Glass-, ceramic- or glass-ceramic-based substrate, monolithic multilayer glazing unit, use of the substrate and process for its manufacture

Substrate based on glass, ceramics or glass ceramics, monolithic multilayer unit, use of substrate and method of production of substrate

Technical field

The invention relates to substrates having a photocatalytic coating based on glass, ceramics or glass ceramics, most often based on glass, in particular transparent substrates provided with coatings having photocatalytic properties, which substrates serve for the production of window panes intended for various applications, such as utility glasses , window glass of vehicles or buildings. Also encompassed by the present invention is a monolithic multi-layer unit of the double glazing type or laminate type, the use of a substrate for the manufacture of self-cleaning, anti-condensation and / or glazing-repellent impurities, and a method of making the substrate.

BACKGROUND OF THE INVENTION

At present, there is an increasing effort to extend the spectrum of use of window panes by applying thin layers applied to the surface of the panes, which give them specific properties depending on the desired application. Optical layers, for example antireflective layers, are known from the prior art, which are composed of several layers alternately arranged with high and low refractive indices. Thin electrically conductive layers, for example based on metal or additive metal oxide, may be used for the antistatic or 'de-icing' heating function. For thermal function, for example for low emissivity or antisolar layers, thin layers of silver type metal or nitride or metal oxide based layers may be used. If the aim is to achieve a water-repellent effect, layers of a hydrophobic nature can be used, for example based on fluorinated organic silane.

However, there is still a need for a substrate, in particular a window pane, which can be termed & quot; dirt-removing & quot ;, i.e., a window pane, which has permanent appearance and surface properties over time, and which particularly allows minimal cleaning and / or better visibility that it achieves the gradual removal of impurities which gradually deposit on the surface of the substrate, in particular impurities of organic origin, such as fingerprints or volatile organic compounds present in the atmosphere, or even steam impurities.

It is known in the art that certain metal oxide semiconductor materials are capable of initiating radical reactions that cause the oxidation of organic products by the radiation of an adequate wavelength. These materials are referred to as "photocatalytic" or "photoreactive".

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a photocatalytic coating on a substrate which exhibits a & quot; dirt-removing & quot; effect relative to the substrate and which can be manufactured by an industrial process.

SUMMARY OF THE INVENTION The present invention provides a glass, ceramic or glass ceramics substrate having at least one portion of at least one of its sides coated with a photocatalytic property comprising at least partially crystallized titanium oxide, characterized in that at least one thin film forming layer is arranged below said coating. a barrier against the migration of alkali metals from the substrate.

Preferably, the crystallized titanium oxide in the substrate is in the form of anatase, rutile or a mixture of anatase and rutile. In another preferred embodiment, the titanium oxide is a crystalline titanium oxide having a degree of crystallization of at least 25%, in particular in the range of 30 to 80%. According to a further preferred embodiment, the crystallized titanium oxide is in the form of crystallites of average size in the range of 1 to 50 nm, in particular in the range of 10 to 40 nm.

Furthermore, a substrate is preferred wherein the coating comprises additives capable of enhancing the photocatalytic effect caused by titanium oxide, in particular by increasing the absorption band of the coating and / or increasing the number of charge carriers by doping the crystal oxide grid or doping the surface of the coating and / or increasing the efficiency and kinetics of photocatalytic reactions. coating at least a portion of the coating with a catalyst. According to another preferred embodiment, the crystalline titanium oxide grid is doped, in particular by means of at least one of niobium, tantalum, iron, bismuth, cobalt, nickel, copper, ruthenium, cerium, molybdenum. According to another preferred embodiment, the titanium oxide or coating is generally covered with a catalyst, in particular in the form of a thin layer of noble metal of the platinum, rhodium, silver, palladium type.

Further preferred is a substrate in which the coating comprises metal elements, particularly in particulate form, to enlarge the absorbent strip, the elements being selected from tin, cadmium, tungsten, cerium or zirconium.

A substrate is further preferred wherein the doping of the titanium oxide surface or the coating containing it is accomplished by coating at least a portion of the coating with a metal oxide or metal salt layer, the metal being selected from iron, copper, ruthenium, cerium, molybdenum, bismuth, vanadium.

Further preferred in the present invention is a substrate according to any of the preceding embodiments, which is oleophilic.

Further preferred is a substrate according to any of the preceding embodiments, wherein the coating thickness is in the range of 15 nm to 1 micrometer, in particular in the range of 5 to 100 nm, preferably in the range of 10 to 80 or 20 to 50 nm.

Also encompassed by the present invention is a monolithic, multi-element, double-glazing or laminate-type unit having a & quot; dirt-repellent and / or anti-condensation & quot; effect comprising a substrate according to any of the above embodiments.

The present invention also relates to the use of a substrate according to any of the above embodiments for the manufacture of self-cleaning, anti-condensation and / or unclean-repellent glazing, wherein these traces of dirt are of organic and / or inorganic type, in particular glazing in double glazing, glazing for vehicles such as windshields, side and rear windows of cars, trains, airplanes or utility glazing such as aquarium glasses, shop showcases, greenhouses, interior furnishings for a flat or house, or a mirror, television screens, and stained glass with electrically controlled absorption.

