Method of depositing tin oxide coatings on flat glass and the resulting coated glass

(54) Title: Processes for depositing a coating of tin oxide or titanium oxide on hot flat glass or on a substrate, and a glass substrate.

(30) Unionist Priority: iaoe / 1996 GB 9616983.4 (71) Depositor (s): Pilkington PIc (GB), Libbey-Owens-Ford Co. (US) (72) Inventor (s): David Willam Sheel, Richard J McCurdy , Simcn James Hurst (57) Abstract: -processes for depositing a TINNY OXIDE OR TITANIUM OXIDE COATING ON HOT VTDRO OR ON A SUBSTRATE, AND, GLASS SUBSTRATE. One, chemical vapor deposition process to space a tin oxide coating with titanium on hot glass using a compound containing organic oxygen and the corresponding metat tetrachloride. The organic oxygen compound is preferably an ester having an alkyl group with a hydrogen in order to obtain a high deposition rate. Due to the high deposition rates obtainable, typically less T30A, second. the process is suitable for depositing coatings of substantial thickness on a floating glass moving tape during the glass making process (74) Attorney: Momsen, Leonardos & Cia.

(86) International Order: PCTGB97 / 02t79de izoâ / 1997 (87) International Publication: wo 98 <O6675de 19.02 / 1998 “PROCESSES FOR DEPOSITING AN OXIDE COAT OF • t 4 4 · * · 4 · · 444 ·

TIN OR TITANIUM OXIDE ON jvnjRÓ -.PLANQ HOT OR ON UAI SUBSTRATE, AND, GLASS SUBSTRATE ”. BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a process for depositing coatings of titanium oxide and tin oxide on a flat glass substrate, and the resulting coated glass. More particularly, this invention relates to a chemical vapor deposition process to produce coatings of titanium oxide and tin oxide on flat glass using a mixture of coating precursor gas comprising the corresponding metal tetrachloride and an organic oxidizer.

2. Summary of Related Art

Titanium oxide and tin oxide coatings have been proposed for use in glass containers, for example bottles, to improve the mechanical strength of the containers. It was proposed to use both the titanium oxide coating and the tin oxide on flat glass to modify the characteristics of the glass for architectural use; titanium oxide coatings deposited under vacuum (by reactive spray) are used as components of multi-layered infrared reflection coatings, sprayed, while tin oxide coatings are used, not just as layers of sprayed multiple coatings layers, but also deposited pyrolytically with a dopant as electroconductive coatings and / or reflecting infrared.

The GB 1 115 342 patent report describes a process for producing glass containers with good inherent resistance and good resistance to abrasion by spraying the containers, while still hot from the manufacturing process, with a solution or dispersion of stannic chloride

Ί (ie, tin tetrachloride), in an organic liquid, isopropyl alcohol • AAA AA AAAAAAAA being preferred. A small amount of <-4br £ tô *; give tjtâíné -pctdd: ser · 44 A AA4444 4 A 4 incorporated as a modifier. The liquid solution is fed to atomizers, which can be of the pressure jet variety, located on both sides of a tunnel over a conveyor for hot glass bottles to produce a mist of liquid reagent, so that a layer of liquid is formed on all outer surfaces of the bottles while reacting to form a layer of tin oxide.

The GB 1 187 784 patent report describes an improvement of the process described in the GB 1 115 342 patent report and apparently more suitable for incorporation into a process for the automatic manufacture of glassware without interfering with the normal cycle of this process and without requiring additional supervision. The report proposes to treat glass containers, at high temperature, with a liquid solution of an organic tin compound whose compound has properties so that when heat is applied, it decomposes into two materials, one of which is an organic tin compound high decomposition temperature that reacts with the glass surface to produce a diffusion layer of tin oxide within the glass surface, while the other is a volatile tin compound so that a substantial proportion of vapor from said compound is produced, and subjecting the containers to a heat treatment so that a reaction is carried out between the glass on at least the surfaces of the containers and tin compounds. The material used for the treatment of glass containers can be provided by reaction of tin tetrachloride with organic substances containing carbonyl groups of moderate activity, for example organic esters, of ethyl, n-propyl, isopropyl, n-butyl and isobutyl alcohols , with acetic, propionic and butyric acids. The resulting solution can be sprayed, in the presence of an ambient atmosphere, on the hot containers, for example in the form of a fine mist after they leave the forming machine and before entering the fr fr · fr frfrfr fr fr fr frfr fr annealing. The GB 1,187 patent report^:; 7 £ 3 frés frfrfr frfrfrfrfrfrfrfr analog similar to that described in 1,187,784 in which an organic titanium compound is sprayed on the hot glass containers instead of the organic tin compound. The organic titanium compound can be produced, in a manner analogous to the organic tin compound, by reacting titanium tetrachloride with an organic ester, for example n-butyl acetate. The resulting solution is again sprayed onto the glass in the ambient atmosphere in the container production line.

