Process for the production of photocatalytic coatings on substrates

Method for manufacturing a photocatalytic coating on a substrate {Process for the production of photocatalytic coatings on substrates}

1 is a graph of the photocatalytic activity of a coated glass produced by a process according to the invention as a function of the thickness of a titanium oxide layer;

2 shows an apparatus for on-line chemical vapor deposition of a coating film according to the present invention.

<backgroundart><p>The present invention relates to a method for producing a photocatalytically active coated substrate. In particular, the present invention relates to a method for producing a photocatalytically active coated glass and to such a coated glass.</p><p>It is known to deposit thin coatings having one or more layers exhibiting different properties on a substrate comprising a glass substrate. One advantageous among the various properties is the photocatalytic activity caused by photogeneration of hole-electron pairs in the semiconductor when the semiconductor is irradiated with light of a specific wavelength. Hole-electron pairs can be generated in sunlight and react in humid air to form hydroxy radicals and peroxy radicals on the surface of the semiconductor. These radicals oxidize organic grime on the surface. This property is useful for self-cleaning substrates, especially self-cleaning glass for windows.</p><p>Titanium dioxide can be an efficient photocatalyst and can be deposited on a substrate to form a transparent film with photocatalytic self-cleaning properties. The titanium oxide photocatalyst film is disclosed in European Patent Publication No. 0 901 991 A2, International Publication No. WO 97/07069, WO 97/10186, WO 98/41480, and literature [Reference: Abstract 735 of 187th Electrochemical Society Meeting (Reno, NV, 95-1, p.1102)] and magazines (New Scientist (26 August 1995, p.19)). According to International Publication No. WO 98/06675, there is a chemical vapor deposition method for depositing a titanium oxide film on a hot plate glass at a high deposition rate using a precursor gas mixture of an organic compound and titanium chloride as an oxygen source for forming a titanium oxide film. is described.</p><p>It has been thought that it is necessary to deposit a relatively thick titanium oxide film to provide good photocatalytic activity. For example, WO 98/41480 states that a photocatalytically active, self-cleaning coating must be sufficiently thick to provide an acceptable level of activity, such a coating having a thickness of at least about 200 Å, more preferably about It is stated that 500 angstroms or more is preferable (the measurement thickness range of the titanium oxide film prepared in Examples is all 400 angstroms to 2100 angstroms).</p><p>However, the problem with the relatively thick titanium oxide film is that the visible light reflectance is high and the visible light transmittance is low. This problem is well documented in the magazine [New Scientist] with regard to coated windscreens, which say that black velvet or some other material that does not reflect light into the coated windshield to reduce the high reflection effect. It is suggested that the instrument panel be covered with a different material.</p><p>The European Patent Application Laid-Open No. 0 901 991 A2 relates to a photocatalytic window glass coated with titanium oxide having a specific crystal structure, characterized in that specific peaks exist in an X-ray diffraction pattern. In this patent specification, the range of the film thickness is described (the specific examples all have a thickness range of 20 nm to 135 nm, and the thinner the film, the lower the photocatalytic activity than the thicker film). Also, while this patent specification suggests a deposition temperature range of 300°C to 750°C, a temperature of 400°C to 600°C is preferred, and in all of the specific examples, titanium dioxide is maintained at a temperature within or below this preferred temperature range. The layer is being deposited.</p></backgroundart><abstractproblem><p>The present inventors have found that by depositing a titanium oxide film at a higher temperature, particularly at a temperature of 600 DEG C or higher, a film exhibiting improved photocatalytic activity at a predetermined thickness can be obtained and the same photocatalytic performance can be obtained with a thinner film. Such thinner coatings advantageously reduce visible light reflectance, ultimately result in higher deposition temperatures, and improve durability, particularly resistance to abrasion and temperature cycling in humid atmospheres.</p></abstractproblem>

