Substrate with photocatalytic coating

Substrate with photocatalytic coating

FIELD OF THE INVENTION The present invention relates to glass-, ceramic- or vitroceramic-based substrates, made in particular of a special transparent substrate of glass, which transparent substrate is suitable for use as practical glazing or glazing for vehicles or buildings. , is provided with a coating having photocatalytic properties, for the purpose of producing glazing for various applications.

Research is increasing on functionalizing glazing by depositing on the surface of the glazing thin layers intended to impart specific properties to the target application. Accordingly, there are layers having an optical function, such as so-called anti-glare layers, which optionally constitute a stack of layers having a high or low refractive index. For an anti-static function or a heating function of the anti-icer type, it is advantageous to provide electrically conductive thin layers, for example based on metal or with added metal oxide. Also possible. For example, for a sun-blocking or low-radiation heat function, thin layers made of a metal of the silver type or based on a metal oxide or made of a nitride can be used. "Rain-repellent" In order to achieve an effect, it is possible to provide the layers with a hydrophobic nature, for example based on fluorinated organosilanes and the like.

However, there is still a need for substrates, particularly window panes, that can be described as "dirt-blockers" with respect to shape and surface properties, ie, aimed at permanence over time, which are progressively deposited on the surface of the substrate. When soil marks are formed, especially of organic origin, such as finger marks or volatile organics present in the atmosphere, or even in the form of agglomerates, the result is that the removal of such marks is achieved, so that the window glass is particularly cleaned. make it possible to avoid frequent and/or improve visibility.

In fact, it is known that, under the effect of radiation of a suitable wavelength, certain semiconductor materials based on metal oxides are capable of generating rapid reactions leading to oxidation of organic matter; In general, these semiconductor materials are "photocatalyst" or optionally "photoreaction" referred to as materials.

Accordingly, it is an intention of the present invention to generate a photocatalytic coating on a substrate, said photocatalytic coating being a "soil-blocking agent" It can be manufactured industrially while exhibiting the display effect of

It is an object of the present invention as a glass-, ceramic- or vitroceramic-based substrate, in particular made of glass and transparent, said substrate having a coating having photocatalytic properties comprising at least partly crystalline titanium oxide on at least one side of the substrate provided in part. The titanium oxide is preferably crystallized "in situ" during the formation of the coating on the substrate.

In fact, titanium oxide is one of the semiconductors that degrades organic matter deposited on the surface of a substrate under the effect of light in the visible or ultraviolet range. As such, "dirt-blockers" The choice of titanium oxide for producing effective glazing is particularly pointed out, moreover, since the oxide exhibits good mechanical strength and good chemical resistance: although repeated handling by mechanical or pneumatic prehension means Although directly exposed to numerous attacks, especially during glazing on the building site (building) or production line (transportation) concerned, once the glazing has been subjected to wear (windscreen wipers, wear fragments) and aggressive chemicals (SO₂For long-term effectiveness, the coating is obviously important to maintain the integrity of the windowpane when placed in a location where there is a risk of contact with tangible air pollutants, cleaning products, and the like).

In addition, the selection is made for at least partially crystalline titanium oxide because it is known to have a much better performance for photocatalytic properties than amorphous titanium oxide. In the form of anatase, in the form of rutile or in the form of anatase and rutile, having a crystallinity of at least 25%, in particular approximately 30 to 80%, especially closely to the windowpane face (rather, a feature having a facet characteristic). It is preferable to crystallize in a mixed form. (Crystallinity depends on TiO in the coating₂TiO for the total weight of₂is understood to mean the crystal weight of

In addition, TiO grown on the substrate₂It is becoming possible to observe in the case of crystals, especially in the case of crystals, that the orientation of the crystals influences the photocatalytic behavior of oxides in the form of anatase: there is a preferred orientation (1,1,0) that significantly promotes the photocatalysis.

The coating is in the form of "crystallites" in which the crystalline titanium oxide contained therein is at least close to the face of the windowpane, so to speak, 0.5 and 100 nm, preferably 1 to 50 nm, in particular 10 to 40 nm, more particularly is advantageously prepared as monocrystals having an average size between 20 and 30 nm. In fact, titanium oxide is within this size range that appears to give an optimal photocatalytic effect, presumably because crystals of this size create a high active surface area.

As can be seen in more detail as a result, it becomes possible to obtain coatings based on titanium oxide in many ways:

- Decomposition of titanium precursors (pyrolysis techniques: liquid phase pyrolysis, powder pyrolysis, vapor phase pyrolysis known as CVD (chemical vapor deposition), or sol-gel related techniques: dipping, cell coating, and the like) ,

- As a vacuum technique (reactive or non-reactive cathode sputtering).

In addition, the coating may, in addition to crystalline titanium oxide, be formed of one or more other types of inorganic materials, in particular in the form of amorphous or partially crystalline oxides, for example silicon oxide (or mixtures of oxides), titanium oxide, tin oxide, zirconium oxide or It may include aluminum oxide. In addition, the inorganic material has a photocatalytic effect to a certain extent, even in the case of tin oxide or amorphous titanium oxide, crystalline TiO₂By showing a weak effect by itself compared to that of , it may be involved in the photocatalytic effect of crystalline titanium oxide.

