EP3873862A1

EP3873862A1 - Coated substrate

Info

Publication number: EP3873862A1
Application number: EP19779510.7A
Authority: EP
Inventors: Eric BOSGAERD; Eugénie PEYROUX; David Pierre
Original assignee: AGC Glass Europe SA; AGC Vidros do Brasil Ltda; Asahi Glass Co Ltd; AGC Flat Glass North America Inc
Current assignee: AGC Glass Europe SA; AGC Vidros do Brasil Ltda; AGC Inc; AGC Flat Glass North America Inc
Priority date: 2018-10-29
Filing date: 2019-10-04
Publication date: 2021-09-08
Also published as: WO2020088880A1

Abstract

The present invention relates to a dried coated substrate comprising: - a substrate, - a soft coating, - a dried sol-gel coating obtained from a sol-gel solution comprising: at least one organic polymer and at least one silicon oxide precursor and at least one oxide precursor of titanium or zirconium, to a process for making a coated substrate, to a densified coated substrate and to glazing units comprising such densified coated substrate.

Description

Coated substrate

Technical field of the invention

The invention relates to a dried coated substrate provided with a soft coating such as a solar control or an insulating low-E coating with an increased mechanical, chemical and corrosion resistance thanks to the presence above the soft coating of a dried protective sol-gel coating. The invention also relates to a densified coated substrate and to the process for making said coated substrates. The invention particularly relates to dried and densified glass coated substrates. The invention also relates to single glazing, multiple glazing and laminated glazing comprising said densified coated glass substrates.

Background of the invention

A large part of soft coatings such as solar control or insulating low-E coatings present a low emissivity and are used in glazing for their IR reflecting ability, allowing a precise energy control of the glazing, thereby reducing heat loss and/or avoiding over-heating of a glazed structure. Unfortunately, the limited mechanical, chemical and corrosion resistance of most soft coatings limits their use. Indeed, such coatings can be easily damaged by exposure to the environment during their production or during their lifetime. Mechanical actions such as contact or friction with other materials or objects can result in scratches or mars. Modifications of the chemical environment (humidity, temperature...) or contact with chemicals like detergent or everyday life products leads to a degradation of the soft coating surface. The result of such deteriorations could be both aesthetic and functional. This is particularly true for soft coatings that rely on metal-based infrared reflecting layers. Even if some soft coatings, without metal-based infrared reflecting layers can be used on exterior faces of glazing, their durability does not reach that of hard coatings produced by chemical vapor deposition (CVD).

During the production of coatings on substrates like glass or polymer sheets, the coated sheets are often scratched due to one or more of: (a) rubbing up against other sheets or the like during shipment; (b) pliers used by glass handlers during and/or proximate cutting or edge seaming steps; (c) abrasion caused by gloves worn by glass handlers; (d) brushes during washing step; and (e) other types of rubbing/abrasion caused during any step at fabricator premises. Additionally, corrosion is also a significant cause of damage of glass sheets and is often caused by high humidity conditions, acid rain, and/or other materials which tend to collect on the coated articles during transport, storage and/or handling.

For glass sheets, while the aforesaid types of damage often occur prior to heat treatment (e.g., tempering), the tempering of the coated sheets typically magnifies such damage. For example, a minor bit of corrosion which was caused pre tempering can lead to a significant blemish upon heat treatment which causes the coated sheet to be scrapped.

Many applications or markets are demanding soft coatings, particularly solar control or insulating low-E coatings for their opto-energetic properties and their ability to block a portion of the IR spectrum. However, the limited mechanical, chemical and/or corrosion resistance of soft coatings limits their use in simple glazing, for interior or exterior use, or in the case of multiple glazing their use in external positions, i.e. on the faces of the glazing facing the exterior of the glazing.

A known method to obtain a glazing with a protected low-E coating is to make use of energy saving window films such as those commercialized by Nitto under the names Penjerex® PX-7060S or Penjerex® PX-8080. These adhesive films contain a low-E coating protected by a polyester film. However, for durability reasons, such films can only be used on the face of the glazing in contact with the interior of a building, they are not heat treatable and oblige the windows maker or the end user to install them on site.

Deposition of a sol-gel coating on a low-E undercoat on glass is disclosed in US20070243391. The sol-gel coating aims at efficiently blocking ultraviolet (UV) radiations and comprises very high amounts of cerium oxide as UV blocker. US20070243391 is silent about the mechanical, chemical and corrosion protection of the low-E coating and the impact of this sol-gel coating on the emissivity of the low-E coating.

Deposition of a temporary protective layer on a functional coating is disclosed in US20160194516. This temporary protective layer is based on the (meth) acrylates chemistiy and protects the functional coating during the processing of the glass until tempering or annealing. The protective layer burns during tempering or annealing and consequently the functional coating resistance after tempering or annealing is so not improved in comparison to a situation where no protective layer is used.

Thus, there is a need to develop substrates, particularly glass substrates provided with a soft coating and having improved mechanical, chemical and corrosion resistance during all the processing steps and lifetime of the product while not significantly impacting the emissivity and/or the aesthetics of the coating. Summary of the invention

Against this background we now provide a dried coated substrate comprising:

• a substrate,

• a soft coating comprising one or more layers deposited by physical vapor deposition provided on at least a part of at least one face of the substrate,

• a dried sol-gel coating provided on at least a part of said face above the soft coating,

wherein the dried sol-gel coating is obtained by applying and subsequently drying, a sol-gel solution comprising: at least one organic polymer, at least one silicon oxide precursor and at least one oxide precursor of titanium or zirconium.

There is also provided a densified coated substrate obtained by the densification of the dried sol-gel coating.

One objective of the invention is to provide in at least one of its embodiments a dried or densified coated substrate comprising a soft coating having improved mechanical, chemical and corrosion resistance thanks to the presence of the sol-gel coating.

Another objective of the invention is to provide in at least one of its embodiments a dried or densified coated substrate comprising a soft coating that is a solar control or insulating low-E coating deposited by Physical Vapor Deposition (PVD) and having improved mechanical, chemical and corrosion resistance thanks to the presence of the sol-gel coating while the emissivity of the solar control or insulating low-E coating is not significantly impacted.

It is yet another objective of the invention in at least one of its embodiments to provide a dried or densified coated substrate comprising a soft coating that can be exposed to the environment, i.e. that can be applied on faces of the substrate in contact with the environment. The dried or densified coated substrate can more particularly be exposed to the environment of the inside of a building.

