Substrate with photocatalytic coating

(54) Title * Substrate based on glass, ceramics or vldro-ceramics, anti-soiling and / or anti-curving, monolithic, multiple glazing, application of substrate and process of obtaining substrate.

(30) Unionist priority. 15/09 / 1995FR 95/10839 (7t), Deposter (s): Saint-Gobam Vltrage (FR) (72) Inventors): PhilippeBoire, Xavier Talpaert (74) Attorney: Momsen, Leonardos & Cia.

(86) International Order * pct fr 96 / oi42i of 13/09/1996 (87) International Publication: WO 97/10186 of 20/03/1997 (57) Abstract: substrate The base of glass, ceramic OR GLASS CERAMIC , ANTI-DIRTY AND / OR ANTITURVATION GLASS, MONOLITHIC. MULTIPLE. APPLICATION OF THE SUBSTRATE AND PROCESS OF OBTAINING THE SUBSTRATE The objective of the Invention is a substrate (1) based on glass, ceramics or glass-ceramic provided on at least a part of at least one of its sides of a coating (3) with fatocatallitic properties that stain the titanium oxide at least paraally crystallized. It also refers to the applications of such a substrate and how it is obtained

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GLASS, CERAMIC OR GLASS-BASED SUBSTRATE, ANTI-DIRTY GLASS AND / OR «: ANT ^] ^ | \ AÇA ^ 't: MONOLITHIC, MULTIPLE, SUBSTRATE APPLICATION' AND * SUBSTRATE OBTAINING PROCESS.

The invention relates to substrates based on glass, ceramics or glass-ceramics, more particularly glass, especially transparent, to which coatings with photocatalytic properties are applied, to manufacture glazing for various applications, such as utility glazing, glazing for vehicles or buildings.

Increasingly, it is sought to functionalize the glazing by placing thin layers on its surface to give it a particular property according to the intended application. Thus, there are layers with an optical function, such as layers called anti-glare composed of a pile of layers alternatively with high and low refractive indices. For an anti-static function, or an anti-heat type heating, thin electrically conductive layers can also be provided, for example based on metal or activated metal oxide. For a thermal, low-emissivity or anti-solar function, for example, thin layers of silver-type metal or based on nitride or metal oxide can be chosen. To obtain an anti-rain effect, layers of a hydrophobic character can be provided, for example, based on fluorinated organo-silane ...

However, there is still a need for a substrate, especially a glazing that could be classified as anti-dirt, that is, it aims at the permanence of the aspect and surface properties over time and that allows especially to clean and / or improve cleaning visibility, gradually eliminating the dirt that is gradually deposited on the surface of the substrate, especially dirt of organic origin, such as traces of fingers or volatile organic products present in the atmosphere, or even turbidity.

Now, it is known that there are certain metal oxide materials, which are capable, under the effect of radiation of an appropriate wavelength, to initiate radical reactions that cause the oxidation of organic products: they are in general photocatalytic materials or still photoreactive¹'.

The invention then aims to adapt photocatalytic coatings on substrate, which have a marked anti-dust effect in relation to the substrate that can be manufactured in an industrial way.

The invention aims at a substrate based on glass, ceramics or glass-ceramics, especially glass and transparent, provided on at least part of at least one of its faces with a photocatalytic coating that involves titanium oxide at least partially crystallized. Titanium oxide is preferably crystallized in situ when the coating is formed on the substrate.

Titanium oxide is in fact part of the semiconductors that, under the action of light in the visible or ultraviolet domain, degrade organic products that decompose on their surface. Choosing titanium oxide to manufacture a glazing with an anti-dirt effect is therefore particularly suitable and this all the more so since this oxide has good mechanical and chemical resistance: in order to be effective for a long time, it is obviously important that the coating preserves its integrity, even if it is directly exposed to numerous attacks, especially when the window is assembled on the construction site (building construction) or on the production line (vehicle) ), which implies repeated manipulation by mechanical or pneumatic gripping means and also once the window is in place with risks of abrasion (windshield wiper, abrasive cloth) and contact with aggressive chemicals (SO type air pollutants)₂, cleaning product,...). 5J $ “! ΐ 5

The choice was also made for a titanium oxide that is at least partially crystallized because it has been shown to be much more functional in terms of photocatalytic property than amorphous titanium oxide. Preferably, it is crystallized in the form of anatase, in the form of rutile or in the form of a mixture of anatase and rutile, with a crystallization rate of at least 25%, especially approximately 30 to 80%, especially near the surface , (the property being preferably a surface property). (Crystallization rate means the amount by weight of TiO₂ crystallized from the total weight of TiO₂ coating).

It can also be observed, especially in the case of crystallization in the form of anatase, that the orientation of the TiO crystals₂ growing on the substrate had an influence on the photocatalytic performances of the oxide: there is a privileged orientation (1,1.00 that clearly favors photocatalysis.

