Substrate with photocatalytic coating

p0001The present invention relates to substrates provided with a photocatalytic coating, the method for obtaining such a coating and its various applications.

p0002It relates more particularly to coatings comprising semiconductor materials based on metal oxides, especially titanium oxide, which are capable, under the effect of a suitable wavelength of radiation, to initiate radical reactions causing the oxidation of organic products.

p0003The coatings thus possible to impart new functionality to the materials they cover, including anti-fouling properties, fungicides, bactericides, possibly combined with hydrophilic properties, anti-fogging, optical, ...

p0004Very various substrates can be envisaged, in particular those used in the field of vehicles or buildings, such as glazing, facade materials, cladding, roofing, flooring, such as tiles, slates, slabs, tiles and generally any material used in construction. These materials can be as glass, metal, ceramic, ceramic, cement, brick, wood, stone or material reconstituted from these natural materials, plastic material, fibrous material of the mineral wool type, especially for filtration processes, etc ...

p0005They can be grouped also in transparent materials, used in particular as glazing, such as glass substrates or flexible or rigid plastic such as polyester substrates or acrylate such as polymethyl methacrylate (PMMA). The substrates can also be categorized as unskilled or porous (glass) or in the category of materials (relatively) porous such as tiles, ceramics.

p0006We can consider the substrates "mono-materials" such as glass substrates or substrates with an overlay material layers, such as facades which we equip one type of coating plaster facade.

p0007It is already known international patent applications <patcit id="pcit0001" dnum="WO9710186A"><text>WO97 / 10186</text></patcit> and <patcit id="pcit0002" dnum="WO9710185A"><text>WO97 / 10185</text></patcit> coatings containing TiO₂ anatase crystallized photocatalytic properties, coatings obtained from the thermal decomposition of suitable organometallic precursors and / or from particles of TiO₂ "Precrystallized" and embedded in an inorganic or organic binder.

p0008It is also known Patents <patcit id="pcit0003" dnum="WO9944954A"><text>WO99 / ​​44954</text></patcit> and <patcit id="pcit0004" dnum="FR2738836A"><text>FR-A-2738836</text></patcit> an improvement in these types of coatings of using particles T1O₂ precrystallized that are coated in a binder, which also contains TiO₂ partially crystalline: thus comes binder participate in the photocatalytic effect of the particles, increasing the coating performance both in terms of photocatalytic properties and durability.

p0009It is also known patent applications <patcit id="pcit0005" dnum="EP1036826A"><text>EP-1036826</text></patcit> and <patcit id="pcit0006" dnum="EP1081108A"><text>EP-1081108</text></patcit> coatings using particles of TiO₂ in a binder containing zirconium oxide.

p0010The invention therefore aims to improve known photocatalytic coatings, particularly in terms of level of photocatalytic performance, durability of its performance over time and / or mechanical / chemical durability.

p0011The present invention first of all relates to a substrate provided on at least a portion of at least one of its faces with a photocatalytic coating containing photocatalytic titanium oxide (preferably essentially or predominantly in anatase form), that is in an essentially mineral binder comprising at least one semiconducting metal oxide chosen from those listed in claim 1.

p0012Preferably chosen an oxide semiconductor which has not substantially, under solar illumination, photocatalytic activity (or so whose photocatalytic activity is markedly lower than that of the TiO₂), And significant electronic conductivity. Its resistivity is advantageously chosen less than or equal to 10⁸ ohm.cm, especially less than or equal to 10⁷ or 10⁶ ohm.cm. The resistivity can be selected even much lower, for example less than 10 ohm.cm. (By extension, this resistivity may be that of the binder as a whole, if it contains a plurality of semiconductor oxides and optionally other compounds which are not.)

p0013In fact, as will be detailed later, it turned out that semiconductor oxide, thus exhibiting a certain level of electronic conductivity, allowed, as binder in combination with TiO₂ photocatalyst, to increase the efficiency of the photocatalytic process, in comparison with a binder which is electrically insulating, for example a basic binder to SiO₂. Surprisingly, using such a binder "driver" of the invention can increase the photocatalytic level of the coating as a whole, and also to increase the durability of this feature.

p0014This application is therefore out of the patent teaching <patcit id="pcit0007" dnum="WO9944954A"><text>WO99 / ​​44954</text></patcit>. It is not a question, in the present invention, to make the photocatalytic coating using a binder which is partially crystallized and photocatalytic itself. Here it is not important to add the photocatalytic activity of the particles of TiO₂ crystallized, and the more low from the binder. In the invention, it seeks primarily to operate than electronic conductivity properties of the binder, which, moreover, can be completely amorphous, completely devoid of photocatalytic activity per se.

p0015The invention has discovered a cooperative effect, synergy between the photocatalytic material and the material with which it is closely associated: the binder.

p0016According to a first variant of the invention, at least part of the photocatalytic titanium oxide (including all or the majority) is incorporated in the coating in the form of preformed particles. preferably nano-sized particles is chosen. These particles are generally in the form of agglomerates of crystallites, the agglomerates having an average size of about 5 to 80 nm (eg 30 to 60 nm) and a crystallite mean size of about 5 to 20 nm (including 5 10 nm). generally they are handled in the form of a dispersion in a liquid phase, especially in colloidal suspension in an aqueous medium or dispersion in one or more organic solvents. These average sizes correspond to diameters, assimilating approximation their shapes to spheres (although this is not necessarily the case, the particles may also have a lenticular shape or rod-shaped). As a first approximation, we can consider that we find in the final coating the same agglomerates, having suffered little structural or dimensional change. In fact, it was observed that when the coating of the manufacturing process involves a heat treatment, it is generally accompanied by a substantial increase in the crystallite size, for example by a factor 1.5 to 2.5, as is detailed in the patent<patcit id="pcit0008" dnum="WO9944954A"><text>WO99 / ​​44954</text></patcit> supra.