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

Processes involving the use of gaseous reagents (also called CVD or chemical vapor deposition processes) have some advantages over spraying processes for coating flat glass, especially when the reagents can be pre-mixed before application to glass . Unfortunately, tin tetrachloride reacts readily with water so that previous proposals to use tin tetrachloride and water vapor in gaseous form were generally involved in supplying the gases separately from the glass surface and mixing it in contact with glass .

The patent report GB 2 044 137A refers to such a process in which discrete laminar currents for each reagent are formed and projected onto a hot glass substrate by joining the chains together in reciprocal tangential contact on the glass. Titanium tetrachloride can be used as one of the gaseous reagents, instead of tin tetrachloride, to form a titanium oxide coating. The patent also suggests • · · ··· »· ft · supplying hydrogen to one of the gas streams pajtf ajreiçtcj yicvt ^ nta between tin tetrachloride and water vapor. This can be done either by adding hydrogen gas directly, or by adding methanol, which is said to react in situ to produce the desired hydrogen gas.

The patent report GB .2 026 454B, describes a process in which a coating chamber is positioned on a hot float glass strip as it advances from the float bath and successive gaseous streams of (1) pre-carrier nitrogen gas -heated, (2) tin tetrachloride entrained in preheated nitrogen and (3) air, water vapor and hydrofluoric acid are introduced into the coating chamber as they flow along the glass substrate surface being coated as a substantially turbulence-free layer. The patent specifies the concentration of water vapor and tin tetrachloride in the gaseous medium on the glass.

European patent reports 0 365 239B1 and 0 376 240B1 describe a process and apparatus for depositing a tin oxide coating on a hot glass strip. A first gas stream of tin tetrachloride in preheated dry air is caused to flow along the surface of the hot glass strip advancing under the coating chamber, a second turbulent stream of hydrofluoric acid and steam introduced into the coating chambers at angles straight to the plane of the glass and direction of flow of the first gas stream, and the first and second combined gas streams drawn through the coating chamber on the glass under turbulent flow conditions. The process and apparatus can also be used to apply a titanium oxide coating using titanium tetrachloride instead of tin tetrachloride.

US patent 4,590,096 describes a process in which a coating solution comprising a substantially solvent-free mixture of an organo-tin chloride and an organic fluorine compound

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A * AA A AA · AA · AAA in a preheated vehicle gas stream that contains enough water vapor that the relative humidity of the gas stream at 18 ° C is about 6% to about 100%. The resulting gas stream is passed over a hot glass surface to deposit a fluorine-doped tin oxide coating on the hot glass. A wide range of organo-tin compounds can be used and the possibility of using tin tetrachloride is mentioned. Similarly, a wide range of organic fluorine compounds, including oxygen-containing compounds, for example trifluoroacetic acid and ethyltrifluoroacetate, can be used. Some of the fluorine-containing dopants have limited solubilities in the used organo-tin compounds, and an optional solubilizer can be used to increase the solubility of the fluorine dopant in the organo-tin compound; acetic anhydride, ethyl acetate, hexane, methyl isobutyl ketone and butyraldehyde are listed as non-limiting examples of the solubilizers that can be used. However, the US patent, in common with the other patents using chemical vapor deposition processes to deposit a metal oxide from a gaseous metal tetrachloride, uses water vapor as the oxygen source.

US patent 4 751 149 Vijaykumar et al refers to the deposition of zinc oxide coatings by deposition of chemical vapor at low temperature (60 ° to 350 ° C, preferably 100 ° to 200 ° C) on heat sensitive photoconductive substrates, and proposes to deposit the zinc oxide coatings of an organozinc compound and an oxidizer, which can be an organic compound containing oxygen, for example an ester, and an inert carrier gas. Although the patent is not completely evident, it apparently proposes to introduce separate streams of the organozinc and oxidant compound in the deposition chamber, and there is certainly no proposal to pre-mix these components together before the coating chamber is released.

It would be advantageous to provide a process for depositing titanium oxide or tin coatings per process: CVB: applied to hot flat glass using a premix of the corresponding methyl tetrachloride as a low cost reagent and an oxygen source without premature reaction between the metal tetrachloride and the oxygen source (previously water) resulting in the formation of .metal oxide in the coating equipment with the consequent problems and inefficiency. It would be particularly advantageous if the process allowed for deposition of the coating at high rates, allowing for a required coating thickness to be deposited on a moving glass strip during the glass making process.

SUMMARY OF THE INVENTION

According to the present invention, a chemical vapor deposition process is provided to spread a coating of titanium oxide or tin oxide on a hot glass substrate, using a mixture of precursor gas containing the corresponding metal tetrachloride and a organic source of oxygen, without requiring the inclusion of water vapor and the consequent risk of premature reaction.

