Method of depositing tin oxide coating on flat glass and coated glass obtained by the method

The present invention relates to a method of depositing a tin oxide coating on a flat glass substrate and to the coated glass obtained by this method. In particular, the present invention relates to a chemical vapor deposition method for obtaining a tin oxide coating on flat glass using a coating precursor gas mixture containing the corresponding metal tetrachloride and organic oxide.

Titanium oxide coatings and tin oxide coatings have been proposed for use in glass containers, such as bottles, to improve the mechanical strength of this container. It has also been proposed to use both titanium oxide and tin oxide coatings on flat glass to modify the properties of the glass for use in architectural applications; provided under vacuum (by reactive sputtering). The titanium oxide coating is used as a component of the sputtered multi-layered infrared reflective coating, while the tin oxide coating is used not only as a layer of the multi-layer sputtered coating, but also as an infrared reflective coating and / or conductive coating with the dopant. Accumulated by decomposition.

British Patent No. 1 115 342 states that glass containers with good intrinsic strength and good wear resistance are organic liquids, preferably isopropyl, with respect to containers that are still hot from the manufacturing process. The process of making by spraying a solution or dispersion of stannic chloride (ie, tin tetrachloride) in alcohol is disclosed. A small amount of titanium chloride can be introduced as a denaturant. A type of jet injection, which can be a sprayer located on any side of the tunnel above the conveyor for hot glass bottles, is fed with a liquid solution to obtain a "liquid reagent mist", thereby obtaining a "liquid reagent mist". A layer of liquid is formed over the entire outer surface of the bottle, where the layer of liquid reacts to form a layer of tin oxide.

UK Pat. No. 1 187 784, UK Pat. No. 1 115 An improvement to the process described in 342, which is apparent to be introduced during the automated manufacturing process of glassware, which does not affect the normal practice of such a process and does not require additional monitoring. A method that is more suitable for is described. The patent specification proposes to treat a glass container at a high temperature with a liquid solution of an organic compound of tin, "this compound decomposes into two substances by applying heat. However, one of them is an organic compound of tin having a high decomposition temperature, and this organic compound reacts with the glass surface to form a diffusion layer of tin oxide in the glass surface, and the other substance is , A volatile compound of tin that yields a significant proportion of the vapors of the above compounds, with the property that the container is heat-treated to cause a reaction between the glass and the tin compound at least on the surface of the container. Have. " The substances used to treat glass containers are tin tetrachloride, organic substances with moderately active carbonyl groups, such as ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol and isobutyl alcohol and acetic acid. , Propyl acid and butyric acid can be provided by reacting with an organic ester. The resulting solution is applied to a hot container in the presence of an ambient atmosphere, for example in the form of fine mist, after the high temperature container has advanced from the molding machine and before entering the annealing slow cooling machine. Can be sprayed on. UK Pat. No. 1,187,783 describes a method similar to that described in UK Pat. No. 1,187,784, wherein the organic compound of titanium is used instead of the organic compound of tin. , Spray on a hot glass container. The organic titanium compound can be obtained by reacting titanium tetrachloride with an organic ester such as n-butyl acetate in a manner similar to that of tin organic compounds. Again, the resulting solution is sprayed onto the glass in a container production line in an ambient atmosphere.

It is also conductive and reflects infrared light by providing a tin oxide coating on hot flat glass, using tin tetrachloride, which is also applied as a liquid spray or, more recently, in gaseous form. It was proposed to form a coating on the surface of hot glass; water was used as an oxygen source to hydrolyze tin tetrachloride to form tin oxide.

For processes involving the use of reactants in gaseous form (also referred to as CVD or chemical vapor deposition methods), flat glass, especially if the reactants can be premixed prior to application to glass. There are some advantages over the spraying method for coating. Unfortunately, tin tetrachloride reacts easily with water, so the previous proposal to use tin tetrachloride and water vapor in gaseous form usually supplies the gas separately to the glass surface, these. Was accompanied by mixing the gas while in contact with the glass.

UK Pat. No. 2,044, 137A creates a separate laminar flow for each reactant and releases these flows together onto a hot glass substrate by tangentially contacting each other on the glass. Regarding the process. Titanium tetrachloride can be used instead of tin tetrachloride as one of the gaseous reactants to form a titanium oxide coating. The patent specification also suggests that hydrogen is supplied to one of the gas streams to weaken the violent reaction between tin tetrachloride and water vapor. This can be done by adding gaseous hydrogen directly or by adding methanol, which is said to react in-situ to produce the desired gaseous hydrogen.

UK Pat. No. 2,026, 454B states that the cladding is placed on a hot float glass ribbon as it advances from the float bath, (1) preheated nitrogen carrier gas, (2). A continuous gaseous stream of tin tetrachloride entrained in preheated nitrogen and (3) air, water vapor and hydrofluoric acid was introduced into the cladding and these flowed along the surface of the glass substrate. , A method of coating as an almost undisturbed layer is described. In this patent specification, the concentrations of water vapor and tin tetrachloride in the gaseous medium on glass are specified.