As such, "mixed" combined with at least partially crystalline titanium oxide with one or more other oxides. The layer of oxide is, from an optical point of view, more particularly if other oxides or oxides are TiO₂It can be beneficial if it is chosen with an index lower than that of the "overall" of the coating. By lowering the refractive index, it is possible to alter the light reflection of the substrate provided for the coating, in particular to lower said reflection. This can be done if, for example, TiO is produced by the method described in European Patent EP-0,465,309.₂/Al₂O₃or TiO₂/SiO₂This is the case when a layer made of Of course, however, the coating must have sufficient amount of TiO to maintain significant photocatalytic activity.₂It is essential to include As such, the coating comprises, in the coating, at least 40% by weight, in particular at least 50% by weight TiO, relative to the total weight of the oxide(s).₂It is considered preferable to include

In addition, the fluorinated organosilanes described in, for example, US Pat. Nos. 5,368,892 and US-5,389,427, which are stable or resistant to photocatalysis in coatings according to the present invention, and European patents of special formula issued under Patent No. FR-2,722,493 Grafted oleophobic and/or hydrophobic (grafted oleophobic) and/or hydrophobic ( It becomes possible to select and superimpose the hydrophobic layer:

CF₃-(CF₂)n-(CH₂)_m-SiX₃as

n is 0 to 12, m is 2 to 5, and X is a hydrolysis group.

In order to amplify the photocatalytic effect of the titanium oxide of the coating according to the invention, first of all, by incorporating other particles into the coating, in particular metal particles or particles based on cadmium, tin, tungsten, zinc, cerium or zirconium, It is possible to increase the absorption width.

It is also possible to increase the number of charge carriers by adding a crystal lattice of titanium oxide by inserting therein one or more of the following metal elements: ie, the following metal elements are niobium, tantalum, iron, bis. Muth, cobalt, nickel, copper, ruthenium, cerium or molybdenum.

Further, the addition can be carried out by surface addition only for titanium oxide or bonding coatings, the surface addition being carried out by applying a metal oxide or salt to at least a portion of the coating, the metal being iron, copper, ruthenium, cerium, molar selected from ribdenium, vanadium and bismuth.

Finally, the photocatalytic phenomenon increases the yield and/or kinetics of the photocatalytic reaction, whereby at least a portion of the coating incorporating the additive in the form of a thin layer of a noble metal of the platinum, rhodium, silver or palladium type or It can be strengthened by covering titanium oxide.

For example, the catalyst deposited by vacuum technology enhances the number and/or lifetime of radical entities created by titanium oxide, making it virtually possible to promote chain reactions leading to degradation of organic matter. makes

In an overall surprising way, the coating exhibits not one property, but two properties as soon as the coating is exposed to suitable radiation, such as sunlight, visible and/or ultraviolet wavelengths: the presence of photocatalytic titanium oxide, as is already known, the coating When silts of organic origin accumulate, they promote gradual extinction, their degeneration by a radical oxidation process. Inorganic soil marks do not degrade themselves by the process: therefore, the inorganic soil marks remain on the surface and, with the exception of the degree of crystallization, they no longer adhere to the surface of the degenerated organic binding agent by photocatalysis. It is easily removed in part because there is no reason to do it.

However, it is desirable that the coatings of the present invention be permanently self-cleaning and exhibit manifested hydrophilic and/or lipophilic properties which produce three very useful effects on the exterior surface:

- The hydrophilic nature makes the coating as completely wet as possible any water that may fall on it. When water agglomeration occurs, instead of falling into droplets in the form of agglomerates that obstruct visibility, it actually exists as a continuous thin film of water that is entirely transparent as it forms on the surface of the coating. In particular, the "anti-agglomeration" The effect was demonstrated as a measurement of a contact angle of less than 5° with water after exposure to light. and

- After rain flows over water, especially surfaces that have not been treated with a layer of photocatalyst, many rainwater droplets hit the surface and remain, once evaporated, leaving unsightly and troublesome marks, mostly inorganic sources. Indeed, surfaces exposed to ambient air are quickly covered with a layer of dirt marks that limit wetting by water. The dirt marks are in addition to other dirt marks, especially mineral marks (crystals and the like) contributed by the atmosphere of the window glass baths. In the case of a photoreactive surface, the inorganic dirt marks are not directly degraded by the photocatalyst. In fact, most of the inorganic marks are removed by the hydrophilic nature induced by the photocatalytic activity. This hydrophilic nature indeed causes the complete spread of raindrops. Therefore, the evaporation marks are no longer present. Moreover, dirt marks of other minerals present on the surface are either wiped off or dissolved in the case of crystals by a water film, and thus most are removed. Inorganic "dirt-blocker" The effect is achieved especially induced by rain,

- with respect to the hydrophilic nature, the coating may also exhibit a lipophilic nature which makes possible the "wetting" of the organic soil marks, and thus, as with water, a markedly localized "stains" It tends to deposit on the coating in the form of a more invisible continuous film. As such, "organic soil-blocking agent" The effect can be achieved by working in two ways: as soon as the soil-blocking agent of the organism is deposited on the coating, the soil marks are already almost invisible. As a result, the dirt marks gradually disappear due to the radical degradation driven by the photocatalyst.