The present invention also relates to a process for producing a substrate according to any one of the above embodiments, characterized in that the photocatalytic properties are applied by liquid-phase pyrolysis, in particular from a solution containing at least one organometallic precursor of titanium chelate type and / or alcoholate. titanium.

In a preferred embodiment of the process, the photocatalytic coating is applied by a sol-gel technique, a dip coating method, a closed cell coating, a cell coating coating, or a man-coating coating, or a laminate coating , from a solution containing at least one organometallic titanium precursor of the titanium alcoholate type.

. 7 .

According to a further preferred embodiment of the process, the photocatalytic coating is applied by gas-phase pyrolysis, by CVD, using at least one precursor of the titanium halide or organometallic compound type.

According to a further preferred embodiment of the process, the coating with photocatalytic properties is applied by vacuum technique, in particular by cathodic spraying.

For these processes, it is preferred that the coating with photocatalytic properties is applied in at least two successive steps. It is also preferred that the coating with photocatalytic properties after application is subjected to at least one heat treatment of the annealing type.

BRIEF DESCRIPTION OF THE DRAWINGS 15

The photocatalytic substrate of the present invention is illustrated in more detail in the accompanying drawings, which show:

Fig. 1: cross-section of a glass substrate coated with a coating according to the invention; Fig. 2: Diagram of a sol-gel coating method called "dip-coating"; Fig. 3: Diagram of a closed coating method Fig. 4: Scheme of the spray-coating method, Fig. 5: Scheme of the laminar coating method.

DETAILED DESCRIPTION OF THE INVENTION

Accordingly, it is an object of the present invention to provide a glass, ceramic or glass ceramic substrate, most commonly a transparent glass substrate having at least a portion of at least one of its sides with a photocatalytic coating comprising titanium oxide at least partially crystallized. Preferably, the titanium oxide crystallizes "in situ" during the coating process.

Titanium oxide is one of the semiconductors which, by exposure to radiation in the visible or ultraviolet range, degrade organic products that deposit on their surface. For this reason, this titanium oxide has been chosen for the production of "dirt-repellent" window panes. Moreover, this oxide has good mechanical and chemical resistance: for its long effectiveness it is very important that the coating retains its integrity, even if it is directly exposed to various aggressive effects, especially during the assembly of window panes on a construction site (building) or production line (vehicles), which involves repeated handling, performed by mechanical or pneumatic tools, but also at the point of application where it is subject to the risk of abrasion (wipers, abrasive rag) and contact with aggressive chemicals (atmospheric pollutants of SO₂, cleaning products, etc.).

In addition, the selection focuses on titanium oxide which is at least partially crystallized since it has been shown to be much more effective in photocatalytic properties than amorphous titanium oxide. Preferably, the oxide is crystallized in the form of anatase, rutile or in the form of anatase and rutile, wherein the degree of crystallization is at least 25%, most preferably about 30 to 80%, especially near the surface (this property is primarily a surface property). (The degree of crystallization refers to the mass amount of crystallized TiO₂ based on the total weight of TiO₂ in the coating).

-3 GB 299321 Β6

Especially in the case of anatase crystallization, it was observed that the orientation of TiO? Growing on the substrate had an effect on the photocatalytic efficiency of the oxide, and there is a favorable orientation (1,1,0) that strongly supports photocatalysis.

The coating is preferably made so that the crystallized titanium oxide contained therein is at least near the surface in the form of "crystallites", i.e. in the form of single crystals having an average size in the range of 0.5 to 100 nm, with preferably 1 to 50 nm, in particular 10 to 40 nm, most preferably 20 to 30 nm. In this dimensional range, titanium oxide has an optimal photocatalytic effect, probably because crystallites of this size form a considerable active surface.

The titanium oxide coating can be obtained in several ways, as detailed below:

decomposition of titanium precursors (pyrolysis technique: liquid phase pyrolysis, solid phase pyrolysis (powder), gas phase pyrolysis called VCD (Chemical Vapor Deposition), sol-gel techniques: dip coating, cell coating , etc.). vacuum techniques (reaction or non-reaction cathodic sputtering).

The coating may also contain at least one other type of inorganic material in addition to crystallized titanium oxide, in particular in the form of an amorphous or partially crystallized oxide, for example silicon oxide (or a mixture of oxides), titanium oxide, tin oxide, zirconium oxide or aluminum oxide. This inorganic material may also contribute to the photocatalytic effect of crystalline titanium oxide by itself representing a certain, albeit weak, photocatalytic effect with respect to crystalline TiO₂such as tin oxide or amorphous titanium oxide.

