Method for producing coated glass articles

Abstract

The subject matter described herein relates to an atmospheric pressure chemical vapor deposition process for depositing a hafnium-containing coating on a glass substrate by reacting a precursor gas mixture including an organohafnium compound, molecular oxygen, and an olefinic hydrocarbon. A glass article having a hafnium-containing layer formed on the glass substrate is also provided.

Description

[Background technology]

[0001] Glass is an article produced when a viscous molten substance is cooled rapidly below its glass transition temperature without sufficient time for an ordered crystal lattice to form. Generally, glass articles are formed of silica-based materials and may contain approximately 70-72% silicon dioxide (SiO2) by weight. Glass articles are known to be used in architectural articles such as transparent materials for windows, interior glass partitions, and buildings. In addition to indoor and outdoor uses, glass articles may be used as windshields for various types of vehicles. Additionally, glass articles may be commonly used as various optical devices such as lenses and protective shields for various electronic devices in both consumer, scientific, and military applications.

[0002] Coatings can be applied to conventional glass articles to improve properties such as thermal conductivity, resistivity, radiation protection, anti-reflection, etc. Such coatings are applied in batches, requiring long processing times under high vacuum conditions.

[0003] Therefore, to produce affordable coatings for optical thin film stack designs, it is desirable to form hafnium-containing coatings essentially at atmospheric pressure and produce the coatings at deposition rates compatible with time-critical manufacturing processes, such as float flat glass production. Summary of the Invention

[0004] Surprisingly, consistent with and in accordance with the present disclosure, an atmospheric pressure CVD process has been discovered for depositing hafnium-containing coatings on glass substrates using a precursor gas mixture comprising an organohafnium compound and an olefinic hydrocarbon.

[0005] The subject matter described herein relates to a process for depositing a hafnium-containing coating on a flat glass substrate. More specifically, the subject matter described herein relates to an atmospheric pressure chemical vapor deposition (CVD) process for producing a hafnium-containing coating on flat glass at high growth rates using a precursor gas mixture that includes an organohafnium compound and an olefinic and hydrocarbon.

[0006] In one embodiment, a method of forming a coated glass article includes providing a glass substrate and depositing a hafnium-containing coating on the glass substrate using a chemical vapor deposition process that uses a precursor gas mixture including an organic hafnium compound, molecular oxygen, and an olefinic hydrocarbon, the precursor gas mixture being introduced into a vapor space above the glass substrate, and the organic hafnium compound and the olefinic hydrocarbon reacting to produce a hafnium-containing coating on the glass substrate, the hafnium-containing coating exhibiting a refractive index of about 1.7 to 1.9.

[0007] In another embodiment, a chemical vapor deposition process for depositing a coating on a moving glass substrate includes the steps of: providing a homogeneous precursor gas mixture including an organo-hafnium compound, molecular oxygen, and an olefinic hydrocarbon, each of the organo-hafnium compound and the olefinic hydrocarbon having a respective thermal decomposition temperature; delivering the precursor gas mixture at a temperature below the respective thermal decomposition temperatures of the organo-hafnium compound and the olefinic hydrocarbon to a location adjacent to a moving glass substrate to be coated, the moving glass substrate being surrounded by an atmosphere at a temperature above the thermal decomposition temperature of the organo-hafnium compound and having a pressure of about atmospheric pressure; and introducing the precursor gas mixture into a vapor space above the moving glass substrate, wherein the organo-hafnium compound and the olefinic hydrocarbon react to produce a coating on the glass substrate, the coating being a hafnium-containing coating exhibiting a refractive index of about 1.7-1.9.

[0008] In certain embodiments, the organohafnium compound is a hafnium amide compound.

[0009] In certain embodiments, the hafnium amide compound comprises tetrakisdialkylamidohafnium, Hf(NMe2)4.

[0010] In certain embodiments, the organohafnium compound is Hf(NR 1 R 2 )4 form of tetrakisdialkylamidohafnium compounds, where R 1 and R 2 is a hydrocarbon having 1, 2, or 6 carbon atoms.

[0011] In certain embodiments, the hafnium-containing coating has a thickness of at least 50 angstroms.