The coating may be chosen for a rather smooth surface. A degree of roughness can indeed be beneficial:

- roughness has the potential to develop a larger active photocatalytic surface area, thus leading to a larger photocatalytic activity,

- Roughness has a direct effect on wetting. In fact, roughness enhances the wetting properties. A smooth hydrophilic surface, once roughened, becomes more hydrophilic. "Roughness" is understood in the above case to mean both surface roughness and roughness, which are induced as a porous layer at least partly of its own thickness.

These effects become even more pronounced when the coating is porous and rough, as it creates a superhydrophilic effect on the rough photoreactive surface. However, if there is too much roughness, the roughness can become difficult by promoting the covering or accumulation of dirt marks and/or resulting in an optically unacceptable dim level appearance.

Thus, TiO such that the coating exhibits a roughness of approximately 2 to 20 nm, preferably 5 to 15 nm.₂- Adopting a method for depositing the base coating has proven to be advantageous, the roughness being evaluated by atomic force microscopy and measurement of the Root Mean Square i.e. RMS value for a surface area of 1 square micrometer do. In terms of the roughness, the coating exhibits a hydrophilic property that is reflected with a contact angle of 1° or less with respect to water. It is also known to be advantageous to enhance the degree of porosity within the thickness of the coating. Therefore, if the coating is TiO₂If it consists of only, the coating preferably exhibits a porosity of the order of 65 to 99%, in particular 70 to 90%, the porosity in this case being TiO₂is defined indirectly as a percentage of the theoretical relative density of TiO₂The percentage of theoretical relative density of is approximately 3.8. One means to enhance the porosity includes, for example, vapor deposition coating by a sol-gel type technique, which involves the decomposition of organometallic type materials; thus, PolyEthylene Glycol (PEG) type. of the organic polymer can be incorporated by addition of organometallic precursor(s) to the solubilizing agent: upon heating the layer to cure, the PEG burns away, creating or enhancing the degree of porosity within the thickness of the layer.

The thickness of the coating according to the invention varies; The thickness of the coating is preferably between 5 nm and 1 micron, in particular between 5 and 100 nm, in particular between 10 and 80 nm or between 20 and 50 nm. In fact, the choice of thickness depends on a variety of variables, especially for applications targeted to glazing type substrates or optionally for coatings of TiO2.₂ It depends on the size of the crystals or on the presence of a high proportion of alkali metals in the substrate.

It is possible to provide a function different or complementary to the function of the coating in one or several other thin layers between the substrate and the coating according to the invention. Said complementary function is in particular TiO in the form of anatas or rutile with anti-static, thermal or optical function.₂ Layers that promote the growth of crystals, or form barriers that prevent the movement of certain elements originating from the substrate, in particular of alkali metals and very particularly of sodium ions when the substrate is made of glass. can

In addition, the coating according to the invention, which constitutes the lamination of the final layer, can be repeated as thin layers of "anti-glare" It makes it possible to observe the stacking of layers with high and low refractive indices. In this case, the coating is composed of a mixed oxide of titanium and silicon, and it is preferable to have a relatively low refractive index.

In particular, a layer having anti-static and/or thermal function (heating by providing the layer with powder lead, low-emissivity material, sun-blocking material, and the like) may be of a metal type such as silver, or tin ITO Added indium oxide, fluorine-type halogen SnO₂:F or antimony SnO₂: can be selected based on the conductive material of the added metal oxide type, such as tin oxide with Sb or zinc oxide with addition of indium ZnO:In, fluorine ZnO:F, aluminum ZnO:Al or tin ZnO:Sn. . In addition, the layer is SnO where X is less than 2_2-Xor ZnO_2-Xcan be related to metal oxides that are stoichiometrically oxygen deficient, such as

The layer having an antistatic function preferably has a surface resistance value of 20 to 1000 ohms·square. Equipment can be made by providing power leads to the layer to polarize the layer (eg supply a voltage between 5 and 100V). Said controlled polarization makes it possible in particular to control the deposition of dust with a size on the order of a millimeter that can be deposited on the coating, in particular dry dust that sticks only by the electrostatic effect: by abruptly changing the polarization of the layer, the dust It becomes "emitted".

A thin layer with an optical function may be selected to reduce light reflection and/or to further neutralize the color reflected to the substrate. In this case, the thin layer preferably exhibits a suitable optical thickness and a refractive index interposed between the coating and the substrate, the thin layer being an oxide or aluminum oxide Al₂O₃, tin oxide SnO₂, Indium Oxide₂O₃Alternatively, it may be composed of a mixed oxide of silicon oxycarbide or oxynitride type. In order to achieve a maximum attenuation of the reflected color, it is necessary that the thin layer exhibit a refractive index close to the square root of the product of squares, so to speak, for the two materials constituting the substrate and the coating according to the invention. may be desirable for In the same way, the optical thickness of the thin layer (say the product of the geometric thickness of the thin layer and its refractive index) similar to the lambda, 1/4 lambda, which, in particular about 500 to 550 nm, is about the average wavelength of visible light. Choosing can be beneficial.

