Photo-induced hydrophilic article and method of making same.

(54) Title: PHOTO-INDUCED HYDROPHILIC ARTICLE AND PRODUCTION METHOD THEREOF. (54) Title: PHOTO-INDUCED HYDROPHILIC ARTICLE AND METHOD OF MAKING SAME.

(57) Summary

Methods and articles are described in which a substrate is provided with a photo-induced hydrophilic surface by formation of a photo-induced hydrophilic coating on the substrate by spray pyrolysis, chemical vapor deposition or vacuum deposition by magnetron bombardment. The coating can have a thickness of 50 A, to 500 A, a root mean square less than 5, preferably less than 2, and a photocatalytic activity less than 3.0 x 10-3 cm-1 min-1 + 2x10-3 cm-1 min-1. The substrate includes glass substrates, including glass sheets and continuous float glass strips.

(57) Abstract

Methods and articles are disclosed in which a substrate is provided with a photo-induced hydrophilic surface by forming a photo-induced hydrophilic coating on the substrate by spray pyrolysis, Chemical vapor deposition, or magnetron sputter vacuum deposition. The coating can have a thickness of 50 ANGSTROM to 500 ANGSTROM, a root mean square roughness of less than 5, preferably less than 2, and photocatalytic activity of less than 3.0 x 10-3 cm-1 min-1 +/- 2.0 x 10-3 cm-1 min-1. The substrate ineludes glass substrates, including glass sheets and continuous float glass ribbons.

(12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)

<td>(19) World IntellectualProperty Organization International Bureau</td><td></td><td>ininiianiiiniiiiiiiiinninii</td>

<td>(43) International Publication Date October 31, 2002 (October 31, 2002)</td><td>PCT</td><td>(10) International Publication Number WO 02/085809 A2</td>

ΙΙΙΙΜΙΙΙΙΙΙΙΠίη ^ζν 608S80 / r0OM (51) International Patent Classification⁷: C03C 17/245 (21) International Application Number: PCT / US02 / 05260 (22) International Filing Date: 22 February 2002 (22.02.2002) (25) Filing Language: English (26) Publication Language: English (30) Priority Data:

60 / 272,197 28 February 2001 (28.02.2001) US

Not fumished 14 Febniary 2002 (14.02.2002) US (71) Applicant: PPG INDUSTRIES OHIO, INC. [US / US]; 3800 West 143rd Street, Cleveland, OH 44111 (US).

(72) Inventors: HARRIS, Caroline, S .; 921 Farragut Street Pittsburgh, PA 15206 (US). SZANYI, Janos; 138 New Haven Court, Richland, WA 99352 (US).

(74) Agents: STACHEL, Kenneth, J, et a] .; PPG Industries, Inc., One PPG Place, Pittsburgh, PA 15272 (US).

(81) Designated States (national): AE, AG, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, BZ, CA, CH, CN, CO, CR, CU, CZ, DE , DK, DM, DZ, EC, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS, JP, KE, KG, KP, KR, KZ, LC , LK, LR, LS, LT, LU, LV, MA, MD, MG, MK, MN, MW, MX, MZ, NO, NZ, OM, PH, PL, PT, RO, RU, SD, SE, SG , SI, SK, SL, TJ, TM, TN, TR, TT, TZ, UA, UG, UZ, VN, YU, ZA, ZM, ZW.

(84) Designated States (regional) ·. ARIPO patent (GH, GM, KE, LS, MW, MZ, SD, SL, SZ, TZ, UG, ZM, ZW), Eurasian patent (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM ), European patent (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, .NL, PT, SE, TR), OAPI patent (BF, BJ, CF, CG, CI, CM, GA, GN, GQ, GW, ML, MR, NE, SN, TD, TG).

Published:

- mthout Internationa! search report and to be republished upon receipt of tkat report

For two-letter codes and other abbreviations, refer to the Guidance Notes on Codes and Abbreviations appearing at the beginning of each regular issue of the PCT Gazette.

(54) Title: PHOTO-INDUCED HYDROPHILIC ARTICLE AND METHOD OF MAKING SAME

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(57) Abstract: Methods and arricies are disclosed in which a substrate is provided with a photo-induced hydrophilic surface by forming a photo-induced hydrophilic coating on the substrate by spray pyrolysis, Chemical vapor deposition, or magnetron sputter vacuum deposition. The coating can have a thickness of 50 A to 500 A, a root mean square roughness of less than 5, preferably less than 2, and photocatalytic activity of less than 3.0 X 10 '³ cm '¹ min '¹ ± 2.0 x 10³ cm '¹ min '¹. The substrate ineludes glass substrates, including glass sheets and continuous float glass ribbons.

PHOTO-INDUCED HYDROPHILIC ARTICLE AND PRODUCTION METHOD OF

SAME

one. Field of the Invention [0002] The present invention relates to methods for depositing hydrophilic coatings on a substrate (eg, a sheet of glass or a continuous float glass strip) and articles of manufacture prepared according to the methods.

2 . Technical Considerations [0003] In the following discussion, general technical considerations in relation to the present invention will be discussed. However, the specific references discussed herein should not be considered to constitute prior art under United States patent regulations and no such acceptance is made.

[0004] For many substrates, for example glass substrates such as architectural windows, automotive transparencies and airplane windows, it is desirable for good visibility that the surface of the substrate is substantially free of surface contaminants, such as contaminants from common organic and inorganic surface, for as long as possible. Traditionally, this has meant that these surfaces need to be cleaned frequently. This cleaning operation is typically carried out by manually wiping the surface with or without the aid of chemical cleaning solutions. This approach can be labor intensive, on time and / or cost. Therefore, there is a need for substrates, particularly glass substrates, that have surfaces that are easier to clean than existing substrates and that reduce the need or frequency of such manual cleaning.

[0005] It is known that some semiconductor metal oxides can be incorporated into a coating to obtain photocatalytically activated coatings (hereinafter FA) that have self-cleaning properties, that is, coatings that, by exposure to certain electromagnetic radiation, interact with organic pollutants from the coating surface to degrade or decompose contaminants. A bibliography of patents and articles related, in general, with photocatalytic oxidation of organic compounds is given in Bibliography of

Work on The Photocatalytic Removal of Hazardous Compounds from Water and Air, D. Blake, National Renewable Energy Laboratory (May 1994), and in an October 1995 update and in an October 1996 update.

[0006] Typically, these FA coatings are produced thick enough to have sufficient photocatalytic activity to destroy or decompose the organic contaminants on top of the coating in as short a time as possible. For example, WO 00/75087 describes a photocatalytically activated coating having a minimum photocatalytic activity of 5 x 10-3 centimeters-1 minute-1 (cm-1 min-1). Coatings are described

Additional FAs, for example, in US Pat. No.

