Substrate with photocatalytic coating

The Invention relates to substrates based on glass, ceramics or Glass ceramics, in particular of glass, and especially transparent are, and which is provided with coatings with photocatalytic properties are to glasses for different manufacture uses as utility glass, automotive glass or building glass.

It more and more is desired, glasses to be provided with functions by on their surface thin films be applied, which for are determined, they intend to apply depending on the application a to impart special properties. So are layers with optical Function as anti-reflective layers made from a build-up layers consist of alternating high and low refractive index available. For an antistatic or heating function of type defrosting, electrically conductive thin layers, For example, on the basis of a metal or a doped Metal oxide, are provided. For a thermal function, For example, a low-emissivity or solar control, can on thin Layers of a metal of the type of silver or based on a Metal nitride or metal oxide be used. to get rain repellent function layers with hydrophobic Character, for example, based on a fluorinated organosilane, be provided.

It However, there is still a need for a substrate, especially a glass, which are referred to as "dirt-repellent" can, that is, the condition during the time remaining concerning appearance and surface properties having and it particularly allows the spaces between to extend Cleaners and / or to improve viewing by the contaminants, that have come in time to the substrate surface, in particular Contamination of organic origin, such as fingerprints, in the atmosphere existing Peek ge Organics or dirt type fitting, according be removed.

there It is known that certain semiconductor metal oxide on the basis of a exist which are able under the influence of radiation with an appropriate wavelength initiate free radical reactions, which cause the oxidation of organic products, which in Generally speaking of "photocatalytic" or "photoreactive" materials becomes.

That's why the invention is an object of photocatalytic coatings providing on a substrate a pronounced antisoiling have effect on the substrate and are produced industrially can.

The Invention has for its object a substrate based on glass, Ceramic or glass-ceramic, especially of a transparent glass, the at least a portion of at least one side with a coating is provided with photocatalytic properties, the least comprising partially crystallized titanium oxide. In this case, the titanium oxide is in situ during the formation of the coating is crystallized on the substrate. The coating is the last layer of an antireflection layer structure.

titanium oxide belongs to the semiconductors, the visible under the action of light in the or ultraviolet range organic products on their surface have deposited degrade. The choice of titanium oxide, a dirt-repellent produce glass, therefore is particularly indicated, and all the more so this oxide as a good mechanical and chemical resistance comprises, as it in order to remain effective for long periods, of course, is important that the coating retains its integrity even when, particularly in the installation of the glass plate on the construction site (Building) or on the production line (vehicle), which means that repeated manipulation with mechanical or pneumatic gripping means means and also, after the glass pane is in its place, with the risk abrasion (wipers and cloths) and the contact with aggressive chemical substances (for example, atmospheric pollutants by type SO₂ and toiletries), direct numerous is under attack.

The Selection extends also a titanium oxide which is at least partially crystallized, because it has been shown that in terms of photocatalytic Features more powerful is an amorphous titanium oxide. Preferably, it is in the anatase form, Rutile or anatase-rutile mixture with a degree of crystallization of at least 25% and especially about 30 to 80%, in particular in nearby the surface crystallized, (This feature is more of a surface property). (Under the Degree of crystallization is the amount by weight TiO₂ to understand the weight-based on the total TiO₂-Amount is crystallized in the coating.)

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furthermore it has been found, particularly during crystallization in Anatase form that the orientation of the TiO₂crystals, grown on the substrate, an influence on the photocatalytic Properties of the oxide have as a preferred direction (1, 1, 0) exists, which clearly favors the photocatalysis.

Advantageously, is the preparation of the coating carried out so that the crystallized titanium oxide which it contains, in the form of "crystallites" at least at the Surface, ie in the form of single crystals with an average size of 0.5 to 100 nm, preferably 1 to 50 nm, especially 10 to 40 nm, and especially 20 to 30 nm, is present. In this size range has the titanium oxide optimum photocatalytic effect, probably due to the fact that the crystallites of this size a considerable active surface develop.

As further will become clear below, the coating on the Based on titanium oxide can be obtained in several ways: <ul><li>- by Decomposition of titanium precursors (Pyrolysis: Flüssigpyrolyse, Powder pyrolysis and chemical vapor deposition, CVD (Chemical Vapor Deposition) and sol-gel method: for example, dipping or dipping and Cell Coating) and</li><li>- on Vacuum process (optionally reactive sputtering).</li></ul>

The Coating can also save the crystallized titanium oxide at least one other type of inorganic Material, especially in the form of an amorphous or partially crystallized Oxide, for example, an oxide (or oxide mixture) of silicon, Titanium, tin, zirconium or aluminum, included. This inorganic Material can also be the photocatalytic effect of the crystallized Titanium oxide contribute, by his hand, a certain photocatalytic Effect exerts even if this against the the crystallized TiO₂ is low, which applies to tin oxide or amorphous titanium oxide.