In particular, a thin layer having a barrier function against alkali metals can be selected based on silicon oxide, nitride, oxynitride, or oxycarbide, wherein the thin layer is aluminum oxide Al containing fluorine.₂O₃Made of :F or optionally made of aluminum nitride. In fact, a thin layer has proven useful when the substrate is made of glass, since the migration of sodium ions towards the coating according to the present invention can adversely affect the photocatalytic properties under certain conditions.

The nature of the substrate or sub-layer furthermore has an additional advantage: said substrate or sub-layer can promote crystallization of the deposited photocatalytic layer, especially in the case of CVD (chemical vapor deposition) deposition.

Therefore, TiO by CVD₂During the deposition of crystalline SnO₂The :F sublayer is usually in the form of rutile, especially TiO with deposition temperatures ranging from 400°C to 500°C.₂On the other hand, the surface of the soda-lime glass or silicon oxycarbide sub-layer induces anatase growth, particularly at a deposition temperature of 400°C to 600°C grade.

All said optional thin layers may be deposited in a known manner by vacuum techniques of the cathodic sputtering type, such as pyrolysis in solid, liquid or gas phase, or by other techniques of the pyrolysis type. Each of the above-mentioned layers can combine multiple functions, but it is also possible to overlap the functions.

Another object of the present invention is whether the thin layer is a single unit, or insulates multiple units of double glazing or laminated type, a "soil-blocking agent" (organic and/or inorganic soil marks) and/or " It is an anti-agglomeration" glazing, said glazing incorporating the above-mentioned coated substrates.

Therefore, the present invention relates to the production of glass, ceramic or vitroceramic articles and very particularly to "self-cleaning" It is aimed at the manufacture of window glass. The latter is advantageous for building glazing, such as double glazing (hence it is possible to align the "outer side" and/or "inside side" of the coating, so to speak to face 1 and/or face 4). can be assembled This is proving to be very particularly beneficial for glazing, such as roof glazing, airport glazing, and the like, which cannot come very close to cleanliness and/or needs to be cleaned very often. In addition, the window glass may relate to a window of a vehicle in which the maintenance of visibility is an essential safety criterion. Therefore, the coating can be deposited on the windscreen, side window or rear window of the vehicle, in particular on the side of the window turning towards the interior side of the passenger compartment. Thus, the coating can block the formation of agglomerates and/or release by traces of dirty finger prints, nicotine or organic material types, ie the plastics constituting the interior of the passenger compartment, in particular the plastics of the dashboard (the release is sometimes " It is possible to remove the organic material present in a volatile, plastic type (known by the term "fogging"). In addition, other vehicles, such as airplanes or trains, may find it advantageous to use the windows provided with the coatings of the present invention.

In particular, as a cotton material, such as aquarium glass, shop windows, green-houses, verandas, or glass used for indoor or street furniture, as well as mirrors, television screens, spectacle fields or tiles and the like. Many other applications are possible, of the type of building material, cladding material or roofing material.

Therefore, the present invention makes it possible to functionalize the known products by imparting them with UV-blocking, soil-blocking, bactericidal, anti-glare, anti-static or antibacterial properties and the like.

Another advantageous application of the coating according to the invention is achieved by combining the following types of electrically controlled changeable absorption glazing in said products: electrochromic glazing, optionally dichroic dyes ( liquefied crystalline glazing to which dichroic dye is added, glazing comprising a system in which particles are suspended, viologen glazing and the like. In general, since all said glazing types consist of a plurality of transparent substrates between disposition of "active" elements, thereby advantageously disposing a coating on the outer surface of one or more of said substrates. can do.

In particular in the case of electronic tinted glazing, when the latter is in the tinted state, the absorbing action of the electronic tinted glazing can in fact accelerate the photocatalytic decomposition of the carbonaceous material deposited on the coating according to the invention. Some degree of surface heating is generated. For further details on the construction of electronically colored glazing, reference is advantageously made to patent application EP-A-0,575,207 which describes an electronically colored laminated double glazing, the coating according to the invention preferably being on side 1 It may be possible to be located.

Another object of the present invention is the various processes for obtaining the coating according to the present invention. When a glass substrate is used, the process makes it possible to use a deposition technique of the pyrolysis type, which can be advantageous because it makes in particular possible the continuous deposition of the coating directly on the float-glass strip.

The pyrolysis can be carried out from the powder(s) of the precursor(s) of the organometallic type to the solid phase.

The pyrolysis may be carried out in the liquid phase from a solvent comprising an organometallic titanium precursor of titanium chelate and/or a titanium alcohol type. One or more other organometallic precursors are mixed with the precursors. For further details on the properties or deposition conditions of the titanium precursor, reference will be made to, for example, French Patent FR-2,310,977 and European Patent EP-0,465,309.

In addition, the pyrolysis can be performed in the vapor phase, the pyrolysis technique is titanium tetrachloride (TiCl₄) or titanium alcohol of titanium tetraisopro-pylate type (Ti(OiPr)₄) from one or more halide types of titanium precursors such as CVD (Chemical Vapor Deposition). The crystallization of the layer can be further controlled by the type of sub-layer, as mentioned above.

