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

Method for depositing tin oxide and titanium dioxide coating on flat glass and obtained coated glass

The present invention relates to a method for depositing titanium dioxide and tin oxide on a flat glass substrate, and the coated glass obtained thereby. More specifically, the present invention relates to a chemical vapor deposition method for preparing titanium dioxide and tin oxide coatings on flat glass using a coating precursor gas mixture including corresponding metal tetrachlorides and organic oxidants.

Titanium dioxide and tin oxide coatings have been suggested for glass containers, such as glass bottles, to improve the mechanical strength of the container. It has been suggested to use both titanium dioxide and tin oxide coatings on flat glass to improve the properties of architectural glass; titanium dioxide coatings deposited under vacuum (reactive sputtering) are used as spray coatings for multi-layer infrared reflective coatings. The tin oxide coating is not only used as a coating for multi-layer sprayed coatings, but also can be pyrolytically deposited with dopants as infrared reflective and/or conductive coatings.

GB Patent Specification 1 115 342 describes a method for preparing glass containers with good inherent strength and good abrasion resistance by spraying glass containers, where tetrachloride is used when the glass container is still hot from the preparation process A solution of tin dispersed in an organic liquid, preferably isopropanol, is sprayed into the glass container. A small amount of titanium chloride can be added as a modifier. The liquid solution is added to the sprayer (which can be a pressure sprayer type) located on either side of the channel above the conveying device of the hot glass bottle to generate a "liquid reagent mist", so that a liquid is formed on all outer surfaces of the glass bottle Layer, and the liquid layer reacts on all outer surfaces of the glass bottle to form a tin oxide layer.

GB Patent Specification 1 187 784 describes an improved method of the method described in GB Patent Specification 1 115 342, which is obviously more suitable for introduction into the automatic production process of glass products without disturbing the normal operation of such a process And no additional monitoring device is required. The manual recommends the use of liquid solutions of tin organic compounds to treat glass containers at high temperatures ("The tin compound has the property that when heat is applied, it decomposes into two materials, one is tin with a high decomposition temperature). An organic compound that reacts with the glass surface to obtain a dispersion coating of tin oxide on the glass surface, and the other is a volatile compound of tin in order to generate a large amount of vapor of the compound and subject the container to heat treatment, so that at least the container A reaction occurs between the glass on the surface and the tin compound"). The materials used to treat glass containers can be organic substances containing tin tetrachloride and moderately reactive carbonyl group-containing organic substances such as ethanol, n-propanol, isopropanol, n-butanol and isobutanol with acetic acid, propionic acid and butyric acid. Ester reaction is provided. After the hot containers leave the brittle machine and before they enter the annealing furnace, the solution obtained can be sprayed onto the hot containers in the form of a fine mist in the presence of the surrounding atmosphere. GB Patent Specification 1 187 783 describes a similar to 1 187 The method described in 784, in which an organic compound of titanium instead of an organic compound of tin is sprayed into a hot glass container. In a manner similar to the organic compound of tin, an organic titanium compound is prepared by reacting titanium tetrachloride with an organic ester such as n-butyl acetate. The obtained solution is still sprayed onto the production line of the container in the surrounding atmosphere.

It has also been proposed to use titanium tetrachloride (as a liquid jet or recently applied in gas form) to apply a tin oxide coating to hot flat glass to form a conductive, infrared reflective coating on the hot glass surface; Used to hydrolyze tin tetrachloride and as an oxygen source to form tin oxide.

The method including the use of reagents in gas form (also known as CVD or chemical vapor deposition method) has certain advantages in the spraying process of coating flat glass, especially the reagents can be premixed before coating the glass. Unfortunately, tin tetrachloride is prone to react with water, so previous proposals to use tin tetrachloride and water vapor that exist in gas form generally include separately supplying these gases on the glass surface and mixing them when in contact with the glass.

GB Patent Specification 2 044 137A relates to a method in which separate laminar flows of each reagent are formed, and then these laminar flows are introduced together to bring them into reverse tangential contact over the glass. In order to form a titanium dioxide coating, titanium tetrachloride can replace tin tetrachloride as one of the gas reagents. The patent also proposes to supply hydrogen in one of the gas streams to weaken the violent reaction between tin tetrachloride and water vapor. This can also be done by adding gaseous hydrogen directly or by adding methanol, which is said to react in situ to obtain the desired gaseous hydrogen.

GB Patent Specification 2 026 454B describes a method in which when the glass ribbon is pushed forward from the float bath, the coating chamber is arranged above the hot float glass ribbon, and the coating Add (1) preheated nitrogen carrier gas, (2) tin tetrachloride entrained in the preheated nitrogen, and (3) a continuous flow of air, water vapor and hydrofluoric acid, so that they follow the coated glass The surface of the substrate flows as a substantially turbulence-free coating. The patent specifies the concentration of water vapor and tin tetrachloride in the gaseous medium above the glass.