<p>Accordingly, the present invention relates to a photocatalyst of a coated surface of a substrate, comprising contacting the surface of the substrate, the temperature of which is maintained at 600° C. or higher, with a fluid mixture containing a titanium source and an oxygen source to deposit a titanium oxide film on the substrate surface. 5 x 10 active<sp>-3</sp>cm<sp>-1</sp>min<sp>-1</sp> and a visible light reflectance measured on the coated surface of 35% or less.</p><p>The temperature of the substrate is preferably maintained at 625°C to 720°C, more preferably 645°C to 720°C.</p><p>Advantageously, the fluid mixture contains titanium chloride as the titanium source and an ester other than the methyl ester. Accordingly, in a preferred embodiment, the present invention provides a photocatalytically active coated substrate comprising contacting the surface of the substrate with a fluid mixture containing titanium chloride and an ester other than methyl ester to deposit a titanium oxide coating having a thickness of less than 40 nm on the substrate. It provides a manufacturing method of</p><p>The manufacturing method may be performed by contacting the surface of the substrate with a fluid mixture when the temperature of the substrate is maintained at 600°C to 750°C.</p><p>Preferably, the ester is an alkyl ester in which the alkyl group has a β hydrogen (the alkyl group of the alkyl ester is a group derived from an alcohol in the synthesis of the ester, and the β hydrogen is bonded to the carbon atom β to the oxygen of the ether bond in the ester. hydrogen). Preferably, the ester is a carboxylate ester.</p><p>Suitable esters are C<sb>2 </sb>to C<sb>10 </sb>It may be an alkyl ester having an alkyl group, but preferably the ester is C<sb>2 </sb>to C<sb>4 </sb>It is an alkyl ester having an alkyl group.</p><p>Preferably, the ester is a compound of the formula RC(O)-OC(X)(X')-C(Y)(Y')-R', wherein R and R' are hydrogen or an alkyl group, and X , X', Y and Y' are monovalent substituents, preferably an alkyl group or a hydrogen atom, and at least one of Y and Y' is hydrogen).</p><p>Suitable esters that can be used in the process of the invention are ethyl formate, ethyl acetate, ethyl propionate, ethyl butyrate, n-propyl formate, n-propyl acetate, n-propyl propionate, n-propyl butyrate, iso propyl formate, isopropyl acetate, isopropyl propionate, isopropyl butyrate, n-butyl formate, n-butyl acetate and t-butyl acetate.</p><p>Preferably, the ester comprises an ethyl ester, more preferably the ester comprises ethyl formate, ethyl acetate or ethyl propionate. Most preferably, the ester comprises ethyl acetate.</p><p>The fluid mixture may be in liquid form, particularly in liquid form that is dispersed as a fine spray (this process is often referred to as spray deposition), but preferably the fluid mixture may be a gas mixture. A deposition method performed using a gas mixture as a precursor is often referred to as chemical vapor deposition (CVD). A preferred form of CVD is laminar flow CVD. However, turbulent flow CVD may also be used.</p><p>The method of the present invention can be practiced on multiple sizes of substrates, including sheet substrates, particularly cut glass sheets, or preferably continuous glass ribbons on-line during float glass production processes. Accordingly, preferably, the method of the present invention is carried out on-line during the float glass production process, and the substrate is a glass ribbon. If the method of the present invention is carried out on-line, it is preferably carried out while the glass ribbon is present in the float bath.</p><p>An advantage of carrying out the process of the present invention on-line is that the coatings deposited on-line are durable and tend to exhibit particularly good abrasion and chemical resistance.</p><p>On-line deposition is preferred, while other deposition methods may be conducted at substantially atmospheric pressure.</p><p>In a particularly preferred embodiment, a photocatalytically active titanium oxide layer is deposited on the surface of the glass substrate by contacting the surface of the substrate maintained at a temperature of 645° C. to 720° C., preferably 670° C. to 720° C. with a fluid mixture containing a titanium source. A method of making a durable photocatalytically active coated glass is provided, comprising shimming.</p><p>As described above, the present inventors have found that by depositing titanium oxide at high temperatures, it is possible to produce films with relatively high photocatalytic activity with respect to thickness, and since films with reduced thickness tend to exhibit lower reflectivity, the present invention The invention also provides novel products with advantageous combinations of high photocatalytic activity and medium or low light reflectance.</p><p>Accordingly, in another aspect, the present invention provides a photocatalytically active coated substrate comprising a substrate having a photocatalytically active titanium oxide film on one surface, wherein the photocatalytic activity of the coated surface is 5 × 10<sp>-3 </sp>cm<sp>-1</sp>min<sp>-1 </sp>to provide a photocatalytically active coated substrate, characterized in that the visible light reflectance measured on the coated surface is 35% or less. </p><p>A high photocatalytic activity is advantageous because the amount of contaminants (including dust) on the surface of the coating of the photocatalytically active coated substrate is reduced more rapidly than a substrate exhibiting a relatively low photocatalytic activity. Also, relatively fast removal of surface contaminants tends to occur at low levels of UV luminosity.