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

METHOD FOR DEPOSITING TIN OXIDE AND TITANIUM OXIDE COATINGS ON FLAT GLASS AND THE RESULTING COATED GLASS

The present invention relates to a method for depositing a titanium oxide and tin oxide coating on a flat glass substrate and to a glass coated therewith. In particular, the present invention provides a method for forming titanium oxide and tin oxide coatings on plate glass using a coating precursor gas mixture comprising a corresponding metal tetrachloride and an organic oxidant. It relates to a method of chemical vapor deposition.

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 titanium oxide and tin oxide coatings on plate glass to modify the properties of architectural glass, the titanium oxide coating deposited in vacuum (by active sputtering) being a sputtered multilayer infrared reflective coating. -layer infrared reflecting coatings) and the tin oxide coating is pyrolytically deposited with a dopant as an infrared reflecting coating or conductive coating as well as used as a multilayer sputtered coating layer.

British Patent Application No. 1 115 342 discloses good intrinsic and abrasion strength by dissolving or dispersing stannic chloride (i.e. tetrachloride) in an organic liquid in which isopropyl alcohol is preempted by spraying it into a vessel at a high temperature in a manufacturing process. A method for manufacturing a glass container having A small amount of titanium chloride may be added as a modifier. Positioned on one side of a tunnel over a conveyor for hot glass vessels to create a 'mist of liquid reagent' to cause a liquid layer to form on all exterior surfaces of the vessel reacting to form the tin oxide layer The liquid solution is supplied to an atomiser, which may be a variety of pressure jets that are

British Patent No. 1 187 784 discloses an improved method over the method disclosed in British Patent No. 1 115 342, which is incorporated into the automated process of manufacturing glassware without any interference or additional control in the normal performance of said method. very suitable for The British Patent No. 1 187 784 proposes to treat a glass container at a high temperature with a liquid solution of an organotin compound, which "is a compound having the property of decomposing into two substances by the application of heat, two One of the materials is an organotin compound having a high decomposition temperature that reacts with the glass surface to create a diffusion layer of tin oxide on the glass surface, and the other is an organic tin compound that is produced at an actual vapor ratio between the glass and the tin compound on the surface of the vessel at least. It is a volatile compound of tin that allows it to react in Materials used in the treatment of glass containers contain suitable active carbonyl groups, such as, for example, acetic, propionic, organic ethyl esters with butyric acid, n-propyl, isopropyl, n-butyl and isobutyl alcohols. Tin tetrachloride may be provided by reaction with the containing organic material. The resulting solution is sprayed onto the hot vessel in the form of a fine mist before entering the annealing lehr after the vessel leaves the manufacturing machine and remains in the ambient atmosphere. British Patent No. 1 187 783 discloses a method similar to British Patent No. 1 187 784, in which an organotanium compound is sprayed onto a hot glass container instead of an organotin compound. Organotanium compounds can be produced in a manner analogous to organotin compounds by reacting titanium tetrachloride with an organic ester, for example n-butyl acetate. In other words, the resulting solution is sprayed onto the glass in the ambient atmosphere during the container manufacturing process.

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

Methods using reactants in gaseous form (called CVD or chemical vapor deposition) have distinct advantages over spraying methods for coating flat glass, especially when the reactants can be mixed before being applied to the glass. Unfortunately, tin tetrachloride reacts readily with water, so prior preparation is necessary to use tin tetrachloride with water vapor in gaseous form, by individually gassing the glass surface and mixing them in contact with the glass.

British Patent No. 2 044 137A relates to a method for causing a separate laminar flow of each reactant to form on a hot glass substrate by causing a flow in tangential contact with each other in the glass. Titanium tetrachloride can be used as one of the gaseous reactants in place of tin tetrachloride to form a titanium oxide coating. Also, British Patent No. 2 044 137A proposes to supply hydrogen to one of the gas streams to reduce the extreme reaction between tin tetrachloride and water vapor. This can be done by direct addition of hydrogen gas, or by addition of methanol reacting in conditions to produce the desired hydrogen gas.

British Patent No. 2 026 454B discloses that (1) a preheated nitrogen-containing gas, (2) tin tetrachloride contained in the preheated nitrogen, and (3) a continuous stream of air, water vapor and hydrofluoric acid in a float bath. A method is disclosed in which the coating chamber is positioned over a hot float glass ribbon such that it proceeds from a bath and is introduced into the coating chamber and flows along the surface of a glass substrate applied as a turbulence free layer. . British Patent No. 2 026454B describes the concentration of water vapor and tin tetrachloride in a gaseous medium on glass.

