Photocatalytically activated self-cleaning object and process for producing thereof

Photocatalytically activated self-cleaning object and method of its preparation

Application links

This application claims the benefit of Provisional US Application Serial No. 60 / 040,566 filed March 14, 1997. Provisional US Application Serial No. 60 / 040,566 of March 14, 1997 and US Application No. 08 / 899,265 to Greeneberg et al. The name 'PASO devices', filed at the same time, also refers to the present application and is incorporated herein by reference. ..

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Technical field

The present invention relates to a method of applying a PASO coating to a substrate (e.g., a glass sheet or continuous float glass ribbon), a method of preventing sodium poisoning of a PASC coating applied to a substrate containing sodium ions, and products prepared in accordance with these methods.

BACKGROUND OF THE INVENTION

For many substrates (e.g., glass substrates), it is desirable that the surface of the substrate remain "clean", i.e., free of surface impurities, such as conventional organic and inorganic surface impurities. Traditionally, this means that such surfaces must be cleaned frequently. Typically, this cleaning operation is performed manually or by mechanical means

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equipment. Both of these methods are laborious, time consuming and / or expensive. Accordingly, there is a need to provide substrates having surfaces that are self-cleaning or at least easier to clean, thereby eliminating or reducing the need for manual or mechanical cleaning.

Titanium dioxide (TiO2) coatings are known to form a photocatalytically-activated self-cleaning (PASC) surface on a substrate. Publications aimed at forming a PASC titanium dioxide coating are US Patent No. 5,595,813 and "Photooxidative Self-Cleaning of a Transparent Titanium Dioxide Layer on Glass", Paz et al., J.Mater.Res., Vol.10, No.11, pages 2843-48 ( November 1995). Furthermore, a bibliography of patents and articles relating generally to photocatalytic oxidation of organic compounds is given in the Bibliography of Works on the Photocatalytic Removal of Hazardous Compounds from Water and Air, D.BIake, National Renewable Energy Laboratory (May 1994), supplemented with the latest information in October 1995 and in October 1996.

The currently available method of applying a PASC coating (e.g., a PASC titanium dioxide coating) to a substrate is the sol-gel method. In this method, the substrate is coated with a non-crystallized alcoholic solvent-based colloidal suspension by centrifugal casting, spraying or dipping at or near room temperature. Then, the substrate is heated to a temperature in the range of about 100 ° C to 800 ° C (212 ° F to 1472 ° F), which results in either bonding the PASC coating to the substrate and / or crystallizing the PASC coating to form a crystallized on the substrate. PASC coating (gel).

One limitation of the application of the sol-gel PASC coating is that the process is not economically or practically compatible with some application conditions or substrates. For example, if it is desired to form a PASC coating on a float glass web during its manufacture, the web may be too hot to receive the sol-gel, which is partially dependent on the solvent used. Many solvents used in the sol-gel process require cooling the hot float ribbon to about room temperature before applying the sol-gel and reheating to a temperature sufficient to crystallize the sol-gel in the PASC coating. Such cooling and reheating requires substantial investment in equipment, energy and handling costs and significantly reduces production efficiency.

The activity of PASC coatings can be significantly reduced or destroyed if sodium ions are present in the substrate and migrate from the substrate to the PASC coating. This process is known as sodium poisoning or sodium ion poisoning. For many substrates that contain sodium ions, the rate of migration of sodium ions into coatings increases as the temperature of the substrate increases. Thus, a further limitation of the sol gel coating process is that reheating the substrate will increase the opportunity for sodium ion migration and thus sodium poisoning of the PASC coating.

A further limitation of the sol-gel PASC coating is the thickness of the coatings having a thickness of, for example, several microns. Such thick PASC coatings may adversely affect the optical and / or aesthetic properties of the articles coated with the PASC coating.

It follows from the above that there is a need for a product having a PASC coating deposited thereon and a method for applying the PASC coating that does not exhibit the disadvantages of the prior art.

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SUMMARY OF THE INVENTION

The present invention relates to a PASC article comprising a substrate having at least one surface and a PASC coating, for example titanium dioxide, deposited on the substrate surface by a method selected from the group consisting of Chemical Vapor Deposition (CVD), spray pyrolysis and vacuum magnetron sputtered vacuum deposition (MSVD). Thus, the present invention relates to a method of forming such a product.

The present invention also relates to a PASC article comprising a substrate having at least one surface, a sodium ion diffusion barrier (SIDB) layer, such as a layer of tin oxide, titanium dioxide, alumina and mixtures thereof applied to a a substrate surface and a PASC coating, for example titanium dioxide, deposited over the SIDB layer. The PASC coating and SIDB layer are deposited by a process selected from the group consisting of CVD, spray pyrolysis and MSVD. Thus, the present invention relates to a method of making such an article.

BRIEF DESCRIPTION OF THE DRAWINGS

1 is a front elevational view of a substrate having a dispersed PASC coating.

Fig. 2 is a view similar to Fig. 1 showing the SIDB layer sandwiched between the substrate and the PASC coating.

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Fig. 3 is a schematic view of selected elements of the CVD coating machine.

Fig. 4 is a schematic view of selected elements of a spray pyrolysis coating machine.

DETAILED DESCRIPTION OF THE INVENTION

Fig. 1 is an object 20 having features of the present invention. The article 20 comprises a substrate 22 provided with a PASC coating 24. The substrate 22 is not limiting to the invention and may consist of a glass substrate, for example, a glass sheet or a continuous float glass ribbon, a plastic substrate, a metal substrate and an enamelled substrate.

The PASC coating 24 may be directly on the substrate 22 as shown in FIG. 1, or alternatively, additional layers may be interposed between this layer 24 and the substrate 22, including, but not limited to, the SIDB layer 26 as shown in FIG. described in more detail. Further, as those skilled in the art are aware, the PASC coating 24 may be the uppermost layer of the multilayer stack of coatings on the substrate 22, or the PASC coating may be one of the layers other than the uppermost layer within such a multilayer stack provided The PASC coating 24 may pass sufficient radiation to which the coating is sensitive to provide photocatalytic activation of the PASC coating 24 and provided that that the active radicals can pass through the coatings deposited on the PASC coating 24 to react with the organic impurities on the uppermost layer of the multilayer column.

The PASC coating 24 may be a coating that is photocatalytically activated for self-cleaning and which

4 4 · can be applied by CVD method, spray pyrolysis method or MSVD method. For example, but not limited to the invention, the PASC coating 24 may include one or more metal oxides such as titanium oxides, iron oxides, silver oxides, copper oxides, tungsten oxides, zinc oxides, zinc / tin oxides, strontium titanate or the like. mixtures thereof. The metal oxide may include metal oxides, peroxides or suboxides.

In a preferred embodiment, the PASC coating 24 is titanium dioxide. Titanium dioxide exists in amorphous form and in three crystalline forms, namely, anatase, rutile and brookite. Anatase titanium dioxide is preferred because it exhibits strong PASC activity and at the same time excellent resistance to chemical disruption and excellent physical durability. Furthermore, the titanium dioxide in the anatase phase has a high transmittance in the visible region of the spectrum, which makes it possible to form thin coatings of this titanium dioxide with excellent optical properties. The titanium dioxide rutile phase also exhibits PASC activity. Combinations of the anatase phase and / or the rutile phase with the brookite phase and / or the amorphous phase are acceptable for the present invention, provided that the combination exhibits PASC activity.

The PASC coating 24 must be strong enough to exhibit an acceptable level of PASC activity. There is no absolute value that indicates that the PASC coating 24 is "acceptable" or "unacceptable" since whether the PASC coating has an acceptable level of activity is determined by the purpose and conditions under which the PASC coated article is used and the property standards selected in connection with this purpose. In general, thicker PASC coatings allow higher PASC activity. However, further considerations may result in a thinner coating. For example, these thinner coatings are advantageous if the article is to have a high aesthetic or permeability

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9 99 optical reasons or if surface impurities on the surface of the article are simply removed with a thinner PASC coating, if the coating is exposed to significant irradiation and / or if the PASC coating 24 is exposed to sodium ion poisoning, as described in more detail below. For a wide range of applications, it is preferred that the PASC coating is at least about 200 angstroms (Å) thick, preferably at least about 400 Å, and most preferably at least about 500 Å. It has been found that when the substrate 22 is a piece of float glass and the PASC coating 24 is a PASC anatase titanium dioxide coating formed directly on this piece of float glass by the CVD method, then a thickness of at least about 500Å allows a PASC reaction rate ranging from about 2 x 10³ up to about 5 x 10 '³ per centimeter and minute ("cm")¹min '¹) to remove a stearic acid test layer when the PASC coating has been exposed to ultraviolet radiation from a light source such as a light source under the tradename UVA-340 of Q-Panel Company Cleveland, Ohio having an intensity of about 20 watts per square meter (W / m³) on the surface of the PASC coating, which is acceptable for a wide range of applications.