The present invention provides a process for depositing a coating of tin oxide or titanium oxide on hot flat glass comprising the steps of:

(a) preparing a mixture of precursor gas containing the corresponding metal tetrachloride and a compound containing organic oxygen as an oxygen source for forming the metal oxide;

(b) maintaining said precursor gas mixture at a temperature below the temperature at which the metal tetrachloride reacts to form the metal oxide while releasing the mixture to a coating chamber opening on the hot glass, (c) introducing the mixture precursor gas in the

Ί coating so the mixture is heated to cause deposition of the oxide of • * - ^ · ** 4 «, * * corresponding metal incorporating oxygen from the <iom | 3rd * stan big: sotírè a> -> ft ftftft · ** · ft hot glass surface.

Surprisingly, a wide range of organic compounds containing oxygen can be used as the oxygen source, without requiring the presence of d¹ water or gaseous oxygen, including compounds normally considered to be reducing agents instead of oxidizing agents, for example alcohols. However, the preferred organic compounds are carbonyl compounds, especially esters; and particularly good results were obtained using esters having an alkyl group with a hydrogen. The alkyl grit with hydrogen will normally contain two to ten carbon atoms.

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

Particularly preferred esters for use in the practice of the present invention include ethyl formate, ethyl acetate, ethyl propionate, isopropyl formate, isopropyl acetate, n-butyl acetate, and t-butyl acetate.

The process of the present invention is generally practiced in connection with the formation of a continuous glass ribbon substrate, for example during a flat glass production process. However, the process of the present invention can be employed in the coating of other flat glass substrates in line or out of line.

The present invention involves the preparation of a precursor gas mixture that includes tin or tin tetrachloride and a compound containing organic oxygen; a carrier gas or diluent, for example nitrogen, air or helium, will normally also be included in the gas mixture. Because the thermal decomposition of the organic oxygen-containing compound 'β * * - 6 * a * · can initiate the metal oxide deposition reaction htn.'úríia', alias tAxhâ is' * 6 4 * 444 «1 4 precursor mixture is maintained at a temperature below the temperature of thermal decomposition of the organic oxygen compound to avoid the pre-reaction of the gas mixture with the formation of metal oxide.

The gas mixture is kept at a temperature below that which will react to form the metal oxide, and released at a location close to the flat glass substrate to be coated, the substrate being at a temperature above that reaction temperature (and above decomposition temperature of the organic oxygen compound in the precursor gas mixture).

The precursor gas mixture is then introduced into the vapor space directly on the substrate. The heat of the substrate raises the temperature of the precursor gas above the thermal decomposition temperature of the organic oxygen compound. The organic oxygen compound then decomposes in reaction with the metal tetrachloride producing a coating of metal dioxide on the substrate.

The present invention allows the production of titanium oxide and tin coatings deposited on hot glass at a high deposition rate, for example 130A / second and, in preferred embodiments, above 250A per second.

The deposition rate is dependent on the particular organic oxygen-containing compound used, and the concentrations of both organic oxygen-containing compound and metal chloride, as well as the temperature of the glass. For any particular combination of compounds, the optimal concentrations (and particularly the optimal ratio of compound containing organic oxygen to metal tetrachloride) and flow rates for rapid coating deposition can be determined by simple attempt. However, it will be noted that the use of higher concentrations of reagents and high gas flow rates will likely result in a uma Β Β BB ♦ · · · B 46 · 6 Β · Β B BBB overall conversion less efficient of the reactants in the re-estimation, and ** that the optimum condition for commercial operation may differ from the conditions that provide the highest deposition rates.

Preferably, the orga nic oxygen-containing compound will be at a volume concentration of about 0.5, especially 1 to 5 times the volume concentration of the metal chloride. It will be commonly used in an amount of at least 30% by weight of the weight of the metal chloride.

The process of the invention allows the production, at high rates, of titanium oxide and tin oxide coatings on hot flat glass substrates in-line during the glass making process. Titanium oxide coatings can be produced with a high refractive index (at least 2.4) allowing the desired optical effects to be achieved, especially when used in combination with other coating layers. Tin oxide coatings can be doped, for example with fluorine, by incorporating an appropriate precursor to the dopant in the precursor gas mixture, increasing the electrical conductivity and infrared reflectivity of the coatings, and thus their usefulness as electrical conductive coatings. and / or low-emissivity coatings in varnishes for architecture and other applications.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of preferred embodiments when considered in the light of the accompanying drawings, in which:

Figure 1 is a schematic view of a vertical section of an apparatus for practicing a float glass process that includes gas distributors appropriately positioned to allow the practice of the process of the present invention.

Figure 2 is a broken section view of a valid.ar.vgQ • A · 4 44 * 44444 44

44434 · 4 44444 4 according to this invention, and: *: /: ·: · '. · * · * * · *

Figure 3 is an enlarged schematic end view of a gas distributor beam suitable for use in the practice of the present invention.

Figure 4 is an enlarged schematic end view of an alternative gas distributor beam that can be used in the practice of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference now more particularly to the drawings, a float glass installation generally shown in Figure 1 is used as a means for practicing the process of the present invention. The float glass apparatus more particularly comprises a channel section 12 along which a molten glass 14 is released from a melting furnace (not shown), to a float bath section 16 in which a continuous glass strip 18 it is formed according to the well-known flotation process. The glass strip 18 advances from the bath section 16 through an adjacent annealing lehr 20 and a cooling section 22. The continuous glass strip 18 serves as the substrate on which the metal oxide coating is deposited according to the present invention.