A "mixed" oxide layer which thus combines at least partially crystallized titanium oxide with at least one other oxide may be significant from an optical point of view, especially when the other oxide (s) have a refractive index lower than that of TiO₂By reducing the "total" refractive index of the coating, it is possible to change the reflection of the light of the coated substrate, in particular to reduce this reflection. This is the case, for example, when it is a TiO layer₂/ Al₂O₃, the manufacturing process of which is described in European patent EP 0 465 309, or in the case of a TiO layer₂/ SiO₂. However, it is necessary that the coating contains a sufficient amount of TiO₂ to maintain significant photocatalytic activity. By this sufficient amount is meant preferably the coating contains at least 40% by weight, in particular at least 50% by weight of TiO.₂ based on the total weight of the oxide or oxides in the coating.

It is also possible to coat the coating according to the invention with an oil-and / or hydrophobic layer, stable or resistant to photocatalysis, for example based on the fluorinated organic silane described in U.S. Patents 5,368,892 and 5,389,427 or on perfluoroalkyl silane described in French patent application FR 94/08734 of 13. No. 2,722,493, corresponding to the European patent EP 0 692 463, in particular based on a silane of the formula:

CFHCF 2 -CH 2 -SiXj in which:

n is from 0 to 12, m is from 2 to 5, and

X is a hydrolyzable group.

-4GB 299321 B6

In order to enhance the photocatalytic effect of the titanium oxide in the coating according to the invention, it is possible first to increase the absorption band of the coating by adding further particles to the coating, in particular metal particles and cadmium, tin, tungsten, zinc, cerium or zirconium.

It is also possible to increase the number of charge carriers by adding a crystalline titanium oxide grid by at least one of the following metallic elements: niobium, tantalum, iron, bismuth, cobalt, nickel, copper, ruthenium, cerium, molybdenum.

The additivation can also be carried out only by the additivation of the surface of the titanium oxide or of the entire coating, the additive being carried out by coating at least a portion of the coating with a metal oxide or salt layer, selected from iron, copper, ruthenium, cerium, molybdenum, vanadium; bismuth.

Finally, the photocatalytic phenomenon may be enhanced by increasing the efficiency and / or kinetics of the photocatalytic reactions by coating the titanium oxide or at least a portion of the coating containing it with a thin layer of noble metal of the platinum, rhodium, silver or palladium type.

This catalyst, applied, for example, by a vacuum technique, allows to increase the number and / or duration of the existence of radical particles formed by titanium oxide, and in this way to promote chain reactions which lead to the decomposition of organic substances.

Quite surprisingly, the coating according to the invention has in fact not one but two distinct properties when exposed to the respective radiation in a visible and / or ultraviolet region such as sunlight: due to the presence of photocatalytic titanium oxide, as shown previously, promotes the gradual removal of organic impurities, depending on their accumulation, by causing them to degrade by radical oxidation. Mineral impurities are not degraded in this way, so they remain on the surface and, to a certain degree of crystallization, are partially easily removed, since once adhered organic reagents are degraded by photocatalysis, they no longer have any reason to adhere to the surface.

The self-cleaning coating of the present invention also has an outer surface preferably of substantially hydrophilic and / or oilophilic nature, which causes three very advantageous effects:

the hydrophilic character permits excellent wetting of the surface with water which can deposit on the coating. When water condensation occurs, a thin continuous film of water, which is completely transparent, forms on the surface of the coating, instead of the deposition of water droplets in the form of vapor that limits visibility. This 'anti-condensation' effect has been particularly proven by measuring the contact angle with water less than 5 ° after light exposure, and by leaving water, especially rain on a surface not coated with a photocatalytic layer, numerous droplets remain on the surface. evaporation leaves aesthetic and disturbing spots of mineral origin. The surface exposed to the ambient air is quickly covered with a layer of dirt that limits its wetting with water. These impurities combine with other impurities, especially inorganic impurities (crystallization, and the like), which come from the atmosphere in which the window pane is wetted. In the case of a photoreactive surface, these inorganic impurities are not directly degraded by photo45 catalysis. In fact, they are largely removed due to the hydrophilic character created by photocatalytic activity. This hydrophilic character causes a perfect spread of raindrops and thus prevents inorganic stains. In addition, the other inorganic impurities present on the surface with the water film are washed off or dissolved in the case of crystallization, and thus largely removed. In this way, the effect of "removing inorganic contaminants" is achieved;

at the same time as the hydrophilic character, the coating may have an oilophilic character which allows the "wetting" of organic impurities which, as in the case of water, tend to settle on the coating in the form of a continuous film, less visible than well-localized spots. In this way the "organic impurity removal" effect is achieved, which takes place in two time planes "already

At the moment when it settles on the coating, the dirt is less visible. It then gradually disappears by radical degradation induced by photocatalysis.

The coating may be applied to a more or less smooth surface. A certain degree of surface roughness may be advantageous:

allows a greater active photocatalytic surface to be obtained, thereby leading to greater photocatalytic activity;

has a direct effect on wetting. Roughness promotes wetting properties. A flat hydrophilic surface will be the more hydrophilic the rough it is. "Roughness" here means both the surface roughness and the roughness caused by the porosity of the layer in at least one part of its thickness.

The foregoing effects will be all the more apparent as the surface becomes more porous and rugged, resulting in a superhydrophilic effect of rough photoreactive surfaces. However, a very pronounced roughness can be disadvantageous since it promotes incrustation, accumulation of impurities and / or causes a degree of optically unacceptable blur.

