer, that bubbles were created within the enamel, near the interface between the latter and the stack, causing a significant drop in adhesion. enamel, modifying its optical appearance (in particular the color on the glass side, that is to say on the side opposite to the enamel) and reducing its chemical resistance, in particular to acids.

Several solutions have been proposed to this problem.

It is possible to remove the stack of thin layers beforehand at the places where the enamel layer is to be deposited, for example by means of abrasives, so that the enamel is deposited in direct contact with the glass sheet and 'avoid any problems of adhesion between the enamel layer and the stack of thin layers. Mechanical abrasion However, there are visible scratches, including on the enamel layer.

Application WO 2014/133929 proposes the idea of using special glass frits for enamel which are capable, during firing, of dissolving the stack of thin layers in order to attach themselves directly to the glass. However, such methods are expensive.

Application WO 2019/106264, for its part, proposes modifying the stack of thin layers by adding an oxide layer between the stack and the enamel comprising bismuth.

The aim of the invention is to propose a simpler and less expensive solution to the aforementioned problem.

To this end, the invention relates to a material comprising a sheet of glass coated on at least part of one of its faces with a stack of thin layers, said stack being coated on at least part of its surface with 'an enamel layer not comprising bismuth, said enamel layer being coated with an anti-adhesion layer.

The subject of the invention is also a process for obtaining a material according to the invention, comprising the following steps:

- the supply of a glass sheet coated on at least part of one of its faces with a stack of thin layers then

- a step of depositing, on at least part of the surface of the stack of thin layers, a layer of enamel not comprising bismuth then

a step of depositing, on said enamel layer, an anti-adhesion layer.

The subject of the invention is also a curved laminated glazing, in particular for a vehicle windshield or roof. automobile, comprising a material according to the invention, adhesively bonded to an additional sheet of glass by means of a lamination interlayer, so that the enamel layer and the stack of thin layers face towards said interlayer, in particular either opposite 2 of the glazing.

Finally, a subject of the invention is a process for obtaining a curved laminated glazing as defined above, comprising the following steps:

- the supply of a material according to the invention or obtained according to the aforementioned method and of an additional sheet of glass, then

- a step of simultaneous bending of the material and of the additional glass sheet, then

a step of laminating said material with the additional glass sheet by means of a lamination interlayer, so that the enamel layer and the stack of thin layers are turned towards said interlayer.

Contrary to what is proposed in the aforementioned application WO 2014/133929, the stack of thin layers is not degraded by the deposition of the enamel. The material according to the invention therefore has, superposed, a stack of thin layers then a layer of enamel, the latter not being in contact with the glass sheet.

The use of an enamel layer not containing bismuth makes it possible to avoid any undesirable interaction during bending, in particular with stacks of thin layers comprising at least one layer based on a nitride. However, since these enamels do not make it possible to avoid bonding between the two glass sheets during bending, an anti-adhesion layer is placed on the enamel layer.

The term “anti-adhesion” layer is understood to mean a layer capable of preventing the sticking of the two sheets of glass during bending. The glass sheet can be flat or curved. The glass sheet is generally flat at the time of deposition of the stack of thin layers and then of the enamel layer, and is then curved. The glass sheet is therefore normally flat in the material according to the invention (intermediate product) and curved in the curved laminated glazing according to the invention (final product).

The glass is typically a soda-lime glass, but other glasses, for example borosilicates or aluminosilicates can also be used. The glass sheet is preferably obtained by floating, that is to say by a process consisting in pouring molten glass onto a bath of molten tin.

The glass sheet may be clear glass or tinted glass, preferably tinted glass, for example green, gray or blue. To do this, the chemical composition of the glass sheet advantageously comprises iron oxide, in a weight content ranging from 0.5 to 2%. It can also comprise other coloring agents, such as cobalt oxide, chromium oxide, nickel oxide, erbium oxide, or else selenium.