The float section 16 includes a bottom section 24 within which a molten tin bath 26 is contained, a ceiling 28, opposite side walls 30, and end walls 32. The ceiling 28, side walls 30, and end walls 32 together they define a room 34 in which a non-oxidizing atmosphere is maintained to prevent oxidation of the molten tin.

Additionally, gas distributor bundles 64, 66 and 68 are located in the bath section 16. The gas distributor bundles 64 and 66 in the bath section can be used to apply additional coatings to the substrate before applying the oxide coating. titanium and tin by the process of the present invention. Additional coatings may include silicon and silica. : *:.? : * · * * · * * · *

In operation, the molten glass 14 flows along the channel 36 under a regulating tool 38 and downwardly on the surface of the tin bath 26 in controlled quantities. In the tin bath, the melting glass spreads laterally under the influence of gravity and surface tension, as well as some mechanical influences, and is advanced through the bath to form the ribbon 18. The tape is removed on withdrawal rollers 40 and then transported through the annealing lehr 20 and the cooling section 22 on aligned rollers 42. The application of the coating of the present invention can occur in the floating bath section 16, or more at the same time. along the production line, for example in the interval between the float bath and the annealing lehr, or in the annealing lehr.

An appropriate non-oxidizing atmosphere, usually nitrogen or a mixture of nitrogen and hydrogen in which nitrogen predominates, is maintained in the bath enclosure 34 to prevent oxidation of the tin bath. Atmospheric gas is admitted through conduits 44 operatively coupled to a distribution pipe 46. Non-oxidizing gas is introduced at a rate sufficient to compensate for normal losses and maintain a light positive pressure, of the order of about 0.001 to 0.01 atmospheres above ambient atmospheric pressure, in order to avoid infiltration of the external atmosphere. Heat to maintain the desired temperature regime in the tin bath 26 and the enclosure 34 is provided by radiant heaters 48 within the enclosure. The atmosphere within lehr 20 is typically atmospheric air, while the cooling section 22 is not closed and the glass strip is opened to the ambient atmosphere. Ambient air can be directed against the glass strip as by fans 50 in the cooling section. Heaters (not shown) can also be provided within the annealing lehr to cause the temperature of the glass strip to be gradually reduced according to a predetermined regime as it is transported through it.

frfrfrfrfrfr · frfrfr ** fr fr * ·

Figure 1 illustrates the use of dtstribnwldresídeigá 64 / -66 and

68, positioned in the float bath 16 to deposit the various coatings on the glass tape substrate. The gas distributor beam is a form of reactor that can be employed in the practice of the process of the present invention.

A convenient configuration for the distribution beams suitable for supplying the precursor materials according to the invention is generally shown in a diagram in figure 3. A frame work generally in the form of a channel, inverted, 70, formed by spaced outer and inner walls 72 and 74 defines closed cavities 76 and 78. An appropriate heat exchange medium is circulated through closed cavities 76, 78 in order to keep the distributor bundles at a desired temperature.

The precursor gas mixture is supplied through a fluid-cooled supply line 80. The supply line 80 extends along the distributor beam and admits the gas through drop lines 82 spaced along the supply line. Supply line 80 leads to a release chamber 84 within a head 86 carried by the frame. The precursor gases admitted through the drop lines 82 are discharged from the release chamber 84 through a passage 88 towards a coating chamber defining an opening of vapor space on the glass, where they flow along the surface of the glass IS in the direction of the arrows in figure 3.

The bulkhead plates 90 can be provided inside the release chamber 84 to equalize the flow of precursor materials through the distributor beam to ensure that the materials are discharged against the glass 18 in a smooth, laminar, smooth flow, completely through the beam distributor. The spent precursor materials are collected and removed through the exhaust chambers 92 along the sides of the distributor beam.

Various forms of distributor beams used for the deposition of a * · · «· · · · * ·· chemical vapor are suitable for the present prüceíso.'fe: sãá * GàíiKêdiClâ ^ in the prior art.

Such an alternative spreading beam configuration is illustrated schematically in figure 4 of the drawings. Using this distributor, which is generally designated 100 (and more fully described in European patent EP 0 305 102B), the precursor gas mixture is introduced through a gas supply duct 101 where it is cooled by cooling fluid circulated through ducts 102 and 103. The gas supply duct 101 opens through an elongated opening 104 in a gas flow limiter 105.

The gas flow limiter 105 is of the type most fully described in United Kingdom patent reports GB 1 507 996, and comprises a plurality of longitudinally corrugated metal strips in the form of a sine wave and vertically mounted in relation to one another. another extending along the length of the distributor. The adjacent corrugated metal strips are arranged out of phase to define a plurality of vertical channels between them. These vertical channels are of small cross-sectional area with respect to the cross-sectional area of ​​the gas supply duct 101, so that the gas is released from the gas flow limiter 105 at a substantially constant pressure along the length of the distributor .

