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

Abstract

The invention relates to a 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 glass sheet being coated with a stack of thin films comprising at least one electrically conductive thin layer. Another object of the invention is laminated glazing comprising such a material. No figure

Description

Title of the invention: Glass sheet coated with a sol-gel layer and a stack of thin films

[0001] The invention relates to the field of glazing, in particular automotive glazing, such as glazing for windshields or for the roof of motor vehicles.

[0002] Such glazing is often laminated glazing, in which two sheets of glass are bonded adhesively by means of a lamination interlayer. This interlayer helps, in particular, to retain glass fragments in the event of breakage, but also provides other functionalities, especially in terms of burglary resistance or improved acoustic properties.

[0003] These glazings often include coatings of various types, intended to confer different properties.

[0004] Layers of enamel, generally black and opaque, are often deposited on a portion of the glazing, usually in the form of a peripheral strip intended 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 generally located on face 2, the faces being traditionally numbered starting from the face intended to be positioned on the exterior of the vehicle. Face 2 is therefore a face in contact with the lamination interlayer. The aesthetic appearance of the enamel layer as seen from outside the vehicle is of particular importance to automotive manufacturers. The enamel is generally obtained by firing a composition comprising a glass frit and pigments at temperatures above 500°C. The firing step is generally carried out simultaneously with the curving of the glass sheet.

[0005] Coatings, generally in the form of stacks of thin films, 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. On the one hand, when current is supplied, these electrically conductive layers can dissipate heat by the Joule effect. These are then heating layers, useful, for example, for defrosting or demisting. On the other hand, these layers exhibit solar control or low-emissivity properties due to their reflection of infrared radiation. These layers are therefore valued for improving thermal comfort or for the energy savings they provide by reducing consumption for heating or air conditioning.These stacks of layers are generally arranged on face 3 of the laminated glazing, therefore also in contact with the lamination interlayer.

[0006] In certain cases, it may 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 in question, so that these coatings are protected within the laminated glazing. The enamel can be deposited on the thin-film stack, but any interactions that may occur between the two coatings during the enamel firing process can negatively affect the enamel's appearance. Another possibility is to deposit the thin-film stack directly onto the enamel. In this case, it is necessary to pre-fire the enamel and carefully control its roughness. However, the remelting of the enamel during the firing stage and the interactions that may then occur with the thin-film stack can degrade the enamel's appearance and / or the electrical conductivity of the stack.

[0007] The invention aims to overcome these drawbacks by proposing a solution that combines good aesthetics and good electroconductive properties.

[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: - 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 for the sol-gel layer, then - a pre-baking step at a temperature of at least 200°C, so as to obtain a sol-gel layer, then - a step of depositing, on the sol-gel layer and on the second zone of the glass sheet, a stack of thin films comprising at least one electrically conductive thin film.

[0010] Another object of the invention is a laminated glazing, in particular for windshield or roof of motor vehicle, 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.

[0011] The invention also relates to a method for obtaining such laminated glazing, comprising the following steps: - the supply of a material obtained according to the process described above 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.

[0012] In the remainder of the text, the sol-gel layer and the stack of thin layers are collectively referred to as "the coatings".

[0013] 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 type compositions.

[0014] The glass sheet may be clear or tinted, preferably tinted, for example 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.

[0015] The glass sheet preferably has a thickness of between 0.7 and 5 mm, in particular between 1 and 4 mm, or even between 1.5 and 3 mm.

[0016] The lateral dimensions of the glass sheet must be adapted according to those of the laminated glazing into which it is intended to be integrated. The glass sheet preferably has a surface area of ​​at least 1 m².

