MXPA00008672A - Substrate with photocatalytic coating - Google Patents

Abstract

The invention concerns a method for obtaining a substrate (1) provided with a coating (3) with photocatalytic properties, crystallised particles of an oxide of metal A with photocatalytic properties being incorporated in said coating by means of a mineral binder (5) comprising at least an oxide of metal B also having photocatalytic properties in crystallised form and optionally at least an oxide of metal M devoid of photocatalytic properties and/or at least a silicon compound such as silicon oxide SiO2. It consists in depositing the coating (3) from liquid phase dispersions containing:said crystallised particles of metal A oxide;at least a precursor compound of the binder (5) of metal B oxide and optionally a precursor compound of metal M oxide and of the Si compound, in a relative proportion A(B + M + Si) by weight ranging between 60/40 and 40/60. The invention also concerns the resulting coated substrate and its various applications.

Description

SUBSTRATE WITH A PHOTOCATALYTIC COVER (Bl Description of the Invention The present invention relates to substrates provided with a photocatalytic coating, to the process for obtaining such a coating and to its various applications. This refers more particularly to coatings comprising semiconductor materials based on a metal oxide, especially a titanium oxide, which are capable, due to the effect of radiation of the appropriate wavelength, of initiating radical reactions causing the oxidation of organic products. The coatings thus make it possible to impart novel functionalities to the materials they cover, especially antifouling properties, fungicides and bactericides, and are optionally combined with hydrophilic properties, anti-fogging properties, optical properties, etc. A very wide variety of substrates can be considered, especially those used in the field of vehicles or buildings, such as glazing products, wall materials, "r veneers, preparation of roofs and floors, such as tiles, slate, slabs and paving stones, and more particularly any material used in the construction industry. These materials can thus be made of glass, metal, glass-ceramics, ceramics, cement brick, wood, stone or a material reconstituted from these natural materials, plastic or < jHi 10 of a fibrous material of the mineral wool type, especially for filtration processes, etc. These can also be classified as transparent materials, used in particular as glazing, such as glass substrates or substrates made of flexible or rigid plastic, such as substrates made of polyester or acrylate, such as polymethyl methacrylate (PMMA). Substrates can also • be classified in the category of non-porous or slightly porous (glass) or in the category of (relatively) porous materials, such as tiles and ceramics. Substrates can also be considered as "simple material" such as glass substrates, or comprising a superposition of materials or layers, such as masonry which is provided with a coating of the wall-type type. Coatings containing crystallized anatase 5 Ti02 with photocatalytic properties are already known from International Patent Applications WO 97/10186 and WO 97/10185, these coatings being obtained from the thermal decomposition of suitable organometallic precursors and / or particles of Ti02"pre-crystallized" embedded in a mineral or organic binder. The object of the invention is therefore to provide these types of coating, so that their photocatalytic operation is extended in time, when exposed to aging conditions that can be found in the various applications considered. The object of the invention is thus to improve these types of coatings, especially by maintaining or improving their photocatalytic properties while increasing their durability, especially their mechanical chemical durability.

The object of the invention is firstly a process for obtaining a substrate provided on at least part of its surface with a photocatalytic coating, crystallized particles of an oxide of a metal A having photocatalytic properties which are incorporated in the coating using a mineral binder comprising at least one oxide of a metal B which also has photocatalytic properties in the crystallized state. This binder can also Optionally comprising at least one oxide of a metal M devoid of photocatalytic properties and / or at least one Si compound of the silicon oxide Si02 type. This process consists in depositing the coating from one or more dispersions in liquid phase containing: "^ on the one hand, the crystallized particles f of the metal oxide A;" ^ on the other hand, at least one compound precursor for the metal oxide B of the mineral binder and optionally, a precursor compound for the metal oxide M and / or for the Si compound, and this in a relative proportion defined by a ratio A / (B + M + Si ) between 60/40 and 40/60.

This proportion corresponds to that of the weights of, on the one hand, the metal A, and on the other hand, of the metal B and optionally of the metal M and of silicon Si, contained respectively in the composition of the metal. • oxide of A in the form of particles, and because the precursor or precursors for the oxide of B and optionally for the oxide of M and for the silicon compound of the type Si02. Advantageously, the deposition / coating treatment conditions are • 10 chosen so that the mineral binder, and more particularly the B oxide which forms part of it, is at least partially crystallized in the final coating. Preferably, the oxides of metals A and B are chosen from at least one of the following oxides: titanium oxide, zinc oxide, tin oxide and tungsten oxide. A particularly preferred embodiment is to choose the • oxides of A and B both in the form of oxide of titanium (titanium dioxide), the anatase crystal form of which is highly photocatalytic. M-type oxides devoid of intrinsic photocatalytic properties are, for example, aluminum oxide or zirconium oxide.

