Manufacturing process for solar control and / or low-emissivity glazing, transparent to radio frequencies: cracked sol-gel overcoat

Abstract

The present invention relates to a method for manufacturing a glass article comprising the following steps: - the provision of a glass substrate, - the deposition, on at least one face of said glass substrate, of a stack of layers comprising at least one functional metallic layer containing silver, each of said layers being deposited by magnetic field assisted sputtering, - the application of a sol-gel solution comprising at least one silicon oxide precursor and / or at least one transition metal oxide precursor, said solution being applied over said stack of layers, so as to form a sol-gel layer having an average thickness of between 50 nm and 3000 nm, preferably between 70 nm and 1500 nm, - the heat treatment at a temperature above 500°C, preferably between 540°C and 700°C, so as to crack the sol-gel layer and damage the stack of layers.The present invention also relates to a glass article that can be obtained by such a process which comprises a glass substrate coated on at least one of its faces: - with a stack of layers comprising at least one functional metallic layer containing silver, and - with at least one sol-gel layer located above said stack of layers and having an average thickness between 50 nm and 3000 nm, preferably between 70 nm and 1500 nm, said stack of layers and said sol-gel layer having cracks or fissures.

Description

Title of the invention: Method for manufacturing solar control and / or low-emissivity glazing, transparent to radio frequencies: cracked sol-gel overcoat

[0001] The invention relates to a method for manufacturing a glass article transparent to radio frequencies, the glass article being in particular a solar control and / or low-emissivity glazing whose glass substrate is provided with a stack of thin films comprising at least one functional metallic layer containing silver. The invention thus relates to the glass article obtained by said method and more particularly to windshields, side windows, or roof windows of motor vehicles, or building glazing, or train glazing comprising such glass articles.

[0002] For the purposes of this application, the term “functional layer” means the layer (or layers) of the stack that gives the stack the essential thermal and / or solar protection properties.

[0003] In order to reduce greenhouse gas emissions, it is common practice to use so-called "solar control" glazing in buildings, motor vehicles, and trains. "Solar control" glazing is glazing that limits the flow of energy, particularly solar infrared (SIR) radiation, passing through it from the outside to the inside without affecting light transmission in the visible spectrum. To measure the energy insulation properties of glazing, the total transmitted solar energy, denoted "TTS" (in English, "total transmitted solar energy"), is used in this field.

[0004] which corresponds to the ratio of the energy passing through the glazing (i.e., entering the room) to the incident solar energy. More specifically, it corresponds to the sum of the flux transmitted directly through the glazing and the flux absorbed by the glazing (including any stacks of layers present on one of its surfaces) and then re-emitted inwards (towards the room) by the glazing. Thus, the lower the TTS value, the better the protection against solar radiation.

[0005] Furthermore, in order to limit energy losses, it is common practice to use so-called "low-emissivity" (or "low-e" in English) insulating glazing which essentially works by reflecting a major part of the incident infrared radiation.

[0006] In particular, with the rise of connected vehicles and the Internet of Things, motor vehicles are now equipped with embedded telecommunication systems (Wi-Fi or Bluetooth transmitters, GPS chips, etc.) enabling Wireless communications with the external environment. These systems can also interact with personal telecommunication devices (cell phone, etc.) of the driver and / or passengers.

[0007] Thus, in addition to solar control and / or low-emissivity properties, it is necessary that glazing for motor vehicles, but also glazing for buildings or for trains, exhibit transparency properties to radio electromagnetic waves, in particular radio frequencies, which are commonly used in on-board telecommunication devices.

[0008] However, solar control glazing that also offers good optical performance (light transmission, blur, color, etc.) and low-emissivity glazing with good thermal performance, and in particular glazing with a stack of thin films including at least one metallic functional layer containing silver, is generally not suitable for such applications. Indeed, the metallic functional layers containing silver present in these types of glazing (solar control and / or low-emissivity) are continuous and conductive layers that block radio electromagnetic waves, especially radio frequency waves. The radio signal emitted or detected by these telecommunications devices is then weakened, and the quality of communications becomes poor. Telecommunications may sometimes be impossible.