Advantageously, the fabrication of the coating is carried out in such a way that the crystallized titanium oxide it contains is in the form of crystallites, at least close to the surface, that is to say, single crystals, which have an average size between 0.5 and 100 nm , preferably 1 at 50 nm, especially 10 at 40 nm, more particularly between 20 and 30 nm. It is in effect in this dimension range that titanium oxide appears to have an optimal photocatalytic effect, truly because crystallites of this size develop a large active surface.

As will be seen in more detail later, the titanium oxide coating can be obtained in multiple ways:

□ by decomposition of titanium precursors (pyrolysis techniques: liquid pyrolysis, powder pyrolysis, steam phase pyrolysis called CVD (Chemical Vapor Deposition), techniques associated with sol-gel: immersed or dipping, cell-coating, ...) , p: s · * 5: «

Ί 0 00 0 ··· 0 0 0 □ using a vacuum technique (reactive or non-reactive sputtering).

The coating may also involve, in addition to crystallized titanium oxide, at least one other type of mineral material, especially in the form of an amorphous or partially crystallized oxide, for example, a silicon oxide (or mixture of oxides), of titanium, tin, zirconium or aluminum. This mineral material can also participate in the photocatalytic effect of crystallized titanium oxide, presenting itself a certain photocatalytic effect, even weak in relation to that of TiO₂ crystallized, which is the case for tin oxide or amorphous titanium oxide.

A mixed oxide layer that thus combines at least partially crystallized titanium oxide with at least one other oxide may be interesting in the optical plane, particularly if the other or the other oxides are chosen with a lower index than TiO₂: by lowering the overall refractive index of the coating, the luminous reflection of the substrate provided with the coating can be varied, especially lowering this reflection. This is the case if, for example, a layer of TiO is chosen₂ / TO 1₂O₃, of which a method of obtaining it is described in patent EP-0.465.309 or TiO₂ / SiO₂. It is, of course, necessary that the coating in the meantime contains a content of TiO₂ enough to conserve remarkable photocatalytic activity. Thus, it is considered that it is preferable that the coating contains at least 40% by weight, especially at least 50% by weight of TiO₂ in relation to the total weight of oxide (s) in the coating.

It is also possible to choose to superimpose on the coating according to the invention a oleophobic and / or hydrophobic layer grafted that is stable or resistant to photocatalysis, for example, based on the fluorinated organo-silane described in US-5,368,892 and US-5,389. 427, as well as perfluoroalkylsilane described in patent application sÇf0 „· July 1994 published under number FR-2,722,493 and corresponding to the European patent EP-0.692,463, especially of formula:

CF₃- (CF₂)_n- (CH₂)_m-SiX₃ in which néde0al2, méde2a5eXis a hydrolyzable group.

In order to amplify the photocatalytic effect of the titanium oxide of the coating according to the invention, it is possible, in principle, to increase the absorption range of the coating, incorporating into the coating other particles especially metallic and based on cadmium, tin, tungsten, zinc, cerium or zirconium.

You can also increase the number of charge carriers by activating the titanium oxide crystalline network, inserting at least one of the following metallic elements: niobium, tantalum, iron, bismuth, cobalt, nickel, copper, ruthenium, cerium, molybdenum.

This activation can also be done by activating the surface only of titanium oxide or the coating as a whole, activating the surface by covering at least part of the coating with a layer of oxides or metal salts, the metal being chosen from the iron , copper, ruthenium, cerium, molybdenum, vanadium and bismuth.

Finally, the photocatalytic phenomenon can be amplified by increasing the yield and / or the kinetics of the photocatalytic reactions, covering the titanium oxide or at least part of the coating that incorporates it, with a noble metal in the form of a thin layer of the platinum type, rhodium, silver, palladium.

Such a catalyst, for example, deposited by a vacuum technique, actually allows to increase the number and / or the life span of the radical entities created by titanium oxide and thus favor the chain reactions that lead to the degradation of organic products.

In a totally surprising way, ^:* £&gt; · * fívf ^ ttspííjt • «· · ·· · · · · in fact presents not one property but two, as soon as it is exposed to adequate radiation as in the domain of the visible and / or the ultraviolet, such as one solar radiation: by the presence of photocatalytic titanium oxide, as already seen, it favors the progressive disappearance, during its accumulation, of dirt of organic origin, causing its degradation by a process of radical oxidation. Mineral soils are not themselves degraded by this process: they therefore remain on the surface, and, alongside certain crystallizations, they are partly easily evacuated as they have no reason to adhere to the surface, the sticky organic agents being degraded by photocatalysis.

