A method of depositing a coating utilizing a coating apparatus

Description

Background Art [0001] The invention relates to a method of depositing a coating using a coating apparatus. More specifically, the invention relates to a method that inhibits the formation of a coating and by-products that result from the deposition of a coating on a coating apparatus during deposition of a coating on a glass substrate.

[0002] Thin film coatings can be formed using a coating apparatus to deposit a thin film coating on, for example, a glass substrate during a glass manufacturing process. However, known methods for the production of coatings that contain silicon oxides on glass substrates use precursor materials (reagents) that react undesirably. For example, known precursor materials can react to form by-products before and during coating on a glass substrate. The resulting by-products, which often take the form of fine particles or powder, can form blockages in the coating apparatus. The powder needs to be removed from the coating apparatus to create an aesthetically pleasing and uniform coating on the glass substrate.

[0003] Various methods are known for removing powder from a coating apparatus. For example, the powder can be removed mechanically from the coating apparatus. Mechanical removal of the powder can be carried out after coating deposition. However, the disadvantages of this method are the shortened deposition times as well as its time and effort.

[0004] Alternatively, US Patent No. 6,857,433 describes a method of cleaning a glass coating reactor. The method requires that the reactor contain a glass substrate in the chamber and that the deposition gas flow to the reactor is completed. Cleaning gas is then added to the reactor to react with substances formed on the inner surface of the chamber. This method also suffers from shorter deposition processes, as the coating process is interrupted to remove substances formed in the chamber.

[0005] It is therefore desirable to develop an improved method for depositing coatings that contain silicon oxide on glass substrates.

Brief description of the invention [0006] A coating deposition method is provided that uses a coating apparatus according to claim 1. The method comprises providing a coating apparatus over a glass substrate and forming a coating on the surface of the glass substrate while flowing into the apparatus for coating the fluorine-containing compound. The fluorine-containing compound inhibits the formation of a coating on one or more parts of the coating apparatus.

[0007] In another embodiment, the method includes providing a coating apparatus over a moving glass substrate. The coating apparatus has one or more exhaust gas channels. The method also includes forming a silica coating on the surface of the glass substrate while flowing into the apparatus for coating the fluorine-containing compound. The silica coating is fluorine free or contains only trace amounts. A fluorine-containing compound inhibits the formation of a silica coating in one or more exhaust gas channels.

[0008] Preferably, the coating comprises silicon oxide. Preferably, the glass substrate is moved. Preferably, the method further comprises placing the coating apparatus in a deposition chamber. Preferably, the coating is formed on the surface of the glass substrate by chemical vapor deposition. Preferably, the glass substrate has a temperature between about 566 ° C (1050 ° F) and 760 ° C (1400 ° F). Preferably, the coating does not contain fluorine or contains only trace amounts thereof.

PAT-3489-EP-E

EP2879999 [0009] The coating apparatus comprises one or more exhaust gas channels and a fluorine containing compound is introduced into the exhaust gas channel. Preferably the hydrogen fluoride containing compound is anhydrous HF. Preferably, the fluorine-containing compound inhibits the formation of a coating in one or more exhaust gas channels. Preferably, the fluorine-containing compound inhibits the formation of a coating on the surface of the coating apparatus.

[0010] Preferably, the method comprises forming a gaseous mixture containing a silicon containing compound, an oxygen containing compound and a scavenger, flow of the gaseous mixture to the coating apparatus, and directing the gaseous mixture through the coating apparatus to the surface of the glass substrate.

[0011] Preferably, the fluorine-containing compound enters the coating apparatus prior to forming a coating on the surface of the glass substrate. Preferably the coating is a silica coating. Preferably, the fluorine-containing compound is introduced into each exhaust gas channel through separate gas distribution pipes. The ratio of fluorine-containing compound to silicon-containing compound entering the coating apparatus is equal to or greater than 2: 1. Preferably, the ratio of the fluorine-containing compound to the silicon-containing compound entering the coating apparatus is equal to or greater than 4: 1.

[0012] In another embodiment, the invention provides a method of depositing a coating using a coating apparatus comprising: providing a coating apparatus that contains one or more exhaust gas channels above a moving glass substrate and forming a silica coating on the surface of the glass substrate that is free of fluorine or contains only trace amounts thereof, while flowing to the apparatus for coating the fluorine-containing compound , wherein the fluorine-containing compound inhibits the formation of a silica coating in one or more exhaust gas channels.