In accordance with the present invention, a thin PASC coating, for example less than 1 micron, more preferably less than 0.5 micron, is formed on the substrate 22 by the spray pyrolysis method, the CVD method or the MSVD method. In the spray pyrolysis method, the metal-containing precursor is carried in an aqueous suspension, in the CVD method in a carrier gas, such as nitrogen, and directed to the surface of substrate 22, the substrate 22 having a temperature sufficiently high to decompose the metal precursor to form a PASC 24 on substrate 22. In the MSVD method, a metal-containing target cathode is sputtered under negative pressure in an inert or oxygen atmosphere to deposit 99 9 99 99 9999

9999 The substrate 22 is heated during or after application of the substrate, causing crystallization of the dusted coating to form a PASC coating 24.

Each of the methods has advantages and limitations, for example, the CVD method and the pyrolysis method are preferable to the spray pyrolysis method, since an aqueous solution in the spray pyrolysis method may result in the presence of OH ions in the PASC coating 24. 24 thereby reducing the PASC activity of the coating. The CVD method and the pyrolysis method are also more preferred than the MSVD method because they allow the coating of continuous substrates at elevated temperatures, such as float glass strips. The CVD method, the spray pyrolysis method and the MSVD method of applying the PASC coating 24 will be discussed in more detail below. It will be appreciated that the spray pyrolysis method and the CVD method can be used to deposit thin (e.g., several hundred angstroms) metal oxide coatings (including titanium dioxide coatings) on a substrate. Such coatings are described in US Patent Nos. 4,344,986; 4,393,095;

4,400,412; 4,719,126; 4,853,257; and 4,971,843, which are incorporated herein by reference.

Metal-containing precursors that can be used in practice in the practice of the present invention to form PASC titanium dioxide coatings by the CVD method include, but are not limited to, titanium tetrachloride (TiCU), titanium isopropoxide (Ti (OC3H)₇(4) (hereinafter TTIP) and titanium ethoxide (Ti (OC2H₅)₄(TTEt). Carrier gases that may be used in the CVD method include, but are not limited to, air, nitrogen, oxygen, ammonia, and mixtures thereof. The preferred carrier gas is nitrogen and the preferred metal-containing precursor is TTIP. The concentration of the metal-containing precursor in the carrier gas is generally in the range from 0.1% to 0%. 4% by volume for the three listed metal-containing precursors, but it is clear to those skilled in the art that these concentrations may vary for other metal-containing precursors.

Metal-containing precursors that can be used in practice to form PASC coatings by the spray pyrolysis method include water-insoluble organometallic reactants, especially metal acetylacetone compounds, which are crushed or wet milled to a particle size of less than about 10 microns and suspended in an aqueous medium using a chemical wetting agent. A suitable metal acetylacetonate for forming the titanium dioxide PASC coating is acetylacetone titanium oxide (TiO 2 C 5 H 2 Cl 2). The relative concentration of metallic acetylacetone in the aqueous suspension is preferably in the range of about 5 to 40 weight percent of the aqueous suspension. The wetting agent may be any relatively low-foaming surfactant, including anionic, nonionic or cationic compounds, although nonionic surfactants are preferred. The wetting agent is typically added in an amount of about 0.24% by weight, but may be in the range of about 0.01% to 1% or more. The aqueous medium is preferably distilled or deionized water. Wetting agents for the pyrolytic deposition of metal-containing layers are described in U.S. Patent No. 4,719,127, in particular in column 2, line 16, through column 4, line 48.

For both the CVD method and spray pyrolysis, the temperature of the substrate 22 during formation of the PASC coating must be within a range that causes the decomposition of the metal-containing precursor to form a coating having PASC activity (e.g., crystalline phase for PASC metal oxide coatings). Obviously, the lower limit of this temperature range is

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0000 0 0 0000 • 00 · 0 0 000000 • 0 0 0 0 0 000 000 000 000 · 0 * · widely influenced by the decomposition temperature of the selected metal-containing precursor. For the above-mentioned titanium-containing precursors, the minimum temperature of the substrate 22, which ensures sufficient decomposition of the precursor, is within a temperature range of about 400 ° C to 500 ° C (752 ° F to 932 ° C). The upper limit of this temperature range may be affected by the coated substrate. For example, where the substrate 22 is a float glass web and a PASC coating 24 is applied to the web during its manufacture, the float glass may reach temperatures above 1000 ° C (1832 ° F). The float glass web is typically attenuated or formatted (for example, shrunk or compressed) at a temperature above 800 ° C (1472 ° F). If the PASC coating 24 is applied before or during the weakening of the float glass, the PASC coating 24 may rupture or warp as the float glass web is shrunk or compressed. Therefore, in the practice of the invention, it is advantageous to apply a PASC coating when the float glass web is dimensionally stable, for example below about 1472 ° F for soda-lime-silica glass and at a decomposition temperature of the metal-containing precursor, e.g. 752 ° F).

The formation of the PASC coating 24 by the CVD or spray pyrolysis method is particularly advantageous for implementation during the production of a float glass ribbon. Generally, a float glass web is produced by melting glass batch material into an oven and feeding refined molten glass to a molten tin bath. The molten glass is drawn through the tin bath as a continuous glass ribbon, being formatted and controlled to form a dimensionally stable float glass ribbon. This strip is then removed from the tin bath and is conveyed by conveyor rollers through a cooling furnace for annealing. The annealed strip of float glass is then guided through the conveyor rollers through the cutting stations where it is cut into glass • • • ··&gt; ··

9 · boards of required length and width. US Patent Nos. 4,466,562 and 4,671,155, which are incorporated herein by reference, include a description of the production of float glass.

The tin bath strip temperatures generally range from about 1093.3 ° C (2000 ° F) at the beginning of the bath to about 538 ° C (1000 ° F) at the outlet end of the bath. The strip temperature between the tin bath and the tunnel cooling furnace generally ranges from about 480 ° C (896 ° F) to about 580 ° C (1076 ° F); the temperature of the float belt in the tunnel cooling furnace is generally in the region of about 204 ° C (400 ° F) to 557 ° C (1035 ° F) peak.

US Patent Nos. 4,853,257; 4,971,843; 5,536,718;

Nos. 5,464,657 and 5,599,387, which are incorporated herein by reference, disclose CVD coating methods and apparatuses which can be used in the practice of the invention for coating a float glass web during its manufacture. By the CVD method, it is possible to coat a moving float glass web as it resists the harsh environment associated with the production of a float glass web and is thus suitable for forming a PASC coating 24 on this web. The CVD coating apparatus can be used at several points in the float glass web manufacturing process. For example, it can be used to pass a float glass ribbon through a tin bath, after leaving a tin bath, before, in or out of a tunnel cooling furnace.

As is known to those skilled in the art, the concentration of metal-containing precursor in the carrier gas, carrier gas flow rate, float belt speed ("line speed"), CVD coating surface area relative to float belt surface area, surface area and flow velocity exhaust gas exhaust device exhaust, exhaust speed ratio • «• · ♦♦ ·

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the exhaust vents to the carrier gas inlet velocity in the CVD coating unit, known as the 'suction adaptation ratio', and the float belt temperature are among parameters that affect the final thickness and morphology of the PASC coating 24 formed on the float CVD belt.

US Patent Nos. 4,719,126; 4,719,127; Nos. 4,111,120 and 3,660,061, incorporated herein by reference, disclose a spray pyrolysis method and apparatus that can be used in the manufacture of a float glass ribbon. The spray pyrolysis method is like the CVD method suitable for coating on a moving float glass web, but has a more complex apparatus than the CVD method typically used between the tin bath exit and the tunnel cooling furnace inlet.

One skilled in the art will appreciate that the components and concentrations of the pyrolytically sprayed aqueous suspension, the rate of passage of the float belt through the line, the number of pyrolytic spray guns, spray pressure or volume, spraying method and float belt temperatures at deposition time are among parameters that will affect the final thickness and morphology of the PASC coating 24 formed on the float web by spray pyrolysis.

As is known to those skilled in the art, the surface of a float glass ribbon on molten tin (commonly referred to as the "tin side") has tin dispersed in the surface, causing a different tin absorption pattern on the tin side than the opposite side that is not in contact with the molten tin. tin (commonly called the "air side"). This characteristic is described in: Chemical Characteristics of Float Glass Surfaces, Seiger, J., JOURNAL OF NON-CRYSTALLINE

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SOLIDS, Volume 19, pp. 213-220 (1975); Penetration of Tin in Bottom Surface of Float Glass; A Synthesis, Columbin L. A et al .; JOURNAL OF NON-CRYSTALLINE SOLIDS, Vol. 33 &amp; 39, pp. 551-556 (1980) and Tin Oxidation State, Depth Profiles of Sn²⁺ and Sn⁴⁺ and Oxygen Diffusivity in Float Glass by Mossbauer Spectroscopy, Wiliams, KFE et al., JOURNAL OF NON-CRYSTALLINE SOLIDS, vol. 211, pages 164-172 (1997), incorporated herein by reference. As is known to those skilled in the art, the PASC coating 24 may be formed on the air side of the float belt while it is carried by a tin bath (CVD method), on the air side of the float belt after leaving the tin bath by both CVD and spray pyrolysis. the tin side of the float belt after exiting the tin bath in the CVD method. When the PASC coating 24 is formed on the tin side of the float belt, it is expected that the tin and / or tin oxide present in the glass surface will function as the SIDB layer 26 for the PASC coating 24 located thereon.