The glass sheet preferably has a thickness within a range ranging from 0.7 to 19 mm, in particular from 1 to 10 mm, particularly from 2 to 6 mm, or even from 2 to 4 mm.

The lateral dimensions of the glass sheet are to be adapted as a function of those of the laminated glazing in which it is intended to be integrated. The glass sheet preferably has a surface area of at least 1 m ² .

The glass sheet is preferably coated with the stack of thin layers over at least 70%, in particular over at least 90%, or even over the entire surface of the face of the glass sheet. Some areas may indeed not to be coated in order in particular to provide communication windows allowing waves to pass.

The stack is preferably coated with the enamel layer over 2 to 25%, in particular 3 to 20%, or even 5 to 15% of its surface. The enamel layer preferably comprises a peripheral strip, that is to say a strip closed on itself which, from each point of the periphery of the glass sheet, extends towards the interior of the sheet. of glass over a certain width, typically between 1 and 20 cm.

The anti-stick layer preferably coats the entire enamel layer. Advantageously, the anti-adhesion layer only coats the enamel layer; it is then not present in the uncoated areas of the enamel layer.

The stack of thin layers is preferably in contact with the glass sheet. The enamel layer is preferably in contact with the stack of thin layers. The anti-adhesion layer is preferably in contact with the enamel layer. In this text, the stack of thin layers, the enamel layer and the anti-stick layer are collectively referred to as "the coatings". The material according to the invention preferably consists of these coatings.

By “contact” is meant in the present text a physical contact. The expression “based on” preferably means the fact that the layer in question comprises at least 50% by weight of the material considered, in particular 60%, or even 70% and even 80% or 90%. The layer may even essentially consist of or consist of this material. By “essentially consist”, it should be understood that the layer can comprise impurities without influence on its properties. The terms "oxide" or "nitride" do not necessarily mean that the oxides or nitrides are stoichiometric. They can in fact be substoichiometric, superstoichiometric or stoichiometric.

The stack preferably comprises at least one layer based on a nitride. The nitride is in particular a nitride of at least one element chosen from aluminum, silicon, zirconium and titanium. It can comprise a nitride of at least two or three of these elements, for example a nitride of silicon and zirconium, or a nitride of silicon and aluminum. Preferably, the layer based on a nitride is a layer based on silicon nitride, more particularly a layer consisting essentially of a silicon nitride. When the silicon nitride layer is deposited by cathodic sputtering, it generally contains aluminum, since it is customary to dope silicon targets with aluminum in order to accelerate the deposition rates.

The layer based on a nitride preferably has a physical thickness in a range ranging from 2 to 100 nm, in particular from 5 to 80 nm.

Nitride-based layers are commonly used in a number of stacks of thin layers because they have advantageous blocking properties, in the sense that they prevent the oxidation of other layers present in the stack, in particular functional layers. which will be described below.

The stack preferably comprises at least one functional layer, in particular an electrically conductive functional layer. The functional layer is preferably between two thin dielectric layers, at least one of which is a nitride-based layer. Other possible dielectric layers are, for example, layers of oxides or oxynitrides. At least one electrically conductive functional layer is advantageously chosen from:

- metallic layers, in particular made of silver or niobium, or even gold, and

- the layers of a transparent conductive oxide, in particular chosen from indium tin oxide, doped tin oxides (for example with fluorine or with antimony), doped zinc oxides (for example aluminum or gallium).

These layers are particularly appreciated for their low emissivity, which gives the glazing excellent thermal insulation properties. In the glazing fitted to land vehicles, in particular automobiles, railways, or even air or sea vehicles, low-emissive glazing makes it possible in hot weather to reflect part of the solar radiation to the outside, and therefore to limit the heating of the interior of said vehicles, and where appropriate reduce air conditioning expenses. Conversely, in cold weather, these glazings make it possible to conserve heat within the passenger compartment, and consequently to reduce the heating energy effort. It is the same in the case of glazing equipping buildings.