5,873,203, 6,027,766, and 6,054,227.

[0007] In addition to their self-cleaning properties, these FA coatings are also typically hydrophilic, that is, they are wetted with water. The hydrophilicity of FA coatings helps to reduce fogging, that is, the accumulation of water droplets on the coating, which can reduce visible light transmission and visibility through the coated substrate. This hydrophilicity has hitherto been associated with several factors, among which are a greater surface roughness (roughness) of the surface of the coating and a greater porosity of the coating. For example, US Patent No. No. 6,103,363 discloses a photocatalytically self-cleaning hydrophilic self-cleaning coating having a preferred root mean square surface area (MC) of 5 nanometers (nm) at 15 nm and a preferred porosity of 70% to 90%. However, this degree of surface roughness can make surface cleaning more difficult, for example by producing small pockets where dirt and grime can accumulate, or by clogging or tearing fibers from a clean cloth rubbed onto the surface. . Furthermore, the increased porosity of the coating provides channels through which the underlying substrate can be chemically attacked.

[0008] In order to achieve previously desired levels of coating thickness, photocatalytic activity, surface roughness, and coating porosity, many FA self-cleaning coatings have been deposited by sol-gel techniques. In a typical sol-gel procedure, an uncrystallized colloidal suspension is deposited on a substrate at or near room temperature and then heated to form a crystallized coating. For example, US Patent No. No. 6,013,372 describes a hydrophilic photocatalytic self-cleaning coating formed by mixing photocatalyst particles in a metal oxide layer and applying the mixture to a substrate by a sol-gel procedure.

[0009] However, conventional sol-gel coating methods are not economically or practically compatible with certain application conditions or substrates. For example, in a conventional float glass procedure, the float glass strip in the molten metal bath may be too hot to accept the sol due to evaporation or chemical reaction of solvent used in the sol. Additionally, the environment in the molten metal bath does not lead to movement of machinery, such as spray devices, that would be needed to apply the sun. Therefore, the sol should typically be applied after the float glass strip has exited the molten metal bath and has cooled to approximately room temperature. The coated web must then be reheated to a temperature sufficient to crystallize the coating. Such cooling and reheating operations require a substantial investment of equipment, energy, and handling costs and significantly reduce production efficiency. In addition, overheating a sodium-containing substrate, such as soda-lime-silica glass, increases the opportunity for sodium ions in the substrate to migrate to the coating, which is conventionally referred to as sodium ion poisoning of the coating deposited. The presence of these sodium ions can reduce or destroy the photocatalytic activity of the self-cleaning coating. Furthermore, the sol-gel method typically produces thick coatings, for example, several microns thick, which can have an adverse effect on the optical and / or aesthetic properties of the coated articles. Typically, as the thickness of the self-cleaning coating FA increases, the light transmittance and reflectance of the coating go through a series of minima and maxima due to the effects of optical interference. The reflected and transmitted color of the coating also varies due to these optical effects. Thus, coatings that are thick enough to give the desired self-cleaning properties may have undesirable optical characteristics.

Therefore, it would be advantageous to have an article of manufacture having a coating, in particular a hydrophilic coating, and a method of producing the article that reduces or eliminates at least some of these drawbacks.

SUMMARY OF THE INVENTION [0011] The present invention is directed to an article of manufacture that includes a substrate having at least one surface and a hydrophilic coating, in particular a photoinduced hydrophilic coating (defined below), deposited on at least a portion Of the surface. The coating can be deposited by a process selected from chemical vapor deposition (hereinafter DQV), spray pyrolysis and / or vacuum deposition by magnetron bombardment (hereinafter DVBM). In one embodiment, the liner, for example an outer surface of the liner, may have a root mean roughness in the range of greater than or equal to 0 nm to less than or equal to 4 nm, for example less than or equal to 3 nm, for example less than or equal to 2 nm, for example less than or equal to 1 nm. It is particularly advantageous if the substrate is a float glass strip and the coating is deposited in a DQV molten tin bath during the manufacture of the float glass strip. In another particular embodiment of the invention, the photoinduced hydrophilic coating has a photocatalytic activity of greater than or equal to 0 cm-1 min-1 to less than or equal to 3 x 10-3 cm-1 min-1, for example less than or equal at 2 x 10-3 cm-1 min-1. In another embodiment of the invention, the substrate is a float glass quote located in a molten metal bath, the photoinduced hydrophilic coating has a thickness in the range of more than 0 Á to less than or equal to 5 00 Á and the coating Photoinduced hydrophilic is deposited in the molten metal bath by chemical vapor deposition. The present invention is also directed to methods of producing such articles.

[0012] Surprisingly, it has been found that very thin coatings of semiconductor metal oxides, for example of order of greater than 0 Á to less than or equal to 500 Á, are thinner than the coatings typically used to achieve self-cleaning photocatalytic properties They retain their hydrophilicity even when the photocatalytic activity of the very thin coating is below that typically desired for self-cleaning coatings to break down organic contaminants. Thus, as long as the metal oxide semiconductor coating remains photoactive enough to be hydrophilic, it cannot be photoactive enough to have measurable or commercially acceptable photocatalytic self-cleaning activity over time. This photoinduced hydrophilicity allows less fogging and / or also makes the coated article easier to clean, for example easier to rinse to remove dirt and / or water stains, than the uncoated article. Furthermore, photoinduced hydrophilicity also allows water to drain and drying faster, reducing water stains, since water does not tend to form ridges to leave stains. Dirt can also be more easily removed by simply rinsing the coating without manually rinsing the coating. Additionally, these very thin metal oxide semiconductor coatings suffer less from the undesirable optical problems associated with thicker self-cleaning photocatalytic coatings. It has also surprisingly been found that these very thin metal oxide semiconductor coatings can be produced much smoother and denser than previously thought while retaining their photoinduced hydrophilicity. An example of a suitable semiconductor metal oxide that can be used in the practice of the invention is a titanium oxide.

[0013] In one embodiment, the invention provides a substrate having at least one surface with a photoinduced hydrophilic semiconductor metal oxide coating, such as a titanium oxide coating, deposited on at least a portion of the surface by DQV, pyrolysis by spray or DVBM. The coating may have a thickness in the range of greater than 0 Á to less than or equal to 500 Á, for example less than or equal to 400 Á, for example less than or equal to 300 Á, and the external surface of the coating may have, in Generally, a roughness MC of greater than or equal to 0 nm to less than or equal to 2 nm, such as 1.9 nm or less, for example 1 nm or less. For coatings of the invention having a thickness of about 200A or less, the coating surface may be less smooth, for example may have a MC roughness of 5nm or less, for example 4.9nm or less, for example of 4nm or less, for example of 3nm or less, for example of 2nm or less, for example of 1nm or less. In a particular embodiment, the substrate is a float glass strip located in a molten tin bath.

