Photo-induced hydrophilic article and method of making same

Light-induced hydrophilic products and preparation method thereof

Cross-reference of related applications This application is a continuation application of the US patent application 09/282943 entitled "Photocatalytically activated self-cleaning appliance" filed on April 1, 1999, which was filed on July 23, 1997 A divisional application of U.S. Patent Application 08/899257 (now US6027766), which claims priority of U.S. Provisional Application 60/040566 filed on March 14, 1997, the entire contents of these applications are incorporated herein by reference. This application also claims priority to the United States Patent Provisional Application 60/272197 entitled "Photo-induced Hydrophilic Articles and Methods of Making the Same" filed on February 28, 2001, the entire contents of which are hereby incorporated by reference.

1. Scope of the invention The present invention relates to methods for depositing hydrophilic coatings on substrates, such as glass plates or continuous float glass ribbons, and to articles prepared by these methods.

2. Technical considerations In the following discussion, general technical considerations related to the present invention will be discussed. However, it is not considered that the specific references discussed here constitute "prior art" in the US patent regulations, and such recognition is not made.

For many substrates, such as glass substrates such as architectural windows, automotive light-transmitting windows and airplane windows, for good visibility, it is desirable that the substrate surface be free of surface contaminants for as long as possible, such as common organic surface pollution And inorganic pollutants. Traditionally, this meant cleaning these surfaces frequently. This cleaning operation is usually performed by manually wiping the surface, with or without chemical cleaning solutions. This method is laborious, time-consuming, and/or expensive. Therefore, there is a need for substrates with a surface that is easier to clean than existing glass substrates, especially glass substrates, which reduces the need or frequency of such manual cleaning.

It is known that certain metal oxide semiconductors can be added to the coating in order to provide a self-cleaning photocatalytically activated (hereinafter referred to as "PA") coating, that is, the coating and the coating described under exposure to certain electromagnetic radiation The organic pollutants on the coating surface interact to degrade or decompose the pollutants. The patents and products that usually involve the photocatalytic oxidation of organic compounds are reported in D.Blake's Bibliography of work on The photocatalytic Removal of Hazardous Compounds from Water and Air, National Renewable Energy Laboratory (May 1994), updated in October 1995 and October 1996.

Generally, these PA coatings are made thick enough to have sufficient photocatalytic activity to destroy or decompose organic pollutants on the coating in the shortest possible time. For example, WO00/75087 discloses a photocatalytically activated coating with a minimum photocatalytic activity of 5×10-3 cm-1min-1. For example, other PA coatings are disclosed in US 5873203, 6027766 and 6054227.

In addition to self-cleaning properties, these PA coatings are usually hydrophilic, that is, water-wet. The hydrophilicity of the PA coating helps to reduce fogging, that is, the accumulation of water droplets on the coating, which can reduce the transmission of visible light and the visibility through the coated substrate. So far, this hydrophilicity has been related to several factors, including increased surface roughness of the coating and increased porosity of the coating. For example, US 6103363 discloses such a hydrophilic photocatalytically activated self-cleaning coating, the preferred root mean square (RMS) surface roughness is 5-15 nm, and the preferred porosity is 70-90%. However, this surface roughness can make surface cleaning more difficult, such as generating small grooves where dust and dirt can accumulate, or pulling and breaking fibers from a cleaning cloth wiped on the surface. Moreover, the increase in the porosity of the coating also creates some pores that can chemically attack the underlying substrate.

In order to achieve the desired coating thickness, photocatalytic activity, surface roughness and coating porosity, many kinds of PA self-cleaning coatings have been deposited by sol-gel technology. In a typical sol-gel method, an uncrystallized colloidal suspension is applied to a substrate at about normal temperature, and then heated to produce a crystallized coating. For example, US 6013372 discloses a hydrophilic photocatalytically activated self-cleaning coating produced by the following steps: the photocatalyst particles are blended in the metal oxide layer, and then the blend is applied to the substrate by the sol-gel method. Material.

However, the traditional sol-gel method is economically or practically inconsistent with certain application conditions or substrates. For example, in the conventional float glass method, the float glass ribbon in the molten metal bath may be too hot, so that the sol cannot be used due to the vaporization or chemical reaction of the solvent used in the sol. In addition, the environment in the molten metal bath is also detrimental to the moving machinery such as spray equipment required to coat the sol. Therefore, the sol usually has to be applied after the float glass ribbon comes out of the molten bath and cooled to about room temperature. The coated glass ribbon is then heated to a temperature sufficient to crystallize the coating. Such cooling and reheating operations require huge investments in equipment, energy, and processing costs, while also greatly reducing production efficiency. In addition, the reheating of sodium-containing substrates such as soda-lime silica glass increases the chance that sodium ions in the substrate migrate to the coating, which is traditionally referred to as "sodium ion poisoning" of the deposited coating. The presence of these sodium ions can reduce or destroy the photocatalytic activity of the self-cleaning coating. Moreover, the sol-gel method usually produces thick coatings, that is, a few microns thick, which may adversely affect the optical and/or aesthetic properties of the coated article. Generally, as the thickness of the PA self-cleaning coating increases, the light transmittance and reflectivity of the coating pass a series of minimum and maximum values due to the light interference effect. Due to these optical effects, the reflection color and transmission color of the coating are changed. Therefore, a coating thickness sufficient to provide the required self-cleaning properties may have undesirable optical properties.

Therefore, it is advantageous to provide such an article with a coating, especially a hydrophilic coating, and a method for preparing the article, which reduces or eliminates at least some of the above-mentioned disadvantages.

