MXPA99001459A - Method of depositing tin oxide and titanium oxide coatings on flat glass and the resulting coated glass - Google Patents

Abstract

A chemical vapour deposition process for laying down a tin or titanium oxide coating on hot flat glass through the use of an organic oxygen containing compound and the corresponding metal tetrachloride. The organic oxygen compound is preferably an ester having an alkyl group with a&bgr;hydrogen in order to obtain a high deposition rate. Because of the high deposition rates attainable, typically at least 130Å/second, the process is suitable for depositing coatings of substantial thickness on a moving ribbon of float glass during the glass production process.

Description

METHOD FOR DEPOSITING TEXTILE OXIDE COATINGS AND TITANIUM OXIDES IN FLAT GLASS AND GLASS WITH RESULTING COATING BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION The present invention relates to a process for depositing coatings of titanium oxide and tin oxides on a flat glass substrate, and the resulting coated glass. More particularly, the present invention relates to a chemical vapor deposition process for producing titanium oxide and tin oxide coatings in flat glass using a precursor coating gas mixture comprising the corresponding metal tetrachloride and an organic oxidant. . 2. Related art Titanium oxide and tin oxide coatings have been proposed for application in glass containers, for example bottles, to improve the mechanical strength of the containers. It has also been proposed to apply coatings of titanium oxide and tin oxide on flat glass to modify the characteristics of glass for architectural use. The titanium oxide coatings represented by vacuum (by reactive evaporated oxide) are applied as components of multi-layer infrared reflective coatings by evaporating oxide, but they are also deposited by pyrolysis with a doping material as an infrared or electroconductive reflective coating. British patent specification 1 115 342 describes a process for producing glass containers with good inherent strength and good resistance to abrasion by spraying the containers, when they are still hot by their manufacturing process, with a solution or dispersion of stannic chloride (that is, tin tetrachloride) in an organic liquid, with isopropyl alcohol being preferred. A small amount of titanium chloride can be incorporated as a modifier. The liquid solution is fed to atomizers, which can be of the pressure jet variety, located on both sides of a tunnel on a conveyor belt for hot glass bottles to produce a "simple" simple liquid reagent mist in such a way that a layer of liquid forms on all the outer surfaces of the bottles where it reacts to form a layer of tin oxide.