However, the coating of the invention, which is permanently self-cleaning, also preferably has an external surface of a marked hydrophilic and / or oleophilic character, which induces three very advantageous effects:

□ a hydrophilic character allows perfect wetting of the water that can be deposited on the coating. When a phenomenon of water condensation occurs, instead of a deposit of droplets of water in the form of turbidity that hinders visibility, a thin continuous film of water is formed that forms on the surface of the coating and is completely transparent. This anti-turbidity effect is especially demonstrated by measuring an angle of contact with water below 5 ° after exposure to light, and,

Π after dripping water, especially from rain, on a surface not treated by a photocatalytic layer, numerous drops of rain water remain attached to the surface and leave, once evaporated, unsightly and uncomfortable traces, mainly of mineral origin. In effect, a surface exposed to ambient air quickly covers up with a layer of dirt that limits its wetting by water. To these soils are added other soilsSjíIêspefWmeate.

* · · · »· · Aa · minerals (crystallizations, ...) brought by the atmosphere in which the glass is bathed. In the case of a photoreactive surface, these mineral soils are not directly degraded by photocatalysis. In fact, they are largely eliminated thanks to the hydrophilic character induced by the photocatalytic activity. This hydrophilic character actually causes the raindrops to be perfectly spread. Therefore, traces of evaporation are no longer present. In addition, the other mineral soils present on the surface are washed or redissolved in the case of crystallization, by the water film and therefore largely evacuated. A mineral anti-dirt effect, especially induced by rain, is obtained.

□ together with a hydrophilic character, the coating may also have an oleophilic character, which allows the wetting of organic soils, which, as for water, then tend to settle on the coating in the form of a continuous film less visible than well-located stains . This results in an organic anti-dirt effect that operates in two stages: as soon as it settles on the coating, the dirt is barely visible. Then, progressively, it disappears due to radical degradation initiated by photocatalysis.

The coating can be chosen from a more or less smooth surface. A certain roughness can also be advantageous:

□ it allows to reveal a larger active photocatalytic surface and therefore it induces greater photocatalytic activity, □ it has a direct influence on wetting. The roughness actually exalts the wetting properties. A smooth hydrophilic surface will be even more hydrophilic once it has been roughened. Here, roughness is understood as well as surface roughness, as the roughness induced by a porosity of the layer in at least part of its thickness.

The previous effects will be as much afcerituáckjs íçpçÍpícj

The «·····» «· · ··» · »· · · · coating is porous and rough, hence a super-hydrophilic effect of rough photoreactive surfaces. However, very accentuated, the roughness can be penalizing favoring the fouling, the accumulation of dirt and / or causing a level of lack of sharpness optically unacceptable.

It was thus interesting to adapt the deposition mode of TiO-based coatings₂ so that they had a roughness of approximately 2 to 20 nm, preferably from 5 to 15 nm, this roughness being evaluated by microscopy with atomic force, by measuring the value of the mean square deviation (called Root Mean Square ”or RMS in English ) on a surface of 1 square micrometer. With such roughness, the tiles have a hydrophilic character which translates into an angle of contact with water that can be less than 1 °. It was also found that it was advantageous to favor a certain porosity in the thickness of the coating. Thus, if the coating consists only of TiO₂, it preferably presents a porosity of the order of 65 to 99%, especially 70 to 90%, the porosity being defined here indirectly by the percentage of theoretical density of TiO₂, which is approximately 3.8. In order to favor such porosity, a means consists, for example, in depositing the coating using a sol-gel technique, which involves the decomposition of organo-metallic materials: it can then be introduced into the solution, in addition to or (s) organometallic precursor (s), an organic polymer of the type polyethylene glycol PEG: by hardening the layer by heating, the PEG is burned, which generates or amplifies a certain porosity in the layer thickness.

The thickness of the coating according to the invention is variable, it is preferably between 5 nm and 1 micron, especially between 5 and 100 nm, especially between 10 and 80 nm or between 20 and 50 nm. In fact, the choice of thickness may depend on different parameters, especially on the target application of the system; s.&gt; v ·. · vv:

or the size of TiO crystallites₂ in the coating or the presence of alkalis in strong proportion in the substrate.

Between the substrate and the coating according to the invention, one or more other thin layers can be arranged with a different or complementary function to that of the coating. It can be specially treated with layers with anti-static, thermal, optical function or that favor the crystalline growth of TiO₂ in the form of anatase or rutile or layers that serve as a barrier to the migration of certain elements from the substrate, especially as a barrier to alkalis and particularly sodium ions when the substrate is glass.

It is also possible to target a pile of anti-reflective layers ”alternating thin layers with high and low indexes, the coating according to the invention constituting the last layer of the pile. In this case, it is preferable that the coating has a relatively low refractive index, which is the case when it consists of a mixed oxide of titanium and silicon.

The layer with anti-static and or thermal function (heater providing it with current arrivals, low-emission, anti-solar, ...) can be specially chosen based on a conductive material of the metal type, such as silver or of the activated metal oxide type such as ITO tin-activated indium oxide, the tin oxide activated with a fluorine-type halogen SnO₂: F or with SnO antimony₂: Sb or zinc oxide activated with ZnO indium: In with fluorine ZnO: F, with aluminum ZnO: Al or with tin ZnO: Sn. One can also treat metal oxides under stoichiometric in oxygen, such as SnO₂._x or ZnO_2x with x &lt;2.