SUMMARY OF THE INVENTION The present invention relates to an article comprising a substrate having at least one surface and a hydrophilic coating deposited on at least a portion of the surface, in particular a light-induced hydrophilic coating (specified below). The coating may be deposited by a method selected from chemical vapor deposition (hereinafter "CVD"), spray pyrolysis, and/or magnetron vacuum deposition (hereinafter "MSVD"). In one embodiment, the root mean square roughness of the coating, such as the outer surface of the coating, may be greater than or equal to 0 nm to less than or equal to 4 nm, such as less than or equal to 3 nm, such as less than or equal to 2 nm, such as less than or equal to 1 nm. It is particularly advantageous if the substrate is a float glass ribbon and the coating is deposited by CVD in a molten tin bath during the preparation of the float glass ribbon. In another specific embodiment of the present invention, the photocatalytic activity of the light-induced hydrophilic coating is greater than or equal to 0 cm-1 min-1 to less than or equal to 3×10-3 cm-1 min-1, for example, less than or equal to 2× 10-3cm-1min-1. In another embodiment of the present invention, the substrate is a float glass ribbon in a molten metal bath, the thickness of the light-induced hydrophilic coating is greater than 0 angstroms to less than or equal to 500 angstroms, and the light-induced hydrophilicity The coating is deposited by chemical vapor deposition in a molten metal bath. The invention also relates to a method of preparing such an article.

Surprisingly, it has been found that very thin semiconducting metal oxide coatings, for example, a semiconducting metal oxide coating of approximately greater than 0 angstroms to less than or equal to 500 angstroms, are thinner than coatings commonly used to achieve photocatalytic self-cleaning properties. Even when the photocatalytic activity of a very thin coating is lower than the activity normally required for a self-cleaning coating to decompose organic pollutants, it retains its hydrophilicity. Therefore, although the thin semiconducting metal oxide coating still retains sufficient photoactivity for hydrophilicity, it may not have sufficient long-term optical activity for having a measurable or commercially acceptable photocatalytic self-cleaning activity. This light-induced hydrophilicity provides low fogging and/or also makes coated articles easier to clean than uncoated articles, for example easier to wipe, in order to remove dust and/or water spots. Moreover, the light-induced hydrophilicity also allows water to form and spread and dry faster, and it reduces water spots, because water is not easy to form water droplets and leave spots. It is also easier to remove dust by simply washing the coating without manually wiping the coating. In addition, these very thin semiconducting metal oxide coatings will not suffer from the undesirable optical problems associated with thicker photocatalytic self-cleaning coatings. It was also surprisingly discovered that these very thin semiconducting metal oxide coatings can be made smoother and denser than originally thought, while still retaining their light-induced hydrophilicity. Suitable semiconducting metal oxides that can be used in the practice of the present invention are titanium oxides.

In one embodiment, the present invention provides a substrate having at least one surface with a light-induced hydrophilic semiconducting metal oxide coating such as a titanium dioxide coating, and the coating passes CVD, spray pyrolysis or MSVD method is deposited on at least a part of the surface. The thickness of the coating can be greater than 0 angstroms to less than or equal to 500 angstroms, such as less than or equal to 400 angstroms, such as less than or equal to 300 angstroms, and the RMS roughness of the outer surface of the coating can generally be greater than or equal to 0 nm to less than or equal to 2 nm , For example, 1.9 nm or less, for example, 1 nm or less. For the coating of the present invention with a thickness of about 200 angstroms or less, the coating surface may not be too smooth, for example, the RMS roughness may be 5nm or less, for example 4.9nm or less, for example 4nm or less, for example 3nm or Smaller, for example 2 nm or less, for example 1 nm or less. In a specific embodiment, the substrate is a ribbon of float glass in a molten tin bath.

In one embodiment, the present invention provides an article comprising a float glass ribbon 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 the float glass ribbon in the molten metal bath.

The present invention also provides an article comprising a substrate with at least one surface and a light-induced hydrophilic coating deposited on at least a part of the at least one surface. The substrate can be a float glass ribbon in a molten metal bath, the thickness of the light-induced hydrophilic coating can be 500 angstroms or less, and the light-induced hydrophilic coating can be deposited in the molten metal by chemical vapor deposition. On the at least one surface in the metal bath.

The present invention also provides an article comprising a substrate with at least one surface and a light-induced hydrophilic coating deposited on at least a part of the at least one surface. The light-induced hydrophilic coating can be deposited by chemical vapor deposition at 500-1200°C, and the thickness of the light-induced hydrophilic coating can be 500 angstroms or less.

A method of forming a light-induced hydrophilic coating on at least a part of a substrate is provided. The method includes providing a substrate with a first surface and a second surface, at least one of the surfaces having tin diffused therein; and applying a metal oxide precursor selected from the group consisting of chemical vapor deposition, spray pyrolysis and magnetron The method of sputtering vacuum deposition is deposited on at least one of the surfaces from the coating equipment; and the substrate is heated to a temperature sufficient to decompose the metal oxide precursor to generate light with a root mean square roughness of 2 nm or less Induced hydrophilic coating.

Another method of forming a light-induced hydrophilic coating on at least a portion of a substrate, the method includes providing a ribbon of float glass in a molten metal bath; The coating equipment is directly deposited on the top surface of the float glass ribbon; and the glass ribbon is heated to a temperature sufficient to decompose the metal oxide precursor to generate a light-induced hydrophilic coating.

Another method of forming a light-induced hydrophilic coating on at least a portion of a substrate, the method includes providing a substrate with at least one surface; depositing a metal oxide precursor from a CVD coating device to the at least On at least a part of a surface; heating the substrate to 400-1200°C to decompose the metal oxide precursor to form a light-induced hydrophilic coating; and providing sufficient precursor material to cause light-induced hydrophilicity The thickness of the coating is 500 angstroms or less.

The invention also relates to products prepared by the method of the invention.

