Process of applying coatings based on tin oxide and titanium oxide to substrate and glass substrate with such coating

Method of applying coatings based on tin oxide and titanium oxide on a substrate and a glass substrate with such a coating (57)

The deposition of the tin or titanium oxide coating by chemical vapor deposition on a substrate, in particular a hot flat glass, is carried out with an oxygen-containing organic compound and the corresponding metal tetrachloride. The organic compound is preferably an ester having an alkyl group with b-hydrogen to achieve a high deposition rate. Due to the high attainable speeds, typically at least 13 nm / s, the method suitable for depositing greater thickness coatings on a moving glass ribbon is in the glass manufacturing process.

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-1 Method of depositing coatings based on tin oxide and titanium oxide on a substrate and a glass substrate coated with such a coating

Technical field

The invention relates to a process for the deposition of titanium oxide and tin oxide coatings and glass coated with such a coating. More particularly, the invention relates to a chemical vapor deposition (CVD) process for forming titanium oxide and tin oxide coatings on a flat glass using a gaseous coating precursor composition comprising a metal tetrachloride and an organic oxidizing agent.

BACKGROUND OF THE INVENTION

Titanium oxide and tin oxide coatings have been proposed for use on glass containers, such as bottles, to improve the mechanical strength of the containers. It has also been proposed to use both titanium and tin oxide coatings on flat glass to vary the properties of glass for use in architecture. Titanium oxide coatings applied under vacuum (reactive sputtering) are used as components of a sprayed multilayer coating reflecting infrared radiation, but are also applied pyrolytically with a dopant as infrared reflecting coatings and / or electroconductive coatings.

GB 1 115 342 discloses a process for producing glass containers with good intrinsic strength by spraying containers that are still hot from the manufacturing process with a solution or dispersion of tin tetrachloride in an organic liquid, with isopropyl alcohol being preferred. A small amount of titanium tetrachloride may be added as a modifier.

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ru. The liquid solution is fed to nebulizers which can be placed on the sides of the tunnel above the hot glass bottle conveyor and which form a liquid reagent mist so that a liquid layer is formed on all outer surfaces of the bottles where it reacts to form a tin oxide layer.

GB 1 187 784 discloses an improvement to the method described in GB 1 115 342 and is apparently more suitable for incorporation into the process of automatically manufacturing glass products without collisions with the normal operation of such a process and without requiring further supervision. The disclosure proposes to treat glass containers at high temperature with a liquid solution of an organic tin compound having the properties of decomposing into two substances upon application of heat, one of which is an organic tin compound having a high decomposition temperature which reacts with the glass surface to form a diffuse layer. the second surface being a volatile tin compound, so that a substantial proportion of the vapor of the tin compound is developed, and the containers are subjected to a heat treatment such as by causing a reaction between the glass and at least one of the surfaces of the containers and tin compounds.

The material used for processing glass containers can be obtained by reacting tin tetrachloride with organic substances containing low activity carbonyl groups, for example, organic esters of ethyl, η-propyl, isopropyl, n-butyl and isobutyl alcohols with acetic, propionic and butyric acids. The resulting solution may be sprayed in the presence of ambient atmosphere onto hot containers, for example in the form of a fine mist after leaving the molding machine and before entering the cooling furnace.

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GB 1 187 783 describes an analogous process to that described in GB 1 187 784, in which an organic titanium compound is sprayed on hot glass containers instead of an organic tin compound. An organic tin compound can be produced, analogously to an organic tin compound, by reacting titanium tetrachloride with an organic ester, e.g., n-butyl acetate. Again, the resulting solution is sprayed with glass in the ambient air on a container production line.

It has also been proposed to use tin tetrachloride, applied as a liquid spray, or more recently in gaseous form, to deposit a tin oxide coating on a hot flat glass to form an infrared reflective electroconductive coating on a hot glass surface using water to hydrolyze chloride and as a source of oxygen for the formation of tin oxide.

Processes involving the use of reactants in gaseous form (also called CVD or chemical vapor deposition processes) have some disadvantages over spraying processes for forming flat glass, especially when the reactants may be premixed before being applied to the glass. However, tin tetrachloride reacts readily with water, so previous suggestions to use tin tetrachloride and water vapor in gaseous form have generally been to supply the gases separately from the glass surface and mix them when in contact with the glass.

GB 2 044 137A relates to such a process in which individual laminar streams of each reactant are generated and are thrown on a hot glass sub.

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The individual streams are brought together in tangential contact with each other over 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 proposes to supply hydrogen to one of the gas streams to damp the violent reaction between titanium tetrachloride and water vapor. This may be accomplished by direct addition of hydrogen gas or by adding methanol, which is said to be allowed to react in place to produce the desired hydrogen gas.

GB 2 026 454 B discloses a method in which the coating chamber is placed over a hot strip of glass which is moved away from the float bath and the preheated nitrogen carrier stream, tin tetrachloride entrained in preheated nitrogen and air, water are introduced into the coating chamber. vapor and hydrofluoric acid by flowing along the surface of the coated substrate as a layer substantially free of turbulence.