A "mixed oxide", in which at least partially crystallized titanium oxide with at least one other combined oxide, may be visually interesting, especially when the other or another oxide / e having a refractive index of less than that of the TiO₂ to get voted: By the "global" index of refraction Coating is lowered, the light reflectance of the coating provided substrate can be influenced and in particular reduced. This is for example the case when a TiO₂/ Al₂O₃Film, which a method of production in the Patent EP-0465309 describes or TiO₂/ SiO₂-Layer chosen becomes. It is of course necessary that the coating, however, a TiO₂-Salary contains, sufficient in order to retain a significant photocatalytic activity. So will believed that it is preferred that the coating comprises at least 40 wt .-% and especially at least 50 wt .-% of TiO₂. based on the total weight of oxide / s in the coating contains.

one can be also decide on the coating of the invention an oleophobic and / or applying hydrophobic layer or stably anchored with respect to the Photocatalysis is resistant, for example based on the fluorinated organosilane in patents US-5 368 is described 892 and US 5,389,427, and the Perfluoralkylsilans that in patent application FR-94/08734 is described on 13 July 1994, under the number FR-2722 published 493 is and the European Patent EP-0692463 corresponds, in particular having the formula: <st32:che xmlns:st32="http://lighthouseip.com/">CF₃- (CF₂)_n- (CH₂)_m--SiX₃. </st32:che>in wherein n is 0 to 12, m is 2 to 5 and X a hydrolysable group means.

Around the photocatalytic effect of the titanium oxide coating according to the invention amplify, can first the absorption band of the coating can be increased by the coating other particles, especially metallic based on cadmium, Tin, tungsten, zinc, cerium or zirconium, can be installed.

It can also the number of charge carriers by doping the crystal lattice of titanium oxide to be increased, wherein at least one of the following metallic elements incorporated is: niobium, tantalum, iron, bismuth, cobalt, nickel, copper, ruthenium, Cerium and molybdenum.

This may doping by an exclusive Oberflächendotieren of the titanium oxide or of the total coating take place, said Oberflächendotieren accomplished is by at least a portion of the coating with a layer is covered from metal oxides or salts, the metal being from Iron, &lt;?page 4?&gt;Copper, ruthenium, cerium, molybdenum, vanadium and bismuth is selected.

Finally, the photocatalytic phenomenon reinforced be by the yield and / or the kinetics of the photocatalytic increased reactions is by the titanium oxide or at least part of the surface which it contains, with egg nem noble metal such as platinum, rhodium, silver and palladium in Form of a thin layer is covered.

On Such a catalyst, for example, by a vacuum process is applied, allows the number and / or life of the free-radical entities to increase, produced by the titanium oxide, and the chain reactions favor, deplete organic products result.

Surprisingly has the coating not only a property, but two, when exposed to an appropriate radiation, as in Range of visible and / or ultraviolet light such as a Sunlight: by the presence of the photocatalytic Titanium oxide, as already seen, the progressive removal of contamination of organic origin according to their collection favors, by their degradation is caused by free radical oxidation. The inorganic contaminants are not through this process degraded, they therefore remain on the surface and, apart from certain Crystallization forms, they are partially removed easily because they are no longer on the surface adhere, as the adhesive organic substances are degraded by photocatalysis.

The inventive coating, the constantly cleans itself, but also preferably has an outside with a strong hydrophilic and / or oleophilic character, leading to three very advantageous Effects results: <ul><li>- on hydrophilic character allows perfect wetting with water, which can be deposited on the coating; if water condensation instead of depositing droplets of water in the form of fog, which interferes with the phantom, occurs, produces a continuous thin film of water on themselves the surface the coating forms and completely is transparent; this fog-repellent effect is particularly shown by the measurement of a contact angle with water after Light irradiation is smaller than 5 °, and</li><li>- after Sprinkling with water, especially after the impact of rain, on a surface that have not been treated with a photocatalytic layer is liable numerous rain droplets on the surface and left after evaporation tracks that unsightly, annoying and mainly inorganic origin; , Exposed to a surface, the ambient air is covered quickly with a layer of dirt which their Wetting limited with water; these contaminants come to the other, particularly inorganic Contamination (eg crystallisation) added that from the atmosphere, in which the glazing is to be contributed; at a photoreactive surface these inorganic contaminants not directly by the Photocatalysis decomposed; they are to a very large extent eliminated by the hydrophilic character, the photocatalytic of the activity caused; This hydrophilic character causes a complete homogenization of the Rain droplets; evaporation tracks are therefore no longer exists; also be the other on the surface washed existing inorganic contaminants or dissolve at a crystallization through the film of water and are therefore to a large Part removed; it is a inorganic dirt-repellent Effect achieved, which is particularly caused by the rain,</li><li>- together with a hydrophilic nature, the coating can also be a have oleophilic character, which allows the "wetting" with organic contaminants, which, as in the water, then tend to the coating deposit in the form of a continuous film which is less visible than the well-localized "traces" is; it is so an "organic Dirt repellent effect "received, which takes place in two stages; if the contamination on the coating is deposited, it is already less visible; after all it disappears progressively through triggered by photocatalysis radical Degradation.</li></ul>