[0012] In certain embodiments, the precursor gas mixture further comprises helium.

[0013] In certain embodiments, the temperature of the glass substrate is at least 400° C., more preferably 425° C., when the precursor gas mixture is introduced during the chemical vapor deposition process.

[0014] In certain embodiments, the temperature of the glass substrate is between 425°C and 700°C, more preferably between 450°C and 700°C, when the precursor gas mixture is introduced during the chemical vapor deposition process.

[0015] In certain embodiments, the olefinic hydrocarbon is at least one of ethylene, propylene, and butene. In certain preferred embodiments, the olefinic hydrocarbon is ethylene.

[0016] In a particular embodiment, the hafnium-containing coating is a hafnium oxide coating.

[0017] In a particular embodiment, the glass substrate comprises soda-lime-silica glass.

[0018] In a particular embodiment, the glass substrate is formed by a float glass process.

[0019] In a particular embodiment, the hafnium-containing coating is deposited on the glass substrate at a deposition rate of at least 50 angstroms per second.

[0020] In certain embodiments, the coated glass article exhibits a haze of from about 0.09% to about 0.54%.

[0021] In certain embodiments, the coated glass article exhibits a visible light transmittance of from about 56% to about 91%.

[0022] In certain embodiments, the coated glass article exhibits a film side reflectance of from about 8% to about 23%.

[0023] In certain embodiments, the method further comprises depositing a silicon dioxide layer between the glass substrate and the hafnium-containing coating.

[0024] In certain embodiments, the silicon dioxide layer has a thickness of at least 200 angstroms.

[0025] In certain embodiments, the method further comprises depositing a tin oxide layer between the glass substrate and the silicon dioxide layer.

[0026] In certain embodiments, the temperature of the glass substrate is at least 400°C, more preferably 425°C, when the precursor gas mixture is introduced into the vapor space above the moving glass substrate.

[0027] In certain embodiments, the temperature of the glass substrate is between 425°C and 700°C, more preferably between 450°C and 700°C, when the precursor gas mixture is introduced into the vapor space above the moving glass substrate.

[0028] In certain embodiments, the chemical vapor deposition process further includes depositing a silicon dioxide layer between the moving glass substrate and the hafnium-containing coating.

[0029] In certain embodiments, the chemical vapor deposition process further includes depositing a tin oxide layer between the moving glass substrate and the silicon dioxide layer.

[0030] Also provided in accordance with the subject matter described herein is a hafnium-containing coated glass article. In one embodiment, the hafnium-containing coated glass article comprises a glass substrate having a surface. The glass article further comprises a silicon dioxide layer formed on the surface of the glass substrate, and a hafnium-containing layer formed on the silicon dioxide layer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] It is understood that the subject matter described herein may assume various alternative directions and sequences of steps unless expressly specified otherwise. It is also understood that the specific devices and processes described in the following specification are merely exemplary embodiments of the inventive concepts defined in the appended claims. Thus, unless expressly set forth otherwise in the claims, specific dimensions, directions, flow rates, or other physical characteristics associated with the disclosed embodiments should not be considered as limiting. Furthermore, although the subject matter described herein is described in the context of a float glass process, those skilled in the art will appreciate that the coating process described herein may also be applied to other manufacturing processes used to deposit hafnium-containing coatings. In the subject matter described herein, "hafnium-containing coating" refers to a hafnium oxide coating, a hafnium nitride coating, or a hafnium oxynitride coating.

[0032] The process of the subject matter described herein is generally carried out in connection with the formation of a continuous glass ribbon substrate, for example during float glass manufacturing / production. The subject matter described herein enables the production of hafnium-containing coatings deposited on a glass ribbon at high deposition rates, preferably at or above 50 angstroms per second, more preferably at or above 75 angstroms per second. However, it is noted that the deposition rate can be any suitable deposition rate as desired.

[0033] When coating substrates in manufacturing, high deposition rates are important. This is especially true in float glass manufacturing where the glass ribbon moves at a specific line speed and a specific coating thickness is required. To obtain high deposition rates, at least one olefinic hydrocarbon may be used in combination with at least one organic hafnium precursor compound to form a hafnium-containing coating without the need for deliberate addition of water vapor, gaseous oxygen, or other oxygen-containing compounds. The deposition rates obtained with preferred embodiments of the subject matter described herein may be 1.5 times or more higher than the deposition rates of other known processes for depositing hafnium-containing coatings.