European Patent Nos. 0 365 239B1 and 0 376 240B1 describe methods and equipment for depositing tin oxide coatings on hot glass ribbons. A first gas stream of tin tetrachloride in preheated dry air flows along the surface of a hot glass ribbon traveling under the cladding to create a second turbulent stream of hydrofluoric acid and water vapor. Introduced into the cladding chamber at right angles to the plane of the glass and the direction of the flow of the first gas stream, the combined first and second gas streams are passed through the cladding chamber above the glass. , Pull out under turbulent conditions. This method and device can also be used to provide a titanium oxide coating with titanium tetrachloride instead of tin tetrachloride.

U.S. Pat. No. 4,590 096 contains a coating solution containing an almost solvent-free mixture of organotin chloride and reactive organofluorines, which is soluble in or miscible with organotin chloride, 18 A method of introduction into a preheated carrier gas stream containing sufficient water vapor for the relative humidity of the gas stream to be about 6% to about 100% at ° C is described. The resulting gas stream is passed over the surface of the hot glass to deposit a fluorine-doped tin oxide coating on the hot glass. It is stated that a wide range of organotin compounds can be used and tin tetrachloride can be used. Similarly, a wide range of organofluorine compounds, including oxygen-containing compounds, such as trifluoroacetic acid and ethyl trifluoroacetate can be used. Some fluorine-containing dopants have low solubility in the organotin compounds used, and optional solubilizers can be used to increase the solubility of the fluorine dopant in the organotin compounds; ethyl anhydride, ethyl acetate, Hexane, methyl isobutyl ketone and butyraldehyde are listed as non-limiting examples of solubilizers that can be used. However, in this US patent specification, steam is used as the oxygen source, as in other patent specifications where metal oxides are deposited from gaseous metal tetrachloride using a chemical deposition method.

US Pat. No. 4,751 149 by Vijaykumar et al. Chemically applied zinc oxide coatings on heat-sensitive photoconductor substrates at low temperatures (60 ° C to 350 ° C, preferably 100 ° C to 200 ° C). It relates to depositing by vapor deposition, and it has been proposed to deposit zinc oxide coatings from organozinc compounds and oxygen-containing organic compounds, such as oxides and inert carrier gases that can be esters. .. Although this patent specification is not completely clear, it is clearly proposed in this patent specification to introduce separate streams of organozinc compounds and oxidants into the deposition chamber, a mixture of these. It is a fact that it has not been proposed to premix these components before sending them to the cladding.

US Pat. No. 4,731,256 and European Patent Application No. 0,186,481 relate to an improved liquid coating composition for producing high quality fluorine-doped tin oxide coatings; No. 5 401 305 relates to a composition for coating glass by chemical vapor deposition, wherein the composition is a reaction accelerator such as a metal oxide precursor, a carbon dioxide precursor tetraethyl orthosilicate, and triethylphosphite. Organic tin chloride (defined as containing tin tetrachloride) as a tin source, along with atmospheric or added oxygen, which consists of a mixture of and reacts to form metal oxides deposited on glass substrates. Organic fluorine compounds, which may be esters, are used as a source of fluorine, and esters are present to stabilize the liquid as needed. In each case, the liquid composition vaporizes in a stream of oxygen containing carrier gas for delivery to hot glass, which probably acts as an oxygen source for forming the tin oxide coating.

US Pat. No. 5,124,180 describes a CVD method for producing a metal oxide coating containing fluorine on a substrate, and the equipment used in that method, with respect to the metal oxide precursor and oxygen. Water or alcohol as a source is separately delivered to the cladding in the form of a gas and mixed just before depositing on the substrate.

<p> The tin oxide coating is applied to the hot, flat glass by the CVD method, using a premixture of the corresponding metal tetrachloride and oxygen source as a low cost reactant, metal tetrachloride and oxygen source ( It is advantageous to provide a method of depositing without causing problems and inefficiencies as a result of the premature reaction with water) resulting in the formation of metal oxides in the coating equipment. The method allows for high-speed deposition of the coating, which is especially advantageous when it is possible to deposit the required coating thickness on the moving glass ribbon during the glass manufacturing process.</p>