p0017According to a second variant, at least part of the photocatalytic titanium oxide is formed during formation of the coating, especially by thermal decomposition of organometallic precursors or type of metal halide or metal salts. As explained in the patent<patcit id="pcit0009" dnum="WO9710186A"><text>WO97 / 10186</text></patcit> cited above, the coating deposition techniques (detailed below) of the sol-gel precursor or pyrolysis adhoc allow in situ forming "particles" of TiO₂ photocatalytic (either at hot deposition, or by crystallization by a post-deposition heat treatment). In this case, we also have crystalline domains TiO₂ (Anatase) distributed in the binder that can be assimilated to previously formed particles described in the first variant, knowing that may also be present amorphous areas of TiO₂.

p0018Both variants are alternative or cumulative.

p0019To amplify the impact of the "driver" binder of the invention (this term is understood in the rest of the text, the presence in the binder of one or more metal oxide semiconductor), its electronic conductivity can be increased by doping with a metal or a halogen or the semi-conducting oxides of the binder. This doping, especially with a halogen, can be achieved by using a deposition technique by thermal decomposition of halogenated precursors (which are also the precursors of one of the oxides of the coating or which is a precursor whose sole function is to provide halogen), a technique referred to earlier. To facilitate the incorporation of halogen into the coating, in particular when starting from precursors of the metal halide type, can be carried on the coating, during or after its deposition, a heat treatment under atmosphere substoichiometric in oxygen

p0020In fact, we must understand the term "doping" in the broadest sense, in that the dopant is incorporated in the coating, but not necessarily found only in the binder or on one of the compounds constituting the binder.

p0021The inventors have studied the reason why we got a photocatalytic level, at constant amount of TiO₂ photocatalytic, higher with a conductive binder. In fact, under the effect of an adequate radiation centered on ultraviolet, electron-hole pairs are generated in the particles of TiO₂ Photocatalytic: the holes initiate radical reactions which cause the oxidation of organic substances, the electrons to produce an electrochemical reduction. The presence of a conductive binder would allow two things:<ul><li>➢ one hand, it could accommodate the photoelectrons generated in the TiO₂ photocatalytic, and allow these electrons to carry out therein an electrochemical reduction, in principle that of oxygen. It has thus cooperation between the photocatalytic particles and their binder, the photocatalytic particles being the seat of oxidation reactions by photo-holes, while the binder is the seat of reduction reactions by the photoelectrons that have been there transferred. It would therefore optimization of the redox cycle involved in the phenomenon of photocatalysis, allowing electrons to be effectively used,</li><li>➢ the other hand, the "evacuation" of electrons disadvantage spontaneous recombination of electron-hole pairs generated by the particles, which again goes in the direction of greater efficiency of the particles.</li></ul>

p0022Two situations may arise, without limitation:<ul><li>➢ in a first situation, the or at least one oxide of metal (s) (s) semiconductor (s) of the binder has the lowest energy level of its conduction band, which is:<ul><li>① - less than or equal to the lowest energy level of the conduction band of the photocatalytic titanium oxide,</li><li>② - close to the electronic energy level (most likely) oxygen, E⁰_oxIn the redox couple O₂/ H₂O₂ or O₂/ H₂O.</li><li>① - the relative positioning of the conduction bands of the binder and the photocatalytic oxide is important: whether the driver binder has a sufficient level of electronic conduction to transport electrons on the surface of the binder, it is also necessary that the band conduction of the binder is near, preferably lower in energy than TiO₂ photocatalytic, so that the electrons can pass from one material to another,</li><li>② - about the energy level E⁰_ox redox couples O₂/ H₂O₂ or O₂/ H₂O, while it is similar to that of the conduction band of the conducting binder, the double reduction reaction (on the binder) and oxidation (on the TiO₂) Will be favored, the electrons will be able to achieve the desired electrochemical reduction.</li></ul></li></ul>

p0023A number of oxides meet these two conditions ① and ②.

p0024These include titanium oxide TiO₂, Of tin oxide SnO₂, Antimony oxide (especially Sb₂O₃ and / or Sb₂O₅), ZnO of zinc oxide, tungsten oxide WO₃, Cobalt oxide Co₃O₄, Of nickel oxide NiO, a mixed oxide of cobalt and nickel NiCo₂O₄. Each of these oxides may also be doped (as ZnO: Al, SnO₂: Sb, SnO₂F, ZrO₂F, Sb₂O₃: F, ZnO: F). It can also be mixed oxides containing manganese (the manganite family) and mixed oxides containing cobalt (the family cobaltites).

