JP5991794B2 - Light-induced hydrophilic article and method for producing the same - Google Patents

Description

  The present invention relates to a method of depositing a hydrophilic coating on a substrate (eg, a glass sheet or continuous float glass strip) and an article of manufacture made by the method.

REFERENCE RELATED APPLICATION This application is a provisional U.S. patent application serial no. No. 60 / 040,566, filed July 23, 1997, US Patent Application Serial No. No. 08 / 899,257 (current US Pat. No. 6,027,766), filed on April 1, 1999, “Photocatalytically-Activated Self- US Patent Application Serial No. by Greenberg et al. Entitled Cleaning Appliances). 09 / 282,943. These applications are all incorporated herein by reference in their entirety. This application is a provisional US entitled “Photo-Induced Hydrophilic Article and Method of Making Same” filed on February 28, 2001, which is incorporated herein by reference in its entirety. Patent application Serial No. Claims the right of 60 / 272,197.

  The following discussion discusses general technical considerations related to the present invention. However, the specific documents discussed here should not be considered as constituting "prior art" in US patent law and are not accepted.

  For many materials, such as glass substrates such as architectural windows, automotive transparencys, and aircraft windows, the surface of the substrate can substantially form surface contaminants such as common organic and inorganic surface contaminants. It is desirable for good visibility not to have a long time only. Traditionally, this has often meant cleaning these surfaces. This cleaning operation is typically performed by manually wiping the surface with or without the aid of a chemical cleaning solution. This method is labor intensive, time consuming and / or costly. Accordingly, there is a need for a substrate, particularly a glass substrate, that is easier to clean than existing glass substrates and has a surface that reduces the need or frequency of such manual cleaning operations.

  Certain semiconducting metal oxides are self-cleaning coatings that are activated by photocatalysts (hereinafter referred to as “PA”) when incorporated into the coating, ie, on the coating surface when exposed to certain electromagnetic waves. It is known to provide a coating that interacts with and degrades or degrades these organic contaminants. Bibliographies of patents and articles on photocatalytic oxidation of organic compounds in general are Blake, “Bibliography of Work On The Photocatalytic Removal of Hazardous Compounds from Water and Air, National Renewable Energy Laboratory (May 1994), October 1995. Renewal and October 1996 update are reported.

Typically, these PA coatings are made thick enough to have sufficient photocatalytic activity to disintegrate or decompose organic contaminants on the coating in as short a time as possible. For example, WO 00/75087 describes a coating activated by a photocatalyst having a photocatalytic activity of at least 5 × 10 ⁻³ cm ⁻¹ min− ¹ . Still other PA coatings are described, for example, in US Pat. Nos. 5,873,203, 6,027,766, and 6,054,227.

  In addition to their self-cleaning properties, these PA coatings typically also have hydrophilicity, i.e. water wettability. The hydrophilicity of the PA coating is cloudy, i.e. helps to reduce the accumulation of water droplets on the coating. The accumulation of water droplets can reduce the transmission and visibility of visible light through the coated substrate. So far this hydrophilicity has been accompanied by several factors, among which are increased surface roughness (皺) and increased porosity of the coated surface. For example, US Pat. No. 6,103,363 discloses hydrophilic photocatalytic activity having a preferred root mean square (RMS) surface roughness of 5 nm to 15 nm and a preferred porosity of 70% to 90%. A self-cleaning coating is described. However, this degree of surface roughness can make the surface more difficult to clean, for example, by providing small pits that accumulate dirt and dirt, or from cleaning cloths that have been rubbed over the surface. It can be more difficult due to fiber catching or tearing. In addition, increasing the porosity of the coating can provide a groove through which the underlying substrate can be chemically eroded.

  In order to achieve the desired levels of coating thickness, photocatalytic activity, surface roughness, and coating porosity described above, many PA self-cleaning coatings have been deposited by sol-gel methods. In a typical sol-gel process, an uncrystallized colloidal suspension is coated on a substrate at or near room temperature and then heated to form a crystallized coating. For example, US Pat. No. 6,013,372 discloses hydrophilic photocatalytic self-cleaning property formed by mixing photocatalyst particles in a metal oxide layer and applying the mixture to a substrate by a sol-gel method. A coating is described.

  However, conventional sol-gel processes are not economically or practically compatible with certain application conditions or substrates. For example, in conventional float glass production, the float glass strip in the molten metal bath is too hot to accept the sol due to evaporation of the solvent used in the sol or chemical reaction. Furthermore, the molten metal bath environment does not help a moving machine such as a spray device that is required to apply the sol. Thus, the sol must typically be applied after the float glass strip exits the molten metal bath and is cooled to approximately room temperature. The coated strip must then be reheated to a temperature sufficient to crystallize the coating. Such cooling and reheating operations require substantial capital input in terms of equipment, energy, and handling costs and significantly reduce manufacturing efficiency. In addition, reheating sodium-containing substrates such as soda, lime, and silica glass increases the opportunity to move sodium ions in the substrate toward the coating, which is a “sodium ion poisoning” of the deposited coating. Conventionally mentioned. The presence of these sodium ions can reduce or eliminate the photocatalytic activity of the self-cleaning coating. Furthermore, the sol-gel process typically results in thick coatings, eg, several microns thick, which can adversely affect the optical and / or aesthetic properties of the coated article. Typically, as the thickness of the PA self-cleaning coating increases, the light transmission and reflectance of the coating exceeds a series of minimum and maximum values due to optical interference effects. The color of the reflected and transmitted light of the coating varies due to these optical effects. Thus, a coating that is thick enough to provide the desired self-cleaning properties may have undesirable optical properties.

  Accordingly, it would be advantageous to provide a manufactured article having a coating, particularly a hydrophilic coating, and a method of manufacturing an article that reduces or eliminates at least some of those disadvantages.