EP 0 365 239 B1 and 0 376 240

B1 discloses a method and apparatus for depositing a tin oxide coating on a hot glass ribbon. A first gaseous tin tetrachloride stream in preheated dry air is allowed to flow along the surface of the hot glass ribbon sliding under the coating chamber, a second turbulent stream of hydrofluoric acid and steam is introduced into the coating chamber perpendicular to the plane of the glass with the flow direction of the first gaseous stream; the combined first and second gaseous streams are drawn through the coating chamber through the glass under turbulent flow conditions. The method and apparatus can also be used to deposit a titanium oxide coating using titanium tetrachloride instead of chlorine.

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·· ·· du tin.

U.S. Pat. No. 4,590,096 discloses a process in which the coating solution comprises a mixture, substantially free of solvent, tin organochloride and a reactive organic fluorine compound, soluble or miscible in tin organochloride, which is introduced into a preheated stream of gaseous carrier containing sufficient water. so that the relative humidity of the gas stream at 18 ° C is from about 6% to about 100%. The resulting gaseous stream is passed through a hot glass surface to deposit a fluoride doped tin oxide coating on the hot glass surface. A wide variety of organotin compounds can be used and the possibility of using tin tetrachloride has been reported. Similarly, a wide variety of organic fluorine compounds can be used, including oxygen-containing compounds such as trifluoroacetic acid and ethyltrifluoroacetate. Some of the fluorine-containing dopants have limited solubilities in the organotin compounds used, and an optional solubilizer may be used to increase the solubility of the dopant fluorine additive, including, but not limited to, acetic anhydride, ethyl acetate, hexane, methylisobutylketone and butyraldehyde. However, the US patent uses water vapor as a source of oxygen for the deposition of metal oxide from gaseous metal chloride, similar to other patents using gas phase chemical deposition processes.

U.S. Pat. No. 4,751,149 relates to the deposition of zinc oxide coatings by chemical vapor deposition at a low temperature (60 ° to 350 ° C, preferably 100 ° to 200 ° C) on thermally sensitive substrates in the form of a photoconductor, and proposes to «· ···· • ·

-Coat zinc oxide coatings of the organozinc compound and the oxidant, which may be an oxygen-containing organic compound such as an ester and an inert carrier gas. Although the patent is not entirely clear, it clearly suggests introducing separate streams of organozinc compound and oxidant into the deposition chamber and does not include any suggestion of premixing these components together prior to feeding them into the coating chamber.

It would be advantageous to provide a method of depositing tin or titanium oxide coatings on a hot flat glass using a preformed mixture of the corresponding metal tetrachloride as a cheap reagent, and an oxygen source without premature reaction between the metal tetrachloride and the oxygen source (still water) resulting of metal oxide in the coating apparatus with subsequent problems and lack of efficiency. It would be particularly advantageous if the method allows the coating to be applied at high speeds, which would allow the desired coating thickness to be applied to the moving glass web during glass production.

SUMMARY OF THE INVENTION

The present invention provides a method of depositing a tin oxide or titanium oxide coating on a hot glass substrate by chemical vapor deposition using a precursor gas mixture containing the corresponding metal tetrachloride and an organic oxygen source, without requiring the use of water vapor and the consequent risk of premature reaction. The present invention provides a method of depositing a tin oxide or titanium oxide coating on a hot glass substrate, wherein a precursor gas mixture is prepared comprising the corresponding metal tetrachloride and an oxygen-containing organic compound as the oxygen source to form oxi.

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The metal precursor gas mixture is maintained at a temperature below the temperature at which the metal carbon tetrachloride reacts to form the metal oxide when the mixture is fed to the coating chamber opening to the hot glass, and the precursor gas mixture is introduced into the coating chamber thereby heated to allow the corresponding oxygen-containing metal oxide from the organic compound to be deposited on the hot glass surface.

Surprisingly, a wide variety of oxygen-containing organic compounds can be used as the oxygen source without requiring the presence of water vapor or gaseous oxygen, including compounds normally considered as reducing agents rather than oxidizing agents such as alcohols. Preferred organic compounds are carbonyl compounds, especially esters. Especially good results are obtained with esters having an alkyl group with β hydrogen. The β-hydrogen alkyl group will normally contain two to ten carbon atoms.

It is preferred to use organic compounds, especially esters containing from two to ten carbon atoms, as larger molecules tend to be less volatile and thus less suitable for use in the CVD process of the invention.

Particularly preferred esters for practicing the invention include ethyl formate, ethyl acetate, ethyl propionate, isopropyl formate, isopropyl acetate, n-butyl acetate and t-butyl acetate.

The process of the invention will suitably be performed in conjunction with the formation of a continuous glass substrate.

-8 · pásu · pásu · pásu pásu pásu pásu pásu pásu pásu pásu,,,,,,,,,,,,,,,,,,,,,,,,, However, the method of the invention can be used to coat other flat substrates either on-line or off-line.