The coating gas is released from the gas flow limiter on the inlet side 107 of a generally designated U-shaped guide channel 106 comprising inlet leg 107, coating chamber 108 which opens on the hot glass substrate 110 to be coated, and exhaust leg 109, when used the coating gas is removed from the glass. The rounded corners of the blocks defining the coating channel promote a uniform laminar flow of coating parallel to the glass surface through the glass surface to be coated.

The following examples (where. The gas yolnpiçs are 4 Λ 4 * 4 444 * 4 ^ 4 ^ expressed under standard conditions, this is a pifession> Zkí attnekfèra'-ê 'at room temperature, except in others terms), are presented for the purpose of further illustrating and describing the present invention, and should not be construed as a limitation of the invention:

Examples 1 to 5

In the series of examples, a bidirectional coating reactor of the type shown in figure 3 was used in the laboratory to deposit a titanium oxide coating.

In examples 1, 2 and 3, the glass was heated in a conveyor oven to simulate the coating reaction conditions of a float process in order to test the process of the present invention. The stove used in-line rollers to transport a glass substrate through a heating zone before practicing the process of the present invention. In example 1, the glass substrate was float glass that had initially been provided with a silica coating. The silica coating was deposited on the float glass through a known chemical vapor deposition process using a monosilane precursor in an oxygen-enriched atmosphere. The deposition of silica is not part of the present invention.

In accordance with the present invention, a titanium oxide coating was deposited on the silica-coated substrate. The substrate was at a temperature of 630 ° C and the substrate line speed was 8 meters per minute.

To deposit titanium oxide, a mixture of precursor gas was developed comprising tin tetrachloride, ethyl acetate, oxygen and helium. Helium was included in the precursor mixture as a vehicle for the reagents. The precursor mixture was prepared by simultaneously introducing all four gas streams through a piping system. A static in-line mixer was used, to make a · AAA AA

AAA AA A en1 · tf <5lhirfe 'of the homogeneous precursor mixture. The composition Epetcertttial · precursor mixture was 0.7% titanium tetrachloride, 17.2% ethyl acetate, 7.2% oxygen, and 74.9% helium, with flow rates for the components in the pipeline being as shown in the attached table 1.

The temperature of the precursor mixture was maintained above 150 ° C in order to avoid the reaction of titanium tetrachloride and ethyl acetate adduct. The precursor temperature was also kept below the thermal decomposition temperature range 510 ° C - 610 ° C of ethyl acetate in order to avoid the pre-reacting mixture.

The precursor mixture was introduced into the reactor just above the moving substrate. The temperature in the precursor tower was 120 ° C. The temperature on the face of the reactor was 175 ° C. The higher substrate temperature initiated the thermal decomposition of ethyl acetate, which then resulted in the deposition of titanium oxide.

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

In examples 2 and 3, the coating procedure specified in example 1 was repeated, except that in example 2 ethyl format was used as the organic source of oxygen, and in example 3 isopropanol was used as the organic source of oxygen and non-glass coated (instead of the silicon oxide coated glass of examples 1 and 2) was used as the substrate. The gas flow rates used and, in the case of example 2 * the thickness

5 *, 1, ** * · J * · · * · · 'titaitio .prtfdú2idô £ * £ ão and growth rate of the oxide coating shown in table 1. In example 3, the isopropanol burned in the reactor leaving only oxide of titanium particles on the glass, the corresponding deposition rate being quoted as OÂ / second.

The procedure for examples 4 and 5 was as used in the previous examples (the reactor and substrate temperature being identical to example 1), except that the substrate was static and not dynamic. The static sample was placed under the reactor for 10 seconds. Under static conditions, the residence time of the substrate under the reactor is increased from dynamic conditions by a factor of five.

In example 4, methyl acetate was used as the organic source of oxygen, and in example 5 t-butyl acetate was used; in each case, titanium oxide coating was produced. The gas flow rates, resulting titanium oxide coating thickness and coating growth rates are as shown in table 1. The relatively slow growth rate obtained using methyl acetate is discussed below.

Example 6

A flotation gas process was used to produce a continuous glass strip having a thickness of 3 mm at a line speed of 11 meters per minute. The glass temperature was 615 ° C at the desired point of application in the floating bath section of a titanium oxide coating using a coating reactor similar to that shown in figure 3. The temperature in the precursor tower was 205 ° C on the reactor face at 260 ° C. Before practicing the process of the present invention, a silica coating was deposited on the glass substrate in the float bath section at a thickness of about 339Â °. The same chemical vapor deposition process as described in example 1 was used to deposit the silica coating. The deposition of silica is not part of the present invention.