The present invention relates to an article of manufacture comprising a substrate having at least one surface and a hydrophilic coating, in particular a light-induced hydrophilic coating (defined below) deposited over at least a portion of the surface. The coating is deposited by a method selected from chemical vapor deposition (hereinafter referred to as CVD), spray pyrolysis, and / or magnetron sputtered vacuum deposition (hereinafter referred to as MSVD). Can do. In one embodiment, the outer surface of the coating, for example the coating, is equal to or greater than 0 nm, equal to or less than 4 nm, for example equal to or less than 3 nm, for example equal to or greater than 2 nm. It has a root mean square roughness that is small, for example in the range equal to or less than 1 nm. It is particularly advantageous if the substrate is a float glass strip and the coating is deposited in a molten tin bath by CVD during the production of the float glass strip. In another particular embodiment of the invention, the light-induced hydrophilic coating is equal to or greater than 0 cm ⁻¹ min ⁻¹ and less than or equal to 3 × 10 ⁻³ cm ⁻¹ min ⁻¹ For example, it has a photocatalytic activity in a range equal to or less than 2 × 10 ⁻³ cm ⁻¹ min− ¹ . In another aspect of the invention, the substrate is a float glass strip located in a molten metal bath and the light-induced hydrophilic coating has a thickness in the range of greater than 0 mm and less than or equal to 500 mm. However, the light-induced hydrophilic coating is deposited in a molten metal bath by chemical vapor deposition. The invention also relates to a method of manufacturing such an article.

FIG. 1 is a cross-sectional view (not to scale) of a portion of a substrate having a light-induced hydrophilic coating of the present invention deposited thereon. FIG. 2 is a side view (not full scale) showing the coating process for applying the semiconductor metal oxide coating of the present invention to a glass strip in a molten metal bath for float glass production. FIG. 3 is a sectional side view (not to scale) of an insulating glass unit incorporating features of the present invention.

  Very thin semiconducting metal oxide coatings, for example, coatings to the extent of greater than 0 and less than or equal to 500 are thinner than coatings typically used to achieve photocatalytic self cleaning. It has been discovered quite unexpectedly that the photocatalytic activity of thin coatings maintains their hydrophilicity even when they are lower than the activity typically desired for self-cleaning coatings to degrade organic contaminants. That is, the photoactivity maintained by the thin semiconductor metal oxide coating may not be sufficient photoactivity to have a measurable or commercially acceptable photocatalytic self-cleaning activity, but the coating Has been found to be sufficient to be hydrophilic. This light-induced hydrophilicity reduces haze and / or makes the coated article easier to clean, e.g. makes it easier to wipe off dirt and / or water spots than uncoated articles. Furthermore, the light-induced hydrophilicity makes water thinner, speeds drying, and reduces water droplet spots. This is because water has no tendency to form droplets and leave spots. Dirt can also be more easily removed by simply rinsing the coating without manually wiping the coating. In addition, these very thin semiconductor metal oxide coatings are less prone to the undesirable optical problems associated with thicker photocatalytic self-cleaning coatings. It has also been unexpectedly discovered that these very thin semiconducting metal oxide coatings can be made much smoother and more dense than previously thought while still maintaining their light-induced hydrophilicity. One example of a suitable semiconductor metal oxide that can be used in the practice of the present invention is an oxide of titanium.

  In one aspect, the invention provides a light-induced hydrophilic semiconductor metal oxide such as a titanium dioxide coating deposited on at least one surface of a substrate over at least a portion of the surface by CVD, spray pyrolysis, or MSVD. A substrate having a coating is provided. The coating has a thickness in the range of greater than 0 mm, equal to or less than 500 mm, for example equal to or less than 400 mm, for example equal to or less than 300 mm, and the outer surface of the coating is In general, it can have an RMS roughness equal to or greater than 0 nm, equal to or smaller than 2 nm, for example 1.9 nm or less, for example 1 nm or less. In the case of the coating of the present invention having a thickness of about 200 mm or less, the coating surface can be made even less smooth, for example 5 nm or less, for example 4.9 nm or less, for example 4 nm or less, for example 3 nm or less, for example 2 nm or less. For example, it can have an RMS roughness of 1 nm or less. As a special embodiment, the substrate is a float glass strip (ribbon) located in a molten tin bath.

  In one embodiment, the present invention provides an article comprising a float glass strip having at least one surface and a light-induced hydrophilic coating directly deposited on at least a portion of the at least one surface. The light-induced hydrophilic coating can be deposited directly on a float glass strip in a molten metal bath.

  The present invention also provides an article comprising a substrate having at least one surface and a light-induced hydrophilic coating deposited over at least a portion of the at least one surface. The substrate may be a float glass strip located in the molten metal bath, the light-induced hydrophilic coating may have a thickness of 500 mm or less, and the light-induced hydrophilic coating is at least one by chemical vapor deposition in the molten metal bath. It can be deposited over the surface.

  The invention further provides an article comprising a substrate having at least one surface and a light-induced hydrophilic coating deposited over at least a portion of the at least one surface. The light-induced hydrophilic coating can be deposited by chemical vapor deposition at a temperature in the range of 500 ° C. to 1200 ° C., and the light-induced hydrophilic coating can have a thickness of 500 mm or less.

  A method is provided for forming a light-induced hydrophilic coating covering at least a portion of a substrate. The method provides a substrate having a first surface and a second surface, wherein at least one of the surfaces has tin diffused therein, chemical vapor deposition, spray pyrolysis, magnetron on at least one of the surfaces. Deposit a metal oxide precursor from the coating apparatus by a method selected from sputter vacuum deposition, and heat the substrate to a temperature sufficient to decompose the metal oxide precursor to obtain a root mean square roughness of 2 nm or less. Forming a light-induced hydrophilic coating having a thickness.

  Another method of forming a light-induced hydrophilic coating over at least a portion of a substrate is to provide a float glass strip in a molten metal bath and the metal directly from the coating apparatus by chemical vapor deposition on the top surface of the glass strip. Depositing an oxide precursor material and heating the glass strip to a temperature sufficient to decompose the metal oxide precursor material to form a light-induced hydrophilic coating.

  Yet another method of forming a light-induced hydrophilic coating over at least a portion of a substrate provides a substrate having at least one surface and a CVD coating of a metal oxide precursor material covering at least a portion of the at least one surface. Vapor deposition by apparatus and heating the substrate to a temperature in the range of 400 ° C. to 1200 ° C. to decompose the metal oxide precursor material to form a light-induced hydrophilic coating, Providing sufficient precursor material to have a thickness of 500 mm or less.

  The present invention also relates to an article formed by the method of the present invention.