It is still another objective of the invention in at least one of its embodiments to provide a dried coated glass substrate that is suitable to be heat treated or suitable to be tempered.

It is another objective of the present invention to provide in at least one of its embodiments a long-lasting densified coated glass substrate for saving energy in applications such as buildings, home appliances, transportation (automobile, bus, boat, train, tramway and the like) or greenhouses. It is yet another objective of the invention in at least one of its embodiments to provide a dried coated substrate wherein the soft coating is already protected when provided to the customer or end user who has no additional protection step to perform.

The present invention also provides a process for making the dried coated substrate and for making the densified coated substrate, as well as the densified coated substrate per se.

The present invention also provides glazing units comprising the densified coated substrate wherein the substrate is glass, and particularly single or multiple glazing units.

It is an objective of the present invention to provide in at least one of its embodiments glazing units allowing the face of the coated glass substrate covered by the soft coating and the sol-gel coating to face the outside of the unit, i.e. to be in contact with the exterior of the glazing, more particularly when the glazing is used inside of a building , thanks to improved mechanical, chemical and corrosion resistance.

Description of the invention

In a first aspect of the invention, there is provided a dried coated substrate comprising:

a substrate,

a soft coating comprising one or more layers deposited by physical vapor deposition provided on at least a part of at least one face of the substrate,

a dried sol-gel coating provided on at least a part of said face above the soft coating,

characterized in that the dried sol-gel coating is obtained by applying and subsequently drying, a sol-gel solution comprising:

at least one organic polymer and

at least one silicon oxide precursor and

at least one oxide precursor of titanium or zirconium.

The substrate can be any substrate such as for instance glass, glass-ceramic, ceramic, steel, metal and transparent polymers such as polycarbonate (PC), polyethylene terephthalate (PET), polystyrene (PS), polyvinyl chloride (PVC), polymethyl methacrylate (PMMA). The substrate according to the invention may be flat or curved/bended. Suitable substrates according to the invention preferably can withstand a heat treatment at at least 300°C, more preferably at at least 400°C. The substrate is preferably glass, glass-ceramic, ceramic, steel, metal. According to the invention, the substrate is preferably a glass substrate, more preferably a glass sheet. According to an embodiment, the glass sheet is a float glass sheet. The term“float glass sheet” is understood to mean a glass sheet formed by the float method, which consists in pouring the molten glass onto a bath of molten tin, under reducing conditions. A float glass sheet comprises, in a known way, a“air face” and a“tin face”, the last one being a face enriched in tin in the body of the glass close to the surface of the sheet. The term“enrichment in tin” is understood to mean an increase in the concentration of tin with respect to the composition of the glass at the core, which may or may not be substantially zero (devoid of tin). Therefore, a float glass sheet can be easily distinguished from sheets obtained by other glassmaking methods, in particular by the tin oxide content which may be measured, for example, by electronic microprobe to a depth of ~ to microns. In many cases and as illustration, this content lies between l and 5 wt%, integrated over the first 10 microns starting from the surface. Alternatively, the glass sheet is a cast or drawn glass sheet.

The glass sheet according to the invention is made of glass whose matrix composition is not particularly limited and may thus belong to different categories. The glass may be a soda-lime-silicate glass, an alumino-silicate glass, an alkali-free glass, a boro-silicate glass, etc. It may be a clear, extra-clear/low-iron or coloured glass sheet. Preferably, the glass sheet of the invention is made of a soda-lime glass or an alumino-silicate glass. Non-limiting examples of glass sheets are Planibel® Clear, Planibel® Coloured, Linea Azzura®, Dragontrail®, Tirex®, Falcon®, Clearvision®, Clearlite®.

The glass sheet of the invention can be of any desired dimensions, such as length, width, shape and/or thickness. In one embodiment, the glass sheet of the invention may have a thickness of from 0.1 to 25 mm.

For the purpose of the present invention a soft coating is a coating comprising one or more layers deposited by physical vapor deposition (PVD) in particular by magnetron sputtering. In particular, a soft coating may comprise one or more metal based infrared reflecting layers that are typically surrounded by two or more dielectric layers. The metal based infrared reflecting layer is most often based on silver but may also be based on metals such as for example nickel, chromium, niobium, tungsten, zirconium, titanium stainless steel or mixtures thereof. The dielectric layers may comprise one or more metal oxides or metal nitrides or metal oxynitrides or metal carbides or diamond-like carbon layers. In a typical embodiment of the present invention the soft coating comprises p functional layer(s) reflecting infrared radiation and p+i dielectric layers, with p³i, each functional layer being surrounded by dielectric layers. In certain embodiments, a soft coating may also be a coating deposited by physical vapor deposition (PVD) in particular by magnetron sputtering which is devoid of any metallic layer and comprises only one or more layers of one or more metal oxides or metal nitrides or metal oxynitrides or metal carbides or diamond-like carbon or transparent conductive oxides.

Soft coatings produced by PVD, in particular comprising metallic functional layers, have generally a limited mechanical, chemical and corrosion resistance hence limiting their possible uses in contact with the environment.

The soft coating may in particular be a solar control or insulating low-E coating. For example, and without limitation, such solar control or insulating low-E coatings may be single silver, double silver or triple silver coating stacks, or any of the soft coatings in any of the following WO2005012200, WO2006122900, WO2007138097, WO2011147875, WO2011147864, WO2013079400, WO2014191472, WO2014191474, WO2014191484, all of which are hereby incorporated by reference.

Suitable soft coatings in the frame of the present invention are for instance Sunlux or Stopsol commercialized by Asahi Glass Company. Examples of solar control or insulating low-E coating suitable for the invention are Silver Smart (such as 30/51/69), Planibel AS, iplustop (such as 1.1T, 1.0T, Stopray (Vision 50, 60, 72, 61, 41, and 40 and ultra 50 and 60 )) and Energy N also commercialized by Asahi Glass Company.

The soft coating of the invention is provided on at least a part of at least one face of the substrate. It can be provided on a part of said face or substantially on the entire said face. It can be provided on a part of the face as it is the case for the so called edge deleted glass sheet. In this case, the soft coating is removed on the periphery of the face of the coated glass sheet. It can alternatively be provided substantially on the entire said face. By substantially on an entire entity (here the face) is meant that at least 90% of the entity is covered, preferably at least 95%, more preferably at least 97%, most preferably 100% of the entity is covered. The soft coating can be provided on anyone of the faces of the substrate or on both faces.