[0034] Organohafnium compounds suitable for use in connection with the subject matter described herein preferably have the general formula Hf(NR 1 R 2 ) 4, where N is ethyl, methyl, propyl, butyl, or phenyl; R 1 and R 2 are the same or different and can be either alkyl groups having 1 to 6 carbon atoms, or other groups such as phenyl, tolyl, etc. Preferred hafnium amide compounds are tetrakisdialkylamido hafnium compounds. A particularly preferred precursor material is tetrakisdimethylamido hafnium, Hf(NMe2)4.

[0035] However, the subject matter described herein is not limited to only hafnium amide compounds, and other organic hafnium compounds may also be used in the practice of the subject matter described herein. For example, bis(methylcyclopentadienyl)dimethylhafnium, Hf[C5H4(CH3)]2(CH3)2, and bis(methylcyclopentadienyl)methoxymethylhafnium, Hf[C5H4(CH3)]2(OCH3)CH3, may also be used to form hafnium-containing coatings.

[0036] It has been found that olefinic hydrocarbons can be used in combination with organic hafnium compounds to form hafnium-containing coatings without the need for deliberate addition of water vapor, gaseous oxygen, or other oxygen-containing compounds. Olefinic hydrocarbons useful as precursor materials in connection with the subject matter described herein contain one or more double bonds. Preferred olefinic hydrocarbons for use in the practice of the subject matter described herein include ethylene, propylene, and butene. A particularly preferred olefinic hydrocarbon is ethylene.

[0037] Although it is believed that the precursor gases may be mixed at or very near the surface of the glass substrate, the subject matter described herein involves the preparation of a precursor gas mixture. The precursor gas mixture includes an organic hafnium compound and an olefinic hydrocarbon. The precursor gas mixture may further preferably include a carrier gas or a diluent. The carrier gas may include one gas or a combination of gases. Gases that may comprise the carrier gas include nitrogen, argon, and / or helium. For example, in another embodiment, the carrier gas includes helium. In another embodiment, the carrier gas includes nitrogen and helium. It should be understood that any suitable gas or combination of suitable gases may be used as the carrier gas. Regardless of the specific components, since the precursor gas mixture is comprised of multiple gases, it is preferable to premix the precursor gases to ensure that the gas mixture is substantially uniform prior to forming the hafnium-containing coating.

[0038] The pyrolysis of the organohafnium compound and the olefinic hydrocarbon can rapidly initiate the deposition reaction of the hafnium-containing coating. Therefore, before deposition is desired, the precursor gas mixture is maintained at a temperature below the temperature at which significant reaction occurs. Preferably, the precursor gas mixture is maintained at a temperature below the pyrolysis temperature of the organohafnium compound and the olefinic hydrocarbon until deposition is desired.

[0039] The precursor gas mixture is delivered adjacent to a moving glass substrate. Prior to deposition, the substrate is at a temperature above the thermal decomposition temperature of the organohafnium compound in the precursor gas mixture. The precursor gas mixture is then introduced into the vapor space above the substrate. Heat from the substrate raises the temperature of the precursor gas mixture above the thermal decomposition temperature of the organohafnium compound. The primary reactants then react with each other to produce a hafnium-containing coating on the substrate.

[0040] The deposition rate depends on the particular olefinic hydrocarbon used, the concentration of the olefinic hydrocarbon and the organohafnium compound, and the temperature of the glass substrate. In particular, the use of ethylene results in a particularly efficient reaction with the tetrakisdialkylamidohafnium compound. The exact role of ethylene in depositing hafnium-containing coatings from organohafnium compounds has not been established. It should be understood that increasing the reactant concentration and gas flow rates may reduce the overall conversion efficiency of the reactants to the coating. Thus, the optimum conditions for commercial operation may differ from those that provide the highest deposition rates.