According to a preferred embodiment, the stack of thin layers comprises at least one layer of silver, in particular one, two or three, or even four layers of silver. The physical thickness of the silver layer or, where appropriate, the sum of the thicknesses of the silver layers is preferably between 2 and 20 nm, in particular between 3 and 15 nm.

According to another preferred embodiment, the stack of thin layers comprises at least one layer of indium tin oxide. Its physical thickness is preferably between 30 and 200 nm, in particular between 40 and 150 nm. In order to protect the or each thin electroconductive layer (whether metallic or based on a transparent conductive oxide) during the bending step, each of these layers is preferably surrounded by at least two dielectric layers. The dielectric layers are preferably based on the oxide, nitride and / or oxynitride of at least one element chosen from silicon, aluminum, titanium, zinc, zirconium and tin.

At least part of the stack of thin layers can be deposited by various known techniques, for example by chemical vapor deposition (CVD), or by cathodic sputtering, in particular assisted by a magnetic field (magnetron process).

The stack of thin layers is preferably deposited by cathode sputtering, in particular assisted by a magnetic field. In this process, a plasma is created under a high vacuum in the vicinity of a target comprising the chemical elements to be deposited. The active species of the plasma, by bombarding the target, tear off said elements, which are deposited on the glass sheet, forming the desired thin layer. This process is said to be “reactive” when the layer consists of a material resulting from a chemical reaction between the elements torn from the target and the gas contained in the plasma. The major advantage of this process lies in the possibility of depositing on the same line a very complex stack of layers by successively making the glass sheet scroll under different targets, generally in one and the same device.

The aforementioned stacks have properties of electricity conduction and infrared reflection useful for providing a heating function (defrosting, demisting) and / or a thermal insulation function.

When the stack of thin layers is intended to provide a heating function, current leads must be planned. They may in particular be strips of silver paste deposited by screen printing on the stack of thin layers, at two opposite edges of the glass sheet.

The enamel layer is preferably formed from a composition comprising at least one pigment and at least one glass frit. The enamel layer preferably does not include lead oxide.

The enamel composition generally also comprises an organic medium, intended to facilitate the application of the composition to the substrate as well as its temporary adhesion to the latter, and which is eliminated during the firing of the enamel. The medium typically includes solvents, diluents, oils and / or resins. In the present text, the term “enamel composition” is used to describe the liquid composition which is used to deposit, on the glass sheet, a layer of wet enamel. The term "enamel layer" is used to describe the final layer, after firing, while the term "wet enamel layer" is used to describe the enamel layer before firing.

The enamel layer is preferably deposited by screen printing. To do this, a silkscreen screen is placed on the sheet of glass, which comprises meshes, some of which are sealed, then the enamel composition is deposited on the screen, then a doctor blade is applied in order to force the composition of enamel to pass through the screen in areas where the mesh of the screen is not sealed, so as to form a layer of wet enamel.

The deposition of the enamel layer comprises a baking step, preferably at a temperature of at least 600 and even 650 ° C, and at most 700 ° C, preferably during a subsequent bending treatment of the glass sheet. The pigments preferably comprise one or more oxides chosen from oxides of chromium, copper, iron, manganese, cobalt and nickel. It may be, for example, chromates of copper and / or iron. In a preferred embodiment of the invention, the enamel layer is based on zinc borosilicate.

More particularly, the enamel layer advantageously has a chemical composition comprising the following oxides, in weight contents varying within the limits mentioned below: B2O3 2-20%, in particular 4-10% S1O2 20-45%, in particular 25 -40% B12O3 0

ZnO 8-25%, in particular 10-20% The composition advantageously comprises at least one alkali metal oxide, in particular of potassium, in contents of at most 5% and / or sodium, in contents ranging from 2 to 15%, in particular from 5 to 13%. The composition preferably contains titanium oxide (T1O2), in contents ranging from 1 to 10%, in particular from 2 to 7%. The composition also includes pigments, for example copper chromates. In this case, the typical Cr0 ₃ and CuO contents range from 8 to 20% and from 3 to 12% respectively.