European Patent Nos. 0 365 239B1 and 0 376 240B1 disclose a method and apparatus for depositing a tin oxide coating on a high temperature glass ribbon. A first gas flow of tin tetrachloride in the preheated dry air flows along the surface of the hot glass ribbon running down the coating chamber, and a second turbulent flow of hydrofluoric acid and vapor is directed at the plane of the glass and in the direction of the first gas flow. and introduced into the coating chamber perpendicular to the , the mixed flow of the first and second gas streams flows through the coating chamber and onto the glass under turbulent conditions. The apparatus and method may be used to apply a titanium oxide coating using titanium tetrachloride instead of tin tetrachloride.

U.S. Patent 4 590 096 discloses a coating solution comprising a solvent free mixture of organic tin chloride and a reactive organic fluorine compound dissolved in or mixed with organic tin chloride. A method is disclosed wherein the gas stream is introduced into a preheated carrier gas stream containing sufficient water vapor wherein the relative humidity of the gas stream is between about 6% and 100%. The resulting gas stream is passed over the hot glass surface to deposit a fluorinated tin oxide coating on the hot glass. Various organotin compounds can be used, and the possibility of using tin tetrachloride is mentioned. Similarly, various organic fluorine compounds can be used, including oxygen-containing compounds, for example trifluoroacetic acid and ethyltrifluoroacetate. Some fluorine-containing dopants limit solubility in the organotin compounds used, and include, but are not limited to, acetic anhydride, ethyl acetate, hexane, methyl isobutyl ketone, and butyraldehyde ( Butyraldehyde), any solubilizing agent may be used to increase the solubility of the fluorine dopant on the organotin compound. However, this US patent, along with other patent specifications using a chemical vapor deposition method for depositing metal oxides from gaseous metal tetrachloride, uses water vapor as the oxygen source.

US Pat. No. 4 751 149 to Vijaykumar et al. on a heat sensitive photoconductor substrate by chemical vapor deposition at low temperatures (60° C. to 350° C., preferably 100° C. to 200° C.) It is proposed to deposit zinc oxide coatings from oxidants and organozinc compounds which can be, for example, esters and oxygen-containing organic compounds, which are inert carrier gases. Although this US patent is not entirely clear, it is clear that it is not suggested to introduce separate flows of organozinc compound and oxidant into the deposition chamber, and to premix the components together prior to transfer to the coating chamber. .

A CVD method applied to high-temperature plate glass using a premix of an oxygen source and a corresponding metal tetrachloride as a low-cost reactant without premature reaction between the metal tetrachloride and the oxygen source (water) to form an inefficient metal oxide within the coating apparatus. It would be advantageous to provide a method for depositing a tin oxide or titanium oxide coating by A method of depositing a coating at a high rate that allows the required thickness of the coating to be deposited on a moving glass ribbon during the glass manufacturing process is particularly advantageous.

According to the present invention, a tin oxide or titanium oxide coating is placed down on a hot glass substrate using a precursor gas mixture containing an organic oxygen source and a corresponding metal tetrachloride, without the need to contain water vapor and the risk of premature reaction. A chemical vapor deposition method is provided.

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

(a) providing a precursor gas mixture containing an organic oxygen containing compound and a corresponding metal tetrachloride as an oxygen source to form a metal oxide;

(b) maintaining said precursor gas mixture at a temperature below the temperature at which metal tetrachloride reacts to form metal oxide during transfer of said mixture to a coating chamber opening on hot glass;

(c) introducing the precursor gas mixture into the coating chamber.

Here, the mixture is heated to react with oxygen from the organic compounds on the surface of the hot glass substrate to cause deposition of the corresponding metal oxide.

Various oxygen-containing organic compounds that do not require water vapor or gaseous oxygen, including compounds such as alcohols, which are generally considered to be reducing agents rather than oxidizing agents, can be used as the oxygen source. However, preferred organic compounds are in particular carbonyl compounds which are esters, and particularly good results are obtained using esters having an alkyl group comprising beta hydrogen. Alkyl groups comprising beta hydrogens typically contain from 2 to 10 carbon atoms.

It is preferable to use organic compounds containing 2 to 10 carbon atoms, especially esters, because they are inconvenient for use in the CVD method of the present invention due to their tendency to decrease volatility as the molecule increases.