US Patent Nos. 4,379,040; 4,861,669; 4,900,633;

4,920,006; 4,938,857; Nos. 5,328,768 and 5,492,750, incorporated herein by reference, disclose MSVD devices and methods for sputtering metal oxide coatings onto a substrate, including a glass substrate. The MSVD method is generally not compatible with the formation of a PASC coating on a float glass web during its manufacture, since, among other things, the MSVD method requires a vacuum during spraying that is difficult to build around a continuously moving float web. However, the MSVD method is acceptable to form a PASC coating 24 on a substrate 22, for example, on a glass plate. Those skilled in the art are aware that the substrate 22 can be heated to a temperature in the range of about 400 ° C (752 ° F) to 500 ° C (932 ° F), so that the coating is sprayed on to 449 4 9 4 44 44.

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944 The MSVD substrate crystallizes during the deposition process, thereby eliminating the subsequent heating operation.

Heating the substrate during sputtering is not a preferred method because an additional heating operation during sputtering may reduce production capacity. Alternatively, the sputtered coating can crystallize in an MSVD device directly and without further heating using high energy plasma, but again, due to the tendency to reduce the production capacity of the MSVD coating machine, this method is not preferred.

A preferred method for implementing a PASC coating using the MSVD method is to sputter the coating onto the substrate, remove the coated substrate from the MSVD coating machine, and then heat the coated substrate to crystallize the dusted coating to form a PASC coating 24. For example, but not limited to, the MSVD method sputters a titanium metal target in an argon-oxygen atmosphere having about 5-50%, preferably 20% oxygen, at a pressure of about 5-10 milliters (0.67 - 1.33 Pascal) and by sputtering, a titanium dioxide coating of desired thickness is formed on the substrate 22. The coating, as applied, is not crystallized. The coated substrate is removed from the coating machine and heated to a temperature in the range of about 400 ° C (752 ° F) to 600 ° C (1112 ° F) for a time sufficient to form the PASC crystalline form, thereby allowing the PASC activity of the coating. Generally, a time of at least one hour at a temperature in the range of about 400 ° C (752 ° F) to 600 ° C (1112 ° F) is preferred. If the substrate 22 is a glass plate cut from a float glass web, the PASC coating 24 may be dusted on the air and / or tin side.

Substrate 22 having a PASC coating 24 deposited by CVD method, spray pyrolysis or MSVD method may subsequently be subjected to one or more annealing operations,

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444 444 444 44 44 to increase the self-cleaning activity of the PASC coating 24. It is believed that such annealing after formation of the PASC coating can enhance the self-cleaning activity of the PASC coating 24 by promoting formation of the desired PASC crystalline phase. The annealing time and temperature can be influenced by several factors including the composition of the substrate 22. the composition of the PASC coating 24, the thickness of the PASC coating 24 and whether the PASC coating 24 is directly on the substrate 22 or is one of multiple layers on that substrate 22. It has been determined that if the substrate 22 is float glass and the PASC coating is 400A or 625A anatase titanium dioxide produced by spray pyrolysis, annealing the coating at 500 ° C (932 ° F) for up to 13 minutes increases PASC activity .

As discussed above, when the PASC coating is formed by CVD, spray pyrolysis, or MSVD, the substrate 22 comprises sodium ions that can migrate from the substrate 22 to the PASC coating deposited on the substrate 22. sodium ions can block or destroy photocatalytic activity PASC coatings by forming inactive components while consuming titanium, for example by forming sodium titanates or by causing recombination of photoelectrically excited charges.

It has been found that a PASC coating can be formed on a substrate containing sodium ions without loss of photocatalytic activity as follows:

1. By allowing limited sodium ion poisoning, parts of the PASC coating and / or

2. forming the SIDB layer 26.

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Each of these methods will be discussed in detail below.

It has been found that if the thickness of the PASC coating exceeds the minimum threshold, PASC activity will not be destroyed by sodium ion migration even when the PASC coating is deposited on the surface of the sodium ion-containing substrate and the substrate is at a temperature sufficient to cause sodium ion migration from the substrate to the PASC . Although the mechanism that causes this is not entirely clear, it can be assumed that if the PASC coating thickness exceeds the minimum thickness, sodium ions are able to migrate only a fraction of the total PASC coating thickness during the time the substrate temperature exceeds the temperature allowing sodium ion migration. Then, when the temperature of the substrate drops below the temperature causing sodium ion migration, the migration is stopped or "frozen" in place, resulting in the surface of the PASC coating opposite from the substrate surface being unaffected by sodium ion poisoning and capable of maintaining PASC activity. This minimum PASC coating thickness varies with expected parameters such as: the time the substrate is maintained above the temperature at which sodium ion migration occurs, the use for which the PASC article is intended, and the degree of desired or desired PASC activity. It has been found that for a PASC titanium dioxide coating applied by CVD to flat soda lime silicate glass, the thickness of the PASC coating should be at least about 250Å, preferably at least about 400Å, and more preferably at least about 500Å, so that a sufficient portion of PASC she kept her activity.

According to FIG. 2, in an alternative method of protecting the PASC coating from sodium ion poisoning, it is formed between the PASCs

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999 The SIDB layer 26 may be the only layer between the PASC coating 24 and the substrate 22, or it may be a single layer of a multi-layer column. Using a multilayer column, the SIDB layer 26 is not required to contact the substrate 22, provided the SIDB layer 26 is positioned between the PASC coating 24 and the substrate 22 to prevent sodium ions from migrating from the substrate 22 into the PASC coating 24.

The SIDB layer may be formed from amorphous or crystalline metal oxides including, but not limited to, cobalt, chromium or iron oxides, tin, silicon, titanium, zirconium, fluorine-doped tin oxides, aluminum, magnesium, zinc oxides and mixtures thereof. Mixtures include, but are not limited to, magnesium / aluminum and zinc / tin oxides. Those skilled in the art will appreciate that the metal oxide may include metal oxides, peroxides, or suboxides. Although the thickness of the SIDB layer required to protect the PASC coating from sodium ion poisoning varies with many factors including the time the substrate is maintained at a temperature above which sodium ion migration occurs, the rate of sodium ion migration from the substrate, the sodium ion migration rate of the SIDB layer, thickness. The PASC coating and the degree of photocatalytic activity required for a given application, for most applications, the SIDB layer thickness should typically be in the range of at least about 100Å, preferably at least about 250Å, and most preferably at least 500Å, to prevent sodium ion poisoning of the PASC coating. The SIDB layer may be applied to the substrate 22 by the CVD method, spray pyrolysis, or MSVD method. If a spray pyrolysis method or a CVD method is used, to form the SIDB layer, preferably the substrate 22 is maintained at a temperature of at least about 400 ° C (752 ° F) to ensure decomposition of the metal-containing precursor. The SIDB layer may be formed by others

0000 0 0 ·♦ 1« • ·0 00 0 0 0 0 • ·· · · «000 » * 0 0 0 000 000 • · · 0 0

000 0 · 0 000 00 00 processes, including the sol-gel method, which, as mentioned above, is not compatible with the production of float glass ribbon.

The SIDB tin oxide layer can be applied to the substrate by spray pyrolysis to form an aqueous suspension of difluordibutyltin (C).₄H₉)₂SnF2 and water, and this aqueous suspension is applied to the substrate by spray pyrolysis. Generally, the aqueous suspension typically contains 100 to 400 grams of difluordibutyltin per liter of water. Wetting agents may be used to improve the suspension. During the preparation of the aqueous suspension, the difluordibutyltin particles may be milled to an average particle size of from 1 to 10 microns. The aqueous suspension is preferably intensively mixed to distribute the particles in the suspension evenly. The aqueous suspension is spray-pyrolyzed to a substrate surface having a temperature of at least about 400 ° C (752 ° F), preferably about 500 ° C to 700 ° C (932-1929 ° F), wherein the aqueous suspension pyrolyses for the purpose of forming a SIDB tin oxide layer. The thickness of the SIDB layer formed by this process can be controlled, inter alia, by the coating line speed, the concentration of difluordibutyltin in the aqueous suspension, and the spraying rate.

Alternatively, the SIDB tin oxide layer may be formed on a CVD substrate by a metal precursor method such as monobutyltin trichloride vapor (MBTTCL) in an air carrier gas mixed with water vapor. The MBTTCL vapor may be present at a concentration of at least about 0.5% in the air carrier gas supplied to the substrate while the substrate is at a temperature sufficient to cause deposition of a tin-containing layer, for example at at least 400 ° C (952 ° F). preferably about 500 ° C to 800 ° C (932-1472 ° F) to form

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SIDB layers of tin oxide. Advantageously, the thickness of the SIDB layer formed in this manner can be controlled, inter alia, by the coating line speed, the MBTTCL vapor concentration in the air carrier gas, and the carrier gas flow rate.

The SIDB layer formed by the MSVD method is described in U.S. Patent Application Serial No. 08 / 597,543, filed Feb. 1, 1996 under the title "Alkali Metal Diffusion Barrier Layer" referred to herein, which application discloses forming barriers by diffusion of the alkali metal. The barrier layer described is generally effective at thicknesses of about 20Å to 180Å, with efficiency increasing with increasing density of the barrier.