Description of the drawings

Figure 1 is a cross-sectional view (not to scale) of a part of a substrate with a light-induced hydrophilic coating of the present invention; Figure 2 is a molten metal bath for applying the semiconductor metal oxide coating of the present invention to the float glass process A side view of the coating method on the glass ribbon in (not to scale); Figure 3 is a side view of the insulating glass structure with the characteristics of the present invention (not to scale).

DETAILED DESCRIPTION OF THE INVENTION As used herein, spatial or directional terms such as "internal", "external", "above", "below", "top", "bottom", etc. are related to the present invention, as shown in the drawings. However, it should be understood that the present invention can have various alternative orientations, so such terms are not meant to be limiting. In addition, all numbers representing dimensions, physical properties, processing parameters, component quantities, reaction conditions, etc. used in the specification and claims should be understood as being changed by the term "about" in all cases. Therefore, unless otherwise stated, the numerical values shown in the following description and claims are approximate values, and they can be closely related to the desired performance that is attempted to be obtained with the present invention. At a minimum, and not intended to limit the scope of the claims to the application of the doctrine of equivalence, at least each value should be interpreted based on the number of important numbers reported and the application of conventional rounding techniques. Moreover, all ranges disclosed herein should be understood to include any and all sub-ranges contained herein. For example, the so-called "1-10" range should be considered to include any and all sub-ranges between the minimum value 1 and the maximum value 10 (inclusive); that is, the minimum value is 1 or greater, and the maximum value is 10. Or all sub-ranges ending in smaller, for example 5.5-10. In addition, as used herein, the term "deposited on" or "provided on" refers to deposition or provision on, but not necessarily in contact with the surface. For example, a substrate whose coating is "deposited on" does not exclude the presence of one or more coating films of the same composition or different compositions between the deposited coating and the substrate. In addition, unless otherwise specified, all percentages mentioned herein are percentages by weight. All the photocatalytic activity values described here are measured using the traditional stearic acid test disclosed in US 6027766, which is incorporated herein by reference. All root mean square roughness values are determined by the root mean square (RMS) measurement on a surface area of 1 square micrometer using an atomic force microscope. In addition, all references incorporated herein as references should be understood as their entire contents are incorporated.

Referring now to Figure 1, there is shown an article 20 that features the features of the present invention. The article 20 includes a substrate 22 with a surface 21, and the photo-induced hydrophilic (hereinafter referred to as PH) coating 24 of the present invention is deposited on at least a portion of the surface 21. As used herein, the term "photo-induced hydrophilic coating" refers to a photo-activated hydrophilic material or coating. "Photoactivated hydrophilic" refers to a coating in which the contact angle of water droplets on the surface of the coating decreases over time due to the exposure of the coating to electromagnetic radiation. For example, the contact angle can be lowered to less than 15°, such as less than 10°, and exposed to the UV rays produced by the light source sold under the trade name UVA 340 of Q-Panel Company of Cleveland, Ohio after 60 minutes can become superhydrophilic, such as When it is lowered to less than or equal to 5°, for example, less than or equal to 4°, for example, to less than or equal to 35°, the position of the light source can have an intensity of 24W/m2 on the surface of the PH coating. When exposed to the light source for a longer period of time or exposed to different light sources and/or different illumination intensities, the contact angle may even further decrease, for example, less than or equal to 2°, for example, less than or equal to 1°.

Although not as a limitation to the present invention, it is considered that the PH coating of the present invention is photo-activated or its behavior is photo-activated. As understood by those skilled in the art, the term "photoactivated" refers to photo-generated hole-electron pairs irradiated with rays of a specific frequency. Exemplary photoactive materials suitable for use in the practice of the present invention include semiconducting metal oxides. Although the photoactivated hydrophilic coating 24 may not be photocatalytic enough to be self-cleaning, that is, it may decompose organic materials and other contaminants on the coating surface within a reasonable or economically effective time. Not enough photocatalysis.

In the broad practice of the present invention, the substrate 22 can be any desired material having any desired optical properties. For example, the substrate 22 may be transparent to visible light. The so-called "transparent" means that the transmittance through the substrate 22 is greater than 0% up to 100%. The so-called "visible light" refers to the electromagnetic energy of 395-800nm. Alternatively, the substrate 22 may be translucent or opaque. The so-called "translucent" means that electromagnetic energy (such as visible light) can pass through, but its diffusion is such that objects on the other side cannot be clearly seen. The so-called "opaque" means that the transmittance of visible light is 0%. Suitable materials for the substrate 22 include plastics (e.g. polymethylmethacrylate, polycarbonate, polyurethane, polyethylene terephthalate (PET) or copolymers of any monomers used to prepare these polymers, or Mixture), ceramic or glass. The glass can be any type of glass, such as traditional float glass or flat glass, and can be any composition with any optical properties, such as any value of visible light transmittance, ultraviolet light transmittance, infrared light transmittance and/or total Solar energy transmittance. The so-called "float glass" refers to glass prepared by the traditional float glass method, in which molten glass is deposited on a molten metal bath and controlled cooling to produce a float glass ribbon. If necessary, the glass ribbon is then cut and/ Or forming and/or heat treatment. An example of the float glass method is in US 4466562 and 4671155. For example, the glass can be traditional soda-lime silica glass, borosilicate glass or lead-containing glass. The glass can be "transparent glass", that is, uncolored or colorless glass. On the other hand, the glass may be tinted or colored glass. The glass can be tempered, heat-treated or heat strengthened glass. As used herein, the term "thermally strengthened" refers to annealed, tempered, or at least partially tempered. Although not limiting the present invention, examples of glass suitable for the substrate 12 are disclosed in US 4746347, 4792536, 5240886, 5385872, and 5393593, which are hereby incorporated by reference. The substrate 22 can have any desired size, such as length, width, shape, or thickness. For example, the substrate 22 can be a glass pane of a building window, a skylight, a pane of a thermal insulation glass unit, or used in traditional automobile windshield components, side or rear windows, skylights, or aircraft light transmission equipment. Only given here Some examples.