</p><p>The photocatalytic activity for the purposes of the present invention is about 32 W/m in intensity at the surface of the coated substrate.<sp>2</sp>is determined by measuring the reduction rate of the integral absorbance of the infrared absorption peak corresponding to the CH stretch of a thin stearic acid film formed on the coated substrate under irradiation of UV light from a UVA lamp having a peak wavelength of 351 nm. Stearic acid can be formed on the coated substrate by spin casting a solution of stearic acid in methanol as described below.</p><p>Preferably, the photocatalytic activity of the coated surface of the substrate is 1 × 10<sp>-2</sp>cm<sp>-1</sp>min<sp>-1</sp> excess, preferably 3 x 10<sp>-2</sp>cm<sp>-1</sp>min<sp>-1</sp> it is excess</p><p>A low visible light reflectance is advantageous because it is less scattered than a high reflectance, especially for glass substrates, the low visible light reflectance often corresponds to the high visible light transmission required for architectural glass and especially automotive glass.</p><p>The coated substrate preferably has a visible light reflectance measured on the coated surface of 20% or less, more preferably 17% or less, and most preferably 15% or less.</p><p>In most embodiments of the present invention the substrate is substantially transparent, and in a preferred embodiment of the present invention the substrate comprises a glass substrate. Typically the glass substrate is a soda-lime glass substrate.</p><p>When the substrate is a soda-lime glass substrate or another alkali metal ion-containing substrate, the coated substrate preferably has an alkali metal ion blocking undercoating layer between the substrate surface and the photocatalytically active titanium oxide film. This reduces the tendency for alkali metal ions to migrate from the substrate to the photocatalytically active titanium oxide. This reduction is advantageous because it is well known that alkali metal ions have a detrimental effect on semiconductor oxide films and reduce their activity.</p><p>The alkali metal ion blocking undercoat layer may include a metal oxide, but preferably the alkali metal ion blocking undercoat layer is a silicon oxide layer. The silicon oxide may be silica, but not necessarily stoichiometric, with carbon (commonly referred to as silicon oxycarbide, deposited as described in British Patent Publication No. 2,199,848) or nitrogen (commonly referred to as silicon oxynitride); It may contain the same impurities.</p><p>It is advantageous that the alkali metal ion blocking undercoating layer is thin so as not to significantly affect the optical properties of the coating, particularly by reducing the transparency of the transparent coated substrate or by generating an interference color in reflection or transmission. A suitable thickness range is determined by the properties of the material (its refractive index) used to form the alkali metal ion blocking layer, but usually the alkali metal ion blocking undercoating layer is less than 60 nm thick, preferably less than 40 nm. Currently, the alkali metal ion blocking undercoat must always be thick enough to reduce or block migration of alkali metal ions from the glass to the titanium oxide film.</p><p>An advantage of the present invention is that although the photocatalytically active titanium oxide film is thin (due to the low visible light reflectance of the coated substrate), the coated substrate exhibits excellent photocatalytic activity. The titanium oxide film preferably has a thickness of 30 nm or less, more preferably 20 nm or less, and most preferably 2 nm to about 20 nm.</p><p>The present invention is also advantageous because the deposition of a thin titanium oxide film requires less precursor and the layers can be deposited in a relatively short time. A thin titanium oxide film also produces less interference colors in reflection or transmission. However, a particularly advantageous point is that the visible light reflectance of the thin titanium oxide film is low, which is particularly important when the coated substrate is coated glass. In general, the required visible light transmittance of the coated glass determines the thickness of the titanium oxide film.