The Coating can also be selected with a more or less smooth surface. Here, a certain roughness be advantageous: <ul><li>- they allows a larger photocatalytically active surface to develop and lead thus a higher photocatalytic activity and</li><li>- they has a direct impact on the wetting; the roughness exceeds wetting properties; a hydrophilic surface is smooth still hydrophilic after it has been made rougher; it is here under "roughness" both the surface roughness as well as to understand the roughness of the Po&lt;?page 5?&gt;rosität the layer over at least part of its thickness is caused.</li></ul>

These Effects are more pronounced, more porous and rougher the coating is why a super hydrophilic effect the rough photoreactive surfaces occurs. However, too pronounced roughness be disruptive, by favoring the encrustation and accumulation of dirt and / or caused an optically unacceptable veil.

It has proved to be so interesting, the way of applying the coatings on the basis of TiO₂ so adjust to have a surface roughness of about 2 to 20 nm and preferably having 5 to 15 nm, this roughness by atomic force microscopy by measuring the mean square error (english "Root Mean Square or RMS ") on a area is determined by one square micrometer. With such roughness the coatings a hydrophilic character, which expresses in a contact angle with water, which may be less than 1 °. Furthermore, it has been found that it is advantageous to use a certain porosity to favor in the thickness of the coating. Thus, the coating, if they only TiO₂ is, preferably a porosity from about 65 to 99% and in particular from 70 to 90%, with the porosity here indirectly as a percentage of the theoretical density of the TiO₂Which is about 3.8, is defined. to such porosity to favor, there is a means, for example, therein, the coating by applying a sol-gel method, at which the decomposition of organometallic Materials involved: It can be in the solution besides / organometallic Precursor / n an organic polymer are the type of polyethylene glycol, PEG, introduced wherein if the layer is cured by heating, the PEG burns, which a certain porosity caused in the thickness of the layer or these increases.

The Thickness of the coating according to the invention is variable, it is preferably 5 nm to 1 micron, particularly between 5 and 100 nm, especially between 10 and 80 nm or between 20 and 50 nm. The choice of the thickness can depend on various parameters, in particular of the intended use of the substrate type glazing, the size of the TiO₂crystallites in the coating or the presence of alkali metal ions with a high proportion in the substrate.

In between Substrate and coating according to the invention can one or more additional thin layers with a function different from that of the coating is or supplements the latter, be applied. It may be in particular layers with an antistatic, thermal, optical, or with a function, the crystal growth of TiO₂ in shape promotes anatase or rutile, or involve layers as barrier to the migration certain elements coming from the substrate, in particular as Barrier against alkali metal ions and especially for sodium ions, when the substrate is made of glass, are used.

In an antireflection-layer structure in which thin layers of high and low refractive index alternate, the inventive coating forms the final layer of the structure. In this case, it is preferred that the coating has a relatively not so high refractive index has, which is the case when a Titansiliciummischoxid consists.

The Layer with antistatic and / or thermal function (for example, be heated by it has been provided with power supply lines, low-emitting and sun protection function) may in particular selected be based on a conductive Material type metal such as silver or type doped metal as tin-doped indium oxide, ITO, with a halogen type Fluorine-doped tin oxide, SnO₂: F, antimony doped tin oxide, SnO₂: Sb, or indium doped zinc oxide ZnO: In, with fluorine ZnO: F, with aluminum ZnO: Al, or with tin, ZnO: Sn, doped zinc oxide. It may also to stoichiometric oxygen Metal oxides such as SnO_2-x or ZnO_2x. with x &lt;2, act.

The Layer with antistatic function preferably has a surface resistivity from 20 to 1000 ohms / square. It can supply leads be provided in order to polarize it (supply voltages for example, 5 to 100 V). This controlled polarization in particular allows the deposition of dust particles with a Size of about 1 mm, which are able to deposit on the coating, in particular of dry dust, the electrostatic by the Effect adhere to prevent: By the polarization of the layer suddenly is reversed, these dust particles are repelled.