The invention encompasses the preparation of a precursor gas mixture comprising tin- or titanium tetrachloride and an organic oxygen-containing compound, wherein a gaseous carrier or diluent, such as nitrogen, air or helium, will normally also be included in the gas mixture. Since thermal decomposition of the oxygen-containing organic compound can initiate a high-speed metal oxide deposition reaction, it is desirable that the precursor mixture be maintained at a temperature below the decomposition temperature of the organic oxygen compound to prevent prior reaction of the gaseous mixture with metal oxide formation.

The gaseous mixture is maintained at a temperature below the temperature at which it reacts to form the metal oxide and is brought to a position close to the coated flat glass substrate at a temperature above said reaction temperature (and above the decomposition temperature of the oxygen-containing organic compound in the precursor). gas mixtures).

The precursor gas mixture is then introduced into the vapor space directly above the substrate. Heat from the substrate raises the temperature of the precursor gas above the thermal decomposition temperature of the organic oxygen compound. The organic oxygen compound is then decomposed by reaction with metal carbon tetrachloride to form a metal oxide coating on the substrate.

The invention enables the production of hot glass coatings of tin oxide and titanium at high speeds.

-9* · • · • · ·

· · · · · * ·, ·, ·,,,,,,,,,, eg, over 130 angstroem per second, and in preferred embodiments above 250 angstroem per second.

The deposition rate depends on the particular oxygen-containing compound used and the concentrations of the oxygen-containing organic compound and the metal chloride as well as the glass temperature. For any combination of compounds, the optimal concentrations (and in particular the optimum proportion of the oxygen-containing organic compound to the metal tetrachloride) and the rapid coating rates can be determined by mere test. It will be appreciated, however, that the use of higher reagent concentrations and higher gas flow rates is likely to result in a less efficient overall conversion of the reactants into the coating, so that optimum conditions for industrial operation may differ from those ensuring the highest deposition rates.

The organic oxygen compound will preferably have a volume concentration of about half the volume, especially one to five times the volume concentration of the metal chloride. It will generally be used in an amount of at least 30 wt% based on the weight of the metal chloride.

The process according to the invention makes it possible to produce titanium and tin oxide coatings on hot glass substrates directly on the line during the production process at high speeds. Titanium oxide coatings can be manufactured with a high refractive index (at least 2.4) to achieve the desired optical effects, especially when used in combination with other coatings. The tin oxide coatings may be doped with fluorine, for example, by incorporating them into the precursor gas

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99 The composition incorporates a suitable precursor for the dopant, thereby increasing the electrical conductivity and the ability of the coatings to reflect infrared radiation, thereby increasing their applicability as electrically conductive coatings and / or low emissivity coatings for glass used in architecture and other fields of application.

Overview of the drawings

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic vertical section through a float glass plant comprising suitably spaced gas distributors; FIG. 3 shows an enlarged schematic front view of a gas distributor in the form of a beam for use in carrying out the method according to the invention, and FIG. 4 is an enlarged schematic front view of an alternative beam-shaped gas distributor that may be used to carry out the method of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a float glass plant 10 used as a means for carrying out the process of the invention. The float glass machine comprises a channel section 12 along which molten glass 14 is discharged from a melting furnace (not shown) to a bathing bath section 16, forming a continuous glass ribbon 18 in a well known manner. The glass ribbon 18 is advanced from the bath section 16 with an adjacent cooling section 20 for tempering cooling and a cooling section 22. The continuous glass ribbon 18 serves as a substrate on which the metal oxide coating of the present invention is applied.

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The bath float section 16 houses a bath of molten tile wall 30 and end walls 32. The roof 28, side walls 30, and end walls 32 together define a chamber 34 in which a non-oxidizing atmosphere is maintained to prevent oxidation of the molten tin.

it comprises a lower part 24, a tin, and a roof 28. For additionally, beam gas distributors 64, 66 and 68 are arranged in the bath section 16. The beam gas distributors 64 and 66 in the bath section may be used to deposit additional coatings on the substrate before the tin or titanium oxide coating is applied by the method of the invention. The additional coatings may comprise silicon and silica.

In operation, the molten glass flows along the channel 36 below the regulating damper 38 and downwards to the level of the tin bath 26 in controlled amounts. On the tin bath, the molten glass spreads sideways under its own gravity and surface tension as well as certain mechanical influences, and is moved across the strip forming bath 18. The strip is removed through the lift rollers 40 and conveyed thereafter through the cooling furnace 20 and the quenching furnace. 22 after the cylinders 42 arranged in the track one after the other. The coating according to the invention can take place in the float bath section 16 or further along the production line, for example in the gap between the float bath and the cooling furnace, or in the cooling furnace.

A suitable non-oxidizing atmosphere, generally of nitrogen or a mixture of nitrogen and hydrogen in which nitrogen predominates, is maintained in the bath chamber 34 to prevent oxidation of the tin bath. Gas ♦ 9

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99 the atmosphere is fed through channels 44 operatively connected to the manifold 46. The non-oxidizing gas is fed at a rate sufficient to compensate for normal losses and maintain a slight overpressure of the order of 0.001 to 0.01 atmospheres above atmospheric pressure to prevent ambient air infiltration. Heat for maintaining the desired temperature regime in the tin bath 26 and chamber 34 is provided by radiant heaters 48 within the chamber. The atmosphere in the cooling furnace 20 is typically atmospheric air, while the quench section 22 is not spatially closed and the glass web is open to the ambient atmosphere. Ambient air may be directed against the glass web in the quench section by the fans 50. The heaters (not shown) may also be placed in a cooling furnace to cause a gradual drop in the temperature of the glass web according to a predetermined mode when conveyed through the furnace.