p0025It turned out that the pre-cited oxides containing Co, Ni or Mn have an additional advantage: they are compounds which are catalytic vis-à-vis the oxygen reduction. The redox reaction mentioned above is thus further enhanced. Literature; the properties studied catalytic mixed oxides of Ni and Co, including the publication "<nplcit id="ncit0001" npl-type="s"><text>Surface properties of Ni and Co mixed oxides: a study by X rays, XPS, BET and PZC "LA De Faria, JF Koenig, Chartier P and S Trasatti (Electrochemica Acta 44 (1998) 1481-1489</text></nplcit>). Publications describe methods for obtaining sol-gel oxide of Ni and / or Co, such as<nplcit id="ncit0002" npl-type="s"><text> Svegl F. et al. in Electrochemica Acta 45 (2000) 4359-4371</text></nplcit>, Of the <nplcit id="ncit0003" npl-type="s"><text>Spinolo G. et al. in Journal of Electroanalytical Chemistry 423 (1997) 49-57</text></nplcit>And that <nplcit id="ncit0004" npl-type="s"><text>JG Kim et al. in Applied Surface Science 165 (2000) 70-84</text></nplcit>.

p0026An advantageous embodiment of the invention therefore consists in that the binder "driver" is not only electronic conductor, but also catalyst vis-a-vis of the reduction of oxygen (at least for a semiconductor oxides it contains if it contains one).

p0027In a second case, the or at least one oxide of metal (s) (s) semiconductor (s) of the binder:<ul><li>① - the lowest energy level of its conduction band which is higher than that of the photocatalytic titanium oxide,</li><li>② - the electronic states in the band gap, particularly related to structural defects and / or dangling bonds. These include the aluminum oxide Al₂O₃ and zirconium oxide ZrO₂ (Optionally doped). Despite the unfavorable positioning of their conduction bands, this oxide has proved advantageous because they have so intermediate energy states located in their bandgap that allow them to accommodate electrons (and approaching levels of E⁰_ox O pairs₂/ H₂O₂ or O₂/ H₂O).</li></ul>

p0028According to a variant of the invention, the binder according to the invention may further comprise at least one electrically insulating compound, especially a silicon derivative such as silicon oxide, oxynitride, oxycarbide or silicon nitride.

p0029It is understood by "insulating" materials that have such a resistivity greater than 10¹⁰ ohm.cm, in particular greater than 10¹² ohm.cm.

p0030An extremely advantageous consequence of the invention is that one can modulate the rate much more freely TiO₂ photocatalytic coating in: relatively low rates allow even still get photocatalytic satisfactory levels thanks to the effect of the binder driver amplifier. Especially in the variant in which the particles are used of TiO₂ photocatalytic preformed, this can be of considerable interest, since a high rate preformed particles in the coating generally tends to lower the durability and / or adhesion to the substrate on which the coating is deposited: the invention thus makes for better performance / durability, especially in this variant.

p0031May thus be chosen, for example, a ratio R_{TiO2 / binder} by weight of the photocatalytic titanium oxide and the binder varies between 10/90 and 60/40, especially 10/90 to 50/50 or 20/80 to 40/60.

p0032As regards the binder composition, it is preferred that the rate of oxide (s) metal (s) semiconductor (s) therein is at least 25% by weight, especially at least 50 up to 100% by weight. It may be interesting, as we have seen above, adding a non-conductive material such as SiO₂, In particular for optical considerations: thus, the presence of SiO₂ can lower the overall refractive index of the coating, which lowers if necessary its light reflection.

p0033Advantageously, the amount of titanium oxide present in the coating is between 5 and 100 g / cm², Especially between 10 and 50 or between 15 and 35 g / cm². Here, it is the whole titanium oxide, comprising both the TiO₂ photocatalytic crystallized and optionally also TiO₂ photocatalytic (amorphous) is there in the binder.

p0034The coatings according to the invention in particular exhibit a photocatalytic activity of the coating, based on the total amount of titanium oxide, of at least 2 nm / h / (g / cm²), In particular at least 5, 10 or 20 nm / h / (g / cm²). The fact report this activity to the total amount of TiO₂ to better assess the impact of the binder on performance, as the examples demonstrate it later.

p0035The coatings according to the invention, especially when they are intended to cover glasses or transparent substrates for glazing, are preferably interferential thickness (not more than 1 .mu.m, generally of the order of 10 to 300 nm).

p0036A variant according to the invention consists in associating the coating to at least one further interference layer thickness. It may especially be a layer having thermal properties (low-emissivity) optical function (to reduce the level of light reflection or change the color by interference effect) or barrier to the migration of species diffusing out substrate: one then inserts the layer between the substrate and the coating. This is particularly useful when the substrate is glass, for blocking the diffusion of alkali. The sub-barrier layer may be silicon compound such as silicon oxide, oxycarbide or oxynitride or silicon nitride or based on optionally doped metal oxide (SnO₂F, SiO₂Sb, ...). The coating may thus be the final layer of a multilayer heat reflective / low-E, for example.

p0037The applications of the coated substrate according to the invention have already been mentioned in the preamble of the claim. It can in fact be any architectural material, especially glazing, a roofing material, a cladding material, flooring, false ceiling. It can also include materials used in means of transport (car, train, plane, boat) especially glazing or materials for home appliances (oven walls, glazed walls of the refrigerator / freezer, ...) .

p0038Suitable substrates are very different: transparent material type glass or polymer, ceramic, ceramic, wood, metal, cement, stone, plaster face, material reconstituted from natural materials ....

p0039May also be deposited on the coating of the fibrous material of the mineral wool type of thermal and / or acoustic or any wire assembly of reinforcement, for applications in the field of filtration, for example.

p0040The coatings according to the invention are also hydrophilic, can operate according to the applications their anti-fouling function and / or bactericide / fungicide and / or anti-fogging as required.