The PASO coatings of the present invention are usually photocatalytically activated for self-purification by exposure to radiation in the ultraviolet region of the electromagnetic spectrum, for example 300-400 nanometers (hereinafter referred to as nm). Ultraviolet radiation sources include natural sources such as sunlight and artificial sources such as black light source or ultraviolet light such as UVA-340 light source. When artificial ultraviolet light sources are used under test conditions where it is desirable to determine how the PASC coating will react to natural ultraviolet radiation, the UVA-340 has a light energy distribution that is closer to sunlight than the light energy distribution of the black light source, using a UVA-340 light source to further approximate how the PASC coating will behave when exposed to sunlight.

The intensity of the ultraviolet radiation is calibrated to a minimum intensity of 20 W / m.² on the surface coated with the test coating. The intensity can be calibrated, for example, by an ultraviolet meter such as sold under the trademark BLACK-RAY by Ultraviolet Products, Inc., San Gabriel, CA, model J-221. The light source is preferably positioned perpendicular to the coated surface to be tested.

The ultraviolet radiation source and the PASC coating may be positioned relative to each other such that the ultraviolet radiation passes first through the PASC coating and then through the substrate (ie, front or coated side). If the substrate transmits ultraviolet radiation, the PASC coating and the ultraviolet radiation source may be positioned relative to each other such that the ultraviolet radiation passes first through the substrate and then through the PASC coating (ie, from behind or from the substrate side). In yet another embodiment, one or more ultraviolet radiation sources may be located on each side of the substrate having a PASC coating on one or both surfaces.

It is difficult to specify the preferred ultraviolet light source or ultraviolet light intensity or relative location of the ultraviolet light source, the PASC coating and the substrate, since many factors are possible. These factors include, but are not limited to: the purpose for which the PASC coating is used, e.g., outdoor or indoor use, a selected ultraviolet radiation source, i. natural or artificial, seasonal or geographical effects if the ultraviolet radiation source is natural, the desired or expected exposure time, the angle of incidence of ultraviolet radiation on the surface of the PASC coating, the expected or desired degree of PASC activity, the degree to which ultraviolet radiation can be reflected or absorbed by substrate and / or • 9999 9 9 99 «9 ♦ 9 9» 9 ·· 9 · · ·

999· 9 9 9999

99 9 99 99····

9 · Other coatings or layers placed above the substrate or over the PASC coating, impurities to be removed, PASC coating thickness, PASO coating composition, sodium ion poisoning potential and presence or absence of SIDB layer. However, it has been found that the intensity of ultraviolet radiation in the region of about 5 to 100 W / m²preferably at least 20 W / m², measured on the surface of the PASC coating from a source of ultraviolet radiation located above the surface of the PASC coating will produce sufficient intensity to cause satisfactory PASC activity for many self-cleaning applications.

It is useful to be able to measure and compare the PASC activity or activity of the PASC coatings in order to evaluate the PASC activity of the PASC coating. A known, readily available organic impurity can be applied to the PASC coating, and after photocatalytic activation of the PASC coating, the ability of the PASC coating to remove the organic impurity can be observed and measured. Stearic acid, CH₃(CH₂i3COOH is a model organic impurity for testing the PASC activity of PASC coatings, since this acid is a long hydrocarbon chain carboxylic acid and therefore a good “model molecule” for common impurity molecules such as household oils and dirt. Stearic acid can be applied to the PASC coating as a thin test layer using any conventional technology including dip coating, spraying, centrifugal coating. In general, stearic acid test layers having a thickness of about 100Å to 200Å provide an adequate test layer. Stearic acid can be used as stearic acid in methanol solution and it has been found that a solution having a concentration of about 6x10 &amp; apos;³ mole of stearic acid per liter of solution is sufficient.

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The activity of the PASC coating can be qualitatively estimated by overlaying the PASC coating with a stearic acid layer (which generally appears as a light brown layer upon application to the PASC coating), exposing the stearic acid layer to ultraviolet radiation of the desired intensity for a desired period of time. whether either the stearic acid test layer has completely disappeared or whether the darkness of the stearic acid layer has decreased compared to that portion of the stearic acid layer that has been applied to the PASC coating but has not been exposed to ultraviolet radiation.

PASC activity of PASC coatings can also be measured quantitatively by measuring the integrated intensity of the absorption bands of valence vibrations of carbon-hydrogen bonds (hereinafter CH bonds) of stearic acid present on the PASC coating. The integrated intensity is commensurate with the thickness of the stearic acid layer remaining on the surface of the PASC coating, and removal of the stearic acid layer by photocatalytically activated self-cleaning is expected to result in a decrease in the intensity of the absorption bands of the valence vibration CH bond. CH bonds in stearic acid absorb infrared radiation which, unlike ultraviolet radiation, does not photocatalytically activate the PASC coating. This absorption generally occurs between 2800 and 3000 cm -1¹ and may be measured by a Fourier transform infrared spectrophotometer, hereinafter FTIR spectrophotometer. The spectrophotometer may be equipped with a detector such as a deuterated triglyceride sulfate detector, hereinafter referred to as a DTGS detector, or a copper-cadmium-telluride detector, hereinafter referred to as an MCT detector. An MCT detector is preferred because it has a much higher signal / noise ratio than a DTGS detector. This may be important where the substrate and / or other coatings added to the PASC coating absorb infrared radiation that is

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used by a spectrophotometer to generate the absorption spectrum. When the infrared radiation is absorbed by the substrate and / or other coatings, the intensity of the infrared radiation beam passing through the stearic acid layer, the PASC coating and the substrate to the detector is significantly reduced. In combination with a low concentration of stearic acid on the surface of the PASC coating (which creates a very poor infrared absorption property) this means that the resulting infrared signal is not particularly intense. Therefore, a device equipped with an MCT detector produces a spectrum in which the signal / noise ratio is about one order of magnitude higher than a device equipped with a DTGS detector. When the PASC activity of a test layer of stearic acid deposited on the layers and substrates through which the infrared ray can pass is measured, the infrared ray can be directed through the layers and substrate to a detector located on the opposite side of the sample being tested. When the layers and substrates do not allow infrared radiation to pass, the infrared radiation beam can be directed to the surface at an angle as it passes through the stearic acid test layer and is reflected from the substrate, as opposed to passing through the substrate to the detector. This latter method is known as reflex infrared spectroscopy.

The rate of PASC reaction can be determined for a PASC coating by measuring the rate at which the coating reacts when removing a stearic acid layer from the coating when the PASC coating is exposed to radiation to which it is sensitive. Specifically, the rate of PASC response is expressed by the degree of reduction of the integrated intensity of the C - H valence vibrations (proportional to the surface area of ​​the coating) with the accumulated exposure time to which the coating is susceptible (hereinafter ultraviolet radiation). For example, it is FTIR

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The initial PASC activity for the stearic acid test layer on the PASC coating was measured by spectrophotometer. The PASC coating may or may not be exposed to ultraviolet radiation for this initial measurement. The stearic acid covering the PASC coating is then exposed to ultraviolet radiation for a measured period of time, at the end of which a second measurement of PASC activity is performed using an FTIR spectrophotometer. The integrated intensities of the CH valence vibrations in the second measurement are expected to be lower than in the first measurement due to this_TO that part of the stearic acid test layer has been removed by exposure to ultraviolet radiation. From these two measurements, it is possible to plot a curve of the integrated intensity of CH valence vibrations versus time, the slope of which determines the rate of PASC reaction. Although two points are sufficient to determine the curve, it is preferable to perform several measurements during PASC measurement to obtain a more accurate curve. While the exposure time to ultraviolet radiation between FTIR spectrophotometer measurements may be constant or may vary when more than two measurements of PASC activity are accumulated (because cumulative ultraviolet exposure time is used for plotting), intensity and orientation (coating or substrate side) of ultraviolet radiation should be constant for all measurements in determining the rate of PASC response.

The rate of PASC reaction can be reported in cm -1.¹min '¹wherein a higher value indicates greater PASC activity. There is no absolute speed indicating that the PASC coating is "acceptable" or "unacceptable" because whether the PASC coating has an acceptable level of activity is largely determined by the purpose for which the PASC coated article is used and the performance standards chosen for that purpose. . For most applications, at least about 2 x 10 'PASC activity is desirable³more preferably at least about 5 x 10 '³ cm¹min '¹.

• ·

It is also useful to measure the thickness of the PASC coatings for the purpose of appropriately determining and comparing the PASC activity of the PASC coatings prepared according to the present invention, since the thickness of the PASC coating may affect photocatalytic activity, as will be further demonstrated in the examples. The thickness of the PASC coating 24 and / or SIDB layer 26, if any, may be determined either by Variable Angle Spectroscopic Ellipsometry (YOUR) or by profilometric measurements of the scratched edge in the measured layer, or may be estimated from interference colors, as is known in the art.

The particle size of the PASC coating 24 and / or the SIDB layer 26, if any, can be calculated from X-ray diffraction (XRD) data using the Scherrer relationship. This relationship is known in the art and a discussion of it can be found in Chapter 9 of X-Ray Diffraction Procedures for Polycrystalline and Amorphous Materials, Klug and Alexander, John Wiley &amp; amp; (1954).

The following examples of the present invention are given by way of illustration, but the invention is not limited thereto.