The precursor mixture was developed comprising · · · · ·· * titanium tetrachloride and ethyl acetate in the vehicle gas Tôélid- Gxícfenrrt.fiâo was used in the precursor as a result of previous examples indicated that the coating reaction was not sensitive to the concentration of oxygen. The precursor mixture was prepared by simultaneously introducing the three components through a piping system. The percentage composition by volume of the precursor mixture was 0.6% titanium tetrachloride, 1.8% ethyl acetate, and 97.5% helium. The flow rates for the components were 480.0 1 / m helium, 3.0 1 / m titanium tetrachloride, 9.2 1 / m ethyl acetate. The total flow rate of the precursor mixture was 492.2 1 / m.

The resulting titanium oxide coating was 684Â thick. The carbon content of the coating was less than 2 percent atomic. The growth rate of the coating was 309Â per second. Example 7

The same procedure for example 6 was used in this example. The substrate comprised silicon coatings and then silica on the glass substrate. The coatings were deposited by a chemical vapor deposition process known in the floating bath section. The silicon coating was deposited by CVD from monosilane with a non-oxidizing carrier gas. The silica coating was then deposited on the silicon coating using the same procedure as described in example 1.

The precursor to the titanium oxide coating included titanium tetrachloride and ethyl acetate in the helium carrier gas. The percentage composition in volume of the precursor was 0.5% titanium tetrachloride, 1.9% ethyl acetate, and 97.6% helium. The corresponding flow rates for the components were 480.0 1 / m helium, 2.4 1 / m titanium tetrachloride, 9.2 1 / m ethyl acetate. The total flow rate of the precursor mixture was 491.6 1 / m.

The resulting coated article 52 is illustrated in figure 2. O * -^J ft * «ft ftftft ft ft ftftft · ft ft 1 ftftft ft ftftft ftft ft glass substrate 54 is shown with a stack üe rev2siimèntGs^:Multiples 56. The coatings comprise a layer of silicon 58, a layer of silica 60, then a coating of titanium oxide 62 on top of the article. The titanium oxide coating on the resulting article was 836 µ thick. The optical properties of the resulting coating stack included an observed illuminance C transmittance of 13.1% and an observed illuminant C reflectivity of 82.5%. The growth rate of titanium oxide coating was 378À per second.

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Examples 8-13 · »&gt; · * fc 4 4 &lt;66 6

In the series of examples, a revestant Jesl ^ tiÒo; fo {laboratory for applying a coating of tin oxide on a float glass substrate carrying a layer of color-suppressing silicon oxide produced as described in European patent EP 0275 662B.

The float glass to be coated was. supported on a level block in a reactor vessel and the block heated from below by electric heating elements to provide a glass temperature of 585 ° C. A flat graphite plate was mounted approximately 10 mm above the glass and parallel to it to provide a 10 mm deep gas flow path between the glass surface containing the silicon oxide layer and the plate.

A mixture of precursor gas containing tin tetrachloride and a source of organic oxygen, in air and a small proportion of additional nitrogen as the carrier gas, was released through a gas line maintained at a temperature of 225 ° C + 15 ° C, and provided with a fish tail spout opening over the gas flow path over the hot glass in a general direction parallel to the glass surface. The total vehicle gas flow rate was 13 m³/hour. The flow rates of tin tetrachloride, and the nature and flow of organic compound used, were as shown in the attached table 2. In examples 9 and 11, small amounts of 40% hydrogen fluoride were incorporated into the precursor gas mixture to dope the resulting tin oxide coating with fluorine, as shown in the table.

The gas flow containing the reactant gases was applied for approximately 8 seconds, and the coating and coated glass apparatus was then allowed to cool under a flow of air at 225 ° C. When dismantling the coating device, the release gas line, nozzle and plate defining the gas flow path over the glass that was found to be free, in each case, from the deposit, indicating an absence of undesirable pre-reaction. In each case, the glass had a tin oxide coating applied over silicon oxide, the thickness of the coating varying diatànciã.Hcr * bíco * pm3 * abQ'de • 4 4 4 A · A * AAAAA · fish. The maximum thickness and corresponding growth rate for each precursor gas mixture used is shown in table 2. The emissivity, resistivity and turbidity of the samples produced using hydrogen fluoride to incorporate a fluorine dopant (examples 9 and 11) were measured and the results recorded in table 2.

This series of examples shows that an organic oxygen source can be used as part of a pre-blended precursor gas mixture comprising tin tetrachloride to deposit a tin oxide coating without significant undesirable pre-reaction adversely affecting the coating process, for example by depositing tin oxide in the gas supply ducts. In addition, if desired, a dopant source, such as hydrogen fluoride, can be incorporated into the gas premix to reduce the emissivity and resistivity of the coating while continuing to avoid significant harmful pre-reaction.

