Glass sheet coated with a sol-gel layer and a thin-film stack

Abstract

The invention relates to a material comprising a glass sheet, one of the faces of which comprises a first region and a second region, only the first region being coated with a sol-gel layer, and the sol-gel layer and the second region of the glass sheet being coated with a stack of thin films comprising at least one electrically conductive thin film. The invention further relates to a laminated glazing comprising such a material.

Description

[0001] Description

[0002] Title: Glass sheet coated with a sol-gel layer and a stack of thin layers

[0003] The invention relates to the field of glazing, in particular automotive glazing, such as windshield or roof glazing for motor vehicles.

[0004] Such glazing is often laminated glass, in which two sheets of glass are bonded together with an adhesive interlayer. This interlayer helps to hold glass fragments together in case of breakage, but also provides other functionalities, particularly in terms of burglary resistance and improved acoustic properties.

[0005] These windows often include coatings of various types, designed to impart different properties.

[0006] Layers of enamel, usually black and opaque, are often applied to part of the glazing, generally as a peripheral strip designed to conceal and protect against ultraviolet radiation the polymer seals used to fix and position the glazing on the body frame. In laminated glazing, these enamel layers are usually located on surface 2, with surfaces traditionally numbered starting from the surface intended to face the exterior of the vehicle. Surface 2 is therefore in contact with the interlayer. The aesthetic appearance of the enamel layer as seen from the outside of the vehicle is of particular importance to car manufacturers. The enamel is generally obtained by firing a composition containing a glass frit and pigments at temperatures above 500°C. The firing process is usually carried out simultaneously with the curing of the glass sheet.Coatings, generally in the form of stacked thin layers, may also be present on one of the glass panes of laminated glazing. These may include electrically conductive layers, which can provide two types of functionality. Firstly, when current is supplied, these electrically conductive layers can dissipate heat through the Joule effect. These are then heating layers, useful, for example, for defrosting or demisting. Secondly, these layers, by reflecting infrared radiation, offer solar control or low-emissivity properties. These layers are therefore valued for improving thermal comfort or for the energy savings they provide by reducing heating or air conditioning consumption. These stacked layers are generally located on surface 3 of the laminated glazing, and are therefore also in contact with the interlayer.

[0007] In some cases, it can be advantageous to place the enamel layer and the thin-film stack on the same sheet of glass, and therefore on the same face of the glass sheet, so that these coatings are protected within the laminated glass. The enamel can be deposited on top of the thin-film stack, but any interactions that may occur between the two coatings during the enamel firing process can negatively impact the enamel's appearance. Another possibility is to deposit the thin-film stack directly onto the enamel. This requires pre-firing the enamel and carefully controlling its roughness. However, the remelting of the enamel during the firing process and the resulting interactions with the thin-film stack can degrade the enamel's appearance and / or the electrical conductivity of the stack.The invention aims to overcome these drawbacks by proposing a solution that combines good aesthetics and good electrical conductivity.

[0008] For this purpose, the invention relates to a material comprising a sheet of glass, one of whose faces comprises a first zone and a second zone, only the first zone being coated with a sol-gel layer, the sol-gel layer and the second zone of the sheet of glass being coated with a stack of thin layers comprising at least one electroconductive thin layer.

[0009] The invention also relates to a method for obtaining a material according to the invention, comprising the following steps:

[0010] - the supply of a sheet of glass, one face of which comprises a first zone and a second zone, then

[0011] - a deposition step on the first zone of a precursor soil of the soil-frost layer, then

[0012] - a pre-baking stage at a temperature of at least 200°C, in order to obtain a sol-gel layer, then

[0013] - a deposition step, on the sol-gel layer and on the second zone of the glass sheet, of a stack of thin films comprising at least one electrically conductive thin film.

[0014] Another object of the invention is a laminated glazing, in particular for windshields or roofs of motor vehicles, comprising a material as described above, bonded adhesively to an additional sheet of glass by means of a lamination interlayer, so that the sol-gel layer and the stack of thin layers are turned towards said interlayer.