The PH coating 24 can be deposited directly on the surface in contact with it, such as the surface 21 of the substrate 22 shown in FIG. 1. It has been found that even sodium-containing substrates such as soda lime silica glass, when the coating is coated by the following molten pool method, will not cause the very thin PH coating of the present invention to lose its hydrophilicity through the sodium in the substrate. . Therefore, when there is no sodium barrier layer between the glass and the PH coating of the present invention, the soda lime silica glass can be cleaned more easily. Optionally, such a barrier layer can be used.

On the other hand, one or more other layers or coatings, such as one or more functional coatings (such as anti-reflective coatings) or sodium ion barrier layers as described below may be sandwiched between the PH coating 24 and the substrate 22 between. For example, the PH coating 24 may be the outer layer or the outermost layer of a multi-layer coating existing on the substrate 22, or the PH coating 24 may be buried in such a multi-layer coating as one of the other layers except the outermost layer. In the layer. The so-called "outer layer" refers to a layer that receives sufficiently excited electromagnetic radiation, such as ultraviolet rays, to obtain a photoactive hydrophilic coating with sufficient photoactivity, but it is not necessarily photocatalytic. Preferably, the PH coating 24 is the outermost coating of the substrate 22.

As discussed above, the PH coating 24 need not have a level of photocatalytic activity that is approximately the same as that of self-cleaning coatings known in the past. For example, the photocatalytic activity of the PH coating 24 can be greater than or equal to 0 cm-1min-1 to less than or equal to 5×10-3cm-1min-1±2×0-3cm-1min-1, for example, less than or equal to 4× 10-3cm-1min-1, for example, less than or equal to 3×10-3cm-1min-1±2×10-3cm-1min-1, for example, less than or equal to 2×10-3cm-1min-1±2×10- 3cm-1min-1.

The PH coating 24 may include any coating material that is hydrophilic in light activation and can be deposited by CVD, spray pyrolysis, or MSVD. For example, but not limiting the present invention, the PH coating 24 may include one or more metal oxides, metal alloy oxides, or semiconductor metal oxides or metal alloy oxides, such as but not limited to titanium oxide, silicon oxide, and aluminum. Oxide, iron oxide, silver oxide, cobalt oxide, chromium oxide, copper oxide, molybdenum oxide, tungsten oxide, zinc oxide, zinc/tin alloy oxide, zinc stannate, strontium titanate and Its mixture or composition. The metal oxide and/or metal alloy oxide may include metal oxides, peroxides, or suboxides.

An exemplary PH coating 24 particularly suitable for the practice of the present invention is titanium dioxide. Titanium dioxide exists in amorphous or three crystalline forms, namely anatase, rutile and brookite crystalline forms. Anatase titanium dioxide has strong light-activated hydrophilicity, and at the same time has excellent chemical resistance and excellent physical durability. The rutile phase of titanium dioxide may also have photo-activated hydrophilicity. Mixtures or compositions of anatase and/or rutile and/or brookite and/or amorphous phase are all suitable for use in the present invention, provided that the composition has photoactivated hydrophilicity.

The PH coating 24 should have a sufficient thickness to provide an acceptable level of photoactivated hydrophilicity. There is no absolute value that makes the PH coating 24 "acceptable" or "unacceptable", because the level of acceptable photoactivatable hydrophilicity of the PH coating and the purpose and conditions of use of the PH-coated article and the selection and The performance standard that matches the stated purpose is closely related. However, as discussed above, the thickness of the PH coating 24 to achieve photo-activated hydrophilicity can roughly reach the thickness required for the traditional commercially acceptable level of photocatalytic self-cleaning activity. For example, the thickness of the PH coating 24 may be 10-5000 angstroms, and a thicker coating within this range may have photocatalytic self-cleaning activity and hydrophilicity. As the coating becomes thinner within this range, the photocatalytic self-cleaning activity generally decreases. As the coating thickness decreases in the range of 50-3000 angstroms, such as 100-1000 angstroms, such as 200-500 angstroms, such as 200-300 angstroms, the photocatalytic self-cleaning activity may not be measurable. Hydrophilicity still exists in the presence of electromagnetic radiation. It has been found that when the substrate 22 is a float glass plate and the PH coating 24 has a certain anatase titanium dioxide PH coating directly formed on the float glass plate by the CVD method, a thickness of 200-300 angstroms provides 0- The photocatalytic activity of 2×10-3cm-1min-1±2×10-3cm-1min-1, such as 1.8-2.8×10-3cm-1min-1, in order to remove the stearic acid test film, when the PH coating When exposed to UVA-340 light source with an intensity of 24W/m2 on the surface of the PH coating. This PH coating is also super-hydrophilic under the same rays. After 60 minutes of exposure under the UVA-340 light source, the contact angle of the water droplets is 4°±2° to 7°±2°. As understood by those skilled in the art, there may not be a uniform thickness over the entire area of the coating. Therefore, the thickness discussed here should be understood as the average thickness of the entire coating.

In another aspect of the present invention, the outer surface of the PH coating 24 of the present invention can be much smoother than previous hydrophilic self-cleaning coatings, while still maintaining its photoactivated hydrophilicity. For example, the RMS roughness of the coating 24, especially the outer surface or top surface of the coating, can be greater than or equal to 0 nm to less than 5 nm, such as less than or equal to thin coatings within the above range, such as 200-300 angstroms. 4.9nm, such as less than or equal to 4nm, such as less than or equal to 3nm, such as less than or equal to 2nm, such as less than or equal to 1nm, such as 0.3-0.7nm. For example, the RMS surface roughness of the 200-300 Angstrom PH coating just discussed above is 0.55-0.65nm, measured with an atomic force microscope.