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

The method of the present invention is practiced with respect to the formation of a continuous glass ribbon substrate, for example, during a plate glass manufacturing process. However, the method of the present invention can be used for the coating of other flat glass substrates either online or offline.

The present invention typically involves the preparation of a precursor gas mixture comprising tin tetrachloride or titanium tetrachloride and an organic oxygen-containing compound as a diluent or carrier gas, for example nitrogen, air or helium, which may be included in the gas mixture. Since the pyrolysis of the organic oxygen-containing compound can initiate metal oxide deposition reactions at a high rate, the precursor mixture is maintained at a temperature below the pyrolysis temperature of the organic oxygen compound to prevent the formation of metal oxides and the pre-reaction of the gaseous mixture. It is preferable to be

The gaseous mixture is maintained at a temperature below the temperature at which it reacts to form a metal oxide and adjacent to the glass substrate to be coated which is at a temperature above the reaction temperature (and above the decomposition temperature of the organic oxygen compound in the precursor gas mixture). transported to location.

The precursor gas mixture is then introduced into the vapor space directly above the substrate. Heat from the substrate raises the precursor gas temperature to a temperature above the pyrolysis temperature of the organic oxygen compound. The organic oxygen compounds decompose by reacting with the metal tetrachloride creating a metal dioxide coating on the substrate.

The present invention allows a tin oxide or titanium oxide coating to be deposited on the hot glass at a high deposition rate of 130 Angstroms per second (A) or greater, and in a preferred embodiment greater than 250 A per second.

The deposition rate depends, inter alia, on the use of the organic oxygen-containing compound and the temperature of the glass as well as the concentration of the organic oxygen-containing compound and the metal chloride. For a particular combination of mixtures, the flow rate and optimal concentration (especially the optimal ratio of organic oxide containing compounds to metal tetrachloride) for rapid coating deposition can be determined by simple experimentation. However, it will be appreciated that the use of higher concentrations of reactants and high gas flow rates is likely to result in insufficient conversion of reactants into the coating, so that commercial optimum conditions may differ from those that provide the highest deposition rates.

Preferably, the organic oxygen containing compound will be concentrated to a volume of about 0.5, particularly 1, and up to 5 times the volume of metal chloride. The organic oxygen-containing compound may be used, usually at 30% or more by weight of the metal chloride.

The method of the present invention forms a high proportion of titanium oxide and tin oxide coatings on hot plate glass substrates during the glass manufacturing process. Titanium oxide coatings can be made with a high refractive index (greater than 2.4) which makes it possible to achieve desirable effects, especially when used in combination with other coatings. Tin oxide coatings can be treated, for example, with fluorine, by adding a suitable dopant precursor into the precursor gas mixture to increase the infrared reflectivity and conductivity of the coating, and are used as conductive and low-emissivity coatings in architectural glass and the like.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view, in vertical section, of an apparatus for manufacturing float glass comprising a gas distributor suitably arranged for practicing the method of the present invention;

2 is a cross-sectional view of an article coated in accordance with the present invention;

3 is an enlarged schematic view of a gas distributor beam suitable for use in practicing the present invention;

4 is an enlarged schematic view of an optional gas distributor beam that may be used to practice the present invention;

These and other advantages of the present invention will become apparent to those skilled in the art from the following detailed description of preferred embodiments, when considered in light of the accompanying drawings.

Looking more closely at the drawings, there is shown in Figure 1 a float glass installation used as a means for carrying out the method of the present invention. The float glass apparatus includes a conduit portion 12 through which molten glass 14 is conveyed from a melting furnace (not shown) to a float bath portion 16, and a continuous glass ribbon 18 is formed according to a known float process. . Glass ribbon 18 proceeds from bath section 16 through adjacent annealing furnace 20 and cooling section 22 . The continuous glass ribbon 18 serves as a substrate on which a metal oxide coating is deposited in accordance with the present invention.

The float bath portion 16 includes a bottom portion 24 that includes a molten tin bath 26 having a roof 28 , opposing sidewalls 30 , and endwalls 32 therein. Roof 28, sidewalls 30, and endwalls 32 define an enclosure 34 in which a non-oxidizing atmosphere is maintained to prevent oxidation of the molten tin.

Accordingly, the gas distributor beams 64 , 66 , 68 are positioned within the bath portion 16 . The gas distributor beams 64 and 66 in the bath can be used to apply additional coatings on the substrate prior to applying the tin oxide coating or the titanium oxide coating according to the method of the present invention. Additional coatings may include silicone and silica.