[0041] The subject matter described herein allows for rapid production of hafnium-containing coatings on moving hot flat glass substrates during the float glass manufacturing process. Deposition of the hafnium-containing coating requires that the temperature of the moving glass substrate be at least 400° C. when the precursor gas mixture is introduced into the vapor space above the moving glass substrate. Typically, in practicing the subject matter described herein, the temperature of the glass substrate is in the range of about 450° C. to 750° C. More preferably, the substrate temperature is in the range of about 450° C. to 700° C. Regardless of the substrate temperature during deposition, the hafnium-containing coatings produced according to the subject matter described herein have been found to have a refractive index in the range of about 1.7 to about 1.9. This allows for desirable optical effects to be achieved, especially when used in combination with other coating layers. It should be noted that the refractive index values ​​described herein are reported as average values ​​over the electromagnetic spectrum from 400 to 780 nm.

[0042] When a float glass facility is utilized as a means for practicing the subject matter described herein, the float glass apparatus more specifically comprises a canal section along which molten glass is delivered from a melting furnace to a float bath section where a float process forms a continuous ribbon of glass. The glass ribbon advances from the bath section through adjacent annealing furnaces and a cooling section. The continuous ribbon of glass serves as a substrate upon which a hafnium-containing coating is deposited in accordance with the subject matter described herein.

[0043] The bath section includes a bottom section in which a bath of molten tin is contained, a roof, opposing side walls, and end walls. It is understood that the bath may include other suitable materials to achieve the desired results. The roof, side walls, and end walls together form an enclosure in which a non-oxidizing atmosphere is maintained to prevent oxidation of the molten tin. Additionally, a gas distribution beam may be disposed in the bath section. The gas distribution beam in the bath section may be used to apply a hafnium-containing coating or to apply an additional coating on the substrate by the subject process described herein prior to applying the hafnium-containing coating. The additional coating may include, for example, tin oxide and / or silicon dioxide.

[0044] During operation, the molten glass flows downwards along the canal below the alignment pins in a controlled amount onto the surface of the tin bath. On the tin bath, the molten glass spreads laterally under gravity, surface tension, and certain mechanical influences, advancing through the bath to form a ribbon. The ribbon is removed on a lift-out roll and then conveyed through the annealing furnace and cooling section on aligned rolls. Heaters may be provided in the annealing furnace to gradually reduce the temperature of the glass ribbon according to a predetermined regime as it is conveyed. Ambient air may also be directed toward the glass ribbon, typically by a fan in the cooling section.

[0045] Application of the hafnium-containing coating of the subject matter described herein may occur within the float bath section or further along the production line, for example, the hafnium-containing coating may be deposited in the gap between the float bath and the annealing furnace, or within the annealing furnace itself.

[0046] To form the coating within the bath section, a suitable non-oxidizing atmosphere, generally nitrogen or a mixture of nitrogen and hydrogen with a predominance of nitrogen, is maintained to prevent oxidation of the molten tin. The atmospheric gas is introduced through a conduit operatively coupled to the distribution manifold. The non-oxidizing gas is introduced at a rate sufficient to maintain a slight positive pressure, on the order of about 0.001 to about 0.01 atmospheres above ambient atmospheric pressure, to compensate for normal losses and prevent ingress of external atmosphere. For purposes of the subject matter described herein, the above pressure range is deemed to constitute normal atmospheric pressure. Heat to maintain the desired temperature regime within the tin bath and bath housing is provided by radiant heaters within the housing and by the glass ribbon itself.

[0047] The atmosphere in the furnace is typically air. However, when forming a hafnium-containing coating in a furnace, an inert atmosphere may be maintained in the furnace section where deposition occurs. Similarly, the atmosphere in the gap between the furnace and the bath is typically air and the atmosphere of the bath section, but when depositing a hafnium-containing coating therein, an inert atmosphere may also be provided. In either case, the pressure of the inert atmosphere may be substantially similar to the pressure of the atmosphere in the bath section.

[0048] The gas distribution beam may be located in the bath section, in the gap between the bath section and the annealing furnace, or within the annealing furnace to deposit various coatings on the glass ribbon substrate. The gas distribution beam is one form of reactor that may be used in carrying out the subject processes described herein.