Fig. 1 illustrates the use of beam splitters 64, 66 and 68, located above the float bath 16, for applying various coatings to a glass ribbon substrate. Beam gas distributor is one form of reactor that can be used in the process of the invention.

Figure 3 schematically illustrates a suitable arrangement of beam distributors according to the invention. The beam distributor has a skeleton 70 in the form of a substantially inverted trough formed by inner walls 72 and outer walls 74 and defining closed cavities 76 and 78. A suitable heat exchange medium circulates through the closed cavities 76, 78 to maintain the beam dividers at the desired temperature.

The precursor gas mixture is fed through the feed screed * · «···

9* • ·

-13 * 80 *, cooled by coolant. The inlet conduit 80 extends along the manifold beam and allows gas to enter the manifold via descending pipes 80 spaced apart along the inlet conduit. The supply line 80 leads to the dispensing chamber 84 in the distributor element 86 carried by the carcass. The precursor gases supplied by the downcomers 82 are discharged from the dispensing chamber 84 through a passage 88 towards the coating chamber defining a vapor space open to the glass where it flows along the surface of the glass 18 in the direction of the arrows in FIG.

Obstacle plates 90 for aligning the stream of precursor materials through the beam divider may be positioned within the dispensing chamber 84 to ensure that the materials are discharged against the glass 18 in a smooth, laminar and uniform flow over the full width of the beam divider.

Various forms of beam splitters used for chemical vapor deposition applications known in the art are suitable for the process of the invention. One such alternative form of beam splitters is shown in Fig. 4 in the drawings. Using this manifold, referred to as manifold 100 and described in more detail in EP 0 305 102 B, the precursor gas mixture is introduced through a lance 101 where it is cooled by a cooling fluid circulating through the tubes 102. 103 ♦ The lance 101 opens through an elongated opening 104 into the gas flow restrictor 105.

The gas flow restrictor 105 is of the type described in more detail in GB 1 507 996 and comprises metal strips, longitudinally shaped in the form of a sine wave and vertically disposed

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so that they rest on each other along the length of the distributor. Adjacent shaped metal strips are arranged out of phase with each other so that they define a plurality of vertical channels therebetween. These vertical channels have a cross-sectional area that is small with respect to the cross-sectional area of ​​the lance 101 so that gas is released from the gas flow restrictor 105 at a substantially constant pressure along the length of the manifold.

The coating gas is released from the gas flow restrictor at the inlet side 107 of the substantially U-shaped guide channel including the inlet arm 107, the coating chamber 108 that opens onto the coated hot glass substrate 110, and the discharge arm 109, thereby utilizing the coating gas is withdrawn 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 across the coated glass surface.

The following examples (in which percentages by volume are expressed under standard conditions, i.e., pressure of one atmosphere at room temperature, unless otherwise stated) are for the purpose of further explanation of the invention and are not intended to be limiting thereof.

EXAMPLES 1-5

In this series of examples, a two-dimensional coating reactor of the type shown in Figure 3 was used in a titanium oxide coating laboratory. In Examples 1, 2 and 3, the glass was heated in a through furnace to simulate the coating reaction conditions of the float glass production for testing the method of the invention. In the furnace, a series of rollers arranged in succession were used in the form of · 99 · 99

A conveyor line for conveying the glass substrate through the heating zone prior to carrying out the method of the invention. In Example 1, the glass substrate was float glass which had previously been coated with silica. The silica coating was applied to the float glass by a known gas-phase deposition process using as monosilane as a precursor in an oxygen-enriched atmosphere. The deposition of silica does not form part of the invention.

According to the invention, a titanium oxide coating has been applied to the silica-coated substrate. The substrate had a temperature of 630 ° C and its conveyor line speed was 8 meters per minute.

A precursor gas mixture comprising titanium tetrachloride, ethyl acetate, oxygen and helium was formed for the deposition of titanium oxide. Helium was included in the precursor mixture as carrier for the reactants. The precursor mixture was prepared by simultaneously feeding all four gaseous streams through a manifold system. A static mixer incorporated in the flow path was used to form a homogeneous precursor mixture. The percent by volume composition of the precursor mixture was 0.7% titanium tetrachloride, 17.2% ethyl acetate, 7.2% oxygen, and 74.9% helium, the flow rates of the components in the manifold being shown in Table 1.

The temperature of the precursor mixture was maintained above 150 ° C to avoid an additional reaction of titanium tetrachloride and ethyl acetate. The temperature of the precursors was also kept below 510 ° C-610 ° C by thermal decomposition of ethyl acetate to prevent premixing of the mixture. The precursor mixture was fed into the reactor just above the moving substrate. Heat-

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9 in the precursor lead (tower) was 250 ° C. The reactor front temperature was 350 ° C. Higher substrate temperature induced thermal decomposition of ethyl acetate, which then resulted in the deposition of titanium oxide.