[0017] The dimensions of the glass sheet can depend on the process step considered. According to a first embodiment, the coating application steps are carried out on a "primitive," that is, a glass sheet that already has dimensions such that it will not need to undergo a cutting step before bending and lamination. According to a second embodiment, the coating application steps are carried out on a large glass sheet (for example, with a surface area between 6 and 20 m², in particular approximately 3 x 6 m² or 3 x 3 m²). Several laminated glass panes can then be produced from the resulting material. In this case, a cutting step is carried out prior to bending and lamination. After cutting, the original glass sheet is subdivided into n glass sheets, n typically being from 2 to 5, in particular 3 or 4.

[0018] The glass sheet can be flat or curved. It is generally flat during the steps of depositing the precursor sol of the sol-gel layer and stacking the thin layers. It is then preferably curved before the lamination step, and therefore has a curved shape in the final glazing.

[0019] The first zone is that coated by the sol-gel layer. This first zone preferably represents between 2 and 25%, in particular between 3 and 20%, or even between 5 and 15%, of the coated face surface. In the final material, before integration or integrated into the laminated glazing, the first zone preferably takes the form of a peripheral band. By "peripheral band," we mean a closed band which, from each point on the periphery of the glass sheet, extends inwards towards the interior of the glass sheet over a certain width, typically between 1 and 20 cm.

[0020] 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 deposited and before the curvature.

[0021] 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.

[0022] 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.

[0023] 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 films.

[0024] The sol-gel layer is preferably in contact with the glass sheet.

[0025] The sol-gel layer is preferably opaque, tinted black. In particular, the clarity L* measured in reflection on the glass side (i.e. on the side opposite the mineral paint layer) is preferably less than 5, in particular less than 3. The measurement is carried out using a spectrocolorimeter, and the calculation is carried out taking into consideration the illuminant D65 and the reference observer CIE 1964 (10°).

[0026] The thickness of the sol-gel layer is at most 800, preferably 500 nm, and at least 50, preferably 100 nm. This refers to the thickness of the final layer after baking. This layer has a perfectly smooth and regular surface. Its thinness is advantageous with regard to its coverage by the stacking of thin layers (the edge zone of said first zone), whose adhesion it promotes, and ultimately the cohesion of the whole.

[0027] The sol-gel layer refers to a layer obtained by a sol-gel process. It is oxide-based, and its precursor is chosen from among 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.

[0028] The sol-gel layer can be transparent or opaque, have a colored appearance due to the presence of pigments or metallic particles, for example.

[0029] The precursor sol includes, in particular, salts of the element whose oxide is to be deposited. These include, in particular, organometallic compounds or nitrates, acetates, chlorides, etc. Examples of organometallic compounds include alkoxides, for example, titanium tetraisopropoxide in the case of a titanium oxide layer or tetraorthosilicate (TEOS) in the case of a silicon oxide layer.

[0030] The soil may be partially aqueous. It preferably comprises an organic solvent, for example an alcohol, in particular selected from ethanol, isopropanol, butanol, and glycols or glycol derivatives, and mixtures thereof. The soil may further contain viscosity-regulating agents, such as cellulose ethers or polyacrylates.

[0031] The sol-gel layer is preferably deposited by screen printing. The deposition step of the precursor sol is then carried out by screen printing. Screen printing comprises the deposition, notably using a squeegee, of a fluid composition onto the glass sheet through the mesh of a screen printing screen. The screen mesh is blocked in the portion corresponding to 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 techniques, are also possible.

[0032] The pre-baking step may be preceded by a drying step. However, this step is not necessary, as the water contained in the sol-gel layer can evaporate during pre-baking.

[0033] After the precursor sol is deposited, the coated glass sheet undergoes a pre-baking step, designed to harden the sol-gel layer, so that the stack of thin layers can be deposited on it. The sol-gel layers can, for example, be hardened at moderate temperatures, on the order of 200 to 250°C.