The chemical composition of the enamel can be determined by conventional chemical analysis methods, especially from baked enamel. It is therefore indeed the chemical composition of the baked enamel layer, and not the glass frit which was used to form the enamel.

Preferably the enamel layer is opaque, black in color. Its clarity L * measured in reflection on the glass side is preferably less than 5. As indicated above, it advantageously forms a strip at the periphery of the glass sheet. In this way, the enamel layer is able to conceal and protect against ultraviolet radiation seals, connection elements, or sensors.

The anti-adhesion layer is preferably a layer based on refractory particles (in particular pigments) or a sol-gel layer. The anti-adhesion layer preferably does not contain bismuth because it has been observed that the presence of bismuth could generate defects, even when the anti-adhesion layer is not in contact with the stack of thin layers.

The term “refractory particles” is understood to mean particles which do not undergo transformation during bending.

The refractory particles can be for example alumina particles. The refractory particles can advantageously be pigments.

The pigments preferably comprise one or more oxides of transition metals, in particular chosen from oxides of chromium, copper, iron, manganese, cobalt, nickel and titanium.

Preferably, the pigments are titanium oxide pigments, which exhibit excellent non-stick properties. Although these pigments are white (while the enamel is generally black) these pigments do not change the appearance of the enamel when viewed from the exterior of the vehicle. When, in the final laminated glazing, the additional glass sheet or the lamination interlayer is tinted, the color imparted by these pigments is not detrimental to the aesthetics seen from the interior of the passenger compartment either.

The pigment-based layer preferably comprises at least 40%, in particular at least 60%, or even at least 80% by weight, of pigments.

According to a preferred embodiment, the anti-adhesion layer consists of pigments. These pigments are attached to the glass sheet thanks to the underlying enamel layer: its softening during bending makes it possible to fix the pigments deposited above it.

According to another embodiment, the layer anti ^¬ adhesion includes pigments and a vitreous binder. The vitreous binder does not include bismuth, and can be based on the same glass frit as the underlying enamel. To obtain the non-stick property, the mass proportion of pigment in the anti-stick layer should be at least 40% by weight. A very simple way to obtain this type of layer consists in adding a certain proportion of pigments to an enamel composition identical to that which was used to deposit the underlying enamel layer.

According to yet another embodiment, the anti-adhesion layer is a sol-gel layer. The term “sol-gel layer” is understood to mean a layer obtained by a sol-gel process. The sol-gel layer is preferably based on silica.

A sol-gel process is a process in which a sol containing precursors of the layer to be produced is deposited on the glass sheet by various means, such as spraying, curtain, laminar coating, roller, screen printing etc. .... Deposition by screen printing is preferred here since it easily makes it possible to deposit the sol-gel layer only on a part of the glass sheet, in this case only on the area covered with enamel (and advantageously on this whole area).

The sol preferably contains organometallic precursors of the layer to be produced, for example tetraethyl orthosilicate (TEOS). The layer is then generally dried and then annealed in order to densify it. The annealing preferably takes place during the same step as the baking of the enamel, therefore generally during the bending of the glass sheet. The anti-adhesion layer preferably has a thickness (in particular in the wet state) of between 5 and 100 μm. When the layer is based on refractory particles, its thickness is preferably between 10 and 100 μm, in particular between 12 and 30 μm. When the layer is a sol-gel layer, its thickness is preferably between 5 and 20 μm.

Preferably, the step of depositing the enamel layer and the step of depositing the anti-adhesion layer are carried out by screen printing.

In the case where the anti-adhesion layer consists of pigments, the pigments are mixed with an organic medium, which is then removed during bending or during a possible pre-baking.

The step of depositing the enamel layer is preferably followed by a drying step, typically at a temperature between 100 and 200 ° C., before depositing the anti-adhesion layer.