[0014] In one embodiment, the invention provides an article consisting of a float glass strip having at least one surface and a photoinduced hydrophilic coating deposited directly on at least a portion of the at least one surface. The photochromic hydrophilic coating can be deposited directly onto the float glass strip in a molten metal bath.

The invention also provides an article consisting of a substrate having at least one surface and a photoinduced hydrophilic coating deposited on at least a portion of the at least one surface. The substrate may be a float glass strip located in a molten metal bath, the photoinduced hydrophilic coating may be 500 A or less thick, and the photoinduced hydrophilic coating may be deposited on the at least one surface in a metal bath melted by chemical vapor deposition.

The invention also provides an article consisting of a substrate having at least one surface and a photoinduced hydrophilic coating deposited on at least a portion of the at least one surface. The photoinduced hydrophilic coating can be deposited by chemical vapor deposition at a temperature in the range of

500 ° C to 1,200 ° C and the photoinduced hydrophilic coating can be 500A or less thick.

[0017] A method is provided for forming a photoinduced hydrophilic coating on at least a portion of a substrate. The method includes having a substrate having a first surface and a second surface, at least one of the surfaces having tin diffused therein; depositing a metal oxide precursor with a coating device on at least one of the surfaces by a process selected from chemical vapor deposition, spray pyrolysis, and vacuum deposition by magnetron bombardment, and heating the substrate to a temperature sufficient to decompose the metal oxide precursor and form the photoinduced hydrophilic coating having a quadratic medical roughness of 2 nm or less.

[0018] Another method of forming a photoinduced hydrophilic coating on at least a portion of a substrate is to provide a float glass strip in a molten metal bath; depositing a metal oxide precursor material with a coating device directly on an upper surface of the glass strip by chemical vapor deposition, and heating the glass strip to a temperature sufficient to decompose the metal oxide precursor material and form the coating Photoinduced hydrophilic treatment.

[0019] Another method of forming a photoinduced hydrophilic coating on at least a portion of a substrate is to dispose of a substrate having at least one surface, depositing a metal oxide precursor material with a DQV coating device on at least a portion of the at least one surface, heat the substrate to a temperature in the range of 400 ° C to 1,200 ° C to decompose the metal oxide precursor material to form the photoinduced hydrophilic coating and to provide sufficient precursor material for the photoinduced hydrophilic coating to have a thickness of 500A or less.

[0020] The invention also relates to a product formed by a method of the invention.

DESCRIPTION OF THE DRAWINGS [0021] Fig. 1 is a cross-sectional view (not to scale) of a portion of a substrate having a photoinduced hydrophilic coating of the invention deposited thereon;

[0022] Fig. 2 is a side view (not to scale) of a coating process for applying a semiconductor metal oxide coating of the invention onto a glass strip in a molten metal bath for a float glass process , and [0023] Fig. 3 is a side view (not to scale) of an insulating glass unit embodying the features of the invention.

DESCRIPTION OF THE INVENTION [0024] As used herein, terms of space or direction, such as internal, external, above, below, top, bottom, and the like, refer to the invention as shown in the figures. . However, it is to be understood that the invention may take various alternative orientations and that, accordingly, such terms are not to be considered as limiting. Furthermore, all numbers expressing dimensions, physical characteristics, processing parameters, amounts of ingredients, reaction conditions and the like used in the description and in the claims are to be understood as being modified in all cases by the term approximately. Accordingly, unless otherwise indicated, the numerical values ​​set forth in the following description and in the claims are approximations that may vary depending on the desired properties to be obtained by the present invention. At least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical value should be considered at least in light of the number of significant digits given and applying ordinary rounding techniques.

Furthermore, it must be considered that all the ranges described here cover each and every one of the sub-ranges subsumed within them. For example, an established range of 1 to 10 should be considered to include each and every one of the sub-ranges between (inclusive) the minimum value of 1 and the maximum value of 10, that is, all sub-ranges that start with a value minimum of 1 or more and ending with a maximum value of 10 or less, for example 5.5 to 10. Furthermore, as used herein, the terms deposited on or provided with mean deposited or provided with, but not necessarily in contact with the surface of. For example, a coating deposited on a substrate does not exclude the presence of one or more different coating films of the same or a different composition located between the deposited coating and the substrate. Additionally, all percentages described herein are by weight, unless otherwise indicated. All the photocatalytic activity values ​​discussed here are determined by the conventional stearic acid test described in the Patent

USA No. 6.027.7S6, incorporated herein by reference. All root mean square roughness values ​​are those determined by atomic force microscopy by measuring the root mean square (MC) over a surface area of ​​one square micrometer. Additionally, any reference to which mention is made here as incorporated as a reference is to be understood as incorporated in its entirety.

[0025] Referring now to Fig. 1, an article 20 is shown having features of the present invention. Article 20 includes a substrate 22 having a surface 21 with a photoinduced hydrophilic coating (hereinafter HF) 24 of the invention deposited on at least a portion of surface 21. As used herein, the term photoinducible hydrophilic coating refers to a material or coating that is photoactively hydrophilic. By photoactively hydrophilic is meant a coating for which the contact angle of a water droplet on the surface of the coating decreases with time as a result of exposing the coating to electromagnetic radiation. For example, the contact angle can decrease to a value less than 15 °, such as less than 10 °, and can be made super hydrophilic; for example, it decreases to less than or equal to 5 °, for example less than or equal to

4 °, for example less than or equal to 35 ° after sixty minutes of exposure to ultraviolet radiation from a light source sold under the trade name UVA

340, from the Q-Pansi Company of Cleveland, Ohio, positioned to have an intensity of 24 W / m2 on the surface of the HF coating. The contact angle can drop further, for example to less than or equal to 2 °, for example to less than or equal to

1 °, after greater exposure to the light source or after exposure to different light sources and / or different lighting intensities.

[0026] Although not considered as limiting the invention, the HF coating of the invention is believed to be photoactive or to behave photoactively. As one skilled in the art will appreciate, the terms "photoactive" or "photoactively" refer to the photogeneration of a hollow electron pair when illuminated by radiation of a particular frequency. Exemplary photoactive materials useful in practicing the invention include semiconductor metal oxides. Although photoactively hydrophilic, coating 24 may not necessarily be photocatalytic to be self-cleaning, that is, it may not be photocatalytic enough to decompose organic materials, such as grime, on the surface of the coating.