In another aspect of the present invention, the PH coating 24 may have low visible light reflectivity. As used here, "visible light reflectivity" refers to the traditional chromaticity coordinate designation (R1)Y (light source C, 2° observation). For example, the visible light reflectivity of a PH-coated article may be 10-25%, such as 15-25%, such as 19-24%, such as 15-22%, such as less than or equal to 25%, such as less than or equal to 23%, For example, less than or equal to 20%.

In 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 may be substantially non-porous. The so-called "essentially non-porous" means that the coating is dense enough that the coating can withstand the traditional hydrofluoric acid drop test. In this drop test, two drops of 0.5% (vol%) hydrofluoric acid aqueous solution (HF) are placed on the coated sample, and a traditional laboratory watch glass is placed on the sample at room temperature for 8 minutes . After 8 minutes, remove the watch glass and check whether the coating is damaged. The denser PH coating 24 of the present invention provides greater protection for the underlying substrate against chemical attack than the previous self-cleaning coating with more holes, and it is also better than the previous self-cleaning coating with sol-gel coating. Harder and more resistant to scratches.

According to the present invention, a pH coating having a thickness of 10-500 angstroms, such as less than or equal to 400 angstroms, such as 200-300 angstroms, can be formed on the substrate 22 by any one or more of spray pyrolysis, CVD, or MSVD. In the spray pyrolysis method, the organic or metal-containing precursor is carried in an aqueous suspension such as an aqueous solution; in the CVD method, it is carried in a carrier gas such as nitrogen and sent to the surface of the substrate 22, while the substrate 22 is at a high temperature sufficient to decompose the precursor and form a PH coating 24 on the substrate 22. In the MSVD method, a metal-containing cathode target is sputtered in an inert or oxygen-containing atmosphere under negative pressure, and a sputter coating is deposited on the substrate 22. The substrate 22 can be heated during the coating process or after coating to crystallize the sputter coating to form the PH coating 24. Technical personnel who are familiar with this profession are very familiar with the traditional spray pyrolysis, CVD and MSVD methods, so they will not be detailed here.

Depending on the required characteristics of the coating 24 and the type of glass preparation method, each of these methods has advantages and limitations. For example, in the traditional float glass method, molten glass is poured into a molten metal (tin) bath, such as a tin bath, to form a continuous float glass ribbon. The temperature of the float glass ribbon in the tin bath is usually 1203°C (2200°F) (at the feed end of the bath) to 592°C (1100°F) (at the outlet end of the bath). The float glass ribbon is taken out from the tin bath and annealed in an annealing furnace before the glass is cut into glass sheets of the required length and width, that is, controlled cooling. The temperature of the float glass ribbon between the tin bath and the annealing furnace can be 480°C (896°F) to 580°C (1076°F), and the temperature of the float glass ribbon in the annealing furnace can be 204°C (400° F) to 557°C (1035°F) peak temperature. US 4466562 and 4671155 provide a discussion of the float glass process and are therefore incorporated by reference.

Among the float glass methods, CVD and spray pyrolysis methods may be superior to the MSVD method because they are more compatible with coating continuous substrates such as float glass ribbon at elevated temperatures. Exemplary GVD and spray pyrolysis coating methods are disclosed in US 4344986, 4393095, 4400412, 4719126, 4853257 and 4,971,843, which patents are hereby incorporated by reference.

In the practice of the present invention, one or more CVD coating equipment can be used in several places during the preparation of the float glass ribbon. For example, when the float glass ribbon is conveyed through the tin bath, after it is discharged from the tin bath, before entering the annealing furnace, when it is conveyed through the annealing furnace, or after it is discharged from the annealing furnace, CVD coating equipment can be used. Because the CVD method can coat moving float glass ribbons and can withstand the harsh environment related to the preparation of float glass ribbons, the CVD method is particularly suitable for providing PH coatings on float glass ribbons in molten tin baths. twenty four. US4853257, 4971843, 5536718, 5464657, and 5599387 disclose CVD coating equipment and methods that can be used in the practice of the present invention to coat float glass ribbon in a molten tin bath.

For example, as shown in FIG. 2, one or more CVD coaters 50 may be in the tin bath 52 above the molten tin pool 54. As the float glass ribbon 56 moves through the bath 52, the precursor material is sent to the top surface of the ribbon 56. The precursor material decomposes to form the PH coating with photoactivated hydrophilic activity of the present invention. For example, the precursor material can be selected to decompose to form a semiconducting metal oxide, such as a crystalline metal oxide. Exemplary precursor materials that can be used in the practice of the present invention to generate titanium dioxide PH coatings by CVD methods include, but are not limited to, titanium tetrachloride (TiCl4), titanium tetraisopropoxide (Ti(OC3H7)4) (hereinafter "TTIP") , Titanium tetrabutoxide, titanium tetraethoxide (Ti(OC2H5)4) (hereinafter referred to as "TTEt") and mixtures thereof. Exemplary carrier gases that can be used in the CVD method include, but are not limited to, air, nitrogen, oxygen, ammonia, and mixtures thereof. For the aforementioned metal-containing precursor, the concentration of the metal-containing precursor in the carrier gas may be 0.01-0.4% (volume), such as 0.05-0.4% (volume), such as 0.05-2% (volume), for example 0.05-1% (volume); but as those skilled in the art can understand, for other metal-containing precursors, these concentrations are variable.