It is also possible to deposit the coating by other techniques, in particular the techniques combined with "sol-gel". Various deposition methods are possible, such as deposition with cells, also known as "dipping", also known as "dip coating" or "cell coating". In addition, pyrolysis is a "spray coating" or to a deposition method by lamina coating, the latter technique being described in detail in International Patent Application WO-94/01598. In general, all of the above deposition methods use a solvent comprising at least one organometallic precursor, especially titanium of the alcohol type, which is thermally decomposed after coating the substrate on one or both sides of the substrate with a solvent. .

It may be more beneficial to deposit a coating whether the deposition technique is envisioned as two or more successive steps rather than as a single step, the deposition technique being able to use titanium through the thickness of the coating when a relatively thick coating is selected. It tends to promote the crystallization of oxides.

Likewise, it is beneficial to impart photocatalytic properties to the coating after deposition by annealing type heat treatment. Heat treatment is essential for sol-gel or lamina coating type techniques to decompose the organometallic precursor(s) into the oxide, and to improve resistance to abrasion when pyrolysis techniques are not used, once Once the substrate is coated, the precursor disintegrates as soon as it begins to contact the substrate. In the first case, but as in the second case, the post-deposition heat treatment is TiO₂improves the degree of crystallization of the coating as soon as it is formed. The selected heat treatment temperature makes it possible to better control the degree of crystallization and the crystalline properties, the grade of anatas and/or rutile, and the grade of the oxide.

However, in the case of a substrate made of soda-lime glass, multiple and time-extended annealing may promote weakening of the photocatalytic activity due to overmigration of alkali metals from the substrate toward the photocatalytic layer. The use of a barrier layer between substrates, if the barrier layer is made of standard glass, and the choice of a substrate to make the glass into a coating, or suitable composition, or, optionally, soda-lime glass on the surface from which alkali metals have been removed. to make it possible to eliminate this risk.

Other advantageous descriptions and features of the present invention emerge from the non-limiting supplementary examples and description with the aid of the following drawings:

1 is a cross-sectional view showing a glass substrate provided with a coating according to the invention;

Fig. 2 is a schematic diagram showing a sol-gel deposition technique by means of a so-called "dip coating" coating;

Figure 3 is a schematic diagram illustrating a deposition technique called "cell coating";

Fig. 4 is a schematic diagram illustrating a deposition technique called "spray coating";

5 is a schematic diagram showing a deposition technique by lamina coating.

As shown very schematically in FIG. 1 , all of the following examples are based essentially on titanium oxide on a transparent substrate 1 , a so-called "soil-blocking agent" It relates to the deposition of the coating (3).

The substrate 1 is made of clean soda-lime-silica glass having a thickness of 4 mm and a length and width of 50 cm, respectively. It is clear that the present invention is not limited to this particular type of glass. Also, the glass may not be flat but may bend.

Between the coating 3 and the substrate 1 an optional thin layer 2 is found, which thin layer 2 constitutes a barrier to the diffusion of alkali metals and/or a layer that attenuates light reflection. For this purpose, an antistatic and/or low-emission layer, which is also based on silicon oxycarbide, and has a low-emission effect, which is also based on silicon oxycarbide, written as SiOC, and/or a layer that attenuates the reflected color in particular For the purpose of composing, fluorine SnO₂: Also based on F-doped tin oxide.

<b><u> Examples 1 to 3 </u></b>

Examples 1-3 relate to a coating (3) deposited using liquid phase pyrolysis techniques. The operation may be carried out continuously by using a stable spray nozzle disposed across the float-glass strip on the exit side of a suitable float-bath chamber. In this case, the operation is performed non-continuously, by using a movable nozzle disposed opposite to the substrate 1 already cut to the size indicated, the substrate being uniformly passed through a nozzle spraying a suitable solvent. Before proceeding to speed, it is first heated in an oven to a temperature of 400 to 650 °C.

<b><u> Example 1 </u></b>

In this example, there is no optional layer 2 . The coating 3 is coated with a solvent containing two organometallic titanium precursors, titanium diiso-propoxide diacetylacetonate and titanium tetraoctylene-glycolate. and the coating is dissolved with a mixture of two solvents, the latter being ethyl acetate and isopropanol.

In addition, other precursors of the same type, in particular titanium acetylactonate, titanium (methyl acetoacetato), titanium (ethyl acetoacetato) or optionally titanium triethanol It should be noted that it is entirely possible to use other titanium chelates of the titanium triethanolaminato or titanium diethanolaminato type.

As soon as the substrate 1 has reached the desired temperature in the oven, ie especially at a temperature of approximately 500°C, the substrate is advanced through a nozzle which is sprayed with compressed air and the indicated mixture at room temperature.

So, TiO with a thickness of approximately 90 nm₂A layer is obtained, the thickness of which can be controlled by the speed of travel of the substrate 1 past the nozzle and/or the temperature of the substrate. The layer is partially present as crystals in the form of anatase.

The layer exhibits good mechanical behavior. The durability of the layer to abrasion tests can be compared to that obtained for the surface of exposed glass.

The layer can be bent and can be dip coated. The layer shows no bloom: the scattered light transmittance of the coated substrate is 0.6% (D₆₅measured at 560 nm by the illuminator).