In operation, molten glass 14 flows down a regulating tweel 38 along a duct 36 and flows downstream on the surface of the tin bath 26 in a controlled amount. The molten glass on the tin bath develops laterally under the influence of any mechanical influence and gravity and surface tension and is advanced across the bath to form a ribbon 18 . The ribbon is removed over a lift out roll 40 and conveyed through an annealing furnace 20 and a cooling section 22 on an aligned roll 42 . The coating of the present invention is applied within the float bath portion 16 or, for example, in the space between the float bath and the annealing furnace or along the production line in an annealing furnace.

A suitable non-oxidizing atmosphere, typically nitrogen predominantly nitrogen or a mixture of nitrogen and hydrogen, is maintained within the bath enclosure 34 to prevent oxidation of the tin bath. The atmospheric gas passes through a conduit 44 operatively coupled to a distribution manifold 46 . The non-oxidizing gas is introduced at a rate sufficient to compensate for the normal loss and maintained at a static pressure of about 0.001 to 0.01 higher than the ambient atmospheric pressure to prevent infiltration of the outside atmosphere. Heat is provided into the enclosure by radiant heaters 48 to maintain the desired temperature regime within the tin bath 26 and enclosure 34 . With the cooling section 22 not enclosed and the glass ribbon open to the ambient atmosphere, the atmosphere in the furnace 20 is typically atmospheric air. Ambient air can be directed towards the glass ribbon by a fan 50 in the cooling section. A heater (not shown) may be provided in the annealing furnace such that the temperature of the glass ribbon is gradually decreased according to a predetermined temperature regime as the glass ribbon is moved.

1 illustrates the use of gas distributor beams 64, 66, 68 positioned within a float bath 16 to deposit various coatings on a glass ribbon substrate. A gas distributor beam is one type of reactor that may be used to practice the method of the present invention.

A convenient configuration for a distributor beam suitable for supplying a precursor according to the invention is schematically shown in FIG. 3 . An inverted channel-like frame 70 defined by the spaces of the inner and outer walls 72 , 74 defines an enclosed cavity 76 , 78 . A suitable heat exchange medium is circulated through the enclosed cavities 76 and 78 to maintain the distributor beam at the desired temperature.

The precursor gas mixture is supplied through a cooling fluid supply conduit 80 . A supply conduit 80 extends along the distributor beam and allows gas to pass through drop lines 84 spaced along the supply conduit. The supply conduit 80 allows the transfer chamber 84 in the header 86 to be carried by the frame. The precursor gas, accepted through drop line 82, is discharged from transfer chamber 84 through passage 88 towards the coating chamber defining a vapor space opening on the glass to strike the surface of glass 18 in the direction of the arrow in FIG. flows along

To equalize the flow of precursor material across the splitter beam to ensure that material is emitted against the glass 18 in a laminar uniform flow across the splitter beam, a baffle plate 90 is placed in the transfer chamber ( 84) can be provided. The spent precursor is collected along the side of the distributor beam and removed through an evacuation chamber 92 .

Various types of splitter beams used in chemical vapor deposition are suitable for the present invention and are known in the art.

Any one of the configurations of the splitter beam is schematically illustrated in FIG. 4 . Using such a distributor (described in detail in European Patent EP 0 305 102B), designated with reference number 100, the precursor gas mixture is supplied with a gas cooled by means of a cooling fluid circulated through ducts 102, 103. It is introduced through duct 101 . The gas supply duct 101 opens through an extending hole 104 into the gas flow restrictor 105 .

The gas flow restrictor 105 is of the type disclosed in British Patent Application No. GB 1 507 996 and is mounted vertically adjacent to each other in a longitudinally waving sine wave shape and extending along the length of the distributor. Adjacent wavy metal strips are installed "out of phase" to form a plurality of vertical channels therebetween. This vertical channel has a cross-sectional area that is smaller than the cross-sectional area of the gas supply duct 101 , so that the gas is discharged from the gas flow restrictor 105 at a substantially static pressure along the length of the distributor.

The coating gas is directed to the inlet side 107 of a designated U-shaped guide channel 106 comprising an inlet leg 107 , a coating chamber 108 open on the hot glass substrate 110 to be coated, and an outlet leg 109 . The gas flow restrictor into it is discharged, and the used coating gas is withdrawn from the glass. The rounded edges of the block defining the coating channels uniformly propagate a laminar flow of coating parallel to the glass surface across the glass surface to be coated.