[0013] Preferably, the glass substrate has a temperature between about 566 ° C (1050 ° F) and 760 ° C (1400 ° F).

[0014] Preferably, the method further comprises forming a gaseous mixture containing a silicon containing compound, an oxygen containing compound and a scavenger, flow of the gaseous mixture to the coating apparatus, and directing the gaseous mixture through the coating apparatus to the surface of the glass substrate, the ratio of fluorine containing compound to compound silicon containing flowing into the coating apparatus is equal to or larger than 4: 1.

[0015] In another embodiment outside the scope of the invention, a coated glass substrate comprising a coating, a coating deposited by using a coating apparatus comprising: providing a coating apparatus over a glass substrate and forming a coating on the surface of the glass substrate while flowing to the apparatus for coating the fluorine-containing compound, wherein the fluorine-containing compound inhibits the formation of a coating on one or more parts of the coating apparatus.

[0016] All the features described herein can be combined with any of the above embodiments in any combination.

[0017] The above, as well as other advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description taken in light of the accompanying drawings, among which:

Figure 1 is a schematic view of a glass plant according to one embodiment of the invention, Figure 2 is a schematic view of a coating apparatus according to one embodiment of the invention

PAT-3489-EP-E

EP2879999 Figure 3 is a cross-sectional view of the coating apparatus of Figure 2, Figure 4 is a perspective view of a gas distribution pipe in accordance with one embodiment of the invention, and Figure 5 is a perspective view of a portion of the gas distribution pipe of Figure 4.

Detailed description of the invention [0018] It should be understood that the invention may assume various alternative orientations and order of steps, unless expressly stated otherwise. It should also be understood that the specific apparatuses and methods illustrated in the accompanying drawings and described in the following description are merely illustrative embodiments of the inventive concepts. Thus, specific dimensions, directions, or other physical characteristics pertaining to disclosed embodiments should not be construed as limiting, unless expressly stated otherwise.

[0019] A method of depositing a coating is provided. Referring to Fig. 1, in one embodiment, the method includes providing a coating apparatus 10 over a glass substrate 12 and forming a coating on the surface 14 of the substrate 12 while flowing into the coating apparatus 10 of the fluorine-containing compound. Preferably, the coating does not contain fluorine or contains only trace amounts thereof. The fluorine-containing compound inhibits the formation of the coating and / or by-products resulting from the deposition of the coating on one or more parts of the coating apparatus 10. The term "inhibits", its derivatives and other terms with similar meaning as used herein refer to removal or prevention of formation coating and / or by-products resulting from coating deposition on one or more parts of the coating apparatus.

[0020] Preferably, the coating comprises silicon oxide. More preferably, the coating is silicon dioxide (SiO2), which will be referred to as "silica" in the remainder of the description. Preferably, the silica coating substantially contains silicon and oxygen. However, trace amounts of impurities, for example carbon and / or fluorine, may be contained in the silica coating.

[0021] The method will be described with reference to the deposition of a silica coating. However, it should be noted that the application of the method is not limited to the deposition of silica coatings. For example, a silicon oxycarbide or silicon oxynitride coating may be deposited using the method.

[0022] In some embodiments, the method will be described with respect to forming a coated glass article. The coated glass product can have many applications and can be used in many applications. For example, a coated glass product can be used in architectural glazing. The coated glass product can be used in solar, electronic, automotive and aviation applications.

[0023] Preferably, the coating apparatus 10 is placed in the deposition chamber 18. The method can advantageously be carried out in place while the coating apparatus 10 is located inside the deposition chamber 18. Furthermore, the method does not require interrupting the formation of the coating on the glass substrate 12. Thus thus, the method described herein allows longer deposition runs than those known. Finally, the method inhibits the formation of by-products that result from coating deposition, such as, for example, silicon oxide, while known methods attempt to remove by-products after they are formed.