The dried sol-gel coating of the invention is provided on at least a part of the face of the substrate provided with the soft coating and above the soft coating. Both the soft coating and the dried sol-gel coating can cover substantially the entire face of the substrate or they can both cover the same part of the face or the soft coating can cover a part of the face and the dried sol-gel coating can cover a larger part of or substantially the whole face of the substrate. The dried sol-gel coating is provided above the soft coating and it can either be in direct contact with the soft coating or separated from the soft coating by one or more intermediate layers. The dried sol-gel coating is preferably provided in direct contact with the soft coating, i.e. no intermediate layer is present between the soft coating and the dried sol-gel coating on the portions of the surface where they are both present. It is more preferably provided in direct contact with the soft coating and at least substantially on the entire soft coating.

The dried sol-gel coating is obtained by applying and subsequently drying a sol- gel solution.

By dried sol-gel coating is meant a sol-gel coating exempt of any volatile compound. By volatile compound is meant any compound having a boiling point of at most 250°C measured at standard pressure. By exempt is meant that the residual content of such volatile compounds is close to zero. It is generally below 3 wt%, preferably below 2 wt%, more preferably below 1 wt%, most preferably below 0.5 wt% of the dried sol-gel coating. The wt% of volatile compounds is determined by thermogravimetric analysis (TGA) under air, from 20 to 300°C at a heating rate of io°C/min. The wt% of volatile compounds is the weight loss measured by TGA under these conditions on a sample of dried sol-gel coating obtained from the sol-gel solution that has been dried under air at 150°C for 7 minutes.

The dried sol-gel coating is typically obtained by drying the sol-gel solution at a temperature ranging from ioo°C to 250°C for a certain duration. The temperature and duration conditions are adapted depending on the type of sol-gel solution applied. A typical drying is 150°C for 7 minutes. Besides the evaporation of the volatile compounds, the drying may also lead to partial or total crosslinking of the oxide precursors depending on the temperature and the heating duration.

The application methods are described later in the process description.

For the purpose of the present invention, the sol-gel solution comprises:

at least one organic polymer and

at least one silicon oxide precursor and

at least one oxide precursor of titanium or zirconium.

The sol-gel solution hence comprises:

at least one organic polymer, at least one silicon oxide precursor and at least one titanium oxide precursor, or

at least one organic polymer, at least one silicon oxide precursor and at least one zirconium oxide precursor, or

at least one organic polymer, at least one silicon oxide precursor, at least one titanium oxide precursor and at least one zirconium oxide precursor. In a preferred embodiment, the sol-gel solution preferably comprises at least one organic polymer, at least one silicon oxide precursor, at least one titanium oxide precursor and at least one zirconium oxide precursor.

In another embodiment, the sol-gel solution comprises at least one organic polymer, at least one silicon oxide precursor, at least one titanium oxide precursor and at least one zirconium oxide precursor wherein said precursors sum up to ioo% of the metal and metalloid oxide precursors of the sol-gel solution.

The sol-gel solution is an homogeneous mixture meaning that it has the same proportions of its constituents throughout any given sample. Having a homogeneous sol-gel solution is an important parameter to obtain a dried and a densified coating with the desired performances, low thickness dispersion and aesthetics.

For the purpose of the invention, by polymer is meant a chemical compound having a structure comprising covalently bonded repetitive units. An organic polymer is a carbon-containing polymer. The carbon may be present in the polymer main backbone and/or in side groups. The organic polymers may be natural polymers like cellulose or synthetic polymers which are not present in nature and are industrially produced. The organic polymers suitable for the invention are preferably synthetic polymers. The organic polymers may be linear, branched or crosslinked. The organic polymers of the invention are preferably linear or branched polymers or mixtures of these.

The organic polymer preferably comprises at least 3 covalently bonded repetitive units and preferably more than 3 repetitive units. It is characterized by a number average molecular weight, a weight average molecular weight and a molecular weight distribution, which are known parameters of a polymer that are for instance determined by gel permeation chromatography (GPC) making use of a polystyrene calibration. The analysis conditions such as the solvent, the set of columns, the temperature, the detection system have to be adapted to the type of polymer to be analysed.

The organic polymers suitable for the invention have typically a weight average molecular weight ranging from 200 to 1000000 Daltons. They have preferably a weight average molecular weight of at least 500 Daltons, more preferably of at least 2000 Daltons, most preferably of at least 5000 Daltons. They have preferably a weight average molecular weight of at most 700000 Daltons, more preferably of at most 500000 Daltons, most preferably of at most 300000 Daltons.

The organic polymers suitable for the invention have typically a glass transition temperature (Tg) ranging from 20°C to 400°C. They have preferably a Tg of at least 25°C, more preferably of at least 35°C, most preferably of at least 50°C. They have preferably a Tg of at most 350°C, more preferably of at most 300°C, most preferably a Tg of at most 250°C. The glass transition temperature is a known parameter of a polymer and is measured by differential scanning calorimetry according to ISO 11357-2 Part 2.

Without wishing to be bound by any theory, it is believed that the organic polymer needs to have a weight average molecular weight of at least 200 Daltons and a Tg of at least 25°C to bring an improvement in terms of performances of the dried sol-gel coating. Hence particularly preferred organic polymers are linear and/or branched synthetic polymers having a weight average molecular weight of at least 200 Daltons, preferably at least 500 Daltons, more preferably at least 2000 Daltons, most preferably at least 5000 Daltons and a Tg of at least 25°C.

Non exhaustive examples of organic polymers suitable for the present invention are acrylic polymers, polyacrylamides, polycarbonates, polyurethanes, polyesters, polyolefins, polydienes, polyamides, polyimides, polyethers, silicones, polyalkylene oxides. Copolymers are also suitable organic polymers. Examples are vinyl copolymers obtained from at least two different vinyl monomers such as aciylic copolymers, styrene-acrylic copolymers, ethylene- vinyl acetate copolymer, stiyrene-acrylonitrile copolymer, stiyrene-butadiene-styrene copolymer and the like. Mixtures or several of these organic polymers may also be used.

The presence of the organic polymer is advantageous in that it improves the mechanical, chemical and corrosion resistance of the dried sol-gel coating and in consequence, it improves the protection of the underlying soft coating. As a consequence, the dried coated substrate provided with the soft coating and the dried sol-gel coating may be handled and transported before densification with no or reduced risk of damage. It is of particular interest when the substrate is glass. In this case, the dried coated substrate can be exposed to the environment during its production or during its lifetime. It may advantageously be transported to the end user who may be cut it at the desired size and grind it before heat treatment.