In view of the above, it has proven advantageous to adapt the TiO coating process₂ so that their roughness is in the range of about 2 to 20 nm, preferably 5 to 15 nm, which roughness is determined by atomic force microscopy, by measuring the standard deviation (referred to as "Root Mean Square" or RMS) over an area of ​​1 micrometer square . Coatings with such roughness values ​​have a hydrophilic character, which is manifested by a contact angle with water which may be less than 1 °. It has also been stated that it is advantageous to promote a certain porosity over the entire thickness of the coating. If the coating consists of TiO only₂Preferably, it has a porosity in the range of 65 to 99%, especially 70 to 90%, the porosity being defined indirectly herein as a percentage of the theoretical relative density of TiCl 2, which is about 3.8. Such porosity can be obtained, for example, by coating with a sol-gel technique which involves the decomposition of organometallic materials: in which case, in addition to one or more organometallic precursors, an organic polyethylene glycol PEG type polymer may be added to the solution; increases a certain degree of porosity over the entire layer thickness.

The thickness of the coating according to the invention varies, preferably in the range from 5 nm to 1 micrometer, in particular from 5 to 100 nm, most preferably in the range from 10 to 80 nm, or from 20 to 50 nm. The choice of thickness may in fact depend on various parameters, in particular on the desired application of a pane of the window type, or on the size of TiO crystallites₂ in the coating or in the presence of a high proportion of alkali metals in the substrate.

Between the substrate and the coating of the invention, one or more other thin layers may be provided with an additional function, or alternatively with a different function with respect to the properties of the coating. These may in particular be layers with an antistatic, thermal or optical function or layers supporting the growth of TiO crystals₂ in the form of anatase or rutile, or a barrier-forming layer for the migration of certain elements from the substrate, especially the alkali metals, especially the sodium ion barrier, if the substrate is glass.

It may also be desirable to have a set of "anti-reflective" layers in which thin layers with high and low refractive indices alternate, the coating of the invention forming the last layer of the set. In this case, it is preferred that the coating has a relatively low refractive index, which is the case when the coating is a mixed titanium-silicon oxide.

The antistatic or thermal layer (heated layer provided with power supply, low emissivity layer, antisolic layer, and the like) can most often be selected from conductive materials of a metallic nature, such as silver or additive metal oxide type such as indium tin oxide doped with ITO tin, tin oxide doped with SnO2: F, or antimony SnO₂: Sb, or zinc oxide doped with indium ZnO: In, fluorine ZnO: F, aluminum ZnO: Al or tin ZnO: Sn. They may also be metal oxides with a substoichiometric oxygen content, for example SnO₂__x or ZnO_{2 x}where x <2.

-6GB 299321 Β6

The antistatic layer preferably has a surface electrical resistance value in the range of 20 to 1000 ohms / square. This layer can be provided with power supplies for polarization (the input voltage is, for example, in the range of 5 to 100 V). This controlled polarization makes it possible, in particular, to prevent the deposition of dust of the order of millimeters, which is deposited on the surface, in particular of dry dust adhering to the electrostatic effect, the dust being repelled by a sudden change in polarization of the layer.

The thin film with the optical function may be selected to reduce light reflection and / or render a more neutral color when light is reflected from the substrate. In this case, preferably the refractive index has a value in the range between the refractive index of the substrate and the refractive index of the coating and an optically suitable thickness, and may be formed of an oxide or a mixture of an oxide of the aluminum oxide type A1₂O₃, SnO₂, indium oxide In₂O₃ oxycarbide or silicon oxynitrile. In order to maximize color weakness upon reflection, it is preferred that the rigid layer has a refractive index close to the square root of the product of the squares of the refractive index of the two materials adjacent to it, i.e. the substrate and coating of the invention. At the same time, it is preferable to select its optical thickness (i.e., the product of its geometric thickness and its refractive index) close to lambda / 4, wherein lambda is approximately equal to the mean wavelength in the visible region, especially in the range of 500 to 550 nm.

This thin layer with an alkali metal barrier function can be selected particularly from the group of substances based on silicon oxide, nitride, oxynitride or oxycarbide, or fluorine-containing aluminum oxide₂O₃: F, optionally based on aluminum nitride. This layer has proven useful in the case of a glass substrate, since migration of sodium ions into the coating of the invention may, under certain conditions, impair photocatalytic properties.

In addition, the nature of the substrate or backing layer has the additional advantage of: it can promote crystallization of the deposited photocatalytic layer, particularly in the case of CVD deposition,

During TiO deposition₂ thus supporting the bottom layer of crystallized SnO by CVD₂: F TiO growth₂especially in the form of rutile, especially at deposition temperatures in the range of 400-500 ° C, while the soda-lime glass surface or silicon oxycarbide backing rather promotes anatase growth, especially at deposition temperatures in the range of 400-600 ° C.

All of these thin or present layers may be applied in a known manner by vacuum cathodic spraying methods or other thermal decomposition methods, for example by solid, liquid or gaseous pyrolysis. Each of the aforementioned layers may have several functions, or it is possible to apply the individual layers to each other.