[0049] A suitable distribution beam configuration for delivering precursor material in accordance with the subject matter described herein is an inverted, generally channel-like framework formed by spaced apart inner and outer walls defining two enclosed cavities, through which a suitable heat exchange medium is circulated to maintain the distribution beam at a desired temperature.

[0050] The precursor gas mixture is supplied through a supply conduit. Depending on the location of deposition, the supply conduit may be surrounded by a cooling fluid. The supply conduit extends along a distribution beam and introduces the precursor gas mixture through drop lines spaced along the supply conduit. The supply conduit leads to a delivery chamber in a header supported by a framework. The precursor gas mixture introduced through the drop lines exits the delivery chamber through a passageway toward a coating chamber that defines a vapor space opening above the glass substrate, where the precursor gas mixture flows along the surface of the substrate.

[0051] A baffle plate may be provided in the delivery chamber to equalize the flow of the precursor gas mixture across the distribution beam and ensure that the precursor gas mixture is discharged to the glass substrate in a smooth, laminar, uniform flow across the distribution beam. Spent precursor gases are collected and removed through an exhaust chamber along the side of the distribution beam.

[0052] Various forms of distribution beams used in chemical vapor deposition are suitable for the method of the present invention and are known in the art. In one such alternative distribution beam configuration, the precursor gas mixture is introduced through a gas supply duct where it is cooled by a cooling fluid circulating through a number of ducts. The gas supply duct opens through an elongated opening into a glass flow restrictor.

[0053] The gas flow restrictor comprises a plurality of metal strips that are sinusoidally crimped longitudinally and vertically attached in abutting relationship to one another extending along the length of the distributor. Adjacent crimped metal strips are arranged "out of phase" to define a plurality of vertical channels therebetween. These vertical channels have a small cross-sectional area compared to the cross-sectional area of ​​the gas supply duct such that the precursor gas mixture is discharged from the gas flow restrictor at a substantially constant pressure along the length of the distributor.

[0054] The precursor gas mixture is discharged from the gas flow restrictor into the inlet side of a substantially U-shaped guide channel, which generally comprises an inlet section of the coating chamber that opens onto the glass substrate to be coated and at least one exhaust section, and the used precursor gas is removed from the glass. It should be understood that the guide channel may have any suitable size, shape, and configuration, as desired. The rounded corners of the blocks that define the coating channel promote a uniform laminar flow of the coating parallel to the glass surface across the entire glass surface to be coated. EXAMPLES

[0055] The following examples (unless otherwise specified, gas volumes are expressed under standard conditions, i.e., 1 atmosphere pressure and ambient temperature) are for illustrative purposes only and should not be construed as limiting the subject matter described herein.

[0056] The following experimental conditions apply to Comparative Examples 1 and 2 in Table 1, Examples 3 and 4, and Examples 5 to 12 in Table 2.

[0057] In Examples 1-12, the organohafnium compound used was tetrakisdimethylamidohafnium. Preparation and containment of the organohafnium compound and ethyl acetate, EtOAc, was accomplished utilizing multiple source chambers known as bubblers. There was one bubbler for each of the organohafnium compound and EtOAc, each maintained at a specific temperature. In Examples 1-12, the organohafnium compound bubbler was maintained at a temperature of about 100° C. In Examples 1-12, the EtOAc bubbler was maintained at a temperature of about 60° C. To deliver the precursor gas mixture, helium gas was introduced into the bubbler at a specific flow rate as listed in Table 1.

[0058] At ambient temperature, oxygen and ethylene are gases; therefore, neither needs to be placed in a bubbler and heated. However, it is preferable to preheat both before premixing either with the organohafnium compound. The amount of preheating is not critical, but should be sufficient to raise the temperature of either to a temperature similar to that of the organohafnium compound.

[0059] The glass substrate was heated to a desired temperature and passed through a laboratory furnace having a 25.4 cm wide two-way coater positioned above the glass substrate. The coater was adapted to distribute gaseous reactants onto the surface of the glass substrate to form a coating layer or stack of layers by chemical vapor deposition.