[0009] By way of example, according to the article by Rodriguez et al., "Radio Propagation into Modem Buildings: Attenuation Measurements in the Range from 800 MHz to 18 GHz", 2014 IEEE 80th Vehicular Technology Conference (VTC2014-Fall), 2014, pp. 1-5, glazing which includes a stack of layers comprising metallic functional layers can cause an attenuation of more than 30dB (decibel) of telecommunication signals.

[0010] To make the solar control and / or low-emissivity glazing mentioned above transparent to radiofrequency waves, it is known to use mass-tinted glass. However, its solar control performance is significantly reduced.

[0011] Another possibility is the use of a 3M film. However, this film can crease during lamination, which therefore makes its use on an industrial scale complicated.

[0012] Another known method consists of etching the silver layer, after its deposition onto a glass substrate coated with thin films, so as to selectively remove the silver in bands or lines having a width of at least 50 µm. This etching is performed by a spot etching laser, also called the "laser ablation method." This technique has the disadvantages of being very expensive and unsightly, since the bands or lines that make the glass transparent to radio frequencies are then visible to the naked eye on the glass substrate. In addition, laser ablation has low productivity on large-format glazing requires a significant investment relative to the surfaces involved.

[0013] There is therefore a need to find another method for making transparent to radio electromagnetic waves a glass substrate coated with a stack of thin films comprising at least one functional metallic layer containing silver which is less expensive and more reproducible, while retaining good solar control properties, good optical and thermal properties for the glass article obtained; the glass article obtained according to the invention also being more aesthetic than the glass article obtained according to the prior art.

[0014] In the present application, the term "radio-transparent electromagnetic wave glass article or radio-frequency wave transparent article, denoted "RF", means a glass article having a transparency to RF waves similar to that of bare glass, in other words, preferably exhibiting a transmission loss in decibels (dB) between 0 and -5 dB for a frequency ranging from 4 to 14 GHz.

[0015] Furthermore, a glass article transparent to RF waves according to the invention preferably has a profile such that the resistance-per-square parameter, named "Rsq" ("resistivity square" in English), is between 500 Ohms per square (Q / D) and infinity, and in particular greater than 1500 Q / D

[0016] To this end, the invention relates to a method for manufacturing a glass article comprising the following steps: - the supply of a glass substrate, - the deposition, on at least one face of said glass substrate, of a stack of layers comprising at least one functional metallic layer containing silver, each of said layers being deposited by magnetic field-assisted sputtering, - the application of a sol-gel solution comprising at least one silicon oxide precursor and / or at least one transition metal precursor, said solution being applied over said stack of layers, so as to form a sol-gel layer having an average thickness of between 50 nm and 3000 nm, preferably between 70 nm and 1500 nm, - heat treatment at a temperature above 500°C, preferably between 540°C and 700°C, so as to crack the sol-gel layer and damage the stack of layers.

[0017] Indeed, it was surprisingly observed by the inventors that the addition of at least one sol-gel layer by liquid method, on top of a stack of layers deposited by magnetron on a glass substrate and comprising at least one functional metallic layer containing silver, made it possible, after heat treatment of the whole, to render the glass article transparent to electromagnetic waves radio while having little effect on the solar control, optical and thermal properties of the glass article.

[0018] The inventors thus discovered that during the heat treatment of the glass article, the sol-gel layer deposited by liquid over the stack of layers comprising at least one functional metallic layer containing silver cracked, damaging and / or fracturing the layers of said stack: - either by propagation of the cracks / fissures on the layers of the stack and in particular on the layer(s) containing silver, or - either by localized oxidation of the functional metallic layer(s) containing silver, thus advantageously creating cracks or fissures of small width between 0.5 pm and 5 pm, referred to in this application as "crack or fissure width".

[0019] Said cracks / fissures in particular on the layer(s) containing silver have thus made it possible to make these layers non-conductive in certain places, thus allowing the obtaining of a glass article transparent to radio electromagnetic waves.