p0041The invention also relates to the process for obtaining the coated substrate described above. Can be used, in a first variant, a technique involving thermal decomposition at least one organometallic precursor or in the form of a metal halide or metal salt. The phase deposition itself can be followed or not a post-deposition thermal treatment, for example in the order of 30 minutes to several hours at 350-550 ° C (cold deposition of sol-gel type or deposit hot pyrolysis type).

p0042In a second variant, one can use a technique of vacuum deposition, particularly sputtering, preferably magnetron sputtering. It can be reactive (from metal target / metals, alloys, with a deposit in the presence of oxidizing species at least) or non-reactive (from appropriately ceramic composition of targets).

p0043The invention will be described below in more detail using non-limiting examples and the following figures:<ul><li>√ <figref idrefs="f0001 f0002">Figures 1 to 3</figref> : Details of the likely mechanisms involving binding the driver of the invention in the level of photocatalytic activity of the coating, </li><li>√ <figref idrefs="f0003">4</figref> : A graph showing the photocatalytic activity of coatings according to the invention.</li></ul>

p0044The <figref idrefs="f0001">figure 1</figref> illustrates the first case mentioned above, namely when the driver binder includes a semiconductor oxide whose lowest level of its conduction band is below that of the TiO₂ photocatalytic. The X axis represents the electronic energy level (eV) growing, the line features full C₁ corresponds to the lowest level of the conduction band of the TiO₂ photocatalytic and the dotted line C features₂ corresponds to, for example SnO₂, Sb₂O₃ or ZnO (binder), the line C₃ corresponds to the lowest energy level of the valence band of the TiO₂ photocatalytic. The X axis is the boundary between the coating thickness (left) and its outwardly facing surface (right). The horizontal line C₄ represents the Fermi level.

p0045By photo-excitation of electrons symbolized e^-So will pass to the conduction band of the TiO₂ that, for example, SnO₂ lower in energy. The electron then tends to be supplied to the coating surface.

p0046The <figref idrefs="f0002">3</figref> represents, on a scale on the ordinate, energy (at pH = 7, in eV) from the bottom of the conduction band of various oxides, as well as levels E⁰_ox oxygen in couples O₂/ H₂O₂ and O₂/ H₂O (E⁰_ox is the most likely level, the center of a 0.8 eV width close to Gaussian). One can check that SnO₂, For example, which lies between the two levels of O pairs₂/ H₂O₂ and / or O₂/ H₂O, is well placed to make an electrochemical reduction of oxygen in H₂O₂ or H₂O with electrons it has recovered photocatalytic particles. The oxides TiO₂, Sb₂O₃, ZnO, NiO are also suitable; WO₃ and co₃O₄ are slightly lower but may still be appropriate, since they differ by less than 0.5 eV, especially less than 0.4 eV, the redox potential of O₂/ H₂O, and Co₃O₄ oxide is a known to be catalytic with respect to the reduction of oxygen.

p0047The second situation mentioned above is illustrated in Figure <figref idrefs="f0001">2</figref> In this case, with the same conventions as for <figref idrefs="f0001">figure 1</figref>, The conduction band of the conductive binder, such as ZrO₂ or Al₂O₃ is above that of TiO₂ photocatalytic. Their positions in the<figref idrefs="f0002">3</figref> does not seem theoretically favorable. In fact, these two oxides also can accommodate the electrons coming from the photocatalytic material because they possess intermediate energy states in their band gaps (symbolized in the<figref idrefs="f0001">2</figref> hatched zone along the axis X.

p0048All examples below although illustrative of the technical effect related to the invention are all related with the exception of Examples D-16, D-17, D-18 and D-20 to different substrates of the invention as defined by the appended claims.

EXAMPLES 1-5

p0049These five examples relate to a substrate of clear soda-lime-silica 3mm, surmounted by a first layer of SiOC deposited in known manner by CVD (chemical vapor deposition (chemical vapor deposition), and then a coating photocatalytic consisting of a mixed binder SiO₂ + TiO₂ coating the particles of TiO₂ preformed.

p0050The deposit is made by sol-gel, by dip-coating, as described in the pre-cited patent <patcit id="pcit0010" dnum="WO9944954A"><text>WO99 / ​​44954</text></patcit>, From a solution containing the precursors ① binder and using:<ul><li>⇒ as solvent: ethanol and ethylene glycol in weight proportions of 75/25</li><li>⇒ as stabilizer: acetylacetonate,</li><li>⇒ as a precursor of TiO₂ : Titanium tetrabutoxide (TBT)</li><li>⇒ as a precursor of SiO₂ : Tetraethylorthosilicate (TEOS) and a ② dispersion which is:</li><li>⇒ the ethylene glycol liquid phase containing crystallized photocatalytic particles, the following characteristics:<ul><li>↪ surface area of ​​the particles: ≥ 350 m²/ g</li><li>↪ particle size: ≈ 40 nm</li><li>↪ crystallite size constituting the particles: 7 nm</li><li>↪ crystalline phase: anatase greater than 80%</li></ul></li></ul>

p0051The solution was then associates ① and ② the dispersion in concentrations / ad hoc proportions for the coating in the rate of TiO₂ and SiO₂ and desired nano-particles in the binder.

p0052The photocatalytic activity of the coating was measured as follows, by using palmitic acid: A palmitic acid layer is deposited by sputtering from a chloroform solution on the plate to be tested. The amount deposited is then determined by weighing. The plate is then placed under UV irradiation (about 30 W / m²) And the blur induced by the presence of palmitic acid is measured over time. This determines the rate of disappearance of palmitic acid, expressed in nm / h. This speed may also be based on the total amount of TiO₂ (In g / cm²) Present on the glazing studied (representative of the thickness of the layer) and is then expressed by (nm / h) / (g / cm²).