"Inner", "outer", "above", "below", "top", "bottom" used here ”, Etc., relates to the present invention as shown in the drawings. However, it will be understood that the invention may take a variety of other orientations and therefore such terms should not be considered limiting. In addition, all numbers representing sizes, physical characteristics, processing parameters, component amounts, reaction conditions, etc. used in the specification and claims are, in each case, modified by the term “about”. It should be understood as possible. Accordingly, unless stated to the contrary, the numerical values set forth in the following specification and claims are approximate and depend on the desired properties sought to be obtained by the present invention. It can be changed. At a minimum, rather than trying to limit the application of doctrine equivalent to the claims, each number is given by referring to at least a number of reported significant numbers and applying the usual rounding method. Should be regarded as being Further, it should be understood that many of the ranges described herein are encompassed by any and all small ranges contained therein. For example, a range stated as “1-10” should be considered to encompass any small range that falls between the lowest value of 1 and the highest value of 10 (including those values). . That is, all small ranges starting with a minimum value of 1 or more and ending with a maximum value of 10 or less, for example, a range such as 5.5-10 are included. Furthermore, as used herein, the term “deposited over” or “provided over” means deposited or applied above but not necessarily in contact with the surface. Means that For example, a coating “deposited over” a substrate does not exclude the presence of one or more other coating films of the same or different composition located between the deposited coating and the substrate. . Further, all percentages stated herein are by “weight” unless otherwise indicated. All photocatalytic activity values discussed herein were determined by the conventional stearic acid test described in US Pat. No. 6,027,766, incorporated herein by reference. Values of all the root mean square roughness is to be determined by measuring the root mean square of the (RMS) by atomic force microscopy over a surface area of 1 [mu] m ^2. Further, it is to be understood that documents referred to herein as “incorporated by reference” are incorporated in their entirety.

Referring now to FIG. 1, there is shown an article 20 having features of the present invention. The article 20 has a substrate 22 having a surface 21 with a light-induced hydrophilic (hereinafter referred to as PH) coating 24 of the present invention deposited over at least a portion of the surface 21. As used herein, the term “photo-induced hydrophilic coating” refers to a substance or coating that is photo-activated hydrophilic. “Photoactively hydrophilic” means a coating in which the contact angle of a water droplet on the coating surface decreases with time as a result of exposing the coating to electromagnetic waves. For example, the contact angle can be reduced to a value less than 15 °, eg, less than 10 °, can be superhydrophilic, eg, ohio, arranged to have a strength of 24 W / m ^{2 on} the PH coated surface After 60 minutes of exposure to UV light from a light source sold as QA-Panel Co. (trade name) UVA 340 by Cleveland Co., equal to or less than 5 °, eg equal to 4 ° Or less, for example, to a value equal to or less than 35 °. If the contact angle is exposed to the light source longer or exposed to a different light source and / or different illumination intensity, it is further, for example, equal to or less than 2 °, for example equal to or greater than 1 °. It can be reduced to small values.

  While not to be considered as a limitation on the present invention, the PH coating of the present invention is believed to be photoactive or behave like a photoactive. It will be appreciated by those skilled in the art that the term “photoactive” or “photoactively” refers to photogenerating a hole-electron pair when irradiated with radiation of a particular frequency. Examples of photoactive materials useful in the practice of the present invention include semiconductor metal oxides. Although photoactively hydrophilic, the coating 24 need not necessarily be photocatalytic to the extent that it is self-cleaning, i.e., as a stain on the coating surface in a reasonably or economically useful time. It may not be photocatalytic enough to decompose the organic material.

  As a broad embodiment of the present invention, the substrate 22 may be composed of any desired material having the desired optical properties. For example, the substrate 22 may be transparent to visible light. “Transparent” means having a transmission through the substrate 22 of greater than 0% and up to 100%. “Visible light” means electromagnetic energy in the range of 395 nm to 800 nm. Alternatively, the substrate 22 can be “translucent” or “transparent”. “Translucent” means passing electromagnetic energy (eg, visible light), but diffusing it to a point where the object on the other side is not clearly visible. “Opaque” means that the visible light transmittance is 0%. Suitable materials for the substrate 22 include plastics (eg, polymethyl methacrylate, polycarbonate, polyurethane, polyethylene terephthalate (PET), or copolymer of monomers to produce them, or mixtures thereof), Ceramic or glass is included. The glass can be of any type, for example, conventional float glass or flat glass, and any optical properties such as visible light transmission, ultraviolet transmission, infrared transmission, and / or total Any value of solar energy transmittance may consist of any composition having it. “Float glass” means glass formed by a conventional float method in which molten glass is placed on a molten metal bath and cooled under control to form a float glass band. The strip is then cut and / or molded and / or heat treated as desired. Examples of float glass are described in US Pat. Nos. 4,466,562 and 4,671,155. For example, the glass may be conventional soda / lime / silicate glass, borosilicate glass, or lead glass. The glass may be “transparent glass”, ie colorless or non-colored glass. Alternatively, the glass may be colored or otherwise colored glass. The glass may be unstrengthened, heat treated, or heat tempered glass. As used herein, the term “heat strengthened” means annealed, tempered, or at least partially quenched. While not limiting to the present invention, examples of glasses suitable for the substrate 12 include U.S. Pat. Nos. 4,746,347, 4,792,536, 5,240,886, and 5,385. 872, and 5,393,593, which are hereby incorporated by reference. The substrate 22 can be of any desired size, eg, length, width, shape, or thickness. For example, to name a few, the substrate 22 can be a glass plate of an architectural window, a light window, a single glass plate of an insulating glass unit, or a laminate for conventional windshields, side or rear windows. , Sunroof or aircraft transparency.

  The PH coating 24 may be deposited directly on the surface 21 of the substrate 22, ie, in surface contact, as shown in FIG. Even when using sodium-containing substrates such as soda, lime, and silica glass, the very thin PH coating of the present invention is due to the sodium in the substrate even when the coating is applied by the in-bath process described below. It has been found that it is not rendered non-hydrophilic. Therefore, soda, lime, and silica glass can be easily cleaned without using a sodium barrier layer between the glass and the PH coating of the present invention. In some cases, such a barrier layer may be used.