[0034] However, it has been found that such temperatures do 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, in the case of low-temperature curing, interactions between the two coatings can occur in some cases during bending. On the other hand, pre-curing at at least 550°C, particularly 560°C, makes it possible to form a sol-gel layer that will not generate detrimental interactions during subsequent bending. Preferably, the The sol-gel layer therefore underwent a pre-baking step at a temperature of at least 550°C, specifically at least 580°C and even at least 600°C, before the thin-film stack was deposited. This pre-baking temperature is preferably no more than 650°C. This embodiment is particularly advantageous when it is necessary to achieve high electrical conductivities, including in the first zone coated with the sol-gel layer.

[0035] 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, in particular from 200 to 450°C, or even from 250°C to 400°C, which notably 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 of the laminated glazing is highly tinted, masking any potential discoloration resulting from interactions between the sol-gel layer and the stack of thin films.

[0036] The pre-baking step is typically carried out in a radiant or convective oven. The pre-baking time is preferably between 60 and 1000 seconds, in particular between 100 and 600 seconds, or even between 120 and 500 seconds.

[0037] The stack of thin films 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.

[0038] Preferably, the entire surface, or at least 90%, of the second zone is coated by stacking thin layers. Some areas may indeed remain uncoated in order to provide communication windows allowing the waves to pass through.

[0039] In the stack of thin films, at least one, in particular the or each, electrically conductive thin film is preferably a metallic film or a film of a transparent conductive oxide.

[0040] The metallic layer is preferably silver-based, in particular composed of silver. Other metals such as gold or niobium are also possible. The stack may comprise a single metallic layer, or several identical or different metallic layers, for example two, three or four silver-based layers.

[0041] 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.

[0042] 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.

[0043] The physical thickness of the layer of a transparent conductive oxide is preferably between 20 and 700 nm, in particular between 30 and 500 nm.

[0044] In order to protect the or each electroconductive thin film (whether metallic or based on a transparent conductive oxide) during the bending step, each of these layers is preferably sandwiched between at least two dielectric layers. The dielectric layers are preferably based on an oxide, nitride, and / or oxynitride of at least one element selected from silicon, aluminum, titanium, zinc, zirconium, and tin. The stack of thin films comprises, for example, a succession of dielectric layers and metallic layers, particularly silver-based layers.

[0045] The thin-film stack deposition step is preferably carried out by sputtering, particularly magnetically assisted sputtering (magnetron process). In this technique, the glass sheet is passed, within a vacuum chamber, over various targets. Under the effect of a plasma, atoms are ejected from the target and deposited onto the glass sheet. This technique makes it possible to deposit particularly complex stacks of layers, containing ten or more thin films.

[0046] The aforementioned stacks possess electrical conduction and infrared reflection properties useful for providing a heating function (defrosting, demisting) and / or a thermal insulation function.

[0047] When the stack of thin films is intended to provide a heating function, current supply points must be provided. These may, in particular, consist of silver paste strips screen-printed onto the stack of thin films at two opposite edges of the glass sheet.

[0048] Laminated glazing is preferably curved. To achieve this, the two sheets of glass of the laminated glazing, i.e. the material according to the invention and the additional sheet of glass, are curved, generally together.

[0049] The 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 the bending process, 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 carbonate. During the bending process, the inner glass sheet (intended to be positioned inside the passenger compartment) is normally placed on top of the outer glass sheet.

[0050] In particular, in the case of the second embodiment described above (deposition of coatings on large sheets of glass), the curvature step is This method is preferably preceded by a cutting stage. This stage allows for the production of glass sheets with the appropriate dimensions for the creation of laminated glazing.

[0051] 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. The cutting step is preferably followed by a shaping step.

[0052] The lamination step 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 by vacuum.

[0053] 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 vehicle's passenger compartment. In this way, the coatings are arranged on face 2 of the laminated glazing.

[0054] The additional glass sheet may be made of soda-lime silicate glass, or of borosilicate or aluminosilicate glass. It may be clear or tinted glass. Its thickness is preferably between 0.5 and 4 mm, in particular between 1 and 3 mm.