European patent specifications 0 365 239B1 and 0 376 240B1 describe a method and equipment for depositing tin oxide coatings on hot glass ribbons. The first airflow of tin tetrachloride in the preheated dry air flows along the surface of the hot glass ribbon advancing under the coating chamber, and the second turbulent flow of hydrofluoric acid and steam added to the coating chamber is in line with the glass plane and the first The flow direction of the airflow is introduced at a right angle, and under turbulent flow conditions, the mixed first and second airflows are guided through the coating chamber above the glass. The method and equipment can also be used to use titanium tetrachloride instead of tin tetrachloride to coat titanium dioxide coatings.

US Patent 4 590 096 describes a method in which a coating solution is added to a preheated carrier gas flow, wherein the coating solution includes a substantially solvent-free organotin chloride and soluble or can be dissolved in or with chlorine A mixture of reactive organic fluorine compounds mixed with organic tin, and the carrier gas stream includes sufficient water vapor with a relative humidity of about 6% to 100% at 18°C. The resulting air flow passes over the hot glass surface and deposits a fluorine-doped tin oxide coating on the hot glass. Various organotin compounds can be used, and the possibility of using tin tetrachloride is mentioned. Similarly, a wide variety of organic fluorine compounds can be used, including oxygen-containing compounds such as trifluoroacetic acid and ethyl trifluoroacetate. Some fluorine-containing dopants have limited solubility in the organotin compounds used, and optional solubilizers can be used to increase the solubility of the fluorine dopants in the organotin compounds; acetic anhydride, ethyl acetate, hexane, Methyl isobutyl ketone and butyraldehyde are listed as non-limiting examples of solubilizers that can be used. However, this US patent and other patents that use chemical vapor deposition methods to deposit metal oxides from gaseous metal tetrachlorides both use water vapor as the oxygen source.

US Patent 4 751 149 to Vijaykumar et al. relates to a chemical vapor deposition method at low temperature (60 to 350°C, preferably 100 to 200°C) to deposit a zinc oxide coating on a heat-sensitive photoconductor substrate, and it is recommended to use organic zinc The zinc oxide coating is deposited with a compound and an oxidant and an inert carrier gas, where the oxidant can be an organic compound containing oxygen such as an ester. Although the patent is not very clear, it clearly proposes to add separate streams of organozinc compound and oxidant in the deposition chamber, and there is certainly no proposal here to pre-mix these components before they are delivered to the coating chamber.

It is advantageous to provide a method for depositing tin oxide and titanium dioxide coatings on hot flat glass by CVD method using corresponding metal tetrachloride as a premix of low-cost reagent and oxygen source, wherein the metal tetrachloride and oxygen source There is no early reaction leading to the formation of metal oxides in the coating equipment, and this reaction causes subsequent problems and low efficiency. It is particularly advantageous if the method allows the coating to be deposited at a high speed, then it is possible to deposit the desired thickness of the coating on the moving glass ribbon during the glass production process.

According to the present invention, there is provided a chemical vapor deposition method for depositing tin oxide or titanium dioxide coatings on a hot glass substrate using a precursor gas mixture containing corresponding metal tetrachloride and an organic source of oxygen. The method does not need to include water vapor. And there is no subsequent risk of early reaction.

The present invention provides a method for depositing tin oxide and titanium dioxide coatings on hot flat glass, which comprises the steps of: (a) preparing a metal tetrachloride containing the corresponding metal and organic oxygen as an oxygen source for forming metal oxides. (B) maintaining the precursor gas mixture at a temperature lower than the temperature at which the metal tetrachloride reacts to form a metal oxide, while delivering the mixture to the coating leading to the hot glass In the coating chamber, (c) the precursor gas mixture is added to the coating chamber, thereby heating the mixture to combine oxygen from the organic compound to deposit the corresponding metal oxide on the hot glass surface.

Surprisingly, a wide variety of organic compounds can be used as oxygen sources without the presence of water vapor or gaseous oxygen, including compounds that are generally considered reducing agents rather than oxidizing agents, such as alcohols. However, the preferred organic compounds are carbonyl compounds, especially esters; particularly good results have been obtained using esters with β-hydrogen alkyl groups. Alkyl groups with beta hydrogens will generally contain 2 to 10 carbon atoms.

It is preferable to use organic compounds containing 2 to 10 carbon atoms, especially esters, because large molecules tend to be difficult to volatilize and therefore inconvenient to use in the CVD method of the present invention.

Particularly preferred esters used in the present invention include ethyl formate, ethyl acetate, ethyl propionate, isopropyl formate, isopropyl acetate, n-butyl acetate, and tert-butyl acetate.

The method of the present invention is usually implemented in conjunction with the formation of a continuous glass ribbon substrate, for example in a float glass production process. However, the method of the present invention can be used in coating other flat glass on-line or off-line.