The organic polymer may be provided in any suitable form such as a finely dispersed powder, a solution, an aqueous dispersion. It is preferably provided in the form of a solution or an aqueous dispersion giving a homogeneous solution with the other sol-gel solution constituents.

An example of such an aqueous dispersion usable for the purpose of the present invention is an aqueous dispersion of polyurethane such as Daotan® TW7000/40WA.

A metal or metalloid oxide precursor has here its general meaning, e.g. a species corresponding to the general formula Rv-xM(X)x where M is a metal or a metalloid having a valence v; R is typically a saturated or an unsaturated alkyl group, a linear or branched alkyl chain, optionally containing heteroelements such as O, N, S, Br, Cl, I; and X is a leaving group such as an alkoxide, an hydroxide, an halide (such as a chloride, a bromide an iodide or a fluoride), a perfluoroalkylsulfonate, a tosylate, a mesylate, a carboxylate, a phenoxide, a thioether, a nitrate, a phosphate or other inorganic esters. The same or different R groups and X groups may be present on the same precursor. The wording metal also covers the transition metal elements.

Suitable silicon oxide precusors are silicon alkoxydes and silane halides. For instance tetraethylorthosilicate (TEOS), methyltriethoxysilane (MTES), methyltrimethoxysilane (MTMS), (3-aminopropyl)-triethoxysilane (APTES), (3- Glycidyloxypropyl)trimethoxysilane (GPTMS) and the like. A preferred silicon oxide precursor is (3-Glycidyloxypropyl)trimethoxysilane. Combinations of different silicon oxide precusors can be used.

Suitable titanium oxide precursors are for instance titanium (IV) isopropoxide, titanium (IV) butoxide or titanium (IV) tert-butoxide. Preferred are titanium (IV) isopropoxide and titanium (IV) butoxide. Combinations of such precursors can be used.

When present, titanium oxide advantageously allows improving the chemical and corrosion resistance of the dried and the densified sol-gel coatings and hence the protection of the underlying soft coating.

For the purpose of the present invention, suitable zirconium oxide precursors are for instance zirconium alkoxides such as zirconium (IV) butoxide, zirconium (IV) isopropoxide, zirconium (IV) tert-butoxide), or under the form of zirconium (IV) salts such as zirconium(IV) acetylacetonate. Preferred ones are zirconium (IV) butoxide or zirconium (IV) isopropoxide. Combinations of such precursors can be used.

Zirconium oxide, when present participates to the improvement of the mechanical resistance of the dried and densified sol-gel coatings such as the scratch resistance and to the improvement of the corrosion resistance. It improves particularly the corrosion resistance.

The sol-gel solution may optionally further comprise bismuth oxide or cerium oxide precursors or a mixture of bismuth oxide and cerium oxide precursors.

Suitable precursors of bismuth oxide or cerium oxide are bismuth or cerium salts or organometallic derivatives like metal alkoxides. Examples of such bismuth oxide precursors are bismuth nitrate, bismuth chloride, bismuth citrate, bismuth acetate, bismuth phosphate and the like. Examples of precursors of cerium oxide are cerium nitrate, cerium acetate, cerium chloride, cerium sulfate, cerium acetylacetonate and the like. Certain species may also exist under their hydrate forms which are also suitable precursors. Preferably, the precursor of bismuth oxide is bismuth nitrate and the precursor of cerium oxide is cerium nitrate. Combinations of such precursors can be used.

The sol-gel solution may optionally further comprise phosphorous oxide precursors such as phosphoric acid and/or a phosphite alkoxide such as triethylphosphite. Preferred is triethylphosphite.

The sol-gel solution may optionally also comprise precursors of one or several other metal oxides such as AI2O3, Fe203, Sn02, Ta02. Examples of such precursors are the corresponding nitrate or chloride salts.

A typical sol-gel solution also comprises a solvent or a solvent mixture for the metal and metalloid oxide precursors solution, and water. The solvent or solvent mixture used can be any of those known to the skilled person for sol-gel solution preparation. These solvents are solvents miscible with water such as alcohols, for instance: methanol, ethanol, isopropanol, butanol, 2-ethoxy-ethanol, i-methoxy-2-propanol; or ketones such as acetone and methylethylketone. As water-miscible solvents, ethylcellosolve, butylcellosolve, cellosolve acetate, diacetone alcohol, tetrahydrofurfuryl alcohol and mesityl oxide can also be mentioned. Mixtures of solvents can be used. In the present invention, when the organic polymer is provided in the form of a solution, the solvent of said solution must be miscible with the solvent or solvent mixture used to dissolve the precursors, while homogeneity of the sol-gel solution is preserved.

A catalyst may optionally be used, it can be chosen amongst the catalysts known to the skilled person for sol-gel preparation, such as an inorganic acid, for instance hydrochloric acid, nitric acid, sulfuric acid; or an organic acid such as acetic acid, citric acid, formic acid. Preferred are nitric acid and hydrochloric acid.

A stabilizing agent may also optionally be used, it can be chosen amongst the stabilizing agents known to the skilled person for sol-gel preparation, such as acetylacetone, ethyl acetoacetate or hydroxypropyl cellulose. Preferred is ethyl acetoacetate.

The sol-gel solution may further optionally comprise other additives such as hydrophobic or oleophobic or omniphobic substances to confer an easy maintenance property to the final coating, coloring components (eg. inorganic pigments).

In a preferred embodiment, the sol-gel solution comprises the organic polymer and silicon oxide precursor in a weight ratio of :

organic polymer weight / silicon oxide precursor weight expressed as silicon oxide theoretical weight ranging from 0.10 to 3,

The claimed ranges also comprise the limits of the ranges. When the organic polymer is provided in a solid form, its weight is expressed in grams (g). When it is provided as a solution or a dispersion, the weight of the organic polymer is defined by the following formula :

Weight polymer ⁼ GP polymer solution/dispersion · SC polymer solution/dispersion where,

m polymer solution/dispersion is the mass in g of the polymer solution or dispersion of the sol-gel solution.

SC polymer solution/dispersion is the solid content of the polymer solution or dispersion

If there is more than one organic polymer solution and/or dispersion, the weight of the organic polymers of the sol-gel solution is the sum of the weight polymer of each polymer solution or dispersion. For instance, if there are two polymer solutions in the sol-gel solution, the total weight of organic polymer is equal to : m polymer solution/dispersion 1 . SC polymer solution/dispersion 1 + m polymer solution/dispersion 2 . SC polymer solution/dispersion 2.