The following examples (where the gas capacity is expressed under standard conditions, i.e. one atmospheric pressure and ambient temperature without being brought to another state) are presented to illustrate the present invention and should not be construed as limitations of the present invention.

Examples 1 to 5

In a series of embodiments, a bidirectional coating reactor of the type shown in FIG. 3 may be used within the apparatus to deposit a titanium oxide coating.

In Examples 1-3, the glass was heated in a transfer hearth to meet the coating reaction conditions of the float glass process to test the method of the present invention. The furnace used inline rollers to transport the glass substrate through the heating zone prior to carrying out the method of the present invention. In Example 1, the glass substrate was initially a float glass provided with a silica coating. Silica coatings were deposited on float glass via a known chemical vapor deposition method using a precursor of monosilane in an oxygen containing atmosphere. Silica deposition is not included as part of this invention.

A titanium oxide coating according to the present invention was deposited on a silica coated substrate. The substrate temperature was 630 °C (1170 °F) and the substrate line speed was 8 m (300 in) per minute.

To deposit titanium oxide, the precursor gas mixture included titanium tetrachloride, ethyl acetate, oxygen, and helium. Helium was included in the precursor mixture as a carrier for the reactants. The precursor mixture was prepared by simultaneously introducing four gas streams through a manifold system. A static mixer was used in the line to ensure a homogeneous precursor mixture. The volume percent composition of the 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 manifold as shown in the attached Table 1.

The temperature of the precursor mixture was maintained above 150 °C (350 °F) to prevent the addition reaction of titanium tetrachloride and ethyl acetate. In addition, the precursor temperature was also maintained below the thermal decomposition temperature range of ethyl acetate from 510°C to 610°C (950°F to 1130°F) to prevent a pre-reaction of the mixture.

The precursor mixture was introduced into the reactor directly above the moving substrate. The temperature in the precursor tower was 120 °C (250 °F). The temperature at the reactor side was 175°C (350°F). The higher substrate temperature initiated thermal decomposition of ethyl acetate which resulted in the deposition of titanium oxide.

The resulting coated glass was cooled by air and coating decomposition. It has been found that titanium oxide contains 2.5 to 3.5 atomic percent carbon. The thickness of the titanium oxide coating was measured 490 Å, and the thickness and growth rate (150 Å per second) are shown in Table 1. As for the optical properties of the result, the observed illuminant C transmittance (observed at an angle of 10°) was 62.3% and the observed illuminant C reflectivity was 35.6%. The extinction coefficient was 0.008 at 550 nm, and the refractive index of the titanium oxide coating was 2.44.

In Example 2, ethyl formate was used as the organic oxygen source, and in Example 3, isopropanol was used as the organic oxygen source and uncoated glass (oxidation of Examples 1 and 2). The coating procedure set in Example 1 was repeated in Examples 2 and 3, except that (instead of silicon coated glass) was used as the substrate. The gas flow rates used in the case of Example 2 and the thickness and growth rate of the titanium oxide coating are shown in Table 1. In Example 3, isopropanol burned in the reactor leaves only titanium oxide particulates on the glass, and the corresponding deposition rate is 0 angstroms per second.

The procedure of Examples 4 and 5 is the same as that used in the previous examples except that the substrate is static rather than dynamic (reactor temperature and substrate are the same as in Example 1). A static specimen is placed under the reactor for 10 seconds. Under static conditions, the residence time of the substrate under the reactor is increased over dynamic conditions by five factors.

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

Example 6

The float glass process was used to make continuous glass ribbons with a thickness of 3 mm (0.125 in) on a line at a speed of 11 m (434 in) per second. The glass temperature at the preferred point in the float bath of the titanium oxide coating was 615° C. (1140° F) using the same coating reactor as shown in FIG. 3 . The temperature in the precursor tower was 205 °C (400 °F) and the temperature at the reactor side was 260 °C (500 °F). Prior to carrying out the method of the present invention, a silica coating was deposited on the glass substrate in the float bath to a thickness of about 339 angstroms. A chemical vapor deposition method as described above in Example 1 was used to deposit the silica coating. Silica deposition is not included in the present invention.