[0024] Preferably, the silica coating is formed using precursor materials and a chemical vapor deposition (CVD) method. More preferably, the deposition surface 14 of the glass substrate 12 is substantially at atmospheric pressure when forming over or on top of it. Same

PAT-3489-EP-E

EP2879999 the silica coating can be formed using the atmospheric pressure CVD (APCVD) method. However, it is worth noting that the silica coating can be created using a different CVD method. [0025] A feature of the method is that it allows the formation of a silica coating at a commercially real deposition rate and, as mentioned above, does not require interrupting the formation of the silica coating on the glass substrate or moving the coating apparatus 10 until it is desired. When depositing coatings on a glass substrate, high deposition rates are important. This is particularly the case when the glass substrate 12 is a glass ribbon traveling at a line speed in the range of several hundred inches per minute and it is desirable to deposit the silica coating at a certain thickness in a split second. For example, the method inhibits the formation of a coating and / or by-products on one or more parts of the coating apparatus 10 while forming a silica coating on the deposition surface 14 of the glass substrate 12 at a deposition rate of, for example, about 5 or more nanometers per second (nm / s ).

[0026] For any particular combination of precursor materials, the optimal concentrations and flow rates to achieve a specific rate of silica deposition on the glass substrate may vary. Furthermore, it is noteworthy that for any particular combination of precursor materials, optimal concentrations and flow rates for achieving a specific deposition rate can be determined by testing or computer modeling. It is also worth noting that the use of higher concentrations and / or higher flow rates of a particular precursor material can lead to less efficient overall conversion of the reagents to the silica coating, so that optimal conditions for commercial operation may differ from those that provide the highest deposition rates.

[0027] In one embodiment, the glass substrate 12 is soda lime silicate glass. In this embodiment, the glass substrate 12 may be substantially transparent. However, the method is not limited to transparent glass substrates, since translucent glass substrates can also be used in the practical implementation of the method. Furthermore, the transparency or absorption characteristics of the glass substrate 12 used may vary between embodiments of the invention. Similarly, the invention is not limited to the use of a substrate 12 having a particular composition, such as, for example, glass substrates 12 of a borosilicate composition may be used in the method. In addition, the method is not limited to the specific thickness of the glass substrate.

[0028] In an embodiment, the method can be implemented in practice under dynamic deposition conditions. In this embodiment, the glass substrate 12 moves during the formation of the silica coating. In another embodiment, the glass substrate 12 may be heated. Preferably, in this embodiment, the temperature of the glass substrate 12 when forming a silica coating over it or on it is between 566 ° C (1050 ° F) and 760 ° C (1400 ° F). Preferably, during the practical implementation of the method, the glass substrate 12 is displaced and heated.

[0029] The method can be carried out in practice in connection with the production of the glass substrate 12. The production of the glass substrate 12 can be carried out using the well-known method of producing float glass. In these embodiments, it is preferred that the glass substrate 12 is a glass ribbon and when describing such embodiments of the method, the glass substrate 12 may be treated as such. Most preferably, in the practical implementation of the method, the glass substrate 12 is displaced, heated, and is a glass ribbon.

[0030] An exemplary illustration of the planted glass system 20 used in the production of glass system is shown in Figure 1. It is worth noting that the plant 20 for glass system described herein and

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EP2879999 shown in Fig. 1 only illustrates such installations and that the method is not limited to use only with such an installation in Fig. 1. It is also worth noting that the method can be carried out in practice separately from the method of producing float glass or separately from creating and cutting a substrate glass.

[0031] As illustrated in Figure 1, the float glass plant 20 includes a channel section 22 along which molten glass 24 is supplied from the melting furnace to the flotation bath section 25 where a glass ribbon is formed. The glass ribbon is moved from the flotation bath section 25 through the adjacent tunnel compressor 26 and cooling section 28. The flotation bath section 25 includes a bottom section 30 in which a molten tin bath 32, roof 34, opposed side walls (not shown) and end walls 36 are included. In this embodiment the roof 34, side walls and end walls 36 define together the deposition chamber 18. When describing this and other embodiments, the deposition chamber 18 may be referred to as a flotation bath chamber. In these embodiments, a non-oxidizing atmosphere is maintained in the deposition chamber 18.

[0032] The glass ribbon is removed from the flotation bath section 25 on extraction rollers 40 and then transferred through tunnel compressor 26 and cooling section 28 on aligned rollers. Deposition of the silica coating preferably takes place in the flotation bath section 25, and more particularly in the flotation bath chamber. However, it is possible for the deposition to take place further along the glass production line, for example in the space 42 between the flotation bath section 25 and the tunnel compressor 26 or in the tunnel compressor 26.