</p><p>Preferably, the coated surface of the substrate has a static water contact angle of 20 DEG or less. Freshly made or cleaned glass has a hydrophilic surface (an integer contact angle of about 40° or less indicates a hydrophilic surface), but organic contaminants rapidly adsorb to the surface, increasing the contact angle. A particular advantage of the coated substrate (especially the coated glass) according to the present invention is that it reduces the contact angle by reducing or destroying organic contaminants by UV light of a right wavelength, even if the coated substrate is contaminated. Another advantage is that the water is dispersed over the surface of the low contact angle, thus reducing the scattering effect of water droplets (e.g. from rain) on the surface, and removing any dust or other contaminants that are not destroyed by the photocatalytic activity of the surface. It tends to be washed out. The integer contact angle is the angle with respect to the meniscus of a droplet on the glass surface, and the diameter of a droplet of a known volume on the glass surface can be determined according to a known method and calculated using an iterative procedure.</p><p>Preferably, the coated substrate has a haze of 1% or less, which is advantageous because a clear view can be achieved through the transparent coated substrate.</p><p>In a preferred embodiment, the coated surface of the substrate exhibits abrasion resistance, whereby the coated surface exhibits photocatalytic activity even after being subjected to 300 strokes under the European standard wear test. Preferably, the coated surface exhibits photocatalytic activity even after being subjected to 500 strokes under the European standard wear test, more preferably the coated surface exhibits photocatalytic activity even after being subjected to 1000 strokes under the European standard wear test.</p><p>This is advantageous because the self-cleaning coated substrate of the present invention is often used as an externally exposed coating surface (coated glass having a glass coating surface as the outer surface of a window) on which the coating is susceptible to wear.</p><p>European standard abrasion test refers to the wear test described in European standard BS EN 1096 part 2 (1999) and involves reciprocating a felt pad on the surface of a sample at a set speed and pressure.</p><p>Even if the hydrostatic contact angle is reduced to 15° or less by irradiation of UV light (eg, peak wavelength 351 nm) after being subjected to the European abrasion test, the coated substrate according to the present invention still exhibits photocatalytic activity. To reach this contact angle after wear of the coated substrate, it is usually about 32 W/m on the surface of the coated substrate.<sp>2</sp>The intensity of the irradiation requires less than 48 hours of irradiation time.</p><p>Preferably, the haze of the coated substrate after being subjected to the European standard wear test is 2% or less.</p><p>Durable coated substrates according to the present invention also exhibit durability against wetting cycles, which is likely to exhibit similar effects on weathering. Accordingly, as a preferred aspect of the present invention, the coated surface of the substrate is durable to wetting cycles to such an extent that the coated substrate retains its photocatalytic activity even after being subjected to 200 wetting cycle tests. The wet cycle test herein refers to a test in which the coating is subjected to a temperature cycle of 35° C., 75° C., and back to 35° C. for 4 hours at near 100% relative humidity. If the hydrostatic contact angle is reduced to 15° or less as a result of irradiation with UV light after the test, the coated substrate is considered to retain photocatalytic activity.</p><p>As a further preferred aspect, the present invention has a coating comprising an alkali metal ion blocking undercoat layer and a photocatalytically active titanium oxide layer on one surface, and the coated surface maintains photocatalytic activity even after being subjected to 300 strokes under the European standard wear test. Provided is a durable photocatalytically active coated glass comprising a glass substrate having abrasion resistance to an extent. In this embodiment, the coated glass preferably has a visible light reflectance measured from the film side of 35% or less, and the photocatalytically active titanium oxide layer preferably has a thickness of 30 nm or less. Since, prior to the present invention, only relatively thick coatings were considered to exhibit good durability, it is surprising that thin coatings exhibit durability.</p><p>In a further aspect, the present invention is a coated glass comprising a glass substrate having a photocatalytically active titanium oxide film on one surface, wherein the photocatalytic activity of the coated surface of the glass is 4 × 10<sp>-2</sp>cm<sp>-1</sp>min<sp>-1</sp> Excess<sb>, </sb>preferably 6 x 10<sp>-2</sp>cm<sp>-1</sp>min<sp>-1</sp> Excess<sb>, </sb>more preferably 8 x 10<sp>-2</sp>cm<sp>-1</sp>min<sp>-1</sp> and a visible light reflectance of the coated glass measured on the coated surface of less than 20%.</p><p>The clad substrate according to the present invention is used in many fields, for example as a glazing comprising a composite glazing unit comprising a first glazing glazing of the clad substrate and a second glazing glazing spaced apart therefrom, for example, or It is used as a laminated glass comprising a coated glass layer, a polymer interlayer (eg polyvinylbutyral) and a second glass layer.