The layer with anti-static function preferably has a square resistance value of 20 to 1000 obms / square. It can be foreseen to provide it with current arrivals in order to polarize it (supply voltages for example comprised between 5 and 100V). This cpôladâ.

:: .l · ·. · v ·. · vt makes it possible to specially fight against the deposit of dust of the size of the millimeter susceptible to be deposited on the coating, especially dry dust adhering only by electrostatic effect: brutally inverting the polarization of the layer , this dust is ejected.

The thin layer with optical function can be chosen in order to reduce the luminous reflection and / or make the substrate reflection color more neutral. In this case, it preferably has an intermediate refractive index between that of the coating and that of the substrate and an appropriate optical thickness and may consist of an oxide or a mixture of oxides of the type aluminum oxide Al₂O₃, SnO tin oxide₂, indium oxide In₂O₃, silicon oxycarbonate or oxynitride. To obtain a maximum attenuation of the reflection color, it is preferable that this thin layer has a refractive index close to the square root of the product of the squares of the refractive indices of the two materials that surround it, that is, the substrate and the coating according to the invention. In parallel, it is advantageous to choose its optical thickness (that is, the product of its geometric thickness and its refractive index) close to lambda / 4, lambda being approximately the average wavelength in the visible, especially from approximately 500 to 550 nm.

The thin layer with alkaline barrier function can be specially chosen based on oxide, nitride, oxynitride or silicon oxycarbonide, in aluminum oxide containing fluorine A1₂O₃: F, or in aluminum nitride. In fact, it has been found to be useful when the substrate is glass, since the migration of sodium ions in the coating according to the invention can, under certain conditions, alter the photocatalytic properties.

The nature of the substrate or the sub-layer is also of additional interest: it may favor the crystallization of the photocatalytic layer that is deposited, especially in the case of the CVD deposit.

Thus, when deposited by CKflS dèg líOj, aSjqã jijtí- (: .. · ·. · ·. · ·. · ·. ·:

SnO layer₂; F crystallized favors the growth of TiO₂ in a mostly rutile form, especially for deposition temperatures in the range of 400 ° to 500 ° C, whereas the surface of a soda-lime glass or silicon oxycarbonide sub-layer preferably induces anatase growth, especially for deposit temperatures on the order of 400 ° to 600 ° C.

All of these optional thin layers can, in a known manner, be deposited by vacuum sputtering techniques or by other thermal decomposition techniques such as solid, liquid or gaseous pyrolysis. Each of the aforementioned layers can accumulate several functions, but you can also overlap them.

The invention also aims at anti-dust panes (organic and / or mineral soils) and / or anti-turbidity, whether they are monolithic, multiple insulators of the double pane type or veneered and which incorporate the coated substrates described above.

The invention therefore aims at the manufacture of glass, ceramic or glass-ceramic products and particularly the manufacture of self-cleaning panes. These can advantageously be building glazing, such as double glazing (the cladding can then be arranged on the outside and / or inside, that is to say on face 1 and / or face 4). This is particularly interesting for glazing that is not easily accessible and / or that needs to be cleaned very frequently, such as roof glazing, airport glazing, ... Glazing for vehicles in which maintenance is also possible. visibility is an essential safety criterion. This coating can thus be placed on windshields, side or rear windows of cars, especially on the face of the glass panes facing the interior of the passenger compartment. This coating can then prevent the formation of turbidity and / or suppress traces of dirt such as fl 4 β I β II * * * * fl from fingers, nicotine or organic material from the fipcí jA4 ^ í # í | aiiÇB: Ydl &amp; fií fogged by the plastic that lines the interior of the passenger compartment, especially the dashboard (fogging sometimes known by the English term fogging (turbidity formation)). Other vehicles such as airplanes or trains may also find interest in using panes provided with the coating of the invention.

Numerous other applications are possible, especially for aquarium glass, store windows, greenhouses, balconies, glass used in indoor or urban furniture, but also mirrors, television screens, mastery of glasses sales or any architectural material of the type facade, framing, roofing material such as tiles, ...

The invention thus makes it possible to functionalize these known products, giving them anti-ultraviolet, anti-dirt, bactericidal, anti-reflective, anti-static, anti-microorganism, properties ...

Another interesting application of the coating according to the invention consists of associating an electrically controlled variable absorption pane of the electrochrome pane type, pane with liquid crystals possibly with dichroic coloring, pane with suspended particle system, viologenic pane ... All these glazing being constituted in general of a plurality of transparent substrates between which active elements are arranged, the coating can then be advantageously arranged on the outer face of at least one of these substrates.