[0033] The non-oxidizing atmosphere is essentially nitrogen or a mixture of nitrogen and hydrogen, with nitrogen dominating and being maintained in the flotation bath chamber to prevent oxidation of molten tin 32. Atmospheric gas is admitted through lines 43 operably coupled to the distribution manifold 45. Non-oxidizing gas is introduced at a rate sufficient to compensate for normal losses and to maintain a slight overpressure, on the order of from about 0.001 to about 0.01 above atmospheric pressure, so that the penetration of the atmosphere from outside is prevented.

[0034] When describing the method, the pressure range indicated above is treated as normal atmospheric pressure. It should be noted that in addition to the pressure in the flotation bath chamber, at the level of essentially atmospheric pressure there can also be pressure in the tunnel decompressor 26 and / or in the space 42 between the flotation bath section 25 and the tunnel decompressor 26 and in the practical implementation of the method the coating apparatus 10 . However, it should also be noted that the method is not limited to practical implementation at substantially atmospheric pressure. Thus, a silica coating can be formed and the process can be implemented in practice under vacuum.

[0035] Heat for maintaining the desired temperature regime in the molten tin 32 and the flotation bath chamber is supplied by radiating heaters 44 in the chamber. The atmosphere in tunnel compressor 26 is typically atmospheric air because the cooling section 28 is not closed and part of the glass ribbon is open there to the ambient atmosphere. Ambient air can be directed to the glass ribbon through fans 46 in cooling section 28. Heaters (not shown) may also be provided in the tunnel compressor 26 to cause a gradual decrease in the temperature of the glass web in accordance with a predetermined regime during its conveyance through the compressor.

[0036] The precursor materials used to form the silica coating are provided at a temperature below the temperature at which they react to form the silica coating and the glass substrate 12 has a temperature above the reaction temperature. Such materials may at some point be liquid or solid, but are volatile so that they can be evaporated for use in the gaseous state. When they are in a gaseous state, materials

PAT-3489-EP-E

EP2879999 precursor is delivered to the deposition surface 14 of the glass substrate 12 and they react chemically in a predetermined manner. The reaction leads to the deposition of a silica coating on a glass substrate 12.

[0037] Gaseous precursor materials are mixed to form a silica coating on a glass substrate 12. The precursor materials can be mixed inside or outside the coating apparatus 10 to form a gaseous mixture. In one embodiment, separate feed lines extend from the precursor material sources to the coating apparatus. In this embodiment, the precursor materials are mixed inside the coating apparatus 10 or outside the coating apparatus 10 so as to form a gaseous mixture upon release. Alternatively, the precursor materials can be fed to the coating apparatus 10 in a single batch. In such an embodiment, the gaseous precursor material mixture is formed before it is fed to the coating apparatus 10.

[0038] Preferably, the gaseous mixture contains precursor materials suitable for forming a silica coating under substantially atmospheric pressure. In one embodiment, the gas mixture of precursor materials comprises a silicon containing compound, an oxygen containing compound and a radical scavenger.

[0039] Preferably the silicon containing compound is a silane compound. The preferred silane compound is monosilane (SiH4). However, the process is not limited to the use of monosilane only, since other silane compounds are suitable for use in forming the silica coating. For example, suitable silane compounds for use in forming the silica coating are dichlorosilane (SiHiCl ·) and / or trichlorosilane (SiHCl ·).

[0040] Preferably, the oxygen-containing compound is oxygen (O2) or water (H2O). Oxygen can be provided as part of a gaseous composition such as air. In another embodiment, the oxygen is provided in a substantially purified form. In each embodiment, the oxygen is in the form of molecular oxygen. Water can be supplied as steam. The gaseous precursor mixture may also contain both oxygen and water.

[0041] Preferably the radical scavenger is a hydrocarbon gas. Preferred hydrocarbon gases are ethylene (C2H4) or propylene (C3H6). U.S. Patent No. 5,798,142, which is incorporated herein by reference in its entirety, describes the formation of a silica coating by combining a radical scavenger, silane, oxygen and a carrier gas to form a precursor gas mixture.

[0042] With precursor materials, inert gas can be used as the carrier and / or dilution gas. Suitable inert gases include nitrogen (N2), hydrogen (H2), helium (He) and mixtures thereof. In one embodiment, the precursor mixture contains one or more inert gases selected from the group consisting of N2, H2, He, and mixtures thereof.

[0043] Coating apparatus 10 suitable for use in the method is best illustrated in Figs. 2 and 3. Precursor materials flow into coating apparatus 10 through one or more inlets 47. One or more inlets are in fluid communication with conduit 49, which directs the precursor materials through the coating apparatus 10. The conduit 49 is in fluid communication with the outlet 54. The precursor materials are released from the coating apparatus 10 through the outlet 54.