[0055] According to a preferred embodiment, 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. 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 arrange the stack of thin layers on face 3. The chemical strengthening (also called "ion exchange") consists of contacting the surface of the glass with a molten potassium salt (for example, potassium nitrate), so as to strengthen the surface of the glass by exchanging ions in the glass (here, sodium ions) for ions of a larger ionic radius (here, potassium ions). This ion exchange makes it possible to create 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 compression zone is at least 20 pm, typically between 20 and 50 pm. The stress profile can be determined in a known manner 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. The chemical strengthening is preferably carried out 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 is borne 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, the glass sheet bearing the sol-gel layer being able to be clear glass. The resulting glazing is preferably a motor vehicle roof.

[0056] The lamination interlayer preferably comprises at least one sheet of polyvinyl acetal, in particular polyvinyl butyral (PVB).

[0057] The lamination interlayer can be tinted or untinted in order to regulate the optical or thermal properties of the glazing if necessary.

[0058] The lamination interlayer may advantageously possess sound-absorbing properties in order to absorb airborne or structure-borne sound. In particular, it may 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.

[0059] The lamination interlayer may also possess thermal insulation properties, in particular infrared radiation reflection. For this purpose, it may comprise a low-emissivity thin-film coating, for example, a coating comprising a thin silver layer or a coating alternating dielectric layers with different refractive indices, deposited on an inner PET sheet framed by two outer PVB sheets.

[0060] The thickness of the lamination interlayer is generally in the range of 0.3 to 1.5 mm, in particular 0.5 to 1 mm. The lamination interlayer may have a lower thickness at an edge of the glazing than at the center of the glazing in order to avoid the formation of a double image when using a head-up display (HUD) system.

[0061] The following examples illustrate the invention in a non-limiting manner.

[0062] On 2.1 mm thick sheets of clear soda-lime-silicon glass, a black opaque layer (screen-printed, wet thickness: 20 to 25 µm) was successively deposited, followed, after a 3-minute pre-firing step, by a stack of thin films comprising three thin silver layers surrounded by dielectric thin films (deposited by magnetron sputtering). 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. In order to be as close as possible to industrial conditions (simultaneous firing with glass bending), the firing was carried out by placing a second sheet of clear glass, 2.1 mm thick, on the side of the opaque black layer of the glass sheets.

[0063] 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.

[0064] 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 be subjected to 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)-l-[[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 for the mineral coating is between 5 and 9 Pa·s. This 100% TiO2 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 90.40 mesh (90 threads per cm² for a 40 µm wire diameter) or a 120.34 mesh, for example. The mesh angle relative to the frame is 22.5°.

[0065] In reference example C, no black layer was deposited. The stack of thin films was therefore deposited directly onto the glass.

[0066] 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.

[0067] [Tables 1] - 575°C 615°C 645°CA 1.7 3.1 3.6 9 B 1.5 1.0 1.1 1.1 C 1.4 1.0 1.0 1.0

[0068] 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.

[0069] In contrast, the use of a sol-gel layer (example B) allows for maintaining a desirable 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-reflective (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 having one face comprising a first zone and a second zone, the first zone only 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 films comprising at least one electroconductive thin film.

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 prior to 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 method 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 step of depositing on the first zone a sol precursor of a sol-gel layer, then - a pre-baking step at a temperature of at least 200°C, so as to obtain a sol-gel layer, then - a step of depositing, on the sol-gel layer and on the second zone of the sheet of glass, a stack of thin layers comprising at least one electrically conductive thin layer.

10. A method according to the preceding claim, wherein the pre-baking 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 thin film stack 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: - supplying a material obtained according to the method of any one of claims 9 to 12 and an additional sheet of glass, then - a step of curving, in particular simultaneously, the material and the additional sheet of glass, then - a step of laminating said material with the additional sheet of glass by means of a laminating interlayer, so that the sol-gel layer and the stack of thin films are turned towards said interlayer.

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