The British patent specification 1 187 784 describes an improvement of the process described in the British patent specification 1 115 342 and apparently more suitable for incorporation in an automatic manufacturing process of glassware, without interfering with the normal execution of said process and without requiring additional supervision. The specification proposes to treat glass containers, at high temperature, with a liquid solution of an organic tin compound "compound that has properties such that upon application of heat it decomposes into two materials, one being an organic compound of tin with high decomposition temperature that reacts with the surface of the glass to produce a diffusion layer of tin oxide inside the surface of the glass, while the other is a volatile tin compound, in such a way that a substantial proportion of vapor is produced of said compound, after subjecting the containers to heat treatment, in such a manner as to cause such a reaction between the glass on at least the surfaces of the containers and the tin compounds ". The material used to treat the glass containers can be provided by reacting tin tetrachloride with organic substances containing carbonyl groups of moderate activity, for example, organic esters of ethyl, n-propyl, isopropyl, n-butyl and isobutyl alcohols with acids acetic, propionic and butyric, the resulting solution can be sprayed, in the presence of the ambient atmosphere, in hot containers, for example, in the form of a fine mist after they leave the forming machine and before they enter the annealing tunnel. British patent specification 1 187 783 describes a process analogous to that described in 1 187 784 in which an organic titanium compound is sprayed onto hot glass containers in place of the organic tin compound. The organic tin compound can be produced analogously to the organic tin compound by reacting titanium tetrachloride with an organic ester, for example, n-butyl acetate. Again, the resulting solution is sprayed onto the glass in the ambient atmosphere of the vessel's production line. It has also been proposed to use tin tetrachloride, applied either as a liquid spray or, more recently, in gaseous form as to apply an oxide coating to hot flat glass to form an electroconductive coating, which reflects the infrared rays on the surface of the glass hot; Water is used to hydrolyze tin tetrachloride and as an oxygen source for the formation of tin oxide. The processes that involve the use of reagents in gaseous form is called (also called CVD processes or chemical vapor deposition) have certain advantages over the spray processes for the coating of flat glass, especially when the reagents can be mixed before the application to glass. Unfortunately, tin tetrachloride reacts easily with water, so that the previous proposals to use tin tetrachloride and steam in gaseous form have generally involved the supply of gases separately to the surface of the glass and mix them while they are in contact with the glass. The British patent specification 2 044 137A relates to a process in which discrete laminar flows of each reagent are formed and are projected onto a hot glass substrate by joining the flows in tangential and reciprocal contact on the glass. Titanium tetrachloride can be used as one of the gaseous reactants instead of tin tetrachloride, to form a titanium oxide coating. The patent also suggests supplying hydrogen to one of the gas streams to attenuate the violent reaction between tin tetrachloride and water vapor. This can be done either by direct addition of gaseous hydrogen, or by the addition of methanol, which allegedly reacts in situ to produce the desired hydrogen gas. British patent specification 2 026 454B discloses a process in which the coating chamber is placed by a hot float glass band as it advances from the float bath and the successive gas flows or (1) the previously heated nitrogen transport gas , (2) tin tetrachloride entrained in the pre-heated nitrogen and (3) air, water vapor and phlorhydric acids are introduced into the coating chamber to flow along the surface of the glass substrate being coated as a layer substantially free of turbulence. The patent specifies the concentration of water vapor and tin tetrachloride in the gaseous medium on the glass. European patent specifications 0 365 239B1 and 0 376 240B1 describe a method and apparatus for depositing a tin oxide coating on a hot glass strip. It is caused that a first gaseous flow of tin tetrachloride in preheated dry air flows along the surface of the hot glass band advancing below the coating chamber, a second turbulent flow of hydrofluoric acid and steam introduced into the glass. the coating chambers at right angles to the plane of the glass and the direction of flow of the first gas flow, and the first and second gas flows being drawn through the coating chamber onto the glass under the turbulent flow conditions. The method and apparatus can also be used to apply a coating of titanium oxide using titanium tetrachloride in place of tin tetrachloride. U.S. Patent 4 590 096 describes a process in which a coating solution comprising a substantially solvent-free mixture of an organo-tantalic chloride and a reactive soluble organic fluoride compound omissable with the organo-tannic chloride is introduced into a flow of previously heated conveyor gas containing sufficient water vapor, such that the relative humidity of the gas flow at 18 ° C is approximately 6% to approximately 100%. The resulting gas flow is passed over a hot glass surface to deposit a tin oxide coating contaminated with fluoride on the hot glass. A wide range of organotin compounds can be used, and the possibility of using tin tetrachloride is mentioned. In the same way, a wide range of organic fluoride compounds can be used, including oxygen-containing compounds, for example trifluoroacetic acid and ethyltrifluoroacetate. Some of the fluoride-containing doping compounds have limited solubilities in the organotin compounds used, and an optional solubilizer can be used to increase the solubility of the fluoride doping compound in the organotin compound; Acetic anhydride, ethyl acetate, hexane, methyl isobutyl ketone and butylaldehyde are listed as non-limiting examples of the solubilizers that may be employed. However, the United States patent, in the same way as the other patents that use chemical vapor deposition methods to deposit a metal oxide from a gaseous metal tetrachloride, uses water vapor as the source of oxygen. U.S. Patent 4,751,149 issued to Vijaykumar et al. refers to the deposition of zinc oxide coatings by chemical vapor deposition at low temperature (60 ° to 350 °, preferably 100 ° to 200 °) on heat-sensitive photoconductive substrates, and proposes to deposit zinc oxide coatings from an organic zinc compound and an oxidant, which may be an organic compound containing oxygen, for example, an ester, and an inert carrier gas. Although the patent is not completely clear, it apparently proposes the introduction of separate flows of the organic zinc compound and the oxidant into the deposition chamber, and certainly there is no proposal to premix these components prior to delivery to the coating chamber. U.S. Patent 4,731,256 and European Patent Application 0 186 481 relate to improved liquid coating compositions for producing tin oxide coatings doped with high quality fluoride. U.S. Patent 5,401,305 relates to a composition for coating glass by chemical vapor phase replacement comprising a mixture of a metal oxide precursor, a silicon dioxide tetraertilorthosilicate, and an accelerant, eg, phosphite of triethyl, with added atmospheric oxygen reacting to form the metal oxide deposited on the glass substrate, an organic tin chloride (defined to include tin tetrachloride) is used as a source of tin, an organic fluoride compound, which can be a ester, for example as a fluoride source, and, optionally, an ester is present to stabilize the liquid. In each case, the liquid composition is vaporized in a transport gas stream containing oxygen for supply to the hot glass, presumably serving the oxygen gas as the oxygen source for the formation of the tin oxide coating. U.S. Patent 5,124,180 relates to a CVD method for producing metal oxide coatings containing fluoride on substrates and an apparatus for use in said method, wherein a precursor of metal oxide and water or alcohol as an oxygen source they are supplied separately to a coating chamber in the form of steam and are mixed just before deposition in the substrate. It would be advantageous to provide a method for depositing tin oxide or titanium coatings by a CVD process applied to hot flat glass using a pre-mix of the corresponding metal tetrachloride as a low cost reagent and an oxygen source without premature reaction between the metal tetrachloride and the source of oxygen (previously water) that results in the formation of metal oxide in the coating equipment with consequent problems and efficiency. It would be particularly advantageous if the method would allow deposition of the coating at high speeds, allowing a required coating thickness to be deposited on a moving glass strip during the glass production process. SUMMARY OF THE INVENTION According to the present invention, a chemical vapor deposition process is provided to place a tin oxide or titanium oxide coating on a hot glass substrate using a precursor gas mixture containing the tetrachloride. corresponding metal and a source of organic oxygen, without the requirement to influence water vapor and the consequent risk of premature reaction.

The present invention provides a process for depositing a coating of tin oxide or titanium oxide on a hot flat glass comprising the steps of (a) preparing a precursor gas mixture containing the corresponding metal tetrachloride and a compound containing organic oxygen as an oxygen source for the formation of the metal oxide, (b) maintaining the precursor gas mixture at a temperature lower than the temperature at which the metal tetrachloride reacts to form the metal oxide while supplying the mixture to an aperture of the metal oxide. coating chamber on the hot glass, (c) introducing the precursor gas mixture into the coating chamber, whereby the mixture is heated to cause the deposition of the corresponding metal oxide incorporating oxygen of the organic compound on the hot glass surface . It is surprising that a wide range of organic compounds containing oxygen can be used as the source of oxygen, without requiring the presence of water vapor or gaseous oxygen, even compounds normally considered as reducing agents instead of oxidizing agents, for example, alcohols. However, the preferred organic compounds are carbonyl compounds, especially esters; and particularly good results have been obtained using esters having an alkyl group with a β-hydrogen will normally include from 2 to 10 carbon atoms. It is preferred to use organic compounds, especially esters, containing from 2 to 10 carbon atoms, since the larger molecules tend to be less volatile and, therefore, less convenient to be used in the CVD process of the present invention . Particularly preferred esters for use in the practice of the present invention include ethyl formate, ethyl acetate, ethyl propionate, isopropyl formate, isopropyl acetate, n-butyl acetate and t-butyl acetate. The method of the present invention is generally practiced in connection with the formation of a continuous glass band substrate, for example, during a float glass production process. However, the method of the present invention can be applied in the coating of other flat glass substrates either online or offline. The present invention involves the preparation of a propellant gas mixture including tin or titanium tetrachloride and an organic oxygen-containing compound; A carrier gas or diluent eg nitrogen, air or helium, will also normally be included in the gas mixture. Because the thermal decomposition of the organic oxygen-containing compound can initiate the metal oxygen deposition reaction at a high rate, it is desirable that the precursor mixture be maintained at a temperature below the thermal decomposition temperature of the organic oxygen compound for prevent the previous reaction of the gas mixture with formation of the metal oxide. The gas mixture is maintained at a lower temperature at which it reacts to form the metal oxide, and is supplied at a location close to the flat glass substrate to be coated, the substrate being found at a temperature above the aforesaid reaction temperature (and higher than the decomposition temperature of the organic oxygen compound contained in the precursor gas mixture). The precursor gas mixture is then introduced into the vapor space directly on the substrate. The heat of the substrate increases the temperature of the precursor gas over the thermal decomposition temperature of the organic oxygen compound. The organic oxygen compound is then decomposed with the reaction of the metallic tetrachloride producing a coating of metallic dioxide on the substrate.