The resulting coating gas was allowed to cool in air and the coating was analyzed. It was found to be a titanium oxide having a carbon content of 2.5-3.5 atomic percent. The titanium oxide coating thickness of 490 angstroem was measured and the thickness and growth rates (150 angstroem per second) are shown in Table 1. The optical properties of the resulting product showed an observed light transmittance C (10 ° observer) of 62.3% and an observed light reflectance C 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 the examples 2 and 3, the coating process of example 1 was repeated except that in form 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 with the silica coating of Examples 1 and 2. The gas flow rates and, in the case of Example 2, the thickness and growth rate of the titanium oxide coating formed are shown in Table 1. In Example 3, isopropanol burned in the reactor while leaving only the particulate titanium oxide on the glass, and the corresponding deposition rate is therefore reported as 9 angstroem per second.

The procedure used in Examples 4 and 5 was the same as in the previous examples (reactor temperature and substrate were the same as in Example 1) except that the substrate was static-1799 9 99

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9 99 99 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 by a factor of five relative to the dynamic conditions.

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

EXAMPLE 6

A float glass manufacturing method was used to produce a continuous strip of 3 mm glass at a line speed of 11 meters per minute. At the desired titanium oxide coating point in the float bath section, the glass temperature was 615 ° C and a coating reactor similar to that shown in Figure 3 was used. The temperature in the precursor feed was 205 ° C and the reactor front temperature was 260 ° C. Prior to carrying out the process of the invention, a silica coating and a thickness of about 339 angstroem was applied to the glass substrate in the float bath section. The same chemical vapor deposition procedure as described in Example 1 was used to apply the silica coating. The silica coating does not form part of the invention.

A precursor gas mixture was formed containing titanium tetrachloride and ethyl acetate in helium as carrier gas. Oxygen was not used in the precursor mixture as a result of the previous examples showing that the coating reaction is not a feeling.

-18 sensitive to oxygen concentration. The precursor mixture was prepared by simultaneously feeding the three components through the distribution system. The composition of the precursor mixture by volume was 0.6% titanium tetrachloride, 1.8% ethyl acetate and 97.5% helium. The flow rates of the components were 480 l / min. helium, 3.0 rpm. titanium tetrachloride and 9.2 l / min. ethyl acetate. The total flow rate of the precursor mixture was 492 L / min.

The resulting titanium dioxide coating had a thickness of 684 angstroem. The carbon content of the coating was less than 2 atomic percent. The coating growth rate was 309 angstroem per second.

EXAMPLE 7

In the example, the same procedure was used as in Example 6. The substrate contained coatings of silicon followed by silica on the glass substrate. The coatings were deposited by a known chemical vapor deposition process in the float bath section. The silicon coating was applied by chemical vapor deposition from monosilane with a non-oxidizing gaseous carrier. The silica coating was then applied to the silicon coating using the same procedure as in Example 1.

The titanium oxide coating precursor contained titanium tetrachloride and ethyl acetate in helium as the carrier gas. The precursor composition was 0.5% titanium tetrachloride, 1.9% ethyl acetate and 97.6% helium by volume. The corresponding flow rates for the components were 480 l / min helium, 2.41 l / min. titanium tetrachloride and 9.2 l / min. ethyl acetate. The total flow rate of the precursor mixture was 491.6 l / min.

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The resulting coated article 52 is shown in FIG. The glass substrate 54 is shown with a stack of multiple coatings 56. The coatings comprise a layer of silicon 58, a layer 60 of silica and then a layer of coating 62 of titanium oxide on top of the article. The titanium oxide coating on the resulting product had a thickness of 836 angstroem. The optical properties of the resulting coating stack included an observed light transmittance of C 13.1% and an observed light reflectance of C 82.5%. The growth rate of the titanium oxide coating was 378 angstroem per second.

TAB.l

<td>Ex.</td><td>tíci₄</td><td>organ.oxygen. merge</td><td>oxygen</td><td>He</td><td>tl.Á</td><td>A / sec</td>

<td> 1</td><td> 0,2</td><td>4.8 ethyl acetate</td><td> 2,0</td><td> 20,9</td><td> 490</td><td> 150</td>

<td> 2</td><td> 0,5</td><td>1,6 ethyl formate</td><td> 6,0</td><td> 17,4</td><td> 800</td><td> 250</td>

<td> 3</td><td> 0,45</td><td>1,5 isopropanol</td><td> 4,0</td><td> 15,45</td><td> 0</td><td> 0</td>

<td> 4</td><td> 0,5</td><td>1,2 methyl formate</td><td> 6,0</td><td> 17,4</td><td> &lt;100</td><td> &lt;10</td>

<td> 5</td><td> 0,5</td><td>0.5 t-butyl acetate</td><td> 6,0</td><td> 17,4</td><td> 1300</td><td> 130</td>

EXAMPLES 8-13

In this series of examples, a static coating was used in a laboratory to deposit a tin oxide coating on a float glass substrate carrying a color suppressing silica layer produced by the method described in EP 0 275 662 B.