[0020] Thus, the process according to the invention is rapid and its implementation is simple; the heat treatment allows both the sol-gel layer to be cracked and the glass article to be given certain properties or conformations (tempered and / or domed and / or annealed substrate).

[0021] For the purposes of this application, "cracked sol-gel layer" means a sol-gel layer exhibiting cracks or fissures, advantageously of small width between 0.5 pm and 5 pm.

[0022] A glass article obtained according to the invention can thus be used as laminated or laminated glazing, multiple, double or triple, without problems of wrinkling or lack of adhesion between the layers during lamination or lamination.

[0023] The glass substrate according to the invention is in particular made of soda-lime silico-glass, but it may also be of the borosilicate or aluminosilicate type. Clear soda-lime silico-glasses are preferred. The thickness of the glass substrate can vary between 0.1 mm and 20 mm, in particular between 2 and 8 mm. The glass substrate is preferably in the form of a glass sheet.

[0024] The glass substrate may be partially or totally coated with an enamel layer. The term "coated" means that the enamel layer coating the substrate is deposited on top of said substrate, but not necessarily in contact with it. Preferably, the enamel layer is in direct contact with the glass substrate. Even more preferably, the enamel layer is in direct contact with the glass substrate and / or the stack of layers. The enamel layer or the enamel consists of a mixture of glass frit (i.e., glassy phase), pigments The enamel consists of inorganic and organic components, a mixture of diluent (organic solvent) and an organic medium (most often resin dissolved in a solvent), ensuring proper suspension of all the inorganic particles and thus allowing their application in a liquid state. The enamel layer can be applied by screen printing or using the curtain technique. Once applied, the enamel layer can optionally be dried at a temperature below 150°C before being fired at a higher temperature.

[0025] The layer stack according to the invention comprises at least one functional metallic layer containing silver. The layer stack may successively comprise, starting from the glass substrate, an alternation of x functional metallic layers containing silver and (x+1) antireflective coatings, each antireflective coating comprising at least one dielectric layer, such that each functional metallic layer containing silver is disposed between two antireflective coatings.

[0026] Very advantageously, the layer stack comprises a single functional metallic layer containing silver, x is equal to 1; in other words, the thin film stack comprises, more preferably, successively from the glass substrate a single functional layer containing silver and two anti-reflective coatings, each anti-reflective coating comprising at least one dielectric layer, so that the single functional metallic layer is disposed between two anti-reflective coatings.

[0027] The thickness of the thin film stack can be greater than 70 nm, and less than 400 nm.

[0028] Each of the stack layers is deposited by magnetic field-assisted sputtering over the glass substrate.

[0029] A sol-gel solution is then applied over the stack of layers, as defined above, so as to form a sol-gel layer. The sol-gel solution preferably contains a dry extract of at most 50% by weight, in particular of at most 10% by weight, and generally between 8% and 15% by weight, and even more generally of at least 1% by weight.

[0030] The solvent for the solution is preferably chosen from water, organic solvents, and mixtures of water and organic solvents. Organic solvents are preferably chosen from alcohols (for example, isopropanol, propanol, ethanol, etc.) and acetone. The term "solvent" is used here in its generic sense, so the solvent may consist of a mixture of solvents.

[0031] In a first embodiment, the sol-gel solution can be aqueous, in the sense that the solvent of the solution contains at least 50% by weight of water, or even 60%, and even 70%, 80%, or 90% by weight of water. The solvent is preferably completely aqueous, in the sense that it is made up of water. The use of aqueous solutions, or at least predominantly aqueous solutions, offers advantages in terms of the environment, industrial hygiene, cost, and also the durability of the resulting layer.

[0032] In a second embodiment, the sol-gel solution can be alcoholic, it contains at least 50% by weight of an alcohol, or even 60%, and even 70% or 80% or even 90% by weight of an alcohol; the alcohol being chosen for example from isopropanol, propanol and ethanol.