The present invention includes the preparation of a precursor gas mixture including tin tetrachloride or titanium tetrachloride and an organic compound containing oxygen; the gas mixture generally also includes a carrier gas or a diluent such as nitrogen, air or helium gas. Because the thermal decomposition of oxygen-containing organic compounds can stimulate the deposition reaction of metal oxides at a high rate, it is desirable that the precursor mixture is maintained at a temperature lower than the thermal decomposition temperature of the organic oxygen compound to prevent the gas mixture from forming pre-reactions. Metal oxide.

Keep the gas mixture at a temperature lower than the temperature at which it reacts to form metal oxides, and transport it to a position close to the flat glass substrate to be coated, the substrate temperature being higher than the reaction temperature (and higher than The decomposition temperature of the organic oxygen compound in the precursor gas mixture).

After that, the precursor gas mixture is added to the evaporation space directly above the substrate. The heat from the matrix raises the temperature of the precursor gas to a temperature higher than the thermal decomposition temperature of the organic oxygen compound. Then, the organic oxygen compound decomposes and simultaneously reacts with the metal tetrachloride to produce a metal dioxide coating on the substrate.

The present invention allows the deposition of tin oxide and titanium dioxide coatings on hot glass at high deposition rates, for example in excess of 130 angstroms/sec, and in preferred embodiments, for example, deposition rates in excess of 250 angstroms/sec.

The deposition rate depends on the specific organic oxygen-containing compound used, the concentration of both the organic oxygen compound and the metal chloride, and the temperature of the glass. For any particular combination of compounds, the optimal concentration of rapid coating deposition (especially the optimal ratio of organic oxygen compound and metal tetrachloride) and the flow rate can be determined by simple experiments. However, it should be realized that the higher reagent concentration and high gas flow rate in the test may result in low efficiency in the entire reagent conversion process, so that the best commercially available conditions can be different from the conditions that provide the highest deposition rate. .

Preferably, the concentration (volume) of the organic oxygen compound is about 0.5 times, especially 1 to 5 times, the concentration (volume) of the metal chloride. Generally, the amount of the organic oxygen compound used is at least 30% by weight based on the weight of the metal chloride.

The method of the present invention allows in-line deposition of titanium dioxide and tin oxide coatings on a hot flat glass substrate at a high speed in the production process of flat glass. Titanium dioxide coatings with high reflectivity (at least 2.4) can be prepared to obtain the desired optical effect, especially when used in combination with other coatings. Tin oxide coatings can be doped by adding suitable dopant precursors to the precursor gas mixture, such as fluorine, which can improve the conductivity and infrared reflectivity of the coatings, and therefore increase their use in architectural glass and Practicality as conductive coating and/or low emissivity coating in other applications.

For those skilled in the art, the above and other advantages of the present invention will be more apparent with reference to the accompanying drawings and the detailed description of the preferred embodiments below.

Figure 1 is a schematic diagram of a longitudinal section of the equipment used in the float glass process, which includes a gas distributor suitably arranged so as to be able to implement the method of the present invention.

Figure 2 is a cross-sectional view of an article coated in accordance with the present invention; and Figure 3 is a schematic enlarged side view of a gas distributor beam suitable for use in the practice of the present invention.

Figure 4 is a schematic enlarged side view of another gas distributor beam that can be used in the practice of the present invention.

Now, it will be described in more detail with reference to the accompanying drawings. In FIG. 1, 10 generally shows a complete set of float glass equipment used as a device for implementing the method of the present invention. More specifically, the float glass equipment includes a channel area 12 along which molten glass 14 is transported from a furnace (not shown) to a float bath area 16, in which the float glass is in accordance with the well-known float bath area. The method process forms a continuous glass ribbon 18. The glass ribbon 18 advances from the float bath area 16 through the adjacent annealing furnace 20 and the cooling zone 22. The continuous glass ribbon 18 serves as a substrate on which a metal oxide coating is deposited according to the method of the present invention.

The float bath area 16 includes a bottom area 24 in which the molten tin bath 26 is contained, a top cover 28, opposing side walls 30 and end walls 32. The top cover 28, the side wall 30 and the end wall 32 together define a cavity 34 in which a non-oxidizing atmosphere is maintained to prevent oxidation of the molten tin.

In addition, the beams 64, 66, and 68 of the gas distributor are arranged in the float tank area 16. The gas distributor beams 64 and 66 in the float bath area can be used to apply an additional coating on the substrate before applying the tin oxide or titanium dioxide coating according to the method of the present invention. This additional coating includes silicon or silicon dioxide.

In operation, the molten glass 14 flows along the channel 36 under the regulating gate 38 and flows down to the surface of the tin bath 26 at a controlled flow rate. In the tin bath, the molten glass expands laterally under the influence of gravity and surface tension and under some mechanical influence, and advances forward through the bath to form a glass ribbon 18. The glass ribbon moves above the lift roller 40 and then is transported through the annealing furnace 20 and the cooling belt 22 on the guide roller 42. The coating method of the present invention can be used in the float bath area 16, or further along the production line, for example in the gap between the float bath and the annealing furnace, or in the annealing furnace.