The present invention allows the production of tin oxide and titanium coatings deposited on hot glass at a high deposition rate, for example, more than 130A / second and, in preferred embodiments, more than 250A per second. The rate of deposition depends on the particular organic oxygen-containing compound used, and the concentrations of both the organic oxygen-containing compound and the metal chloride, as well as the temperature of the glass. For any particular combination of compounds, optimum concentrations (in particular the optimum ratio of organic oxygen-containing compound to metal tetrachloride) and flow rates for rapid coating deposition can be determined by a simple assay. However, it will be appreciated that the use of higher concentrations of reagents and high gas flow rates will likely result in a less efficient overall conversion of the reagents in coating, such that the optimum condition for the commercial operation may differ from the conditions that provide the highest deposition rates. Preferably, the organic oxygen-containing compound will be at a concentration by volume of about 0.5, especially 1 to 5 times the concentration by volume of the metal chloride. A quantity of at least 30% by weight of the weight of the metal chloride will commonly be used. The method of the invention allows the production, at high speeds, of coatings of titanium oxide and tin oxide on hot flat glass substrates in line during the glass production process. The titanium oxide coatings can be produced with a high refractive index (of at least 2.4) which allows the achievement of the desired optical effects, especially when used in combination with other coating layers. The tin oxide coatings can be contaminated, for example with fluoride, by incorporating a suitable precursor of the dopant into the precursor gas mixture, increasing the electrical conductivity and the infrared reflectivity of the coatings, and, therefore, their usefulness as coatings. conductors of electricity or coatings of low emission power in architectural and other applications. BRIEF DESCRIPTION OF THE DRAWINGS The foregoing, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the detailed description that follows of the preferred embodiments, when considered under the light of the drawings. Annexes where: Figure 1 is a schematic view of a vertical section of an apparatus for implementing a float glass process that includes gas distributors placed in a suitable manner to allow the implementation of the method of the present invention. Figure 2 is an exploded section view of an article coated in accordance with the present invention; and Figure 3 is an elongated schematic end view of a gas distributor beam suitable to be applied in the practice of the present invention. Figure 4 is an elongated schematic end view of an alternative gas distributor beam that can be used in the practice of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENT With reference now more particularly to the drawings, a float glass installation used as a means for practicing the method of the present invention is generally illustrated at 10 in Figure 1. The float glass apparatus more particularly comprises a channel section 12 along which the molten glass 14 is supplied from a foundry furnace (not shown), to a float bath section 16 where a glass band is formed Continue 18 in accordance with the well-known float process. The glass band 18 advances from the section of the bath 16 through an adjacent annealing tunnel 20 and a cooling section 22. The continuous glass band 18 serves as the substrate on which the metal oxide coating is deposited in accordance with the present invention. The float section 16 includes a lower section 24 within which a float is contained. molten tin bath 26, a roof 28, opposite side walls 30 and end walls 32. The roof 28, the side walls 30, and the end walls 32 together define a housing 32 wherein a non-oxidizing atmosphere is maintained to prevent oxidation of melted tin. Additionally, there are gas distributing beams 64, 66 and 68 located in the section of the bath 16. The bundles of the gas distributor 64 and 66 that are in the section of the bath can be used to apply additional coatings on the substrate before applying the tin oxide or titanium coating by the method of the present invention. Additional coatings may include silicone and silica. In operation, the molten glass 14 flows along the channel 36 below a regulating gate 38 and downwards in the direction of the surface of the tin bath 26 in controlled quantities. In the tin bath the molten glass is spread laterally under the influence of gravity and surface tension, as well as certain mechanical influences, and is advanced through the bath to form the strip 18. The strip is removed on rollers 40 and thereafter it is transported through the recharge tunnel 20 and the cooling section 22 on aligned rollers 42. The coating application of the present invention can occur in the float bath section 16, or later as along the production line, for example in the space between the float bath and the recosido tunnel, or in the recosido tunnel. A suitable non-oxidizing atmosphere, generally nitrogen or a mixture of nitrogen and hydrogen in which nitrogen predominates, is maintained in the housing of the bath 34 to prevent oxidation of the tin bath. Atmospheric gas is admitted through ducts 44 functionally coupled to a distribution system 46. The non-oxidizing gas is introduced at a sufficient rate to compensate for normal losses and maintain a slight positive pressure, in the range of about 0.001 to about 0.01 atmospheres. on the atmospheric atmospheric pressure, in such a way that the infiltration of the external atmosphere is prevented. The heat to maintain the desired temperature regime in the tin bath 26 and the housing 34 is provided by radiant heaters 48 which are within the housing. The atmosphere inside the recosido tunnel 20 is typically atmospheric air, while the cooling section 22 is not closed and the glass band is open to the ambient atmosphere. The ambient air can be directed against the glass strip by fans 50 which are in the cooling section. The heaters (not shown) may also be provided within the recumbent tunnel to cause the temperature of the glass band to be gradually reduced according to a predetermined rate and transmitted therethrough. Figure 1 illustrates the use of gas distributor bundles 64, 66 and 68, placed in the float bath 16 to deposit the various coatings on the substrate of the glass strip. The gas distributor beam is a form of reactor that can be employed in practicing the process of the present invention. A suitable configuration for the distributor beams suitable for supplying the precursor materials according to the invention are shown in generally schematic form in figure 3. An inverted frame generally in the form of a channel 70 formed by internal and external walls 72 and 74, separated defines enclosed cavities 76 and 78. A suitable technical exchange medium is circulated through the closed cavities 76 and 78 to maintain the distributor beams at a desired temperature. The precursor gas mixture is supplied through a liquid-cooled supply conduit 80. The supply conduit 80 extends along the bundle of the distributor and admits the gas through descending pipes 82 spaced along the conduit. supply. The supply conduit 80 leads to a supply chamber 84 within the head 86 carried by the frame. The precursor gases admitted through the descending pipes 82 are discharged from the supply chamber 84 through a passage 88 in the direction of the coating chamber defining a vapor space opening on the glass where they flow along the surface of the glass 18 in the direction of the arrows shown in Figure 3. Baffle plates 90 can be provided within the supply chamber 84 to equalize the flow of the precursor materials through the distributor beam to ensure that they are discharged against the glass 18 in a smooth, laminar flow and completely uniform through the distributor beam. The spent precursor materials are collected and removed through the exhaust chambers 92 along the sides of the distributor bundle.