<p> In the present invention, in providing the tin oxide coating on a high temperature glass substrate, a precursor gas mixture containing the corresponding metal tetrachloride and organic oxygen source is used, without the need to introduce water vapor, resulting in a premature reaction. Provide a non-hazardous, chemical vapor deposition method.</p><p> The present invention provides a method of depositing a tin oxide coating on a hot, flat glass, which method (a) produces the corresponding metal tetrachloride and organic as an oxygen source for the formation of metal oxides. A precursor gas mixture containing an oxygen-containing compound is produced, and (b) the precursor gas mixture described above is maintained at a temperature lower than the temperature at which the metal tetrachloride reacts to form a metal oxide, and at the same time, the mixture is maintained. , Delivery to a cladding open on hot glass, (c) introducing this precursor gas mixture into the cladding, thereby heating the mixture to contain oxygen from organic compounds. Including the step of causing the metal oxide to be deposited on the surface of the high temperature glass.</p><p> Surprisingly, a wide range of oxygen-containing organic compounds can be used as an oxygen source without the need for the presence of water vapor or gaseous oxygen, which is usually considered a reducing agent rather than an oxidizing agent. Contains compounds such as alcohol. However, preferred organic compounds are carbonyl compounds, especially esters; particularly good results have been obtained with esters having alkyl groups with β-hydrogen. Alkyl groups with β-hydrogen usually contain 2 to 10 carbon atoms.</p><p> It is preferable to use an organic compound having 2 to 10 carbon atoms, particularly an ester. The reason is that larger molecules tend to be less volatile and are therefore more inconvenient to use in the CVD method of the present invention.</p><p> Particularly preferred esters to be used 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.</p><p> The methods of the invention are generally practiced in connection with forming a continuous glass ribbon substrate, for example during a float glass manufacturing process. However, the methods of the invention can be used to coat other flat glass substrates, either online or offline. The present invention involves producing a precursor gas mixture containing tin tetrachloride and an organic oxygen-containing compound; a carrier gas or diluent such as nitrogen, air or helium is usually included in the gas mixture. Since the pyrolysis of the organic oxygen-containing compound can initiate the metal oxide deposition reaction at a high speed, the precursor mixture is kept at a temperature lower than the pyrolysis temperature of the organic oxygen compound, which is accompanied by the formation of the metal oxide. It is desirable to prevent the pre-reaction of the gaseous mixture.</p><p> The gaseous mixture is maintained at a temperature lower than the temperature at which it reacts to form a metal oxide and delivered to a location near the coated flat glass substrate, which is at a temperature higher than the reaction temperature described above. (And the temperature is higher than the decomposition temperature of the organic oxygen compound in the precursor gas mixture). The precursor gas mixture is then introduced into the vapor space just above the substrate. The heat from the substrate raises the temperature of the precursor gas to a temperature higher than the thermal decomposition temperature of the organic oxygen compound. The organic oxygen compound then decomposes with reaction with the metal tetrachloride to form a metal dioxide coating on the substrate.</p><p> The present invention makes it possible to deposit tin oxide coatings on hot glass at high deposition rates, such as greater than 130 Å / sec, and, in preferred embodiments, greater than 250 Å / sec.</p><p> The deposition rate depends on the particular organic oxygen-containing compound used, as well as the concentrations of both the organic oxygen-containing compound and the metal chloride, and the temperature of the glass. For any particular combination of compounds, the optimum concentration (and especially the optimum ratio of organic oxygen-containing compound to metal tetrachloride) and the flow rate for rapid coating deposition can be determined by simple testing. .. However, as a result of using higher concentrations of reactants and higher gas flow rates, the overall efficiency of conversion of the reactants to the coating tends to be relatively low, so the optimum conditions for industrial operation are It should be understood that the conditions that provide the highest deposition rate may differ.</p><p> Preferably, the volumetric concentration of the organic oxygen-containing compound is about 0.5 times, particularly 1 to 5 times, the volume concentration of the metal chloride. Generally, the organic oxygen-containing compound can be used in an amount of at least 30% by weight based on the weight of the metal chloride.</p><p> According to the method of the present invention, the titanium oxide coating and the tin oxide coating can be produced online at high speed during the glass production process on a high temperature flat glass substrate. Titanium oxide coatings can be produced with a high index of refraction (at least 2.4), which allows the desired optical effect to be achieved, especially when used in combination with other coating layers. The tin oxide coating can be doped, for example, with fluorine by introducing a suitable precursor for the dopant into the precursor gas mixture, thereby increasing the conductivity and infrared reflectance of the coating. The usefulness of the coating as a conductive coating and / or low emissivity coating in building polish and other applications can be enhanced.</p>

Here, with reference to the drawings more specifically, the float glass equipment used as a means for carrying out the method of the present invention is generally shown in FIG. This float glass device, more specifically, comprises a canal portion 12, along which the molten glass 14 is fed from a melting furnace (not shown) to a float bath portion 16, where a continuous glass ribbon 18 is provided. Is formed by a well-known float process. The glass ribbon 18 travels from the bath portion 16 through the adjacent annealing slow cooling chamber 20 and the cooling portion 22. The continuous glass ribbon 18 acts as a substrate on which a metal oxide coating is deposited according to the method of the invention.

The float portion 16 has a bottom 24, within which a bath of molten tin 26, a top 28, opposing side walls 30 and end walls 32 are included. The top 28, side wall 30 and end wall 32 together form a siege 34, in which a non-oxidizing atmosphere is maintained to prevent oxidation of molten tin.

In addition, gas distributor beams 64, 66 and 68 are placed in the bus section 16. Using the gas distributor beams 64 and 66 in the bus portion, an additional coating is applied on the substrate before the tin oxide coating is applied by the method of the invention. Additional coatings can include silicon and silica.