A suitable non-oxidizing atmosphere is maintained in the cavity 34 of the tank, which is generally nitrogen or a mixture of nitrogen and hydrogen (mainly nitrogen) to prevent the tin bath from being oxidized. The shielding gas is allowed to pass through a conduit 44 that is operatively matched with the shunt pipe 46. The non-oxidizing gas is added at a rate sufficient to compensate for normal losses and maintain a slightly positive pressure (about 0.001 to about 0.01 atmospheres above the surrounding atmospheric pressure) to prevent infiltration of the outside atmosphere. The radiant heater 48 in the cavity provides heat for maintaining a desired temperature range in the tin bath 26 and the cavity 34. The gas in the annealing furnace 20 is generally air, and the cooling zone 22 is not enclosed, and the glass ribbon is in communication with the surrounding atmosphere. In the cooling zone, the fan 50 blows ambient air toward the glass ribbon. A heater (not shown) may also be arranged in the annealing furnace so as to gradually lower the temperature of the glass ribbon according to a predetermined temperature range when the glass ribbon is conveyed through the annealing furnace.

FIG. 1 shows the use of gas distributor beams 64, 66, and 68 arranged in the float bath 16 to deposit various coatings on a glass ribbon substrate. The glass distributor beam is a form of reactor that can be used in the implementation of the method of the present invention.

The advantageous structure of the distributor beam suitable for supplying the precursor material of the present invention is schematically shown in Fig. 3 in general terms. The inverted generally channel-shaped frame 70 formed by the spaced-apart inner and outer walls 72 and 74 defines closed cavities 76 and 78. A suitable heat exchange medium circulates through the enclosed cavities 76, 78 in order to maintain the distributor beam at the desired temperature.

The precursor gas mixture is supplied through the liquid cooling supply conduit 80. The supply duct 80 extends along the distributor beam and allows the gas to pass through downcomers 82 spaced along the supply duct. The supply duct 80 leads to the delivery chamber 84 in the heater 86 supported by the frame. The precursor gases allowed to pass through 82 are discharged from the delivery chamber 84 through the passage 88 into the coating chamber defining the vapor space communicating with the glass, where they flow along the surface of the glass 18 in the direction of the arrow in FIG. 3.

The transfer chamber 84 may be equipped with a baffle 90 for adjusting the flow rate of the precursor material passing through the distributor beam, so as to ensure that the material passes through the distributor beam in a smooth, layered, and uniform fluid to the glass 18 discharge. The spent precursor material is collected and removed by an exhaust chamber 92 arranged along the side of the distributor beam.

The various distributor beam forms used in the chemical vapor deposition method are suitable for the method of the present invention and are known in the prior art.

Fig. 4 schematically shows such a distributor beam structure. When using this distributor (generally denoted by 100, which is described in more detail in European Patent EP0 305 102B), the precursor gas mixture is added through the gas supply conduit 101, and the mixture is passed through the conduit 102 and the gas supply conduit 101 in the gas supply conduit 101. The 103 circulating cooling liquid is cooled. The gas supply conduit 101 communicates with the gas flow throttle valve 105 through the elongated aperture 104.

The gas flow throttle valve 105 is the kind described in great detail in the UK patent specification GB1 507996, which includes a number of metal strips that are vertically curled in the form of a sine wave and extend along the length of the distributor. . The adjacent crimped metal strips are arranged out of phase so as to define a plurality of vertical channels therebetween. These vertical channels have a smaller cross-sectional area equivalent to the cross-sectional area of the gas supply conduit 101, so that gas is released from the gas flow throttle valve 105 at a substantially stable pressure along the length of the distributor.

The coating gas released from the gas flow throttle enters the inlet side 107 of the substantially U-shaped guide channel (generally referred to as 106), wherein the guide channel 106 includes an inlet pipe 107 leading to the hot glass substrate to be coated The coating chamber 108 and the exhaust pipe 109 for exhausting the used coating gas from the glass. The rounded corners of the blocks that define the coating pipe allow the paint to flow uniformly and in layers across the glass surface to be coated parallel to the glass surface.

In order to further illustrate and disclose the present invention, the following examples are given (wherein, unless otherwise specified, the gas volume is the volume under standard conditions, that is, 1 atmosphere and ambient temperature), but it should not be considered as a limitation to the present invention.

Examples 1 to 5 In this series of examples, a bidirectional coating reactor of the type shown in Figure 3 was used in the laboratory to deposit titanium dioxide coatings.