The thin layer optical function can be selected to the light reflectance to reduce and / or the coloring to make the substrate in reflection neutral. It has in this case to&lt;?page 6?&gt;preferably an index of refraction between that of the coating and that of the substrate is located, has a suitable optical thickness and can be made of an oxide or mixed oxide type alumina Al₂O₃. Tin oxide, SnO₂, Indium oxide, In₂O₃, Oxycarbide or oxynitride consist. To a maximum attenuation of coloring to get at the reflection, It is preferable that this thin Layer has an index of refraction close to the square root from the product of the squares of the refractive indices of the two materials, surround it, ie the substrate and the coating according to the invention, lies. Parallel, it is advantageous, its optical thickness (ie, Product of geometrical thickness and to select Brechungsin dex) near λ / 4, where Lambda approximately the average wavelength in the visible region, particularly from about 500 to 550 nm is.

The thin layer with barrier protection against alkali metal ions can in particular based on silicon oxide, nitride, oxynitride or -carbidoxid, Alumina containing fluorine, Al₂O₃: F, or selected from aluminum nitride will. She has proven to be useful proved, when the substrate is made of glass, because the migration by of sodium ions into the coating according to the invention under certain Conditions the photocatalytic properties are changed can.

Of the Nature of the substrate or the underlayer is also of additional Interest: He, the crystallization of the photocatalytic layer favor, in particular, when it is applied by CVD.

If TiO₂ is deposited by CVD, favors Sublayer crystallized SnO₂: F the growth of TiO₂ in the form of predominantly Rutile, in particular at deposition temperatures of about 400 to 500 ° C, while the surface a soda lime silicate glass or a silicon oxycarbide sublayer rather a Anataswachstum, especially at deposition of about 400 to 600 ° C, triggers.

All these optional thin layers in a known manner by vacuum process type sputtering or by methods other type thermal decomposition such as pyrolysis from the solid, liquid or gas phase are applied. In this case, each of the aforementioned Layers combine several functions on itself, but they can also superimposed Arrange.

The Invention further has "dirt-repellent" (organic and / or inorganic soils) and / or "fog-resistant" glass, the monolithic and Mehrfachisolierverglasungen composite glazing type double glazing or Ver are and in which the coated substrates described above are installed to the object.

The Invention thus relates to the manufacture of glass, ceramic or Glass-ceramic products, particularly directed to the manufacture of "self-cleaning" glazing. these can advantageously architectural glazings as double glazing to be (the coating can then on the "outside" and / or "inside", ie to position 1 and / or 4-position, arranged). This proves to be particularly interesting for glazings for cleaning poorly accessible and / or a very common require cleaning as roofing and glazing airport. In this case, it also be vehicle glazing where maintaining the review is an essential safety criterion. The coating can so on the windscreen, side windows or rear window a car are arranged, and in particular to the interior of the the cabin-facing side of the glazing. This coating can then prevent the formation of fog and / or traces of dirt type traces of fingers, nicotine or organic material from type volatile Plasticizer, which escapes from the plastic, with which the interior covered the passenger compartment is, in particular that of the dashboard (an escape, the known sometimes under the English name "fogging" is), remove. Other trucks such as airplanes, trains, can also interesting for provided the use of coating according to the invention with the be glazing.

Numerous other uses are possible, especially for Aquariums glasses, Shop windows, greenhouses, verandas, glasses, the for the interior or street furniture be used, as well as mirrors, television screens, eyeglasses or any building material, for example of the facade, Fassadenverkleidungs- and roofing materials as roofing tiles.

The Invention thus allows to functionalize these known products, by them for example against UV radiation protective, dirt-repellent, bactericidal, antistatic, antimicrobial and anti-reflective properties are awarded.

&lt;?page 7?&gt;

A Another interesting use of the coating according to the invention is with a glass with electrically controlled variable absorption electrochromic type glass, liquid crystal glass, optionally with two-tone dye, glass with a system to connect from suspended particles and Viologenglas. All these glasses are generally composed of a plurality of transparent substrates, arranged between which the "active" elements are; the coating can then advantageously on the outside at least one of the substrates are placed.

Especially resulting in an electrochromic glazing, when the colored state to is, their absorption at a certain superficial Warming, which is capable of the photocatalytic decomposition of the carbonaceous Substances that have been deposited on the coating of the invention, to accelerate. Because closer Details of the construction of an electrochromic glazing can advantageously from the patent application EP-A-0575207 teach, in which describes an electrochromic double laminated glazing , wherein the coating of the invention preferably may be located in position. 1

The Invention also has the different procedures for the preparation of coating according to the invention to the object. It can be a deposition type pyrolysis be applied, which is interesting because it is particularly the continuous Applying the coating allowed directly on the float glass ribbon, when a glass substrate is used.

The Pyrolysis can from the solid phase, starting from metal-organic / organometallic powder / powdered precursor / n are performed.