[0027] In the broad practice of the invention, the substrate 22 can be of any desired material having any desired optical characteristics. For example, the substrate 22 may be transparent to visible light. By "transparent" is meant that it has a transmittance through substrate 22 of from more than 0% to 100%. Visible light means electromagnetic energy in the range of 395 nm to 800 nm. Alternatively, the substrate 22 can be translucent or opaque. By translucent is meant that it allows electromagnetic energy (eg visible light) to pass through, but diffuses it in such a way that objects on the other side are not clearly visible. By opaque is meant that it has a transmittance of visible light of 0%. Suitable materials for substrate 22 include plastic (eg, methyl polymethacrylate, polycarbonate, polyurethane, ethylene polyterephthalate (PET), or copolymers of any monomer for their preparation, or mixtures thereof), ceramic, or glass. The glass can be of any type, such as conventional float glass or flat glass, and can be of any composition having any optical properties, for example any visible transmission value, ultraviolet transmission, infrared transmission and / or energy transmission total solar. By float glass is meant glass formed by a conventional flotation process wherein molten glass is deposited on a molten metal bath and cooled in a controllable manner to form a float glass strip. The web is then cut and / or shaped and / or heat treated as desired. Examples of float glass procedures are described in US Pat.

Nos. 4,466,562 and 4,671,155. The glass may be, for example, conventional soda-lime-silicate glass, borosili19 cato glass or leaded glass. The glass may be clear glass, that is, untinted or uncolored glass. Alternatively, the glass may be tinted glass or some other colored glass. The glass can be non-tempered, heat treated, or heat reinforced glass. As used herein, the term "heat reinforced" means annealed, tempered, or at least partially tempered. Although not limiting of the invention, examples of glass suitable for substrate 12 are described in US Pat. No. 4,746,347,

4,792,536, 5,240,886, 5,385,872 and 5,393,593, which are incorporated herein by reference. The substrate 22 may be of any desired dimension, eg, length, width, shape, or thickness. For example, the substrate 22 may be a glass pane from an architectural sale, a skylight, a pane from an insulating glass unit, or a sheet for a conventional side or rear windshield or window for vehicles, a sunroof, or a transparency for airplanes, to name just a few.

[0028] The HF coating 24 can be deposited directly on, ie in contact with, the surface 21 of the substrate 22 as shown in Fig. 1. It has been found that even with a sodium containing substrate, such Like soda-lime-silica glass, the very thin HF coatings of the invention are not rendered non-hydrophilic by the sodium in the substrate when the coating is applied by the bath method described below. Therefore, an easier to clean soda-lime-silica glass can be produced without a sodium barrier layer between the glass and the HF coating of the invention. Eventually, such a barrier layer could be used.

[0029] Alternatively, one or more different layers or coatings, for example one or more functional coatings (eg, an anti-reflective coating) or sodium ion diffusion barrier layers may be interposed as described below between the HF 24 coating. and substrate 22. For example, the HF coating 24 may be an outer or outermost layer of a stack of multiple layers of coatings present on substrate 22, or the HF coating 24 may be embedded as one of the layers other than the outermost layer in said multi-layer stack. By an outer layer, is meant a layer that receives enough excitatory electromagnetic radiation, for example ultraviolet radiation, to provide the coating with enough photoactivity to be photoactively hydrophilic, but not necessarily photocatalytic. Preferably, the HF 24 coating is the most extreme coating on substrate 22.

[0030] As previously stated, the coating

HF 24 need not have a level of photocatalytic activity on the order of previously known self-cleaning coatings. For example, the HF 24 coating may have photocatalytic activity in the range of greater than or equal to 0 cm1 min-1 to less than or equal to 5 x 10-3 cm-1 min-1 ± 2 x 10-3 cm-1 min -1, for example less than or equal to 4 x 10-3 cm-1 min-1, for example less than or equal to 3 x 10-3 cm-1 min-1 ± 2 x 10-3 cm-1 min-1 , such as less than or equal to 2 x 10-3 cm-1 min-1 + 2 x

10-3 cm-1 min-1.

[0031] The HF 24 coating can include any coating material that is photoactively hydrophilic and that can be deposited by the DQV method, the spray pyrolysis method or the DVBM method. For example, but without limiting the invention, the HF coating 24 may include one or more metal oxides, metal alloy oxides or metal oxides or semiconductor metal alloy oxides, such as, without limitation, titanium oxides, silicon oxides, oxides Aluminum, Iron Oxides, Silver Oxides, Cobalt Oxides, Chromium Oxides, Copper Oxides, Molybdenum Oxides, Tungsten Oxides, Zinc Oxides, Oxides of Zinc / Tin Alloys, Zinc Stannates, strontium titanate and mixtures and combinations thereof. Metal oxides and / or oxides of metal alloys can include metal oxides, superoxides, or suboxides.

[0032] An exemplary HF 24 coating particularly useful in practicing the invention is titanium dioxide.

Titanium dioxide exists in an amorphous form and three crystalline forms, namely the anatase, rutile, and brookite crystal forms. Anatase phase titanium dioxide exhibits strong photoactive hydrophilicity, while also possessing excellent resistance to chemical attack and excellent physical resistance. The rutile phase of titanium dioxide can also exhibit photoactive hydrophilicity. Mixtures or combinations of the anatase and / or rutile and / or brookite and / or amorphous phases are acceptable for the present invention, provided that the combination exhibits photoactive hydrophilicity.

[0033] The HF 24 coating should be thick enough to give an acceptable level of photoactive hydrophilicity. There is no absolute value that makes the HF coating 24 acceptable or unacceptable, as the HF coating having an acceptable level of photoactive hydrophilicity varies greatly depending on the purpose and conditions in which the article is being used. HF coated and selected performance standards to meet that end. However, as stated above, the thickness of the HF 24 coating to achieve photoactive hydrophilicity may be much less than is necessary to achieve a conventional commercially acceptable level of self-cleaning photocatalytic activity. For example, the HF 24 coating may have a thickness in the range of 10A to 5,000A, where the thicker coatings in this range may have photocatalytic self-cleaning activity as well as hydrophilicity. As coatings get thinner in this range, photocatalytic self-cleaning activity typically decreases. As the thickness of the coating decreases in ranges such as 50 Á to 3,000 Á, for example 100 Á to 1,000 Á, for example 200 Á to 500 Á, for example 200 Á to 300 Á, the photocatalytic self-cleaning activity can be immeasurable, but hydrophilicity is still present in the presence of selected electromagnetic radiation. It has been found that, when the substrate 22 is a float glass piece and the HF coating 24 has some anatase titanium dioxide HF coating formed directly on the float glass piece by the DQV method, a thickness of 200 Á at 300 Á provides a photocatalytic activity in the range of 0 to 2 x 10-3 cm-1 min-1 ± 2 x 10-3 cm-1 min-1, for example 1.8 x 10-3 cm-1 min24 to 2.8 χ 10-3 cm-1 min-1, for removal a stearic acid test film when exposed to ultraviolet radiation from a UVA-340 light source having an intensity of 24 W / m2 on the surface of the HF coating. This HF coating was also super hydrophilic under this same radiation and had a water droplet contact angle in the range of 4 ° + 2 ° to 7 ° + 2 ° after 60 min of exposure to the UVA-340 light source. As will be appreciated by one skilled in the art, the coating may not be uniformly thick throughout its entire area. Therefore, the thickness values ​​discussed here are to be considered average thicknesses throughout the coating.