The authors of the present invention have been successful in this process in reconciling two constraints that to date were not • easily reconcilable, namely photocatalytic performance and durability, and more specifically these have succeeded in extending the photocatalytic properties of the coating over time. This is because it has been found that the catalytic effect of coating is probably mainly due • the particles that are incorporated in it, whose particles are already crystallized and are already active from the catalytic point of view from the start. It is tempting therefore to maximize the amount of particles in the coating. Surprisingly, however, excessively high and excessively low amounts of particles have been found to be unsuitable for the purpose of achieving both • desired objectives (namely the properties photocatalytic and sufficient durability), the adjustment of the ratio, discovered by the inventors, is the most difficult to achieve when the amount and type of A oxide particles probably influence the morphology of the binder comprising B oxide, the change in the relatively pronounced photocatalytic character of the coating and its retention over time are not linear functions of such • parameter. The process according to the invention has therefore shown that it is possible to select a proportion A / (B + M + Si) within a range that allows the highest reconciliation between a satisfactory level of photocatalytic activity and the retention of this high level of activity • photocatalytic with time. The reasons for this are not completely understood, at least with respect to the photocatalytic operation of the coating. It can be suggested that it is advantageous that the mineral binder also contributes to the activity of the coating. It should also be noted that the coatings obtained tend to have excellent optical properties, especially a • high light transmission and a very low level of turbidity. The precursors for B-oxide that were mentioned above, and optionally those for the oxide or M-oxides, are advantageously organometallic compounds capable of decompose in an oxide under the effect of an adequate treatment, especially thermal treatment. With respect to the precursor for the Si compound, especially the SiO2 precursor, • it is possible to use a compound from the family of 5 silicon alkoxides (silanes). Advantageously, the process according to the invention uses crystallized particles of the oxide of A (especially Ti02 crystallized predominantly in the anatase form) in the • Form of agglomerates of crystallites, preferably agglomerates having an average size of about 5 to 80 nm and crystallites having an average size of about 5 to 20 nm (especially of 5 to 10 nm), in dispersion in a liquid phase, especially in colloidal suspension in an aqueous medium or in dispersion in at least one organic solvent. These sizes correspond to the "diameters" of the agglomerates and the crystallites in • question, looking like its shapes to spheres (even if this is not necessarily the case; in particular, the agglomerates in question can also be approximately lenticular in shape or have the shape of rods). Instead of talking about agglomerates of crystallites, a more correct terminology can in fact be used, namely that the agglomerates are particles and the crystallites are what can be termed by the term crystalline F coherence domain. For a first approximation, it can be considered that the same agglomerates are found in the final coating, having suffered little or no structural or dimensional modification. In fact, it has been observed that when the process for obtaining the photocatalytic coating involves a heat treatment (explained in detail below), this treatment results in these particles being structurally modified, with an appreciable increase in the size of the crystallites. For example, when the crystallites of Ti02 are initially about 5 to 10 nm in size, these are generally rather about 10 to 20 nm in the final coating; Its size has approximately doubled (a factor of 1.5 to 2.5). A detailed description of These particles will be found, for example, in the aforementioned application WO 97/10185 or in the application WO / FR97 / 02068 of November 18, 1987 published under the number WO 98/23549 or the application FR-2, 681, 534.

Preferably, the organometallic compound or precursors for the B oxide, and Jfc optionally for the M oxide, is (are) chosen from the tetraalkoxide family of the formula M (OR) 4, Where M is the metal in question and R is a radical containing carbon of the linear or branched alkyl type, all of which are identical or different, especially having from 1 to 6 carbon atoms. Mention can be made in this way to 'EF 10 titanium tetrabutoxide or titanium tetraisopropoxide. It is also possible to choose them from trialkoxides of the MR '(OR) 3 type, where R and R' are radicals which are identical to or different from the type of those in the tetraalkoxides above mentioned, or halides, especially titanium chlorides. Since these precursors are highly hydrolysable and reactive, it is preferred ^^ dissolve them together with at least one chelating / stabilizing agent, for example of the β-20 diketone type such as acetylacetone (2,4-pentanedione), benzoylacetone (1-phenyl-1,3-butanedione) and diisopropylacetylacetone, or even acid acetic acid, diethanolamine or compounds of the glycols family such as ethylene glycol or tetraoctilenglicol. The concentration of precursor in the solution (for a given solids content, for example) is then adjusted by making suitable dilutions using one or more organic solvents.

• According to a first variant of the invention, the mineral binder of the coating according to the invention comprises only the metal oxide B, the aforementioned proportion A / (B + M + Si) then becomes more simply the proportion A / B • According to a second variant, the mineral binder comprises the metal oxide B, of the Ti02 type and a silicon compound, of the Si02 type, the ratio of A / (B + M + Si) then becomes A / ( B + Yes). The simplest method for implementing the process according to the invention is to deposit the coating from a dispersion containing the precursor (s), and • start from a dispersion containing the particles, these being premixed in a simple dispersion before spraying the latter onto the substrates or submerging the substrate in this simple dispersion, although it is also conceivable to deposit a coating from several separate dispersions, especially two dispersions without premixing them. A first type of deposition technique is • called "hot" deposition, that is to say that during the dispersion / substrate contact, the substrate is at a sufficiently high temperature to allow thermal decomposition of the precursor (s): this is the technique of the pyrolysis type in the liquid phase. 10 A second type of technique is called • "cold" deposition, that is, during the dispersion / substrate contact, the substrate is at room temperature or at least at a temperature that is too low to cause Decomposition of the precursor (s): these are techniques of the sol-gel type, with a deposition method of immersion type, cell coating, laminar coating or coating.