The Pyrolysis may from the liquid phase starting from a solution accomplished be that or an organometallic titanium precursor of the type titanium chelate and / Titanium alcoholate contains. Such precursors are mixed with at least one other organometallic precursor. Because closer Details of the nature of the titanium precursor or on the deposition conditions you can, for example, in Patents FR-2,310,977 and EP-0 465 309 teach.

The Pyrolysis may further as vapor deposition, a process, the also known CVD (Chemical Vapor Deposition) known is, starting from at least one titanium precursor of type halide such TiCl₄ or titanium alcoholate type Ti tetraisopropylate, Ti (OiPr)₄, be performed. crystallization the layer may also are controlled by the type of sublayer, as explained above.

The Coating can also be applied by other methods, in particular Sol-gel process. Various Abscheidearten are possible, as well as "dip-coating" called "diving" or the deposition by means of a cell, which is called "Cell-coating". It can also be a "spray coating" or a roller application act, the latter method is described in detail in the patent application WO-94/01598 described. In all of these deposition methods is in general, a solution used, the at least one organometallic precursor, in particular titanium alcoholate type contains, which after coating the substrate with the solution thermally decomposed on one of its sides or on both sides becomes.

furthermore it can be interesting, the coating regardless of the coating method not at once, but sequentially in at least two following deposit levels, which the crystallization of titanium oxide on the total thickness of the coating, if this has been selected to be relatively thick is, seems to promote.

furthermore it is advantageous that the coating having photocatalytic properties after applying a heat treatment type annealing to subjugate. Heat treatment is essential organometallic in a sol-gel method or a roll applicator, to the / the precursor reducing to an oxide, after the coating of the substrate accomplished has been, and to improve the abrasion resistance, which is not the Case is when a pyrolysis method has been applied, in which the precursor is degraded, when it is with the substrate into contact. In the first as in the second case, however, by a heat treatment after the coating operation after formation of the TiO₂ its Degree of crystallization increases. In this case, the selected Treatment temperature, it also allow crystallization degree and crystalline character, anatase and / or rutile, of the oxide adjust better.

however can with a substrate of soda lime silicate glass more and extended Glühvor&lt;?page 8?&gt;puts a Reducing the photocatalytic activity due to a large migration favor of alkali ions from the substrate into the photoreactive layer. The use of a barrier layer between the substrate when it consists of a standard glass and the coating, the choice a glass substrate with adequate entalkalinisiert composition or the choice of a soda-lime silicate glass, its surface is it possible to eliminate this danger.

More advantageous features of the invention and details will be apparent from the following description of exemplary embodiments explained in more detail with reference to the figures in the appendix, wherein

<figref idrefs="S33">1</figref> a Section provided by a coating according to the invention with a Glass substrate,

<figref idrefs="S33">2</figref> on Diagram of a sol-gel coating process, the "dip-coating" or "dip-coating" is called,

<figref idrefs="S33">3</figref> on Scheme of an offer called "Cell-coating" the coating method,

<figref idrefs="S34">4</figref> on Scheme of an offer called "spray coating" coating process and

<figref idrefs="S34">5</figref> on Scheme of a roll-coating method shows.

As very schematically in <figref idrefs="S33">1</figref> shown, affect all following examples applying a "dirt-repellent" coating <figref>3</figref>. essentially based on titanium oxide, on a transparent substrate <figref>1</figref>,

The substratum <figref>1</figref> consists of a soda lime silicate clear glass with a thickness of 4 mm and a length and width of 50 cm. there it goes without saying, that the invention is not limited to this specific type of glass. also the glass may plan, but also be curved.

In between coating <figref>3</figref> and substrate <figref>1</figref> There is a optional thin layer <figref>2</figref>, Either based on silicon oxycarbide, SiOC to provide a barrier against the diffusion of alkali metal ions form, and / or a light reflection attenuating layer, or based on fluorine-doped tin oxide, SnO₂: F to an antistatic and / or low to form emitting layer, even with a weak low emitting effect and / or coloring, particularly in reflection, mitigate.

Examples 1 to 3

The Examples 1 to 3 relate to a coating <figref>3</figref>, by a pyrolysis from the liquid phase was applied. It can be moved continuously by a suitable distribution nozzle, the cross and the float glass ribbon is at the output of the actual float enclosure is used. Here was worked intermittently by a movable nozzle was used, the opposite the substrate <figref>1</figref> was arranged, the already mentioned on the Dimensions was cut, wherein the substrate is first in a furnace was heated to a temperature of 400 to 650 ° C before it with a constant velocity past the nozzle ran, the appropriate solution aufsprühte.

example 1

In this example, there is no optional layer <figref>2</figref>, The coating <figref>3</figref> was applied by means of a solution containing two organometallic titanium precursors, Titandiisopropoxydiacetylacetonat and Titantetraoctylenglykolat, dissolved in a mixture of two solvents, Ethyl acetate and isopropanol contained.

there it should be noted that other precursor of the same type also Same usable, in particular other titanium chelates from Type titanium acetylacetonate, and Titanmethylacetacetat Titanethylacetacetat, Titanium triethanolamine or Titandiethanolamin.