In operation, the molten glass 14 flows downward along the canal 36 under the regulating tweel 38 and on the surface of the tin bath 26 in a controlled amount. On the tin bath, the molten glass diffuses laterally under gravity and surface tension, as well as some mechanical influence, which travels across the bath to form the ribbon 18. The ribbon is removed onto a lift out roll 40 and then transported over an aligned roll 42 through the annealing slow-cooling gear 20 and the cooling section 22. The coating of the present invention can be applied in the float bath portion 16 or in another production line, for example, in the gap between the float bath and the annealing slow cooling, or in the annealing slow cooling.

A suitable non-oxidizing atmosphere, generally a nitrogen atmosphere or an atmosphere of a nitrogen-hydrogen mixture with high nitrogen content, is maintained in the bath enclosure 34 to prevent oxidation of the tin bath. Ambient gas is introduced through a conduit 44 operatively combined with the distribution manifold 46. The outside atmosphere is introduced with a non-oxidizing gas at a rate sufficient to compensate for normal losses and maintained at a slightly positive pressure, about 0.001 to about 0.01 atm above the surrounding atmospheric pressure. Prevents penetration of gas. Heat is provided by the radiant heater 48 in the siege to maintain the desired temperature conditions in the tin bath 26 and the siege 34. The atmosphere inside the slow-cooling sill 20 is typically ambient air, while the cooling portion 22 is not surrounded and the glass ribbon is exposed to the ambient atmosphere. Ambient air is directed at the glass ribbon, for example, by a fan 50 in the cooling section. Also, a heater (not shown) is provided in the annealing slow-cooling cage to gradually reduce the temperature of the glass ribbon according to the surrounding conditions as the ribbon is transported through the slow-cooling cage. be able to.

FIG. 1 illustrates the deposition of various coatings on a glass ribbon substrate using gas distributor beams 64, 66 and 68 placed in a float bath 16. The gas distributor beam is one form of reactor that can be used in the practice of the methods of the invention.

In the present invention, an advantageous form for a distributor beam suitable for supplying precursors is generally graphically shown in FIG. An inverted, generally grooved skeleton 70 formed by separated inner and outer walls 74 defines closed cavities 76 and 78. A suitable heat exchange medium is circulated through the closed spaces 76, 78 to maintain the distributor beam at the desired temperature.

The precursor gas mixture is fed through a fluid-cooled supply conduit 80. The supply conduit 80 extends along the distributor beam and allows the gas to travel through the descent line 82, which is spaced along the supply conduit. The supply conduit 80 leads to a delivery chamber 84 in the header 86 supported by the skeleton. The precursor gas transported by the descent line 82 is discharged from the delivery chamber 84 through the passage 88 toward the covering chamber defining the steam space open on the glass, where these precursor gases are glass. It flows along the surface of 18 in the direction of the arrow shown in FIG.

A deflector 90 is provided in the delivery chamber 84 to equalize the flow of precursor material across the distributor beam so that the material is smooth, layered and, relative to the glass 18, completely traverses the distributor beam. Ensure that the discharge is uniform. Consumed precursors are collected and removed along the sides of the distributor beam through the discharge chamber 92.

Various forms of distributor beams used for chemical vapor deposition are suitable for the methods of the invention and are known in the art.

One such alternative form of distributor beam is shown graphically in FIG. The precursor gas mixture is introduced through the gas supply duct 101 using this distributor, commonly indicated by reference numeral 100 (also more fully described in European Patent EP 0 305 102B). Here, the mixture is cooled by a cooling fluid circulating through ducts 102 and 103. The gas supply duct 101 is opened in the gas flow throttle 105 by the elongated opening 104.

The gas flow throttle 105 is of the type more fully described in UK Pat. No. GB 1 507 996, which has a longitudinal waveform in the form of a sinusoid and is of the distributor. It has a plurality of metal strips placed vertically in contact with each other so as to extend along the length direction. Metal strips with adjacent corrugations are placed "out of phase" to define multiple vertical grooves between them. These vertical grooves have a cross-sectional area smaller than the cross-sectional area of the gas supply duct 101, whereby the gas is discharged from the gas flow throttle 105 at a substantially constant pressure along the length direction of the distributor. Will be done.

The coating gas is drawn from the gas flow throttle, generally in 106, approximately U-shaped, with inlet legs 107, a coating chamber 108 open on the hot glass substrate 110 to be coated, and discharge legs 109. It is discharged into the inlet side 107 of the guide groove of the guide groove, thereby drawing the used coating gas out of the glass. The rounded corners of the block defining the coating groove facilitate a uniform layered flow of coating parallel to the glass surface across the glass substrate to be coated.

The following examples (where, unless otherwise stated, the gas volume is expressed under standard conditions, i.e., pressure at 1 atm and ambient temperature) are presented for the purposes of further exemplifying and disclosing the present invention. These examples should not be construed as limiting the invention.

<u style="single">Reference example 1 ~ 5</u> In this series of reference examples, a two-way coating reactor of the type shown in FIG. 3 was used in the laboratory to deposit a titanium oxide coating.