p0053The coatings of the five examples all contain 50% by weight of nanoparticles of TiO₂ preformed, and 50% by weight binder distributed among SiO₂ and TiO₂. They were annealed after deposition to 500 ° C.

p0054Table 1 below shows examples for each of the following data (Example 1 binder 100% SiO₂ and thus is a comparative example): ➢ the rate of TiO₂ compared with SiO₂ in the binder, in mol% "% TiO₂ binder " ➢ the level of photocatalytic activity of coatings "AP", according to the test described, expressed in nm / h / (g / cm²), Based on the total amount of TiO₂ in the coating.<tables id="tabl0001" num="0001"><table frame="all"><title><u>Table 1</u></title><tgroup cols="3"><colspec colnum="1" colname="col1" colwidth="24mm" /><colspec colnum="2" colname="col2" colwidth="26mm" /><colspec colnum="3" colname="col3" colwidth="10mm" /><thead><row><entry align="center" valign="top">EXAMPLE</entry><entry align="center" valign="top">% TiO₂ BINDER</entry><entry align="center" valign="top">AP</entry></row></thead><tbody><row><entry align="center">1 (comparative)</entry><entry align="center">0 (100% SiO₂)</entry><entry align="char" char="." charoff="18">1.1</entry></row><row><entry align="center">2</entry><entry align="center">14</entry><entry align="char" char="." charoff="18">1.5</entry></row><row><entry align="center">3</entry><entry align="center">25</entry><entry align="char" char="." charoff="18">2.2</entry></row><row><entry align="center">4</entry><entry align="center">50</entry><entry align="char" char="." charoff="18">6.8</entry></row><row><entry align="center">5</entry><entry align="center">75</entry><entry align="char" char="." charoff="18">7.8</entry></row></tbody></tgroup></table></tables>

EXAMPLE 6

p0055This example relates to a coating deposited on the same substrate and by a technique known as "dip coating", containing 50% by weight of nanoparticles of TiO₂ preformed (those used in the preceding examples) and 50% of a binder of 100% zirconium oxide.

p0056The procedure is the following: was added as zirconium isopropoxide in isopropanol. One adds acetylacetone, and is carried out by dilution with ethanol. then this solution is mixed with a nano-particles in colloidal suspension dispersion in water acidified with nitric acid. After deposition, the coating is annealed at 500 ° C, the photocatalytic activity of the AP obtained coating, according to the convention used in the preceding examples, 2.5 nm / h / (g / cm²).

EXAMPLES 7 and 8

p0057These examples relate to coatings containing only (by weight) that 10% of preformed nanoparticles.

p0058Example 7 is the comparative example, a binder comprising 100% SiO₂The deposit is made by dip-coating.

p0059Example 8 a binder 100% SnO₂ doped with antimony.

p0060For Example 7, using a colloidal suspension of nanoparticles of TiO₂ as in Example 6 and a base TEOS solution.

p0061For Example 8, the procedure is as follows: dissolving the tin II chloride (SnCl₂) In dimethyl formamide. then dissolved antimony chloride in dimethyl formamide, was added and this second solution to the first. Is then added a colloidal suspension of nanoparticles of TiO₂ as above, whose concentration has been adjusted. The coating is applied by dip-coating. It was then reheated to 500 ° C.

p0062For Example 7, the measured photocatalytic activity PA was 0.1 nm / h / (g / cm²).

p0063For Example 8, the measured photocatalytic activity PA was 3 nm / h / (g / cm²).

p0064In this series of examples 1-8, we see that iso-amount of TiO₂Binder directly influences the photocatalytic activity of the coating while it is not (or almost) no photocatalytic itself.

p0065This is particularly striking for Example 8, which contains very few nano-particles of TiO₂ photocatalytic.

p0066Thus demonstrating the importance of the semiconductor and electronic conduction properties of the binder.

p0067For the record, the oxide electrical resistivity conductors can be recalled below be used in the context of the invention, in comparison with those of glass and SiO₂ :<tables id="tabl0002" num="0002"><table frame="none"><tgroup cols="2" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="18mm" /><colspec colnum="2" colname="col2" colwidth="12mm" /><tbody><row><entry>ZnO: Al</entry><entry>10^-3</entry></row><row><entry>SnO₂Sb</entry><entry>10^-2</entry></row><row><entry>SnO₂</entry><entry>5</entry></row><row><entry>ZrO₂</entry><entry>10⁷</entry></row><row><entry>TiO₂</entry><entry>10⁵</entry></row><row><entry>Glass</entry><entry>10¹²</entry></row><row><entry>SiO₂</entry><entry>10¹⁷</entry></row></tbody></tgroup></table></tables>

p0068Three series of examples A, B, C were then made, using a mixed binder TiO₂ + SiO₂ and nano-particles of TiO₂, Similarly to the series of Examples 1 to 5 (same filing mode, same precursors).