After this the substrate 1 in the furnace the desired had reached temperature, ie in particular approximately 500 ° C, it was at the nozzle over, with the above-mentioned mixture of compressed air Ambient temperature aufsprühte.

&lt;?page 9?&gt;

It A TiO₂Layer having a thickness obtained of about 90 nm by the throughput speed the substrate <figref>1</figref> upstream of the nozzle and / or the substrate temperature can be controlled. The film was partly in the form of anatase crystallized.

These Layer has an excellent mechanical strength. Your abrasion resistance is comparable with that obtained from the uncoated glass surface becomes.

they let yourself turn and bias. She has a veil on: The scattered Light transmittance of the coated substrate is less than 0.6% (measured at standard illuminant D65 at 560 nm).

example 2

example 1 was repeated, wherein between the substrate <figref>1</figref> and the coating <figref>3</figref> a layer <figref>2</figref> of SnO₂: F inserted with a thickness of 73 nm has been. This layer was formed by powder pyrolysis from dibutyltin, DBTF obtained. You can also in a known manner by Flüssigphasenpyrolyse or vapor deposition can be obtained as, for example, is described in Patent Application EP-A-0648196. In vapor deposition may, in particular a mixture of monobutyltin trichloride and a fluorinated precursor, optionally together with a "soft" oxidizing agent of type H₂O used will.

Of the Refractive index of the obtained film was about 1.9. Your sheet resistance was about 50 ohms.

In Example 1 had the coated substrate <figref>1</figref>Which in a double glazing so had been installed so that the coating on position <figref>1</figref> was (With another substrate <figref>1'</figref>, The uncoated, but of the same Personality and the same dimensions as substrate <figref>1</figref> was with an air filling having a thickness of 12 mm), with a reflection excitation purity of 26% and a transmission excitation purity of 6.8%.

In Example 2 was the excitation purity in reflection (golden Sounds) only still 3.6% in transmission only 1.1%.

So allows it SnO the₂: F sublayer due to their electrical conductivity, to impart antistatic properties to the substrate; she also has a beneficial influence on the staining of the substrate by it its coloration makes both in transmission and in reflection significantly "neutral", a coloration that of the coating <figref>3</figref> of titanium oxide, the relative a high refractive index, is caused. You can by is provided with a suitable electrical connector, polarized be to the deposition of dust particles with the relatively considerable Size of about limit 1 mm.

In addition, of this underlayer, diffusion of the alkali metal ions in the photocatalytic TiO₂Layer decreases. Thereby, the photocatalytic activity is increased.

example 3

example 2 was repeated, but this time between the substrate <figref>1</figref> and the coating <figref>3</figref> a layer <figref>2</figref> on the base of silicon oxycarbide having a refractive index of about 1.75 and a thickness of about 50 nm has been inserted, a layer by CVD from a mixture of SiH₄ and Ethylene diluted, can be nitrogen, obtained as described in patent application EP-AO 518 755 describes. This layer is particularly effective, to the diffusion of alkali ions (Na⁺, K⁺) And alkaline earth metal ions (Ca⁺⁺) from the substrate <figref>1</figref> come in the coating <figref>3</figref> to prevent, therefore, the photocatalytic activity is markedly increased. Because they, like SnO₂: F, a refractive index between that of the substrate (1.52) and that of the coating <figref>3</figref> (about 2.30 to 2.35 has), it allows also, the strength of coloring of the substrate, both in reflection and in transmission, and globally the light reflectance R_L the substrate to lower.

The Examples 4 to 7 relate to coatings by CVD.

&lt;?page 10?&gt;

Examples 4 to 7

example 4

This Example relates to the application of the coating <figref>3</figref> by CVD directly on the substrate <figref>1</figref> using a standard nozzle, such as it in the above mentioned patent application EP-A-0518755 is described. As a precursor was either an organometallic or metal halide used. Here was as organometallic compound of titanium tetraisopropoxide decided that because of its great volatility and its large temperature range of use 300-650 ° C interesting is. The coating was performed in this example is about 425 ° C, the thickness of the TiO₂ was 15 nm.