</p><p>In addition to use in self-cleaning substrates (particularly self-cleaning glazing), the coated substrates of the present invention may also be useful for reducing concentrations of air pollutants. For example, coated glass under irradiation with UV wavelength (including UV wavelengths present in daylight) light can destroy atmospheric pollutants (eg, nitrogen oxides, ozone and organic pollutants) adsorbed on the coated surface of the glass. This use is particularly advantageous in prefabricated building areas (eg urban centers) where the concentration of organic pollutants is relatively high (especially under intense sunlight) and the use surface area of the glass is relatively high. In addition, coated glass (with a covering surface on the inside) can be used to reduce the concentration of air pollutants in buildings, particularly office buildings where the concentration of air pollutants is relatively high.</p><p>The present invention is illustrated by the following drawings, which are not intended to limit the invention.</p><p>In Figure 1, the coated glass is produced by an on-line CVD process as described in the following examples. A circle (1) relates to a titanium oxide layer deposited using titanium tetrachloride as a titanium precursor, and a cross mark (2) relates to a titanium oxide layer deposited using titanium tetraethoxide as a titanium precursor.</p><p>The encapsulation layer can be applied on-line to the glass substrate by chemical vapor deposition during the glass manufacturing process. 2 shows an apparatus 10 comprising a float zone 11 , a furnace 12 and a cooling zone 13 , useful for on-line production of the coated glass article of the present invention. The float section 11 has a bottom 14 comprising a molten tin bath 15 , a top wall 16 , side walls (not shown) and an end wall 17 , which together form a seal to form a sealed section 18 . makes A non-oxidizing atmosphere is maintained in the enclosed area to prevent oxidation of the tin bath 15 . During operation of this apparatus 10 molten glass 19 is cast on furnace 20, from which it flows down a metering wall 21 and then moves down to the surface of a tin bath 15 to form a float glass ribbon ( 37 ), which is removed by lifting rolls 22 and conveyed through a furnace 12 and then a cooling zone 13 .</p><p>A suitable gas, eg, a gas comprising 2% by volume nitrogen and hydrogen, is introduced into zone 18 via conduit 23 operatively connected to manifold 24 to enter the float zone 11 non-oxidatively. keep the atmosphere The non-oxidizing gas is sufficient to compensate for the gas loss (a portion of the non-oxidizing atmosphere flows down the end wall 17 and leaves the zone 18) and the conduit at a rate sufficient to maintain a pressure slightly above atmospheric pressure. It is introduced from (23) into zone (18). The tin bath 15 and the enclosed zone 18 are heated by radiant heat radiated downward from the heater 25 . Heating zone 18 is usually maintained at a temperature of about 1330° F. to 1400° F. (721° C. to 760° C.). The atmosphere in the furnace 12 is generally air, and the cooling zone 13 is not sealed. A fan 26 is used to blow ambient air onto the glass.</p><p>Apparatus 10 also includes applicators 27 , 28 , 29 and 30 successively positioned in float zone 11 over float glass ribbon 37 . A precursor gas mixture for each encapsulation layer is supplied to each applicator, which in turn directs the precursor gas mixture to the hot surface of the float glass ribbon 37 in turn. The temperature of the float glass ribbon 37 is highest at the location of the applicator 27 closest to the furnace 20 and lowest at the location of the applicator 30 closest to the furnace 12 .</p><p>The invention is further illustrated by the following examples, wherein a coating is deposited on a moving ribbon of float glass during the glass making process using laminar flow chemical vapor deposition in a float bath. In an embodiment, a two-layer coating is deposited on a glass ribbon.</p><p>All gas volumes were measured at standard temperature and pressure unless otherwise noted. The thickness dimension used for the layer was measured by using a high-resolution scanning electron microscope and by optical modeling the reflection and transmission spectra of the coated glass. The thickness of the coating was measured with an uncertainty of about 5%. The transmittance and reflectance of the coated glass were measured using a Hitachi U-4000 spectrophotometer. a, b and L of the transmitted and/or reflective colors of the glass referred to herein<sp>*</sp> Values refer to CIE Lab colors. Visible light reflectance and visible light transmittance of the coated glass were measured according to the ISO 9050 standard [Parry Moon Airmass 2] using a D65 light source and a standard CIE 2° observer. The haze of the coated glass was measured by WYK-Gardner. It was measured using a haze guard + haze meter.