Various forms of distributor beams used for chemical vapor deposition are suitable for the present method and are known in the prior art. An alternative distributor beam configuration is illustrated schematically in Figure 4 of the drawings. Using this dispenser, which is generally designated 100 (and more fully described in European patent EP 0 305 102B), the precursor gas mixture is introduced through a gas supply pipe 101 where it is cooled by a cooling liquid. circulated through the ducts 102 and 103. The gas supply duct 101 is opened through an elongated opening 104 within a gas flow restrictor 105. The gas flow restrictor 105 is of the type most fully described in FIG. UK Patent Specification GB1 507 996, and comprises a variety of metal strips longitudinally crimped in the form of a sine wave and mounted vertically in a contact relationship with one another extending along the distributor. The adjacent crimped metal strips are disposed "out of phase" to define a variety of vertical channels therebetween. These vertical channels have a small cross-sectional area relative to the cross-sectional area of the gas supply pipe 101, such that the gas is released from the gas flow restrictor 105 at a substantially constant pressure throughout. of the distributor. The coating gas is released from the gas flow restrictor to the intake side 107 of a substantially U-shaped guide channel generally designated 106 comprising the intake leg 107, the coating chamber 108 that opens towards the hot glass substrate 110 to be coated, and the exhaust leg 109, whereby the coating gas used is removed from the glass. The rounded corners of the blocks defining the coating channel promote a uniform laminar flow of the coating parallel to the glass surface through the glass surface to be coated. The following examples (in which gas volumes are expressed under normal conditions, i.e., an atmosphere pressure and an ambient temperature, unless otherwise indicated) and are presented for the purpose of illustrating and further presenting this invention , and should not be construed as a limitation thereof: Examples 1 to 5 In this series of examples, a bidirectional coating reactor of the type shown in Figure 3 was employed in the laboratory to deposit a coating of titanium oxide. In Examples 1, 2 and 3, the glass was heated in a conveyor belt oven to simulate the coating reaction conditions of a float glass process to test the method of the present invention. The furnace used in-line rollers to transport a glass substrate through a heating zone prior to practicing the method of the present invention. In Example 1, the glass substrate was float glass that had been initially provided with a silica coating. The silica coating was deposited on the float glass through a known chemical vapor deposition process using a monokoline precursor in an oxygen enriched atmosphere. The silica deposition does not form part of the present invention. In accordance with the present invention, a coating of titanium oxide was deposited on the substrate coated with silica. The substrate was at a temperature of 1170 ° F / 630 ° C and the line speed of the substrate was 300 inches / 8 meters per minute. To deposit the titanium oxide, a precursor gas mixture was created comprising titanium tetrachloride, ethyl acetate, oxygen and helium. The helium was included in the precursor mixture as a carrier for the reagents. The precursor mixture was made by the simultaneous introduction of the four gas streams through a collector system. A static in-line mixer was used to ensure a homogenous precursor mixture. The composition in percentage by volume of the precursor mixture was 0.7% titanium tetrachloride, 17.2% ethyl acetate, 7.2% oxygen and 74.9% helium, showing the flow rates of the collector components as shown in table 1 annex. The temperature of the precursor mixture was maintained above 300 ° F / 150 ° C to prevent the addition reaction of titanium tetrachloride and ethyl acetate. The precursor temperature was also kept below the thermal decomposition temperature range 950 ° F-1130 ° F (510 ° F-610 ° C) of the ethyl acetate to prevent the mixture from undergoing a previous reaction. The precursor mixture was introduced into the reactor just above the moving substrate. The temperature in the precursor tower was 250 ° F / 120 ° C. The temperature at the front of the reactor was 350 ° F / 175 ° C. The higher temperature of the substrate initiated the thermal decomposition of the ethyl acetate which then caused the deposition of the titanium oxide. The resulting coated glass was allowed to stand in air and the coating was analyzed. It was found to be of titanium oxide with a carbon content of 2.5-3.5 atomic percent. The coating thickness of titanium oxide was measured at 490Á and the thickness and rate of growth (150A per second) are shown in Table 1. The optical properties of the resulting product included an observed illuminating C factor of 35.6%. The extinction coefficient was 0.008 to 550 nm, and the refractive index of the titanium oxide coating was 2.44. In examples 2 and 3 the coating procedure specified in example 1 was repeated, except that in example 2 ethyl formate was used as the organic oxygen source, and in example 3 isopropanol was used as the organic oxygen source and uncoated glass was used as the substrate (instead of the glass coated with silicone oxide of examples 1 and 2). The gas flow rates used and, in the case of Example 2, the thickness and growth rate of the titanium oxide coating produced are shown in Table 1. In Example 3, the isopropanol was burned in the reactor leaving only particulate titanium oxide in the glass, the corresponding deposition rate, is thus indicated as 0Á / sec. The procedure for examples 4 and 5 was used in the previous examples (the temperature of the rector and the substrate being identical to those of example 1), except that the substrate was static and not dynamic. The static sample was placed under the reactor for 10 seconds. Under static conditions, the residence time of the substrate under the reactor is increased with respect to the dynamic conditions by a factor of 5. In example 4, methyl acetate was used as the organic source of oxygen, and in Example 5 it was used t-butyl acetate; in all cases a coating of titanium oxide was produced. The gas flow rates, titanium oxide coating thickness and resultant coating growth rates are shown in Table 1. The relatively slow growth rate achieved using methyl acetate is discussed below. Example 6 A float glass process was applied in the production of a continuous glass strip with a thickness of 0.125 inches / 3 mm at a line speed of 434 inches / 11 meters per minute. The temperature of the glass was 1140 ° F / 615 ° C at the desired point of application in the flotation bath section of a titanium oxide coating using a coating reactor similar to that shown in Figure 3. The temperature in the precursor tower was 400 ° F / 205 ° C and the temperature at the front of the reactor was 500 ° F / 260 ° C. Prior to practicing the method of the present invention, a silica coating was deposited on the glass substrate in the flotation bath section to a thickness of approximately 339A. The chemical vapor deposition process as described in example 1 was used to deposit the silica coating. The silica deposition does not form part of the present invention. The precursor gas mixture was made comprising titanium tetrachloride and ethyl acetate in a helium carrier gas. Oxygen was not used in the precursor as a result of the above examples indicating that the coating reaction was not sensitive to oxygen concentration. The precursor mixture was made by simultaneously introducing the three components through a collector system. The composition by volume percentage of the percussion mixture was 0.6% titanium tetrachloride, 1.8% ethyl acetate and 97.5% helium. The flow rates of the components were 480.0 l / m helium, 3.0 l / m titanium tetrachloride, 9.2 l / m ethyl acetate. The total flow rate of the precursor mixture was 492.2 l / m. The resulting titanium oxide coating was 684A thick. The carbon content of the coating was less than 2 atomic percent. The growth rate of the coating was 309A per second. Example 7 In this example, the same procedure was carried out as in the example 6. The substrate comprised silicone coatings and then silica on the glass substrate. The coatings were deposited by a known chemical vapor replenishment process in the flotation bath section. The silicone coating was deposited by CVD from monosilane with a non-oxidizing carrier gas, the silica coating was then deposited on the silicone coating through the use of the same procedure described in Example 1. The coating precursor Titanium oxide included titanium tetrachloride and ethyl acetate in a helium carrier gas. The percentage composition by volume of the precursor was 0.5% titanium tetrachloride, 1.9% ethyl acetate and 97.6% helium. The corresponding flow rates of the components were 480.0 l / m helium, 2.4 l / m titanium tetrachloride, 9.2 l / m ethyl acetate. The total flow rate of the precursor mixture was 491.6 l / m. The resulting coated article 52 is illustrated in Fig. 2. The glass substrate 54 is depicted with a stack of multiple coatings 56. The coatings comprise a layer of silicone at 58, a layer of silica 60, then a coating of titanium oxide 62 at the top of the article. The titanium oxide coating of the resulting article had a thickness of 836 A. The optical properties of the resulting coating stack included an illuminant transmission factor C of 13.1% and an illuminant reflectance C of 82.5%. The growth rate of the titanium oxide coating was 378A per second. TABLE 1 Example Flow rates (liters / minutes) Tetrachloride Oxygen Compound Oxygen Elido Thickness Speed of organic titanium increased A / sec. 1 0.2 4.8 ethyl acetate 2.0 20. .9 490 150 2 0.5 1.6 ethyl formats 6.0 17. .4 800 250 3 0.45 1.5 isopropanol 4.0 15. .45 0 0 4 0.5 1.2 methyl format 6.0 17. .4 <; 100 < 10 5 0.5 0.5 t-butyl acetate 6.0 16. .5 1300 130 Examples 8-13 In this series of examples, a static coating in the laboratory was used to apply a tin oxide coating on a float glass substrate carrying a color suppressor silicone oxide layer produced as described in the patent European EP 0 275 662B. The float glass to be coated was supported on a nickel block in a reactor vessel and the block was heated from below by electrical heating elements to provide a glass temperature of 1085 ° F / 585 ° C. A flat graphite plate at approximately 0.4 inches / 10 mm was mounted on the glass and parallel thereto to provide a 0.4 inch / 10 mm depth gas flow path between the glass surface carrying the silicone oxide layer and the plate. A precursor gas mixture containing tin tetrachloride and an organic oxygen source, in air and a small proportion of additional nitrogen as a carrier gas, was supplied through a gas pipeline maintained at a temperature of 435 ° F + 25 ° F / 225 ° C + 15 ° C provided with a fishtail nozzle opening in the gas flow path on the hot glass in a general direction parallel to the surface of the glass. The total transport gas flow velocity was 13m3 / hour. The flow rates of tin tetrachloride and the nature of the flow rates of the organic compound used are shown in Table 2 annexed. In Examples 9 and 11, small amounts of 40% hydrogen fluoride were incorporated into the precursor gas mixture to impurify the resulting tin oxide coating with fluoride, as shown in the table. The gas flow containing the reactive gases was applied for approximately 8 seconds, and the coating apparatus and the coated glass were allowed to cool under an air flow at 345 ° F / 225 ° C. When dismantling the coating apparatus, the supply gas pipe, the nozzle and the plate defining the gas flow path on the glass, were in each case free of deposits, indicating an absence of undesirable prior reaction. In all cases, the glass had a coating of tin oxide applied on the silicone oxide, varying the thickness of the coating with the distance from the fishtail nozzle. The maximum thickness and the corresponding growth rate for each mixture of precursor gas used is shown in Table 2. The emission power, resistivity and dry haze of the samples produced using hydrogen fluoride to incorporate a fluoride dopant (examples 9 and 11) were measured and the results are given in Table 2. This series of examples shows that an organic oxygen source can be used as part of a pre-mixed precursor gas mixture comprising tin tetrachloride to deposit an oxide coating. of tin without undesirable and considerable prior reaction affecting the coating process, for example, by the deposition of tin oxide in the gas supply ducts. In addition, if desired, a source of dopant, for example hydrogen fluoride, can be incorporated into the gaseous premix to reduce the emitting power and the resistivity of the coating while still avoiding the considerable damaging pre-reaction.