The coated float glass was carried on a nickel block «9 ·» ··· · ··· ···

9 9 9 9 9 9 9 ·» · ·· 9 99 99

The reaction vessel and the block were heated from below with electrical heating elements to obtain a glass temperature of 585 ° C. At a distance of approximately 10 mm above and parallel to the glass, a flat graphite plate was installed to create a 10 mm deep gas path between the surface of the glass supporting the silica layer and the plate.

A precursor gas mixture containing tin tetrachloride and an organic oxygen source in the air and a small amount of additional nitrogen as carrier gas was fed through the gas line, maintaining the temperature at 225 ° C ± 15 ° C and having a tail-shaped orifice to the flow path. gas over the hot glass in a direction that is generally parallel to the surface of the glass. The total volume flow of the carrier gas was 13 m³/throw. The volumetric flows of stannous chloride and the nature and volumetric flows of the organic compound used corresponded to those shown in the attached Table 2. In Examples 9 and 11, small amounts of hydrogen fluoride were incorporated into the precursor gas mixture to dope the resulting tin oxide coating with fluorine as indicated in the table.

The gaseous stream containing the reaction gases was fed for approximately 8 seconds and the coating apparatus and the coated glass were then allowed to cool in the presence of an air stream of 225 ° C. After dismantling the coating device, the gas supply line, orifice and plate defining the gaseous flow path across the glass were found to be free of deposit in each case, indicating that there was no undesired pre-reaction. In any case, the glass had a tin oxide coating formed on the silica, the thickness of the coating varying with the distance from the orifice in the shape of an ryφ tvaruφ··········φφφφφφφφφφφφφφφφφ···········φ φ φ φ φ φ &lt;&lt;&lt;&lt;&lt;

-21white tail. The maximum thickness and corresponding growth rate for each precursor gas mixture are shown in Table 2. The emissivity, resistivity and haze of samples of products using hydrogen fluoride to deliver a fluorine dopant (Examples 9 and 11) were measured, and the results were included in Table 2.

This series of examples shows that an organic oxygen source can be used as part of a premixed precursor gas mixture containing tin tetrachloride to deposit a tin oxide coating without significant undesired pre-reaction, detrimentally affecting the coating process, for example by deposition of tin oxide in the gas supply tubes. In addition, a source of dopant, such as hydrogen fluoride, can be incorporated into the preformed gas mixture to reduce the emissivity and resistivity of the coating, while still avoiding a significant detrimental pre-reaction.

EXAMPLE 14

In this example, a coating distributor, schematically shown in FIG. 4, was used in the float bath to deposit the tin oxide coating according to the method of the invention. The belt speed was approximately 350 m / hr. and the glass thickness was 1.2 mm. The glass temperature was approximately 630 ° C. The temperature of the gas supply tube 101, which served as the primary gas mixing chamber, was maintained at 150 ° C and the static manifold with the gas flow restrictor 105 was at a temperature of about 340 ° C. The vapors of tin tetrachloride and butyl acetate were passed by bubbling nitrogen through the liquids held at 80 ° C in scrubbers and then through individually cooled pipes into the gas supply tube 101. The vapors mixed in the primary chamber were passed through the separators. 99 · 99 · 99 · ft

22 with a gas flow restrictor and thereafter in laminar flow conditions through a U-shaped guide channel 106 comprising a coating chamber 108 opening onto a hot sheet of glass.

TAB. 2

<td>Example</td><td>SnCl flow rate₄</td><td colspan="2">organ.resource.of oxygen.</td><td>Flow</td>

<td></td><td>(ml / min)</td><td>Merge.</td><td>Flow</td><td>40% HF</td>

<td> 8</td><td> 12</td><td>ethyl acetate</td><td>(ml / min) 10</td><td>(ml / min)</td>

<td> 9</td><td> 12</td><td>ethyl acetate</td><td> 10</td><td> 1</td>

<td> 10</td><td> 12</td><td>butyl acetate</td><td> 13,4</td><td> -</td>

<td> 11</td><td> 12</td><td>butyl acetate</td><td> 13,4</td><td> 1,3</td>

<td> 12</td><td> 6</td><td>i sopropylalkoho1</td><td> 120</td><td> -</td>

<td> 13</td><td> 17</td><td>acid trifluoroacetic acid</td><td> 16,2</td><td></td>

<td>Example Max</td><td>Max.</td><td>Emisivita Rezis-</td><td>Ha</td>

<td>of tin oxide</td><td>growth A / sec</td><td>tivita</td><td></td>

ohm / cm

<td> 8</td><td> 2750</td><td> 344</td><td> -</td><td> -</td><td> -</td>

<td> 9</td><td> 2680</td><td> 335</td><td> 0,25</td><td>.5,3X10 “⁴</td><td> 0,4%</td>