The precursor gas mixture was enhanced to include titanium tetrachloride and ethyl acetate in the helium carrier gas. Oxygen was not used in the precursor as in the above examples the coating reaction was indicated to be insensitive to oxygen concentration. The precursor mixture was prepared by simultaneously introducing the three components through a manifold system. The volume percent composition of the precursor mixture was 0.6% titanium tetrachloride, 1/8% ethyl acetate, and 97.5% helium. The flow rates of the components were helium 480.0 l/m, titanium tetrachloride 3.0 l/m, ethyl acetate 9.2 l/m. The total flow rate of the precursor mixture was 492.2 l/m.

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

Example 7

The same procedure as in Example 6 was used in this example. The substrate includes a silicon and silica coating over a glass substrate. The coating was deposited by known chemical vapor deposition in a float bath. The silicon coating was deposited by CVD from monosilane with a non-oxidizing carrier gas. The silica coating was deposited on the silicone coating through the same procedure as in Example 1.

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

The coated result 52 is shown in FIG. 2 . Glass substrate 54 is depicted as a stack of composite coatings 56 . The coating includes a silicon layer 58 , a silica layer 60 , and a titanium oxide coating 62 on the resulting product. The resulting titanium oxide coating had a thickness of 836 Angstroms. The optical properties of the resulting coating stack were an observed C light source transmittance of 13.1% and an observed C light source reflectance of 82.5%. The growth rate of the titanium oxide coating was 378 Å per second.

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Examples 8 to 13

In a series of examples, a static coater is installed in the apparatus to apply a tin oxide coating on a float glass substrate carrying a color that inhibits the resulting silicon oxide layer as disclosed in European Patent EP 0 275 662B. was used

The float glass to be coated was supported on a nickel block in a reactor vessel, which was heated by an electric heating element to provide the glass with a temperature of 585° C. (1085° F.) as follows. A graphite plate approximately 10 mm (0.4 in) was mounted parallel to the glass to provide a 10 mm (0.4 in) deep gas flow path between the plate and the glass surface supporting the silicon oxide layer.

A precursor gas mixture containing an organic oxygen source and tin tetrachloride in air with a small proportion of additional nitrogen as carrier gas is passed through a gas line maintained at a temperature of 225 °C ± 15 °C (435 °F ± 25 °F). A fish tail nozzle opening was provided on the gas flow path over the hot glass in a direction generally parallel to the glass surface. Total carrier gas flow is 13 m³/hr. The actual flow rate of tin tetrachloride and the flow rate of the organic compound used are shown in the attached Table 2. In Examples 9-11, a small amount of 40% hydrogen fluoride was added to the precursor gas mixture to fluorine the resulting tin oxide coating as shown in the table.

A gas stream containing reactant gases was applied for approximately 8 seconds, and the coating apparatus and coated glass were cooled under an air flow of 225°C (345°F). When dismantling the coating apparatus, the conveying gas lines, nozzles and plates defining the gas flow passages on the glass are installed free from the deposition unit in each case indicating undesirable elements. In each case, the glass has a tin oxide coating applied over the silicon oxide, and the thickness of the coating varies with the distance from the fish tail nozzle. The maximum thickness and corresponding growth rate of each precursor gas mixture used are shown in Table 2. Table 2 shows the results of measurements of emissivity, resistivity and haze of samples prepared using hydrogen fluoride together with a fluorine dopant (Examples 9 to 11).

A series of examples show that the organic oxygen source is premixed comprising tin tetrachloride to deposit a tin oxide coating without undesirable pre-reactions adversely affecting the coating process, for example by deposition of tin oxide in a gas supply duct. It is shown that it can be used as part of a precursor gas mixture. Also, a source of dopant, such as hydrogen fluoride, can be incorporated into the gaseous premixture to reduce the emissivity and resistivity of the coating in a continuous state to avoid detrimental prereactions.

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Example 14

In this example, a coating dispenser as schematically shown in FIG. 4 was used in the float bath to apply the tin oxide coating by the method according to the invention. The ribbon speed was approximately 233 inches per minute (350 minutes per hour) and the glass thickness was 1.2 mm (0.05 inches). The glass temperature was approximately 630°C (1170°F). The temperature of the gas supply duct 101 serving as the first gas mixing chamber was maintained at 150°C (300°F), and the static waffle-type gas distributor 105 was approximately 340°C (645°F). it was The tin tetrachloride and butyl acetate vapors were conveyed through separate heating conduits to gas supply duct 101 by bubbling nitrogen through the liquid maintained at 80° C. (175° F.) in the bubble. The vapors mixing in the first chamber pass through a waffle-type pack gas distributor and then under laminar flow conditions through a U-shaped guide channel 106 comprising a coating chamber 108 open on a hot glass ribbon.