TABLE 2 E j us Precursor gas mixture Sn Cl, source of organic oxygen HF at 40% Thickness Maximum Speed d Speed of Speed of Growth Oxide in flow ral / rain) Compound flow (ml / min) Flow Maximum Tin A seconds 12 ethyl acetate 10 2750 344 12 ethyl acetate 2680 butyl acetate 13.4 3460 butyl acetate 13.4 isopropyl alcohol 262 13 17 trifluoroacetic acid 2840 335 Example 14 In this example, a coating distributor as illustrated schematically in Figure 4 it was used in a float bath to apply a tin oxide coating through a method according to the invention. The band speed was approximately 233 inches per minute / 350 minutes per hour and the thickness of the glass was 0.05 inches / 1.2 mm. The glass temperature was approximately 1170 ° F / 630 ° C. The temperature of the gas supply duct 101 that served as the main gas mixing chamber was maintained at 300 ° F / 150 ° C and the "static" coffered gas distributor 105 was approximately 645 ° F / 340 ° C. The vapors of tin tetrachloride and butyl acetate were supplied through nitrogen boron through liquids maintained at 175 ° F / 80 ° C in bubblers and, therefore, through separate heated conduits to the gas supply pipe 101. The vapors mixed in the main chamber, were passed through the gas distributor of coffer gaskets, and then under conditions of laminar flow through the gas. a U-shaped guide channel 106 comprising the coating chamber 108 that opens toward the hot glass strip.