<td> 10</td><td> 3460</td><td> 432</td><td> -</td><td> -</td><td> -</td>

<td> 11</td><td> 2880</td><td> 360</td><td> 0,25</td><td>6,9xl0 ~⁴</td><td> 0,6</td>

<td> 12</td><td> 2284</td><td> 262</td><td> -</td><td> -</td><td> -</td>

<td> 13</td><td> 2840</td><td> 335</td><td> —</td><td> —</td><td> -</td>

The flow rates were sufficient to obtain a molar of &amp; lt; 9 &amp; gt;

•

99 9

-239 9 9

9 9 • 99

9 9 ·

<img file="CZ9900402A3_D0012.tif" />

9

9999

9 9

9 9

9 • ratios of tin tetrachloride to butyl acetate from 1: 1 to 1: 5. If carried out for 5 hours. Upon removal of the coating, it was found that the cooled surfaces and associated coatings were more than 90% free of deposits, indicating that the tin tetrachloride and butyl acetate used for the coating of tin oxide on the glass can be premixed with each other without substantial pre-reaction. A tin oxide coating on a glass ribbon was obtained.

It will be appreciated that various changes and variations to the particular details of the invention set forth in the preceding examples may be made without departing from the spirit of the invention as described in the claims. In its essential details, the invention is a continuous gas-phase chemical deposition process for deposition of tin and titanium oxide coatings on a glass substrate at high deposition rates using the corresponding metal tetrachloride and organic compound used as the oxygen source in the preformed precursor gas mixture.

Metal tetrachlorides are preferred sources of the corresponding metals due to the availability and cost of the raw material.

It has been found that, in particular when coating titanium dioxide coatings from titanium tetrachloride to form metal oxide at optimal deposition rates, it is desirable to use an oxygen-containing organic compound which is an ester, especially an ester in which the alcohol-derived group is an β hydrogen alkyl group. Further, the decomposition temperature of the ester should not be greater than the reaction temperature of the precursor coating gas mixture at the desired deposition point. Esters used in precursors 111 111 1 111 24 24 9191 911 111

111 Visually gaseous mixtures having β hydrogen and suitable decomposition temperatures will result in deposition at high deposition rates. A preferred group of esters used in the practice of the invention comprises a group consisting of ethyl formate, ethyl acetate, ethyl propionate, isopropyl formate, isopropyl acetate, n-butyl acetate and t-butyl acetate.

The ester generally decomposes continuously over a given temperature range. According to the invention, the thermal decomposition temperature is defined as the temperature at which the rate of single molecular decomposition of the ester is 0.01 / sec. The single-molecular decomposition rate constants of conventional 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 thermal decomposition temperatures, as defined above, are 500 ° C and 344 ° C. One skilled in the art will recognize that the choice of ester and the particular deposition temperature used will determine optimal coating growth. Reaction temperatures below a defined thermal decomposition temperature, but with a range of decomposition of the selected ester, will result in lower coating growth rates.

According to the invention, the alkyl group of the ester used in the precursor coating gas mixture may be a carbon compound having 2 to 10 carbon atoms. The lower limit of the range is dictated by the requirement for the alkyl group to have β hydrogen. The upper limit is given to avoid the easy ignition and volatility that occurs when an alkyl group has more than ten carbon atoms.

In carrying out the method of the invention, the manifold can be used to connect and control the individual • 444 • 4 • 4 • * • 4

-2544 4444

4 • 4

4

4

4 • 4

4 4 4

4 4 4

444 4 44

4 gaseous streams to form a precursor coating gas mixture. A common feed line may be used to deliver the precursor gas mixture from the manifold to the beam gas distributor. A static mixer may be incorporated into the supply line to ensure the formation of a homogeneous gas mixture. In addition, the barriers in the beam gas distributor shown in FIG. 3, or the gas flow restrictor described with reference to FIG. 4, may provide further mixing of the precursor gas stream at the reactor stage.

In many of the examples, oxygen was introduced into the precursor gas mixture. However, the deposition rate of the metal oxide coating was not sensitive to oxygen concentrations, and no gaseous oxygen was used in Examples 6 or 7, indicating that the presence of oxygen was not necessary.

The concentration of the reactants of the precursor coating gas mixture can be selected to obtain an optimal growth rate. The metal tetrachloride concentration is generally 0.1 to 0.5 vol% of the precursor gas mixture. It is based on the amount of metal needed to achieve the desired coating thickness during the residence time available. The metal tetrachloride concentration is thus adjusted according to variable process parameters such as the speed of the strip line in the float glass manufacturing process.

The concentration of the oxygenated organic compound in the precursor gas mixture is generally up to one to five times the concentration of the metal tetrachloride, and is selected within this range based on the deposition temperature. When an ester is used, lower deposition temperatures will result in slower decomposition rates of es-

<img file="CZ9900402A3_D0013.tif" />

·* 9

-26♦ 9 999*

9· 9 • · • 9 9 • 9 · • 9 9 *

Thus, the mixture and the mixture will require higher ester concentrations to react with the metal tetrachloride. In Examples 6 and 7, the optimum concentration of ethyl acetate in the precursor gas mixture is 1 to 3 times the titanium tetrachloride concentration. Concentrations above and below the optimum range will result in metal oxide coatings with lower growth rates.