[0015] The invention also relates to a method for obtaining such laminated glazing, comprising the following steps:

[0016] - the supply of a material obtained according to the process described above and an additional sheet of glass, then

[0017] - a bending step, including simultaneous bending of the material and the additional sheet of glass, then

[0018] - a step of laminating said material with the additional glass sheet by means of a laminating interlayer, so that the sol-gel layer and the stack of thin layers are turned towards said interlayer.

[0019] In the rest of the text, the sol-gel layer and the stack of thin layers are collectively referred to as "the coatings".

[0020] The glass sheet of the material according to the invention is preferably made of soda-lime silicate glass. It is advantageously obtained by flotation. Other glass compositions are, however, possible, for example, borosilicate or aluminosilicate compositions.

[0021] The glass sheet can be clear or tinted, preferably tinted, for example in green, gray, or blue. To achieve this, the chemical composition of the glass sheet advantageously includes iron oxide, in a weight content ranging from 0.5 to 2%. It may also include other coloring agents, such as cobalt oxide, chromium oxide, nickel oxide, erbium oxide, or selenium.

[0022] The glass sheet preferably has a thickness between 0.7 and 5 mm, especially between 1 and 4 mm, or even between 1.5 and 3 mm.

[0023] The lateral dimensions of the glass sheet must be adapted according to those of the laminated glass into which it is intended to be integrated. The glass sheet preferably has a surface area of ​​at least 1 m². 2 .

[0024] The dimensions of the glass sheet can depend on the stage of the process considered. According to one embodiment, the coating application stages are carried out on a "primer," that is, a glass sheet that already has the dimensions such that it will not need to undergo a cutting stage before bending and lamination. According to a second embodiment, the coating application stages are carried out on a large glass sheet (for example, with a surface area between 6 and 20 m²). 2 , specifically of approximately 3*6 m 2 or 3*3 m 2 Several laminated glass panes can then be made from the material obtained. In this case, a cutting step is carried out prior to bending and lamination. After cutting, the original sheet of glass is subdivided into n sheets of glass, n typically being from 2 to 5, notably 3 or 4.

[0025] The glass sheet can be flat or curved. It is generally flat during the stages of depositing the precursor sol for the sol-gel layer and stacking the thin layers. It is then preferably curved before the lamination stage, and therefore has a curved shape in the final glazing.

[0026] The first zone is the one coated with the sol-gel layer. This first zone preferably represents between 2 and 25%, specifically between 3 and 20%, or even between 5 and 15%, of the coated surface. In the final material, before or after integration into the laminated glass, this first zone preferably takes the form of a peripheral band. A "peripheral band" is defined as a closed band that extends inward from each point on the periphery of the glass sheet to a certain width, typically between 1 and 20 cm.

[0027] Here again, the shape of the first zone may depend on the stage of the process considered, insofar as cutting stages may take place after the coatings have been applied and before the curvature.

[0028] In the first embodiment described above (deposition on primitive), the first zone, during the deposition of the coatings, preferably takes the form of a peripheral band.

[0029] In the second embodiment described above (deposition on large sheet), the first zone, during the deposition of the coatings, preferably comprises several, in particular n closed, disjoint strips, n typically being from 2 to 5, in particular 3 or 4. After cutting, n materials are obtained, each having a first zone in the form of a peripheral strip, which can be curved and then integrated into the laminated glazing.

[0030] Preferably, the first and second zones together represent the entire surface of one face of the glass sheet. The first zone may constitute the entire surface without departing from the scope of the invention. In this case, the second zone no longer exists; the entire surface is coated with the sol-gel layer and then with the stack of thin layers.

[0031] The sol-gel layer is preferably in contact with the glass sheet.

[0032] The sol-gel layer is preferably opaque, tinted black. In particular, the lightness L* measured in reflection on the glass side (i.e., on the side opposite the mineral paint layer) is preferably less than 5, especially less than 3. The measurement is carried out using a spectrocolorimeter, and the calculation is performed taking into account the illuminant D65 and the CIE 1964 reference observer (10°).

[0033] The thickness of the sol-frost layer is at most equal to

[0034] 800, preferably 500 nm, and at least equal to 50, preferably 100 nm. This refers to the thickness of the final layer after firing. This layer has a perfectly smooth and regular surface. Its thinness is advantageous with regard to its covering by the stacking of thin layers (area of ​​the edges of said first zone), whose adhesion it promotes, and ultimately the cohesion of the whole.