[0033] According to the invention, the sol-gel solution comprises at least one silicon oxide precursor and / or at least one transition metal oxide precursor. Indeed, the sol-gel layer according to the invention, also referred to as the "sol," is obtained in a known manner by hydrolysis and polycondensation of the oxide precursors. The transition metal is preferably selected from Ti, Al, Zr, Ce, and Zn. The silicon oxide precursor is preferably an inorganic silicon salt or a silicon alkoxide, and in particular an alkoxysilane. Similarly, the transition metal precursor is preferably an inorganic transition metal salt or a transition metal alkoxide; the transition metal being advantageously selected from Ti, Al, Zr, Ce, and Zn.

[0034] Thus, the silicon oxide precursor can be: • an inorganic silicon salt of general formula (I) as follows: SiXy, in which X is a halogen, preferably a chlorine, and y is an integer equal to 4, such as silicon tetrachloride of formula SiCl4, or • a silicon alkoxide chosen from: - alkoxysilanes of general formula (II) as follows: Si(OR')z, in which R1 is independently chosen from the Ci-C4 alkyls, and z is an integer equal to 4, - alkoxysilanes of general formula (III) as follows: Si(OR1)4 kR2k, in which R1 is independently chosen from among the Ci-C4 alkyls, k is an integer between 1 and 3, and R2 is independently an alkyl group substituted with or without a reactive function, and - a mixture of these alkoxysilanes.

[0035] The term “reactive function” means a function selected from the group consisting of epoxy, carboxylic acid, amine, acrylate, methacrylate, vinyl, isocyanate, thiol, thiocyanate and hydroxyl.

[0036] The preferred alkoxysilanes according to the general formula (II) are the following: tetraethyl orthosilicate and tetramethyl orthosilicate, and the alkoxysilanes Preferred according to the general formula (III) are the following: tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, methyltriethoxysilane, rethyltriethoxysilane, propyltriethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, (3-glycidyloxypropyl)trimethoxysilane, and methacryloxypropyltrimethoxysilane.

[0037] Thus, the precursor of transition metal oxide is preferably: - an inorganic salt of general formula (IV) as follows: MXy,

[0038] in which M is chosen from Ti, Al, Zr, Ce and Zn, X is a group chosen from chlorides, nitrates, acetates, and y is an integer between 2 and 4, such as titanium tetrachloride, aluminum chloride, cerium chloride, aluminum nitrate, cerium nitrate or zinc acetate, or - a transition metal alkoxide of general formula (V) as follows: M(OR)Z, in which M is chosen from Ti, Al, Zr, Ce and Zn, R is independently chosen from the alkyls in Ci-C4z is an integer between 2 and 4.

[0039] The preferred transition metal alkoxides according to the general formula (V) are the following: tetrabutyl orthotitanate, tetraethyl orthotitanate, tetramethyl orthotitanate, tetrapropyl orthotitanate, titanium isopropoxide, aluminum isopropoxide, aluminum tri-sec butoxide, zirconium isopropoxide, and zirconium propoxide.

[0040] The sol-gel solution may include other components, such as complexing agents, porogens, pH regulating agents, surfactants, nanoparticles, nanopigments,...

[0041] A pore-forming agent, according to the invention, may be solid, its size being chosen to allow for variation in pore size. The pore-forming agent may be particulate, particularly of a substantially spherical shape, for example in the form of hollow or solid beads. The pore-forming agent is preferably organic in nature. By way of example, the pore-forming agent comprises polymeric beads, in particular of a polymer selected from polymethyl methacrylate (PMMA), methyl (meth)acrylate / (meth)acrylic acid copolymers, polycarbonates, polyesters, and polystyrene.

[0042] The sol-gel solution to be applied is preferably acidic. Its pH is preferably between 0 and 5, in particular between 1 and 3.

[0043] The application of the sol-gel solution is preferably carried out by coating using at least one roller, a technique also known as "roll coating," which allows precise control of the amount of solution deposited as well as the spatial homogeneity of the deposit. According to this technique, the glass substrate covered with a stack of layers is preferably passed under a metering roller and a roller The applicator rollers are in near contact with each other and rotate in the same or opposite direction. The applicator roller is in contact with the surface of the substrate to be coated, and the solution to be applied is poured from above between these two rollers. The solution, passing between the metering roller and the applicator roller, is deposited on the surface of the latter and then transferred to the surface to be coated.