</p><p>The photocatalytic activity of the coated glass was measured from the reduction rate of the area of the infrared peak corresponding to the CH stretch of the stearic acid film present on the coated surface of the glass under UVA light irradiation. The stearic acid film was prepared in a solution of methanol stearate (8.8 × 10<sp>-3</sp>moldm<sp>-3</sp>) 20 μl was spin-casted on the coated surface of the glass at 2000 rpm for 1 minute to form a size of 7 to 8 cm 2 on the glass sample. The infrared spectrum was measured as transmittance, and the peak corresponding to the CH stretch of the stearic acid film (about 2700 to 3000 cm<sp>-1</sp>) was measured, and the corresponding peak area was determined from the adjustment curve of the peak area to the peak height. A UVA-351 lamp with a peak wavelength of 351 nm on the coated surface of the glass and an intensity of about 32 W/m2 at the coated surface of the glass [product of Q-Panel Co., Cleveland, Ohio] was investigated with Photocatalytic activity in the present specification is the reduction rate of the IR peak area (unit: cm<sp>-1</sp>min<sp>-1</sp>) or t, which is the UV exposure time it takes to reduce the peak height of a peak in the wavelength area to 10% of its initial value.<sb>90%</sb>(unit: minutes). </p><p>The hydrostatic contact angle of the coated glass was determined by irradiating the coated glass for about 2 hours (or otherwise) using a UVA351 lamp and then measuring the diameter of a water droplet (volume of 1 to 5 μl) placed on the coated side of the glass.</p><p><u>Examples 1 to 15</u></p><p>A 1 mm thick soda lime float glass ribbon is coated with a two-layer coating as the ribbon is advanced over the float bath at a glass temperature of about 650° C. to about 670° C. while advancing at a furnace speed of 300 m/hr. The atmosphere of the glass bath consists of a flowing gas mixture of nitrogen and 9% hydrogen at a bath pressure of about 0.15 mbar.</p><p>Layer 1 (the first layer deposited on the glass) is a silicon oxide layer. Layer 1 is illustrated in British Patent Application Publication No. 1 507 966 (specifically illustrated in FIG. 2 and page 3 line 73 through page 4 75), which shows the path of movement of the gas mixture onto the glass surface of about 0.15 m. In the direction of movement of the glass, parallel to the surface of the glass using an applicator as described in the row) monosilane (SiH<sb>4</sb>, 60 ml/min), oxygen (120 ml/min), ethylene (360 ml/min), and nitrogen (8 l/min) were deposited by contacting and flowing a gas mixture. Extracted at about 0.9 to 1.2 mbar. A glass ribbon is coated along a width of about 10 cm at a temperature of about 670°C. The thickness of the silica layer is about 20-25 nm.</p><p>Layer 2 (second deposited layer) is a titanium dioxide layer. Layer 2 is a gas mixture each of a gas stream comprising titanium tetrachloride in a flowing nitrogen carrier gas, a gas stream comprising ethyl acetate in a flowing nitrogen carrier gas and a nitrogen bulk stream at 8 l/min (flow rate measured at 20 psi). After mixing, the gas mixture is fed (via a line maintained at about 250° C.) to an applicator consisting of an oil-cooled dual flow applicator to deposit. The pressure of the nitrogen carrier and bulk nitrogen gas is approximately 20 lb/in.<sp>2</sp> am. The gas mixture contacts and flows up and down along the glass ribbon parallel to the glass surface. The path of movement of the gas mixture is about 0.15 m downstream and about 0.15 m upstream, and the extraction takes place at about 0.15 mbar. Titanium tetrachloride and ethyl acetate are included in each flowing nitrogen carrier gas stream by passing nitrogen through a bubbler containing either titanium tetrachloride or ethyl acetate. The flow rates of the nitrogen carrier gas are given in Table 1 (the flow rates were measured at 20 psi). The titanium tetrachloride bubbler was maintained at 69°C and the ethyl acetate bubbler at 42°C. The calculated flow rates of nested titanium tetrachloride and nested ethyl acetate for each of Examples 1 to 15 are also presented in Table 1.</p><p>Then, the properties of the two-layer coating are measured. The thickness of the layer (2) (titanium oxide layer) for Examples 1 to 15, and the visible light reflectance measured at the covering surface, L<sp>*</sp> and haze of the coated glass are shown in Table 2. The haze of each coated glass is 0.2% or less.</p><p>Then, the photocatalytic activity and the hydrostatic contact angle of the coated glass are measured. Initial peak height and initial peak area, photocatalytic activity, integer contact angle and t of the IR peak corresponding to the stearic acid CH stretch for Examples 1 to 15<sb>90%</sb>are presented in Table 3. The thickness of the titanium oxide layer surprisingly has little effect on the photocatalytic activity.