In the case of deposition by screen printing of an anti-adhesion layer based on refractory particles, the latter must have a size compatible with the screen printing screen used. The particles preferably have an D90 of between 5 and 40 μm. The particle size distribution is here a volume distribution, determined for example by laser particle size distribution.

The step of depositing the anti-adhesion layer is preferably followed by a pre-curing step, preferably at a temperature between 150 and 600 ° C. Such a pre-baking makes it possible to eliminate the organic medium, or in general any organic component possibly present in the layer.

A pre-baking step is usually carried out in the case of the use of bismuth-based enamels, in order to to develop the non-stick properties of such an enamel by causing its partial crystallization. This step must however be carried out at high temperature, typically at least 500 ° C., while the pre-cooking carried out in the context of the present process can advantageously be carried out at lower temperatures.

In laminated curved glazing, the material according to the invention is adhesively bonded to an additional sheet of glass by means of a lamination interlayer, so that the coatings are facing said interlayer. The coatings are preferably positioned on face 2 of the glazing, that is to say on the face of the glass sheet intended to be positioned on the outside of the vehicle facing the laminating insert.

The 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. The glass sheets are preferably kept at a distance by placing between them an intermediate powder ensuring a space of a few tens of micrometers, typically 20 to 50 μm. The intermediate powder is for example based on calcium carbonate and / or magnesium.

During bending, the inner sheet of glass (intended to be positioned inside the passenger compartment) is normally placed above the outer sheet of glass. Thus, during the bending step, the additional glass sheet is placed on top of the material according to the invention.

The laminating step can be carried out by treatment in an autoclave, for example at temperatures of 110 to 160 ° C. and under a pressure ranging from 10 to 15 bars. Prior to the autoclave treatment, the air trapped between the glass sheets and the lamination interlayer can be removed by calendering or by vacuum. As said previously, the additional sheet is preferably the inner sheet of the laminated glazing, that is to say the sheet located on the concave side of the glazing, intended to be positioned inside the passenger compartment of the vehicle. In this way, the coatings are placed on face 2 of the laminated glazing.

The additional glass sheet may be soda-lime-silicate glass, or else of borosilicate or aluminosilicate glass. It can be in clear or tinted glass. Its thickness is preferably between 0.5 and 4 mm, in particular between 1 and 3 mm.

According to a preferred embodiment, the additional glass sheet has a thickness of between 0.5 and 1.2 mm. The additional glass sheet is in particular made of sodium aluminosilicate glass, preferably chemically reinforced. The additional glass sheet is preferably the inner sheet of the laminated glazing. The invention is particularly useful for this type of configuration, for which it is difficult to place the stack of thin layers on the face 3. Chemical reinforcement (also called “ion exchange”) consists in bringing the surface of the glass into contact with it. a molten potassium salt (for example potassium nitrate), so as to strengthen the surface of the glass by exchanging ions of the glass (here sodium ions) with ions of greater ionic radius (here potassium ions). This ion exchange makes it possible to form compressive stresses on the surface of the glass and over a certain thickness. Preferably, the surface stress is at least 300 MPa, in particular 400 and even 500 MPa, and at most 700 MPa, and the thickness of the zone in compression is at least 20 μm, typically between 20 μm. and 50 pm. The stress profile can be determined in a known manner using a polarizing microscope equipped with a Babinet compensator. Step of Chemical quenching is preferably carried out at a temperature ranging from 380 to 550 ° C, and for a period ranging from 30 minutes to 3 hours. The chemical reinforcement is preferably carried out after the bending step but before the laminating step. The glazing obtained is preferably a motor vehicle windshield, in particular a heated windshield.

According to another preferred embodiment, the additional sheet of glass carries on the face opposite to the face facing the laminating insert (preferably face 4, the additional sheet being the inner sheet) a stack of additional thin layers, in particular a low emissivity stack, comprising a transparent conductive oxide, in particular indium tin oxide (ITO). The invention is also particularly useful for this type of configuration, for which it is difficult to arrange stacks of thin layers on both sides of the same sheet of glass (face 3 and 4). In this embodiment, the lamination interlayer and / or the additional glass sheet is preferably tinted, the glass sheet carrying the coatings possibly being of clear glass. The glazing obtained is preferably a motor vehicle roof.