The present invention also provides "dirt-removing" window panes (organic and / or inorganic soils) and / or "anti-condensation" panes, which are monolithic, multi-insulated double-glazed window or laminated assemblies containing the above described coated substrates.

Accordingly, the present invention is directed to the manufacture of glass, ceramic or glass ceramic products, in particular to the manufacture of "self-cleaning" window panes. These panes may advantageously serve as window panes of buildings, for example double glazed assemblies (in which case the coating may be placed on the "outer" and / or "inner" side, i.e. on side 1 and / or side 4). This is of particular interest for poorly accessible window panes and / or window panes that need very frequent cleaning, such as roof panes, airport panes, and the like. It may also be a vehicle window pane where visibility is an essential safety criterion. In this case, the coating may be located on the windshield, side or rear windows of the automobile, in particular on the inside of the windows. This coating may prevent condensation and / or remove traces of fingerprint, nicotine or organic material, which may be a volatile plasticizer that is released from the plastic that is coating the interior of the vehicle, especially the plastic from the dashboard ( sometimes referred to as the English term

-7EN 299321 B6 fogging). Other vehicles, such as airplanes or trains, may also use these coated panes of the invention.

There are numerous other applications, especially aquarium glasses, shop showcases, greenhouses, porches, glass used in the interior of a home or house, but also mirrors, television screens, optics or architectural materials such as façade, tiling, roofing materials such as tiles , etc.

The invention also allows to confer on these known products new functions, for example ultraviolet protection, a "dirt-repellent" effect, as well as bactericidal, antireflective, antistatic, antimicrobial and the like.

Another interesting application of the coating according to the invention is to combine the formation of an electrically controlled variable absorption sheet of the electrochromic stained glass type, with liquid-crystal stained glass, optionally with a two-color dye, suspended particle stained glass, viologene stained glass and the like. All of these glazing assemblies, or stained glass, are generally comprised of a series of transparent substrates between which the & quot; active & quot; elements are disposed, and the coating can therefore preferably be placed on the outside of at least one of these substrates.

Especially in the case of electro-chromed stained glass, when stained, its absorption causes a certain heating of the surface, which in practice leads to an acceleration of the footocatalytic decomposition of the carbonaceous substances depositing on the coating according to the invention. A more detailed description of the structure of an electrochromic glazing panel or stained glass is given in patent application EP-A-0 575 207, in which a double layered electrochromic stained glass is described, wherein the coating according to the invention can advantageously be placed on page 1.

The present invention also provides various methods of obtaining the coating of the invention. This may be a pyrolysis-type deposition technique, which is interesting in that it allows a particularly smooth coating to be applied directly to the float glass web when a glass substrate is used.

The pyrolysis can be carried out in solid phase from a powdered precursor or precursors of the organometallic compound type or organometallic compounds type.

The pyrolysis may be carried out in liquid phase from a solution containing an organometallic precursor of titanium chelate type and / or titanium alcoholate. These precursors are mixed with at least one other organometallic precursor. A more detailed description of the nature of the titanium precursor or deposition conditions is given, for example, in French patent FR 2 310 977 and in European patent EP 0 465 309.

The pyrolysis can also be carried out in the gas phase, in which case the pyrolysis process is also referred to as CVD (Chemical Vapor Deposition), using at least one precursor of the titanium halide type, e.g. TiCl₄ or titanium alcoholate of the titanium tetraisopropylate type, Ti (OiPr)₄. In addition, the crystallization of the layer can be controlled by a particular type of underlayer as previously mentioned.

The coating may also be applied by other methods, in particular by methods combined with sol-gel methods. There are various methods of application, such as "dip coating", also called dip-coating, or closed cell application, called "cell-coating". It may also be a spraycoating method, or a laminate laminate may be applied, the latter being described in detail in the international publication WO 94/01598. All these deposition methods generally use a solution comprising at least one organometallic precursor, in particular of the titanium alcoholate type, which decomposes thermally after coating the substrate with a solution on one or both sides thereof.

-8EN 299321 B6

In addition, it may be advantageous to apply this coating, whatever the technique of application is chosen, not at one time, but in at least two successive stages, since this seems to support the crystallization of titanium oxide over the entire thickness of the coating if relatively strong coating.

It is likewise advantageous to subject the coating with photocatalytic properties after annealing to a heat treatment of the annealing type. This heat treatment is necessary when using the sol-gel coating method or when laminating a laminate treatment to decompose the organometallic precursor or precursors to oxide once applied to the substrate and to improve abrasion resistance, which is not the case. for a pyrolysis technique wherein the precursor decomposes once it comes into contact with the substrate. In the first and second cases, however, the post-deposition heat treatment if titanium dioxide TiO has already formed₂, improves its degree of crystallization. In addition, the treatment temperature selected may make it possible to better control the degree of crystallization and the nature of the oxide crystals, whether in the form of anatase and / or rutile.