[0044] The coating apparatus 10 may comprise a long axis 48 and may have a length L which is substantially equal, slightly smaller or slightly larger than the width of the glass substrate 12. Furthermore, as shown in the embodiment of figure 2, the apparatus for the coating 10 may have a substantially rectangular shape. However, it is worth noting that the method can be used with a coating apparatus having a configuration that differs

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EP2879999 from the above described, and further descriptions of coating apparatus suitable for the practical implementation of the method can be found in US Patent No. 4,922,853 and US Patent No. 9540277.

[0045] The temperature inside the coating apparatus 10 can be controlled. The temperature inside the coating apparatus 10 can be controlled by appropriate means. For example, the temperature inside the coating apparatus 10 can be controlled by using a suitable heat exchange medium in certain parts of the coating apparatus 10.

[0046] In some embodiments, the coating apparatus 10 may include one or more face portions 52. As shown in Figure 2, in one embodiment, the coating apparatus 10 includes two face surfaces 52. Precursor materials are released from the outlet 54, which separates the front parts 52 and is adjacent to them. Thus, precursor materials are released from the coating apparatus 10 between the head portions 52.

[0047] Each face part 52 includes a face 53. The face surfaces 53 are aligned with each other and arranged parallel to the glass substrate 12. The face parts 52 and outlet 54 have lengths that can be substantially equal. In one embodiment, the lengths of the front portions 52 and the outlet 54 are substantially equal to the lengths L of the coating apparatus 10.

[0048] Coating apparatus 10 includes one or more exhaust gas channels 56. As illustrated in Figure 3, coating apparatus 10 may include two exhaust gas channels 56. Exhaust gas channels 56 allow continuous removal of used or unused gaseous precursor materials and / or inert gases that could otherwise create unwanted contaminants on the deposition surface 14 of the glass substrate 12. Exhaust ducts 56 are separated from the outlet 54 with front parts 52 of the coating apparatus 10. In this embodiment, each exhaust gas channel 56 is disposed adjacent to the front 52.

[0049] Each exhaust gas channel 56 is at least partially defined by one or more side walls 58. Furthermore, each exhaust gas channel 56 includes an opening 60 that receives used or unused gaseous precursor materials and / or inert gases. In some embodiments, the aperture 60 has a length that is substantially equal to the length L of the coating apparatus 10. When the coating apparatus 10 is located in the deposition chamber 18 and above the glass substrate 12, the outlet 54 and the exhaust gas opening 60 are provided near the deposition surface 14 of the glass substrate 12.

[0050] At least one baffle 62 may be provided in each exhaust gas channel 56. At least one baffle 62 helps ensure that used or unused precursor materials and / or inert gases are removed homogeneously from the deposition chamber 18. At least one partition 62 may be configured as an elongated sheet and may be formed of corrosion resistant metal. At least one partition 62 is preferably attached to sidewall 58 and disposed substantially parallel to the long axis 48 of coating apparatus 10.

[0051] Preferably, the coating apparatus 10 is provided in the deposition chamber 18 at a predetermined distance above the glass substrate 12. As shown in Fig. 1, when the method is implemented in practice in combination with a method of making glass, the coating apparatus 10 can be provided in the flotation bath chamber. It is worth noting, however, that the coating apparatus 10 can be provided in another part of the flotation bath section 25, tunnel compressor 26 and / or in the space 42 between the flotation bath section 25 and tunnel compressor 26.

PAT-3489-EP-E

EP2879999 [0052] The fluorine-containing compound may at some point be a liquid or solid, but is volatile so that it can be vaporized before entering the coating apparatus 10. Preferably, the fluorine-containing compound is hydrogen fluoride (HF). More preferably, the hydrogen fluoride containing compound is anhydrous HF. However, it is worth noting that alternative fluorine-containing compounds can be used in practicing the method.

[0053] The method may include providing a source 80 of the fluorine-containing compound. The fluorine containing compound flows from its source 80 into the coating apparatus 10. In one embodiment, the method comprises introducing the fluorine containing compound at one or more locations in the coating apparatus 10. The fluorine containing compound is introduced into exhaust gas channel 56. More preferably, the fluorine-containing compound is introduced into separate exhaust gas channels. It is worth noting, however, that the fluorine-containing compound can be introduced into one or more locations in the coating apparatus.