Especially in the case of an electrochromic glazing, when the latter is in the colored state, its absorption leads to a certain heating on the surface, which, in fact, is likely to accelerate the photocatalytic decomposition of the carbonated substances that are deposited on the coating accordingly. with the invention, for more details on the • a · · ·· · · · · · structure of an electrochrome pane, Meal will be made \ iantajbáaKêfà4 â &lt;5 ϊ s · '··· * · · · patent application EP-A-0.575.207 which describes an electrochrome chrome double glazing, the coating according to the invention and may preferably be face 1.

The invention also aims at the different processes for obtaining the coating according to the invention. A pyrolysis type deposition technique can be used, which is interesting because it allows the deposit of the coating to be continuously deposited directly on the float glass strip when using a glass substrate.

Pyrolysis can be carried out in solid phase, from organo-metallic precursor powder (s).

Pyrolysis can be carried out in a liquid phase, from a solution comprising an organo-metallic titanium precursor of the titanium chelate type and / or titanium alcoholate. Such precursors are mixed with at least one other organo-metallic precursor. For more details on the nature of the titanium precursor or on the deposit conditions, we will refer, for example, to patents FR-2,310,977 and EP-0.465,309.

Pyrolysis can also be carried out in the vapor phase, a technique that is also called by the term CVD (Chemical Vapor Deposition), from at least one titanium precursor of the halide type such as TiCl₄ or Ti, Ti tetraisopropylate titanium alcoholate (OiPr)₄. Crystallization of the layer can also be controlled by the type of sublayer, as previously mentioned.

It is also possible to deposit the coating by other techniques, especially by techniques associated with sol-gel. Different deposit modes are possible as immersion also called dipcoating¹'(immersion coating) or a deposit with the help of a cell called cell-coating. It can also be a spray-coating or laminar coating deposit, detailed in patent application WO-94/01598. All these deposit modes generally use a solution that comprises at least one organo-metallic precursor, especially of titanium of the alcoholic type, which decomposes thermally after covering the substrate by the solution on one of its faces or on its two faces.

In fact, it may be interesting to deposit the coating, regardless of the deposition technique considered, not just once, but at least for two successive stages, which seems to favor the crystallization of titanium oxide over the entire thickness of the coating when you choose the relatively thick one.

In the same way, it is advantageous to make the coating that has photocatalytic property, after deposit, undergo a heat treatment of the annealed type. A heat treatment is essential for a sol-gel or laminar coating technique in order to decompose the organo-metallic precursor (s) of oxide, once the substrate is coated and the resistance to abrasion, which is not the case when using a pyrolysis technique in which the precursor decomposes as soon as it is in contact with the substrate. In the first case as in the second, however, a post-deposit heat treatment, once TiO is formed_2simproves its crystallization rate. The treatment temperature chosen may also allow better control of the crystallization rate and the crystalline nature, anatase and / or rutile of the oxide.

However, in the case of a soda-lime glass substrate, multiple and prolonged annealing can favor an attenuation of the photocatalytic activity due to an excessively large migration of the substrate's alkalis towards the photoreactive layer. The use of a barrier layer between the substrate, if it is made of standardized glass and the coating, or the choice of a glass substrate of appropriate composition *, ·, or the choice of soda-cal and cu | 4 • · glass »De-alkalized, allows you to get rid of this risk.

Further details and advantageous features of the invention are highlighted in the following description of examples of non-limiting realization, with the help of the following figures:

- figure 1: a cross-section of a glass substrate provided with the coating according to the invention,

- figure 2: a scheme of a sol-gel deposit technique, called by immersion or dip-coating of the coating,

- figure 3: a scheme of a deposit technique called cell-coating,

- figure 4: a scheme of a deposition technique called spray-coating,

- figure 5: a schematic of a laminar coating deposit technique.

As shown in an extremely schematic way in figure 1, all the following examples refer to the deposition of a coating 3 called anti-dirt essentially based on titanium oxide on a transparent substrate 1.

Substrate 1 is 4 mm thick, 50 cm long and wide silica-soda-lime clear glass. It follows that the invention is not limited to this specific type of glass. The glass may also not be flat, but arched.

Between the coating 3 and the substrate 1, there is an optional thin layer 2, based on silicon oxycarbonate, which represents SiOC to constitute a barrier against diffusion to alkalis and / or a attenuating layer of light reflection, either based on oxide of fluorine-activated tin SnO₂: F to form an anti-static and / or low-emission layer, even with a low accentuated low-emissive effect, and / or that attenuates the color «« especially in reflection. ?^! The ·* · .

• b · β · “·. · B - ada 'aad« aa. * hello

EXAMPLES 1A3

Examples 1 to 3 refer to a coating 3 deposited with the aid of a liquid phase pyrolysis technique. You can proceed continuously, using an adapted distribution nozzle disposed transversely and above the float glass tape, when leaving the enclosure of the float bath itself. Here, we proceeded in a discontinuous way, using a movable nozzle arranged in front of the substrate 1 already cut in the indicated dimensions, substrate that is initially heated in an oven at a temperature of 400 to 650 ° C before going at constant speed in front of the nozzle designing an appropriate solution.