• Dew . 20 A heat treatment after the dispersion / substrate contact phase is necessary in the case of "cold" deposition techniques in order to cure the coating and ensure that the precursors are completely decomposed. Do not However, this also proves to be advantageous in the case of "hot" deposition techniques, since this can improve the cohesion of the coating and favor at least the partial crystallization of the binder that arises from the decomposition of the precursor (s). . This treatment is especially carried out at at least 400 ° C, for example above 450 ° C, especially in the region of 550 to 550 ° C, more particularly when the substrate is capable of withstanding this type of treatment, which fl 10 is the case with substrates having a glass, ceramic or glass-ceramic matrix. The object of the present invention is also a substrate provided on at least part of its surface with a photocatalytic coating incorporating crystallized particles of an oxide of a metal A, with photocatalytic properties using an at least partially crystallized mineral binder comprising an oxide of • a metal B, which also has properties photocatalytic in the crystallized state, especially a substrate obtained according to the process described above. This is characterized by a high porosity, especially greater than 40% and approximately between 45% and 65%.

This porosity can be calculated indirectly, by measuring the Index of the layer, by comparing it with what should be if the material were completely dense. This method • Indirect is very representative of the porosity and of the surface morphology of the layer, since the measurement of the Index also takes into account, at least partially, the degree of surface roughness of the layer. (There are also other indirect methods, especially those that consist of the measurement • the weight of the coating deposited per unit area of the substrate, referred to as the given coating thickness). In fact, this high porosity has many advantages First, it makes it possible to lower the refractive index of the material and vary the optical appearance of the same. In the case of a coating based on Ti02 (ie, the Ti02 particles crystallized predominantly as anatase and a binder based on Ti02, optionally combined with SiO2), decreasing its Index to values at most 2, especially about 1.4 to 1.8 and preferably about 1.7 to 1.8, makes it possible to greatly reduce the well-known reflective appearance. In addition, the porosity of the coating is bound with a high surface roughness, hence a highly developed surface area of the coating that favors its photocatalytic activity. Finally, this coarseness, which is probably of two different types, as described in International Patent WO 98/23549, gives the coating a durable and improved hydrophilic character, thereby imparting pronounced anti-rain and anti-rain properties to it. Anti-fogging (water droplets that are dispersed in an invisible film), and promotes the removal of mineral dust by the drag with rainwater. Surprisingly, this high porosity does not result in excessively high weakening of the coating from a mechanical point of view. The object of the present invention is also a substrate provided on at least part of its surface with a coating having photocatalytic properties, incorporating crystallized particles of an oxide of a metal A with photocatalytic properties, using an at least partially crystallized binder that comprises at least one oxide of a metal B which also has photocatalytic properties in the state • crystallized, and optionally at least one oxide of an M metal devoid of photocatalytic properties and / or a silicon compound of the silicon oxide type, especially one obtained according to the process described above. This is characterized by a relative proportion A / (B + M + Si) between 60/40 and 40/60 in weight with # with respect to the weight of the metals (and optionally of the Si) contained respectively in the composition of the particles of the oxide of A and in the composition of the oxide of B, and optionally of the oxide of M and of the Si compound of the mineral binder. It should be noted that in the invention the substrate considered may have a certain porosity for example when this is a tile, or a • fibrous appearance (eg insulation wool) mineral). When it is established that the substrate is provided with the photocatalytic coating, it should be understood that the latter is deposited on its surface, but also that it can impregnate the substrate over a certain depth if it is porous / fibrous. This is the reason why the amount of exposed coating can be expressed either by its thickness on the substrate, when it is not porous, for example when it is a glass substrate, or by a quantity of material per unit area , more particularly when the substrate has a certain porosity. The coating according to the invention, either obtained by the process described above and / or whether it conforms to the coatings whose intrinsic characteristics have been described above, advantageously has the following structure (more particularly if the oxides of A and B they are both based on Ti02): crystallized particles having a size between 5 and 80 nm with crystalline coherence domains having a size between 5 and 20 nm (according to the conventions described above) and a mineral binder at least partially in the form of grains ending around the crystallized particles, in the interparticle interstices, and having an average size of between 5 and 25 nm, preferably 10 to 20 nm. These "grains" of approximately spherical shape are not completely crystallized, although probably partially crystallized at a very small scale that is difficult to measure, and thus they "encapsulate" the particles and the iFk agglutinate each other. Advantageously, the substrate according to the invention is provided with the catalytic coating of the invention, comprising particles of Ti02 essentially in the form of anatase and a mineral binder combining the Si02 and the partially crystallized Ti02. Preferably, the coating has an Index at most 2, especially between 1.5 and 1.9, or between 1.6 and 1.9 or between 1.6 and 1.8. According to one embodiment, at least one layer that is inserted between the substrate and the photocatalytic coating, the layer or layers have possibly several functions (optical function, barrier for the species responsible for migrating from the substrate, such as metals). • alkaline, antistatic function, adhesion layer, 20 etc). There may be layers based on Si compounds, such as Si, SiO2, SiON, SiOC and Si3N4 or based on an optionally doped metal oxide (F: Sn02, Sb: Sn02, etc.).