For the CVD method (and the spray pyrolysis method discussed below), in the process of forming the PH coating 24 on the substrate, the temperature of the substrate 22 (for example, the float glass ribbon 56) should be such that the metal-containing precursor The material decomposes and generates within the range of photo-activated hydrophilic activity. The lower limit of this temperature range is largely affected by the decomposition temperature of the selected metal-containing precursor. For the aforementioned titanium-containing precursor, the lower limit of the temperature at which the substrate 22 is sufficiently decomposed for the precursor may be 400°C (752°F) to 500°C (932°F). The upper limit of this temperature range can be affected by the substrate coating method. For example, in the case where the substrate 22 is a float glass ribbon 56 and the PH coating 24 is applied to the float glass ribbon 56 in the molten tin bath 50 during the preparation of the float glass ribbon, the float glass ribbon The temperature of 56 can exceed 1000°C (1832°F). The float glass ribbon 56 can be drawn or sized (e.g., stretched or compressed) above 800°C (1472°F). If the PH coating 24 is applied to the float glass ribbon 56 before or during drawing, the PH coating 24 may crack or wrinkle when the float glass ribbon 56 is stretched or compressed, respectively. Therefore, when the float glass ribbon 56 is stable in size (except for thermal shrinkage during cooling), for example, when the soda lime silica glass is below 800°C (1472°F), the PH coating can be coated, and the float glass The belt 56 decomposes the metal-containing precursor at a certain temperature, for example, 400°C (752°F) or higher.

For spray pyrolysis, US 4719126, 4719127, 4111150 and 3660061 disclose spray pyrolysis equipment and methods that can be used with traditional float glass ribbon preparation methods, and are therefore incorporated by reference. Although the spray pyrolysis method is very suitable for coating the moving float glass ribbon like the CVD method, the spray pyrolysis method is more complicated than the CVD equipment and is usually used at the outlet end of the tin bath and the inlet end of the annealing furnace.

Exemplary metal-containing precursors that can be used in the practice of the present invention to generate PH coatings by spray pyrolysis include relatively water-insoluble organometallic reactants, specifically metal acetylacetonates, which are jet milled or wet milled to a particle size smaller than 10μm, and suspended in an aqueous medium with a chemical wetting agent. The metal acetylacetonate suitable for generating the PH coating of titanium dioxide is titanium oxyacetylacetonate (TiO(C5H7O2)2). The relative concentration of the metal acetylacetonate in the aqueous suspension is preferably 5-40% by weight of the aqueous suspension. The wetting agent can be any relatively low foaming surfactant, including anionic, nonionic or cationic compositions, although nonionic compositions are preferred. The wetting agent is usually added at 0.24% by weight, but it can also be 0.01-1% by weight or more. The aqueous medium is preferably distilled water or deionized water. Aqueous suspensions for the pyrolytic deposition of metal-containing films are disclosed in US 4719127, especially in column 2, line 16 to column 4, line 48, and are therefore incorporated herein by reference.

As understood by those skilled in the art, the bottom surface of the float glass ribbon directly placed on the molten tin (usually called the "tin side") has diffused tin on the surface, and the opposite surface (usually Called "air side") the tin side with different tin adsorption patterns. When the float glass ribbon is supported on tin, as mentioned above, the PH coating of the present invention can be formed on the air side of the glass ribbon by the CVD method in the float method; after it leaves the tin bath, it can be formed on the air side of the glass ribbon by CVD or spray pyrolysis. The air side of the float glass ribbon is formed; and/or after it is discharged from the tin bath, it is formed on the tin side of the float glass ribbon by the CVD method.

Regarding MSVD, US 4379040, 4861669, 4900633, 4920006, 4938857, 5328768, and 5492750 (all incorporated herein by reference) disclose a method for sputtering metal oxide films on substrates including glass substrates. MSVD equipment and methods. The MSVD method is generally not suitable for providing PH coating on the float glass ribbon during the preparation process of the float glass ribbon. The MSVD method requires negative pressure during the sputtering operation, and it is difficult to apply to the continuously moving float glass ribbon. form. However, the MSVD method is suitable for depositing the PH coating 24 on a substrate 22 such as a glass plate. The substrate 22 can be heated to 400°C (752°F) to 500°C (932°F), so that the MSVD sputter coating on the substrate crystallizes during the deposition process, so no subsequent heating operation is required. In some cases, the heating of the substrate during the sputtering process may not be preferable because an additional heating operation during the sputtering process can reduce productivity. On the other hand, the sputtered coating can be directly crystallized in the MSVD coating equipment without post-heating treatment using high-energy plasma, and it is not a preferred method due to the tendency of lowering the yield through the MSVD coater.

An illustrative method to obtain PH coatings by MSVD method (especially PH coatings with RMS roughness of 2nm or less and 300 angstroms or less) is to sputter the coating onto the substrate and then apply it from MSVD. Take out the coated substrate from the cladding device, and then heat the coated substrate to crystallize the sputtered coating to form a PH coating 24. For example, but not limited to the present invention, a titanium metal target can be sputtered at a pressure of 5-10 mTorr in an argon/oxygen atmosphere containing 5-50%, such as 20% oxygen, to sputter a desired thickness of titanium dioxide coating Deposited on the substrate 22. The newly deposited coating is not crystallized. The coated substrate is taken out of the coater and heated to 400°C (752°F) to 600°C (1112°F) for a period of time, which is sufficient to promote the formation of the PH crystal form of titanium dioxide and obtain PH activity. For example, the coated substrate can be heated at a temperature of 400°C (752°F) to 600°C (1112°F) for at least 1 hour. In the case where the substrate 22 is a glass plate cut from a float glass ribbon, the PH coating 24 may be sputter deposited on the air side and/or the tin side.