EXAMPLE 1

In this example, there is no optional layer 2. The coating 3 is deposited with the help of a solution comprising two organo-metallic titanium precursors, titanium diisopropyl di acetylacetonate and titanium tetraoctylene glycolate dissolved in a mixture of two solvents, which are ethyl acetate and isopropanol.

It can be seen that other precursors of the same type are also fully usable, especially other titanium chelates of the type titanium acetylacetonate, titanium methylacetoacetate, titanium ethylacetoacetate or even the titanium tri-ethanol amine or the titanium diethanol amine.

As soon as substrate 1 has reached the desired temperature in the oven, especially around 500 ° C, it passes in front of the nozzle that projects the indicated mixture at room temperature with the help of compressed air.

A layer of TiO is then obtained₂ approximately 90 nm thick, the thickness can be controlled by the speed of passage of the substrate 1 in front of the nozzle and / or the temperature of said substrate.

3· · · ·* _TheS ·· · a

The layer is partially crystallized in anatase form .: '·· · *: · ::: ·. ::: .j

This layer has excellent mechanical behavior. Its resistance to abrasion tests is comparable to that obtained for the bare glass surface.

It is arable and waterlogged. It does not have a veil: the diffuse light transmission of the coated substrate is less than 0.6% (measured according to illuminant D₆₅ at 560 nm).

EXAMPLE 2

This renews example 1, but with a layer 2 in SnO between the substrate 1 and the coating 3₂: 73 nm thick F. This layer is obtained by powder pyrolysis from dibutyl tin difluoride DBTF. It can also be obtained, in a known way, by pyrolysis in liquid or vapor phase, as for example is described in patent application EP-A0.648.196. In the steam phase, a mixture of tin mono butyl trichloride and a fluorinated precursor, possibly associated with a mild H₂O.

The layer index obtained is approximately 1.9. Its square resistance is approximately 50 ohms.

In the previous example 1, the coated substrate 1, mounted in double glazing so that the coating is on the face 1 (with another Γ uncoated substrate but of the same nature and dimensions as the substrate 1 by means of an air blade of 12 mm) has a reflection color purity value of 26% and a transmission color purity value of 6.8%.

In this example 2, the color purity in reflection (in gold) is not more than 3.6% and it is 1.1% in transmission.

Thus, the SnO sub-layer₂: F allows to give the substrate anti-static properties that are a consequence of its electrical conductivity, it also has a favorable influence on the colorimetry of the substrate, making its sol $ râdã} J, iftoi bémidrâ considerably more neutral:

• · · · · · · ·. · ·. · · Transmission when reflective, coloration caused by the presence of the titanium oxide coating 3 which has a relatively high refractive index. It can be polarized by providing it with an adapted electrical supply, to limit the deposit of dust of relatively large size in the order of millimeter.

In addition, this sub-layer decreases the diffusion of alkali in the photocatalytic layer of TiO₂. The photocatalytic activity is therefore improved.

EXAMPLE 3

He renews example 2, but this time by inserting a layer 2 of silicon oxycarbonate between the substrate 1 and the coating 3, with an index of approximately 1.75 and a thickness of approximately 50 nm, a layer that can be obtained by CVD from of a mixture of S1H4 and ethylene diluted in nitrogen, as described in patent application EP-A0.518.755. This layer is particularly effective in preventing the tendency to diffuse alkali (Na, K) and alkaline earth (Ca) from substrate 1 to coating 3 and whose photocatalytic activity is markedly improved. Having, as SnO₂: F, an intermediate refractive index between that of the substrate (1.52) and that of coating 3 (approximately 2.30 to 2.35), it also attenuates the intensity of the substrate's coloration as well in reflection as in transmission and overall decrease the light reflection value R_L of said substrate.

Examples 4 to 7 below refer to CVD deposits. EXAMPLES 4 TO 7

EXAMPLE 4

This example refers to depositing pro CVD of coating 3 directly onto substrate 1, with the aid of a standardized nozzle such as that represented in patent application EP-A-0.518.755 mentioned above. As precursors, it is used either an organometáliêd, fcej.4 Jlp5 hàfqgpnê &amp;: metallic. Here, titanium tetraisopropylate is chosen as organometallic, which is interesting for its high volatility and wide range of temperatures of use, from 300 to 650 ° C. The deposit is made in this example at approximately 425 ° C, the thickness of TiO₂ is 15 nm.

Ti (O-Et) titanium tetrahydroxy₄ it can also suit and as halide we can quote TiCl₄.

EXAMPLES

This is done similarly to example 4, except that the 15 nm layer of TiO is deposited₂ not directly on the glass, but on a 50 nm SiOC sub-layer deposited as in the example

3.