[0060] Table 1 summarizes the deposition flow rates of the precursor gas mixtures delivered to the surface of the glass substrate in accordance with the subject matter described herein. The various reactants described below were premixed into a homogenous precursor gas mixture before being introduced into the vapor space above the glass substrate. At the time the precursor gas mixture was introduced into the vapor space above the glass substrate, the temperature of the substrate used in Example 1 was 454° C., the temperature of the substrate used in Example 2 was 632° C., the temperature of the substrate used in Example 3 was 632° C., and the temperature of the substrate used in Example 4 was 632° C.

[0061] Examples 1-3 were carried out under static conditions using a soda-lime-silica glass substrate pre-deposited with a 200 Angstrom thick silicon dioxide layer. Example 4 was carried out under dynamic conditions at a line speed of 75 inches / min using a soda-lime-silica glass substrate pre-deposited with a 200 Angstrom thick silicon dioxide layer.

[0062] [Table 1]

[0063] NOTE: All flow rates are standard liters / min.

[0064] No hafnium-containing layer was formed in Comparative Examples 1 and 2. In Example 3, the hafnium-containing layer was formed at a rate of 160 Angstroms per second. In Example 4, the hafnium-containing layer was formed at a rate of about 85 Angstroms per second. The thickness of the hafnium-containing coating was measured optically.

[0065] Table 2 summarizes the input parameters and coating properties for Examples 5-12 according to the subject matter described herein. The various reactants described below were premixed into a homogenous precursor gas mixture before being introduced into the vapor space above the glass substrate. Examples 5-12 were carried out under static conditions using a glass substrate. In addition to the input parameters shown in Table 2 for Examples 5-12, molecular oxygen (O2) was also introduced. The source of molecular oxygen for Examples 5-12 was the ambient air.

[0066] [Table 2]

[0067] The coating of Example 9, deposited at the lower substrate temperature, was not thick enough to be acceptable for most applications.

[0068] It should be noted that the subject process described herein can be repeated as necessary on a given substrate to form a coating consisting of several successive layers, the composition of each layer not necessarily being identical. Of course, for a given flow rate of reactants, it is clear that the thickness of the coating layer depends on the speed of movement of the substrate. Under these conditions, if desired, the reaction stations can be increased by juxtaposing two or more coating devices. In this way, successive layers are superimposed before the layers cool, producing a particularly homogeneous overall coating and / or coating stack.

[0069] In carrying out the subject matter described herein, it may be preferable to apply a layer of material that acts as a sodium diffusion barrier between the glass substrate and the hafnium-containing coating. For example, it has been found that when a hafnium-containing coating deposited according to the subject matter described herein is applied to a glass substrate with a sodium diffusion layer in between, the coated glass article exhibits lower haze compared to when applied directly onto the glass. This is particularly true when the glass substrate is a soda-lime-silica glass. Thus, in one embodiment, a sodium diffusion layer comprising silicon dioxide is formed on the surface of the glass substrate. In this embodiment, the layer of silicon dioxide, which is preferably formed using conventional CVD techniques, is preferably at least 200 angstroms thick.

[0070] In another embodiment, a layer of tin oxide is first deposited on the surface of the glass substrate, and a layer of silicon dioxide is deposited thereon. The layer of tin oxide is deposited on the surface of the glass substrate and adheres to the surface of the glass substrate. This forms a tin oxide / silicon dioxide underlayer structure formed between the glass and the layer of hafnium-containing coating that is subsequently deposited. In this embodiment, the silicon dioxide film not only functions as a sodium diffusion barrier, but also, in combination with the first (undoped) tin oxide film, helps to suppress the iridescence of the resulting coated glass article. The use of such anti-iridescence layers is disclosed in U.S. Pat. No. 4,377,613, the entirety of which is incorporated herein by reference.

[0071] The subject matter described herein is disclosed in what are considered to be its preferred embodiments. It will be understood, however, that the specific embodiments are provided by way of example only, and that the subject matter described herein can be practiced otherwise than as specifically illustrated without departing from its spirit and scope.