  Alternatively, as described below, between the PH coating 24 and the substrate 22, one or more other layers or coatings, ie, one or more functional coatings (eg, anti-reflection coatings) or sodium An ion diffusion barrier layer can be interposed. For example, the PH coating 24 may be the outer, ie, outermost, layer of a coating multilayer stack present on the substrate 22, or the PH coating 24 may be the outermost layer in such a multilayer stack. It may be embedded as one of the layers other than the outer layer. An “outer layer” is a layer that receives sufficient excitation electromagnetic waves, eg, ultraviolet radiation, to provide a coating with photoactivity sufficient to become photoactive hydrophilic, but not necessarily photocatalytic. means. Preferably, the PH coating 24 is the outermost coating on the substrate 22.

As discussed above, the PH coating 24 need not have a photocatalytic activity at a level comparable to previously known self-cleaning coatings. For example, the PH coating 24 is equal to or greater than 0 cm ⁻¹ min− ¹ and is equal to or greater than 5 × 10 ⁻³ cm ⁻¹ min− ¹ ± 2 × 10 ⁻³ cm ⁻¹ min− ^1. Small, for example equal to or less than 4 × 10 ⁻³ cm ⁻¹ min− ¹ , for example equal to 3 × 10 ⁻³ cm ⁻¹ min− ¹ ± 2 × 10 ⁻³ cm ⁻¹ min− ¹ , or It can have a photocatalytic activity that is less than, for example, in a range equal to or less than 2 × 10 ⁻³ cm ⁻¹ min− ¹ ± 2 × 10 ⁻³ cm ⁻¹ min− ¹ .

  The PH coating 24 can comprise any coating material that is photoactive hydrophilic and can be deposited by CVD, spray pyrolysis, or MSVD. For example, without limiting the invention, the PH coating 24 may be one or more metal oxides, metal alloy oxides, or semiconductor metal oxides or metal alloy oxides, such as titanium oxide, silicon oxide. Aluminum oxide, iron oxide, silver oxide, cobalt oxide, chromium oxide, copper oxide, molybdenum oxide, tungsten oxide, zinc oxide, zinc / tin alloy oxide, zinc stannate, titanic acid It can include, but is not limited to, strontium, and mixtures or combinations thereof. Metal oxides and / or metal alloy oxides include metal oxides, superoxides, or suboxides.

  One example of a PH coating 24 that is particularly useful in the practice of the present invention is titanium dioxide. Titanium dioxide exists in amorphous and three crystalline forms: anatase, rutile, and brookite crystal forms. Anatase phase titanium dioxide exhibits strong photoactive hydrophilicity while having excellent resistance to chemical erosion and excellent physical durability. The rutile phase of titanium dioxide can also exhibit photoactive hydrophilicity. Mixtures or combinations of anatase and / or rutile and / or brookite and / or amorphous phase are acceptable in the present invention as long as the combination exhibits photoactive hydrophilicity.

The PH coating 24 should have a thickness sufficient to provide an acceptable level of photoactive hydrophilicity. There is no absolute value to make the PH coating 24 “acceptable” or “unacceptable”. This is because whether a PH coating has an acceptable level of photoactive hydrophilicity varies greatly depending on the purpose and conditions for using the PH coated article and the performance criteria selected to meet that purpose. Because. However, as discussed above, the thickness of the PH coating 24 that achieves photoactive hydrophilicity is the thickness required to achieve a conventional commercially acceptable level of photocatalytic self-cleaning activity. It can be much smaller than that. For example, the PH coating 24 can have a thickness in the range of 10 to 5000 mm, and the thicker coating in this range can have hydrophilicity as well as photocatalytic self-cleaning activity. As the coating becomes thinner in this range, the photocatalytic self-cleaning activity typically decreases. As the thickness of the coating decreases in a range such as 50 to 3000 mm, such as 100 to 1000 mm, such as 200 to 500 mm, such as 200 to 300 mm, the photocatalytic self-cleaning activity may not be measurable, but was selected Hydrophilicity still exists in the presence of electromagnetic waves. If the substrate 22 is a piece of float glass and the PH coating 24 has some anatase titanium dioxide PH coat formed directly by CVD over the piece of float glass, then 200 to 300 inches. When the PH coating is exposed to UV light from a UVA-340 light source having a thickness of 24 W / m ² at the PH coated surface, 0-2 × 10 ⁻³ cm ⁻ for removal of the stearic acid test film. ¹ min- ¹ ± 2 × 10 ⁻³ cm ⁻¹ min− ¹ , for example, a photocatalyst in the range of 1.8 × 10 ⁻³ cm ⁻¹ min− ^{1 to} 2.8 × 10 ⁻³ cm ⁻¹ min− ^1. It has been found to provide activity. This PH coating also became superhydrophilic under this same UV light and had a water droplet contact angle in the range of 4 ° ± 2 ° to 7 ° ± 2 ° after 60 minutes exposure to a UVA-340 light source. One skilled in the art will recognize that the coating need not be of uniform thickness throughout its entire area. Therefore, the thickness values discussed here should be considered as the average thickness over the entire coating.

  As another aspect of the present invention, the outer surface of the PH coating 24 of the present invention can be made much smoother than previous hydrophilic self-cleaning coatings, but still maintain its photoactive hydrophilicity. For example, the coating 24, particularly the top or outer surface of the coating, is in the range of less than 5 nm, equal to or greater than 0 nm, even for thin coatings within the above range, such as 200 to 300 mm. Can have an RMS roughness, for example equal to or less than 4.9 nm, for example equal to or less than 4 nm, for example equal to or less than 3 nm, for example equal to 2 nm Or, for example, it can have an RMS roughness equal to or less than 1 nm, for example 0.3 nm to 0.7 nm. For example, the 200 to 300 ＰＨ PH coating discussed immediately above had an RMS surface roughness of 0.55 to 0.65 nm as measured with an atomic force microscope.

As yet another aspect of the present invention, the PH coating 24 can have a low visible light reflectivity. As used herein, “visible light reflectance” refers to conventional chromaticity coordinate designation (R ₁ ) Y (lighting C, observer angle 2 °). For example, the PH-coated article is 10% to 25%, such as 15% to 25%, such as 19% to 24%, such as 15% to 22%, such as 25% or less, such as , 23% or less, for example having a visible light reflectivity in the range equal to or less than 20%.