[0035] The sol-gel layer refers to a layer obtained by a sol-gel process. It is oxide-based, and its precursor is chosen from the precursor sols of titanium oxides, silicon oxides, zirconium oxides, tin oxides, zinc oxides, aluminium oxides, indium oxides and oxides of transition metals, in particular copper, iron, cobalt, chromium, manganese.

[0036] The sol-gel layer can be transparent or opaque, and have a colored appearance due to the presence of pigments or metallic particles, for example.

[0037] The precursor soil includes salts of the element whose oxide is to be deposited. These include organometallic compounds, as well as nitrates, acetates, chlorides, etc. Examples of organometallic compounds include alkoxides, such as titanium tetraisopropoxide in the case of a titanium oxide layer or tetraorthosilicate (TEOS) in the case of a silicon oxide layer.

[0038] The soil may be partially aqueous. It preferably comprises an organic solvent, for example an alcohol, particularly ethanol, isopropanol, butanol, and glycols or glycol derivatives, and mixtures thereof. The soil may also contain viscosity-regulating agents, such as cellulose ethers or polyacrylates.

[0039] The sol-gel layer is preferably deposited by screen printing. The deposition of the precursor sol is then carried out by screen printing. Screen printing involves depositing a fluid composition onto the glass sheet, typically using a squeegee, through the mesh of a screen printing screen. The screen mesh is blocked in the areas of the glass sheet that are not to be coated, so that the fluid 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, are also possible.

[0040] The pre-baking stage can be preceded by a drying stage. However, this stage is not necessary, as the water contained in the sol-gel layer can evaporate during pre-baking.

[0041] After the precursor sol is deposited, the coated glass sheet undergoes a pre-curing step to harden the sol-gel layer, allowing the stack of thin layers to be deposited on top. Sol-gel layers can, for example, be hardened at moderate temperatures, in the range of 200 to 250°C.

[0042] However, it turned out that such temperatures did not always yield good results in terms of the aesthetics of the sol-gel layer and the electrical properties of the thin-film stack. It appears that with low-temperature curing, interactions between the two coatings can occur in some cases during curing. Conversely, pre-curing at at least 550°C, particularly 560°C, allows for the formation of a sol-gel layer that will not generate detrimental interactions during subsequent curing. Preferably, the sol-gel layer has therefore undergone a pre-curing step at a temperature of at least 550°C, particularly at least 580°C and even at least 600°C, before the thin-film stack is deposited. This pre-curing temperature is preferably no more than 650°C.This embodiment is particularly interesting when it is necessary to achieve high electrical conductivities including in the first zone, coated with the sol-gel layer.

[0043] Alternatively, when electrical conductivity is less critical—for example, when the electrically conductive thin film is used solely for its infrared radiation reflection properties and not as a heating layer—pre-curing can be carried out at lower temperatures, such as 200 to 450°C, or even 250 to 400°C. This facilitates subsequent cutting of the glass sheet. This is also the case when aesthetic considerations are less important, for example, when at least one glass sheet in the laminated glazing is heavily tinted, masking any potential discoloration resulting from interactions between the sol-gel layer and the stack of thin films.

[0044] The pre-baking stage is typically carried out in a radiant or convection oven. The pre-baking time is preferably between 60 and 1000 seconds, specifically between 100 and 600 seconds, or even between 120 and 500 seconds.

[0045] The stack of thin layers is preferably deposited, in the first zone, in contact with the sol-gel layer, and in the second zone, in contact with the glass sheet.

[0046] Preferably, the entire surface, or at least 90%, of the second zone is coated by stacking thin layers. Some areas may indeed remain uncoated to provide communication windows allowing the waves to pass through.

[0047] In the stacking of thin films, at least one, in particular the first or each, electrically conductive thin film is preferably a metallic film or a film of a transparent conductive oxide.

[0048] The metallic layer is preferably silver-based, specifically composed of silver. Other metals such as gold or niobium are also possible. The stack can consist of a single metallic layer, or several identical or different metallic layers, for example, two, three, or four silver-based layers.

[0049] The physical thickness of the metallic layer or, where applicable, the sum of the thicknesses of the metallic layers is preferably between 2 and 20 nm, in particular between 3 and 15 nm.