The flow rates used were sufficient to obtain molar proportions of tin tetrachloride with respect to butyl acetate between 1: 1 and 1: 5. The test was carried out for 5 hours. By dismantling the coater it was found that the cooled surfaces and related conduits were free of deposits by more than 90%, thus showing that tin tetrachloride and butyl acetate used to produce a coating of tin dioxide on glass can be preblended each other without considerable prior reaction. A thin tin oxide coating was obtained in the glass strip. It will be appreciated that various changes and modifications can be made to the specific details of the invention as incorporated in the previous examples without departing from the spirit and scope thereof as defined in the appended claims. In its essential details, the invention is a vapor deposition chemical deposition process for placing tin oxide and titanium oxide coatings on a glass substrate at high deposition rates through the use of corresponding metallic tetrachloride and organic compound used as a source of oxygen in a previously formed precursor gas mixture.

Metal tetrachlorides are preferred sources of the respective metals given the availability and cost of the raw material. It has been discovered, especially when depositing titanium oxide coatings from titanium tetrachloride, that, in order to form the metal oxide at the optimum deposition rates, it is desirable to use a compound containing organic oxygen which is an ester, particularly an ester in that the group derived from the alcohol is an alkyl group with a β-hydrogen. In addition, the decomposition temperature of the ester should not be higher than the reaction temperature of the precursor gas mixture of the coating and the desired application point. The esters used in the precursor gas mixture have a ß hydrogen and suitable decomposition temperatures will deposit the coatings at high replacement rates. The group of preferred esters used in the practice of the present invention includes the group consisting of ethyl formate, ethyl acetate, ethyl propionate, isopropyl formate, isopropyl acetate, n-butyl acetate and d-acetate. butyl. In general, an ester decomposes continuously over a given temperature range. In the present invention, the thermal decomposition temperature of the ester is defined as the temperature at which the constant of the unimolecular decomposition rate of the ester is 0.01 / sec. The constants of the unimolecular decomposition rate of the common esters, for example, ethyl acetate and t-butyl acetate are known and can be found in the chemistry writings. For ethyl acetate and t-butyl acetate, the thermal decomposition temperatures using the above definition are 935 and 650 ° Fahrenheit (500 ° C and 344 ° C), respectively. One skilled in the art will recognize that the choice of the ester and the specific deposition temperature employed will determine the optimum coating growth rate. Reaction temperatures below the defined thermal decomposition temperature, but within the decomposition range of the selected ester, will cause lower coating growth rates. According to the present invention, the alkyl group of an ester used in the coating precursor gas mixture can be a carbon compound with a range of 2-10 carbon atoms. The lower limit of the range is determined by the hydrogen requirement of the alkyl group. The upper limit is to avoid the flammability and volatility that arise when the alkyl group contains more than 10 carbon atoms.