[0034] In another aspect of the invention, the external surface of the HF 24 coating of the invention can be much smoother than previous hydrophilic self-cleaning coatings, while maintaining its photoactive hydrophilicity. For example, the liner 24, particularly the top or outer surface part of the liner, may have a roughness MC in the range of greater than or equal to 0 nm to less than or equal to 5 nm, even for thin coatings in the above ranges, such as 200 Á to 300 Á, for example less than or equal to 4.9 nm, for example less than or equal to 4 nm, for example less than or equal to 3 nm, for example, less than or equal to 2 nm, for example less or equal to 1 nm, for example from 0.3 nm to 0.7 nm. For example, the 200A to 300A HF coating just quoted had a surface roughness MC of 0.55nm to 0.65nm, as measured by atomic force microscopy.

[0035] In another aspect of the invention, the coating

HF 24 can have low reflectance in visible light. As used herein, reflectance to visible light refers to the conventional denomination of chromaticity coordinates (Rl) Y (Illuminator C, 2 degree observer). For example, the HF coated article may have a reflectance to visible light in the range of 10% to 25%, for example 15% to

25%, for example from 19% to 24%, for example from 15% to 22%, for example less than or equal to 25%, for example less than or equal to 23%, for example less than or equal to 20%.

[0036] In yet another aspect of the invention, the HF 24 coating may be denser than previous hydrophilic self-cleaning coatings. For example, the HF 24 coating can be substantially non-porous. By substantially non-porous, it is meant that the coating is dense enough that the coating can withstand a conventional hydrofluoric acid drop test. In the drop test, two (2) drops of a 0.5 volume percent (% vol.) Aqueous solution of hydrofluoric acid (HF) are placed on a coated sample and a laboratory watch glass is placed Conventional on the sample for 8 minutes (min) at room temperature. After 8 minutes, the watch glass is removed and the coating is inspected for damage. The denser HF 24 coatings of the invention provide greater protection to the underlying substrate from chemical attack than the more porous previous self-cleaning coatings and are also harder and more scratch resistant than previous self-cleaning coatings applied in solgei.

[0037] According to the present invention, an HF coating can be formed having a thickness in the range of 10A to

500 Á, such as less than or equal to 400 A, for example from 200 Á to

300 Á, on substrate 22 by any one or more between spray pyrolysis, DQV or DVBM. In the spray pyrolysis method, an organic or metal-containing precursor is transported in an aqueous suspension, for example an aqueous solution, and in the DQV method, it is transported in a gaseous vehicle, for example nitrogen gas, and is directed toward the surface of substrate 22 while substrate 22 is at a temperature high enough to cause the precursor to decompose and form an HF coating 24 on substrate 22. In the DVBM method, a metal-containing cathode target is bombarded under negative pressure in an inert or oxygen-containing atmosphere to deposit a bombarded coating on the substrate 22.

Substrate 22 can be heated during or after coating to cause crystallization of the bombarded coating to form HF 24 coating. Conventional methods of spray pyrolysis, DQV and DVBM will be well understood by someone of ordinary skill in the art and, by they will not be described in detail here.

[0038] Each of the methods has advantages and limitations depending on the desired characteristics of the coating 24 and the type of glass manufacturing process. For example, in a conventional float glass process glass is poured onto a pool of molten metal, for example tin, in a molten metal bath (tin) to form a continuous band of float glass. The temperatures of the float glass strip in the tin bath generally vary between 1,203 ° C (2,200 ° F) at the inlet end of the bath and 592 ° C (1,100 ° F) at the outlet end of the bath. The float glass strip is removed from the tin bath and tempered, ie cooled in a controllable manner, in an annealing tunnel before being cut into sheets of glass of the desired length and width. The temperature of the float glass strip between the tin bath and the annealing tunnel may be in the range of 480 ° C (896 ° F) to 580 ° C (1,076 ° F) and the temperature of the glass strip float in the annealing tunnel may be in the range of 204 ° C (400 ° F) to a peak of 557 ° C (1,035 ° F). US Patents Nos. 4,466,562 and 4,671,155 (incorporated herein by reference) provide a discussion of the float glass process.

[0039] DQV and spray pyrolysis methods may be preferred to the DVBM method in a float glass procedure, as they are more compatible with coating continuous substrates, such as float glass strips, at elevated temperatures. Examples of DQV coating and spray pyrolysis methods are described in US Pat. No. 4,344,986, 4,393,095,

4,400,412, 4,719,126, 4,853,257 and 4,971,843, the patents of which are hereby incorporated by reference.

[0040] In practicing the invention, one or more DQV coating apparatus can be employed at various points in the float glass web manufacturing process.

For example, a coating apparatus can be used for

DQV when the float glass strip travels through the tin bath, after it leaves the tin bath, before it enters the annealing tunnel, when traveling through the annealing tunnel, or after it leaves the tunnel annealing. Since the DQV method can coat a moving float glass strip and still withstand the harsh conditions associated with the manufacture of the float glass strip, the DQV method is particularly suitable for obtaining the HF 24 coating on the glass float band. float in the molten tin bath. US Patents No.

4,853,257, 4,971,843, 5,536,718, 5,464,657 and 5,599,387, incorporated herein by reference, describe a DQV coating apparatus and methods that can be used in practicing the invention to coat a glass strip flotation in a molten tin bath.