[0050] The layer of a transparent conductive oxide is preferably based on, in particular made up of, an oxide chosen from among mixed indium and tin oxides (ITO), tin oxides doped, in particular with fluorine or antimony, zinc oxides doped, in particular with aluminium or gallium.

[0051] The physical thickness of the layer of a transparent conductive oxide is preferably between 20 and 700 nm, especially between 30 and 500 nm.

[0052] To protect each electrically conductive thin film (whether metallic or based on a transparent conductive oxide) during the curving step, each of these layers is preferably sandwiched between at least two dielectric layers. The dielectric layers are preferably based on an oxide, nitride, and / or oxynitride of at least one element selected from silicon, aluminum, titanium, zinc, zirconium, and tin. The thin-film stacking includes, for example, a succession of dielectric and metallic layers, particularly silver-based layers.

[0053] The deposition of the thin-film stack is preferably performed by sputtering, particularly magnetically assisted sputtering (magnetron sputtering). In this technique, the glass sheet is passed over various targets in a vacuum chamber. Under the influence of a plasma, atoms are ejected from the target and deposited onto the glass sheet. This technique allows for the deposition of particularly complex stacks of layers, containing ten or more thin films.

[0054] The aforementioned stacks possess electrical conductivity and infrared reflection properties useful for providing a heating function (defrosting, demisting) and / or a thermal insulation function.

[0055] When the stack of thin films is intended to provide a heating function, current supply lines must be provided. These may consist of silver paste strips screen-printed onto the stack of thin films at two opposite edges of the glass sheet.

[0056] Laminated glazing is preferably curved. To achieve this, the two sheets of glass in the laminated glazing, i.e. the material according to the invention and the additional sheet of glass, are curved, generally together.

[0057] Bending can be achieved, for example, by gravity (the glass deforming under its own weight) or by pressing, at temperatures typically ranging from 550 to 650°C. To prevent the glass sheets from sticking together during bending, they are preferably kept apart by placing an interlayer powder between them, ensuring a gap of a few tens of micrometers, typically 20 to 50 µm. The interlayer powder is, for example, based on calcium carbonate and / or magnesium. During bending, the inner glass sheet (intended to be positioned inside the passenger compartment) is normally placed on top of the outer glass sheet.

[0058] In particular, in the case of the second embodiment described above (application of coatings to large sheets of glass), the bending step is preferably preceded by a cutting step. This step makes it possible to obtain sheets of glass with the appropriate dimensions for the production of laminated glazing.

[0059] The cutting step can be carried out at the edge of the first zone, coated with the sol-gel layer, or even within the first zone itself. The cutting step is preferably followed by a shaping step.

[0060] The lamination process can be carried out by autoclave treatment, for example at temperatures of 110 to 160°C and under a pressure of 10 to 15 bar. Prior to autoclave treatment, the air trapped between the glass sheets and the lamination interlayer can be removed by calendering or vacuum extraction.

[0061] The additional sheet is preferably the inner sheet of the laminated glass, that is, the sheet located on the concave side of the glass, intended to be positioned inside the vehicle's passenger compartment. In this way, the coatings are positioned on surface 2 of the laminated glass.

[0062] The additional glass sheet can be made of soda-lime glass, or borosilicate or aluminosilicate glass. It can be clear or tinted. Its thickness is preferably between 0.5 and 4 mm, particularly between 1 and 3 mm.