Subsequently, the substrate 22 deposited with the PH coating 24 by CVD, spray pyrolysis or MSVD may be subjected to one or more post-PH coating annealing operations. As can be understood, the annealing time and temperature can be affected by several factors, including the production of the substrate 22, the production 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 It is one layer of a multi-layer stack on the substrate 22.

Regardless of whether the PH coating is provided by CVD, spray pyrolysis, or MSVD, when the substrate 22 contains sodium ions that can migrate from the substrate 22 to the PH coating deposited on the substrate 22, the sodium Ions can inhibit or destroy the photoactivated hydrophilicity of the pH coating by generating inactive compounds while consuming titanium (for example, by generating sodium titanate) or by recombination of light-excited charges. Therefore, before the PH coating 24 is deposited, a sodium ion diffusion barrier layer (SIDB) can be deposited on the substrate. A suitable SIDB layer is disclosed in detail in US 6027766, so it is incorporated by reference and will not be discussed in detail here. As for post-coating heating, a sodium-containing substrate such as soda lime silica glass with a sodium barrier layer may be preferable. For the application of the PH coating of the present invention in a molten metal bath, a sodium barrier layer is optional.

When exposed to radiation in the ultraviolet range of the electromagnetic spectrum (for example, 300-395 nm), the PH coating of the present invention is preferably photoactivated and hydrophilic. The ultraviolet ray sources include natural light sources, such as sunlight; and artificial light sources, such as black light or ultraviolet light sources, such as the aforementioned UVA-340 light source.

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) may be deposited on the substrate 22. For example, the functional coating 46 may be deposited on the major surface 60 of the substrate 22 which is the opposite side of the surface 21. The functional coating 46 can be deposited by any conventional method, such as but not limited to spray pyrolysis, CVD, MSVD, sol-gel method and the like. For example, US 4584206 and 4900110 disclose methods and equipment for depositing a metal-containing film on the bottom surface of a glass ribbon using a CVD method, which are incorporated herein by reference. Such known equipment can be downstream of the molten tin bath of the float glass process to provide a functional coating under the glass ribbon, that is, on the opposite side of the PH coating of the present invention. On the other hand, one or more other CVD coaters can be placed in the tin bath to deposit the functional coating on or under the PH coating 24 of the float glass ribbon.

Fig. 3 shows an exemplary article prepared by the present invention in the form of an insulating glass (IG) unit 30. The insulating glass unit has a first pane 32 spaced from the second pane 34 by a gasket assembly (not shown), and the panes are fixed by a seal system to form a chamber between the two panes 32, 34. The first pane 32 has a first surface 36 (number 1 surface) and a second surface 38 (number 2 surface). The second pane 34 has a first surface 40 (number 3 surface) and a second surface 42 (number 4 surface). The first surface 36 may be the outer surface of the IG unit, that is, the surface exposed to the environment, and the second surface 42 may be the inner surface, that is, the surface that forms the inner side of the structure. Examples of IG units are disclosed in US 4193236, 4464874, 5088258 and 5106663, which are hereby incorporated by reference. As shown in FIG. 3, the PH coating 24 is preferably on the surface of number 1 or 4, preferably on the surface of number 1. The PH coating 24 reduces fogging and makes the IG unit 30 easier to clean and maintain.

One or more optional functional coatings 46 may be deposited on at least a portion of the number 2, 3, or 4 surface. As used herein, the term "functional coating" refers to a coating that can change one or more of the physical properties of the substrate deposited on it, such as optical, thermal, chemical or mechanical properties, during subsequent processing. It is not intended to be removed from the substrate. The functional coating 46 may have one or more functional coatings with the same or different compositions or functions. As used herein, the term "layer" or "film" refers to a coated area of a desired or selected coating composition. The film can be uniform, non-uniform, or with a gradient of compositional changes. When the outer surface or part (that is, the surface or part farthest from the substrate), the inner surface or part (that is, the surface or part closest to the substrate) and the part between the inner and outer surfaces have substantially the same composition, the film is "average". When going from the inner surface to the outer surface, or vice versa, one or more components of the film have substantially increasing fractions and one or more other components substantially decreasing fractions, the film is "gradient change" of". When the film is different from a uniform film or a gradient film, the film is "non-uniform." The "coating" is composed of one or more "films".

The functional coating 46 may be an electrically conductive coating, such as the conductive heating window coating disclosed in US 5653903 and 5028759, or a single film or multiple film coating that can be used as an antenna. Similarly, the functional coating 46 may be a solar control coating, such as a visible light, infrared light or ultraviolet light energy reflecting or absorbing coating. Examples of suitable solar control coatings can be found in the following patents: US 4898789, 5821001, 4716086, 461071, 4902580, 4716086, 4806220, 4898790, 4834857, 4948677, 5059295 and 5028759, also in US Patent Application 09/058440 turn up. Likewise, the functional coating 46 may be a low-emission coating. "Low-emission coating" allows visible light wavelength energy (such as 400-780nm) to be transmitted through the coating, while reflecting longer wavelength solar infrared light energy and/or thermal infrared light energy, usually aimed at improving the insulation performance of architectural glass windows . The so-called "low emissivity" refers to an emissivity of less than 0.4, preferably less than 0.3, and more preferably less than 0.2. Examples of low emissivity coatings are for example in US 4952423 and 4504109 and GB Found in 2302102. The functional coating 46 may be a single-layer or multi-layer coating, and may contain one or more metals, non-metals, semi-metals, semiconductors and/or alloys, compounds, composites, compositions, or blends thereof. For example, the functional coating 46 may be a single-layer metal oxide coating, a multi-layer metal oxide coating, a non-metal oxide coating, or a multi-layer coating. In addition, the functional coating may be an anti-reflective coating.