The weight of a metal or metalloid oxide precursor of the sol-gel solution is expressed as the theoretical weight of the corresponding oxide according to the following formula:

Theoretical weight oxide— n oxide precursor · Meq oxide

where,

n _{oxide precursor} is the total number of metal or metalloid equivalents in the precursor(s) of a given metal or metalloid oxide. Equivalent has here its general meaning , i.e. number of moles of precursor multiplied by the number of metal or metalloid element(s) in the precursor. Depending on the sol-gel solution, there might be one or more precursors of a given metal or metalloid oxide. If there is a single precursor, n is the number of metal or metalloid equivalents of that given precursor. If there are for instance two precursors, n=ni+n2, where ni is the number of metal or metalloid equivalents of the first precursor and n2 is the number of metal or metalloid equivalents of the second precursor,

M_eq oxide is the metal or metalloid equivalent weight of the metal or metalloid oxide expressed in g/eq. The metal or metalloid equivalent weight is the molar weight of the metal or metalloid oxide divided by the number of metal or metalloid element(s) in the metal or metalloid oxide (for Bi203, the metal equivalent weight is the molar weight divided by 2). With a ratio of at least o.io, the content in organic polymer advantageously provides a significant performance improvement. On the other hand, when the ratio is above 3, the amount of organic polymer present in the dried sol-gel coating might be detrimental when densification of the dried sol-gel coating is performed. In this case, the organic polymer degradation upon heating during densification may be detrimental to the coating integrity. Holes, cracking, delamination of the coating may appear. The weight ratio organic polymer /silicon oxide precursor is preferably at least 0.25, more preferably at least 0.5, most preferably at least 1. The ratio is preferably at most 2.5, more preferably at most 2, most preferably at most 1.5.

In another preferred embodiment where a titanium oxide precursor is present, the ratio titanium oxide precursor weight expressed as titanium oxide theoretical weight/ silicon oxide precursor weight expressed as silicon oxide theoretical weight ranges from 0.10 to 3. The ratio is preferably at least 0.25, more preferably at least 0.5, most preferably at least 1. The ratio is preferably at most 2.5, more preferably at most 2, most preferably at most 1.5.

In yet another preferred embodiment where a zirconium oxide precursor is present, the ratio zirconium oxide precursor weight expressed as zirconium oxide theoretical weight / silicon oxide precursor weight expressed as silicon oxide theoretical weight ranges from 0.10 to 3. The ratio is preferably at least 0.25, more preferably at least 0.5, most preferably at least 1. The ratio is preferably at most 2.5, more preferably at most 2, most preferably at most 1.5.

With a ratio of at least 0.10, the amount of zirconium oxide provides a significant improvement of the mechanical and corrosion resistance of the dried and densified sol-gel coatings. Values above the upper limit of the range will limit the amounts of silicon oxide and/or titanium oxide in the dried or densified sol-gel coating. Too low amounts of silicon oxide might be detrimental to the adhesion, while too low amounts of titanium oxide might be detrimental to chemical resistance.

In a more preferred embodiment, the organic polymer, silicon oxide precursor(s) and both titanium oxide precursor(s) and zirconium oxide precursor(s) are present in the above amounts. In this case, the ratio titanium oxide precursor weight expressed as titanium oxide theoretical weight /zirconium oxide precursor weight expressed as zirconium oxide theoretical weight ranges from 0.10 to 10. The ratio is preferably at least 0.25, more preferably at least 0.5, most preferably at least 1. The ratio is preferably at most 6, more preferably at most 4, most preferably at most 2. When bismuth oxide precursor(s) are present, the ratio bismuth oxide precursor weight expressed as bismuth oxide theoretical weight /silicon oxide precursor weight expressed as silicon oxide theoretical weight ranges from o to 0.03. The ratio is preferably at most 0.02, more preferably at most 0.01.

When cerium oxide precursor(s) are present, the ratio cerium oxide precursor weight expressed as cerium oxide theoretical weight / silicon oxide precursor weight expressed as silicon oxide theoretical weight ranges from o to 0.03. The ratio is preferably at most 0.02, more preferably at most 0.01.

The optional use of cerium oxide as doping agent in low amounts is advantageous as it does not impact significantly the color, it has particularly a low yellowing effect.

When other metal or metalloid oxide precursors such as precursors of AI2O3, Fe203, Sn02, Ta02 or any mixtures of those are used, they are present in a total amount of maximum 3 wt % of the dried coating composition. By wt% (weight percent) is meant the number of gram of said precursors per toog of dried sol gel coating.

The thickness of the dried sol-gel coating typically ranges from 70 to 1000 nm. The thickness is preferably at least 150 nm and preferably at most 700 nm. When the thickness is too low, the protective effect of the coating is less efficient and when the thickness is too high, the risk to create cracks into the coating during a densification step is high due to the shrinkage of the sol-gel.

It is another object of the invention to provide a process for making a coated substrate comprising the steps of:

a) forming a soft coating comprising one or more layers deposited by physical vapor deposition on at least a part of at least one face of the substrate,

b) applying a sol-gel solution on at least a part of said face above the soft coating, the sol-gel solution comprising:

at least one organic polymer and

at least one silicon oxide precursor and

at least one oxide precursor of titanium or zirconium,

c) drying the sol-gel solution to obtain a dried sol-gel coating.

All features and embodiments described above in relation with namely the substrate, the soft coating, the sol-gel solution, the dried sol-gel coating, the drying apply to the process description as well. The process comprises the step of forming a soft coating comprising one or more layers deposited by physical vapor deposition on the substrate. It may be applied for instance by sputtering by the well-known method of magnetron sputtering.

The soft coating is formed on at least a part of at least one face of the substrate. It can be provided on a part of said face or substantially on the entire said face. It can be provided on a part of the face as it is the case for a so called edge deleted glass sheet. In this case, the soft coating is removed on the periphery of the face of the coated glass. It can alternatively be provided substantially on the entire said face. The soft coating can be provided on anyone of the faces of the substrate or on both faces.

The process for making a coated substrate according to the invention comprises a step of applying a sol-gel solution on at least a part of the face of the substrate provided with the soft coating and above the soft coating.

The sol-gel solution can be applied on the substrate by various methods such as bar coating, spin coating, dip coating, slot-die coating, spraying (i.e. LP pulverization, HVLP pulverization, airless pulverization or combined spraying technologies like Airmix®, DUO®, ...), ultrasonic deposition, electrospray deposition, curtain coating, roller coating, slit coating, flow coating, dipping method; or a printing method such as screen printing, gravure printing, inkjet printing and curved-face printing.