The substrates provided with such coatings have already been mentioned in FIG. preamble of the present application. These may comprise a transparent material of the type glass 5 or plastic, especially for the formation of part of the glazing with which the buildings or vehicles are equipped, or of the screens for television or computer-type machines, for example touch screens, or any laminated or "monolithic" glazing (that is, it contains only a simple glass panel or a simple plastic sheet). It is also advantageous to incorporate a transparent substrate provided with the coating of the invention in a structure of insulating multiple glazing, either so that the coating is on an internal face of the encristalado or on an external face of encristalado. This can be conventional insulating glazing that has one or more interlayers gas, for example of the type marketed by Saint-Gobain Vitrage under the names BIVER or CLIMALIT D, CONTRATHERM, CONTRASONOR, CONTRARISC, or those calls encristalados "a vacio" in which the interlayer of gas is replaced with a vacuum, as described for example in European Patent EP-645,516. Especially in the latter case, it is particularly advantageous to place the coating as the outer face, on that face of the insulating glazing 5 facing outwards, in order to prevent the formation of fogging by virtue of its hydrophilic nature. The coating of the invention is also advantageous for glazed walls of freezers / refrigerators In fact, many materials can act as substrates for the coating according to the invention, for example metal, ceramic, plastic or cement materials and all the above mentioned materials used in architecture for applications such as masonry, plating or roofing materials such as tiles and slabs. These can also be materials with which floors or walls • Interiors or exteriors of the residences are equipped, such as slabs or tiles. It is also possible to deposit coatings on fibrous materials of the mineral wool type for thermal and / or acoustic insulation, or even on fibers of the textile yarn type for the reinforcement, possibly finding these fibrous materials applications in filtration processes for example: it is in this way possible to exploit the antifouling properties, • Bactericides, fungicides and anti-fogging of the coating of the invention as required. The object of the invention is also the liquid phase dispersion that was described in particular above and can be used to manufacture the photocatalytic coating in accordance to the invention. The dispersion comprises • especially a solvent chosen from water, ethylene glycol, ethanol, propylene glycol, and mixtures thereof. The nature of the crystalline phase of The titanium dioxide particles of the dispersion according to the invention are preferably predominantly in the anatase crystal form. "Predominantly" means • that the anatase content of the particles of The titanium dioxide in the coating is greater than 50% by mass. Preferably, the particles of the coating have an anatase content greater than 30%. The crystallinity and the nature of the crystalline phase are measured by X-ray diffraction.