  As yet another aspect of the present invention, the PH coating 24 can be made denser than previous hydrophilic self-cleaning coatings. For example, the PH coating 24 can be substantially non-porous. “Substantially non-porous” means that the coating is sufficiently dense so that the coating can withstand a conventional hydrofluoric acid drop test. In the drop test, two drops of 0.5% by volume hydrofluoric acid (HF) aqueous solution were placed on the coated sample, and a conventional laboratory watch glass was placed on the sample for 8 minutes at room temperature. deep. After 8 minutes, remove the watch glass and inspect the coating for damage. The dense PH coating 24 of the present invention better protects the underlying substrate against chemical erosion than conventional more porous self-cleaning coatings and is stiffer than conventional self-cleaning coatings applied by the sol-gel method. It is even more difficult to get scratched.

  In accordance with the present invention, a PH coating having a thickness in the range of 10 to 500 mm, for example, less than or equal to 400 mm, for example 200 to 300 mm, is obtained by any one or more of spray pyrolysis, CVD, or MSVD. It can be formed on the substrate 22. In the spray pyrolysis method, the organic or metal-containing precursor is carried as an aqueous suspension, eg, an aqueous solution, and in the CVD method, it is carried in a carrier gas, eg, nitrogen gas, and directed toward the surface of the substrate 22. At the same time, the substrate 22 is brought to a temperature high enough to decompose the precursor on the substrate 22 and form a PH coating 24. In the MSVD method, a metal-containing cathode target is sputtered under reduced pressure in an inert atmosphere or an oxygen-containing atmosphere, and a sputter coating covering the substrate 22 is deposited. The substrate 22 is heated during or after coating to cause crystallization of the sputter coating to form a PH coating 24. Conventional spray pyrolysis, CVD, and MSVD methods are well understood by those skilled in the art and, therefore, may not be described in detail here.

  Each of these methods has advantages and disadvantages depending on the desired properties of the coating 24 and the type of glass manufacturing method. For example, in conventional float glass manufacturing, molten glass is poured onto a pool of molten metal, such as tin, in a molten metal (tin) bath to form a continuous float glass strip. The temperature of the float glass strip in the tin bath generally ranges from 1203 ° C. (2200 ° F.) at the inlet end of the bath to 592 ° C. (1100 ° F.) at the outlet end of the bath. The float glass strip is removed from the tin bath, annealed in a slow cooling furnace, ie, controlled to cool, and then cut into glass sheets of the desired length and width. The temperature of the float glass strip between the tin bath and the annealing lehr is in the range of 480 ° C. (896 ° F.) to 580 ° C. (1076 ° F.), and the temperature of the float glass strip in the slow cool furnace is , 204 ° C. (400 ° F.) to 557 ° C. (1035 ° F.) peak. U.S. Pat. Nos. 4,466,562 and 4,671,155 (incorporated herein by reference) provide a review of float glass manufacturing.

  CVD and spray pyrolysis methods are preferred over MSVD methods for float glass production. This is because they are better compatible with coating continuous substrates such as float glass strips at elevated temperatures. Examples of CVD and spray pyrolysis coating methods include U.S. Pat. Nos. 4,344,986, 4,393,095, 4,400,412, 4,719,126, 4,853. 257, and 4,971,843, which patents are incorporated herein by reference.

  In practicing the present invention, one or more CVD coating devices can be used at several points in the float glass strip manufacturing process. For example, a CVD coating apparatus can be used while a float glass strip moves through a tin bath, after it exits the tin bath, before it enters the slow cooling furnace, while it moves through the slow cooling furnace, or It can be used after leaving the slow cooling furnace. CVD methods can coat moving float glass strips, yet can withstand the harsh environments associated with producing float glass strips, so CVD methods can be used to float in molten tin baths. It is particularly well-suited for providing a PH coating 24 to a tempered glass strip. U.S. Pat. Nos. 4,853,257, 4,971,843, 5,536,718, 5,464,657, and 5,599,387 (herein for reference) Describes a CVD coating apparatus and method that can be used in the practice of the present invention to coat a float glass strip in a molten tin bath.

For example, as shown in FIG. 2, one or more CVD coating devices 50 can be placed at the tin bath 52 above the molten tin pool 54. While the float glass strip 56 moves through the tin bath 52, the precursor material is delivered to the top surface of the strip 56. The precursor material decomposes to form the PH coating of the present invention having photoactive hydrophilic activity. For example, the precursor material can be selected to decompose to form a semiconductor metal oxide, eg, a crystalline metal oxide. Examples of precursor materials that can be used in the practice of the present invention to form a titanium dioxide PH coating by CVD include titanium tetrachloride (TiCl ₄ ), titanium tetraisopropoxide [Ti (OC ₃ H ₇ ) ₄ (Hereinafter referred to as TTIP), titanium tetrabutoxide, titanium tetraethoxide [Ti (OC ₂ H ₅ ) ₄ ] (hereinafter referred to as TTEt), and mixtures thereof, including but not limited to is not. Examples of carrier gases that can be used in the CVD process include, but are not limited to, air, nitrogen, oxygen, ammonia, and mixtures thereof. The concentration of the metal-containing precursor in the carrier gas is 0.01% to 0.4% by volume, for example 0.05% to 0.4% by volume for the metal-containing precursors listed above, for example 0.05 vol% to 2 vol%, for example 0.05 vol% to 1 vol%, but these concentrations can be varied in the case of other metal-containing precursors Will be recognized by those skilled in the art.

  In the case of CVD methods (also the spray pyrolysis method discussed below), the temperature of the substrates during formation of the PH coating 24 on the substrate 22 (eg, float glass strip 56) is determined by the metal-containing precursor material. It should be within the range to decompose and form a coating having 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 titanium-containing precursors listed above, the minimum temperature of the substrate 22 that provides sufficient decomposition of the precursor can be in the range of 400 ° C. (752 ° F.) to 500 ° C. (932 ° F.). The upper limit of this temperature range is affected by the method of coating the substrate. For example, if the substrate 22 is a float glass strip 56 and the PH coating 24 is applied to the float glass strip 56 in the molten tin bath 52 during manufacture of the float glass strip 56, the float glass strip 56 is 1000. Temperatures in excess of 0 C (1832 F) may be reached. The float glass strip 56 can be increased or decreased in size, i.e. dimensioned (e.g. stretched or compressed), at temperatures above 800 <0> C (1472 <0> F). If the PH coating 24 is applied to the float glass strip 56 before or during its size increase or decrease, the PH coating 24 may be applied while the float glass strip 56 is being stretched or compressed. Each can crack or become glazed. Therefore, when the shape of the float method glass band 56 is stabilized (except in the case of thermal shrinkage due to cooling), for example, in the case of soda, lime, and silica glass, it becomes lower than 800 ° C. (1472 ° F.), and the float method glass band A PH coating can be applied when 56 is above a temperature at which the metal-containing precursor can be decomposed, eg, 400 ° C. (752 ° F.).