EXAMPLE 6

This is done as in example 4, except that here the thickness of the TiO layer₂ is 65 nm.

EXAMPLE 7

This is done as in example 5, except that here the thickness of the TiO layer₂ is 60 nm.

From these examples 4 to 7, it appears that the substrates thus coated have a good mechanical resistance to abrasion tests. In particular, there is no delamination of the TiO layer₂.

EXAMPLE 8

This example uses a technique associated with the sol-gel that uses a dip-deposit mode also called dip coating whose principle is shown in figure 2: it is a matter of immersing the substrate 1 in the liquid solution 4 containing the appropriate precursor (s) of the coating 3, after extracting the substrate 1 at a controlled speed with the help of a motor medium 5, the choice of the extraction speed allowing to adjust the thickness of solution that remains on the surface of the two faces of the substrate and, in fact, the thickness of the coatings $ fòs £ àípOsitadós, *. ãg &lt;S &amp; heat treatment of the latter to simultaneously evaporate the solvent and decompose the oxide precursor (s).

A solution 4 comprising Ti titanium tetrabutoxide (O-Bu) is used to deposit coating 3₄ stabilized with diethanol amine DEA in a 1: 1 molar ratio in an ethanol-type solvent to 0.2 mol of tetrabutoxide per liter of ethanol, either the mixture of precursors and solvents described in example 1. (Another precursor may also be used such as titanium dibutoxy-diethanolamine).

Substrates 1 may involve SiOC sub-layers.

After extracting each of the solutions 4, the substrates 1 are heated 1 hour at 100 ° C then approximately 3 hours at 550 ° C with a progressive rise in temperature.

A coating 3 is obtained on each side, in both cases in TiO₂ well crystallized in anatase form.

EXAMPLE 9

This example uses the technique called cell-coating, the principle of which is remembered in figure 3. It consists of forming a narrow cavity bounded by two substantially parallel faces 6,7 and two joints 8,9, at least one of these faces 6,7 being consisting of the face of the substrate 1 to be treated. Then the cavity of the precursor solution 4 (s) of the coating is filled, and the solution 4 is removed in a controlled manner, so as to form a wetting meniscus with the help of a peristaltic pump 10, for example, leaving a film of solution 4 on the substrate face during solution retraction.

The cavity 5 is then maintained for at least the time necessary for drying. The film is hardened by heat treatment. The advantage of this technique in relation to dip-coating is that it is possible to treat only one of the two faces of substrate 1, and not both systematically, unless recofrèr · a »_:^:i} fn: sisfexii £ E: (fc:

• · ·· ... , ·,· ·_β· Masking.

Substrates 1 involving thin layers 2 based on SiOC silicon oxycarbonate.

Example 6 uses the solutions 4 described in example 8 respectively. The same heat treatments are then operated to obtain the TiO coating 3₂.

The coating 3 has good mechanical durability.

The MEB (scanning electron microscope) looks like a field effect in the form of single crystal grains with a diameter of approximately 30 nm. The roughness of this coating induces exalted wetting properties compared to a non-rough coating.

These same solutions 4 can also be used to deposit spray-coating coatings, as shown in figure 4, in which solution 4 is sprayed in the form of a cloud against the substrate 1 in static or by laminar coating as shown in figure 5. In the latter case, substrate 1, held by vacuum suction, is passed against a support 11 in stainless steel and Teflon above a reservoir 12 containing the solution, a solution in which a split cylinder 14 is partially immersed, moves in followed by the assembly of the reservoir 12 and the cylinder 14 over the entire length of the substrate 1, the mask 13 avoiding an excessively rapid evaporation of the solvent from the solution 4. For more details on the latter technique, we will refer advantageously to the patent application WO-94/01598 mentioned above.

Tests were carried out on the substrates obtained according to the previous examples in order to characterize the deposited coatings and evaluate their anti-turbidity and anti-dirt performances.

□ Test 1: is the test of the turbidity figures. It consists of observing the consequences of photocatalysis and of scraping. ifevfesfimÊèfc: (rates of hydroxyl groups, porosity, roughness) on wetting. If the surface is photoreactive, the carbonated micro-pollutions that are deposited on the coating are permanently destroyed and the surface is hydrophilic therefore anti-turbidity. It is also possible to make a quantitative evaluation by abruptly heating the coated substrate initially, stored in the cold or simply blowing on the substrate, measuring whether turbidity appears and if so, at that moment, then measuring the time necessary for the disappearance of said turbidity.

□ Test 2: it is a question of evaluating the hydrophilic and oleophilic on the surface of the coating 3, in comparison with those on the surface of a naked glass, by measuring the contact angles of a drop of water and a drop of DOP (phthalate of dioctyl) on their surfaces, after having left the substrates for a week in the ambient atmosphere under natural lighting, in the dark after having subjected them to UVA radiation for 20 minutes.