In Examples 1, 2 and 3, in order to test the present invention, the glass was heated in a conveyor heating furnace to simulate the coating reaction conditions in the plate glass process. Before implementing the method of the present invention, guide rollers are used to transport the glass substrate through the heating zone in the heating furnace on-line. In Example 1, the glass substrate was float glass that had already had a silica coating at the beginning. The silica coating is deposited on float glass using a monosilane precursor in an oxygen-rich atmosphere according to a known chemical vapor deposition method. The deposition of silica does not form part of the invention.

According to the invention, a titanium dioxide coating is deposited on a silicon dioxide-coated substrate. The temperature of the substrate is 1170°F/630°C, and the linear velocity of the substrate is 300 inches or 8 meters per minute.

To deposit titanium dioxide, a precursor gas mixture containing titanium tetrachloride, ethyl acetate, oxygen and helium was developed. The precursor mixture includes helium as a carrier for the reagent. The precursor mixture is prepared by simultaneously adding all the four gas streams through a multi-pipe system. Use an in-line static mixer to ensure that a homogeneous precursor mixture is obtained. The volume percentages of the precursor mixture components are 0.7% titanium tetrachloride, 17.2% ethyl acetate, 7.2% oxygen and 74.9% helium. The flow rates of these components in the manifold are listed in the attached table 1 in.

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

The precursor mixture is added to the reactor directly above the moving substrate. The temperature of the precursor injection tower is 250°F/120°C. The temperature outside the reactor is 350°F/175°C. The higher substrate temperature stimulates the thermal decomposition reaction of ethyl acetate, and this reaction leads to the deposition of titanium dioxide.

The obtained coated glass was cooled in air and the coating was analyzed. It can be found that the coating is titanium dioxide with a carbon content of 2.5-3.5 atomic %. The measured thickness of the titanium dioxide coating is 490 angstroms, and the thickness and growth rate (150 angstroms/sec) are listed in Table 1. The optical properties of the obtained product include: the transmittance of the observation light source C (10° observer) is 62.3%, and the reflectance of the observation light source C is 35.6%. The extinction coefficient at 550 nm is 0.008, and the refractive index of the titanium dioxide coating is 2.44.

In Examples 2 and 3, the coating step in Example 1 was repeated, but in Example 2, ethyl formate was used as the organic source of oxygen, and isopropanol was used as the organic source of oxygen in Example 3. Uncoated glass (instead of the silica-coated glass in Examples 1 and 2) was used as the substrate. In the case of Example 2, the glass flow rate, the thickness of the obtained titanium dioxide coating and the growth rate are listed in Table 1. In Example 3, isopropanol was burned in the reactor, leaving only particulate titanium dioxide under the glass, and the corresponding deposition rate was expressed as 0 angstroms/sec.

The steps of Examples 4 and 5 are the same as those used in the above examples (reactor temperature and matrix are the same as in Example 1), but the matrix is static rather than dynamic. Place the static sample under the reactor for 10 seconds. Under static conditions, the retention time of the matrix in the reactor is increased to 5 times from that under dynamic conditions.

In Example 4, ethyl acetate was used as the organic source of oxygen, and tert-butyl acetate was used in Example 5, and a titanium dioxide coating was prepared in each case. The gas flow rate, the thickness of the obtained titanium dioxide coating and the coating growth rate are listed in Table 1. The relatively slow growth rate obtained with methyl acetate is discussed below.

Example 6 uses a float glass process in the preparation of a continuous glass ribbon, where the thickness of the glass ribbon is 0.125 inches/3 mm at a line speed of 434 inches or 11 meters per minute. In the float bath area where titanium dioxide is coated with a coating reactor similar to that shown in FIG. 3, the glass temperature is 1140°F/615°C at the desired implementation location. The temperature of the precursor spray tower is 400°F/205°C, and the temperature on the outside of the reactor is 500°F/260°C. Before implementing the method of the present invention, a silicon dioxide coating with a thickness of about 339 angstroms was deposited on the glass substrate in the float bath area. The silicon dioxide coating was deposited using the same chemical vapor deposition method as in Example 1. The deposition of silica does not form part of the invention.

A precursor gas mixture of titanium tetrachloride and ethyl acetate included in helium as a carrier gas was developed. Since the surface coating reaction of the previous embodiment is not sensitive to the concentration of oxygen, oxygen is not used in the precursor. The precursor mixture is prepared by simultaneously adding these three components through a multi-pipe system. The volume percentages of the precursor mixture components are 0.6% titanium tetrachloride, 1.8% ethyl acetate, and 97.5% helium. The flow rates of these components are: 480.0 l/m of helium, 3.0 l/m of titanium tetrachloride, and 9.2 l/m of ethyl acetate. The total flow rate of the precursor mixture is 492.2 l/m.

The thickness of the obtained titanium dioxide coating was 684 angstroms. The carbon content in the coating is less than 2 atomic %. The growth rate of the coating is 309 angstroms/sec.