  Spray pyrolysis is described in US Pat. Nos. 4,719,126, 4,719,127, 4,111,150, and 3,660,061 (incorporated herein for reference). Describes a spray pyrolysis apparatus and method that can be used in a conventional float glass strip manufacturing process. As with CVD, spray pyrolysis is well suited for coating moving float glass strips, but spray pyrolysis has more complex equipment than CVD equipment, usually at the end of the tin bath. And the inlet end of the annealing furnace.

Examples of metal-containing precursors that can be used in the practice of the present invention to form PH coatings by spray pyrolysis include relatively water-insoluble organometallic reactants, particularly metal acetylacetonate compounds. They are jet milled or wet milled to a particle size of less than 10 microns and suspended in an aqueous medium by using a chemical wetting agent. A suitable metal acetylacetonate for forming the titanium dioxide PH coating is titanyl acetylacetonate [TiO (C ₅ H ₇ O ₂ ) ₂ ]. The relative concentration of metal acetylacetonate in the aqueous suspension is in the range of 5-40% by weight of the aqueous suspension. The wetting agent can be any relatively low foaming surfactant, including anionic, nonionic, or cationic compositions, but nonionic is preferred. The wetting agent is typically added at 0.24% by weight, but can range from 0.01% to 1% or more. The aqueous medium is preferably distilled water or deionized water. Aqueous suspensions for the pyrolytic deposition of metal-containing films are described in US Pat. No. 4,719,127, which is hereby incorporated by reference, in particular in column 2. 16th line to 4th column, 48th line.

  The lower surface of the float glass strip directly on molten tin (commonly referred to as the “tin side”) has diffused tin on the surface that contacts the molten tin on the tin side. The opposite surface (generally referred to as the “air side”) that did not give a different tin absorption pattern. The PH coating of the present invention may be formed by the CVD method as described above on the air side of the float glass strip, while it is supported on tin, In addition, it may be formed by CVD or spray pyrolysis after it exits the tin bath and / or on the tin side of the float glass strip by CVD after it exits the tin bath. May be.

  For MSVD, U.S. Pat. Nos. 4,379,040, 4,861,669, 4,900,633, 4,920,006, 4,938,857, 5,328, Nos. 768 and 5,492,750 (incorporated herein for reference) describe MSVD apparatus and methods for sputter coating metal oxide films on substrates, including glass substrates. Has been. The MSVD method is generally not compatible with providing a PH coating on a float glass strip during its manufacture. This is because, in particular, the MSVD method requires a reduced pressure during the sputtering operation that is difficult to form on a continuously moving float method glass strip. However, the MSVD method is acceptable for depositing the PH coating 24 on the substrate 22, eg, a glass sheet. Heating the substrate 22 to a temperature in the range of 400 ° C. (752 ° F.) to 500 ° C. (932 ° F.) to crystallize the MSVD sputtered coating on the substrate during the deposition process, thereby eliminating subsequent heating operations. Can do. Heating the substrate during spattering may be undesirable in some cases. This is because the additional heating operation during sputtering reduces productivity. Alternatively, sputter coating can be crystallized directly in the MSVD coating equipment without the use of post-heat treatment by using high energy plasma, but again in this case the productivity tends to be reduced by the MSVD coating equipment. This is not a preferred method as it is.

  An example of a method of providing a PH coating using the MSVD method (particularly, a PH coating having an RMS roughness of 300 nm or less and having an RMS roughness of 2 nm or less) is to sputter the coating on the substrate and take out the coated substrate from the MSVD coating apparatus. Thereafter, the coated substrate is heat treated to crystallize the sputter coating to a PH coating 24. For example, but not limiting of the present invention, a titanium metal target is sputtered at a pressure of 5 to 10 millitorr in an argon / oxygen atmosphere containing 5 to 50%, for example, 20% oxygen. A titanium dioxide coating of the desired thickness can be sputter deposited on top. The as-deposited coating is not crystallized. The coated substrate is removed from the coating apparatus and heated to a temperature in the range of 400 ° C. (752 ° F.) to 600 ° C. (1112 ° F.) for a time sufficient to promote the formation of the PH crystalline form of titanium dioxide, Activate. For example, the coated substrate can be heated to a temperature in the range of 400 ° C. (752 ° F.) to 600 ° C. (1112 ° F.) for at least 1 hour. If the substrate 22 is a glass sheet cut from a float glass strip, the PH coating 24 can be sputter deposited on the air side and / or the tin side.

  The substrate 22 having a PH coating 24 deposited by CVD, spray pyrolysis, or MSVD can then be subjected to one or more post-PH coating annealing operations. The annealing temperature and time are determined by the configuration of the substrate 22, the configuration of the PH coating 24, the thickness of the PH coating 24, and whether the PH coating 24 is in direct contact with the substrate 22 or one of the multilayer stacks on the substrate 22. It will be appreciated that it is affected by several factors including whether it is a stratum.

  If the substrate 22 contains sodium ions that can be transferred from the substrate 22 into the PH coating deposited on the substrate 22, the sodium ions are applied when the PH coating is applied by CVD, spray pyrolysis, or MSVD. Prevent or destroy the photoactive hydrophilicity of the PH coating by forming an inert compound while consuming titanium, for example, by forming sodium titanate or by causing recombination of photoexcited charges. There is. Accordingly, a sodium ion diffusion barrier (SIDB) layer can be deposited on the substrate prior to depositing the PH coating 24. Suitable SIDB layers are discussed in detail in US Pat. No. 6,027,766 (herein incorporated by reference) and will not be discussed in detail here. When post-coating heating is used, sodium-containing substrates such as soda, lime, and silica glass preferably have a sodium barrier layer. When applying the PH coating of the present invention in a molten metal bath, the sodium barrier layer is optional.