Example 1

PASC coating of 2100Å thickness, produced by CVD method

The PASC activity of the titanium dioxide coating having a thickness of about 2100Å was investigated as follows. The PASC coating was applied using the CVD method »· · 9» 9 9 9

999 999 »9 · to the substrate 22 which was the air side of a piece of soda-lime float glass sold under the Solex® trademark by PPG Industries, Inc., Pittsburgh, Pennsylvania. This piece of Solex® glass was roughly 5.5 inches wide, 12 inches long and 0.016 inches thick (14cm x 30.5cm x 0.4cm) and was coated with a PASC titanium dioxide coating using the CVD glassware coater 88 as shown in FIG. 3. This CVD coating machine 88 generally consists of three zones shown in FIG. 3 separated by vertical dashed lines 90 and 92. These three zones include a preheating zone 94, a coating zone 96 and a cooling zone 98. A piece of Solex® glass, referred to herein as a substrate 22 has moved these three zones on the endless conveyor 102 in the direction of arrow 104.

Substrate 22 was fed to preheating zone 94 and was preheated to a temperature of about 649 ° C (about 1200 ° F) by a plurality of heaters 106 positioned above and below conveyor 102. Subsequently, substrate 22 was conveyed by conveyor 102 to CVD coating zone 96. This CVD coating zone 96 preferably comprises at least one coating unit 97. In order to sequentially apply more than one coating, the coating zone 96 may comprise a plurality of coating units 97. The coating unit 97 includes support subsystems and control elements such as a gas supply subsystem, a liquid supply subsystem, a temperature control subsystem, a suction control subsystem and a temperature and pressure monitoring subsystems, none of which are shown in the figure. The gas delivery subsystem controls the flow of the carrier gas to the surface of the substrate 22. Nitrogen was used as the carrier gas. The feed stream of nitrogen was maintained at heaters not plotted at a temperature of about 113 ° C (about 235 ° F). NH₃ the carrier gas contained 20% of the total flow. The suction flow rate was 125% of the inlet flow rate. Precursor containing metal • · ·· 9 9 9 ·

9 9 9 9 9 used for the deposition of the titanium dioxide PASC coating 22 was TTIP, which constituted 0.4% by volume of total flow and was also fed at a temperature of about 113 ° C (about 235 ° F). Total flow N₂, NH₃ and the TTIP vapor CVD coating machine 88 was 75 standard liters per minute (slm). The conveying speed of the conveyor 102 was about 50 inches (127 cm) per minute and the coating unit groove width was about 3/16 inches (0.48 cm). Substrate 22 was maintained in the coating unit 97 at a temperature of about 554 ° C (1030 ° F), and a coating 24 was applied to the substrate 22 to form a coated sample 100. A PASC coating 24 of approximately 2100Å thickness (as measured by YOUR) was formed on a 100 bvl sample.

The coated sample 100 then advanced to the cooling zones 98 where it was annealed from an initial temperature of about 549 ° C (1020 ° F) to a final temperature of about 121 ° C (250 ° F) for about 26 minutes.

The PASC coated sample 100 was subjected to XRD analysis. The particle size of the PASC coating 24 was determined to be about 309Å, as calculated using the Scherrer relationship. The coated sample 100 showed sharp peaks in the XRD pattern corresponding to titanium dioxide in the form of anatase.

Then, the PASC coated sample 100 was overlaid with a stearic acid test layer to measure its photocatalytic activity. Stearic acid / methanol solution around 6 χ 10 '³ mole of stearic acid per liter of solution was applied by pipetting this solution at a rate of about 2 ml / 10 sec to the center of the sample 100, with a coated sample of 100 bvl centrifuged at about 1000 rpm, resulting in stearic acid spilling for «0

00 · 0 0000 • 0 0 0 0 000 000 • 0 0 0 0

000 A layer of stearic acid of substantially uniform thickness, having a thickness in the range of about 100 to 200 Å, has been formed on the surface of the coated sample 100 by centrifugal force. The term "substantially" is used previously because the thickness of the stearic acid layer was not constant over the entire length of the coated sample 100, but was thicker due to the centrifugal force at the ends of the sample 100 and thinner at the center of the sample 100. It will be appreciated that the concentrations of the stearic acid solution described, the rotational speed, the sample size and the pipetting speed can be modified to obtain stearic acid coatings of the desired thickness. According to the parameters described above, the average thickness of the stearic acid test layer was about 150Å, as determined by calibrating the intensity of the infrared radiation with a silicon crystal microbalance.

Sample 100 coated with PASC titanium dioxide coating and stearic acid test layer was irradiated from the coated side of sample 100 with ultraviolet radiation from a normal black light source of 20W / m² on the surface of the PASC coating 24 for a total of about 30 minutes to induce photocatalytically activated self-cleaning of the stearic acid test layer. For quantitative measurement of photocatalytic activity, periodic FTIR spectrophotometer measurements were performed over an accumulated period of 30 minutes exposure to ultraviolet light using a FTIR spectrophotometer equipped with an MCT detector. Specifically, the stearic acid test layer on the PASC coated sample 100 was exposed to ultraviolet radiation for a measured period of time, over which the coated sample 100 was placed in an FTIR spectrophotometer, where the integrated area under the CH absorbance band of stearic acid was measured to determine PASC activity. Thereafter, the coated sample 100 was again · 4 · 4 · 4 · 4 · 4 · 4 · 4 · 4 · 4 · 4 · 4 · 4 · 4

4 · 4 · exposed to ultraviolet radiation for another measured period of time to further remove stearic acid, and then another FTIR measurement was performed. This procedure was repeated to obtain an absorption intensity diagram of the integrated infrared radiation CH of valence vibrations as a function of the cumulative exposure time to ultraviolet radiation, the slope of which gives the PASC velocity for the PASC coated sample 100 and the stearic acid test layer. It will be appreciated that all FTIR measurements were performed in roughly the same region of the sample 100 to minimize the effect of varying the thickness of the stearic acid test layer as described above. The photocatalytic reaction rate was determined to be 3.53 χ 10 '³ cm '¹min '¹which is close to that of PASC coated substrates that contain little or no sodium ions (e.g., silica glass substrates). This indicates that the 2100A thickness of the titanium dioxide coating was sufficient to overcome sodium ion poisoning.

Example 2

PASC coating 700 - 800A thick produced by CVD method

A PASC coating 24 of about 700-800Å thickness was applied to the glass substrate by the CVD method in the same manner as in Example 1, with the following exceptions.

The glass used in Example 2 was 3 mm (0.12 inches) thick, clean (i.e., low iron soda-lime silica) glass. The preheat temperature in Example 2 was 593 ° C (1000 ° F), the TTIP concentration in Example 2 was 0.1% at a total of 4 4 4 44 44 ··· • * · 4 4 4 50slm flow. NH 3 was contained in the carrier gas at 24% of the total flow. The feed rate was 30 inches per minute (76.2 cm per minute). The groove width is 1/16 inch (0.16 cm). The thickness of the PASC coating 24 of titanium dioxide was estimated from interference colors in a manner known in the field of thin film thickness measurement and was determined to be in the region of about 700-800 Å.

The stearic acid test layer was applied to the PASC titanium dioxide coating in the same manner as described in Example 1 and then exposed to ultraviolet radiation as described in this example with periodic measurements of the activity of photocatalytically activated self-cleaning by FTIR spectrophotometer for a cumulative period of 33 hours. The photocatalytic reaction rate was determined to be 0.17 χ 10 '³ cm '¹min '¹.

It is believed that the reduced PASC activity of the example results from the difference in the titanium dioxide coating thickness between Examples 1 and 2 (2100Å versus about 700800Å). In particular, it can be assumed that the PASC reaction rate of Example 2 was lower than in Example 1 due to the increased depth of diffusion of sodium ions into the titanium dioxide coating of Example 2, i.e. to a greater percentage of the total PASC thickness of the titanium dioxide coating in Example 2 than in Example 1 . It can be assumed that in Example 2, sodium ions migrated from the glass sample to the PASC coating in the cooling furnace 44. One conclusion that may result from comparing Examples 1 and 2 is that in the absence of the SIDB layer the thicker PASC coatings are less susceptible to sodium poisoning. ions, so they retain higher PASC activity.

• 4 4 94 44

44 49 4 · · ·

4·4 4 9 4949

4 9 4 ·» 4 4 4 9 • 4 4 4 ·

Example 3

PASC coating on SIDB layer created by CVD method

In this example, the effect of the presence of the SIDB tin oxide layer on PASC activity was examined. The SIDB tin oxide layer was formed on the air side of four pieces of float glass and some physical characteristics of the SIDB layer were investigated. Then, another sixteen float glass pieces were coated with the SIDB tin oxide layer by the CVD method, and each of these SIDB tin oxide layers was covered with a PASC coating of the titanium dioxide deposited by the CVD method. From each of the 16 PASC coated and SIDB coated float glass pieces, one sample was cut and the sixteen samples were covered with a stearic acid test layer. These sixteen samples with a stearic acid test layer, PASC titanium dioxide coating, and SIDB tin oxide layer were exposed to ultraviolet radiation and the PASC reaction rates were determined for these samples.