In Reference Examples 1, 2 and 3, the glass was heated on a conveyor furnace to simulate the coating reaction conditions of the float glass process and tested the method of the invention. The furnace used an in-line roller to transport the glass substrate through the heating zone prior to implementing the method of the invention. In Reference Example 1, the glass substrate was a float glass first provided with a silica coating. This silica coating was deposited on float glass by a known chemical vapor deposition process using a monosilane precursor in an oxygen-rich atmosphere. Silica deposits do not constitute any part of the invention.

According to the present invention, a titanium oxide coating was deposited on a silica-coated substrate. The temperature of this substrate was 1170 ° F (630 ° C) and the linear velocity of the substrate was 300 inches / minute (8 m / min).

A precursor gas mixture containing titanium tetrachloride, ethyl acetate, oxygen and helium was generated to deposit titanium oxide. Helium was included in the precursor mixture as a carrier for the reactants. This precursor mixture was prepared by simultaneously introducing all four gas streams with a manifold system. An in-line static mixer was used to ensure homogenization of the precursor mixture. The volume percentage composition of the precursor mixture was 0.7% titanium tetrachloride, 17.2% ethyl acetate, 7.2% oxygen and 74.9% helium, and the flow rates of the components in the manifold were as shown in Attached Table 1.

The temperature of the precursor mixture was kept above 300 ° F (150 ° C) to prevent the adduct reaction between titanium tetrachloride and ethyl acetate. In addition, the temperature of the precursor was maintained below the thermal decomposition temperature range of ethyl acetate, 950 ° F to 1130 ° F (510 ° C to 610 ° C), to prevent the mixture from pre-reacting.

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 on the surface of the reactor was 350 ° F (175 ° C). At relatively high substrate temperatures, the thermal decomposition of ethyl acetate began, which in turn resulted in the decomposition of titanium oxide.

The resulting coated glass was allowed to cool in air and the coating was analyzed. This coating was found to be titanium oxide with a carbon content of 2.5-3.5 atomic%. The thickness of the titanium oxide coating was measured to be 490 Å, and this thickness and growth rate (150 Å / sec) are shown in Table 1. The optical properties of the resulting product had an observed illuminant C transmittance of 62.3% (10 ° observer) and an observed illuminant C reflectance of 35.6%. The extinction coefficient was 0.008 at 550 nm and the refractive index of the titanium oxide coating was 2.44.

In Reference Examples 2 and 3, in Reference Example 2, ethyl formate is used as an organic oxygen source, and in Reference Example 3, isopropanol is used as an organic oxygen source, and uncoated glass (silicon oxide in Reference Examples 1 and 2) is used. The coating procedure described in Reference Example 1 was repeated, except that (instead of the glass coated with) was used as the substrate. Table 1 shows the gas flow rate used and, in the case of Reference Example 2, the thickness and growth rate of the obtained titanium oxide coating. In Reference Example 3, isopropanol was burned in the reactor and only fine-grained titanium oxide remained on the glass, so the corresponding deposition rate was estimated to be 0 Å / sec.

The procedures of Reference Examples 4 and 5 were the same as those used in Reference Examples 1 to 3 except that the substrate was made static and not dynamic (the reactor temperature and the substrate were the same as those of Reference Example 1). ). The static sample was placed under the reactor for 10 seconds. Under static conditions, the residence time of the substrate under the reactor was extended by a factor of 5 compared to dynamic conditions.

In Reference Example 4, methyl acetate was used as the organic oxygen source, and in Reference Example 5, t-butyl acetate was used as the organic oxygen source; in each case, a titanium oxide coating was obtained. The gas flow rate and the resulting titanium oxide coating thickness and coating growth rate are shown in Table 1. The relatively slow growth rates obtained with methyl acetate are discussed below.

<u style="single">Reference example 6</u> A float glass process was used to produce a continuous glass ribbon with a linear velocity of 434 inches / minute (11 m / min) and a thickness of 0.125 inches (3 mm). The glass temperature was set to 1140 ° F (615 ° C) at the desired location for use in the float bath portion of the titanium oxide coating, using a coating reactor similar to the coating reactor shown in FIG. The temperature at the precursor column was 400 ° F (205 ° C) and the temperature at the reactor surface was 500 ° F (260 ° C). Prior to carrying out the method of the invention, a silica coating was deposited on a glass substrate in a float bath portion to a thickness of about 339 Å. The silica coating was deposited using the same chemical vapor deposition process as described in Reference Example 1. Silica deposits do not constitute any part of the invention.

A precursor gas mixture containing titanium tetrachloride and ethyl acetate in the helium carrier gas was generated. Oxygen was not used in the precursor as the results of the previous comparative example showed that the coating reaction was not affected by the oxygen concentration. To produce the precursor mixture, three components were simultaneously introduced through the manifold system. The volume percentage composition of the precursor mixture was 0.6% titanium tetrachloride, 1.8% ethyl acetate and 97.5% helium. The flow rates for these components were helium 480.0 l / m, titanium tetrachloride 3.0 l / m, and ethyl acetate 9.2 l / m. The total flow rate for the precursor mixture was 492.2 l / m.