p0069Table 2 below summarizes, for each sample of each series, (percentages are by weight)<ul><li>➢ The% TiO₂ nano-particle</li><li>➢ The% TiO₂ binder</li><li>➢ The% SiO₂ binder</li></ul> - The value of photocatalytic activity of the coating as a whole AP ', expressed in nm / h, the photocatalytic activity value of the added coating to the total amount of TiO₂ AP in the coating expressed in nm / h / (g / cm²), And the quantity Q of TiO₂ (Contained in the nano-particles and binder) in the coating expressed in g / cm².<tables id="tabl0003" num="0003"><table frame="all"><title><u>Table 2</u></title><tgroup cols="6"><colspec colnum="1" colname="col1" colwidth="29mm" /><colspec colnum="2" colname="col2" colwidth="30mm" /><colspec colnum="3" colname="col3" colwidth="30mm" /><colspec colnum="4" colname="col4" colwidth="20mm" /><colspec colnum="5" colname="col5" colwidth="29mm" /><colspec colnum="6" colname="col6" colwidth="30mm" /><thead><row><entry align="center" valign="middle">% TiO₂ nano-particle</entry><entry align="center" valign="middle">% TiO₂ in the binder</entry><entry align="center" valign="middle">% SiO₂ in the binder</entry><entry align="center" valign="middle">AP 'nm.h^-1</entry><entry align="center" valign="middle">Q = amount of TiO₂ (Nanoparticles + binder) / μg.cm^-2</entry><entry align="center" valign="middle">AP nm.h^-1.μg^-1.cm²</entry></row></thead><tbody><row><entry namest="col1" nameend="col6" align="center" valign="middle" /></row><row><entry valign="middle">series A</entry><entry valign="middle" /><entry valign="middle" /><entry valign="middle" /><entry valign="middle" /><entry valign="middle" /></row><row><entry align="center" valign="middle">0</entry><entry align="center" valign="middle">100</entry><entry align="center" valign="middle">0</entry><entry align="center" valign="middle">18</entry><entry align="center" valign="middle">22.3</entry><entry align="center" valign="middle">0.81</entry></row><row><entry align="center" valign="middle">20</entry><entry align="center" valign="middle">100</entry><entry align="center" valign="middle">0</entry><entry align="center" valign="middle">128</entry><entry align="center" valign="middle">23.7</entry><entry align="center" valign="middle">5.40</entry></row><row><entry align="center" valign="middle">35</entry><entry align="center" valign="middle">100</entry><entry align="center" valign="middle">0</entry><entry align="center" valign="middle">159</entry><entry align="center" valign="middle">22.9</entry><entry align="center" valign="middle">6.94</entry></row><row><entry align="center" valign="middle">50</entry><entry align="center" valign="middle">100</entry><entry align="center" valign="middle">0</entry><entry align="center" valign="middle">231</entry><entry align="center" valign="middle">24.8</entry><entry align="center" valign="middle">9.30</entry></row><row><entry align="center" valign="middle">65</entry><entry align="center" valign="middle">100</entry><entry align="center" valign="middle">0</entry><entry align="center" valign="middle">210</entry><entry align="center" valign="middle">24.1</entry><entry align="center" valign="middle">8.71</entry></row><row><entry align="center" valign="middle">80</entry><entry align="center" valign="middle">100</entry><entry align="center" valign="middle">0</entry><entry align="center" valign="middle">167</entry><entry align="center" valign="middle">18.5</entry><entry align="center" valign="middle">9.03</entry></row><row><entry align="center" valign="middle">100</entry><entry align="center" valign="middle">100</entry><entry align="center" valign="middle">0</entry><entry align="center" valign="middle">222</entry><entry align="center" valign="middle">22.7</entry><entry align="center" valign="middle">9.78</entry></row><row><entry namest="col1" nameend="col6" align="center" valign="middle" /></row><row><entry valign="middle">series B</entry><entry valign="middle" /><entry valign="middle" /><entry valign="middle" /><entry valign="middle" /><entry valign="middle" /></row><row><entry align="center" valign="middle">0</entry><entry align="center" valign="middle">14</entry><entry align="center" valign="middle">86</entry><entry align="center" valign="middle">0</entry><entry align="center" valign="middle">1</entry><entry align="center" valign="middle">0</entry></row><row><entry align="center" valign="middle">10</entry><entry align="center" valign="middle">14</entry><entry align="center" valign="middle">86</entry><entry align="center" valign="middle">0</entry><entry align="center" valign="middle">8.3</entry><entry align="center" valign="middle">0</entry></row><row><entry align="center" valign="middle">25</entry><entry align="center" valign="middle">14</entry><entry align="center" valign="middle">86</entry><entry align="center" valign="middle">0</entry><entry align="center" valign="middle">17.6</entry><entry align="center" valign="middle">0</entry></row><row><entry align="center" valign="middle">50</entry><entry align="center" valign="middle">14</entry><entry align="center" valign="middle">86</entry><entry align="center" valign="middle">58</entry><entry align="center" valign="middle">32.7</entry><entry align="center" valign="middle">1.77</entry></row><row><entry align="center" valign="middle">75</entry><entry align="center" valign="middle">14</entry><entry align="center" valign="middle">86</entry><entry align="center" valign="middle">233</entry><entry align="center" valign="middle">42.1</entry><entry align="center" valign="middle">5.53</entry></row><row><entry align="center" valign="middle">90</entry><entry align="center" valign="middle">14</entry><entry align="center" valign="middle">86</entry><entry align="center" valign="middle">535</entry><entry align="center" valign="middle">49.7</entry><entry align="center" valign="middle">10.77</entry></row><row><entry namest="col1" nameend="col6" align="center" valign="middle" /></row><row><entry valign="middle">series C</entry><entry valign="middle" /><entry valign="middle" /><entry valign="middle" /><entry valign="middle" /><entry valign="middle" /></row><row><entry align="center" valign="middle">50</entry><entry align="center" valign="middle">14</entry><entry align="center" valign="middle">86</entry><entry align="center" valign="middle">15</entry><entry align="center" valign="middle">9.7</entry><entry align="center" valign="middle">1.55</entry></row><row><entry align="center" valign="middle">50</entry><entry align="center" valign="middle">25</entry><entry align="center" valign="middle">75</entry><entry align="center" valign="middle">25</entry><entry align="center" valign="middle">11.3</entry><entry align="center" valign="middle">2.21</entry></row><row><entry align="center" valign="middle">50</entry><entry align="center" valign="middle">50</entry><entry align="center" valign="middle">50</entry><entry align="center" valign="middle">88</entry><entry align="center" valign="middle">12.9</entry><entry align="center" valign="middle">6.82</entry></row><row><entry align="center" valign="middle">50</entry><entry align="center" valign="middle">75</entry><entry align="center" valign="middle">25</entry><entry align="center" valign="middle">137</entry><entry align="center" valign="middle">17.5</entry><entry align="center" valign="middle">7.83</entry></row></tbody></tgroup></table></tables>