By practicing the method of the present invention, a manifold can be used to connect and regulate the individual gas flows to formulate the coating precursor gas mixture. A common supply tube can be used to supply the precursor gas mixture from the manifold to the gas bundle distributor. And a static in-line mixer can be used in the in-line supply to ensure a homogenous gas mixture. In addition, the baffles that are in the gas distributor beam, illustrated in Figure 3, or a gas flow restrictor as described with reference to Figure 4, can provide an additional mixture of the precursor gas in the gas phase. reactor. In many of the examples, oxygen was included in the coating precursor gas mixture. However, the deposition rate of the metal oxide coating was not sensitive to oxygen concentrations, and oxygen gas was not used in Examples 6 or 7 showing that the inclusion of oxygen was unnecessary. The concentration of the reactive components of the coating percolation gas mixture can be selected to obtain the optimum coating growth rate. The concentration of metallic tetrachloride is generally 0.1 to 5.0 percent by volume in the preculsor gas mixture. The concentration of metallic tetrachloride is based on the amount of metal required to provide the desired coating thickness at the available residence time. Thus, the concentration of metal tetrachloride is adjusted according to the process variables, for example the line speed of the strip in a float glass process. The concentration of the organic oxygen compound in the precursor coating gas mixture if it is generally from one to five times the concentration of metallic tetrachloride, being selected within this range based on the deposition temperature. When an ester is used, low deposition temperatures will demonstrate lower ester decomposition rates and, therefore, will require higher ester concentrations to react with the metal tetrachloride. In Examples 6 and 7, the optimum concentration of the ethyl acetate in the precursor gas mixture is 1 to 3 times the concentration of titanium tetrachloride. Concentrations above or below the optimum range will produce metal oxide coatings at lower coating growth rates. The temperature of the precursor gas mixture is fundamental to control the reaction, in particular, to avoid an undesirable pre-reaction or the formation of addition resulting in the formation of a non-volatile product in the precursor tubes. In a preferred embodiment, especially applicable when using an ester, the temperature is maintained above 300 ° F / 150 ° C in the precursor gas tubes. The precursor gas mixture is also preferably maintained below the thermal decomposition temperature of the organic oxygen compound to prevent pre-reaction of the mixture. The present inventive process uses the heat of the substrate to initiate the coating reaction. In on-line situations, for example, the float glass process, the substrate is formed at extremely high temperatures. Therefore, the method of the present invention can be applied to a point in the float glass process where the temperature of the substrate decreases but is still above the temperature at which the coating is formed, and preferably after that temperature. the glass band has substantially finished stretching, for example, less than 1380 ° F / 750 ° C). Off-line applications of the present invention will require heating the substrate at a temperature above the decomposition temperature of the ester. When practicing the method of the present invention in the float glass process, the preferred point of application is in the section of the float bath. The temperature range at the application point for the coating is usually approximately 1100o-1320oF / 590 ° -715 ° C. The temperature is an important operating parameter since it influences the concentration of the organic compound used in the precursor gas mixture. The temperatures of the substrate in the section of the float bath are relatively stable and show, therefore, little variation in the point of application. In Examples 6 and 7 using ethyl acetate, the preferred substrate temperature range is 1100 ° -1250 ° F / 590 ° C-680 ° C. The heat of the substrate increases the temperature of the precursor gas mixture above the temperature required for the formation of the coating (and when an ester is used as the organic compound over the thermal decomposition temperature of the ester). The metal deposition reaction can be initiated by the decomposition of the organic oxygen compound. When titanium tetrachloride is used in combination with an ester having an alkyl group with a β-hydrogen, the titanium oxide coating is then formed on the substrate at decomposition rates that are 10 times higher than the known coating methods. The application in line with a float glass band process, the band passes under the gas distributor beam at a relatively high speed. The metallic oxide coating is deposited on the float glass strip as the band passes under the riser. The inventors propose the following theory with respect to the chemical reaction that can occur when using an ester having an alkyl group with a β-hydrogen. However, the inventors do not wish to limit the invention to only this possible explanation, and therefore offer it only as an aid in understanding the results of the current inventive process. The inventors propose that as the ester decomposes, the carbon-hydrogen bond of 1 of the β-hydrogens breaks down and the hydrogen is transferred to the carbonyl group by removing an alkene and forming a carboxylic acid. The hydrolysis reaction occurs simultaneously between the carboxylic acid and the metal tetrachloride leading to the formation of the metal oxide coating on the substrate. In general, the resulting article produced in accordance with the present invention comprises a substrate coated with titanium oxide or tin oxide. The coating can be applied directly to the substrate or as a layer in a variety of coating on a substrate. The deposition rate of the metal oxide coating is effected by the decomposition rate of the organic oxygen compound. At constant reaction temperatures different organic oxygen compounds will provide different rates of coating growth given the difference in decomposition temperatures. Therefore, the growth rate of the desired metal oxide coating for a given system is selected by comparing a specific organic oxygen compound with the temperature of the precursor gas mixture and the temperature of the substrate at the point of application. The rate of replacement of the titanium oxide coating of the present invention can be 10 times greater than the speeds of the known deposition methods. The current inventive process allows deposition rates of more than 13OÁ per second by measuring some deposition rates much more than 300Á per second. The higher deposition rates of titanium oxide produce a coating with a refractive index greater than 2.4. A further advantage of the invention, in addition to the high coating rates that can be achieved, is that it employs low-cost metal precursors and, especially, when the precursor gas mixture is directed onto the substrate under laminar flow conditions preferred, allows the achievement of a high conversion efficiency (of metallic tetrachloride).

In the present invention, the resulting oxide coating contains little residual carbon from the decomposition of the organic oxygen compound, especially when an ester is used. Carbon is an undesirable by-product of the coating reaction because high levels of carbon in the deposition coatings create problems of absorption in the coating. The interest of using an organic oxygen compound in the precursor coating gas mixture is that the decomposition will cause carbon levels which will adversely affect the absorption properties of the finished glass. The carbon content of the coatings produced with the method of the present invention showed less than 4 atomic% carbon, in the cases in which it was measured. This low carbon level does not significantly affect the absorption properties of the coating. It should be understood that the forms of the invention shown and described herein should be taken as illustrative embodiments thereof only, and that various changes in the shape, size and arrangement of the parts may be made, as well as several procedural changes without get away from the spirit of investment.