However, in the case of a soda-lime glass substrate, multiple and prolonged cooling may promote a reduction in photocatalytic activity caused by too much migration of alkali metals from the substrate to the photoreactive layer. This risk can be avoided by using a layer with a barrier layer function applied between the substrate if it is a standard glass and a coating, or by choosing a glass substrate of the appropriate composition, or by choosing a soda-lime glass with a dealkalized surface.

DETAILED DESCRIPTION OF THE INVENTION

Further details and preferred features of the present invention will be set forth in the following examples, in which the photocatalytic substrate of the present invention and its preparation and application procedures, and its properties, are described in more detail and are not to be construed as limiting the invention. .

All of the following examples relate to the application of a coating 3, referred to as a "dirt-removing" titanium oxide coating, on a transparent substrate I, as shown only schematically in Figure 1.

Substrate I is a clear silica-soda-lime glass having a thickness of 4 millimeters and a length and width of 50 centimeters. It goes without saying that the invention is not limited to this specific type of glass. In addition, the glass need not be straight but can be domed.

Between the coating 3 and the substrate 1, a thin optional layer 2, either based on SiOC based on an oxycarbide SiO to form an alkali metal diffusion barrier and / or a light reflection reducing layer, or based on SnO fluorine additive₂F to form an antistatic layer and / or a layer with a low emissivity, possibly with a slightly increased low emissivity, and / or a color neutralizing layer, especially in light reflection.

Examples 1 to 3

Examples 1 to 3 relate to coating 3 which is applied by liquid-phase pyrolysis. The deposition can be carried out continuously using an adapted distribution nozzle which is positioned transversely to the axis of movement of the float glass ribbon above the strip, precisely at the exit of the float glass bath. In these examples, a discontinuous method was used using a mobile nozzle placed against substrate I, already divided into a predetermined portion, the substrate first being heated in an oven at 400 to 650 ° C and then moving at a constant rate below the nozzle discharging a suitable solution.

- 9 GB 299321 B6

Example 1

In this example, optional optional layer 2 was not used. Coating 3 was applied using a solution containing two organometallic titanium precursors, titanium diisopropoxydiacetylacetonate and titanium tetraoctylene glycolate dissolved in a mixture of two solvents, ethyl acetate and isopropanol.

It should be noted that other precursors of the same type are also useful, in particular other titanium chelates of the titanium acetylacetonate type, titanium methylacetoacetate, titanium ethylacetoacetate, optionally titanium triethanolamine or titanium diethanolamine.

Once substrate 1 reached the desired oven temperature, which is approximately 500 ° C, the substrate was passed under a nozzle through which the mixture was sprayed at ambient temperature with compressed air.

A TiO layer was thus obtained₂ The thickness of this layer could be controlled by the speed of movement of the substrate under the nozzle and / or the temperature of the substrate. This layer was partially crystallized as anatase.

This layer had excellent mechanical resistance. Its abrasion resistance when performing the appropriate tests was comparable to that observed for the surface of the glass itself.

The layer thus obtained is wettable and wettable. This layer shows no haze: the diffused light transmittance of the coated substrate is less than 0.6% (measured with a standard light source D₆5 at 560 nm).

Example 2

The procedure of this example was carried out in the same manner as in Example 1, except that an SnO layer 2 was inserted between the substrate I and the coating 3.₂73 F. This layer was obtained by pyrolysis of DBTF difluordibutyltin powder. This layer can also be obtained by liquid or gaseous pyrolysis, in a manner known per se, as described in European patent application EP-AO 648 196. In the gaseous phase it was particularly possible to use a mixture of monobutyltrichloridin and a fluorinated precursor, which may optionally be used together with fine. type H oxidizing agent₂O.

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

In the previous example 1, the coated substrate 1 assembled in a double stained glass so that the coating was on the side 1 (with another uncoated substrate V of the same material and the same size as the substrate 1, through an air layer of 12 millimeters thickness) 26% and a saturation value at 6.8% permeability.

According to Example 2, the color saturation at reflection (golden color) was only 3.6% and the color saturation at transmittance 1.1%.

SnO bottom layer₂F has given the substrate antistatic properties due to its electrical conductivity, while also having a beneficial effect on the colorimetry of the substrate by making it significantly more neutral in its transmittance and reflection color, with the color induced by the presence of titanium oxide coating 3 having a relatively increased refractive index. This layer could be polarized by applying a suitable electrical voltage in order to reduce dust deposits of relatively large dimensions, of the order of millimeters.

- 10GB 299321 B6

Moreover, this backing layer reduced the diffusion of the alkali metals in the photocatalytic TiO layer₂. This improved photocatalytic activity.

Example 3

The same procedure was carried out as in Example 2 except that a silicon oxycarbide-based layer 2 with a refractive index of about 1.75 and a thickness of about 50 nm was inserted between the substrate and the coating 3, which layer can be produced by chemical vapor deposition (CVD method) using a SiH mixture₄ and ethylene diluted with nitrogen as described in European patent application EP-A 0 518 755. This layer is particularly effective for preventing the diffusion of alkali metals (Na⁺, K⁺) and alkaline earth metals (C⁺⁺) from both the substrate and the coating 3, thereby significantly improving the photocatalytic activity. Because this layer had as much as SnO₂The refractive index F between the refractive index of the substrate (1.52) and the refractive index of coating 3 (about 2.30 to 2.35) also made it possible to reduce the color intensity of the substrate at both reflection and transmittance, and to reduce the light reflection value Rl overall of this substrate. The following Examples 4 to 7 relate to CVD deposition.