p0070The <figref idrefs="f0003">4</figref> shows in the form of a graph the photocatalytic activity of the coatings: the abscissa is represented the percentage by weight of nanoparticles in the coating, and in ordinate the value AP: it puts quite clear that the more TiO₂ in the binder, plus the photocatalytic activity increases (C series). Comparison of Series B and Series C shows that the amount of electronically conductive material in the binder also has a significant impact on the level of photocatalytic activity of the coating that the amount of nanoparticles of TiO₂.

EXAMPLES ACCORDING TO A SERIES

p0071A final series of examples relates to the variant in which the TiO₂ photocatalytic is generated in situ by thermal decomposition of precursors adhoc and at least partially crystallized (which may require a post-deposition annealing).

p0072These examples use various types of binder apart TiO₂. TiO₂ from thermal decomposition of precursors is partly crystallized anatase (photocatalytic) and partially amorphous. Deposits are made by liquid pyrolysis on a glass substrate already used for the previous examples.

p0073Table 3 below lists each of the examples in this series:<ul><li>➢ The type of binder (Sb formula₂O_x means this is either Sb₂O₃ or Sb₂O₅, The oxygen stoichiometry was not measured)</li><li>➢ The amount of TiO₂ in coatings (as measured by X-ray fluorescence: expressed in g / cm² : Q_TiO2</li><li>➢ The AP value as defined above, in nm / h / (g / cm²)</li><li>➢ The total amount of the coating material, also expressed in g / cm² : Q_EARLY</li></ul>

p0074For all these examples, the proportion of the TiO₂ (Whether crystalline or amorphous) and the other coating components (binder) is 90 mol% TiO₂ to 10 mol% of Si or another metal following the examples.<tables id="tabl0004" num="0004"><table frame="all"><title><u>Table 3</u></title><tgroup cols="5"><colspec colnum="1" colname="col1" colwidth="23mm" /><colspec colnum="2" colname="col2" colwidth="13mm" /><colspec colnum="3" colname="col3" colwidth="13mm" /><colspec colnum="4" colname="col4" colwidth="17mm" /><colspec colnum="5" colname="col5" colwidth="12mm" /><thead><row><entry align="center" valign="top">EXAMPLES</entry><entry align="center" valign="top">Q_TIO2</entry><entry align="center" valign="top">Q_EARLY</entry><entry align="center" valign="top">BINDER</entry><entry align="center" valign="top">AP</entry></row></thead><tbody><row><entry align="center">D-10</entry><entry align="char" char="." charoff="28">15.4</entry><entry align="char" char="." charoff="29">15.4</entry><entry align="center">TiO₂</entry><entry align="center">19.4</entry></row><row><entry align="center">D-11</entry><entry align="char" char="." charoff="28">12.1</entry><entry align="char" char="." charoff="29">14.6</entry><entry align="center">SnO₂</entry><entry align="center">11.5</entry></row><row><entry align="center">D-12</entry><entry align="char" char="." charoff="28">12.4</entry><entry align="char" char="." charoff="29">15.0</entry><entry align="center">SnO₂F</entry><entry align="center">12.5</entry></row><row><entry align="center">D-13</entry><entry align="char" char="." charoff="28">11.1</entry><entry align="char" char="." charoff="29">12.7</entry><entry align="center">al₂O₃</entry><entry align="center">4.8</entry></row><row><entry align="center">D-14</entry><entry align="char" char="." charoff="28">11.8</entry><entry align="char" char="." charoff="29">13.5</entry><entry align="center">al₂O₃F</entry><entry align="center">4.7</entry></row><row><entry align="center">D-15</entry><entry align="char" char="." charoff="28">15.8</entry><entry align="char" char="." charoff="29">18.5</entry><entry align="center">ZrO₂</entry><entry align="center">17.8</entry></row><row><entry align="center">D-16</entry><entry align="char" char="." charoff="28">16.0</entry><entry align="char" char="." charoff="29">18.7</entry><entry align="center">ZrO₂F</entry><entry align="center">20.0</entry></row><row><entry align="center">D-17</entry><entry align="char" char="." charoff="28">19.5</entry><entry align="char" char="." charoff="29">25.0</entry><entry align="center">sb₂O_x</entry><entry align="center">3.0</entry></row><row><entry align="center">D-18</entry><entry align="char" char="." charoff="28">17.0</entry><entry align="char" char="." charoff="29">21.8</entry><entry align="center">sb₂O_xF</entry><entry align="center">1.5</entry></row><row><entry align="center">D-19</entry><entry align="char" char="." charoff="28">19.6</entry><entry align="char" char="." charoff="29">21.8</entry><entry align="center">ZnO</entry><entry align="center">1.8</entry></row><row><entry align="center">D-20</entry><entry align="char" char="." charoff="28">20.3</entry><entry align="char" char="." charoff="29">22.6</entry><entry align="center">ZnO: F</entry><entry align="center">2.2</entry></row></tbody></tgroup></table></tables>

p0075The precursors for each of these examples are precursors of organo-metallic type, metal halide or salt, known from the literature. For Example D-10 consisting entirely of TiO₂, It is the same precursor as in Examples 1 to 5.