[0044] The gel solution can also be deposited by curtain coating, slit coating, dip coating, blade coating, spraying, or inkjet printing.

[0045] In another embodiment, no layer comprising an organic polymer is deposited above the sol-gel layer before the heat treatment step. For the purposes of this application, "organic polymer" means a macromolecule consisting of repeating basic molecular units (motifs or repeating units) linked to each other by covalent bonds.

[0046] Thus, the sol-gel solution application step is followed by a heat treatment step of the coated glass substrate (by at least one stack of layers and at least one sol-gel layer) which is carried out at a temperature above 500°C, preferably between 540°C and 700°C. The heat treatment is preferably a tempering, bending, or annealing treatment of the glass, and more preferably a tempering treatment. Tempering the glass consists of heating the glass to a temperature generally above 500°C and then rapidly cooling it, generally by means of nozzles emitting cold air. This rapid cooling creates compressive stresses on the surface of the glass substrate, and thus increases its mechanical strength and impact resistance.

[0047] The heat treatment in the process as defined in this application primarily initiates the cracking of the sol-gel layer and damages the stacked layers, particularly the silver-containing layer(s), by propagating cracks / fissures, thus rendering the glass article transparent to radio electromagnetic waves. It should be noted that the cracks or fissures present on the sol-gel layer and the stacked layers are advantageously barely visible to the naked eye, as their width can range from 0.5 µm to 5 µm.

[0048] Immediately after the application step of the sol-gel solution, before the heat treatment step, the process according to the invention may further include a drying step. This step is intended to accelerate the evaporation of the solvent contained in the sol-gel solution and to consolidate the solution so as to form a dried sol-gel layer with an average thickness of between 50 nm and 3000 nm, preferably between 70 nm and 1500 nm. Indeed, the purpose of this step is to obtain a sol-gel layer that is solid to the touch, in other words, one that is no longer liquid in order to avoid absorbing dust. It can be implemented by all known means, for example by blowing hot air, by IR radiation or by vacuum drying.

[0049] By "average thickness of the sol-gel layer", for the purposes of the present invention, means the average geometric thickness of the layer, as it can be measured in particular by classical scanning electron microscopy or other techniques, such as ellipsometry.

[0050] According to another preferred embodiment, the manufacturing process for the glass article may further comprise, after the heat treatment step, the following successive steps: - the deposition of a sheet, or an interlayer film, of a material selected from poly(vinyl butyral) (PVB), poly(ethylene-vinyl acetate) (EVA) and polyurethane (PU) and mixtures thereof, - the provision of a second glass substrate, and - assembly of the whole (i.e. the first glass substrate bearing the damaged layer stack and the cracked sol-gel layer / interlayer film and the second glass substrate) by lamination to form a laminated glazing.

[0051] An object of the invention is therefore also a glass article, in particular capable of being obtained by the process according to the invention, which comprises a glass substrate coated on at least one of its faces: - a stack of layers comprising at least one functional metallic layer containing silver, and - of at least one sol-gel layer located above said stack of layers and having an average thickness between 50 nm and 3000 nm, preferably between 70 nm and 1500 nm, said stacking of layers and said sol-gel layer exhibiting cracks or fissures.

[0052] The layer stack comprising at least one functional metallic layer containing silver, as described above, exhibits cracks or fissures, preferably with a width between 0.5 µm and 5 µm. The layer stack preferably comprises a single functional metallic layer containing silver.

[0053] The sol-gel layer can be in direct contact with the stack of layers which includes at least one functional metallic layer containing silver.

[0054] The cracked sol-gel layer may have a refractive index between 1.3 and 2.3, preferably between 1.4 and 1.8, and more preferably between 1.4 and 1.6, measured at a wavelength of 630 nm.