The dispersions according to the invention are generally obtained by mixing a dispersion of titanium dioxide particles • with solutions of the precursor compounds and / or a silicon compound. Depending on the nature of the compounds used, it is also possible, during this mixture, to add additives such as cosolvents, surfactants or stabilizers. The mixture can also be improved by agitation of the dispersion ultrasonically. • Additional details and advantageous features of the invention will emerge from the following description of non-limiting illustrative examples, with the help of the following figures: D Figure 1: a highly schematic representation of the structure of a photocatalytic coating according to the invention; • D Figure 2: a photograph obtained by scanning electron microscopy (SEM) of the surface of a photocatalytic coating according to the invention. A first series of examples refers to the deposition of a coating 3 called "antifouling" essentially based on titanium oxide on a transparent substrate 1. The substrate 1 is made of clear glass • siliceous-soda-limestone plan of 15 x 40 cm2 of 5 area and 4 mm thickness. Needless to say, the invention is not limited to this specific type of glass. In addition, the glass may not be flat, but curved. Between coating 3 and substrate 1 there may optionally be a thin layer 2 • Based on silicon oxycarbide, denoted SiOC, for the purpose of forming a barrier to the diffusion of alkali metals, these being harmful to the photocatalytic property of the coating, and / or a A layer having an optical function, for example deposited in a known manner by a chemical vapor deposition (CVD) technique with a thickness of approximately 50 nm. • Two different processes have been used "cold storage", namely deposition by immersion in the cell coating mode with a bath drainage speed of approximately 5 to 30 cm / minute, and deposition by spray coating, i.e. cold liquid. These well-known techniques are explained in detail in the patent applications referred to above, to which the reader can refer. • The coatings are deposited from a dispersion obtained by mixing two initial solutions / dispersions 1 and 2; ^ solution 1: this is the solution that contains the organometallic precursor for the mineral binder based on Ti02. This is Ti titanium isopropylate (OCH (CH3) 2) 4 stabilized with acetylacetonate CH3-CO-CH2-CO-CH3 in solution in ethanol; • dispersion 2: this is the liquid phase of ethylene glycol containing the crystallized photocatalytic particles having the following characteristics: "= specific surface area of the particles:> 350 m2 / g • = particle size:» 40 nm 20 • => size of the crystallites constituting the particles: 7 nm => crystalline phase: more than 80% anatase The composition of the dispersion obtained by mixing solution 1 with the Dispersion 2 is adjusted in order to obtain the desired ratio of Ti (2) / Ti (i), ie the proportion of the weight of titanium (2) that comes from the particles in the dispersion 2 to the weight of titanium (1 ) • which comes from the precursors in solution 1, (by 5 convention, the proportion can also be that of the weight of the titanium oxide coming from the particles to the weight of the titanium oxide coming from the metallic precursor, assuming that 100% of the precursor is converted into oxide: this represents the same thing). • Examples 1 to 7 refer to the deposition by immersion in the cell coating mode, under comparable conditions of deposition, that is to say with the same velocity of drained bath (6 cm / minute) and the same concentration of titanium (namely 3% solids content, converted into weight of oxide) coming from the precursor in solution 1. • After deposition, substrates undergo a heat treatment of about 450-500 ° C for at least 30 minutes. Table 1 below gives, for each of them: < = > the ratio Ti (2) / Ti (i) is explained above, which has no units; * = > the thickness (e) of the coating (3), in nm; the light transmission value TJ, in% measured using the illuminant D65; = the value of "optical clarity" in%, measured by the ratio of the diffuse transmission to the integrated light transmission over the entire visible range.

TABLE 1 • • Example 8 was produced from the dispersion according to that used by the example 4, but deposited on the substrate by cold spraying using a spray nozzle denominated without air, at a pressure of 0.7 bars (0.7 x 105 Pa). The layer obtained, after ÍÍF thermal treatment of about 452-500 ° C for at least 30 minutes, has a thickness of approximately 35 to 60 nm, with a TL value of 88.6% and an optical clarity value of 0.6% with the same conventions as in Table 1. Examples 1 to 8 above were evaluated in terms of photocatalytic activity at 10 before and then after a treatment aimed at stimulating the accelerated aging of the coating. The photocatalytic activity is measured as follows: 15 • = F test carried out on approximately 15 cm2 of coating; = > ® the weighing of the specimen and the measurement of substrate thickness, T and optical clarity; 20"=> <3) spray deposition of a palmitic acid solution (8 g of acid per 1 liter of chloroform) with a distance of glass / spray nozzle of 20 cm, with the vertical substrate, in 3 a 4 successive passes; ^ El the weighing of the specimen after the deposition of palmitic acid, in order to determine the thickness of the deposited acid, in • nanometers; 5"= > © the measurement of optical clarity and TL after the stool; < = > © the measurement of the change in optical clarity as a function of the UVA irradiation time (* 30 V / m2); é- \ 10 = > ® the graphical determination of the time in which the optical clarity has decreased by 50%: this time is called T? 2 (disappearance); < = > ® evaluation of the photocatalytic activity of the coating as the disappearance velocity v (in nm / h) defined by: v (nm / h) = [thickness of palmitic acid (nm)] / [2 x T1 / 2 (disappearance) (h)]. The aging of coatings ^ consists of subjecting them to mechanical abrasion in the following manner: = specimen size: 7 cm x 15 cm; < = applied load: 600 grams; = area of the abrasion felt: 1.5 cm2; ^ n cycles (1 cycle = 1 forward and backwards movement of the felt carrier and load), with n = 200 and 500. Table 2 below gives, for each of the following examples: "= speed of disappearance I saw before the abrasion; = => the disappearance velocity v2 after 200 cycles; • 10 < = > the disappearance speed v3 after 500 cycles.