Example 14

In this example, a coating distributor, as illustrated in the diagram in figure 4, was used in a flotation bath to apply a tin oxide coating by a process according to the invention. The speed of the tape was approximately 350 cm per hour and the thickness of the glass was 1.2 mm. The glass temperature was approximately 630 ° C. The temperature of the gas supply duct 101 that served as a primary gas mixing chamber was maintained at 150 ° C and the static waffle gas distributor ”105 was approximately 340 ° C. The tin tetrachloride and butyl acetate vapors were released by bubbling nitrogen through liquids kept at 80 ° C in bubblers and thus through separate heated ducts to the gas supply duct 101. The vapors mixed in the primary chamber, passed through the packaging gas distributor Vafflêi è: ehiãei, sqò • * »· *» ·· ··. · * Laminar flow conditions through U-shaped guide channel 106 comprising opening of coating chamber 108 on the hot glass strip.

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TABLE 2

Example Mixture of precursor gas Thickness of Ernissivity Rate Resistance of growth oxide ohin / cin * 7

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The flow rates used were sufficient to obtain relations flfl fl fl fl · fl fl fl flflfl fl mol of tin tetrachloride: bijtila acetate: dbjofltré 1J1: Q Tift *: A fl fl flfl fl fl fl · · · fl fl fl fl attempt was performed for 5 hours. Upon dismantling the coating, it was found that the cooled surfaces and associated conduits were above 90% free of deposits, thus showing that tin tetrachloride and butyl acetate used to produce a coating of tin dioxide on glass can be pre- mixed with each other without substantial pre-reaction. A thin tin oxide coating was obtained on the glass strip.

It will be noted that various changes and modifications can be made to the specific details of the invention as incorporated in the examples above without departing from the spirit and scope of the same as defined in the appended claims. In its essential details, the invention is a continuous chemical vapor deposition process to spread coatings of tin oxide and titanium oxide on a glass substrate at high deposition rates through the use of the corresponding metal tetrachloride and a used organic compound as an oxygen source in a preformed precursor gas mixture.

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

It has been found, especially when depositing titanium tetrachloride titanium oxide coatings that, in order to form metal oxide at optimal deposition rates, it is desirable to use a compound containing organic oxygen which is an ester, particularly an ester in which the alcohol-derived group is an alkyl group with a hydrogen. In addition, the decomposition temperature of the ester should not be higher than the reaction temperature of the precursor coating gas mixture at the desired point of application. The esters used in the precursor gas mixture that have a hydrogen and appropriate decomposition temperatures will deposit the coatings at high deposition rates. The preferred group of esters used in the practice of the present invention includes the group consisting of ethyl formate, ethyl acetate, ethyl propionate, ifaphtho-de; ii4pj * çpl | a,

I * * frfr fr frfrfr frfrfr frfrfr isopropyl acetate, n-butyl acetate and t-butyl acetate.

In general, an ester decomposes continuously in a given temperature range. In the present invention, the thermal decomposition temperature of the ester is defined as the temperature at which the ester unimolecular decomposition rate constant is 0.01 / second. The unimolecular decomposition rate constants of 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 thermal decomposition temperatures using the above definition are 500 ° C and 344 ° C, respectively. One skilled in the art will recognize that the choice of ester and specific deposition temperature employed will determine the optimal coating growth rate. Reaction temperatures below the defined thermal decomposition temperature, but within the decomposition range of the selected ester, will result in lower growth rates of the coating.

According to the present invention, the alkyl group of an ester used in the coating precursor gas mixture can be a carbon compound having a range of 2-10 carbon atoms. The lower limit of the range is dictated by the requirement for hydrogen in the alkyl group. The upper limit is to avoid the flammability and volatility aspects that arise when the alkyl group contains more than ten carbon atoms.

In the practice of the process of the present invention, a pipe can be used to connect and regulate the individual gas streams to formulate the precursor coating gas mixture. A common release line can be used to release the precursor gas mixture from the pipeline to the gas beam distributor. A static in-line mixer can be used on the release line to ensure a homogeneous gas mixture.

Additionally, the bulkheads in the gas distribution beam, illustrated in the figure

I * · * | 4 4 4 444 4

3. or a gas flow limiter as described in detail; à · fi ^ rpjd, may provide another mixture of the precursor gas at the reactor stage.

In many of the examples, oxygen was included in the precursor coating gas mixture. However, the deposition rate of the metal oxide coating was not sensitive to oxygen concentrations, and oxygen gas was not used in examples 6 or 7 showing the inclusion of oxygen as being unnecessary.

The concentration of reactive coating precursor gas mixture components can be selected to obtain the optimal coating growth rate. The concentration of metal tetrachloride is generally 0.1 to 5.0 volume percent in the precursor gas mixture. The concentration of metal tetrachloride is based on the amount of metal needed to provide the desired coating thickness in the available residence time. Thus, the concentration of metal tetrachloride is adjusted according to the process variables, such as the in-line speed of the tape in a float process.

The concentration of the organic oxygen compound in the coating precursor gas mixture is generally one to five times the concentration of metal tetrachloride, being selected in this range based on the deposition temperature. When using an ester, lower deposition temperatures will result in slower rates of ester decomposition and thus will require higher concentrations of the ester to react with metal tetrachloride. In examples 6 and 7, the optimal concentration of ethyl acetate in the precursor gas mixture is 1 to 3 times the concentration of titanium tetrachloride. Concentrations above or below the optimum range will produce metal oxide coatings at lower coating growth rates.