As an example of this last preferred embodiment, there may be mentioned a laminated curved roof comprising, from the outside of the vehicle, a sheet of clear glass coated on the face 2 with a stack of thin layers comprising at least one layer of silver. then a layer of enamel then a non-stick layer, a tinted PVB lamination interlayer, and an additional sheet of tinted glass, bearing on face 4 a stack of thin layers with low emissivity, in particular at ITO base. 1 / laminating interlayer preferably comprises at least one sheet of polyvinylacetal, in particular of polyvinylbutyral (PVB).

1 / the lamination interlayer can be tinted or non-tinted in order, if necessary, to regulate the optical or thermal properties of the glazing.

1 / laminating interlayer can advantageously have sound absorption properties in order to absorb sounds of aerial or solidary origin. For this purpose, it may in particular consist of three polymeric sheets, including two so-called external PVB sheets flanking an internal polymeric sheet, optionally made of PVB, of lower hardness than that of the external sheets.

The lamination interlayer can also have thermal insulation properties, in particular reflection of infrared radiation. For this purpose, it may comprise a coating of thin low emissivity layers, for example a coating comprising a thin layer of silver or a coating of alternating dielectric layers of different refractive indices, deposited on an internal PET sheet framed by two external PVB sheets.

The thickness of the lamination interlayer is generally within a range ranging from 0.3 to 1.5 mm, in particular from 0.5 to 1 mm. The lamination interlayer may have a lower thickness on one edge of the glazing than in the center of the glazing in order to avoid the formation of a double image when using a head-up vision system, called HUD ( head-up display).

The exemplary embodiments which follow illustrate the invention in a nonlimiting manner.

Glass sheets 2.1 mm thick, previously coated by sputtering with a stack of thin layers comprising two layers of silver protected by layers of zinc oxide, layers of silicon nitride and NiCr blockers, were coated by screen printing with layers of enamel with a wet thickness of 25 μm.

In the examples according to the invention, the enamel layer “El” (enamel marketed by the company Ferro under the reference 144011) was based on a zinc borosilicate frit (without bismuth) and black pigments based on D. oxides of chromium and copper.

In comparative examples, the enamel layer “E2” (enamel sold by the company Prince under the reference DV173770 / N) was based on a frit of bismuth and zinc borosilicate and on black pigments based on oxides. of chromium and copper.

On the enamel layer, after drying at a temperature of 150 ° C, was then deposited, by screen printing, an anti-adhesion layer, of the following composition according to the examples:

Al: TiCp pigments, wet thickness approximately 10 μm, having an D50 of the order of 3 to 5 μm and a D90 of the order of 10 μm.

A2: sol-gel silica, wet thickness approximately 7 μm, deposited from a solution marketed under the reference TLU0059B01 by the company Ferro

A3: enamel layer E2, wet thickness 25 µm

A4: mixture of 80% by weight of E1 enamel with 20% by weight of TiCp pigments, wet thickness of 10 μm.

The glass sheet thus coated was then subjected to a pre-baking treatment at 570 ° C. for 120 seconds. An additional glass sheet of 2.1 mm thick tinted glass covered on face 4 with a low-emissive stack based on ITO was then placed on the glass sheet, on the coating side. An intermediate powder providing a space of a few tens of micrometers based on calcium carbonate was interposed between the two sheets of glass. The assembly then underwent a bending heat treatment at 600 ° C. for 480 seconds.

Table 1 below summarizes the results obtained, indicating for each example (comparative examples C1 to C3 and examples according to the invention 1 to 3), the nature of the enamel layer and of the anti-adhesion layer (when 'she was present), as well as the results in terms of aesthetics and bonding. Aesthetics, more particularly the black color seen from face 1, is evaluated by measuring the clarity L * in reflection (illuminant D65, reference observer 10 °). The collage is qualitatively assessed by visual observation.