Examples 4 to 7

Example 4

This example relates to the coating of the coating 3 directly to the substrate by the CVD method, by means of a standard nozzle, for example as described in the above-cited European patent application EP-A 0 518 755. Organometallic compounds or metal halides were used as precursors. Titanium tetraisopropylate was chosen as an organometallic compound, which is advantageous for its high volatility and a wide range of operating temperatures ranging from 300 to 650 ° C. The deposition in this case was carried out at approximately 425 ° C with a TiO thickness₂ was 15 nm.

It is also possible in this case to use tetraethoxytitanium Ti (O-Et)₄wherein TiCl may be selected as the halide₄.

Example 5

The same procedure was used as in Example 4, except that there was a TiO layer₂ 15 nm thickness was applied not directly to the glass but to a 50 nm SiOC backing layer which was applied in the same manner as in Example 3.

Example 6

The same procedure was used as in Example 4, except that the thickness of the TiO layer₂ was 65 nm.

-11GB 299321 Β6

Example 7

The same procedure as in Example 5 was used except that the thickness of the TiO 2 layer was 60 nm.

Based on the results obtained in Examples 4 to 7, it was found that the coated substrates had good mechanical resistance to abrasion tests. In particular, no loss of TiO layer was observed₂.

Example 8

In this example, a technique belonging to the sol-gel method was used, employing a dip-coating method based on Figure 2. The substrate 1 was immersed in a liquid solution 4 containing the respective coating precursor (s) 3, and was then withdrawn therefrom at a controlled rate by the motor unit 5, and the withdrawal rate selection allowed to adjust the thickness of the solution adhering to the surface from both sides of the substrate. the thickness of the coatings after the thermal treatment of the substrate carried out to evaporate the solvent while decomposing the precursors or precursors to oxide.

For coating 3, a solution 4 containing either titanium tetrabutoxide Ti (O-Bu) 4 stabilized with diethanolamine DEA in a molar ratio of 1: 1 in an ethanol type solvent at a concentration of 0.2 mole tetrabutoxide per liter of ethanol, or a mixture of precursors and solvents described (Another precursor, for example, titanium dibutoxydietanolamine) may also be used).

These substrates may also comprise SiOC backing layers.

After extraction from each of the solutions 4, the substrates 6 were heated at 100 ° C for 1 hour, then at 550 ° C for about 3 hours with gradual temperature rise.

On each side of the substrate, a coating 3, in both cases consisting of TiO, was obtained₂ well crystallized in the form of anatase.

Example 9

In this example, a closed cell coating technique called "cell-coating" was used, the principle of which is illustrated in Figure 3. This is to create a narrow space delimited by two substantially parallel surfaces 6, 7 and two closure joints 8, 9 with at least one the surfaces 6, 7 are formed by the surface of the substrate 6 to be treated. Thereafter, the space was filled with solution 4 of the coating precursors, and this solution 4 was collected in a controlled manner, for example by means of a peristaltic pump 10, to form a wetting meniscus leaving a film of solution 4 on the substrate surface.

Room 5 was then allowed to dry for at least the time necessary. The film was cured by heat treatment. The advantage of this technique over dip-coating is that it is possible to process only one side of the substrate 6 and not both at the same time if no masking system has been used.

The substrates 6 contained SiOC thin-film layers 2.

CZ 299321 Β6

In the procedure of Example 6, the appropriate solutions 4 described in Example 8 were used. the same heat treatments were then carried out.

The coating 3 had good mechanical resistance.

In MEB (scanning electron microscopy), the effect of a field in the form of "grains" of single crystals with a diameter of approximately 30 nm was apparent. The roughness of this coating resulted in improved wetting properties compared to a non-rough coating.

The same solutions 4 could also be used for coating by means of the spray-coating method as shown in Figure 4, where solution 4 is sprayed in the form of a veil against the static substrate I, or by laminar coating, such as this is shown in Figure 5. In the latter case, the substrate 11, maintained by vacuum suction on the stainless steel and Teflon carrier 11, was passed over a container 12 containing a solution in which the grooved cylinder 14 was partially submerged, and then the system consisted of the container 12 and the cylinder 14 the mask 13 prevented the solvent from evaporating too much from solution 4. A more detailed description of the latter method can be found in the above-cited international patent application WO 94/01598.

In order to characterize the coatings and to evaluate their "anti-condensation" and "soil-removing" efficacy, tests were performed on substrates obtained according to the preceding examples.