  The PH coating of the present invention preferably becomes photoactive hydrophilic when exposed to radiation in the ultraviolet range of the electromagnetic spectrum, for example, in the range of 300 nm to 395 nm. Ultraviolet sources include natural sources, eg, artificial light sources such as solar radiation, black light, or ultraviolet light sources such as the UVA-340 light source as described above.

  As shown in FIG. 1, in addition to the PH coating 24 of the present invention, one or more additional coatings, such as a functional coating 46 (described below), are deposited on or over the substrate 22. can do. For example, the functional coating 46 can be deposited over the major surface 60 of the substrate 22 opposite the surface 21. The functional coating 46 may be deposited by any conventional method, for example, spray pyrolysis, CVD, MSVD, sol-gel method, etc., but is not limited thereto. For example, US Pat. Nos. 4,584,206 and 4,900,110 (incorporated herein for reference) deposit metal-containing films on the lower surface of the glass strip by chemical vapor deposition. A method and apparatus for doing so are described. Such a known device can be placed downstream of the molten tin bath in the float glass production to provide a functional coating on the underside of the glass band, i.e., opposite the PH coating of the present invention. Alternatively, one or more other CVD coating devices can be placed in the tin bath to deposit the functional coating on or below the PH coating 24 of the float glass strip.

  An example of a manufactured article of the present invention is shown in FIG. 3 in the form of an insulating glass (IG) unit 30. The insulating glass unit has a first glass plate 32 separated from a second glass plate 34 by a spacer assembly (not shown), the glass plate being between the two glass plates 32, 34. It is held in place by a sealing system so that the chamber is formed. The first glass plate 32 has a first surface 36 (surface number 1) and a second surface 38 (surface number 2). The second glass plate 34 has a first surface 40 (surface number 3) and a second surface 42 (surface number 4). The first surface 36 may be the outer surface of the IG unit, i.e. the surface exposed to the environment, and the second surface 42 may be the inner surface, i.e. the surface that forms the inside of the structure. Examples of IG units are described in US Pat. Nos. 4,193,236, 4,464,874, 5,088,258, and 5,106,663 (incorporated herein for reference). Is). As shown in FIG. 3, the PH coating 24 is preferably disposed on the number 1 or number 4 surface, and preferably on the number 1 surface. The PH coating 24 reduces haze and makes the IG unit 30 easier to clean and maintain.

  Optionally, one or more functional coatings 46 can be deposited over at least a portion of the number 2, number 3, or number 4 surface. As used herein, the term “functional coating” refers to a coating that changes over one or more physical properties of the substrate on which it is deposited, such as optical, thermal, chemical, or mechanical properties. And is not intended to be removed from the substrate during subsequent processing. The functional coating 46 can have one or more functional coating films with the same or different composition or functionality. As used herein, the term “layer” or “film” refers to the coating area of the desired or selected coating composition. The film may be uniform, non-uniform, or have a graded compositional change. The outer surface or portion (ie, the surface or portion furthest from the substrate), the inner surface or portion (ie, the surface or portion closest to the substrate), and the portion between the outer and inner surfaces have substantially the same composition. If so, the film is “uniform”. The film has a fraction that increases substantially for one or more components and a fraction that decreases substantially for one or more other components when it moves from the inner surface to the outer surface or vice versa. In this case, the film is “graded”. A film is “non-uniform” if it is other than uniform or gradual. The “coating” is composed of one or more “films”.

  Is the functional coating 46 an electrically conductive coating such as, for example, an electrically conductive heating window coating as described in US Pat. Nos. 5,653,903 and 5,028,759? Or a single film or multilayer film coating that can serve as an antenna. Similarly, the functional coating 46 can be a solar control coating, such as a visible light, infrared, or ultraviolet energy reflective or absorbing coating. Examples of suitable solar control coatings include U.S. Pat. Nos. 4,898,789, 5,821,001, 4,716,086, 4,610,771, 4,902,580. No. 4,716,086, No. 4,806,220, No. 4,898,790, No. 4,834,857, No. 4,948,677, No. 5,059,295, And US Pat. No. 5,028,759 and US patent application no. 09 / 058,440. Similarly, the functional coating 46 can be a low radiation coating. “Low-radiation coating” allows visible wavelength energy, eg, 400 nm to 780 nm, to be transmitted through the coating, but reflects longer wavelengths of solar and / or thermal infrared energy and is built into the building Typically, the aim is to improve the thermal insulation of the window glass. “Low radiation” means a radiation less than 0.4, preferably less than 0.3, more preferably less than 0.2. Examples of low-radiation coatings are found, for example, in US Pat. Nos. 4,952,423 and 4,504,109 and British Patent GB 2,302,102. The functional coating 46 may be a single layer or multi-layer coating and may include one or more metals, non-metals, metalloids, semiconductors, and / or alloys, compounds, composites, combinations or mixtures thereof. For example, the functional coating 46 can be a single layer metal oxide coating, a multilayer metal oxide coating, a non-metal oxide coating, or a multilayer coating. Furthermore, the functional coating can be an antireflective coating.

  Examples of functional coatings suitable for use in the present invention are those of the SUNGATE® and SOLARBAN® series of coatings from PPG Industries, Pittsburgh, PA. It is commercially available. Such functional coating is one or more comprising a dielectric or antireflective material, preferably a metal oxide or metal alloy oxide, which is preferably transparent or substantially transparent to visible light. Typically, an antireflective coating film is included. The functional coating 46 can also include an infrared reflective film comprising a reflective metal, eg, a noble metal such as gold, copper, or silver, or combinations or alloys thereof, and further over the metal reflective layer and An underlying film or barrier film, such as titanium, as known in the art, may be included.

  The functional coating 46 may be magnetron sputter deposition (MSVD), chemical vapor deposition (CVD), spray pyrolysis (ie pyrolysis deposition), atmospheric pressure CVD (APCVD), low pressure CVD (LPCVD), plasma enhanced CVD (PECVD), Deposited in any conventional manner such as plasma assisted CVD (PACVD), thermal or electron beam evaporation, cathodic arc evaporation, plasma spray evaporation, and wet chemical vapor deposition (eg, sol-gel, silver mirror formation, etc.) Good, but not limited to them. If the functional coating is applied to the PH coating side of the substrate, it is preferred to apply the functional coating in a tin bath prior to PH coating. If the functional coating is on the opposite side 60 from the PH coating, the functional coating is applied to the tin side of the substrate 22 after a float tin bath, eg, by CVD or MSVD, as discussed above. can do.