<b><u> Example 2 </u></b>

Example 1 was repeated but SnO with a thickness of 73 nm between the substrate 1 and the coating 3₂:F layer (2) is inserted. the SnO₂The :F layer is obtained by powder pyrolysis from dibutyltin difluoride (DBTF). The layer can also be obtained in a known manner, for example by pyrolysis into the liquid or vapor phase, as described in patent application EP-A-0,648,196. In the vapor phase, in particular, H₂It is possible to use mixtures of monobutyltin trichloride and fluorinated precursors optionally combined with a "mild" oxide of type O.

The refractive index of the obtained layer is approximately 1.9. The surface resistance of the layer is approximately 50 ohms.

In the preceding example 1, the coated substrate 1 mounted as a double-glazed glass was on the side 1 (another substrate 1') side having the same properties and dimensions as the substrate 1 which was not coated but had an air layer of 12 mm. ), emit a color saturation value of 26% reflection and a color saturation value of 6.8% transmission.

In Example 2 above, the color saturation of the reflection (in gold) is only 3.6% and the color saturation of the reflection is 1.1% of the transmission.

Therefore, the SnO₂The :F sub-layer makes it possible to impart anti-static properties to the substrate due to its electrical conductivity, and also₂The :F sub-layer has a good effect on the color system of the substrate by making its color more significantly "neutral" It is caused by the presence of an oxide coating (3). It is possible to polarize the sub-layer by providing an appropriate supply of electricity to the sub-layer, in order to limit the deposition of millimeter-scale dust, having a relatively large size.

In addition, the sub-layer is photocatalytic TiO₂Reduces the diffusion of alkali metals towards the layer. Therefore, the photocatalytic activity is improved.

<b><u> Example 3 </u></b>

Example 2 was repeated but this time inserting a layer 2 between the substrate 1 and the coating 3 based on silicon oxycarbide having a refractive index of approximately 1.75 and a thickness of approximately 50 nm, the layer being described in the patent application EP- As described in A-0,518,755, SiH₄ and from a mixture of ethylene diluted in nitrogen by CVD. The layer is an alkali metal (Na) generated from the substrate 1⁺, K⁺) and alkaline-rare earth metals (Ca⁺⁺) is particularly effective in blocking the tendency to diffuse toward the coating 3, and therefore the photocatalytic activity is remarkably improved. The layer (2) is SnO₂Since :F has a refractive index interposed between the substrate 1.52 and the coating 3 (approximately 2.30 to 2.35), it may also become possible to reduce the color intensity of the substrate, in both reflection and transmission. , the light reflection value of the substrate (R_L) can be reduced overall.

The following examples 4 to 7 relate to deposition by CVD.

<b><u> Examples 4 to 7 </u></b>

This example relates to a coating 3 having been deposited by CVD directly on a substrate 1 using a standard nozzle, as shown in the above-mentioned patent application EP-A-0,518,755. Use is made as a precursor of organometallic compounds or metal halides. In this case, titanium tetraisopropylate is chosen as the organometallic compound, which is advantageous because of its high volatility and its large operating temperature range from 300 to 650°C. In the example above, the deposition was performed at approximately 425 °C and TiO₂is 15 nm thick.

In addition, tetraethoxytitanium (tetraethoxytitanium); Ti(O-Et)₄may be suitable as a halide, wherein Ti(O-Et)₄is TiCl₄may be made of

<b><u> Example 5 </u></b>

In this case, 15 nm TiO₂Similar to Example 4 was performed, with the exception that the layer was deposited on a 50 nm SiOC sublayer as in Example 3 rather than being deposited directly on the glass.

<b><u> Example 6 </u></b>

In this case, the TiO₂Carried out as in Example 4, with the exception that the thickness of the layer was 65 nm.

<b><u> Example 7 </u></b>

In this case, TiO₂Performed as in Example 5, with the exception that the thickness of the layer was 60 nm.

From Examples 4 to 7 above, it is found that, as such, the coated substrate exhibits good mechanical behavior for wear testing. In particular, TiO₂No delamination of the layer was observed.

<b><u> Example 8 </u></b>

This example uses a sol-gel combination technique using a deposition method by "dipping", also known as "dip coating", as the principle emerges from FIG. It consists in immersing the substrate 1 in a liquid dissolving agent 4 comprising (s) and furthermore retracting the substrate 1 therefrom at a controlled speed using a motor means 5, the selection of the retraction speed being It makes it possible to adjust the thickness of the dissolving agent remaining on the surfaces of both sides of the substrate, in fact the choice of the retraction rate is to heat the latter in the order of both evaporating the dissolving agent and decomposing the precursor or the oxide precursor. After that, it makes it possible to adjust the thickness of the deposited coating.

Use as DiEthanolAmine (DEA) in a molar ratio 1:1 in an ethanol-type solubilizer containing 0.2 mol (mol) of tetrabutoxide per liter of ethanol to deposit the coating (3). Stabilized, titanium tetrabutoside Ti(O-Bu)₄ or a solubilizing agent 4 comprising a mixture of the precursor and the solubilizing agent described in Example 1 (other precursors such as titanium(diethanolamineto)dibutoside may also be used).

The substrate 1 may include SiOC sub-layers.

After withdrawing from each dissolving agent 4, the substrate 1 is heated at 100°C for 1 hour, and then the substrate 1 is heated to an increasing temperature at 550°C for approximately 3 hours.