[0041] For example, as shown in fig. 2, one or more DQV coaters 50 can be located in the tin bath 52 above the molten tin pool 54. As the float glass strip 56 moves through the tin bath 52, the precursor materials they are directed to the upper surface of band 56. The precursor materials decompose to form an HF coating of the invention that has photoactive hydrophilic activity. For example, precursor materials can be selected to decompose and form semiconductor metal oxides, for example crystalline metal oxides. Examples of precursor materials that can be used in the practice of the present invention to form HF coatings of titanium oxide by the DQV method include, but are not limited to, titanium tetrachloride (TIC14), titanium tetraisopropoxide (Ti (OC3H7) ) 4) (hereinafter TTIP), titanium tetrabutoxide, titanium tetraethoxide (Ti (OC2H5) 4) (hereinafter,

TTet) and its mixtures. Examples of carrier gases that can be used in the DQV method include, but are not limited to, air, nitrogen, oxygen, ammonia, and mixtures thereof. The concentration of the metal-containing precursor in the carrier gas can be from 0.01% to 0.4% by volume (% vol.), For example 0.05% vol. at 0.4 vol%, for example 0.05 vol%. at 2% vol., for example 0.05% vol. at 1% vol. for the metal-containing precursors listed above, but, as will be appreciated by those skilled in the art, these concentrations may vary for other metal-containing precursors.

[0 042] For the DQV method (as well as for the spray pyrolysis method discussed below), the temperature of the substrate 22 (such as a float glass strip 56) during formation of the HF 24 coating thereon must be within a range that causes the metal-containing precursor material to decompose and form a coating that has photoactive hydrophilic activity.

The lower limit of this temperature range is greatly affected by the decomposition temperature of the selected metal-containing precursor. For the aforementioned titanium containing precursors, the lower temperature limit of the substrate 22 to obtain sufficient decomposition of the precursor may be in the range of 400 ° C (752 ° F) to 500 ° C (932 ° F). The upper limit of this temperature range may be affected by the method of coating the substrate. For example, when the substrate 22 is a float glass strip 56 and the HF coating 24 is applied to the float glass strip 56 in the molten tin bath 50 during the manufacture of the float glass strip 56, the 56 float glass strip can reach temperatures above 1,000 ° C (1,832 ° F). The float glass strip 56 can be tempered or resized (eg stretched or compressed) at temperatures above 1,472 ° F (800 ° C). If the HF coating 24 is applied to the float glass strip 56 before or during dimming, the HF coating may crack or wrinkle by stretching or compressing the float glass strip 56, respectively. Therefore, the HF coating can be applied when the float glass strip 56 is dimensionally stable (except for thermal shrinkage with cooling), for example below 800 ° C (1,472 ° F) for soda glass. calsilica, and the float glass strip 56 is at a temperature that decomposes the metal-containing precursor, for example above 752 ° F (400 ° C).

[0043] For spray pyrolysis, Patents

USA Nos. 4,719,126, 4,719,127, 4,111,150, and 3,660,061, incorporated herein by reference, describe spray pyrolysis apparatus and methods that can be employed in a conventional method of manufacturing float glass strips. While the spray pyrolysis method, like the DQV method, is suitable for coating a moving float glass strip, spray pyrolysis requires more complex equipment than equipment.

DQV and is normally used between the end of the tin bath outlet and the end of the annealing tunnel inlet.

[0044] Examples of metal-containing precursors that can be used in the practice of the invention to form HF coatings by the spray pyrolysis method include relatively water-insoluble organometallic reagents, which are jet-ground or wet-milled to a particle size less than 10 microns and suspended in an aqueous medium using a chemical wetting agent. A suitable metal acetylacetonate to form a titanium dioxide HF coating is titanyl acetylacetonate (TiO (C5H7O2) 2). The relative concentration of the metal acetylacetonate in the aqueous suspension preferably ranges from 5 to 40 weight percent of the aqueous suspension. The wetting agent can be any relatively low foaming surfactant, including anionic, nonionic or cationic compositions, although nonionic ones are preferred. The wetting agent is typically added to a

0.24% by weight, but may range from 0.01% to 1% or more. The aqueous medium is preferably distilled or deionized water. Aqueous suspensions for the pyrolytic deposition of metal-containing films are described in US Pat. No. 4,719,127, particularly in column 2, line 16 to column 4, line 48, which is incorporated herein by reference.

[0045] As will be appreciated by those skilled in the art, the bottom surface of the float glass strip resting directly on the molten tin (commonly referred to as the tin side) has diffused tin on the surface, which it gives the tin side a tin absorption pattern different from the opposite surface, which is not in contact with the molten tin (commonly referred to as the air side).

The HF coating of the invention can be formed on the air side of the float glass strip while supported on the tin by the DQV method as described above, on the air side of the float glass strip when it leaves the tin bath by the DQV or spray pyrolysis methods and / or on the tin side of the float glass strip after it has left the tin bath by the DQV method.

[0046] With respect to DVBM, US Pat. No.

4.379.040, 4.861.669, 4.900.633, 4.920.006, 4.938.857,

5,328,768 and 5,492,750, hereby incorporated by reference, describe DVBM apparatus and methods for sputter coating metal oxide films onto a substrate, including a glass substrate. The DVBM procedure is generally not compatible with obtaining a coating

HF on a float glass strip during its manufacture, since, among other things, the DVBM re35 method wants negative pressure during the bombardment operation, which is difficult to form on a continuous moving float glass strip. However, the DVBM method is acceptable for depositing the HF coating 24 on the substrate 22, for example a glass sheet. The substrate can be heated to temperatures in the range of 400 ° C (752 ° F) to 500 ° C (932 ° F), such that the DVBM-bombarded coating on the substrate crystallizes during the deposition process, thereby eliminating an operation for subsequent cancellation. Heating of the substrate during bombardment may not be preferred in some cases, since additional heating operation during bombardment may reduce performance. Alternatively, the bombarded coating can crystallize within the DVBM coating apparatus directly and without heat post-treatment using a high energy plasma, but again due to its tendency to reduce performance through a DVBM coater, this is not a preferred method.

[0047] An example of a method for obtaining a 0 to HF coating (especially an HF coating of 3 00 Á or less and having a MC roughness of 2 nm or less) using the method

DVBM is to bombard a coating on the substrate, remove the coated substrate from the DVBM coater, and then heat treat the coated substrate to crystallize the bombarded coating on the HF 24 coating.

For example, although without limitation, a titanium metal target can be bombarded in an argon / oxygen atmosphere that has 5-50%, for example 20%, oxygen at a pressure of 5-10 millitorr to deposit by I spray a titanium dioxide coating of the desired thickness on the substrate 22. The deposited coating does not crystallize. The coated substrate is removed from the coater and heated to a temperature of 400 ° C (752 ° F) to 600 ° C (1,112 ° F) for a period of time sufficient to promote the formation of the crystalline form HF of titanium dioxide. to get HF activity. For example, the coated substrate can be heated for at least one hour to a temperature of 400 ° C (752 ° F) to 600 ° C (1,112 ° F). When the substrate 22 is a glass sheet cut from a float glass strip, the HF coating 24 can be sprayed onto the air side and / or the tin side.