  In the above discussion, the PH coating was applied over the air side of the substrate and the functional coating was applied over the tin side of the substrate, but the functional coating may be applied over the air side of the substrate. Will understand. For example, it may be applied to a float glass strip in a tin bath, after which the tin side of the substrate is covered and a PH coating is applied by any desired method, such as the method described above.

  The advantages of the present invention over the sol-gel method of forming a self-cleaning coating include a thin and dense coating on the substrate, as opposed to the generally thicker porous self-cleaning coatings obtained by the sol-gel coating method. It is included that a simple PH film can be formed. Since the PH coatings of the present invention are thin, eg, equal to or less than 500 mm, preferably equal to or less than 300 mm, they should be aesthetically acceptable for use as a transparent coating on a glass substrate. Can do. Yet another advantage is that the method of providing a PH coating according to the present invention eliminates the need to reheat the substrate after applying the coating or coating precursor, as required by currently available sol-gel methods. It is that you are. This makes the method of the present invention less expensive and more efficient, such as lower equipment costs, lower energy costs, and shorter manufacturing times (but not limited to them). Not only that, the PH coating of the present invention significantly reduces the opportunity for sodium ion migration and thus poisoning by sodium ions. In addition, the method of the present invention is easy to adapt to form PASC coatings on a continuously moving substrate such as a float glass strip, whereas currently available sol-gel methods are much easier. It cannot be adapted to.

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

Over a 386 cm (152 ") float glass strip (3.3 mm thick clear glass) moving at a rate of 1,229 cm / min (484 in / min) in a conventional tin bath by conventional CVD. A 122 cm (48 ") wide PH coating of titanium dioxide having a thickness of 232 mm (determined by polarization and transmission data) was deposited. The coating was formed from a precursor material that was 0.07 mole percent titanium tetraisopropoxide in a nitrogen-containing carrier gas and was applied at a glass band temperature of 659 ° C. (1220 ° F.). The coated strip was then annealed, ie cooled at a controlled rate, and cut into 7.5 cm (3 ″) × 15 cm (6 ″) sample pieces. The crystal structure of the deposited coating was determined to be anatase by X-ray diffraction. The coating has a photocatalytic activity of 1.8 × 10 ⁻³ cm ⁻¹ min− ¹ as determined by a conventional stearic acid test, reflectance (R ₁ ) Y = 19.43, x = 0.2741. , Y = 0.2774, and transmittance Y = 78.50, x = 0.3187, y = 0.3279, with chromaticity coordinates (illumination C, observer angle 2 °).

To measure the photoactive hydrophilicity of the coated article, the sample piece was diluted (pH 2.9) with a DART 210 cleaner, commercially available from Madison Chemical Inc., Medison, Indiana. Using an aqueous solution, ultrasonic cleaning was performed at 145 ° F. for 20 minutes. The sample piece was then rinsed with room temperature deionized water and then a second ultrasonic cleaning in deionized water at 155 ° F. for 10 minutes. The sample pieces were rinsed again with room temperature deionized water and blown dry with compressed nitrogen. The sample piece was irradiated with UV radiation from a UVA340 bulb at 24 W / m ² and the contact angle of the water droplet was measured over time. The water droplet contact angle was measured with a Rame-Hart telephoto angle measuring instrument, model 102-00-115, with the sample in the horizontal (non-tilt) position. For each sample measured, the water droplet contact angle decreased from about 21 ° to 47 ° to about 4 ° to 11 ° with UVA-340 irradiation for about 30 minutes, and about 3 ° to 7 with about 60 minutes of irradiation. It dropped to °.

  Several sample pieces were subjected to a taber abrasion test using a CS-10F disc having a load of 1000 g at 10 cycles and 25 cycles. The permeation haze for each sample was determined to be 0.0 using the Pacific Scientific XL211 HazeGuard System. For five specimens, test numbers of ANSI Z26.1-1983 for abrasion resistance. A plate rotation wear test was performed according to 18 methods (1000 cycles, 500 g per plate), giving an average increase in diffused light of 2.4%.

  The sample pieces were subjected to several conventional test methods and the results are given in Table 1 below. Film degradation results are based on visual observation and reflect color measurements. Contact angle results were determined as described above.

  As shown in Table 1, the PH coating showed no film degradation and maintained its light-induced hydrophilicity after each test.

  Those skilled in the art will readily recognize that modifications can be made to the present invention without departing from the concepts disclosed in the above description. Accordingly, the specific embodiments described in detail herein are for purposes of illustration only and are not intended to limit the scope of the invention. The scope of the present invention should be accorded the full scope of the claims and any equivalents thereof.

20 Article 21 Base Surface 22 Base 24 PH Coating 30 Insulating Glass Unit 32 First Glass Plate 34 Second Glass Plate 36 First Surface 38 Second Surface 40 First Surface 42 Second Surface 46 Functional Coating 50 CVD Coating Device 52 Tin Bath 56 Float glass strip 60 Main surface of substrate

Claims (3)

A float glass substrate having at least one surface, and a light-induced hydrophilic coating of titanium dioxide, a photoactive hydrophilic coating, deposited directly on at least a portion of said at least one surface, having a thickness of from 100 to 300 mm A light-induced hydrophilic coating having a thickness, the outer surface of which has a light-induced hydrophilic coating having a root mean square roughness less than 2 nm;
When the light-induced hydrophilic coating is exposed to UV light from a UVA-340 light source having an intensity of 24 W / m ^{2 on} the light-induced hydrophilic coating surface, for removal of the stearic acid test film,
Architectural window in which the light-induced hydrophilic coating has a photocatalytic activity equal to or less than 3 × 10 ⁻³ cm ⁻¹ min− ¹ .   The architectural window according to claim 1, wherein the root mean square roughness is 0.3 nm to 0.7 nm. The architectural window according to claim 1, wherein the thickness is 200 to 300 mm and the root mean square roughness is 0.55 to 0.65 nm.

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