The temperature of the precursor gas mixture is critical to controlling the reaction, in particular to prevent an unwanted pre-reaction or adduct formation resulting from the formation of a non-volatile product in the precursor conduit. In one preferred embodiment, particularly suitable when using an ester, the temperature in the precursor gas lines is maintained above 150 ° C. The precursor gas mixture is also preferably kept below the thermal decomposition temperature of the organic oxygen compound to prevent the premixing of the mixture.

The method of the invention utilizes heat from the substrate to initiate the coating reaction. In line situations such as the float glass process, the substrate is formed at extremely high temperatures. The process according to the invention can therefore be carried out at the point of the float glass manufacturing process where the temperature of the substrate is lowered but is still above the temperature at which the coating is formed (and preferably after the glass ribbon has substantially finished stretching, i.e. below 750 ° C). ). Off-line applications of the invention will require heating the substrate to a temperature above the ester decomposition temperature.

In carrying out the method of the invention in the production of float glass, a preferred application point in the float bath section is preferred. The temperature range at the application site for coating is

<img file="CZ9900402A3_D0014.tif" />

<img file="CZ9900402A3_D0015.tif" />

4

4

-274 4 4

4 4

4 usually 590 ° to 715 ° C. Temperature is an important process operating parameter because it affects the concentration of the organic compound used in the precursor gas mixture. The substrate temperatures in the float bath section are relatively stable and therefore show slight variations at the point of application. In Examples 6 and 7 using ethyl acetate, the preferred range is 590 ° to 680 ° C.

The heat from the substrate raises the temperature of the precursor gas mixture above the temperature required for coating (and when the ester is used as an organic compound above the thermal decomposition temperature of the ester). The metal deposition reaction can be initiated by decomposition of the organic oxygen compound. When titanium tetrachloride is used in combination with an ester having an alkyl group with β hydrogen, titanium oxide coating is then formed on the substrate at decomposition rates that are ten times higher than known coating methods. When used on a line for producing a float glass ribbon, the ribbon passes below the beam gas distributor at a relatively high speed. The metal oxide coating is deposited on the float glass web as the web passes under the coating.

The authors propose the following theory concerning the chemical reaction that may occur when an ester having an alkyl group with β hydrogen is used. However, they do not wish to limit the invention to this very possible explanation and therefore offer them only as an aid to understanding the results of the method according to the invention.

The authors believe that when the ester decomposes, the carbon-hydrogen bonds on one of the β hydrogen and the hydrogen

-28«· ··«· ·

• · • » • *

9 t · «

9999 9 9

99

9 9 • · ·

999 999 ·

99 proceeds to the carbonyl group with the exclusion of alkene and formation of the carboxylic acid. At the same time, a hydrolysis reaction occurs between the carboxylic acid and the metal tetrachloride, leading to the formation of a metal oxide coating on the substrate.

The resulting product obtained according to the invention generally comprises a substrate coated with titanium oxide or tin oxide. The coating may be applied directly to the substrate or as a layer in multiple coatings on the substrate. The deposition rate of the metal oxide coating results from the rate of decomposition of the organic oxygen compound. At constant reaction temperatures, the different organic oxygen compounds will provide different growth rates due to the difference in decomposition temperatures. Thus, the desired growth rate of the metal oxide coating for the system is selected by combining the particular organic oxygen compound with the temperature of the precursor gas mixture and the temperature of the substrate at the point of application.

The deposition rate of the titanium oxide coating in the process of the invention may be ten times higher than the rates in known deposition methods. The method of the invention allows deposition rates greater than 130 Å per second, with some measured deposition rates even exceeding 300 Å per second. Higher deposition rates for titanium oxide provide a coating with a refractive index greater than 2.4.

A further advantage of the invention is, besides the achievable high deposition rates, that it uses inexpensive metal precursor compounds and that, especially when the precursor gas mixture is passed over the substrate under preferred laminar flow conditions, it allows high efficiency

-29·· ···· 9 · · • · · • · * • · 9 *9 * «· 9 • * · • · 9 *

9 9 9999

9 9

9

99

9 9 * • 9 9 9

999 ··* « 9

9-99 conversion (metal tetrachloride).

According to the 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 the high carbon contents of the coatings create absorption problems with the coating. When using an organic oxygen compound in the precursor gas mixture of the coating, it is feared that the decomposition would not lead to carbon contents that would adversely affect the absorption properties of the finished glass. The carbon content of the coatings produced by the process according to the invention showed a value of less than 4 atomic percent when measured. This low carbon content will not significantly affect the absorption properties of the coating.

It is to be understood that the embodiments of the invention illustrated and described herein are intended to be illustrative of the invention, and that various changes in the shape, dimensions and arrangement of parts, as well as various process changes, may be made without departing from the spirit of the invention.

9t ·· • ·

-30• · »

9 9

9·

9 *»

9 ·

· · • · •

• 9

9 9 *

99

9 9 9

9 9 9

999 999 ·

99

PATENT CLAIMS