[0055] In addition, the inventors noted that by varying the nature of the precursors of the sol-gel layer, the thickness of the sol-gel layer had to be adapted in order to be able to crack it during the heat treatment.

[0056] Thus, in a preferred embodiment, the sol-gel layer comprising silicon dioxide has an average thickness of between 300 nm and 3000 nm.

[0057] In another preferred embodiment, the sol-gel layer comprises titanium dioxide or zirconium dioxide and has an average thickness of between 70 nm and 1000 nm.

[0058] In a preferred embodiment, the stack of layers is in direct contact with the glass substrate.

[0059] In another possible embodiment, the cracked sol-gel layer of the glass article is not coated with a layer comprising an organic polymer before the first heat treatment step.

[0060] In another preferred embodiment, the glass article may further comprise an enamel layer, as described above, being disposed between the glass substrate and the stack of layers. More preferably, the enamel layer is in direct contact with the glass substrate and / or the stack of layers.

[0061] As stated previously, the inventors discovered that the heat treatment of at least one sol-gel layer, as described above and disposed above a stack of layers deposited by magnetron on a glass substrate and comprising at least one functional metallic layer containing silver, made it possible to render the glass article transparent to radio electromagnetic waves while having little effect on the solar control, optical and thermal properties of the glass article.

[0062] Thus, the Applicant proposes a glass article preferably having: - a measure of transparency to radio frequency waves, denoted "RF", ranging from 0 to -5 dB, preferably from 0 to -2 dB for a frequency ranging from 4 to 14 GHz; - a resistance "Rsq" ranging from 500 ohms per square (Q / D) to infinity, and in particular greater than 1500 Q / D; - a light transmission "TL" greater than 30% in particular for motor vehicle roof windows and greater than 70% in particular for windscreens, in the range of wavelengths of the visible spectrum; - narrow cracks or fissures between 0.5 pm and 5 pm, - a total solar transmitted energy (TTS) value of less than 60%, preferably less than 55%; and - a normal emissivity "en" in particular for non-laminated (or non-laminated) glazing of less than 2.5; emissivity being defined by the relation: en = 1 - Rn, in which Rn is the reflection factor according to the normal (according to Annex A of the international standard ISO 10292 (1994) and according to the standard NF EN 12898 (2019)) of the glazing.

[0063] In general, all the luminous characteristics presented in this description, in particular the light transmission “TL” and the total solar energy transmitted “TTS”, are obtained according to the principles and methods described in the standard NF EN 410 (2011) relating to the determination of the luminous and energy characteristics in the visible range of glazing used in automotive glass.

[0064] The glass articles obtained according to the invention can thus be advantageously used as single or monolithic glazing (a single glass substrate), or as multiple glazing, for example double glazing, or even as laminated or laminated glazing, without any problems during the lamination or lamination process. Laminated or laminated glazing is conventionally understood to mean glazing comprising at least two glass substrates joined by a plastic film, for example of the polyvinyl butyral (PVB), poly(ethylene-vinyl acetate) (EVA), polyurethane (PU), or a mixture thereof type. In this case, the stack of layers and the sol-gel layer, as defined above, are preferably deposited on one of the inner faces of the laminated glazing, that is to say, on face 2 or 3 of the glazing, the faces being conventionally numbered from 1 to 4 from the outside to the inside of the glazing.

[0065] The invention also relates to a windscreen, a side window, or a roof window of a motor vehicle, or a building window, or a train window comprising a glass article as defined above. EXAMPLES

[0066] The following examples illustrate the invention in a non-limiting manner.

[0067] In all examples below, the substrates used are 4 mm thick soda-lime-silicon sheets of the Planiclear® type marketed by Saint-Gobain Glass France. Example 1 according to the invention

[0068] A stack of mono-silver type layers is deposited on a Planiclear® type glass substrate. This stack comprises successively, starting from the glass substrate, a silver layer and two anti-reflective coatings, each anti-reflective coating having at least one dielectric layer, such that each silver layer is disposed between two anti-reflective coatings.