3A. Investigation of SIDB layer

The SIDB layer was deposited by the CVD method using the CVD device described in Example 1 on the air side of four pieces of glass approximately 5 inches x 12 inches x 0.16 inches (12.7 cm x 30.48 cm x 0.4cm), cut from a soda-lime-silica float glass belt. This SIDB layer was a SIDB tin oxide layer and the effect of metal precursor concentration, water vapor concentration, CVD line speed, preheating temperatures, and SIDB layer thickness on the SIDB tin oxide layer was determined. To create a SIDB layer

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The first of four pieces of glass was coated with a SIDB tin oxide layer by the CVD method using the apparatus of Example 1 by introducing MBTTCL steam of about 1.5% and water steam of about 1.5% in the air carrier gas to the air side of the glass. The preheating temperature was about 648 ° C (1200 ° F) and the line speed for this piece of glass was about 50 inches (127 cm) per minute. As determined by YOUR, the SIDB tin oxide layer thus formed had a thickness of about 3500Å. The measured resistivity and particle size of the SIDB layer were about 4.6 x 10³ ohm.cm and 198A respectively.

Similarly, the second piece of glass was coated with a SIDB layer of tin oxide, the line speed was reduced to about 20 inches (50.8 cm) per minute and the MBTTCL steam and water vapor concentrations were reduced to about 0.5% in the air carrier gas. The preheating temperature was maintained at about 648 ° C (1200 ° F). The SIDB tin oxide layer thus formed had a thickness of about 4340Å, as determined by YOUR. A resistivity of about 3.9 x 10 'was found³ ohm.cm and particle size around 185A.

Similarly, a third sample was coated with the SIDB tin oxide layer, reducing the preheat temperature to about 480 ° C (900 ° F) while the line speed increased to about 50 inches per minute. In the air carrier gas, the MBTTCL concentration was about 1.5%, the water vapor concentration was about 1.5%. The resulting SIDB layer ·· stannic oxide had a thickness of about 1000Å, as determined by YOUR, a resistivity of about 3.8 x 10 '² ohm-cm and particle size around 59Å.

Similarly, a fourth piece of glass was coated with the SIDB layer of tin oxide, the preheating temperature was maintained at about 480 ° C (900 ° F), and the line speed was reduced to 20 inches (50.8 cm) per minute. In the air carrier gas, the MBTTCL concentration was about 0.5% and the water vapor concentration was about 0.5%. The SIDB thickness of the tin oxide layer was determined by YOUR about 1010A, the resistivity was about 2 x 10 '² ohm-cm and particle size around 78Å.

It has been concluded from the foregoing that the resistivity and particle size may vary within these temperature ranges, concentrations, line speeds, and SIDB layer thicknesses, but it was found that all four pieces of glass had a tin structure.

3B, PASC Coating on SIDB Oxide Layer

Stannous CVD method

Sixteen additional 5 x 12 x 0.16 inches (12.7 x 30.48 x 0.4 cm) float glass pieces were coated with a SIDB tin oxide CVD coating machine in a manner generally described in Example 3A. Further, they were coated with a PASC coating of titanium dioxide using a CVD device as described generally in Example 1. For this coating operation, a pair of successive coating units (one for the SIDB layer and one for the PASC coating) were used in the coupled CVD process. Overlapping the SIDB layer with a PASC coating makes separate analysis of the SIDB layer difficult, if not impossible, and therefore it has been assumed that the tin oxide SIDB layers overlapped with a titanium dioxide PASC coating have the same properties as the tin oxide overlay layers described above in Section 3A, although both the SIDB layers and the PASC coatings were applied to sixteen glass pieces at various specific parameters, as will be described in more detail below and as shown in Table 1.

Sixteen SIDB tin oxide layers were deposited from precursors containing a metal consisting of MBTTCL steam in an air carrier gas mixed with water vapor, also airborne. The MBTTCL steam temperature was maintained at about 160 ° C (320 ° F). The total flow rate was 60 slm and the corresponding suction adaptation ratio was 115%. The groove width was 0.16 cm (1/16 inch). The specific coating parameters that varied for the SIDB layers produced in this example included preheat zone temperature 94. line speed, MBTTCL concentration, water vapor concentration, and SIDB layer thickness. In Table 1 below, the coating parameters of the SIDB tin oxide layer and the expected SIDB layer thickness for each of the sixteen pieces of glass. Actual thickness measurements were not made; the expected thicknesses are based on the results obtained in Section 3A. The sixteen pieces in Table 1 are divided into four groups, each of four substrates, based on the preheat temperature and the line speed.

♦ ·· ♦·· • · ·

Table 1

CVD coating parameters SnO₂ barrier layers against the diffusion of sodium ions

<td>group C.</td><td>sample no.</td><td>temperature preheating ° F</td><td>speed feed inches / min</td><td>volume of conc. H₂%</td><td>concentr. MBTTCL %</td><td>presumption layer SIDB thickness</td>

<td></td><td> 1</td><td> 900</td><td> 20</td><td> 0,5</td><td> 0,5</td><td> 1010</td>

<td> 1</td><td> 2</td><td> 900</td><td> 20</td><td> 0,5</td><td> 0,5</td><td> 1010</td>

<td> 1</td><td> 3</td><td> 900</td><td> 20</td><td> 0,5</td><td> 0,5</td><td> 1010</td>

<td></td><td> 4</td><td> 900</td><td> 20</td><td> 0,5</td><td> 0,5</td><td> 1010</td>

<td></td><td> 5</td><td> 900</td><td> 50</td><td> 1,5</td><td> 1,5</td><td> 1000</td>

<td>II</td><td> 6</td><td> 900</td><td> 50</td><td> 1,5</td><td> 1,5</td><td> 1000</td>

<td>II</td><td> 7</td><td> 900</td><td> 50</td><td> 1,5</td><td> 1,5</td><td> 1000</td>

<td></td><td> 8</td><td> 900</td><td> 50</td><td> 1,5</td><td> 1,5</td><td> 1000</td>

<td>III</td><td> 9</td><td> 1200</td><td> 20</td><td> 0,5</td><td> 0,5</td><td> 4340</td>

<td></td><td> 10</td><td> 1200</td><td> 20</td><td> 0,5</td><td> 0,5</td><td> 4340</td>

<td></td><td> 11</td><td> 1200</td><td> 20</td><td> 0,5</td><td> 0,5</td><td> 4340</td>

<td></td><td> 12</td><td> 1200</td><td> 20</td><td> 0,5</td><td> 0,5</td><td> 4340</td>

<td>IV</td><td> 13</td><td> 1200</td><td> 50</td><td> 1,5</td><td> 1,5</td><td> 3500</td>

<td></td><td> 14</td><td> 1200</td><td> 50</td><td> 1,5</td><td> 1,5</td><td> 3500</td>

<td></td><td> 15</td><td> 1200</td><td> 50</td><td> 1,5</td><td> 1,5</td><td> 3500</td>

<td></td><td> 16</td><td> 1200</td><td> 50</td><td> 1,5</td><td> 1,5</td><td> 3500</td>

Each of the sixteen pieces of glass coated with the SIDB layer was overlaid with a PASC coating of titanium dioxide deposited in a second coating CVD unit downstream of the first coating SIDB unit in which the TTIP vapor was a precursor containing a metal in the nitrogen carrier gas (N₂) directed to the surface of the glass pieces covered with the SIDB layer. Ammonia (NH 3) was added to the TTIP / carrier gas mixture in eight of the sixteen glass pieces. The carrier gas was maintained at about 113 ° C (235 ° F) for all sixteen pieces. The sixteen pieces were annealed as in Example 1. The TTIP atomizer temperature was maintained at about 104.4 ° C (220 ° F). Table 2 lists the PASC titanium dioxide coating parameters for these sixteen pieces of glass.

44 • 4 4 4 • · · 4

444 444

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These pieces of glass in Table 2 are divided into four groups of four according to the preheating temperature and the feed rate.

Table 2

PASC parameters of TiO coating₂

<td>Group C.</td><td>Sample C.</td><td>Temperature preheating ° F</td><td>speed feed inches / mi n</td><td>total speed flow L / min</td><td>odsáv neither %</td><td>TTIP ends ntrac e%</td><td>nh₃concentr ace%</td><td>width grooves inches</td>

<td> 1</td><td> 1</td><td> 900</td><td> 20</td><td> 35</td><td> 105</td><td> 0.1</td><td> 0</td><td> 1/16</td>

<td></td><td> 2</td><td> 900</td><td> 20</td><td> 75</td><td> 105</td><td> 0,4</td><td> 0</td><td> 3/16</td>

<td></td><td> 3</td><td> 900</td><td> 20</td><td> 35</td><td> 125</td><td> 0,4</td><td> 20</td><td> 1/16</td>

<td></td><td> 4</td><td> 900</td><td> 20</td><td> 75</td><td> 125</td><td> 0,1</td><td> 2</td><td> 3/16</td>

<td>II</td><td> 5</td><td> 900</td><td> 50</td><td> 75</td><td> 125</td><td> 0,4</td><td> 0</td><td> 1/16</td>

<td></td><td> 6</td><td> 900</td><td> 50</td><td> 35</td><td> 125</td><td> 0,1</td><td> 0</td><td> 3/16</td>

<td></td><td> 7</td><td> 900</td><td> 50</td><td> 75</td><td> 105</td><td> 0,1</td><td> 20</td><td> 1/16</td>