[0048] The substrate 22 having the HF coating 24 deposited by the DQV, spray pyrolysis, or DVBM methods may then be subjected to one or more HF postcoat annealing operations. As can be appreciated, annealing time and temperatures can be affected by various factors, including the composition of substrate 22, the composition of the HF coating

24, the thickness of the coating HF 24 and whether the coating

HF 24 is directly in contact with substrate 22 or is a layer of a multi-layer stack on the substrate.

[0049] Whether the HF coating is obtained by the DQV procedure, by the spray pyrolysis procedure or by the DVBM procedure, where substrate 22 includes sodium ions that can migrate from substrate 22 to the HF coating deposited on substrate 22, sodium ions can inhibit or destroy the photoactive hydrophilicity of the HF coating by forming inactive compounds while consuming titanium, for example forming sodium titanates or causing recombination of photoexcited charges. Therefore, a diffusion barrier layer for sodium ions (BDIS) can be deposited on the substrate prior to deposition of the HF 24 coating. A suitable BDIS layer is discussed in detail in US Pat. No. 6,027,766, incorporated herein by reference, and will not be discussed in detail here. With postcoating heating, it may be preferred to have a sodium bar layer containing substrates, such as soda-lime-silica glass. To apply the HF coating of the invention in a molten metal bath, the sodium barrier layer is optional.

[0050] The HF coatings of the present invention are preferably photoactively hydrophilic upon exposure to radiation in the ultraviolet range, for example from

300 nm to 395 nm, of the electromagnetic spectrum. Ultraviolet radiation sources include natural sources, for example solar radiation, and artificial sources, such as a black light or ultraviolet light source, such as the UVA-340 light source described above.

[0051] As shown in Fig. 1, in addition to the HF coating 24 of the invention, one or more additional coatings, such as functional coatings 46 (as described below), may be deposited on substrate 22. For example, a functional coating 46 may be deposited on a larger surface 60 of the substrate opposite surface 21. Functional coating 46 can be deposited by any conventional method, such as, but not limited to, spray pyrolysis,

DQV, DVBM, sol-gel, etc. For example, US Pat. No.

4,584,206 and 4,900,110, incorporated herein by reference, describe methods and apparatus for depositing a metal-containing film on the underside of a glass strip by chemical vapor deposition. Said known apparatus can be located downstream of the molten tin bath in the float glass process to obtain a functional coating on the underside of the glass strip, that is, the side opposite to the HF coating of the invention. Alternatively, one or more different DQV coaters can be located in the tin bath to deposit a functional coating above or below the HF 24 coating on the float glass strip.

[0052] An example of an article of manufacture of the invention is shown in Fig. 3 in the form of insulating glass (VA) unit 30. The insulating glass unit has a first pane 32 separated from a second pane 34 by a spacer mount (not shown) and held in place by a sealing system to form a chamber between the two panes 32, 34. The first pane 32 has a first surface 36 (surface number 1) and a second surface 38 (surface number 2). The second crystal 34 has a first surface 40 (surface number 3) and a second surface 42 (surface number 4). The first surface 36 can be the exterior surface of the VA unit, that is, the surface exposed to the environment, and the second surface 42 can be the interior surface, that is, the surface that forms the interior of the structure. Examples of VA units are described in US Pat. No. 4,193,236, 4,464,874,

5,088,258 and 5,106,663, incorporated herein by reference. As shown in Fig. 3, the HF 24 coating is preferably located on either the number 1 or number 4 surfaces, preferably on the number 1 surface. The HF 24 coating reduces fogging and causes unit

VA 30 is easier to clean and maintain.

[0053] One or more coatings can be deposited with eventual donations 46 on at least a portion of surfaces number 2, number 3 or number 4. As used herein, the term "functional coating" refers to a coating that modifies one or more physical properties of the substrate on which it is deposited, for example optical, thermal, chemical or mechanical properties, and its separation from the substrate during subsequent processing is intended. Functional coating 46 may have one or more functional coating films of the same or different composition or functionality. As used herein, the terms layer or film refer to a coating region of a selected or desired coating composition.

The film may be homogeneous, nonhomogeneous, or have a gradual compositional change. A film is homogeneous when the outer surface or portion (i.e., the surface or portion furthest from the substrate), the inner surface or portion (i.e., the surface or portion closest to the substrate) and the portion between the outer surfaces and internally they have substantially the same composition. A film is gradual when the film has a substantially increasing fraction of one or more components and a substantially decreasing fraction of one or more different components when moving from the inner surface to the outer surface or vice versa. A film is nonhomogeneous when the film is neither homogeneous nor gradual. A coating is made up of one or more films.

[0054] Functional coating 46 may be an electrically conductive coating, such as, for example, an electrically conductive window covering as described in US Pat. No. 5,653,903 and

5.02 8.759, or a single or multi-film coating capable of functioning as an antenna. Similarly, functional coating 46 may be a coating for solar control, for example a reflective or absorbing coating for visible, infrared, or ultraviolet energy. Examples of coatings suitable for solar control are found in US Pat. H °

4.898.789, 5.821.001, 4.716.086, 4.610.771, 4.902.580,

4.716.086, 4.806.220, 4.898.790, 4.834.857, 4.948.677,

5,059,295 and 5,028,759 and also in the Patent Application

USA No. 09 / 058,440. Similarly, functional coating 46 may be a low-emissivity coating. Low-emissivity coatings allow energy of visible wavelength to be transmitted, for example from 400nm to

780 nm, through the cladding, but reflect solar infrared energy and / or thermal infrared energy of greater wavelength and typically aim to improve the thermal insulation properties of architectural glazing.

By low emissivity is meant emissivity less than 0.4, preferably less than 0.3, more preferably less than

0.2. Examples of low emissivity coatings can be found, for example, in US Pat. Nos. 4,952,423 and 4,504,109 and in British reference GB 2,302,102. Functional coating 46 can be a single-layer or multi-layer coating and can include one or more metals, nonmetals, semimetals, semiconductors and / or alloys, compounds, combinations or mixtures thereof. For example, functional coating 46 may be a single-layer metal oxide coating, a multi-layer metal oxide coating, a non-metallic oxide coating, or a multi-layer coating. Additionally, the functional coating may be an anti-reflective coating.

[0055] Examples of functional coatings suitable for use in the invention are marketed by PPG Industries, Inc., of Pittsburgh, Pennsylvania, under the SUNGATE ™ and SOLARÍAN® coating families. Such functional coatings typically include one or more anti-reflective coating films consisting of dielectric or anti-reflective materials, such as metal oxides or metal alloy oxides, which are preferably transparent or substantially transparent to visible light. Functional coating 46 may also include infrared reflective films containing a reflective metal, for example a noble metal, such as gold, copper, or silver, or combinations or alloys thereof, and may also include a primer film or barrier film, such as titanium, as is known in the art, located on and / or below the metallic reflective layer.