[0054] For any particular combination of precursor materials, the optimal flow rate of the fluorine-containing compound to inhibit film formation and / or by-products on one or more parts of the coating apparatus 10 may vary. However, the flow rate of the fluorine-containing compound needed to inhibit the formation of the coating and / or by-products on one or more parts of the coating apparatus 10 may depend on the amount of silicon containing compound flowing into the coating apparatus 10. Thus, the method includes flow to the coating apparatus 10 selected the ratio of the fluorine containing compound to the silicon containing compound. The ratio of fluorine-containing compound to silicon-containing compound entering the coating apparatus is selected to be equal to or greater than 2: 1. More preferably, the ratio of the fluorine-containing compound to the silicon-containing compound entering the coating apparatus is selected to be approximately equal to or greater than 4: 1. Furthermore, the ratio of the fluorine containing compound to the flowing silicon containing compound to coating apparatus 10 can be chosen to be approximately equal to or greater than 5: 1.

[0055] In some embodiments, it may be desirable to flow the fluorine-containing compound into the coating apparatus 10 in a uniform manner. In such embodiments, and as shown in Fig. 3, a gas distribution tube 64 is disposed in the coating apparatus 10. Preferably, the fluorine-containing compound is directed through the gas distribution tube 64 before entering the coating apparatus 10. Because the fluorine-containing compound can be introduced into the coating apparatus 10 at one or more locations, multiple gas distribution pipes 64 can be provided in the coating apparatus 10. For example, as shown in Figure 3, the gas distribution pipe 64 can be provided at any exhaust gas channel 56.

[0056] Each gas distribution pipe 64 is preferably located adjacent to at least one partition 62. The gas distribution pipe 64 may be located above at least one partition 62 or, as shown in Figure 3, under at least one partition 62. Preferably, each the gas distribution pipe 64 is located parallel to the long axis 48 of the coating apparatus 10. Each gas distribution pipe 64 may be attached to the side wall 58 of the exhaust gas channel 56. As shown in Figure 4, a plurality of supports 66 are provided for securing gas distribution pipe 64 to sidewall 58 of exhaust gas channel 56. Supports 66 may be equally spaced apart along gas distribution pipe 64.

[0057] An embodiment of the gas distribution pipe 64 suitable for use in practicing the method is best illustrated in Figures 4 and 5. The gas distribution pipe 64 is preferably metal. Moreover, because the fluorine-containing compound and the environment inside and around the coating apparatus 10 can be corrosive,

PAT-3489-EP-E

EP2879999 is advantageous when the gas distribution pipe 64 is formed of a metal or corrosion resistant metal alloy. In an embodiment, the gas distribution pipe 64 comprises nickel.

[0058] The gas distribution pipe 64 comprises a cylindrical portion 68 that is hollow and has a plurality of equidistant holes 70 formed therein. Preferably, the cylindrical portion 68 has a closed end 72 and an open end 74 located on the opposite side. The gas distribution pipe 64 may have a long axis 76 whose length Lt is substantially equal to the length L of the coating apparatus 10. In an embodiment, the fluorine-containing compound flows into the open end 74 of the gas distribution pipe 64 and is introduced into the coating apparatus 10 through a plurality of holes 70 formed in the cylindrical portion 68.

[0059] Preferably, the fluorine-containing compound enters the coating apparatus 10 prior to forming the silica coating, i.e., before the precursor materials enter the coating apparatus 10, and has a flow rate that is substantially maintained during the formation of the silica coating. However, the fluorine-containing compound may initially flow into the coating apparatus 10 during the formation of the silica coating, i.e. while the precursor materials enter the coating apparatus 10, and has a flow rate that is substantially maintained during the continuous formation of the silica coating. Furthermore, the fluorine-containing compound can flow into the coating apparatus after the formation of the silica coating, i.e. when the silica precursor materials no longer flow into the coating apparatus 10, and may have a flow rate that removes the coating and / or by-products resulting from the deposition of the coating on one or more parts of the coating apparatus.

[0060] As indicated above, the fluorine-containing compound may flow into the coating apparatus 10 prior to forming the silica coating. In this embodiment, the fluorine-containing compound prevents the formation of a coating and / or by-products resulting from deposition of the coating on one or more parts of the coating apparatus 10. In other embodiments, where the fluorine-containing compound enters the coating apparatus 10 during or after the formation of the silica coating, the fluorine-containing compound removes and / or prevents further coating and / or by-products from forming on one or more parts of the coating apparatus 10.