The application method is preferably electrospray deposition, ultrasonic deposition and ink jet printing, which advantageously allow obtaining a lower thickness dispersion of the dried and densified sol-gel coatings.

The sol-gel solution is applied on at least a part of the face of the substrate provided with the soft coating and above the soft coating. Both the soft coating and the sol-gel solution can cover substantially the entire face of the substrate or they can both cover the same part of the face or the soft coating can cover a part of the face and the sol-gel solution can cover a larger part or substantially the whole face of the substrate.

The sol-gel solution may be applied directly after the step of forming the soft coating on the substrate or one or several optional intermediate steps may be conducted in between.

An optional intermediate step may be for instance the application of one or more intermediate layers between the soft coating and the sol-gel solution. When no intermediate layer is applied, the sol-gel solution is in direct contact with the soft coating, i.e. no intermediate layer is present between the soft coating and the sol-gel solution on the portions of the surface where they are both present. It is preferred that the sol-gel solution is provided in direct contact with the soft coating and at least substantially on the entire soft coating. It is hence preferred that no step of applying an intermediate layer is performed.

Another optional intermediate step might be to move the substrate from a soft coating application line to a sol-gel application line.

The process for making a dried coated substrate according to the invention comprises a step of drying the sol-gel solution to obtain the dried sol-gel coating of the invention. This step is as described supra.

In a particular embodiment, the process comprises a subsequent step of densification of the dried sol-gel coating to obtain a densified sol-gel coating and densified coated substrate.

By densification is meant the reduction of the thickness of the dried sol-gel coating by application of heat during a given duration to obtain the densified sol-gel coating. The densification temperature generally ranges from 300 °C to 800 °C in air for a period of from 2 minutes to 10 minutes. It may particularly take place between 400 °C and 7io°C.

This embodiment is hence limited to substrates that can withstand said temperature ranges without major alteration. The substrates used in this embodiment must withstand a heat treatment at at least 300°C, preferably at at least 400°C. The substrate is preferably glass, glass-ceramic, ceramic, steel, metal. It is more preferably a glass substrate .

During densification, the crosslinking of the precursors is finalized if not fully performed during diying, the thickness of the dried sol-gel coating is reduced by the reduction of its porosity and the organic polymer is thermally degraded. The amounts of organic polymer according to the invention advantageously allow an improvement of the coating performances before densification, while the thermal degradation of the organic polymer during densification is not detrimental to the densified sol-gel coating integrity. The protection performances of the densified sol-gel coating are not negatively affected by the organic polymer thermal degradation.

In this embodiment, the application method of the sol-gel solution is preferably electrospray deposition, ultrasonic deposition and ink jet printing, which advantageously allow obtaining a lower thickness dispersion of the final densified sol-gel coating.

In a variant of this embodiment, the substrate is glass and the densification stage takes place during a heat treatment of the glass. The heat treatment of the glass may be one of those encountered in a bending (also known as curving), annealing (also known as strengthening) or tempering process. It is advantageous as more and more heat treated glass is requested in buildings and automotive applications namely for safety purposes. The heat treatment is known to the skilled person and is performed according to known methods. It generally comprises heating the glass sheet to a temperature between 300 and 8oo°C, in air, for example between 400°C and 7io°C, for a couple of seconds to several hours. The conditions are adapted depending on the heat-treatment type, the thickness and nature of the glass sheet, the type of soft coating and sol-gel solution applied. The treatment may comprise a rapid cooling step after the heating step, to introduce stresses difference between the surface and the core of the glass so that in case of impact, the so-called tempered glass sheet will break safely in small pieces. If the cooling step is less strong, the glass will then simply be annealed and in any case offer a better mechanical resistance.

In this variant, the step of densification is preferably a tempering step where a dried coated glass substrate is tempered.

In another aspect of the invention, there is provided a densified coated substrate obtained from the densification of the dried sol-gel coating. The densified coated substrate is preferably a densified coated glass substrate.

During densification, the organic polymer is thermally degraded. The densified sol-gel coating is hence mainly an inorganic densified sol-gel coating. It is usually a uniform network spread out in sheet-like manner. The networks of the invention can have open or closed pores.

The thickness of the densified sol-gel coating typically ranges from 30 to 500 nm. It is preferably at least 50 nm and more preferably at most 300 nm. When the thickness is too low, the protective effect of the coating is less efficient and when the thickness is too high, the risk to create cracks into the coating during the densification step is high due to the shrinkage of the sol-gel.

Dispersion of the thickness of the densified sol-gel coating is preferably lower than +/- 20 nm, more preferably lower than +/- 10 nm whatever the thickness. It allows advantageously not to significantly impact the optical properties of the underlying soft coating such as the color or reflection.

The presence of the densified sol-gel coating of the invention above a solar control or insulating low-E coating advantageously does not significantly impact the emissivity of the solar control or insulating low-E coating. It means that the emissivity measured according to EN 12898 without and with the densified sol-gel coating differs of at most 5%, preferably of at most 3%.

In a preferred embodiment of the present invention the ratio tSG/tDp+i of the optical thickness of the densified sol-gel coating tSG to the optical thickness of the soft coating’s last dielectric layer tDp+i in the sequence starting from the glass is comprised between 0.5 and 0.9 . The optical thickness of a layer or coating is its thickness multiplied by its refractive index at a wavelength of 550nm. It was found that densified coated glass substrates that respect this optical thickness ratio reach good mechanical and chemical durabilities without significantly changing the reflected and/or transmitted colors. In particular, any of the soft coatings in any of the following WO2005012200, WO2006122900, WO2007138097, WO2011147875, WO2011147864, WO2013079400, WO2014191472, WO2014191474, WO2014191484, or soft coatings of the Sunlux or Stopsol product range commercialized by Asahi Glass Company for example Silver Smart (such as 30/51/69), Planibel AS, iplustop (such as 1.1T, 1.0T, Stopray (Vision 50, 60, 72, 61, 41, and 40 and ultra 50 and 60 )) and Energy N also commercialized by Asahi Glass Company is modified so that the ratio of optical thickness of the densified sol-gel coating to the optical thickness of the soft coating’s last dielectric layer in the sequence starting from the glass is comprised between 0.5 and 0.9.