* Test 1: This test concerned the condensation aspects. It consisted in monitoring the effects of photocatalysis and coating structure (hydroxyl content, porosity, roughness) on wetting. If the surface was photoreactive, the carbonaceous microscopic impurities that deposited on the coating were continuously degraded and the surface became progressively hydrophilic, thus having an anti-condensation character. In this case, it was also possible to make a quantitative estimate by rapidly heating the coated substrate which had been placed in the cold, or simply blowing the substrate and observing for condensation, if any, and then measuring the time required to remove it.

* Test 2: This is an estimate of the hydrophilicity and oiliness of the coating surface 3, compared to the glass surface alone, by measuring the contact angles of water droplet and DOP (dioctyl phthalate) droplet on their surface after the substrates were left under ambient atmosphere for one week illuminated in the dark and then exposed to UVA for 20 minutes.

* Test 3: consists of applying a layer of organic silane to the test substrate and irradiating it with UVA in such a way that the layer is degraded by photocatalysis. Because the organic silane modified the wetting properties, the measurement of the contact angle of this substrate with water during irradiation indicated the degradation state of the deposited layer. The rate of removal of this layer is related to the photocatalytic activity of the substrate.

The graft organic thickener used was trichlorosilane: octadecyltrichlorosilane (OTS). The grafting was carried out by dip coating.

The tester was a turntable that rotated around 1 to 6 low pressure UVA lamps. The test samples were placed on the turntable facing the UVA irradiation surface. Depending on the position and number of lamps on, each test sample was subjected to UVA irradiation, ranging from 0.5 to 50 W / m². For Examples 1, 2, 3, 8 and 9, the irradiation intensity was selected

1.8 W / m², for Examples 4 to 7, the irradiation intensity was 0.6 W / m².

- 13 GB 299321 B6

The time between each measurement of contact angle with water ranged between 20 minutes and 3 hours, depending on the photocatalytic activity of the test sample. The measurements were performed using a goniometer.

Before irradiation, the glasses had a contact angle of approximately 100 °. A layer is considered to be distributed after irradiation if the contact angle is less than 20 °.

Each test sample was characterized by an average layer removal rate, expressed in nanometers per hour, i.e., the thickness of the deposited organosilane layer divided by the irradiation time, allowing a final steady state value of less than 20 ° (organosilane layer removal time).

The samples according to all the previous examples complied with the requirements of Test 1, i.e. if these coated substrates were blown off (breathed on), these substrates remained perfectly transparent while a visible condensation layer settled on the uncoated substrates.

The samples of the examples were subjected to Test 2 in which coated substrates exposed to UVA exposure had a contact angle preferably with a DOP of at most 5 °. On the contrary, the glass itself under the same conditions had a contact angle with water of 40 ° and a contact angle with DOP of 20 °.

The following table summarizes Test 3 results for substrates coated by the procedures of the previous examples.

Table

<td>Substrate</td><td>Wetting test 3 at 1.8 V / m² U, V, A. (nm / h)</td>

<td>Example 1 (Ti0₂ on the glass)</td><td> 0,03</td>

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

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

<td>Example 8 (Ti0₂ at 50 nm SiOC)</td><td> 5</td>

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

<td>Glass</td><td> 0</td>

<td>Substrate (CVD)</td><td>Wetting test 3 at 0.6 V / nm² AT_EIN_yAND. (in nm / h)</td>

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

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

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

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

- 14GB 299321 B6

Based on the results presented in this table, it can be concluded that the presence of the underlying undercoats, especially the SiOC layers, promotes the photocatalytic activity of the TiO-containing coating.₂ their barrier effect against alkali and alkaline earth metals that can migrate from glass (comparison of Examples 4 and 5 or 6 and 7).

It was further observed that the thickness of the TiO-containing coating₂ it also plays a role (comparison of Examples 1 and 3), with the thickness of the TiO coating₂ higher than the average size of single crystals or 'crystallites', the best photocatalytic effect was obtained.

In fact, it was observed that CVD coatings containing TiO₂have the most advanced crystallization, with crystallite sizes in the range of 20 to 30 nm. Thus, it can be stated that the photocatalytic activity of the sample obtained according to Example 6 (thickness of TiO 2)₂ 65 nm) is significantly higher than the activity of the sample obtained according to Example 4 (TiO thickness)₂ only 15 mm). It follows from the above that it is therefore advantageous to select the thickness of the TiO-containing coating₂ at least twice the mean diameter of the crystallites contained therein. Alternatively, it is possible to maintain a small thickness of the TiO-containing coating₂as in Example 5, but then selecting a backing layer of suitable material and thickness to promote the growth of TiO crystals as much as possible₂ from the "first" layer of crystallites.

Based on the results obtained with the samples of the above-described examples, it was observed that crystallization of TiO₂ was somewhat less advanced for non-CVD coatings. Here, therefore, there is still a compromise: less advanced crystallization and a priori lower photocatalytic activity can be "compensated" for example by using a less expensive or less complex deposition process. In addition, application of a suitable backing layer for TiO additives₂ they may, if necessary, allow the photocatalytic efficiency to be improved.

Comparing the results obtained in Examples 2 and 3, it was also verified that the nature of the underlying backing layer had an effect on the crystallization process and thus on the photocatalytic activity of the coating.