[0056] Functional coating 46 can be deposited in any conventional manner, such as, but not limited to, magnetron bombardment vapor deposition (DVBM), chemical vapor deposition (DQV), spray pyrolysis (ie, pyrolytic deposition ), Atmospheric pressure DQV (DQVPA), low pressure DQV (DQVBP), plasma-enhanced DQV (DQVIP), plasma-assisted DQV (DQVAP), thermal or electron beam evaporation, cathodic arc position, plasma spray deposition and wet chemical deposition (eg, sol-gel, mirror plating, etc.). When applying the functional coating to the side of the HF coating of the substrate, it is preferred to apply the functional coating in the tin bath before the HF coating. When the functional coating is on the opposite side 60 of the HF coating, the functional coating can be applied after the tin bath in the flotation process discussed above, for example on the tin side of the substrate 22 by DQV or

DVBM.

[0057] Although in the previous discussion the HF coating was applied on the air side of the substrate and the functional coating was applied on the tin side of the substrate, it is to be understood that the functional coating could be applied on the air side of the substrate, for example the float glass strip in the tin bath, and that the HF coating could then be applied to the tin side of the substrate by any desired method, such as those described above.

[0058] The advantages of the present invention over the sol-gel method of forming self-cleaning coatings include the ability to form a thin and dense HF film of a substrate over the generally thicker and more porous self-cleaning coatings obtained with the method of sol-gel coating. Since the HF coatings of the present invention are thin, for example less than or equal to 500 A, preferably less than or equal to 3 00 Á, they are aesthetically acceptable for use as a transparent coating on glass substrates. Still another advantage is that the method of obtaining an HF coating according to the present invention avoids the need to reheat the substrate after application of the coating or the coating precursor, as required with the currently available sol-gel method . This not only makes the present method less costly and more effective, for example, but without limitation, lower equipment costs, lower energy costs, less production time, but also reduces the opportunity for ion migration. sodium and, in turn, sodium ion poisoning of the HF coating of the present invention. Furthermore, the method of the present invention is easily adapted to the formation of PASC coatings on continuously moving substrates, such as a float glass strip, where currently available sol-gel methods are not readily adaptable.

The following example of the present invention is presented for illustrative purposes and the invention is not limited thereto.

EXAMPLE [0060] A 48 (122 cm) wide HF coating of titanium dioxide, having a thickness of 232A (determined by ellipsometry and transmittance data) was deposited by a conventional DQV procedure on a glass strip 152 (385 cm) float (3.3 mm thick clear glass) moving at a speed of 484 inches per minute (1,229 cm / min) in a conventional tin bath. The coating was formed from a 0.07 mole percent titanium tetraisopropoxide precursor material in a nitrogen-containing barrier gas and applied at a glass band temperature of 1,220 ° F (659 ° C).

The coated web was then annealed, ie, cooled at a controlled rate, and cut into sample coupons (7.5 cm) by 6 (15 cm). The crystalline structure of the deposited coating was determined to be anatase by di47 x-ray fraction. The coating had a photocatalytic activity of 1.8 x 10-3 cm-1 min-1, as determined by the conventional stearic acid test and the chromaticity coordinates (Illuminator C, observer 2) of: reflectance (Rl) Y = 19.43, x = 0.2741, y = 0.2774, and transmittance Y = 78.50, x = 0.3187, y = 0.3279.

[0061] To measure the photoactive hydrophilicity of the coated article, sample coupons were ultrasonically cleaned for 20 minutes at 145 ° F with a dilute aqueous cleaning solution (pH 2.9) of DART 210 cleaner, available from Madison Chemical Inc., from Madison, Indiana. The sample coupons were then rinsed with deionized water at room temperature, followed by a second ultrasonic cleaning in deionized water for 10 minutes at 155 ° F.

The coupons were rinsed again with deionized water at room temperature and blown dry with compressed nitrogen. The coupons were exposed to UV radiation from a 340 UVA lamp at 24 W / m2 and the contact angle of a water droplet was measured with time. The contact angles of the water droplets were measured on a Rame-Hart Telegoniometer, Model 102-00-115, with the sample in a horizontal position (not inclined). For each sample measured, the contact angle of the water droplet dropped from approximately 21 ° to 47 ° to approximately 4 ° to 11 ° after approximately 30 min of UVA-340 exposure, and to approximately 3 ° to 7 ° after approximately 60 min of exposure.

[0062] A Taber abrasion test was performed on various sample coupons using a CS-10F wheel weighing 1,000 grams for 10 cycles and 25 cycles. The transmitted turbidity for each sample was determined to be 0.0 using a Pacific Scientific HazeGuard XL211 System. A Taber abrasion test was also performed on five sample coupons according to Test No. 18 of the ANSI Z procedure

26.1-1983 (1,000 cycles, 500 grams per wheel) for abrasion resistance and an average increase in stray light of 2.4% was obtained.

[0063] Sample coupons were subjected to various standard test procedures and the results are given in Table 1 below. The results of film degradation are based on visual observation and measurements of reflected color. The results of the contact angles were determined as previously described.

<td colspan="4">Table 1</td>

<td>Proof</td><td>Description</td><td>Film degradation</td><td>Angle of Contact</td>

<td>Condensation Cleveland</td><td>70 days, 100% RH, 60 ° C (140 ° F)</td><td>None</td><td>Without changes</td>

<td>Sulfuric acid</td><td>30 min, 10 N sulfuric acid, 52 ° C (125 ° F)</td><td>None</td><td>Without changes</td>

<td>Citric acid</td><td>15 min, 10% citric acid, 26 ° C (79 ° F)</td><td>None</td><td>Without changes</td>

<td>Hydroxide ammonium</td><td>1 min, hydroxide ammonia 4%, 23 ° C (74 ° F)</td><td>None</td><td>Without changes</td>

<td>Meter of arc atmospheric conditions carbon</td><td>1,000 h, cycle 7 (102 min. Light, 18 min. light and spray. Water)</td><td>None</td><td>Without changes</td>

<td>Accelerated atmospheric cycle test</td><td>ASTM E-773 (5 weeks)</td><td>None</td><td>Without changes</td>

[0064] As shown in Table 1, the HF coating had no film degradation and maintained its photoinduced hydrophilicity after each test.

[0065]

Those skilled in the art will readily appreciate that modifications can be made to the invention without departing from the concepts set forth in the foregoing description. Accordingly, the particular embodiments described in detail herein are illustrative only and do not limit the scope of the invention, which is to be given in its entirety by the appended claims and each and every one of their equivalents.