</p><p><u>Examples 16-19</u></p><p>Examples 16 to 19 have a bath pressure of about 0.11 mbar, an extraction pressure of about 0.7 mbar for depositing a silica undercoat layer (Layer 1), a titanium tetrachloride bubbler maintained at about 100° C., and an ethyl acetate bubbler was maintained at about 45°C, and the delivery line was maintained at about 220°C, but under the same conditions as Examples 1 to 15.</p><p>The calculated flow rates of nitrogen carrier gas, and embedded titanium tetrachloride and embedded ethyl acetate for each of Examples 16 to 19 are presented in Table 1.</p><p>The calculated thickness of the layer 2 (titanium oxide layer) for each of Examples 16 to 19, and the visible light reflectance measured at the covering surface, L<sp>*</sp> and haze of the coated glass are shown in Table 2. </p><p>Initial peak height and initial peak area of the IR peak corresponding to the stearic acid CH stretch for each of Examples 16 to 19, photocatalytic activity, t<sb>90%</sb> and integer contact angles are given in Table 3. </p><p>The photocatalytic activity of Examples 16-19, despite the thicker (and therefore more reflective) titanium oxide film, does not significantly increase over the photocatalytic activity of Examples 1-15.</p><p><tables id="1"><img file="KR20070068488A_D0001.tif" /></tables></p><p><tables id="2"><img file="KR20070068488A_D0002.tif" /></tables></p><p><tables id="3"><img file="KR20070068488A_D0003.tif" /></tables></p><p><u>Examples 20 to 27</u></p><p>Examples 20 to 27 were prepared from a gas mixture containing titanium tetraethoxide embedded in a nitrogen carrier gas by passing a nitrogen carrier gas through a bubbler containing titanium tetraethoxide maintained at 170° C. ) was carried out under the same conditions as in Examples 1 to 15 except for depositing. The flow rates of nitrogen carrier gas (measured at 20 psi) and flow rates of titanium tetraethoxide for each of Examples 20-27 are presented in Table 4. The flow rate of bulk nitrogen gas is 8.5 L/min (measured at 20 psi).</p><p>Then, the properties of the two-layer coating are measured. Table 5 shows the thickness of the layer 2 (titanium oxide layer) for each of Examples 20 to 27, and the visible light reflectance and haze of the coated glass measured on the coated surface. The haze of each coated glass is 0.7 % or less.</p><p>Then, the photocatalytic activity and the hydrostatic contact angle of the coated glass are measured. Initial peak height and initial peak area of the IR peak corresponding to the stearic acid CH stretch for each of Examples 20-27, photocatalytic activity, t<sb>90%</sb> and integer contact angles are given in Table 6. </p><p><u>Examples 28 and 29</u></p><p>Examples 28 and 29 were carried out under the same conditions as Examples 20 to 27, except that the titanium tetraethoxide bubbler was maintained at 168° C. and the bath pressure was 0.11 mbar. Data for Examples 28 and 29, which are comparable to the data of Examples 20-27, are presented in Tables 4, 5 and 6.</p><p><tables id="4"><img file="KR20070068488A_D0004.tif" /></tables></p><p><tables id="5"><img file="KR20070068488A_D0005.tif" /></tables></p><p><tables id="6"><img file="KR20070068488A_D0006.tif" /></tables></p><p><u>Examples 30 to 42</u></p><p>In Examples 30-42, a two-layer coating was deposited onto a float glass ribbon along a total width of about 132 inches (3.35 m) in a float bath during a float glass manufacturing process using online CVD. The apparatus used to deposit this coating is shown in FIG. 2 . The atmosphere of the float bath contains nitrogen and 2% by volume hydrogen. The pressure of the bath is 0.15 mbar.</p><p>The two-layer coating consists first of a silicon oxide layer deposited on a float glass ribbon and a titanium oxide layer deposited on the silicon oxide layer. As the precursor compound of the gas mixture used to deposit the film, the same as those used in Examples 1 to 15 were used. The deposition temperature of the layers is varied by using different applicators 27 , 28 , 29 and 30 (see FIG. 2 ). The temperature of the applicator 27 closest to the hearth was the highest, and the temperature of the applicator 30 closest to the lehr was the lowest. In Examples 30-33 and 42, two applicators (applicators 28 and 29 in Examples 30-33, and applicators 27 and 28 in Example 42) were used to deposit the silicon oxide film. used] is used. The advantage of using two applicators for depositing the silicon oxide layer is that the manufacturing process time can be further extended.</p><p>The gas mixture used to deposit the silicon oxide layer in Examples 30-41 consisted of the following flow rates of gases: helium (250 l/min), nitrogen (285 l/min), monosilane (2.5 l/min), Ethylene (15 L/min) and Oxygen (10 L/min). In Example 42, the same gas and flow rates were used except for monosilane (2.3 l/min), ethylene (13.8 l/min), and oxygen (9.2 l/min). In Examples 30-42, when two applicators were used to deposit the silicon oxide layer, the flow rates described above were used for each applicator.