<td></td><td> 8</td><td> 900</td><td> 50</td><td> 35</td><td> 105</td><td> 0,4</td><td> 20</td><td> 3/16</td>

<td>III</td><td> 9</td><td> 1200</td><td> 20</td><td> 75</td><td> 125</td><td> 0,1</td><td> 0</td><td> 1/16</td>

<td></td><td> 10</td><td> 12000</td><td> 20</td><td> 35</td><td> 125</td><td> 0,4</td><td> 0</td><td> 3/16</td>

<td></td><td> 11</td><td> 1200</td><td> 20</td><td> 75</td><td> 105</td><td> 0,4</td><td> 20</td><td> 1/16</td>

<td></td><td> 12</td><td> 1200</td><td> 20</td><td> 35</td><td> 105</td><td> 0,1</td><td> 20</td><td> 3/16</td>

<td>IV</td><td> 13</td><td> 1200</td><td> 50</td><td> 35</td><td> 105</td><td> 0,4</td><td> 0</td><td> 1/16</td>

<td></td><td> 14</td><td> 1200</td><td> 50</td><td> 75</td><td> 105</td><td> 0,1</td><td> 0</td><td> 3/16</td>

<td></td><td> 15</td><td> 1200</td><td> 50</td><td> 35</td><td> 125</td><td> 0,1</td><td> 20</td><td> 1/16</td>

<td></td><td> 16</td><td> 1200</td><td> 50</td><td> 75</td><td> 125</td><td> 0,4</td><td> 20</td><td> 3/16</td>

* The preheat temperature refers here to the temperature of the preheat zone 94. There was only one preheat operation and the preheat temperatures shown here are the same temperatures to which pieces of glass were preheated in the preheat zone while moving the coating machine 88. coating before entering the cooling zone 98.

·»»· · · ·· ·· • »» ·♦ 9 9 9 9

999 9 9 9999

9 9 9 · ··· 999

9 9 9 9

In Table 3 below, the selected properties of each of the sixteen pieces of glass after application of the PASC coating as described in Table 2 are selected. is the line speed and precursor concentration. The surface roughness and particle size of the PASC coating were determined in order to correlate PASC activity with the roughness and particle size. Surface roughness measurements were made on the basis of Atomic Force Microscope (AFM) measurements performed on a PASC coating. It has been found that there are large differences in surface roughness, particle size and crystalline phase as a function of preheating temperature.

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* · ·* · • * · • · ·· • ♦ · • »· ·· ·· · ·· » • · · · · • · ·»· ··· • · · • ··· ♦· ··

3C. Description of testing PASC activity of sixteen substrates

A 1 inch x 4 inch (2.54 x 10.16 cm) sample or test strip was cut out from the center of each of the sixteen PASC-coated and SIDB-coated glass pieces. Each of the sixteen test strips was centrifuged over a stearic acid test layer as described in Example 1. Then, the sixteen test strips were exposed to ultraviolet light from a 20W / m black light source.² over a period of 7 hours of cumulative time periods to induce photocatalytically activated self-cleaning of the stearic acid test layer.

Because it has been found that the thickness of the stearic acid test layer varies over the length of the 1x4 inch (2.54 x 10.16 cm) test strips (i.e. a thicker stearic acid test layer at each end of the test strips, and a thinner stearic acid test layer toward the center of each test strip, by applying a centrifugal force to the stearic acid dropped onto the center of the rotating test strip as described above and visually observed the length of these test strips), photocatalytic activity was measured at each end of each of the sixteen test strips, using an FTIR spectrophotometer equipped with an MCT detector. The PASC response rates obtained by FTIR spectroscopic tests are shown in Table 4 for each pair of tests performed on each of the sixteen test strips.

Table 4 flfl fl flfl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl fl

Photocatalytically activated self-cleaning activity of 16 test strips

<td>group C.</td><td>sample no.</td><td>PASC activity rate left side of test strip x 10 '³ cm '¹ min '¹</td><td>PASC activity rate right side of test strip x 10 '³ cm¹ min '¹</td>

<td></td><td> 1</td><td> 0,39</td><td> 0,45</td>

<td>AND</td><td> 2</td><td> 0,32</td><td> 0,28</td>

<td>l</td><td> 3</td><td> 0,26</td><td> 0,31</td>

<td></td><td> 4</td><td> 0,4</td><td> 0,39</td>

<td></td><td> 5</td><td> 0,5</td><td> 0,57</td>

<td>II</td><td> 6</td><td> 0,23</td><td> 0,14</td>

<td>II</td><td> 7</td><td> 0,27</td><td> 0,22</td>

<td></td><td> 8</td><td> 0,014</td><td> 0,019</td>

<td></td><td> 9</td><td> 0,23</td><td> 0,048</td>

<td>III</td><td> 10</td><td> 0,96</td><td> 0,77</td>

<td>III</td><td> 11</td><td> 0,4</td><td> 0,31</td>

<td></td><td> 12</td><td> 0,52</td><td> 0,43</td>

<td>ÍV</td><td> 13 14 15 16</td><td> 1,18 0,73 0,42 0,25</td><td> 0,94 0,77 0,41 0,35</td>

It can be seen from Table 4 that for some test strips there is a significant difference in activity between the two ends of the test strip. This difference is believed to be related to the unevenness of the stearic acid layer thickness on the test strip.

According to Table 4, there appears to be insufficient correlation between deposition conditions and PASC activity of the PASC coating applied to the SIDB layer. Table 4 shows that based on the activity of the left side of the test strips, the three test strips, 13, 10 and 14, are most active.

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These strips 13, 10 and 14 correspond to a higher preheating temperature of 1200 ° F (648.8 ° C). When the remaining 13 test strips are ranked according to PASC activity, a mixture of preheating temperatures as well as other coating parameters is seen indicating that the presence of a sodium ion diffusion barrier layer can prevent sodium ion poisoning of the PASC coating and allow a greater range of coating conditions and parameters, in which still photocatalytic activity is obtained.

Example 4

.......--in--

PASC coating formed by spray pyrolysis

In this example, the pieces of glass were spray coated with PASC with a titanium dioxide coating of varying thickness to determine the effect of this PASC coating thickness on PASC activity.

Three pieces of float glass, each 4 x 4 x 0.16 inches (10.16 x 10.16 x 0.4 cm) each had an air side coated with a PASC titanium dioxide coating formed by spray pyrolysis.

The basic parts of the spray pyrolysis apparatus used to form the PASC coating on the glass pieces are shown in Figure 4. The apparatus comprises a preheating zone 120 and a pyrolytic spray zone 122. A piece of glass 126 was conveyed by a conveyor (not shown) to the preheating zone 120 where it was heated by a plurality of electric heaters 130 to a temperature in the range of about 600 ° C to 700 ° C (1112 ° F to 1292 ° F). This piece of glass 126 was further transported behind the oscillating spray nozzle 132, which was positioned approximately 10 inches (25 inches). 4 cm) above the air side of the piece 126 of glass. The aqueous suspension of the organometallic coating reactants 134 was suspended in the mixing chamber 138 by means of a stirrer 136. This water suspension 134 was passed through line 140 to the spray nozzle 132 where it was mixed with the compressed air in any suitable manner (compressed air is routed from the compressed air source 142 to the spray nozzle 132 through the line 144). The spray shape 146 was formed by spraying a mixture of water suspension 134 and compressed air from the nozzle 132 onto the surface of the glass piece 126 and pyrolyzed to form a PASC coating on the glass piece 126. The PASC-coated piece 126 of glass was cooled in air.

For this example, acetylacetone titanium oxide was selected as the organometallic coating reactant 134, and the rate of water suspension fed to the surface of the three pieces of glass 126 was controlled to produce a PASC coating of the desired thickness on each piece of glass. The thicknesses were 400A, 725A and 1000A. All coating parameters were kept constant to determine the effect of PASC coating thickness on photocatalytic activity for PASC sprayed pyrolysis on pure float glass without SIDB barrier layer.

Table 5 shows the specific coating parameters for this example.

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<td>a coating reactant</td><td>acetylacetone titanoxid</td><td>acetylacetone titanoxid</td><td>acetylacetone titanoxid</td>

<td>speed feed inches / min</td><td>m</td><td> 75</td><td>m N-</td>

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After the PASC titanium dioxide coating was applied, each of the three glass pieces was cut into four 1x4 inch (2.54x10.16 cm) test strips to give a total of 12 test strips.

One test strip from each of the three original glass pieces was subjected to X-ray diffraction analysis. From this analysis, it was found that all of the three glass pieces had strong X-ray diffraction lines corresponding to anatase titanium dioxide.

To evaluate the photocatalytic activity of the three glass pieces, one test strip of each of the three glass pieces was each coated with a stearic acid test layer as described in Example 1. The three test strips were then exposed to ultraviolet radiation of 20W for seven hours for a cumulative period of time. / m² from a black light source placed perpendicular to the coated side of each test strip. The photocatalytic reaction rate of each of the three test strips was quantitated by FTIR spectroscopy using an MCT detector as described above. The photocatalytic reaction rate for the three test strips is shown in Table 5.