[Table 1]

Comparative Examples C1 and C2 do not use an anti-adhesion layer. Example C1 shows that enamels at bismuth, if they do not cause sticking, do not make it possible to obtain the desired black shade, due to interactions between the enamel and the stack of thin layers during bending. The bismuth-free enamel of Comparative Example C2 makes it possible to achieve the desired shade, but a bond between the two sheets of glass is observed.

Comparative Example C3 uses a bismuth-free enamel in contact with the stack, topped with a bismuth enamel in contact with the additional glass sheet. Bonding is then avoided, but the presence of the bismuth enamel, even if it is not in contact with the stack of thin layers, degrades the aesthetics.

Examples 1 to 3 according to the invention show that the use of an anti-adhesion layer in combination with an enamel without bismuth makes it possible to obtain both an absence of sticking and a satisfactory aesthetic appearance.

Claims

Claims

1. Material comprising a sheet of glass coated on at least part of one of its faces with a stack of thin layers, said stack being coated on at least part of its surface with a layer of enamel not comprising of bismuth, said enamel layer being coated with an anti-adhesion layer.

2. Material according to claim 1, wherein the stack of thin layers comprises at least one layer based on a nitride, in particular a nitride of at least one element chosen from aluminum, silicon, zirconium. , titanium.

3. Material according to one of the preceding claims, such that the stack comprises at least one functional layer, in particular an electrically conductive functional layer.

4. Material according to the preceding claim, in which at least one electrically conductive functional layer is chosen from metal layers, in particular made of silver or niobium, and the layers of a transparent conductive oxide, in particular chosen from the oxide of indium and tin, doped tin oxides, doped zinc oxides.

5. Material according to one of the preceding claims, such that the enamel layer is based on zinc borosilicate.

6. Material according to one of the preceding claims, such that the enamel layer is opaque, black in color, and forms a band on the periphery of the glass sheet.

7. Material according to one of the preceding claims, wherein the anti-adhesion layer is a layer based on refractory particles, in particular pigments.

8. Material according to one of claims 1 to 6, wherein the anti-adhesion layer is a sol-gel layer, in particular based on silica.

9. Laminated curved glazing, in particular for the windshield or roof of a motor vehicle, comprising a material according to one of the preceding claims, adhesively bonded to an additional glass sheet by means of a lamination interlayer, so that the layer enamel and the stack of thin layers are turned towards said interlayer, in particular are on face 2 of the glazing.

10. Laminated curved glazing according to the preceding claim, wherein the additional glass sheet has a thickness between 0.5 and 1.2 mm, in particular is chemically reinforced sodium aluminosilicate glass.

11.Laminated curved glazing according to claim 9, in which the additional glass sheet carries, on the face opposite to the face facing the laminating insert, an additional stack of thin layers, in particular a low-emissivity stack comprising an oxide. transparent conductive.

12. A method of obtaining a material according to one of claims 1 to 8, comprising the following steps:

- the supply of a glass sheet coated on at least part of one of its faces with a stack of thin layers then

- a step of depositing, on at least part of the surface of the stack of thin layers, a layer of enamel not comprising bismuth then

a step of depositing, on said enamel layer, an anti-adhesion layer.

13. Method according to the preceding claim, in which the step of depositing the enamel layer and the step of depositing the anti-adhesion layer are carried out by screen printing.

14. A method of obtaining a curved laminated glazing according to one of claims 9 to 11, comprising the following steps:

- the supply of a material according to one of claims 1 to 8 or obtained according to the process of one of claims 12 or 13 and of an additional glass sheet, then

- a step of simultaneous bending of the material and of the additional glass sheet, then

a step of laminating said material with the additional glass sheet by means of a lamination interlayer, so that the enamel layer and the stack of thin layers are turned towards said interlayer.