TABLE 2 • In addition, the analyzes have shown that the coatings in examples 3, 4 and 5 had a structure probably similar to that • shown, in a highly simplified manner in FIG. 1, which represents the glass substrate 1, the SiOC layer 2 and the coating 3. This coating comprises the particles or aggregates of crystallites 5 between which the grains are agglomerated. Ti02 amorphous or slightly crystallized, 10 forming these the mineral coating binder. Figure 2, with reference more specifically to Figure 4, is a photograph obtained by scanning electron microscopy that gives the information regarding the surface appearance of Example 4: a rather rough surface, allowing the coating to offer a surface area developed large. • It should be noted that Example 4 has a Refractive Index of about 1.65. To a first approximation, knowing that the refractive index of Ti02 to "bulk" is 2.4, it can therefore be considered that the porosity of the coating is approximately (2.4 - 1.65) /2.4 25-1), ie approximately 54% The coating according to example 4 also shows strong hydrophilicity, exposed to UVA rays for 20 minutes or in order to activate it, this is put in the dark and the contact angle f with respect to water is periodically measured: this angle of contact remains less than 10 ° for at least 20 days in the dark. The following conclusions can be obtained from these data: examples 3, 4, 6 and 8, and especially example 5, in which the proportion of Ti (2) / Ti (i) is 50/50, which they combine all the desired properties, namely: < = > a high TL, a low optical appearance and a refractive index less than 2, giving the coating a highly favorable optical appearance; "= > a satisfactory photocatalytic activity, which is still present even after the mechanical attack, thereby providing the durability of the coatings, and which makes it possible to use these coatings under real conditions, for example on external glazing, at have an acceptable "life time." These are in fact the only examples produced that still show photocatalytic activity, although moderate, after 500 cycles of abrasion.A second series of examples refers to the same type of coating, based on the same "solution 1" and the same "dispersion 2." The deposition conditions are identical to those of the previous examples 1 to 7, apart from the difference that now the drainage speed of the bath is higher, being equal to 24 cm / minute. Another difference refers to the substrate: this is the same glass, but it is covered beforehand with a first layer of 50 nm of SiOC deposited by CVD and then a second layer of 450 nm of tin oxide doped with fluorine (F: Sn02 ) deposited by powder pyrolysis in a known manner. Furthermore, in this series of examples, the quantity Q of the photocatalytic coating is evaluated not by measuring its thickness, but by measuring the amount of material per unit area of the substrate, expressed in μg / cm2. The photocatalytic activity of the examples is measured before any abrasion test, ie the value vi explained above. The durability of the coating is evaluated qualitatively, simply by rubbing with a cloth: "++" means that the coating is very strongly resistant, "+" means that it is still properly resistant and "-" means that the coating has been (almost ) removed after rubbing it with a cloth. Table 3 below gives, for examples 9 to 13, the ratio Ti (2) / Ti (i), with the same meaning as in table 1, the value Q, the value F 10 vi and the speed of the rag rub test: TABLE 3 • 15 The same trend can be observed in this table as for the first series, namely, with an identical or almost identical quantity of the deposited coating, the optimum occurs for examples 11 and 12 that have proportions Ti (2) / Ti (i) 40/60 and 50/50. Only Example 12 shows a photocatalytic activity above 200 and 5 correct durability. A third series of examples refers to a coating using Ti02 particles of the dispersion used in all the previous examples, but with a hybrid binder that combines Ti02 with • 10 Si02. The solution containing the precursors for the binder uses: - > as solvent: ethanol and ethylene glycol in proportions of 75/25 by mass; 15 t > as a stabilizer: acetylacetonate; • as a precursor of Ti0: titanium tetrabutoxide (TBT); •? as a precursor of Si02: • tetraethylorthosilicate (TEOS). 20 The relative proportion of TBT to TEOS is adjusted to have a Ti02 / Si02 ratio of 15/85 by weight in the solution (using the convention that all TPT is converted to Ti02 and all TEOS to Si02).

Next, this solution is added to the particle dispersion used in the examples 4fe previous, in proportions such that the desired proportion r is obtained, (Tipartícuias / (TipreCursor + Siprecursor) • (The solids content of the solution is 3%). The deposition and the conditions of the substrate are identical to those in examples 9 to 13. 10 Table 4 below gives the values of the proportion r explained above, the value of the proportion vi explained above, the light reflection of the coated substrate RL ( %), and the variation of TL (? TL), observed after 500 15 cycles of the abrasion test described within the context of the first series of examples, as well as the proportion ri that expresses the proportion of the amount of Ti to the amount of Si as the weight of • oxide: 2 0 ri = Tl? 2Partisulas / (T l02aglutnante + S l02aglutinante) • The table also shows Qi, the amount of Total Ti02 in the coating (particles and Ti02 resulting from the titanium precursor) in μg / cm2 and Q2, the amount calculated, as the total weight, of the coating, also in μg / cm2.