Contrarily to the disclosure of US20160194516, the present invention provides a protection of the soft coating after drying, but also after densification of the sol-gel solution; and for the lifetime of the densified coated substrate. After drying, the organic polymer and the partially or totally crosslinked precursors bring protection of the underlying soft coating. After densification, the organic polymer has mainly burnt, but the densified sol-gel coating protects the underlying soft coating.

The presence of the densified sol-gel coating above the soft coating advantageously brings a protection of the soft coating against mechanical, chemical and corrosion attacks. In other words, the densified coated substrate comprises a soft coating having improved mechanical, chemical and corrosion resistance thanks to the presence of the densified sol-gel coating. Particularly significant improvements are observed on soft coatings comprising at least one silver comprising layer, for instance one, two or three silver comprising layers.

These improved performances allow broadening the use of substrates bearing such soft coatings to applications where they are in contact with the environment, particularly when the coated substrate is a glass substrate and particularly when the soft coating is a solar control or insulating low-E coating produced by the PVD method.

The densified coated substrate of the invention has a particular interest in the field of glazing units. It is therefore another object of the present invention to provide glazing units comprising at least one densified coated glass substrate of the invention, wherein a face of the densified coated glass substrate provided with the soft coating and the densified sol-gel coating is facing the outside of the unit. They may for instance be used in simple glazing, or in multiple glazing in external position, i.e. on the external faces of the glazing, those facing the environment, particularly the environment of the inside of a building

The glazing unit may be a single glazing unit, i.e. a glazing unit comprising a single glass panel. In this case, the glass panel is a densified coated glass substrate according to the invention or a laminated glass comprising such densified coated glass substrate. In both cases, a face of the densified coated glass substrate provided with the soft coating and the densified sol-gel coating is facing the outside of the unit.

The glazing unit may be a multiple glazing unit. It is meant by multiple glazing unit a glazing unit comprising at least two glass panels separated by an interspace. It may for instance be a double glazing or a triple glazing. The interspace may be filled in with an insulating gas or the multiple glazing may be a vacuum insulating glazing. The glass panels of said multiple glazing units may be glass sheets or laminated glass or a combination of these. At least one glass panel of the multiple glazing is a densified coated glass substrate according to the invention or a laminated glass comprising such densified coated glass substrate. In both cases, a face of the densified coated glass substrate provided with the soft coating and the sol- gel coating is facing the outside of the unit.

The glazing units of the invention may be used for saving energy in applications such as buildings, transportation (automobile, bus, boat, train, tramway and the like) or greenhouses.

It is another object of the present invention to provide the use of at least one organic polymer in a sol-gel solution to coat a soft coating provided on a substrate, said soft coating comprising one or more layers deposited by physical vapor deposition. The invention more particularly provides the use of said organic polymer in a sol-gel solution to protect the soft coating.

All features and embodiments described above in relation with namely the substrate, the soft coating, the sol-gel solution, the dried sol-gel coating, the drying, the densification, the densified sol-gel coating, apply to the uses as well.

The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. It is further noted that the invention relates to all possible combinations of features, and preferred features, described herein and recited in the claims. Embodiments of the invention will now be further described by way of examples that are provided for illustrative purposes, and are not intended to limit the scope of this invention.

Preparation of Examples 1 and 2 and Comparative examples l to 4 A solution A is prepared by mixing at room temperature Aig of ethyl alcohol,

A2 g of acetylacetonate and A3g of titanium(IV) butoxide. A solution B is prepared by mixing at room temperature Big of ethyl alcohol, B2g of acetylacetone and B3 g of zirconium propoxide. A solution C is prepared by adding dropwise solution A in solution B at room temperature under stirring in 2 hours. A solution D is prepared by mixing Di g of ethyl alcohol, D2 g of tetraethylorthosilicate and D3 g of (3-glycidyloxypropyl)trimethoxysilane. D4 g of a solution of hydrochloric acid 0.1M is added to the solution D. D5 g of demineralized water is added to the solution D. Solution D is stirred at room temperature during 2 hours. Solution E is obtained by adding dropwise in 1 hour solution D to the solution C at room temperature under stirring . Final solution is obtained by addition of D6 g of Daotan® TW7000/40WA (polyurethane dispersion at 40wt% in water) to solution E under stirring 1 hour before application.

2 mL of the final solution are spin coated on a clean low-E coated glass substrate (Planibel AS 4 mm and Vision 40T 6 mm commercialized by Asahi Glass Company).

The drying conditions are: 150°C for 7 minutes under air.

The densification conditions are: under air atmosphere for 3.5 min at 070°C on

Planibel AS and 5 min at 070°C on Vision 40T.

Table i

Properties evaluation

The properties are evaluated according to the following methods:

Neutral salt spray according to ISO 9227-2012. Analysis and results according to EN 1096-2012:

The salt spray cabinet is an Elcometer 1120. The samples are rated from 1 to 5,

5 being not degraded, 1 being very degraded.

Climatic chamber (Weiss WK31000/40) with thermal cycles between 45°C and 55°C (heating from 45°C to 55 °C in 1 hour, cooling from 55°C to 45°C ini hour) and a relative humidity of 98%. The substrates after treatment in the climatic chamber are rated from 1 to 5, 5 being not degraded, 1 being very degraded.

Thickness and thickness dispersion of the dried or densified sol-gel coating has been measured using a Bruker DektakXT Stylus Profiler, with a 12,5 pm stylus.

In example 1, the thickness of the dried sol-gel coating is 195 nm while the thickness of the densified sol-gel coating is mnm. Table 2 : neutral salt spray results on dried coated substrates (Planibel AS 4 mm).