p0076Table 4 below lists these examples for the light transmission values ​​T_L measured under illuminant D₆₅ glasses thus coated, and the R light reflection values_L (Even illuminant). It also indicates the transmission value T broadcasts_d also in%, and the value of Delta T_d, Which corresponds to the variation of diffuse transmission of the coatings after being subjected to mechanical abrasion after the test: is subjected to the coating dry friction test comprising moving back and forth in combination with a proper rotation of a cylinder loaded. The cylinder load is 390 g / cm²The speed back and forth is 50 trips / returns per minute, and the spin rate is 6 rpm. The value of Td is measured after 500 cycles back and forth.<tables id="tabl0005" num="0005"><table frame="all"><title><u>Table 4</u></title><tgroup cols="5"><colspec colnum="1" colname="col1" colwidth="23mm" /><colspec colnum="2" colname="col2" colwidth="12mm" /><colspec colnum="3" colname="col3" colwidth="12mm" /><colspec colnum="4" colname="col4" colwidth="10mm" /><colspec colnum="5" colname="col5" colwidth="16mm" /><thead><row><entry align="center" valign="top">EXAMPLES</entry><entry align="center" valign="top">tl</entry><entry align="center" valign="top">Services</entry><entry align="center" valign="top">T_d</entry><entry align="center" valign="top">delta T_d</entry></row></thead><tbody><row><entry align="center">D-10</entry><entry align="char" char="." charoff="32">83.3</entry><entry align="char" char="." charoff="32">16.2</entry><entry align="char" char="." charoff="18">0.5</entry><entry align="char" char="." charoff="12">0.6</entry></row><row><entry align="center">D-11</entry><entry align="char" char="." charoff="32">86.7</entry><entry align="char" char="." charoff="32">13.1</entry><entry align="char" char="." charoff="18">0.2</entry><entry align="char" char="." charoff="12">0.9</entry></row><row><entry align="center">D-12</entry><entry align="char" char="." charoff="32">86.3</entry><entry align="char" char="." charoff="32">13.4</entry><entry align="char" char="." charoff="18">0.3</entry><entry align="char" char="." charoff="12">0.5</entry></row><row><entry align="center">D-13</entry><entry align="char" char="." charoff="32">87.3</entry><entry align="char" char="." charoff="32">12.5</entry><entry align="char" char="." charoff="18">0.2</entry><entry align="char" char="." charoff="12">3.5</entry></row><row><entry align="center">D-14</entry><entry align="char" char="." charoff="32">86.3</entry><entry align="char" char="." charoff="32">13.5</entry><entry align="char" char="." charoff="18">0.2</entry><entry align="char" char="." charoff="12">2.6</entry></row><row><entry align="center">D-15</entry><entry align="char" char="." charoff="32">81.2</entry><entry align="char" char="." charoff="32">18.5</entry><entry align="char" char="." charoff="18">0.3</entry><entry align="char" char="." charoff="12">1.2</entry></row><row><entry align="center">D-16</entry><entry align="char" char="." charoff="32">80.9</entry><entry align="char" char="." charoff="32">18.8</entry><entry align="char" char="." charoff="18">0.3</entry><entry align="char" char="." charoff="12">0.6</entry></row><row><entry align="center">D-17</entry><entry align="char" char="." charoff="32">81.9</entry><entry align="char" char="." charoff="32">17.6</entry><entry align="char" char="." charoff="18">0.5</entry><entry align="char" char="." charoff="12">0.3</entry></row><row><entry align="center">D-18</entry><entry align="char" char="." charoff="32">83.2</entry><entry align="char" char="." charoff="32">15.1</entry><entry align="char" char="." charoff="18">1.7</entry><entry align="char" char="." charoff="12">1.2</entry></row><row><entry align="center">D-19</entry><entry align="char" char="." charoff="32">81.9</entry><entry align="char" char="." charoff="32">17.4</entry><entry align="char" char="." charoff="18">0.7</entry><entry align="char" char="." charoff="12">0.4</entry></row><row><entry align="center">D-20</entry><entry align="char" char="." charoff="32">81.3</entry><entry align="char" char="." charoff="32">18.3</entry><entry align="char" char="." charoff="18">0.4</entry><entry align="char" char="." charoff="12">1.3</entry></row></tbody></tgroup></table></tables>

p0077These results confirm the previous ones: binders "conductors" can improve within wide limits the performance of photocatalytic coatings, in obtaining further coatings resistant to abrasion and of good optical quality.

p0078In conclusion, all these results show that one can select the best conductors binders according to the invention, which allow to evacuate particles / photocatalytic crystalline domains the photo-generated electrons, and operate in the coating advantageous redox reactions.