Claims (25)

1. CLAIMS 1. A process for depositing a tin oxide or titanium oxide coating on hot flat glass comprises the steps of: (a) preparing a precursor gas mixture containing the corresponding metallic tetrachloride and an organic oxygen containing compound as the source of oxygen for the formation of metal oxide, (b) maintaining the precursor gas mixture at a temperature lower than the temperature at which the metal chloride reacts to form the metal oxide while supplying the mixture to a coating chamber opening over the hot glass, (c) introducing the precursor gas mixture into the coating chamber whereby the mixture is heated to cause the deposition of the corresponding metal oxide incorporating the oxygen coming from the organic compound on the surface of the hot glass.
2. 2. A process for depositing a tin oxide or titanium oxide coating on a hot flat glass as claimed in claim 1, wherein the organic oxygen-containing compound is an ester containing from 2 to 10 carbon atoms, and where the ester is in a concentration by volume of 0.5 to 5 times the concentration by volume of the metallic tetrachloride.
3. 3. A process for depositing a tin oxide or titanium oxide coating on hot flat glass as claimed in claim 2, wherein the ester is an ester having an alkyl group with a β-hydrogen.
4. 4. A process for depositing a tin oxide or titanium coating on hot flat glass as claimed in any of the preceding claims, wherein the ester is selected from a group consisting of ethyl, ethyl acetate, propionate format of ethyl, isopropyl formate, isopropyl acetate, n-butyl acetate, and t-butyl acetate.
5. 5. A process for depositing a tin oxide or titanium coating on hot flat glass as claimed in any of the preceding claims, wherein the substrate is a float glass band having a temperature in the range of about 1100o- 1320oF / 590 ° C-715 ° C.
6. 6. A process for depositing a tin or titanium coating as claimed in any of the preceding claims, wherein the metal tetrachloride found in the precursor gas mixture is at a concentration of about 0.1-5.0% by volume .
7. 7. A process for depositing a tin oxide or titanium coating on hot flat glass as claimed in any of the preceding claims, wherein the organic oxygen-containing compound in the precursor gas mixture is at a concentration of about 1 to 5 times the concentration of the metal tetrafloride.
8. 8. A process for depositing a tin oxide or titanium coating on a hot flat glass as claimed in any of claims 2 to 7, wherein the ester is ethyl acetate and the hot flat glass is a glass strip floated 9.
9. A process for depositing a tin oxide or titanium coating on hot flat glass as claimed in any of the preceding claims wherein the hot flat glass substrate has on it a silica coating, and the oxide coating of Tin or titanium is deposited on the silica coating.
10. A process for depositing a tin oxide or titanium coating on hot flat glass as claimed in any of the preceding claims, wherein the hot flat glass substrate has a silica coating on a silicone coating, and the Tin oxide or titanium coating is deposited on the silica coating.
11. 11. A process for depositing a titanium oxide coating on a substrate on hot flat glass as claimed in any of the preceding claims, wherein the titanium oxide coating has a refractive index greater than 2.4.
12. 12. A process for depositing a tin oxide or titanium coating on hot flat glass as claimed in any of the preceding claims, wherein the tin oxide coating of titanium has a residual carbon content of less than 4 atomic% .
13. 13. A process for depositing a tin oxide or titanium coating on hot flat glass as claimed in any of the preceding claims, wherein the precursor gas mixture includes helium as a carrier gas.
14. 14. A process for depositing a tin oxide or titanium coating on hot flat glass as claimed in any of claims 2 to 13, wherein the ester has an alkyl group having 2-10 carbon atoms.
15. 15. A process for depositing a titanium tin oxide coating on hot flat glass as claimed in any of the preceding claims, wherein the tin oxide titanium film is deposited at a rate of at least 130A per second. .
16. 16. A process for depositing a coating of tin oxide or titanium on a substrate at high deposition rates, being a process as claimed in any of the preceding claims, comprising the steps of: (a) preparing a mixture of precursor gas containing tin or titanium tetrachloride and an ester, the ester having an alkyl group with a β-hydrogen; (b) supplying the precursor gas mixture at a temperature lower than the thermal decomposition temperature of the ester to a location near a substrate to be coated, the substrate being found at a temperature above the thermal decomposition temperature of the ester; and (c) introducing the precursor gas mixture into a vapor space on the substrate where the ester is thermally decomposed and therefore initiating a reaction with the metal tetrachloride to produce a metal oxide coating on the substrate.
17. 17. A process as claimed in claim 17 wherein the substrate is a float glass band.
18. 18. A process as claimed in claim 15 or claim 17 wherein the precursor gas mixture is supplied to the substrate at a location where the temperature of the substrate is in the range of 1100 ° -1320 ° F.
19. 19. A process for depositing a titanium oxide coating on a substrate at high deposition rates, comprising the steps of: (a) preparing a precursor gas mixture containing titanium tetrachloride and an ester, containing the ester of titanium oxide; to 10 carbon atoms and having an alkyl group with a β hydrogen; (b) supplying the precursor gas mixture at a temperature lower than the thermal decomposition temperature of the ester to a location near a substrate to be coated, the substrate being found at a temperature above the thermal decomposition temperature of the ester; and (c) introducing the precursor gas mixture into a vapor space on the substrate where the ester is thermally decomposed and thereby initiating a reaction with the titanium tetrachloride to produce a coating of titanium oxide on the substrate.
20. 20. A process as claimed in claim 19 wherein the substrate is a float glass band.
21. 21. A process as claimed in claim 19 or claim 20 wherein the precursor gas mixture is supplied to the substrate at a location where the substrate temperature is in the range of 1100 ° -1320 ° F .
22. 22. A process for depositing a tin oxide or titanium coating on hot flat glass as claimed in any of the preceding claims wherein the precursor gas mixture is flowed onto the glass surface to be coated under flowing conditions laminar
23. 23. A glass substrate having a coating of tin oxide or titanium on it prepared by the process of any of the preceding claims.
24. 24. A glass substrate with a coating of silicone and silica on it having a coating of tin oxide or titanium on the silica coating, prepared the oxide coating by the process of any of claims 1 to 23.
25. 25 The use of an ester as an oxygen source for the formation of a metal oxide in a process for the deposition of a tin oxide or titanium oxide coating in hot flat glass comprising the steps of: (a) preparing a mixture of precursor gas containing the corresponding metal tetrachloride and an oxygen source, (b) maintaining the precursor gas mixture at a temperature lower than the temperature at which the metal chloride reacts to form the metal oxide while supplying the mixture to the a coating chamber opening on the hot glass, (c) introducing the precursor gas mixture into the coating chamber by which the mixture it is heated to cause the deposition of the corresponding metal oxide on the hot glass surface.