Samples Matrix composition 2 days 10 days

Ex.l Si(GPTMS)-Ti-Zr-Daotan >3.5 >3.5

Ex.2 Si(GPTMS)-Ti-Zr-Daotan >3.5 >3.5

Comp. Ex 1 Si(GPTMS)-Ti-Zr >3.5 <3.5

Comp. Ex 2 Si(TEOS)-Ti-Zr >3.5 <3.5

Comp. Ex 3 Si(GPTMS)-Ti-Zr >3.5 <3.5

Comp. Ex 4 Si(GPTMS)-Ti-Zr >3.5 <3.5

The dried coated substrates according to the invention in which the dried sol- gel coating comprises an organic polymer have an improved corrosion resistance after to days of exposure to a neutral salt spray in comparison to dried coated substrates where no organic polymer is present in the dried sol-gel coating. Table 3 : neutral salt spray results on densified coated substrates (Planibel AS 4 mm)

Samples Matrix composition 2 days 10 days Ex.l Si(GPTMS)-Ti-Zr-Daotan >3.5 >3.5

Ex.2 Si(GPTMS)-Ti-Zr-Daotan >3.5 >3.5

Comp. Ex 1 Si(GPTMS)-Ti-Zr >3.5 >3.5

Comp. Ex 2 Si(TEOS)-Ti-Zr >3.5 >3.5

Comp. Ex 3 Si(GPTMS)-Ti-Zr >3.5 >3.5

Comp. Ex 4 Si(GPTMS)-Ti-Zr >3.5 >3.5

The densified coated substrates according to the invention have similar corrosion resistance after 2 and to days of exposure to a neutral salt spray in comparison to densified coated substrates where no organic polymer was present in the dried sol-gel coating. In the examples according to the invention, the organic polymer has been totally or almost totally thermally degraded during the densification step. The degradation of the organic polymer during the densification step does not negatively impact the protection performances of the densified sol-gel coating.

Table 4 : climatic chamber results on dried coated substrates (Planibel AS 4 mm)

Samples Matrix composition 2 days 10 days

Ex.l Si(GPTMS)-Ti-Zr-Daotan >3.5 >3.5

Ex.2 Si(GPTMS)-Ti-Zr-Daotan >3.5 >3.5

Comp. Ex 1 Si(GPTMS)-Ti-Zr >3.5 <3.5

Comp. Ex 2 Si(TEOS)-Ti-Zr >3.5 <3.5

Comp. Ex 3 Si(GPTMS)-Ti-Zr >3.5 <3.5

Comp. Ex 4 Si(GPTMS)-Ti-Zr >3.5 <3.5

The dried coated substrates according to the invention in which the dried sol- gel coating comprises an organic polymer have an improved corrosion resistance after 10 days of exposure to a neutral salt spray in comparison to dried coated substrates where no organic polymer is present in the dried sol-gel coating. Table 5 : climatic chamber results on densified coated substrates (Planibel AS 4 mm)

Samples Matrix composition 2 days 10 days Ex.l Si(GPTMS)-Ti-Zr-Daotan >3.5 >3.5

Ex.2 Si(GPTMS)-Ti-Zr-Daotan >3.5 >3.5

Comp. Ex 1 Si(GPTMS)-Ti-Zr >3.5 >3.5

Comp. Ex 2 Si(TEOS)-Ti-Zr >3.5 >3.5

Comp. Ex 3 Si(GPTMS)-Ti-Zr >3.5 >3.5

Comp. Ex 4 Si(GPTMS)-Ti-Zr >3.5 >3.5

Examples l and 2 are reproduced, but the final sol-gel solutions are applied on a V40T and a Planibel AS substrates by Electrospray deposition. Process parameters are adapted to obtain a dried sol-gel coating thickness of 180 nm. After densification, the densified sol-gel coating thickness is 120 nm and the dispersion of the densified sol-gel thicknesses is +/- 8 nm.

Claims

CLAIMS l. A dried coated substrate comprising:

a substrate,

at least one organic polymer and

at least one silicon oxide precursor and

at least one oxide precursor of titanium or zirconium.

2. A dried coated substrate according to claim l, wherein the sol-gel solution is characterized by the following weight ratios:

organic polymer weight/ silicon oxide precursor weight ranging from o.io to 3,

titanium oxide precursor weight / silicon oxide precursor weight ranging from o.io to 3, and/or

zirconium oxide precursor weight / silicon oxide precursor weight ranging from 0.10 to 3,

and wherein the metal or metalloid oxide precursor weights are expressed as metal or metalloid oxide theoretical weights.

3 Dried coated substrate according to claim 1 or 2, wherein the substrate is a glass substrate.

4. Dried coated substrate according to any of the preceding claims, wherein the sol-gel solution comprises at least one organic polymer, at least one silicon oxide precursor, at least one titanium oxide precursor and at least one zirconium oxide precursor.

5. Dried coated substrate according to any of the preceding claims, wherein the organic polymer is a linear or branched synthetic polymer having a weight average molecular weight of at least 200 Daltons and a Tg of at least 25°C.

6. Dried coated substrate according to any of the preceding claims, wherein the soft coating is a solar control or insulating low-E coating.

7. Dried coated substrate according to any of the preceding claims, wherein the dried sol-gel coating is provided on at least a part of the face of the substrate provided with the soft coating and in direct contact with the soft coating.

8. Dried coated substrate according to any of the preceding claims, wherein the sol-gel coating is provided at least substantially on the entire soft coating and in direct contact with the soft coating.

9. Process for making a coated substrate comprising the steps of:

a) forming a soft coating comprising one or more layers deposited by physical vapor deposition on at least a part of at least one face of a substrate,

- at least one organic polymer and

- at least one silicon oxide precursor and

- at least one oxide precursor of titanium or zirconium, c) drying the sol-gel solution to obtain a dried sol-gel coating. to. Process according to the preceding claim, wherein the sol-gel solution is applied by an application method selected from electrospray deposition, ultrasonic deposition and inkjet printing. n. Process according to any of claim 10 or n, comprising a subsequent step of densification of the dried sol-gel coating to obtain a densified sol-gel coating.

12. Process according to claim n, wherein the substrate is a glass substrate.

13. Process according to the preceding claim, wherein the step of densification is a tempering step.

14. Densified coated glass substrate obtained by the process of any of claims

12 to 13.

15. Densified coated glass substrate according to the preceding claim wherein the ratio tso/t_Dp+i of the optical thickness of the densified sol-gel coating tso to the optical thickness of the soft coating’s last dielectric layer t_Dp+i in the sequence starting from the glass is comprised between 0.5 and 0.9.

16. Glazing unit comprising at least one densified coated glass substrate according to claim 14 or 15, wherein a face of the densified coated glass substrate provided with the soft coating and the densified sol-gel coating is facing the outside of the unit.

17. Glazing unit according to claim 16, wherein the glazing unit is a single glazing unit comprising one glass panel.

18. Glazing unit according to claim 16, wherein the glazing unit is a multiple glazing unit comprising at least two glass panels separated by an interspace. 19. Use of at least one organic polymer in a sol-gel solution comprising: at least one organic polymer and

at least one silicon oxide precursor and

at least one oxide precursor of titanium or zirconium,

to coat a soft coating provided on a substrate, said soft coating comprising one or more layers deposited by physical vapor deposition.

20. Use according to claim 19, to protect the soft coating.