The Tetraethoxytitanium, Ti (O-Et)₄, Can also suitable, and as a halide is TiCl₄ to call.

example 5

It The procedure described in Example 4, except that here the TiO₂Layer not directly with a thickness of 15 nm on the glass but on a sub-layer of SiOC having a thickness of 50 nm, which was applied as in Example 3, deposited has been.

example 6

It The procedure described in Example 4, except that here the thickness of the TiO₂Layer 65 nm, respectively.

example 7

It The procedure was as in Example 5 except that here the thickness of the TiO₂Layer 60 nm, respectively.

For this Examples 4 to 7 it should be noted that the so-coated substrates good mechanical strength in abrasion tests possessed. Especially was no detachment the TiO₂Layer observed.

example 8

In this example, a sol-gel process has been applied, the Deposition by dip coating, which is also known as "dip coating", accomplished was, the principle of <figref idrefs="S33">2</figref> apparent: It is it is a question, the substrate <figref>1</figref> in the solution <figref>4</figref>That the / the corresponding precursor for the coating <figref>3</figref> contains, immerse and then the substrate <figref>1</figref> at a controlled rate by a driven means <figref>5</figref> again pull with the choice of the rate of withdrawal allows the thickness the solution remaining on both sides of the substrate, and therefore, the thickness the coatings applied after the heat treatment to simultaneously the solvent vaporize and / precursors to decompose to an oxide to adjust.

To the Applying the coating <figref>3</figref> A solution <figref>4</figref> used either titanium tetrabutoxide Ti (O-Bu)₄. stabilized with diethanolamine DEA in a molar ratio of 1: 1 in a solvent the type of ethanol with 0.2 mol tetrabutoxide per liter of ethanol, or the mixture of precursors and solvents, the has been described in Example 1, contained. (It can also other precursors be used as Titandibutoxydiethanolamin.) Substrates <figref>1</figref> can SiOC sublayers include.

After Pulled out of the respective solution <figref>4</figref> were the substrates <figref>1</figref> for one hour at 100 ° C and then about 3 hours at 550 ° C heated with a progressive rise in temperature.

It was applied to each side of a coating <figref>3</figref> obtained in both cases of TiO₂Which probably crystallized in the anatase form was.

example 9

In this example, the "Cell-coating method" is applied, the principle in <figref idrefs="S33">3</figref> is sketched. It is it is a question of forming a narrow cavity in two Substantially parallel sides <figref>6</figref>. <figref>7</figref> and two seals <figref>8th</figref>. <figref>9</figref> limited is, wherein at least one of the sides <figref>6</figref>. <figref>7</figref> out the treated side of the substrate <figref>1</figref> consists. After that is the cavity with the solution <figref>4</figref> out Precursor / n for the &lt;?page 11?&gt;coating filled and the solution <figref>4</figref> for example by means of a peristaltic pump <figref>10</figref> such controls removed that forms a wetting meniscus, wherein according to the distance of the solution, a film of the solution <figref>4</figref> on the side of substrate <figref>1</figref> remains.

Of the cavity <figref>5</figref> then at least the period maintained for that for a drying is required. The curing of the layer is carried out by a heat treatment. The advantage of this method over the "dip-coating" is particularly in that only one side of the substrate <figref>1</figref> and not systematically both sides can be treated without a masking system fall back to have to.

The substrates <figref>1</figref> thin include layers <figref>2</figref> based on silicon oxycarbide, SiOC.

In Example 6, the solutions described in Example 8 were each <figref>4</figref> used. There were then same heat treatments conducted to the coating <figref>3</figref> of TiO₂ to receive.

coating <figref>3</figref> pointed good mechanical resistance on.

in the Scanning Electron Microscope (SEM) showed a field effect in the form of "grains" of monocrystals with a diameter of about 30 nm. The roughness of this coating yielded wetting properties, the rough better than not a Coating were.

the same solutions <figref>4</figref> can also be used to coatings by "spray coating", as in <figref idrefs="S34">4</figref> shown, the solution <figref>4</figref> in A mist form to the static substrate <figref>1</figref> is sprayed, or by roller application, as in <figref idrefs="S34">5</figref> shown, apply. In the latter case, the substrate is<figref>1</figref>, the from a negative pressure to a support <figref>11</figref> out stainless steel, and Teflon a container <figref>12</figref> kept is the solution contains, in which a slot cylinders <figref>14</figref> partially immersed, through left and then A container <figref>12</figref> and cylinder <figref>14</figref> about the entire length of the substrate <figref>1</figref> moves, the mask <figref>13</figref> on rapid evaporation of the solvent from the solution <figref>4</figref> prevented. Because closer For details on this method can be advantageously teach in the above-mentioned patent application WO-94 / 01598th