Examples of functional coatings suitable for use in the present invention are commercially available from PPG Industries, Inc. of Pittsburgh, Pennsylvania in the SUNGATE(R) and SOLARBAN(R) series of coatings. Such functional coatings usually include one or more anti-reflective coating films containing dielectric or anti-reflective materials, such as metal oxides or metal alloy oxides, which are preferably transparent or substantially transparent to visible light. The functional coating 46 may also include an infrared light reflective film containing reflective metals such as precious metals (such as gold, copper or silver or a combination or alloy thereof), and may contain a base film or barrier film on or under the metal reflective layer, such as titanium , As known in the profession.

The functional coating 46 can be deposited by any conventional method, such as but not limited to magnetron sputtering vacuum deposition (MSVD), chemical vapor deposition (CVD), spray pyrolysis (ie pyrolytic deposition), atmospheric pressure CVD (APCVD) , Low pressure CVD (LPCVD), plasma enhanced CVD (PEVCD), plasma assisted CVD (PACVD), thermal or electron beam vaporization, cathodic arc deposition, plasma spray deposition and wet chemical deposition (e.g. sol-gel, Mirror plating (silver, etc.). When the functional coating is applied to the PH coating side of the substrate, it is preferable to coat the functional coating in a tin bath before the PH coating. When the functional coating is on the opposite side 60 of the PH coating, the functional coating can be applied after the tin bath in the float glass process, as discussed above, for example by CVD or MSVD coating on the tin side of the substrate 22 on.

Although in the above discussion the PH coating is applied to the air side of the substrate and the functional coating is applied to the tin side of the substrate, it should be understood that the functional coating can be applied to the substrate such as floating in a tin bath. The air side of the glass ribbon is used, and then the PH coating is applied to the tin side of the substrate by any desired method, such as the method described above.

The advantages of the present invention over the sol-gel method for preparing self-cleaning coatings include that, unlike the usually thicker and porous self-cleaning coatings prepared by the sol-gel method, it can produce thin, dense coatings on the substrate. PH coating. Because the PH coatings of the present invention are thin, such as 500 angstroms or less, and preferably 300 angstroms or less, they are aesthetically acceptable as transparent coatings on glass substrates. Another advantage is that the method of providing the PH coating of the present invention does not require heating the substrate after the coating or coating precursor is applied, and reheating is required by the currently available sol-gel method. This not only enables the method to have lower cost and higher efficiency, such as not limited to lower equipment cost, lower energy cost, shorter production time, but also sodium ion migration and the sodium ion of the PH coating of the present invention The chance of poisoning is greatly reduced. In addition, the method of the present invention is easily applicable to the production of a PASC coating on a continuously moving substrate such as a float glass ribbon, while the currently available sol-gel method is not so easily applicable.

The following embodiments of the present invention are used to illustrate, but not to limit the present invention.

Example In a traditional tin bath, using a traditional CVD method, the deposition thickness is 232 angstroms on a 152" (386cm) float glass ribbon (3.3mm thick transparent glass) moving at a speed of 484in/min (1229cm/min) 48" (122cm) wide titanium dioxide PH coating (measured with ellipsometer and transmission data). The coating was formed from a precursor material of 0.07% (mol) titanium tetraisopropoxide in a nitrogen-containing carrier gas and applied at a glass ribbon temperature of 1220°F (659°C). The coated glass ribbon is then annealed, that is, cooled at a controlled rate, and then the sample is cut into 3" (7.5 cm) x 6" (15 cm) specimens. The crystalline structure of the deposited coating was determined to be anatase by X-ray diffraction. The photocatalytic activity of the coating is 1.8×10-3cm-1min-1, as measured by the traditional stearic acid test and chromaticity coordinates (luminescent body C, 2° observation): reflectance (R1) Y=19.43, x = 0.2741, y = 0.2774 and transmittance Y = 78.50, x = 0.3187, y = 0.3279.

In order to measure the photoactivated hydrophilicity of the coated article, the sample was used at 145°F with a dilute water cleaning solution (pH 2.9) of the DART 210 cleaner commercially available from Madison Chemical Inc., of Madison, Indiana under ultrasound. Clean for 20min. The sample was then cleaned with deionized water at room temperature, followed by a second ultrasonic cleaning in deionized water at 155°F for 10 minutes. Clean the sample again with deionized water at room temperature, and then blow dry with compressed nitrogen. Expose the sample to 24W/m2 ultraviolet rays generated by a UVA 340 lamp, and measure the contact angle of the water droplet with time. The water droplet contact angle was measured on the Rame-Hart Tele 102-00-115 goniometer, and the sample was in a horizontal (non-inclined) position. For each sample measured, the water droplet contact angle dropped from about 21-47° to about 4-11° after UVA-340 exposure for about 30 minutes, and dropped to about 3-7° after exposure for about 60 minutes.

The Taber abrasion test was performed on several samples with a CS-10F wheel weighing 1,000 grams, with 10 laps and 25 laps. The transmission haze of each sample was determined to be 0.0 using Pacific Scientific XL211 HazeGuard System. The Taber abrasion test was also performed on 5 samples according to the No. 18 test of ANSI Z 26.1-1983 (1000 cycles, 500 grams per round) program for anti-wear, and the scattered light increased by an average of 2.4%.

The samples were subjected to several traditional test methods, and the results are listed in Table 1 below. The results of film degradation are based on visual observation and reflection color measurement. The results of the contact angle were measured as described above.

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

Those skilled in the art can easily understand that various changes can be made to the present invention without departing from the principles disclosed above. Therefore, the specific embodiments described in detail here are only illustrative, rather than limiting the scope of the present invention. It is intended to give the full scope of the appended claims and any and all equivalents thereof.