Claims

1. 1. A method of forming a coated glass article, comprising: providing a glass substrate; depositing a hafnium-containing coating on the glass substrate using a chemical vapor deposition process; The chemical vapor deposition process uses a precursor gas mixture including an organohafnium compound, molecular oxygen, and an olefinic hydrocarbon; the precursor gas mixture is introduced into a vapor space above the glass substrate; the organic hafnium compound and the olefinic hydrocarbon react to form the hafnium-containing coating on the glass substrate; the hafnium-containing coating exhibits a refractive index of about 1.7 to 1.9; A method for forming a coated glass article.

2. 1. A chemical vapor deposition process for depositing a coating onto a moving glass substrate to form a coated glass article, comprising: providing a homogeneous precursor gas mixture comprising an organohafnium compound, molecular oxygen, and an olefinic hydrocarbon, the organohafnium compound and the olefinic hydrocarbon each having a respective thermal decomposition temperature; delivering the precursor gas mixture, at a temperature below the respective thermal decomposition temperatures of the organohafnium compound and the olefinic hydrocarbon, to a location adjacent to the moving glass substrate to be coated, the moving glass substrate being surrounded by an atmosphere at a temperature above the thermal decomposition temperature of the organohafnium compound and having a pressure of about atmospheric pressure; introducing the precursor gas mixture into a vapor space above the moving glass substrate, and the organohafnium compound and the olefinic hydrocarbon react to produce the coating on the glass substrate, the coating being a hafnium-containing coating exhibiting a refractive index of about 1.7 to 1.

9. A chemical vapor deposition process in which a coating is deposited onto a moving glass substrate to form a coated glass article.

3. 3. The method of claim 1 or the chemical vapor deposition process of claim 2, wherein the organohafnium compound is a hafnium amide compound.

4. The hafnium amide compound is tetrakis(dialkylamido)hafnium, Hf(NMe ２ ) ４ 4. The method or chemical vapor deposition process of claim 3, comprising:

5. The organic hafnium compound is Hf(NR １ R ２ ) ４ and R １ and R ２ 3. The method of claim 1 or the chemical vapor deposition process of claim 2, wherein is a hydrocarbon having 1, 2, or 6 carbon atoms.

6. 3. The method of claim 1 or the chemical vapor deposition process of claim 2, wherein the hafnium-containing coating has a thickness of at least 50 angstroms.

7. 3. The method of claim 1 or the chemical vapor deposition process of claim 2, wherein the precursor gas mixture further comprises helium.

8. 3. The method of claim 1 or the chemical vapor deposition process of claim 2, wherein the temperature of the glass substrate is at least 400°C, preferably 425°C, when the precursor gas mixture is introduced into the vapor space.

9. 3. The method of claim 1 or the chemical vapor deposition process of claim 2, wherein the temperature of the glass substrate when the precursor gas mixture is introduced into the vapor space is between 425°C and 700°C, preferably between 450°C and 700°C.

10. 3. The method of claim 1 or the chemical vapor deposition process of claim 2, wherein the olefinic hydrocarbon is at least one of ethylene, propylene, and butene.

11. 3. The method of claim 1 or the chemical vapor deposition process of claim 2, wherein the olefinic hydrocarbon is ethylene.

12. 3. The method of claim 1 or the chemical vapor deposition process of claim 2, wherein the hafnium-containing coating is a hafnium oxide coating.

13. 3. The method of claim 1 or the chemical vapor deposition process of claim 2, wherein the glass substrate or moving glass substrate comprises soda-lime-silica glass.

14. 3. The method of claim 1 or the chemical vapor deposition process of claim 2, wherein the glass substrate or the moving glass substrate is formed by a float glass process.

15. 3. The method of claim 1 or the chemical vapor deposition process of claim 2, wherein the hafnium-containing coating is deposited on the glass substrate or the moving glass substrate at a deposition rate of at least 50 angstroms per second.

16. 3. The method of claim 1 or the chemical vapor deposition process of claim 2, further comprising depositing a silicon dioxide layer between the glass substrate or the moving glass substrate and the hafnium-containing coating.

17. 17. The method or chemical vapor deposition process of claim 16, wherein the silicon dioxide layer has a thickness of at least 200 angstroms.

18. 17. The method or chemical vapor deposition process of claim 16, further comprising depositing a tin oxide layer between the glass substrate or the moving glass substrate and the silicon dioxide layer.