A coating (3) is achieved on each side, said coating being in two cases highly crystalline TiO in the form of anatase₂is made with

<b><u> Example 9 </u></b>

This example uses a technique known as "cell coating", in a principle that can be recalled in FIG. 3 . The cell coating is substantially two parallel faces (6, 7) and two seals (8, 9) of one or more of the faces (6, 7) constituting the face of the substrate 1 to be processed. relates to the formation of a narrow cavity, delimited by Therefore, the cavity is filled with a solubilizer 4 of the precursor(s) of the coating, which for example leaves a film of the solubilizer 4 on the face of the substrate 1 when the solubilizer is withdrawn, Using a peristaltic pump 10, it is retracted in a controlled manner to form a wetting meniscus.

Therefore, the cavity 5 is kept for at least the necessary time for drying. The film is cured by heat treatment. The advantage of this technique is that, compared to "dip coating", both sides of the substrate 1 are not in order, so that it is possible to treat only one side of the substrate 1 if the masking system does not help. will be.

The substrate 1 comprises thin layers 2 based on silicon oxycarbide SiOC.

Example 6 uses the dissolving agent 4 described in Example 8, respectively. Therefore, the same heat treatment₂carried out to obtain a coating (3).

The coating 3 exhibits good mechanical durability.

Under SEM (Scanning Electron Microscopy), the field effect appears in the form of "grains" of single-crystals with a diameter of approximately 30 nm. The roughness of the coating leads to enhanced wetting properties over non-roughness coatings.

Also, the same dissolving agents 4 can be used to deposit a coating by "spray coating", as shown in FIG. It is sprayed in the form of a cloud pattern toward (1) or as a lamina coating. In the latter case, the substrate 1 held by vacuum suction towards a support 11 made of stainless steel and Teflon is handed over to a tank 12 containing a dissolving agent, which is a slotted cylinder ( 14 ), and then the combined tank 12 and cylinder 14 are moved over the entire length of the substrate 1 , and the mask 13 prevents excess evaporation of the solvent from the solvent 4 . do. For further details regarding this latter technique, reference is advantageously made to the above-mentioned patent application WO-94/01598.

Tests characterize the coatings being deposited and their "anti-agglomeration" and "dirt-blockers" In order to evaluate the behavior, it is carried out on the substrates obtained according to the above examples.

- <b>Test 1: </b>This is a cohesive shape test. The test consisted of observing the results of the photocatalyst and coating structure (level of hydroxyl groups, porosity, roughness) on wetting. If there is a photoreaction on the surface, the carbonaceous microcontaminants deposited on the coating are subsequently destroyed, making the surface hydrophilic and thus agglomeration-resistant. In addition, by abruptly reheating an initially coated substrate, stored cold on the substrate or simply blown, by measuring at what time agglomeration actively occurs, and thus by measuring the time required for the agglomeration to dissipate. , it is possible to perform a quantitative evaluation.

- <b>Test 2: </b>This leaves the substrate in the dark in ambient atmosphere under natural light for a week, so after placing the substrate under UVA radiation for 20 minutes, contact of water droplets and DOP (dioctyl phthalate) droplets on the surface of the substrate By measuring the angle, it relates to evaluating the hydrophilicity and lipophilicity of the surface of the coating (3) compared to the water droplets and DOP of the exposed glass surface.

- <b>Test 3: </b>This consists in depositing a layer of organosilane on the substrate being evaluated and irradiating the organosilane with UVA radiation to degrade the organosilane by photocatalysis. When the organosylane is transformed into wetting properties, measurement of the contact angle of water to the substrate during radiation indicates the degradation of the bonding layer. The rate of extinction of the layer is related to the photocatalytic activity of the substrate.

The conjugated organosilane is trichlorosilane: octadecyltrichlorosilane (OTS). Bonding is performed by dipping.

The test rig consisted of a turntable rotating around 1 to 6 low pressure UVA lamps. The test specimen to be evaluated is placed on a turntable, and the face of the test specimen is evaluated on the UVA radiation side. Depending on the position of the switch and the number of switched on lamps, each test specimen was 0.5 W/m² to 50 W/m²It receives UVA radiation that changes to For Examples 1, 2, 3, 8 and 9, the radiation power was 1.8 W/m² is selected, and for Examples 4 to 7, the radiation power is 0.6 W/m² is selected as

The time between each contact angle measurement varies between 20 minutes and 3 hours depending on the photocatalytic activity of the test specimen under consideration. Measurements are performed using a goniometer.

Before spinning, the glasses exhibit an angle of approximately 100°. The layer is observed to break when the angle is less than 20° after being radiated.

Each tested test specimen is characterized as an average rate of decay of the layer, given in nanometers per hour, that is to say that the thickness of the deposited organosilane layer is less than or equal to 20° (disappearance time of the organosilane layer). It is divided by the emission time making it possible to reach a fixed value.

All the preceding examples passed test 1, that is to say that when a coating is sprayed onto a substrate, the substrate becomes completely transparent, whereas a layer with high visibility for agglomeration is deposited on the uncoated substrate. .