The flow rate to be used was sufficient to obtain a tin tetrachloride:butyl acetate molecular ratio between 1:1 and 1:5. The experiment was carried out for 5 hours. Upon removal of the coater, the cooled surface and associated conduits were found to be more than 90% deposits, so that the tin tetrachloride and butyl acetate used to create the tin dioxide coating on the glass could be premixed with each other without substantial pre-reaction. can A thin tin oxide coating was obtained on the glass ribbon.

It will be understood that various changes or modifications may be made from the detailed description of the invention set forth in the foregoing embodiments without departing from the spirit and scope of the appended claims. In the detailed description, the present invention describes a continuous chemical vapor deposition method for disposing tin oxide and titanium oxide coatings on glass substrates at high deposition rates through the use of a corresponding metal tetrachloride and an organic compound used as an oxygen source in a precursor gas mixture implemented. am.

Metal tetrachloride is the basis of each metal because of its availability and raw material cost.

When depositing titanium oxide coatings from titanium tetrachloride to form metal oxides with optimum deposition rates, it is preferable to use esters, especially organic oxygen-containing compounds in which the group derived from the alcohol is an ester in the alkyl group with β-hydrogen. found out that In addition, the decomposition temperature of the ester should not be higher than the reaction temperature of the coating precursor gas mixture at the desired point of application. An ester used in a precursor gas mixture with β-hydrogen and an appropriate decomposition temperature will deposit the coating at a high deposition rate. Preferred ester groups used in practicing the present invention include the group consisting of ethyl formate, ethyl acetate, ethyl propionate, isopryl formate, isopryl acetate, n-butyl acetate, and t-butyl acetate.

In general, esters decompose in a continuous fashion over a given temperature range. In the present invention, the thermal decomposition temperature of the ester is defined as the temperature at which the monomolecular decomposition rate constant of the ester is 0.01/sec. The monomolecular decomposition rate constants of common esters such as ethyl acetate and t-butyl acetate are known and can be found in chemical literature and the like. For ethyl acetate and t-butyl acetate, the pyrolysis temperatures using these limits are 500°C and 344°C (935°F and 650°F), respectively. Those skilled in the art will understand that the choice of ester and the specific deposition temperature used will determine the optimum coating growth rate. Reaction temperatures that are within the decomposition range of the selected ester but below the defined pyrolysis temperature will result in lower coating growth rates.

According to the present invention, the alkyl group of the ester used in the coating precursor gas mixture may be a carbon compound having a range from 2 to 10 carbon atoms. The lower limit of the range is indicated by the β hydrogen required for the alkyl group. The upper limit avoids flammable and volatile effluents that rise when the alkyl group contains more than 10 carbon atoms.

In practicing the method of the present invention, a manifold may be used to connect and regulate the respective gas flows to formulate the coating precursor gas mixture. A common transfer line may be used to transfer the precursor gas mixture from the manifold to the gas beam distributor. An in-line static mixer can be used in the transfer line to ensure a homogeneous gas mixture. In addition, the baffles in the gas distributor beam shown in FIG. 3 and the gas flow restrictor described with reference to FIG. 4 can provide additional mixing of the precursor gas in the reactor stage.

In many embodiments, oxygen was included in the coating precursor gas mixture. However, the deposition rate of the metal oxide coating was not sensitive to oxygen concentration, and no oxygen gas was used in Examples 6 or 7, which showed that the inclusion of oxygen was unnecessary.

The concentration of the reactive components of the coating precursor gas mixture may be selected to obtain an optimal coating growth rate. The concentration of metal tetrachloride is generally between 0.1 and 5.0 volume percent in the precursor gas mixture. The concentration of metal tetrachloride is based on the amount of metal required to provide the desired coating thickness within the available residence time. Thus, the metal tetrachloride concentration is controlled according to various processes, such as the line speed of the ribbon in the float glass process.

The concentration of the organic oxygen compound in the coating precursor gas mixture is generally 1 to 5 times the metal tetrachloride concentration and is selected within a range based on the deposition temperature. When using an ester, a higher ester concentration is required to react with the metal tetrachloride as the lower deposition temperature results in a lower rate of ester decomposition. 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 or below the optimum range will produce a metal oxide coating with a lower coating growth rate.