□ Test 3: consists of depositing a layer of an organosilane on the substrate to be evaluated and irradiating with UVA in order to degrade it by photocatalysis. The organosilane that modifies the wetting properties, the measurements of the angle of contact with the water of the substrate during irradiation indicate the degradation state of the grafted layer. The rate of disappearance of this layer is linked to the photocatalytic activity of the substrate.

The grafted organosilane is a trichlorosilane: octadecyltrichlorosilane (OTS). The graft is performed by immersion.

The tester consists of a rotating carousel around 1 to 6 low pressure UVA lamps. The specimens to be evaluated are placed on the carousel, the face to be evaluated on the side of the UVA radiation According to their position and the number of illuminated lamps, each specimen receives a UVA irradiation that varies from 0.5 W / m² at 50 W / m². For examples 1,2,3, 8 and pptêàjÇffc (jeiÂHib &amp; Sft is chosen from 1,8 W / m² and for examples 4 to 7 of 0.6 W / m².

The time between each contact angle measurement varies between 20 minutes and 3 hours, according to the photocatalytic activity of the specimen considered. Measurements are made with the help of a goniometer.

Before irradiation, the glasses have an angle of approximately 100 °. The layer is considered to be destroyed after irradiation when the angle is less than 20 °.

Each test specimen tested is characterized by the average speed of disappearance of the layer, supplied in nanometer per hour, that is, the thickness of the deposited organosilane layer divided by the irradiation duration that allows reaching a final level below 20 ° (time of disappearance of the layer). organosilane layer).

All of the previous examples are successful in test 1, that is, when blowing on the coated substrates of the coating, they remain perfectly transparent, while a very visible turbidity layer is deposited on uncoated substrates.

The examples were subjected to test 2: the coated substrates, after exposure to UVA radiation, have a contact angle with water and with a DOP of at most 5 °. In contrast, bare glass in the same conditions has a 40 ° water contact angle and a 20 ° DOP contact angle.

The following table regroups the results of the coated substrates according to the examples prior to test 3.

<td>Substrate</td><td>1.8 W / iJi enhancement test 3². uJ.AÂeÍ5 ^)⁵·⁵1 '* M </td>

<td>Example 1 (TiO₂ on bare glass)</td><td> 0,03</td>

<td>Example 2 (TiO₂ about SnO₂: F)</td><td> 0,1</td>

<td>Example 3 (TiO₂ about SiOC)</td><td> 0,2</td>

<td>Example 8 (TiO₂ about 50nm SiOC)</td><td> 55</td>

<td>Example 9 (TiO₂ about 50nm SiOC)</td><td> 5</td>

<td>bare glass</td><td> 0</td>

<td>Substrate</td><td>Wetting test 3 at 0.6 W / m²UVA (in nm / h)</td>

<td>Example 4 (TiO₂ on bare glass)</td><td>&lt;0.05 nm / h</td>

<td>Example 5 (TiO₂ about SiOC)</td><td> 4</td>

<td>Example 6 (TiO₂ on bare glass)</td><td> 9</td>

<td>Example 7 (TiO₂ about SiOC)</td><td> 19,5</td>

From the table, it can be seen that the presence of sub-layers, especially SiOC, favors the photocatalytic activity of the coating containing TiO₂, due to its barrier effect to alkali and alkaline earth that can migrate from glass (comparison of examples 4 and 5 or 6 and 7).

It is also observed that the thickness of the coating containing TiO₂ also plays a role (comparison of examples 1 and 3): for a coating thickness of TiO₂ greater than the average size of mono-crystals or crystallites, a better photocatalytic effect is obtained.

In fact, it can be seen that they are TiO coatings₂ obtained by CVD which present the most advanced crystallization, with crystallite sizes in the order of 20 to 30 nm. It can be seen that the photocatalytic activity of example 6 (65 nm TiO₂) is significantly higher than in example 4 (15 nm TiO₂ only). It is therefore advantageous to provide a coating thickness of TiO₂ at least twice the average diameter of the crystallites it contains. Alte {rfat | vàà ^ iitç, coffeíí b:

• · ·· · ·: * “·» · In the case of example 5, a thin thickness of TiO coating can be preserved₂ but then choose to use a sub-layer of the appropriate nature and thickness to favor the maximum crystalline growth of TiO₂ from the first layer of crystallites.

It was observed that the crystallization of TiO₂ it was a little less advanced for coatings deposited by a technique other than CVD. At this point, however, everything is still a compromise: less advanced crystallization and a lower photocatalytic activity can be compensated by using a less expensive or less complex deposit process, for example. In addition, the use of an appropriate sub-layer or the activation of TiO₂ may allow to improve photocatalytic performances if necessary.

It is also verified by comparing examples 2 and 3 that the nature of the sub-layer influences the mode of crystallization and, in fact, the photocatalytic activity of the coating.