</p><p>The deposition temperatures used in Examples 30-42 (ie, the temperature of the float glass ribbon under the applicator corresponding to each of applicators 27-30) are shown in Table 7. The temperatures in Table 7 have an uncertainty of about ±50°F (±28°C). The extraction pressure of each applicator is about 2 mbar.</p><p><tables id="7"><img file="KR20070068488A_D0007.tif" /></tables></p><p>Titanium tetrachloride (TiCl<sb>4</sb>) and ethyl acetate were contained in each nitrogen/helium carrier gas stream. TiCl<sb>4</sb>A thin-film evaporator is used to evaporate the TiCl<sb>4 </sb>The liquid is held in a pressurized vessel (head pressure about 5 psi) and the liquid is fed to a metering pump and a Coriolis forced flow metering system. A metered flow of precursor is then introduced into a thin film evaporator at 110°F (43°C). Then, TiCl<sb>4</sb>is encapsulated in a carrier gas (helium) and delivered in a line downstream of the mixing point maintained at 250°F (121°C). Ethyl acetate is delivered in a similar manner. That is, the ethyl acetate liquid is held in a pressurized vessel (head pressure about 5 psi) and the liquid is delivered to a metering pump and a Coriolis forced flow metering system. A metered flow of precursor is then introduced into a thin film evaporator at 268° F. (131° C.). The evaporated ethyl acetate is then entrained in a carrier gas (helium/nitrogen mixture) and delivered in a line downstream of the mixing point maintained at about 250°F (121°C).</p><p>TiCl<sb>4</sb>and ethyl acetate gas stream to form a gas mixture used to deposit the titanium oxide layer. This mixing is done just before the applicator.</p><p>Linear velocity of float glass ribbon in Examples 30-42, deposition temperature of silicon oxide, deposition temperature of titanium oxide layer, He/N<sb>2</sb> Flow rate of bulk carrier gas and TiCl<sb>4</sb> and the flow rates of ethyl acetate are shown in Table 8.</p><p>After the coated float glass ribbon is cooled and cut, the optical properties and photocatalytic activity of the samples are measured. Table 9 presents the optical properties of the sample at the time of haze, transmission and reflection (visible light transmittance/reflectance and color coordinates measured using the LAB system). Coated glass is abrasive tested according to BS EN 1096. First, a sample having a size of 300 mm × 300 mm is firmly fixed to the test bed at every four corners so that the sample cannot move. Thereafter, an unused felt pad cut to size as described in the standard method [BS EN 1096 Part 2 (1999)] is mounted on the test finger, and the test finger is pressed against the glass surface. The load pressure of the test finger is set to 4N, and the test is started. The fingers are reciprocated with 500 strokes along the specimen at a rate of 60 strokes/min ± 6 strokes/min. Upon completion of the polishing in this way, the sample is separated and examined for optical and photocatalytic activity. If the transmittance changes to ±5% or less when measured at 550 nm after polishing and the coated substrate maintains the photocatalytic activity, the sample is considered to have passed the test, and maintaining the photocatalytic activity is tested by UV light for 2 hours It means that the hydrostatic contact angle is reduced to 15° or less even after the</p><p>The glass is also subjected to a wet cycle test in which the coating is treated by a temperature cycle of 35° C. to 75° C. and back to 35° C. for 4 hours at a relative humidity of about 100%. </p><p>Coated glass as prepared, coated glass after UV irradiation for 130 minutes (UVA 351 mm lamp of about 32 W/m 2 ), and coated glass after 300 strokes, 500 strokes and/or 1000 strokes under European standard abrasive tests The integer contact angles of are given in Table 10. The contact angle of the polished sample was measured after irradiation for 2 hours.</p><p>1330 Samples deposited at elevated temperatures between 1250°F (721°C and 677°C) retain photocatalytic activity even after 1000 European standard abrasive strokes or 200 wetting cycles. t for coated glass as manufactured, coated glass after 300 strokes, 500 strokes and/or 1000 strokes and coated glass after 200 wetting test cycles under European standard abrasive tests<sb>90%</sb>Table 11 shows the photocatalytic activity expressed as . In Table 11, the term "active" means t<sb>90%</sb>was not measured, indicating that the coated glass is photocatalytically active.</p><p><tables id="8"><img file="KR20070068488A_D0008.tif" /></tables></p><p><tables id="9"><img file="KR20070068488A_D0009.tif" /></tables></p><p><tables id="10"><img file="KR20070068488A_D0010.tif" /></tables></p><p><tables id="11"><img file="KR20070068488A_D0011.tif" /></tables></p>

<p>According to the present invention, there is provided a method for producing a photocatalytically active coated substrate having good durability, high photocatalytic activity and low reflectance of visible light.</p>