The temperature of the precursor gas mixture is important to control the reaction, especially to avoid the formation of undesirable pre-reactions or adducts that lead to the formation of non-volatile products within the precursor line. In one preferred embodiment, particularly when applying an ester, the temperature is maintained above 150°C (300°F) in the precursor gas line. In addition, the precursor gas mixture is kept well below the pyrolysis temperature of the organic oxygen compound to prevent a pre-reaction of the mixture.

The method of the present invention utilizes heat from the substrate to initiate the coating reaction. In an online state, such as in the float glass process, the substrate is formed at very high temperatures. Therefore, the method of the present invention is a point in the float glass process at which the substrate temperature is lowered but above the temperature at which the coating is formed (preferably after the glass ribbon has substantially finished drawing, i.e., 750°C (1380°F)). can be applied in Off-line application of the present invention requires heating the substrate to a temperature above the decomposition temperature of the ester.

In practicing the method of the present invention in a float glass process, a preferred point of application is within the float bath. The temperature range for the coating at the point of application is about 590°C to 715°C (1100°F to 1320°F). Temperature is an important working factor as it affects the concentration of organic compounds used in the precursor gas mixture. The temperature of the substrate in the float bath is relatively stable, so there is little change at the point of application. In Examples 6 and 7 using ethyl ester, the preferred substrate temperature range is 590°C to 680°C (1100°F to 1250°F).

Heat from the substrate raises the temperature of the precursor gas mixture above the temperature required to form the coating (and above the pyrolysis temperature of the ester when the ester is used in an organic compound). The metal deposition reaction can be initiated by decomposition of organic oxygen compounds. When titanium tetrachloride is used in combination with an ester having an alkyl group having β-hydrogen, a titanium oxide coating is formed on the substrate with a decomposition rate ten times higher than that of known coating methods. In an online application with a float glass ribbon process, the ribbon passes under the gas distributor beam at a relatively rapid rate. The metal oxide coating is deposited on the float glass ribbon as the ribbon passes under the coater.

The present inventors propose the following theory which takes into account the chemical reactions that may occur when using esters having an alkyl group with β hydrogen. However, the inventors do not wish that the present invention is limited to these descriptions, but rather help to understand the results of the present invention.

We propose ester cleavage, a broken carbon-hydrogen bond on one β-hydrogen, and a hydrogen transported to the carbonyl group that removes the alkene to form the carboxylic acid. The hydrolysis reaction occurs simultaneously between the metal tetrachloride and the carboxylic acid forming a metal oxide coating on the substrate.

Generally, the product produced according to the present invention comprises a substrate having a titanium oxide or tin oxide coating. The coating may be applied directly to the substrate or as a plurality of coating layers on the substrate. The deposition rate of the metal oxide coating is affected by the deposition rate of the organic oxygen compound. A constant reaction temperature of the various organic oxygen compounds will give different coating growth rates due to the difference from the decomposition temperature. Therefore, the desired metal oxide coating growth rate for a given system is selected by matching the specific organic oxygen compound to the precursor gas mixture temperature and the substrate temperature at the point of application.

The deposition rate of the titanium oxide coating of the present invention can be ten times greater than that of known deposition methods. The process of the present invention allows for deposition rates of 130 Angstroms or more, with some deposition rates preferably measuring 300 Angstroms or more. A higher deposition rate of titanium oxide results in a coating having a refractive index of 2.4 or greater.

In addition to being able to obtain high coating rates, an additional advantage of the present invention is the use of inexpensive metal precursor compounds, particularly when the precursor gas mixture is placed over the substrate under good laminar flow conditions (of metal tetrachloride). High conversion efficiency can be obtained.

In the present invention, especially when esters are used, the resulting oxide coating contains little carbon remaining from the decomposition of organic oxygen compounds. Carbon is an undesirable by-product of the coating reaction because high levels of carbon in the deposition coating create absorption problems in the coating. A consideration in the use of organic oxygen compounds in the coating precursor gas mixture is that decomposition brings the carbon to levels that adversely affect the absorption properties of the final glass. The carbon content in the coating resulting from the process of the present invention is shown to be less than the measured 4 atomic percent carbon. This low level of carbon will not affect the absorption properties of the coating.

The forms of the invention shown and described herein may be taken identically to the illustrated embodiments, and various changes in processes as well as various changes in shape, size and arrangement of parts may be reconfigured without departing from the spirit of the invention. You have to understand that you can.