[0063] In a preferred embodiment, the additional glass layer is made of sodium aluminosilicate glass, preferably chemically strengthened, and has a thickness of between 0.5 and 1.2 mm. The additional glass layer is preferably the inner layer of the laminated glazing. The invention is particularly useful for this type of configuration, where it is difficult to arrange the stack of thin layers on face 3. The chemical strengthening (also called "ion exchange") consists of contacting the glass surface with a molten potassium salt (for example, potassium nitrate), so as to strengthen the glass surface by exchanging ions in the glass (here, sodium ions) for ions of a larger ionic radius (here, potassium ions). This ion exchange allows for the formation of compressive stresses on the glass surface and over a certain thickness.Preferably, the surface stress is at least 300 MPa, particularly 400 and even 500 MPa, and at most 700 MPa, and the thickness of the compression zone is at least 20 µm, typically between 20 and 50 µm. The stress profile can be determined using a polarizing microscope equipped with a Babinet compensator. The chemical quenching step is preferably carried out at a temperature ranging from 380 to 550°C, and for a duration ranging from 30 minutes to 3 hours. Chemical strengthening is preferably performed after the bending step but before the lamination step. The resulting glazing is preferably a motor vehicle windshield, in particular a heated windshield.According to another preferred embodiment, the additional glass sheet carries on the face opposite the face facing the lamination interlayer (preferably face 4, the additional sheet being the inner sheet) an additional stack of thin films, in particular a low-emissivity stack, comprising a transparent conductive oxide, in particular indium tin oxide. The invention is also particularly useful for this type of configuration, for which it is difficult to arrange stacks of thin films on both faces of the same glass sheet (faces 3 and 4). In this embodiment, the lamination interlayer and / or the additional glass sheet is tinted (e), the glass sheet bearing the sol-gel layer being able to be clear glass. The resulting glazing is preferably a motor vehicle roof.

[0064] The lamination interlayer preferably comprises at least one sheet of polyvinyl acetal, in particular polyvinyl butyral (PVB).

[0065] The lamination interlayer can be tinted or untinted in order to regulate the optical or thermal properties of the glazing if necessary.

[0066] The laminate interlayer can advantageously possess sound-absorbing properties to absorb airborne or structure-borne sounds. It can, in particular, be made up of three polymer sheets, including two outer sheets of PVB framing an inner polymer sheet, possibly also made of PVB, with a lower hardness than the outer sheets.

[0067] The lamination interlayer can also possess thermal insulation properties, particularly infrared radiation reflection. For this purpose, it can comprise a low-emissivity thin-film coating, for example, a coating including a thin layer of silver or a coating alternating dielectric layers with different refractive indices, deposited on an inner PET sheet sandwiched between two outer PVB sheets.

[0068] The thickness of the lamination interlayer is generally in the range of 0.3 to 1.5 mm, particularly 0.5 to 1 mm. The lamination interlayer may be thinner at one edge of the glazing than in the center of the glazing in order to avoid the formation of a double image when using a head-up display (HUD).

[0069] The following examples illustrate the invention in a non-limiting manner.

[0070] On 2.1 mm thick sheets of clear soda-lime glass, a black opaque layer (screen-printed, wet thickness: 20 to 25 µm) was successively deposited. Following a 3-minute pre-firing step, a stack of thin films comprising three silver thin layers surrounded by dielectric thin layers (deposited by magnetron sputtering) was then applied. After firing at various temperatures representative of those used for glass bending (between 575 and 645°C, for 6 minutes), the square resistance of the thin-film stack was measured. To closely approximate industrial conditions (simultaneous firing with glass bending), the firing was performed with a second 2.1 mm thick sheet of clear glass placed on top of the opaque black layer on the side of the glass sheets.

[0071] In a first comparative example A, the opaque black layer was an enamel layer obtained by depositing an enamel composition comprising pigments and a bismuth glass frit. The pre-firing temperature was 610°C.

[0072] In an example according to invention B, the layer was a screen-printable sol-gel coating made from a composition marketed by Vibrantz under the reference TLU0050 A. The proportions are given here as mass percentages. TLU0050 liquid solutions are precursors of titanium oxide-based reflective ceramic coatings intended to undergo heat treatment on their glass substrate.The titanium oxide precursor is titanium tetraisopropanolate (3 to 10%), mixed with organic compounds: hexa-2,4-dienoic acid (3 to 5%), rosin (2.5 to 10%), heavy aromatic naphtha solvent (petroleum) (1 to 10%), N-(2-ethylhexyl)-1-[[3-methyl-4-[(3-methylphenyl) azo]phenyl] azo]naphthalene-2-amine (0.1 to 1%) in an organic solvent (glycol ether / acetate, acid / ester / carbon dioxide, vegetable oil / terpene / balsam / wax / resin, salt of organic acids / bases, carbohydrate / cellulose (derivative)). The shear viscosity at 20 °C of the liquid precursor of the mineral coating is between 5 and 9 Pa·s. This 100% TiCt sol-gel layer could be opacified, tinted black by introducing pigments into the liquid precursor. The pre-curing temperature was 610°C. A silkscreen is used with a mesh of 90.40, i.e., 90 threads per cm for a wire diameter of 40 µm, or a 120.34 mesh, for example.The angle of the fabric relative to the frame is 22.5°.