[0069] Thus, the stack comprises, starting from the glass substrate, the following thin layers: Si3N4(20nm) / SnZNO (10nm) / ZnO (5nm) / Ag (10nm) / ZnO (5nm) / SnZnO (10nm) / Si3N4(20nm) / TiOx (1nm).

[0070] Each of the stack layers is deposited by magnetic field assisted sputtering (magnetron).

[0071] Then, after hydrolysis at 60°C under reflux for 1h, a liquid sol-gel solution obtained from a mixture of 80.2 g of tetraethylorthosilicate (TEOS) of formula Si(OEt)4, 142.1 g of ethanol and 27.7 g of 0.05 mol.L hydrochloric acid*, is applied over said stack of layers, by dipping coating.

[0072] The sol-gel solution is dried for 10 minutes on a hot plate at 100°C and the average thickness of the sol-gel layer thus formed is 600 nm.

[0073] The glazing thus obtained is then subjected to a heat treatment, such as annealing, by heating the glazing to 650 °C for 10 min, so as to crack the dried sol-gel layer and damage the stack of layers.

[0074] A sheet of PVB is then deposited onto the cracked sol-gel layer, followed by the deposition of a second glass substrate. The glazing is then laminated to form the following laminated glazing 1, corresponding to the laminated glazing according to the invention: glass substrate / damaged layer stack / cracked sol-gel layer / PVB / glass substrate Comparative example of Ibis (outside the scope of the invention)

[0075] The comparative Ibis laminated glazing (not part of this invention) is identical to that obtained above except that it does not include a sol-gel layer, as follows: glass substrate / damaged layer stack / PVB / glass substrate

[0076] A-Measurement of the characteristics of the glazing The radio frequency transparency, optical and solar control characteristics of the glazing obtained according to the examples were measured according to the following principles and standards: 1°) Transparency properties to radio frequency waves RF transparency measurements are performed in an anechoic chamber, a chamber isolated from all external waves. Measurements are taken by sending a 4 to 14 GHz wave through the glass, and an antenna placed on the other side receives the signal. The RF value considered is that between 6 and 14 GHz.

[0077] The radio frequency wave transparency properties are also evaluated by determining the resistance "Rsq", using a measuring device called Nagy.

[0078] 2°) Optical properties and solar control The measurements are carried out in accordance with the European standard NF EN 410 (2011). More specifically, the light transmission "TL" is measured between 380 and 780 nm depending on the illuminant D65.

[0079] The solar control properties of the glazing are evaluated by determining the total solar energy transmitted "TTS" according to the conditions described in standard NF EN 410 (2011).

[0080] 3°) Aesthetic properties The width of the cracks is measured using an optical microscope.

[0081] B-Results The results obtained for laminated glazing according to the examples described above are grouped in Table 1 below:

[0082] [Tables 1] Examples RF (dB) Rsq (Q / D) tl (%) TTS (%) Width (pm) Laminated glazing 1 with cracked sol-gel coating (inv.) 0 to -l 00 71.3 53.4 2.1 pm Laminated glazing Ibis without cracked sol-gel coating (comp.) -35 3.5 71.5 53.5 —

[0083] The results reported in this table show that the laminated glazing 1 obtained according to the invention (i.e., comprising a cracked sol-gel layer exhibiting fine cracks or fissures of width equal to 2.1 pm) transmits radio electromagnetic waves compared to the laminated glazing Ibis (not part of the invention) without said cracked sol-gel layer, since the laminated glazing 1 according to the invention has a radio frequency transparency value close to 0 dB (RF between 0 and -1 dB) and an infinite resistance per square, whereas the RF value of the laminated glazing Ibis is far from 0 dB (RF equal to -35 dB) and the resistance per square is very low, on the order of 3.5 Ω.

[0084] On the other hand, it is observed that the presence of the cracked sol-gel layer does not modify the optical properties, nor the solar control properties, of the laminated glazing which is equipped with it, since the light transmission (TL) as well as the total solar energy transmitted (TTS) obtained for the two laminated glazings are almost identical.