Example 7 uses the same steps as Example 6 in this example. The precursor is a glass substrate with a silicon coating, followed by a silicon dioxide coating. These coatings are deposited by atomic chemical vapor deposition in the float bath area. The silicon coating is deposited from monosilane and non-oxidizing carrier gas according to CVD. Then, a silicon dioxide coating was deposited on the silicon coating by using the same procedure as in Example 1.

The precursor of the titanium dioxide coating includes titanium tetrachloride and ethyl acetate in a helium carrier gas. The volume percentage of the precursor component is 0.5% titanium tetrachloride, 1.9% ethyl acetate and 97.6% helium. The corresponding flow rates of these components are: 480.0l/m helium, 2.4l/m titanium tetrachloride, 9.2l/m ethyl acetate. The total flow rate of the precursor mixture is 491.6 l/m.

The obtained coated product 52 is shown in FIG. 2. The glass substrate 54 has many multilayer coatings 56. The coating includes a silicon coating 58, a silicon dioxide coating 60, and then a titanium dioxide coating 62 on the top of the article. The thickness of the titanium dioxide coating on the obtained product was 836 angstroms. The carbon content in the coating is less than 2 atomic %. The growth rate of the coating is 309 A/sec. The obtained optical performance of the coating group includes: the transmittance of the observation light source C is 13.1%, and the reflectance of the observation light source C is 82.5%. The growth rate of the titanium dioxide coating is 378 angstroms/sec. Table 1 Actual flow rate (L/min) Example Titanium tetrachloride organic oxygen compound Oxygen helium thickness Growth rate /sec 1 0.2 4.8 Ethyl acetate 2.0 20.9 490 1502 0.5 1.6 Ethyl formate 6.0 17.4 800 2503 0.45 1.5 Isopropanol 4.0 15.45 0 04 0.5 1.2 Methyl formate 6.0 17.4 <100 <105 0.5 0.5 tert-Butyl acetate 6.0 16.5 1300 130 Examples 8 to 13 In this series of examples, a static coater was used in the laboratory to prepare float glass with a color-suppressing silica coating as described in European Patent EP0 275 662B The substrate is coated with tin oxide coating.

The float glass to be coated was supported on a nickel block in the reactor, and the nickel block was heated by an electric heating element from the bottom so that the temperature of the glass was 1085°F/585°C. A graphite plate is fixed approximately 0.4 inches or 10 mm above the glass and parallel to the glass to provide an air flow channel with a depth of 0.4 inches or 10 mm between the silica-coated glass surface and the plate.

The precursor gas mixture is conveyed through a gas pipeline maintained at a temperature of 435±25°F/225±15°C and a fishtail nozzle with a gas flow channel leading to the top of the hot glass and parallel to the glass surface, wherein the precursor gas mixture includes The organic source of tin tetrachloride and oxygen in air as the carrier gas and a small amount of additional nitrogen. The total carrier flow rate is 13 cubic meters per hour. The flow rate of tin tetrachloride and the characteristics and flow rate of the organic compound used are listed in Table 2. In Examples 9 and 11, as described in the table, a small amount of 40% hydrogen fluoride was added to the precursor gas mixture in order to dope the obtained tin oxide coating with fluorine.

The gas flow containing the reaction gas is added for about 8 seconds, and the coating device and the coated glass are cooled in the air flow at 345°F/225°C. When disassembling the coating device, it was found that there were no deposits on the conveying gas pipes, nozzles, and the plates defining the gas flow channels above the glass in each case, which indicated that there was no undesirable pre-reaction. In each case, the glass has a tin oxide coating on the silicon dioxide, the thickness of which varies with the distance from the fishtail nozzle. The maximum thickness corresponding to each precursor gas mixture and the corresponding growth rate are listed in Table 2. The emissivity, resistivity and turbidity of the samples prepared using hydrogen fluoride to introduce fluorine dopants (Examples 9 and 11) were measured. The results are shown in Table 2.

This series of examples shows that an organic source of oxygen can be used as part of a pre-mixed precursor gas mixture containing tin tetrachloride to deposit tin oxide coatings without significant undesirable pre-reactions such as The deposition in the gas supply pipeline has an adverse effect on the coating process. In addition, if desired, a dopant source, such as hydrogen fluoride, can be added to the gas premix to reduce the emissivity and resistivity of the coating while continuously avoiding significantly unfavorable pre-reactions.

Embodiment 14 In this embodiment, the coating dispenser shown in FIG. 4 is used in the float bath to coat tin oxide coating according to the method of the present invention. The speed of the glass ribbon is approximately 233 inches/minute (350 meters/hour), and the glass thickness is 0.05 inches (1.2 mm). The glass temperature is approximately 1170°F/630°C. The temperature of the gas supply pipe 101 as the initial gas mixing chamber is maintained at 300°F/150°C, and the temperature of the gas distributor of the "static" grid structure is about 645°F/340°C. The tin tetrachloride and butyl acetate vapors are transported by means of bubbling nitrogen gas through the liquid maintained at 175°F/80°C in the bubbler, and thus enter the gas supply pipe 101 through the indirect heating pipe. The steam mixed in the initial chamber passes through the combined gas distributor of the grid structure, and then passes through the U-shaped guide channel 106 including the coating chamber 108 communicating with the hot glass ribbon under laminar flow conditions.