[0073] In reference example C, no black layer was deposited. The stack of thin films was therefore deposited directly onto the glass.

[0074] Table 1 below summarizes the square resistances obtained (in Q) for each example, before firing and after firing at 575°C, 615°C and 645°C, in the first zone.

[0075] [Table 1] Comparison of examples A and C shows that the existence of an enamel layer in contact with the stack of thin layers is detrimental to the conductivity properties of the stack after firing, since the square resistance increases very strongly, and all the more so as the firing temperature is high.

[0076] In contrast, using a sol-gel layer (example B) maintains a good resistivity, at the same level as that obtained without a black layer (example C). The sol-gel layer is a frit-free material; its microstructure does not change after densification. It does not chemically interact with the stack of infrared-reflecting (IRR) magnetron-type thin films, unlike enamel, which contains bismuth oxide. The sol-gel layer is particularly thin (less than 500 nm thick) and has a smooth, uniform surface.

Claims

Demands 1. Material comprising a sheet of glass, one face of which comprises a first zone and a second zone, only the first zone being coated with a sol-gel layer, the sol-gel layer and the second zone of the sheet of glass being coated with a stack of thin layers comprising at least one electroconductive thin layer.

2. Material according to claim 1, wherein at least one electrically conductive thin layer is a metallic layer, in particular silver-based, or a layer of a transparent conductive oxide.

3. Material according to any one of the preceding claims, wherein the sol-gel layer is opaque, tinted black, the clarity L* measured in reflection on the glass side preferably being less than 5.

4. Material according to any one of the preceding claims, wherein the first zone represents between 2 and 25%, in particular between 3 and 20%, of the surface of the coated face.

5. Material according to any one of the preceding claims, such that the sol-gel layer has undergone a pre-baking step at a temperature of at least 550°C before the deposition of the thin-film stack.

6. Laminated glazing, in particular for windscreens or roofs of motor vehicles, comprising a material according to any one of the preceding claims, bonded adhesively to an additional sheet of glass by means of a lamination interlayer, such that the sol-gel layer and the stack of thin layers are turned towards said interlayer.

7. Laminated glazing according to the preceding claim, wherein the additional glass sheet is made of sodium aluminosilicate glass, preferably chemically strengthened, and has a thickness of between 0.5 and 1.2 mm.

8. Laminated glazing according to claim 6, wherein the additional glass sheet has on the face opposite the face turned towards the laminating interlayer, an additional stack of thin films, in particular a low-emissivity stack comprising a conductive transparent oxide.

9. A process for obtaining a material according to any one of claims 1 to 5, comprising the following steps: - the supply of a sheet of glass, one face of which comprises a first zone and a second zone, then - a deposition step on the first zone of a precursor soil of the soil-frost layer, then - a pre-baking stage at a temperature of at least 200°C, in order to obtain a sol-gel layer, then - a deposition step, on the sol-gel layer and on the second zone of the glass sheet, of a stack of thin films comprising at least one electrically conductive thin film.

10. A method according to the preceding claim, wherein the pre-cooking step is carried out at a temperature of at least 550°C.

11. A method according to any one of claims 9 or 10, wherein the step of depositing the precursor soil of the sol-gel layer is carried out by screen printing.

12. A method according to any one of claims 9 to 11, wherein the step of depositing the stack of thin films is carried out by sputtering.

13. A method for obtaining laminated glazing according to any one of claims 6 to 8, comprising the following steps: - the supply of a material obtained according to the process of any one of claims 9 to 12 and an additional sheet of glass, then - a bending step, including simultaneous bending of the material and the additional sheet of glass, then - a step of laminating said material with the additional glass sheet by means of a laminating interlayer, so that the sol-gel layer and the stack of thin layers are turned towards said interlayer.

14. A method according to the preceding claim, wherein the doming step is preceded by a material cutting step.

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