The temperature of the precursor gas mixture is critical to control the reaction, particularly to avoid undesirable pre-reaction or «ft * # ft · * *« ft t adduct formation resulting in the formation of a pSL: ôdUtS; içVÔtátj | i ^ liÚKas * · · ft ft ft ftft ft ft · ft ft precursor ft. In a preferred embodiment, especially applicable when using an ester, the temperature is maintained above 150 ° C in the precursor gas lines. The precursor gas mixture is also preferably below the thermal decomposition temperature of the organic oxygen compound to avoid pre-reaction of the mixture.

The present inventive process uses heat from the substrate to initiate the coating reaction. In in-line situations, such as the float glass process, the substrate is formed at extremely high temperatures. Thus, the process of the present invention can be applied to a point in the float 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 tape has substantially finished the process). stretching, that is below 750 ° C. The offline applications of the present invention will require heating the substrate to a temperature above the decomposition temperature of the ester.

In the practice of the process of the present invention in the float glass process, the preferred point of application is in the float bath section. The temperature range at the point of application for the coating is generally around 590 ° -715 ° C. Temperature is an important operating parameter because it influences the concentration of the organic compound used in the precursor gas mixture. The substrate temperatures in the floating bath section are relatively stable and thus show little variation at the point of application. In examples 6 and 7 using ethyl acetate, the preferred substrate temperature range is 590 ° C -680 ° C.

The heat of the substrate raises the temperature of the precursor gas mixture above the temperature required for coating formation (and when using an ester as the organic compound above the thermal decomposition temperature of the ester). The metal deposition reaction can be initiated by the decomposition of the oxygen-gas compound. i ^ uàrfdjyàejbsa

4 44 4 444 ··· 444 titanium tetrachloride in combination with an ester having an alkyl group with a hydrogen, the titanium oxide coating then forms on the substrate at decomposition rates that are ten times greater than known coating processes . In a linoleum application with a float glass tape process, the tape passes under the gas distributor beam at a relatively quick rate. The metal oxide coating is deposited on the float glass tape as the tape passes under the coating.

The inventors propose the following theory regarding the chemical reaction that can occur when using an ester having an alkyl group with hydrogen. However, the inventors do not wish to limit the invention to just this possible explanation, and thus offer it only as an aid to understanding the results of the present inventive process.

The inventors propose that the ester breaks down, the carbon-hydrogen bond in one of the -hydrogens breaks down and the hydrogen transfers to the carbonyl group eliminating an alkene and forming a carboxylic acid. The hydrolysis reaction occurs simultaneously between the carboxylic acid and the metal tetrachloride leading to the formation of the metal oxide coating on the substrate.

In general, the resulting article produced in accordance with the present invention comprises a substrate having a coating of titanium oxide or tin oxide. The coating can be applied directly to the substrate or as a layer in a plurality of coatings on a substrate. The rate of deposition of the metal oxide coating is effected by the rate of decomposition of the organic oxygen compound. At constant reaction temperatures, different organic oxygen compounds will provide different rates of coating growth due to the difference in decomposition temperatures. Thus, the desired metal oxide coating growth rate for a given system is selected frfr fr fr frfrfr frfrfr frfrfr fr by adjusting an organic oxygen compound es |&gt; êc | fiô &lt;} p'ar4 a | einj3 ^ çaura mixture of precursor gas and the substrate temperature at the point of application.

The deposition rate of the titanium oxide coating in the present invention can be ten times greater than rates in known deposition processes. The present inventive process allows for deposition rates above 130� per second with some deposition rates measured well above 300�

A per second. Higher deposition rates for titanium oxide give a coating with a refractive index greater than 2.4.

Another advantage of the invention, in addition to the high coating rates obtainable, is that it employs low-cost metal precursor compounds and, especially when the precursor gas mixture is directed over the substrate under preferred laminar flow conditions, it allows a high efficiency of conversion (of metal tetrachloride) to be obtained.

In the present invention, the resulting oxide coating contains little residual carbon from the decomposition of organic oxygen compound, especially when using an ester. Carbon is an undesirable by-product of the coating reaction due to the high levels of carbon in the deposition coatings create absorption problems with the coating. The concern with using an organic oxygen compound in the precursor coating gas mixture is that the decomposition will result in carbon levels that adversely affect the absorption properties of the finished glass. The carbon content in the coatings produced from the process of the present invention shows less than four atomic percent of carbon, where measured. This low carbon level does not significantly affect the absorption properties of the coating.

It will be understood that forms of the invention shown and described herein should be taken as illustrative embodiments only of the same, and that various changes in the shape, size and disposition of parts, as well as changes in procedures, may suggest | sêt} i; 5aif d &lt;$

44 444

44 4 4

4 4 4 4

Spirit of invention.