The thickness of the titanium oxide coating obtained was 684 Å. The carbon content of this coating was less than 2 atomic%. The growth rate of the coating was 309 Å / sec.

<u style="single">Reference example 7</u> The same procedure as that used in Reference Example 6 was used in this Reference Example. The substrate had a silicon coating and then silica on top of the glass substrate. This coating was deposited in the float bath portion by a known chemical vapor deposition process. A silicon coating was deposited by CVD from monosilane containing a non-oxidizing carrier gas. The silica coating was then deposited on the silicon coating by using the same procedure as described in Reference Example 1.

The precursor for titanium oxide coating contained titanium tetrachloride and ethyl acetate in the helium carrier gas. The volume percentage composition of this precursor was 0.5% titanium tetrachloride, 1.9% ethyl acetate and 97.6% helium. The flow rates corresponding to these components were helium 480.0 l / m, titanium tetrachloride 2.4 l / m, and ethyl acetate 9.2 l / m. The total flow rate for the precursor mixture was 491.6 l / m.

The obtained coated article 52 is illustrated in FIG. The glass substrate 54 is illustrated as having a stack of a plurality of coatings 56. This coating has a silicon layer 58, a silica layer 60, and then a titanium oxide coating 62 on top of the article. The titanium oxide coating on the resulting article had a thickness of 836 Å. The optical properties of the stack of coatings obtained included 13.1% observed illuminant C transmittance and 82.5% observed illuminant C reflectance. The growth rate of the titanium oxide coating was 378 Å / sec.

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<u style="single">Examples 1 to 6</u> In this series of examples, a static coating machine was used in the laboratory to obtain tin oxide coating as described in European Patent EP 0 275 662B. It was provided on a float glass substrate having a silicon layer.

Float glass to be coated was supported on a nickel block in a reaction vessel and the block was heated from below by an electroheating element to obtain a glass temperature of 1085 ° F (585 ° C). A flat graphite plate is mounted parallel to the glass approximately 0.4 inches (10 mm) above the glass and a 0.4 inch (10 mm) deep gas flow path between the glass surface with the silicon oxide layer and the plate. Was provided.

A precursor gas mixture containing tin tetrachloride and an organic oxygen source in air as a carrier gas and a small amount of additional nitrogen was maintained at a temperature of 435 ° F ± 25 ° F (225 ° C ± 15 ° C). It was delivered through a gas line provided with a fishtail nozzle opening on the gas flow path above the hot glass in a direction generally parallel to the glass surface. Total carrier gas flow rate is 13m³ / It was time. The flow rate of tin tetrachloride and the properties and flow rates of the organic compounds used are shown in the attached Table 2. In Examples 2 and 4, as shown in the table, a small amount of 40% hydrogen fluoride was introduced into the precursor gas mixture to dope the resulting tin oxide coating with fluorine.

A stream of gas containing the reactant gas was applied for approximately 8 seconds, then the coating and coated glass were allowed to cool under an air stream of 345 ° F (225 ° C). Upon removal of the covering device, the delivery gas lines, nozzles and plates defining the gas flow path above the glass were found to be free of deposits in each case, which means that there was no undesired pre-reaction. Show that. In each case, the glass has a tin oxide coating provided on silicon oxide, the thickness of which coating varies with distance from the fishtail nozzle. The maximum thickness and corresponding growth rate for each precursor gas mixture used are shown in Table 2. The emissivity, resistivity and fogging of the samples (Examples 2 and 4) obtained by introducing a fluorine dopant using hydrogen fluoride were measured, and the results are recorded in Table 2.

This series of examples uses an organic oxygen source as part of a premixed precursor gas mixture containing tin tetrachloride, which adversely affects the coating process, for example by depositing tin oxide in the gas supply duct. It is shown that the tin oxide coating can be deposited without any significant undesired pre-reaction to give. In addition, if desired, a source of dopant, such as hydrogen fluoride, is introduced into the gaseous premix to reduce the emissivity and resistivity of the coating while at the same time continuing to avoid significant undesired prereactions. be able to.

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<u style="single">Example 7</u> In this embodiment, the coating distributor graphically illustrated in FIG. 4 was used in the float bath to provide tin oxide coating by the method of the present invention. The ribbon speed was about 233 inches per minute / 350 minutes per hour and the glass thickness was 0.05 inches (1.2 mm). The glass temperature was about 1170 ° F (630 ° C). The temperature of the gas supply duct 101, which acts as the primary gas mixing chamber, is maintained at 300 ° F (150 ° C), and the "static" waffle gas distributor 105 is approximately 645 ° F (340 ° C). )Met. To deliver the vapor of tin tetrachloride and butyl acetate, nitrogen is passed through a liquid maintained at 175 ° F (80 ° C) in a bubbler, which is passed through a separate heated conduit as bubbles through the gas supply duct 101. .. The steam mixed in the primary chamber is passed through a waffle pack gas distributor and then under layered flow conditions, a U-shaped guide groove 106 with a cladding 108 open on a hot glass ribbon. ..