[0061] The influx of a fluorine-containing compound into the coating apparatus 10 inhibits the formation of a coating and / or by-products resulting from the deposition of the coating on one or more parts of the coating apparatus 10, such as for example on one or more surfaces of the coating apparatus 10. In one embodiment, the coating and / or by-products are inhibited on a surface that at least partially defines the exhaust gas channel 56, such as, for example, one or more side walls 58. In another embodiment, the formation of the coating and / or by-products is inhibited on surface in the exhaust gas channel 56, such as for example on the surface of at least one partition 62. However, the method is not limited to inhibiting the formation of coating and / or by-products on surfaces that are within or define exhaust gas channels 56. Thus, in some embodiments, the formation of the coating and / or by-products is inhibited on at least one face 53 of the coating apparatus 10.

Examples [0062] A coating apparatus having a longer axis was placed transversely above the glass ribbon in a flotation bath chamber and used to form a silica coating thereon. A non-oxidizing atmosphere of a mixture of nitrogen and hydrogen was maintained in the flotation bath chamber. The pressure in the flotation bath chamber was maintained at

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EP2879999 essentially atmospheric pressure level. The approximate glass web temperature and temperature inside the coating apparatus of Examples 1-5 are given in Table 1 below.

[0063] To form the silica coating, gaseous precursor materials were mixed and introduced into the coating apparatus. The gas mixture of precursor materials contained S1H4, O2, C2H4. The gaseous mixture also contained N2 as the diluent. The SiH4 flow rate to the coating apparatus for Examples 1-5 is given below.

[0064] The coating apparatus had two exhaust gas channels and essentially all of the used / unused precursor materials were exhaled from the flotation bath chamber through the exhaust gas channels. A gas distribution pipe was provided in each exhaust gas channel so as to extend parallel to the long axis of the coating apparatus. Each gas distribution pipe contained a hollow cylindrical portion and had equidistant holes formed therein.

[0065] Prior to the formation of the silica coating, it flowed into the coating apparatus and was introduced into each exhaust gas channel through gas distribution pipes, a gas mixture of anhydrous HF and N2. The flow of the HF and N2 mixture was partitioned between the gas distribution pipes and directed to them before introducing the HF / N2 gas mixture into the exhaust gas channels. The total HF and N2 flow rates for Examples 1-5 are given below. The flow of the HF / N2 mixture was maintained during the formation of the silica coating.

Table 1: EXPERIMENTAL CONDITIONS FOR EXAMPLES 1-5

<td>Example</td><td>SiH4 flow rate (slm)</td><td>HF flow rate (slm)</td><td>Flow rate N2 (slm)</td><td>Pressure (Atm)</td><td>Temp. coating apparatus (° F)</td><td>Temp. glass strips (° F)</td>

<td> 1</td><td> 1,6</td><td> 20</td><td> 10</td><td> 1</td><td> 350</td><td> ~1200 -</td>

<td> 2</td><td> 1,6</td><td> 10</td><td> 10</td><td> 1</td><td> 350</td><td> ~1200 -</td>

<td> 3</td><td> 1,6</td><td> 8</td><td> 10</td><td> 1</td><td> 350</td><td> ~1200 -</td>

<td> 4</td><td> 1,6</td><td> 6</td><td> 10</td><td> 1</td><td> 350</td><td> ~1200 -</td>

<td> 5</td><td> 1,6</td><td> 4</td><td> 10</td><td> 1</td><td> 350</td><td> ~1200 -</td>

[0066] As observed under the conditions given for Examples 1-5 and as will be described below, the flow of a fluorine-containing compound, such as HF, to a coating apparatus when depositing a silica coating on a glass substrate inhibits the formation of the coating and / or by-products on one or more more parts of the coating apparatus. Furthermore, the silica coating formed on the glass substrate does not contain fluorine or contains only trace amounts thereof.

[0067] In the conditions of Examples 1-3, the inhibition of coating and / or by-products on the surfaces defining the exhaust channels was excellent. Under the conditions of Example 4, inhibition of coating and / or by-products on the aforesaid surfaces was sufficient, but not as good as observed under the conditions given in Examples 1-3. Under the conditions of Example 5, inhibition of coating and / or by-products on the surfaces defining the exhaust gas channels was not as good as observed under the conditions of Example 4.

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EP2879999