TABLE 4 By adjusting the solids content of the solution and the rate of drainage, the • Coatings were repeated by fixing the ratio r to 55.3 / 44.7 and by varying the amount of coating deposited. Table 5 below gives, for these additional examples of Example 5, the quantity Q in μg / cm2, the corresponding thickness e in nm, when this is measured, the value of vi (in nm / h), the value of RL and the value of? T, these being explained above: • 15 TABLE 5 It can be observed from this third series of examples that there is an advantage in adding Mk a Si02 material to the binder, this material not being involved in the photocatalysis, but allowing the coating to be made more homogeneous and tending to increase its durability. It can also be observed that although the proportion r is key, other parameters may also be involved, especially the Q value, which is preferably between 15 and 45 μg / cm2 in order to take into account the cost of the coating and the impact of its thickness on the optical appearance. Needless to say, the invention is not limited to these specific examples. In particular, it is within the scope of the invention to further improve the photocatalytic activity of the particles by impurifying them, by introducing dopants into the crystal lattice or by covering the particles with said dopants of the type comprising Fe, Cu, Ru, Mo, Bi, Ta, Nb, Co, Ni, Va, etc., as described in the aforementioned patent WO 97/10185. It may also be within the scope of the invention to add a mineral binder comprising oxides, which are not photocatalytic or only slightly photocatalytic in the crystallized state, for example by the addition of the • precursors of the dispersion for other oxides, of the Si02 type, such as tetraethoxysilane TEOS. The above-mentioned ratio A / (B + M + si), which is optimal in the range of 40/60 to 60/40, can also be considered, with a lower level of requirement, in the 35/65 intervals to 40/60 and 65/35 to 60/40. • •

Claims (32)

1. A process for obtaining a • substrate provided on at least part of its surface, with a coating having photocatalytic properties, crystallized particles of an oxide of a metal A having photocatalytic properties that are incorporated into said coating using a binder A mineral comprising at least one oxide of a metal B which also has photocatalytic properties in the crystallized state, and optionally at least one oxide of a metal M devoid of photocatalytic properties and / or at least one silicon compound 15 Si of the silicon oxide type, characterized in that the coating is deposited from dispersions in liquid phase containing: on the one hand, the crystallized particles of metal oxide A; On the other hand, at least one compound The precursor of the metal oxide B of the binder and optionally a precursor compound for the metal oxide M and / or for the Si compound, in a relative proportion A / (B + M + Si) by weight with respect to the weight of the metals, and content 25 respectively in the composition of the metal oxide A and of the precursor (s) for the metal oxide B and optionally for the metal oxide M and for the Si compound, between 60/40 and 40/60. •

2. Process according to claim 1, characterized in that the mineral binder is at least partially crystallized.

• Process according to claim 1 or claim 2, characterized in that the metal oxides A and B are chosen from at least one of the following oxides: titanium dioxide, zinc oxide, tin oxide and 15 tungsten oxide, preferably with both oxides of metals A and B in the form of titanium oxide.

4. Process of compliance with any • of the preceding claims, characterized 20 because the mineral binder comprises only the metal oxide B, the ratio A / (B + M + Si) is expressed in the A / B form.

5. Process according to any of the preceding claims, characterized in that the mineral binder comprises the metal oxide B, of the Ti02 type and a silicon compound of the Si02 type, the ratio A / (B + M + Si) is then expressed in the form A / (B + Si). 6. Process according to any of the preceding claims, characterized in that the crystallized particles of the metal oxide A in the form of particles, which have

-J? 10 preferably an average size of about 5 nm to 80 nm and crystalline coherence domains having an average size of about 5 nm to 20 nm, especially as a dispersion in at least one organic or aqueous solvent. 7. Process according to any of the preceding claims, characterized in that the organometallic compound (s) ^ 1 ^ precursors for B oxide and optionally for

The oxide of M are selected from the family of tetraalkoxides of the formula M (OR) 4, trialkoxides of the formula MR '(0R) 3 or metal halides, where R and R' are carbon-containing radicals.

8. Process according to any of the preceding claims, characterized in that the precursor (s) • Organometallic for the B oxide and optionally for the M oxide, are dispersed in a liquid phase containing at least one chelating / stabilizing agent.

9. Process of compliance with any • 10 of the preceding claims, characterized in that the coating is deposited by pyrolysis in liquid phase using a dispersion containing the precursor (s) of the organometallic compound type, and the crystallized particles.

10. Process according to any of the preceding claims, characterized • because the coating is deposited by a 20 sol-gel technique using a deposition method such as immersion, cell coating, laminar coating or spray coating, using a dispersion containing the organometallic compound (s) and the particles 25 crystallized.

11. Process according to any of the preceding claims, characterized in that the coating undergoes the heat treatment, especially at least at 400 ° C.

12. The substrate, provided on at least part of its surface with a coating, having photocatalytic properties, crystallized particles and an oxide of a metal A having 10 photocatalytic properties, which is incorporated • using an at least partially crystallized mineral binder comprising an oxide of a metal B which also has photocatalytic properties in the crystallized state, and Optionally at least one oxide of a metal M devoid of photocatalytic properties and / or a silicon compound of the silicon oxide type, especially one obtained according to the process • in accordance with any of the 20 previous claims, characterized in that the coating has a porosity, calculated by measuring the refractive index, greater than 40%, especially between 45 and 65%.