The flow rate used was sufficient to make the molar ratio of tin tetrachloride to butyl acetate between 1: 1 and 1: 5. This test was performed for 5 hours. Upon removal of the coating machine, it was found that the cooled surface and associated conduits were free of deposits in more than 90% of the area, which was used to obtain the tin dioxide coating on the glass. It is shown that tin chloride and butyl acetate can be premixed with each other with little pre-reaction. A thin tin oxide coating was obtained on the glass ribbon.

It should be understood that various modifications and modifications may be made from the specific details of the invention, including the embodiments described above, without departing from the ideas and scope of the invention as set forth in the appended claims. is there. In an essential detail of the invention, the invention uses a tin oxide coating and a titanium oxide coating on a glass substrate and an organic compound as the oxygen source in the corresponding metal tetrachloride and precursor gas mixture. This is a continuous chemical vapor deposition process that is provided on the glass substrate at a high deposition rate.

Metal tetrachloride is the preferred source of each metal due to the availability and cost of the raw material.

Especially when the titanium oxide coating is deposited from titanium tetrachloride, the ester, especially the alcohol-derived atomic group, is an alkyl group having β-hydrogen in order to form a metal oxide at an optimum deposition rate. It has been found that it is desirable to use organic oxygen-containing compounds. Furthermore, the decomposition temperature of the ester must not be higher than the reaction temperature of the coating precursor gas mixture at the desired application. Esters used in precursor gas mixtures with β-hydrogen and a suitable decomposition temperature deposit the coating at a high deposition rate. Preferred groups of esters used to carry out the present invention include the group consisting of ethyl formate, ethyl acetate, ethyl propionate, isopropyl formate, isopropyl acetate, n-butyl acetate and t-butyl acetate.

Generally, the ester decomposes in a continuous manner over a predetermined temperature range. In the present invention, the thermal decomposition temperature of the ester is defined as the temperature at which the single molecule decomposition rate constant of the ester is 0.01 / sec. Single molecule decomposition rate constants for common esters such as ethyl acetate and t-butyl acetate are well known and can be found in the chemical literature. For ethyl acetate and t-butyl acetate, the pyrolysis temperatures using the above definitions are 935 ° F (500 ° C) and 650 ° F (344 ° C), respectively. Those skilled in the art are aware that the choice of ester to be used and the particular deposition temperature will determine the optimal coating growth rate. Although below the specified thermal decomposition temperature, the reaction temperature within the decomposition range of the selected ester results in a slower coating growth rate.

In the present invention, the alkyl group of the ester used in the coating precursor gas mixture can be a carbon compound having carbon atoms in the range of 2 to 10. The lower limit of this range depends on the need for β-hydrogen on the alkyl group. The upper limit is to avoid the flammability and volatility problems that arise when the alkyl group has more than 10 carbon atoms.

In carrying out the methods of the invention, a manifold can be used to connect and regulate individual gas streams to formulate a coating precursor gas mixture. A common delivery line can be used to deliver the precursor gas mixture from the manifold to the gas beam distributor. An in-line static mixer can be used in the delivery line to ensure a uniform gas mixture. In addition, the precursor gas can be further mixed at the reactor stage by means of a deflector in the gas distributor beam illustrated in FIG. 3 or the gas flow throttle described with reference to FIG.

In many of the examples, oxygen was introduced into the coating precursor gas mixture. However, the deposition rate of the metal oxide coating is not affected by the oxygen concentration, and Reference Example 6 or 7 shows that oxygen gas is not used, which makes it unnecessary to introduce oxygen. Was done.

The concentration of the reactive component of the coating precursor gas mixture can be selected to obtain the optimum coating growth rate. The concentration of metal tetrachloride is generally 0.1-5.0% by volume in the precursor gas mixture. The concentration of metal tetrachloride is based on the amount of metal required to obtain the desired coating thickness at the available residence time. Therefore, the metal tetrachloride concentration is adjusted according to the variable of the process, for example the linear velocity of the ribbon in the float glass process.

The concentration of the organic oxygen compound in the coating precursor gas mixture is generally 1 to 5 times the concentration of the metal tetrachloride, and is selected within this range based on the decomposition temperature. When using an ester, the relatively low deposition temperature results in a relatively low rate of ester decomposition, thus requiring a higher ester concentration to react with the metal tetrachloride. In Reference Examples 6 and 7, the optimum concentration of ethyl acetate in the precursor gas mixture is 1 to 3 times the concentration of titanium tetrachloride. At concentrations higher or lower than the optimum range, metal oxide coatings form at relatively low coating growth rates.