Table 2 Example precursor gas mixture maximum oxidation maximum increase emissivity resistivity Ha tin thickness velocity /secΩ/cmSnCl4 flow rate organic oxygen source 40% HF flow (ml/min) compound flow rate (ml/min) volume (ml /min) 8 12 Ethyl acetate 10-2750 344---9 12 Ethyl acetate 10 1 2680 335 0.25 5.3×10-40.4% 10 12 Butyl acetate 13.4-3460 432---11 12 Butyl acetate 13.4 1.3 2880 360 0.25 6.9×10-40.612 6 Isopropanol 120-2284 262---13 17 Trifluoroacetic acid 16.2-2840 335---

The flow rate used is sufficient for the molar ratio of tin tetrachloride to butyl acetate to be 1:1 to 1:5. The test was carried out for 5 hours. When disassembling the applicator, it was found that more than 90% of the cooling surface and related pipes were free of deposits, thus indicating that the tin tetrachloride and butyl acetate used to form the tin dioxide coating on the glass can be pre-mixed with each other, and There is basically no pre-reaction. A thin tin oxide coating is obtained on the glass ribbon.

It should be realized that various changes and improvements can be made to the present invention from the specific details of the present invention included in the above embodiments without departing from the spirit and scope defined by the appended claims. In its basic details, the present invention is a method for depositing tin oxide and titanium dioxide coatings at a high deposition rate by using corresponding metal tetrachlorides and organic compounds used as oxygen sources in a preformed precursor gas mixture. Continuous chemical vapor deposition method onto the glass substrate.

Because of the stability and cost of the raw materials, metal tetrachloride is the preferred metal source.

It has been found that particularly when depositing titanium dioxide coatings from titanium tetrachloride, that is to say in order to form metal oxides at an optimal deposition rate, it is desirable to use compounds containing organic oxygen, which are esters, especially those derived from alcohols. The group is an ester of an alkyl group with β hydrogen. Additionally, the decomposition temperature of the ester should not be higher than the reaction temperature of the coating precursor gas mixture where it is desired to be implemented. The ester with beta hydrogen and proper decomposition temperature used in the precursor gas mixture will deposit the coating at a high deposition rate. The ester group preferably used in the practice of the present invention includes the group consisting of ethyl formate, ethyl acetate, ethyl propionate, isopropyl formate, isopropyl acetate, n-butyl acetate and tert-butyl acetate.

Generally, esters decompose in a continuous manner within 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 single-molecule decomposition rate constants of general esters such as ethyl acetate and tert-butyl acetate are well known and can be found in the chemical literature. For ethyl acetate and tert-butyl acetate, the thermal decomposition temperatures as defined above are 935 and 650°F (500°C and 344°C), respectively. Those skilled in the art will recognize that the choice of ester and the specific decomposition temperature used determine the optimal coating growth rate. Lower than the specified thermal decomposition temperature, but the decomposition temperature in the decomposition range of the selected ester will obtain a lower coating growth rate.

According to the present invention, the alkyl group of the ester used in the coating precursor gas mixture may be a carbon compound having 2 to 10 carbon atoms. The lower limit of this range depends on the need for beta hydrogen on the alkyl group. The upper limit should avoid flammability and volatility problems caused when the alkyl group contains more than 10 carbon atoms.

In practicing the method of the present invention, a manifold can be used to connect and adjust a single gas flow to formulate a coating precursor gas mixture. A common transfer line can 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 uniform gas mixture. Additionally, the baffle in the gas distributor beam shown in FIG. 3 or the gas flow throttle valve shown in FIG. 4 can further mix the precursor gas in the reactor stage.

In many embodiments, oxygen is included in the coating precursor gas mixture. However, the deposition rate of the metal oxide coating is not sensitive to the oxygen concentration, and no oxygen is used in Example 6 or 7, which indicates that it is not necessary to include oxygen.

The concentration of the reactive components of the coating precursor gas mixture can be selected to obtain the best coating growth rate. The concentration of metal tetrachloride in the precursor gas mixture is generally 0.1 to 5.0% by volume. The concentration of metal tetrachloride is based on the amount of metal necessary to provide the desired coating thickness in the effective residence time. Therefore, the concentration of metal tetrachloride is adjusted according to process variables such as the linear velocity of the glass ribbon in the float glass process.