The above examples were subjected to Test 2: The coated substrate, after exposure to UVA radiation, exhibits a contact angle of 5° or less to water and DOP. In contrast, exposed glass under the same conditions exhibited a water contact angle of 40° and a DOP contact angle of 20°.

The results of the substrates coated according to the above examples in Test 3 are combined in the table below.

<tables id="1"><table id="1" cols="2"><row><entry he="370" wi="4104" cb="1" ce="1" rb="1" re="1" al="l">Board</entry><entry he="370" wi="6092" cb="2" ce="2" rb="1" re="1" al="l"> 1.8 W/m²Test 3 of wetting with UVA (nm/h)</entry><row><entry he="370" wi="4104" cb="1" ce="1" rb="2" re="2" al="l"> Example 1 (TiO on exposed glass)₂)</entry><entry he="370" wi="6092" cb="2" ce="2" rb="2" re="2" al="l"> 0.03</entry><row><entry he="370" wi="4104" cb="1" ce="1" rb="3" re="3" al="l"> Example 2 (SnO₂: TiO on F₂)</entry><entry he="370" wi="6092" cb="2" ce="2" rb="3" re="3" al="l"> 0.1</entry><row><entry he="370" wi="4104" cb="1" ce="1" rb="4" re="4" al="l"> Example 3 (TiO on SiOC₂)</entry><entry he="370" wi="6092" cb="2" ce="2" rb="4" re="4" al="l"> 0.2</entry><row><entry he="370" wi="4104" cb="1" ce="1" rb="5" re="5" al="l"> Example 8 (TiO on 50 nm SiOC₂)</entry><entry he="370" wi="6092" cb="2" ce="2" rb="5" re="5" al="l"> 5</entry><row><entry he="370" wi="4104" cb="1" ce="1" rb="6" re="6" al="l"> Example 9 (TiO on 50 nm SiOC₂)</entry><entry he="370" wi="6092" cb="2" ce="2" rb="6" re="6" al="l"> 5</entry><row><entry he="370" wi="4104" cb="1" ce="1" rb="7" re="7" al="l"> exposed glass</entry><entry he="370" wi="6092" cb="2" ce="2" rb="7" re="7" al="l"> 0</entry></row></row></row></row></row></row></row></table></tables>

<tables id="2"><table id="2" cols="2"><row><entry he="370" wi="4104" cb="1" ce="1" rb="1" re="1" al="l">Substrate (CVD)</entry><entry he="370" wi="6092" cb="2" ce="2" rb="1" re="1" al="l"> 0.6W/m²Test 3 of wetting with UVA (nm/h)</entry><row><entry he="370" wi="4104" cb="1" ce="1" rb="2" re="2" al="l"> Example 4 (TiO on exposed glass₂)</entry><entry he="370" wi="6092" cb="2" ce="2" rb="2" re="2" al="l"> &lt; 0.05 nm/h</entry><row><entry he="370" wi="4104" cb="1" ce="1" rb="3" re="3" al="l"> Example 5 (TiO on SiOC₂)</entry><entry he="370" wi="6092" cb="2" ce="2" rb="3" re="3" al="l"> 4</entry><row><entry he="370" wi="4104" cb="1" ce="1" rb="4" re="4" al="l"> Example 6 (TiO on exposed glass)₂)</entry><entry he="370" wi="6092" cb="2" ce="2" rb="4" re="4" al="l"> 9</entry><row><entry he="370" wi="4104" cb="1" ce="1" rb="5" re="5" al="l"> Example 7 (TiO on SiOC₂)</entry><entry he="370" wi="6092" cb="2" ce="2" rb="5" re="5" al="l">19.5</entry></row></row></row></row></row></table></tables>

From the above tables, it can be seen that the presence of sub-layers, particularly SiOC, is its barrier effect on alkali metals and alkaline-rare earth metals that can migrate from the glass, with TiO₂promotes the photocatalytic activity of the coating comprising (compare Examples 4 and 5 or 6 and 7).

Also, TiO₂It is observed that the thickness of the coating comprising₂For the coating, a better photocatalytic effect is obtained.

Indeed, TiO obtained by CVD₂It can be observed that the coating exhibits the most improved crystallization, with crystallites on the order of 20-30 nm. Example 6 (TiO₂The photocatalytic activity of 65 nm) in Example 4 (TiO₂It can be seen that it is significantly larger than that of only 15 nm of Therefore, TiO which is at least twice as large as the average diameter of the crystallites contained in the coating.₂Providing a coating thickness can be beneficial. Optionally, as in the case of Example 5, the "first" TiO from layer₂TiO coated with a thin thickness, with a suitable thickness to promote the crystal growth of as far as possible.₂, so it is possible to make a choice to use a sub-layer of suitable properties.

TiO₂It can be observed that the crystallization is somewhat less improved compared to coatings deposited by CVD and other techniques. However, here again everything is still a matter of trade-off: less improved crystallization and preferentially low photocatalytic activity can be " rewarded" can get Besides, the use of suitable sub-layers or TiO₂The addition of can make it possible to improve the photocatalytic behavior, if necessary.

Further, from the comparison of Examples 2 and 3, it was confirmed that the properties of the sub-layers influence the crystallization morphology and, in fact, the photocatalytic activity of the coating.