The temperature of the precursor gas mixture is critically important to control the reaction, especially to avoid unwanted pre-reactions or adduct formation that result in the formation of non-volatile products in the precursor line. In one preferred embodiment, which is particularly applicable when using esters, the temperature in the precursor gas line is maintained above 300 ° F (150 ° C). Further, it is preferable to keep the precursor gas mixture at a temperature lower than the thermal decomposition temperature of the organic oxygen compound to prevent the pre-reaction of the mixture.

The method of the present invention uses heat from a substrate to initiate a coating reaction. In the online state, for example in the float glass process, the substrate is formed at extremely high temperatures. Therefore, the method of the present invention reduced the temperature of the substrate, but still the temperature at which the coating was formed (and preferably the temperature after the elongation of the glass ribbon was almost complete, ie 1380 ° F (750 ° C)). Can be used at locations in the float glass process when the temperature is higher than (less than). For offline application of the present invention, it is necessary to heat the substrate to a temperature higher than the decomposition temperature of the ester.

In carrying out the method of the present invention in the float glass process, the preferred application point is in the float bath portion. The temperature range where the coating is applied is usually about 1100 ° F to 1320 ° F (590 ° C to 715 ° C). This temperature is an important operating parameter. The reason is that this temperature affects the concentration of organic compounds used in the precursor gas mixture. The temperature of the substrate in the float bath portion is relatively stable and therefore shows little change at the point of application. In Reference Examples 6 and 7 using ethyl acetate, the preferred substrate temperature range is 1100 ° F to 1250 ° F (590 ° C to 680 ° C).

The heat from the substrate causes the temperature of the precursor gas mixture to be higher than the temperature required to form the coating (and, when the ester is used as an organic compound, higher than the thermal decomposition temperature of the ester). Rise. 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 having β-hydrogen, a titanium oxide coating is formed on the substrate at a decomposition rate 10 times higher than that of known coating methods. In the online application of the float glass ribbon process, the ribbon passes under the gas distributor beam at a relatively high rate. The metal oxide coating is deposited on the float glass ribbon as the ribbon passes under the coating machine.

The present inventors propose the following theories related to chemical reactions that can occur when an ester having an alkyl group having β hydrogen is used. However, the inventors do not want the invention to be limited to this possible description, and thus provide it merely as an aid in understanding the results of the methods of the invention.

The present inventors propose that when the ester is decomposed, the carbon-hydrogen bond in one of the β-hydrogens is cleaved, the hydrogen moves to the carbonyl group, the alkene is eliminated, and a carboxylic acid is produced. Is. A hydrolysis reaction occurs simultaneously between the carboxylic acid and the metal tetrachloride, which produces a metal oxide coating on the substrate.

Generally, the finished article produced according to the present invention comprises a substrate having a tin oxide coating. The coating can be provided directly on the substrate or as multiple layers of coating on the substrate. The rate of deposition of the metal oxide coating is affected by the rate of decomposition of the organic oxygen compounds. At steady reaction temperatures, different organic oxygen compounds provide different coating growth rates due to differences in decomposition temperatures. Therefore, in order to select the desired metal oxide coating growth rate for a given system, the particular organic oxygen compound is matched to the precursor gas mixture temperature and substrate temperature at the point of application.

The deposition rate of the titanium oxide coating in the present invention can be 10 times higher than the deposition rate of known deposition methods. The methods of the present invention allow deposition rates in excess of 130 Å / sec, with some deposition rates measured to be well in excess of 300 Å / sec. Higher rates of titanium oxide deposition give the coating a refractive index greater than 2.4.

In addition to being able to achieve high coating rates, another advantage of the present invention is that in the present invention low cost metal precursor compounds are used, in particular a precursor gas mixture is preferably layered above the substrate. When guided under flow conditions, the present invention is capable of achieving high conversion efficiencies (of metal tetrachloride).

In the present invention, the obtained oxide coating contains almost no residual carbon from the decomposition of the organic oxygen compound, especially when an ester is used. Carbon is an undesired by-product of the coating reaction, as high levels of carbon present in the deposited coating cause absorption problems in the coating. A concern in using organic oxygen compounds in coating precursor gas mixtures is that the decomposition results in levels of carbon that adversely affect the absorption properties of the finished glass. The carbon content in the coatings obtained from the methods of the invention was shown to be less than 4 atomic% when measured. This low level of carbon does not significantly affect the absorption properties of the coating.

The embodiments shown and described herein should be construed as merely exemplary embodiments of the invention, with various changes in shape, dimensions and arrangement of components, as well as changes in various procedures. It should be understood that it can be adopted without departing from the idea of the present invention.

<figref num="1">FIG. 1 is a schematic cross-sectional view of a device for carrying out the float gas process of the present invention, comprising a gas distributor suitablely arranged to enable the practice of the method of the present invention.</figref><figref num="2">FIG. 2 is a partial cross-sectional view of the article covered by the present invention.</figref><figref num="3">FIG. 3 is an enlarged schematic end view of a gas distributor beam suitable for use in the practice of the present invention.</figref><figref num="4">FIG. 4 is a magnified end view of another gas distributor beam that can be used to carry out the present invention.</figref>