From the foregoing, it can be concluded that low but acceptable photocatalytic reaction rates can be obtained by PASC coatings produced by the spray pyrolysis technique without poisoning the PASC coating with sodium ions. It can also be concluded that thicker PASC coatings increase PASC activity, as demonstrated by Sample C in Table 5.

Example 5

Comparison of PASC coatings created by spray pyrolysis with and without SIDB layer and determination of the effect of annealing after PASC coating application

In this experimental setup, eight pieces of glass were coated with a PASC coating using a spray pyrolysis method to determine the effect of the presence or absence of the SIDB layer, the thickness of the PASC coating and the substrate temperature during PASC coating deposition on the PASC reaction rate of the PASC coating.

The air side of four of the eight pieces of 4 millimeter floated Solex® float glass was coated with a 500Å thick SIDB tin oxide layer which was spray coated with dibutyltin fluoride (C4H) water spray₉) 2SnF₂ and wetting agents. The SIDB tin oxide layer was applied by spray pyrolysis apparatus and as described in Example 4. After applying the SIDB layer, the glass samples were cooled to room temperature, the four glass pieces and the remaining four glass pieces were coated with a PASC titanium dioxide coating over the SIDB layer. to room temperature. It should be noted that four pieces of glass coated with the SIDB layer, which were cooled to room temperature between the application of the SIDB layer and the PASC coating and then reheated before applying the PASC coating, were prepared in this way because the laboratory spray pyrolysis apparatus used in this experiment had only one spray pyrolysis site, requiring a transition from a dibutiltin difluoride slurry (to form an SIDB layer) to an acetylacetone titanium oxide slurry (to form a PASC coating). This intermediate step of cooling would be avoided in a preferred embodiment of the coating machine, e.g. provided with two spray pyrolysis sites for subsequent application of a SIDB layer and a PASC coating to a moving substrate, such as a continuous float glass web, without intermediate annealing.

After all eight PASC coated glass pieces were cooled to room temperature, the glass pieces were covered with the stearic acid layer described in Example 1 and then exposed to ultraviolet radiation of a UVA 340 light source positioned perpendicular to the coated side of the glass pieces to form intensity 20 W / m² on the surface of the PASC coating. The reaction rate of the PASC reaction to remove the stearic acid test bed was quantitatively determined using the method described in Example 1. This reaction rate is recorded in Table 6, below, in the 0.00min header column. It should be noted that the parameter O.OOmin refers to the fact that a piece of glass having a PASC coating formed was then allowed to cool to room temperature and not be annealed; it does not refer to the accumulated exposure time to ultraviolet radiation.

The effect of the annealing time on stearic acid removal was determined as follows. The remaining stearic acid test layer was washed from the PASC coating of each of the eight glass pieces by wiping the surface with a cloth impregnated with methanol until no stearic acid layer or haze was observed. Then, the eight pieces of glass were gradually placed in an oven maintained at about 932 ° F for about 3 minutes to heat the individual pieces of glass. The heating furnace was turned off, the furnace door opened, and each of the pieces of glass was left in the furnace until it had cooled to about room temperature. The low cooling rate in the furnace provided annealing. Each of the individual pieces of glass was then covered with a new stearic acid test layer, exposed to ultraviolet light, and the PASC reaction rate was determined in the same manner as the non-ignited PASC coating described immediately above in this example. The remaining stearic acid test layer was washed again from the surface of each individual piece of glass as described above, and each piece of glass was individually subjected to additional heating for 10 minutes and left in the furnace to slowly cool in the same manner resulting in a 13 minute accumulated heating time. after which the stearic acid test layer was reapplied as described and the PASC reaction rate was determined as above. The process was repeated one more time to obtain a 73 minute accumulated heating time followed by slow cooling in the furnace that provides annealing.

The properties of the SIDB layer and PASC coating and the rate of PASC reaction versus accumulated annealing time for these eight glass pieces (D-K) are shown in Table 6 below.

• ·

Table 6

Reaction rates of photocatalytic activity of PASC coatings with and without barrier layer against sodium ion diffusion

<td rowspan="2">sample C.</td><td rowspan="2">Barrier layer</td><td rowspan="2">Thickness TiO₂</td><td rowspan="2">Glass temperature during TiO application₂</td><td colspan="4">Photocatalytic activity * after annealing at 500 ®C for</td>

<td>0.0 min</td><td>2 min</td><td>10 min</td><td>73 min</td>

<td>D</td><td>none</td><td>400 A</td><td>t145 ° F</td><td> 0,72</td><td> 1,05</td><td>94, 94</td><td> ***</td>

<td>E</td><td>none</td><td>625 A</td><td>1147 ° F</td><td> 0,69</td><td> 1,05</td><td> 1,67</td><td> 2,97</td>

<td>F</td><td>500 A SnO2</td><td>400 A</td><td>1147 ° F</td><td> 2,39</td><td> 5,02</td><td> 7,39</td><td> ***</td>

<td>G</td><td>500 A SnO2</td><td>625 A</td><td>1153 ° F</td><td> 2,23</td><td> 5,35</td><td> 8,74</td><td> 5,13</td>

<td>H</td><td>none</td><td>400 A</td><td>1270 ° F</td><td> 2,05</td><td> 6,59</td><td> 5,14</td><td> ***</td>

<td> 1</td><td>none</td><td>625 A</td><td>1270 ° F</td><td> 4,71</td><td> 7,99</td><td> 9,95</td><td> 5,39</td>

<td>J</td><td>500 A SnO2</td><td>400 A</td><td>1300 ° F</td><td> 2,4</td><td> 5,26</td><td> 3,73</td><td> ***</td>

<td>TO</td><td>500 A SnO₂</td><td>625 A</td><td> 1280⁰ F</td><td> 4,64</td><td> 12,29</td><td> 5,57</td><td> 4,4</td>

PASC reaction rate to remove stearic acid (x 10 '³cm '¹min '¹)

The results of the photocatalytic analysis shown in Table 6 indicate that the thickness of the titanium dioxide layer around 625Å without the barrier layer (Sample I) can approximate the PASC activity of the thinner 400Å PASC coating on the SIDB layer (Sample K). It should be noted that for Sample K, the SIDB layer was subjected to cooling between operations and subsequent reheating as described, where the reheating operation could reduce the SIDB layer efficiency for Sample K, which could otherwise have higher PASC activity.

Sample K from Table 6 also shows how significant the annealing time can have on the PASC reaction rate. After 3 minutes annealing, the PASC activity of Sample K increased from about 4.64 to about 12.29 x 10³cm '¹min¹, but subsequently declined with further annealing. It is believed that during annealing a PASC titanium dioxide coating was formed in the atanasase phase when PASC activity was measured after a three minute period and was formed without appreciable sodium ion poisoning due to the presence of tin oxide in the SIDB layer. While not wishing to be bound by this particular theory, it is believed that continued annealing for too long accumulated time may induce sodium ion poisoning, despite the presence of the SIDB layer, which could explain the decrease in PASC activity of Sample K.

The above examples illustrate the present invention, but the invention is not limited thereto.

Although the aforementioned methods of forming a PASC coating have been described in connection with the formation of such coatings on a continuous moving substrate, such as a float glass web, during the manufacture of this substrate, it should be understood that these methods could also be used in other stages of the manufacturing process. substrate. For example, PASC coatings could be formed on substrates including, but not limited to, glass substrates as part of the bending and / or tempering processes of the substrate. For example, when the glass substrate is heated for subsequent bending and / or tempering, a PASC coating with or without the SIDB layer by spray pyrolysis or CVD or MSVD techniques described above may be formed thereon prior to the bending / tempering. The CVD method and spray pyrolysis can be used when the glass substrate is heated to the bending / tempering temperature. The PASC coating with or without the SIDB layer may be applied to the glass substrate in a post-reheat operation after bending / tempering by any of the CVD, spray pyrolysis or MSVD methods.

It is believed that there are differences in the PASC coatings prepared by the sol-gel process and in the PASC coatings prepared by the above methods. For example, it is expected that PASC coatings prepared by the sol-gel method may be more porous, less dense, generally thicker, and less applicable for use as transparent and may contain more OH groups than layers prepared by the CVD process or by spray pyrolysis. As mentioned above, an excess of OH groups is undesirable as it can block the formation of the correct crystalline form in the PASC coating, which can result in a decrease in PASC activity. PASC coatings prepared by CVD or spray pyrolysis are expected to have a finer grain structure than layers prepared by the sol-gel method.

Advantages of the present invention over the sol-gel PASC coating process include the ability to form a thin dense PASC layer on the substrate over the much thicker porous coatings obtained by the sol-gel coating method. Since the PASC coatings of the present invention are thin, they are aesthetically acceptable for use as transparent coatings on glass substrates. A further advantage is that the PASC coating method of the present invention eliminates the need to re-heat the substrate after applying the coating or coating precursor as required by the currently available sol-gel method. This makes the present method not only less expensive and more efficient, for example due to lower equipment costs, energy costs, shorter production time, but also in the present invention, the opportunity for sodium ion migration and thus sodium poisoning of the PASC coating is significantly reduced. Furthermore, the method of the present invention can easily be adapted to form PASC coatings on continuous moving substrates, such as a float glass ribbon, for which the present sol-gel process cannot be so easily adapted.

• · • · • · · ·

The scope of the invention encompasses many modifications as defined in the following claims.