13. Substrate, provided on at least part of its surface with a coating having photocatalytic properties, particles • crystallized from an oxide of a metal A having 5 photocatalytic properties which is incorporated using an at least partially crystallized mineral binder comprising at least one oxide of a metal B which also has photocatalytic properties in the crystallized state, and Optionally at least one oxide of a metal M devoid of photocatalytic activity and / or a silicon compound of the silicon oxide type, especially one obtained according to the process in accordance with any of the 15 claims 1 to 11, characterized in that the coating contains a relative proportion A / (B + M + Si), by weight, with respect to the weight of the metals contained respectively in the composition of the crystallized particles of the oxide of A and in The composition of the B oxide, and optionally the oxide of the metal M and / or the Si compound of the mineral binder, is between 60/40 and 40/60.

14. Substrate according to claim 12 or claim 13, characterized in that the coating comprises the crystallized particles, which have a size of approximately 5 to 80 nm and coherence domains • crystalline having a size of about 5 nm to 20 nm, and the mineral binder at least partially in the form of grains, which have especially a size between 5 and 25 nm, preferably 10 to 20 nm.

- ^ F 10 15. Substrate according to any of claims 12 to 14, characterized in that the coating comprises crystallized particles of Ti02 essentially in the anatase form and a mineral binder based on partially crystallized Ti02.

16. Substrate according to any of claims 12 to 14, characterized • because the coating comprises Ti02 particles 20 essentially in the anatase form and a mineral binder that combines the partially crystallized Ti02 with the SiO2.

17. Substrate according to claim 15 or 16, characterized in that the coating has a refractive index of at most 2, especially between 1.5 and 1.9, for example between 1.6 and 1.8. •

18. Substrate according to any of claims 12 to 17, characterized in that at least one layer, especially one having the function of being a barrier to the alkali metals and / or having an optical function and / or • 10 antistatic and / or adhesion is inserted between the substrate and the coating having photocatalytic properties, especially at least one layer based on an Si compound, such as Si, SiO2, SiOC, SiON, and Si3N4, or based on a metal oxide 15 optionally contaminated such as tin oxide doped with fluorine.

19. Substrate according to any of claims 12 to 18, or obtained according to the process according to one of claims 1 to 11, characterized in that it comprises at least one transparent material of the glass or plastic type, especially to form part of the glazing for screens for television or computer type machines, such as touch screens.

• 20. Substrate according to claim 5, characterized in that it forms part of the insulating glazing, on the inner or outer face, especially conventional insulating glazing having one or more gas interlayers or glazing of "vacuum" insulation, or part of 10 any laminated or "monolithic" glazing.

21. Substrate according to any of claims 12 to 18, or obtained according to the process of compliance with any 15 of claims 1 to 11, characterized in that it is made of a material of the metal or ceramic type, masonry material, plating material, or roofing material or for flooring, such as tiles or slabs, stone or wood, 20 pavement of tile, cement, plastic, any architectural material, fibrous material of the mineral wool type for thermal and / or acoustic insulation, or textile fiber.

22. Dispersion in liquid phase, comprising: particles of crystallized titanium dioxide; at least one precursor compound for • a metal oxide B that has photocatalytic properties in the crystallized state; optionally at least one precursor compound for a metal oxide M and / or a silicon compound; characterized in that the particles, the precursors and the silicon compound are in a proportion • 1 0 relative A / (B + M + Si) between 60/40 and 40/60.

23. Dispersion according to claim 22, characterized in that the titanium dioxide particles are 15 predominantly in the anatase crystal form.

24. Dispersion according to any of claims 22 and 23, • characterized because the dioxide particles of Titanium have an average size of about 5 to 80 nm and a crystalline coherence domain having an average size of about 5 to 20 nm.

25. Dispersion in accordance with any of claims 22 a. 25, characterized in that the metal oxide B is chosen from: titanium dioxide, zinc oxide, tin oxide and tungsten oxide.

26. Dispersion according to any of claims 22 to 25, characterized in that the metal oxide M is chosen from aluminum oxide and zirconium oxide. flfc 10

27. Dispersion according to any of claims 22 to 26, characterized in that the precursor compounds for the metal oxides B and M are organometallic compounds.

28. Dispersion according to claim 27, characterized in that the organometallic compounds are chosen from the • family of tetraalkoxides of the formula X (OR) 4 and 20 trialcoxides of the formula XR '(OR) 3 or metal halides, where R and R' represent radicals containing carbon and X represents M or B.

29. Dispersion according to any one of claims 22 to 28, characterized in that the silicon compound is chosen from silicon alkoxides.

30. Dispersion according to any of claims 22 to 29, characterized in that it comprises a chelating / stabilizing agent.

31. Dispersion in accordance with • any one of claims 22 to 30, characterized in that the liquid phase comprises a solvent chosen from water, ethylene glycol, ethanol, propylene glycol and mixtures thereof.

32. Dispersion according to any of claims 22 to 32, characterized in that it comprises: particles of crystallized titanium dioxide; tetrabutoxide ^ titanium as a precursor compound for an oxide of 20 metal B; tetraorthosyl icate as a silicon compound, in a relative proportion A / (B + Si) of about 50/50.