The concentration of the organic oxygen compound in the coating precursor gas mixture is generally 1 to 5 times the concentration of the metal tetrachloride, and is selected in this range based on the deposition temperature. When esters are used, a low deposition temperature results in a slower ester decomposition rate, and therefore a high ester concentration is required in order to react with the metal tetrachloride. In Examples 6 and 7, the optimum concentration of ethyl acetate in the precursor gas mixture is 1 to 3 times the concentration of titanium tetrachloride. A concentration higher or lower than the optimal range will result in a metal oxide coating at a lower coating growth rate.

The temperature of the precursor gas mixture is critical to the control of the reaction, especially to avoid undesirable pre-reactions or addition reactions that lead to the formation of non-volatile products in the preliminary pipeline. In a preferred embodiment, especially when esters are used, a temperature above 300°F/150°C is maintained in the precursor gas line. The temperature of the precursor gas mixture is preferably lower than the thermal decomposition temperature of the organic oxygen compound to prevent pre-reaction of the mixture.

The method of the present invention uses heat from the substrate to stimulate the coating reaction. In the online case, such as the float glass process, the matrix is formed at a particularly high temperature. Therefore, the present invention can be implemented in this position of the float glass process, that is, the temperature of the substrate at this position is reduced, but the temperature is still higher than the temperature at which the coating is formed (and preferably when the glass ribbon is substantially completely spread After that, it is below 1380°F/750°C). The offline application of the present invention requires heating the matrix above the decomposition temperature of the ester.

When the method of the present invention is implemented in the float glass process, the preferred implementation position is in the float bath area. The temperature at the coating location is usually about 1100-1320°F/590-715°C. Temperature is an important operating parameter because it affects the concentration of organic compounds used in the precursor gas mixture. The temperature of the substrate in the float bath area is relatively stable, and therefore hardly changes at the application position. In Examples 6 and 7 using ethyl acetate, the preferred substrate temperature is 1100-1250°F/590-680°C.

The temperature from the substrate raises the temperature of the precursor gas mixture above the temperature required for coating formation (and when esters are used as organic compounds, above the thermal decomposition temperature of the esters). The metal deposition reaction can be stimulated by the decomposition of organic oxygen compounds. When titanium tetrachloride and an ester having an alkyl group with β hydrogen are used, the deposition rate of the titanium dioxide coating formed on the substrate is 10 times higher than that of the known coating method. In the online application of float glass ribbon, the glass ribbon passes under the gas distributor beam at a relatively fast speed. When the glass ribbon passes under the coater, the metal oxide is deposited on the float glass.

The present inventors proposed the following theory regarding the chemical reaction that may occur when an ester having an alkyl group with β hydrogen is used. However, the present inventor does not want the present invention to be limited by this possible explanation, and therefore only provides this explanation to help understand the results of the method of the present invention.

The inventors proposed that when the ester is decomposed, the carbon-hydrogen bond on one of the β hydrogens is broken, the hydrogen is transferred to the carbonyl group, the alkene is eliminated and the carboxylic acid is formed. A hydrolysis reaction occurs simultaneously between the carboxylic acid and the metal tetrachloride, resulting in the formation of a metal oxide coating on the substrate.

In summary, the article prepared according to the present invention includes a substrate with a coating of titanium dioxide or tin oxide. The coating can be directly coated on the substrate or as one of multiple coatings on the substrate. The deposition rate of the metal oxide coating is affected by the deposition rate of the organic oxygen compound. At a constant reaction temperature, different organic oxygen compounds will provide different coating growth rates due to different decomposition temperatures. Therefore, for a given system, the desired growth rate of the metal oxide coating is selected by matching the temperature of the specific organic oxygen compound and the precursor gas mixture and the temperature of the substrate at the application site.

The deposition rate of titanium dioxide in the present invention is 10 times greater than that in the known deposition method. The method of the present invention allows the deposition rate to be higher than 130 angstroms/sec, and some of the measured deposition velocities far exceed 300 angstroms/sec. The higher deposition rate of titanium dioxide produces a coating with a refractive index higher than 2.4.

In addition to obtaining a high coating speed, the present invention also has the advantage of using low-cost metal precursor compounds. In particular, when the precursor gas mixture passes over the substrate under the conditions of preferred laminar flow, high coating speeds can be obtained. The conversion rate of (metal tetrachloride).

In the present invention, the obtained oxide coating includes a small amount of residual carbon from the decomposition of organic oxygen compounds, especially when esters are used. Carbon is an undesirable by-product of the coating reaction because the high content of carbon in the deposited coating causes adsorption problems for the coating. Related to the use of organic oxygen compounds in the coating precursor gas mixture is that decomposition leads to an increase in carbon content, which in turn affects the adsorption properties of the final glass. The carbon content in the coating prepared according to the method of the present invention is less than 4 atomic %. The low content of carbon does not significantly affect the absorption performance of the coating.

Obviously, the form of the present invention shown and described here is only considered to be an illustrative embodiment of the present invention, and various changes can be made in shape, size, and component arrangement, and can be changed procedurally without departing from The purpose of the present invention.