It Experiments were in accordance with the previous examples obtained substrates performed, to characterize the applied coatings and their evaluate fog-repellent and dirt-repellent properties. <ul><li>- test 1: This is the test pattern of the fitting. It consists in the Consequences of the photocatalysis and of the structure of the coating (Hydroxylgruppenanteil, porosity and roughness) to observe the wetting. If the surface photoreactively is that carbonaceous micro pollution that might be depositing on the coating, continually destroyed and the surface is hydrophilic and therefore fog-repellent. It can also be a quantitative Review conducted be by the first strongly heated coated substrate in the cold is stored or simply blown out is being measured, whether misting, and if so, at what time, which the period is measured is the for the disappearance of the fitting is required.</li><li>- test 2: Here is the review of hydrophilic and oleophilic on the surface the coating layer 3 in comparison with those of the surface of a uncoated glass by measuring the contact angle of a water drop and a drop of DOP (dioctyl phthalate) on the surface after the substrates for one week under ambient atmosphere in natural Lighting, in the dark and then for 20 minutes at a UVA radiation were left.</li><li>- test 3: He is on the to evaluative substrate an organosilane apply and with UVA irradiating such that it by photocatalysis is degraded. As the organosilane changes the wetting properties, shows the measurement of the contact angle of the substrate with water during the Irradiating the degradation state of the applied layer. The rate of degradation this layer is provided with the photocatalytic activity of the substrate connected.</li></ul>

The grafted organosilane was a trichlorosilane: octadecyltrichlorosilane (OTS). The grafting was carried out by dipping.

The Test apparatus consisted of a carousel which are 1 to 6 UVA low-pressure lamps turned. To be assessed specimens were in the carousel that face to be evaluated side of the UVA radiation, arranged. ever received on their position and the number of lit lamps each specimen a UVA radiation of 0.5 to 50 W / m², Both Examples 1, 2, 3, 8 and 9 was the energy flux on &lt;?page 12?&gt;1.8 W / m² and in Examples 4-7 to 6 W / m² selected.

Of the Period between measurements of the contact angle was varied between 20 minutes and 3 hours, depending on the photocatalytic activity of the subject Specimen. The measurements were carried out using a goniometer.

After Irradiation showed the glasses an angle of about 100 °. It is believed that the layer is destroyed after irradiation, if the angle is less than 20 °.

Each tested specimens was the average rate of degradation of the layer in nanometers per hour, that is, the thickness of the applied organosilane divided by the irradiation time, which allows the end a Limit of less than 20 ° (degradation time To achieve the Organsosilanschicht), characterized.

All Examples passed the test 1, that is, after using on the the coating provided substrates had been blown completely transparent stayed while on the uncoated substrates a highly visible fog coating formed.

The Examples were subjected to Test 2: The coated substrates reported after irradiation with UVA has a contact angle with water and with DOP of not more than 5 °. In contrast, had an uncoated glass under the same Conditions a contact angle with water of 40 ° and a Contact angle with DOP of 20 °.

In The following table shows the results of in accordance with the preceding Examples coated substrates are summarized in test. 3

&lt;?page 13?&gt;

<img img-content="tb" img-format="tif" he="150" wi="163" file="00260001.tif" />

Of the Table shows that of an underlayer, in particular from SiOC, due to their barrier effect against alkali and alkaline earth metal ions, which can migrate from the glass (Comparison of Examples 4 and 5 or 6 and 7), the photocatalytic activity the TiO₂ containing coating is promoted.

furthermore it should be noted that the thickness of the TiO₂ containing Coating also plays a role (comparison of Examples 1 and 3); at a thickness of the TiO₂coating greater than the average size of single crystals or crystallites will get a better photocatalytic effect.

It it was observed that the TiO obtained by CVD₂coatings the most pronounced Crystallization with crystallite sizes of about 20 to 30 nm exhibited. It should be noted that the photocatalytic activity Example 6 (65 nm TiO₂) Is significantly higher than that of Example 4 (only 15 nm TiO₂) was. It is advantageous, therefore, a thickness of the TiO₂coating provided that at least two times greater than the average diameter the crystallites which it contains. Alternatively, as this Example 5 was the case, a small thickness of the TiO₂coating be maintained, but then a bottom layer with a suitable Typical and suitable thickness is used to the TiO₂-Kristallwachstum from the "first" crystallite layer best to promote.

It was noted that the TiO₂crystallization being to a lesser extent was in the coatings, as by another method CVD had been applied. Again, however, can a compromise conclude: A less pronounced Crystallization and an a priori less high photocatalytic activity can be "compensated" by applying a deposition the example less is expensive or less complex. Moreover, the use an appropriate sublayer or the doping of TiO₂ it allow, if necessary, the photocatalytic properties to verbes&lt;?page 14?&gt;fibers.

It is also apparent from the comparison of Examples 2 and 3 that the Typical of the underlayer the way of crystallization and thus affect the photocatalytic activity of the coating.