Claims

Demands

1. A method for manufacturing a glass article comprising the following steps: - providing a glass substrate, - depositing, on at least one face of said glass substrate, a stack of layers comprising at least one functional metallic layer containing silver, each of said layers being deposited by magnetic field-assisted sputtering, - applying a sol-gel solution comprising at least one silicon oxide precursor and / or at least one transition metal oxide precursor, said solution being applied over said stack of layers, so as to form a sol-gel layer having an average thickness of between 50 nm and 3000 nm, preferably between 70 nm and 1500 nm, - heat treatment at a temperature above 500°C, preferably between 540°C and 700°C, so as to crack the sol-gel layer and damage the stack of layers.

2. A process according to claim 1, wherein the silicon oxide precursor is: • an inorganic silicon salt of general formula (I) as follows: SiXy, in which X is a halogen and y is an integer equal to 4, or • a silicon alkoxide selected from: - alkoxysilanes of general formula (II) as follows: Si(OR')z, in which R1 is independently selected from CrC4 alkyls, and z is an integer equal to 4, and - alkoxysilanes of general formula (III) as follows: Si(OR1)4 kR2k, in which R1 is independently selected from CrC4 alkyls, k is an integer between 1 and 3, and R2 is independently an alkyl group substituted with or without a reactive function, and - a mixture of these alkoxysilanes.

3. A process according to claim 1, wherein the transition metal oxide precursor is: - an inorganic salt of general formula (IV) as follows: MXy, in which M is chosen from Ti, Al, Zr, Ce and Zn, X is a group chosen from chlorides, nitrates, acetates, and y is an integer between 2 and 4, or - a transition metal alkoxide of general formula (V) as follows: M(OR)z, in which M is chosen from Ti, Al, Zr, Ce and Zn, R is independently chosen from the alkyls in Ci-C4z is an integer between 2 and 4.

4. A method according to any one of the preceding claims, wherein the layer stacking successively comprises, from the glass substrate, an alternation of x functional metallic layers containing silver, and (x+1) antireflective coatings, each antireflective coating comprising at least one dielectric layer, such that each functional metallic layer containing silver is disposed between two antireflective coatings.

5. Method according to claim 4, wherein the layer stack comprises a single functional metallic layer containing silver, x is equal to 1.

6. A method according to any one of the preceding claims, wherein the application of the sol-gel solution to the glass substrate is carried out by roller coating, curtain coating, slit coating, dip coating, blade coating, spraying, squirting, or inkjet printing.

7. A method according to any one of the preceding claims, wherein the heat treatment is quenching, bending, or annealing.

8. A method according to any one of the preceding claims, wherein the glass substrate is coated in whole or in part with a layer of enamel before the deposition of the layer stack.

9. A method according to any one of the preceding claims, comprising, immediately after the sol-gel solution application step and before the heat treatment step, a drying step.

10. Glass article obtained according to the process of any one of claims 1 to 9, comprising a glass substrate coated on at least one of its faces: - of a layer stack comprising at least one functional metallic layer containing silver, and - of at least one sol-gel layer located above said layer stack and having an average thickness between 50 nm and 3000 nm, preferably between 70 nm and 1500 nm, said layer stack and said sol-gel layer having cracks or fissures.

11. Glass article according to claim 10, characterized in that the cracked sol-gel layer has a refractive index between 1.3 and 2.3, preferably between 1.4 and 1.8, and more preferably between 1.4 and 1.6, measured at a wavelength of 630 nm.

12. Glass article according to claim 10 or 11, wherein the width of the cracks or fissures present in the stack of layers and in the sol-gel layer is between 0.5 pm and 5 pm.

13. Glass article according to any one of claims 10 to 12, further comprising an enamel layer disposed between the glass substrate and the stack of layers exhibiting cracks and fissures.

14. Glass article according to any one of claims 10 to 13, wherein the sol-gel layer is in direct contact with the stack of layers which includes at least one functional metallic layer containing silver.

15. Windscreen, side window, or roof window of a motor vehicle, or building glazing, or train glazing comprising a glass article, according to any one of claims 10 to 14.