Process for depositing a coating

Abstract

A process for manufacturing a coated glass article, said process comprising the following steps in order: providing a glass substrate having a surface, forming a gaseous mixture comprising a source of tin, a source of fluorine, molecular oxygen and water, delivering the gaseous mixture to the surface of the glass substrate, and depositing a coating based on fluorine-doped tin oxide on the surface of the substrate, wherein the coating based on fluorine-doped tin oxide comprises two or more layers based on fluorine-doped tin oxide, wherein the process is carried out using chemical vapour deposition (CVD), and wherein the molar ratio of the source of fluorine in the gaseous mixture during deposition of the layer based on fluorine-doped tin oxide that is directly beneath the outermost layer based on fluorine-doped tin oxide : the source of fluorine in the gaseous mixture during deposition of the outermost layer based on fluorine-doped tin oxide is from 0.01 to 1.5.

Description

[0001] Process For Depositing A Coating

[0002] This invention relates to a process for manufacturing a coated glass article.

[0003] Coatings on substrate surfaces find uses in many fields. Some of the more useful coatings are transparent conductive oxides or TCOs, for example, fluorine-doped tin oxide, which may be used as low emissivity coatings as well as in sensors, digital displays, smart window coatings, catalyst supports, and electrode substrates for electronic devices.

[0004] Methods used to deposit metal oxide coatings include physical vapour deposition methods, such as sputtering, or liquid based methods, such as sol-gel using spincoating or dip-coating techniques, among others. One particularly useful method for deposition of coatings is chemical vapour deposition (CVD) wherein a fluid precursor in the form of a vapour is delivered to the surface of the substrate where the precursors react and / or decompose thereby depositing a coating. Different subsets of CVD include metal organic (MO) CVD, combustion (C) CVD, plasma enhanced (PE) CVD and aerosol-assisted (AA) CVD.

[0005] It would be desirable to influence the electrical properties of tin oxide coatings deposited on glass, in order to afford the tin oxide, and / or an overlying material, a particular functionality. In particular it would be advantageous to afford improved electrical properties while maintaining optical properties such as transmission.

[0006] According to a first aspect of the present invention there is provided a process for manufacturing a coated glass article, said process comprising the following steps in order: providing a glass substrate having a surface, forming a gaseous mixture comprising a source of tin, a source of fluorine, molecular oxygen and water, delivering the gaseous mixture to the surface of the glass substrate, and depositing a coating based on fluorine-doped tin oxide on the surface of the substrate, wherein the coating based on fluorine-doped tin oxide comprises two or more layers based on fluorine-doped tin oxide, wherein the process is carried out using chemical vapour deposition (CVD), and wherein the molar ratio of the source of fluorine in the gaseous mixture during deposition of the layer based on fluorine-doped tin oxide that is directly beneath the outermost layer based on fluorine-doped tin oxide : the source of fluorine in the gaseous mixture during deposition of the outermost layer based on fluorine-doped tin oxide is from 0.01 to 1.5.

[0007] The inventors have surprisingly found that the use of this process enables the deposition of a coating of fluorine-doped tin oxide with desirable electrical properties, in particular a tuneable electron mobility for a given sheet resistance, while retaining acceptable optical performance.

[0008] In the context of the present invention, where a coating or layer is said to be “based on” a particular material or materials, this means that the coating or layer predominantly consists of the corresponding said material or materials, which means typically that it comprises at least about 50 at.% of said material or materials.

[0009] In the following discussion of the invention, unless stated to the contrary, the disclosure of alternative values for the upper or lower limit of the permitted range of a parameter, coupled with an indication that one of said values is more highly preferred than the other, is to be construed as an implied statement that each intermediate value of said parameter, lying between the more preferred and the less preferred of said alternatives, is itself preferred to said less preferred value and also to each value lying between said less preferred value and said intermediate value.

[0010] Throughout this specification, the term “comprising” or “comprises” means including the component(s) specified but not to the exclusion of the presence of other components. The term “consisting essentially of” or “consists essentially of” means including the components specified but excluding other components except for materials present as impurities, unavoidable materials present as a result of processes used to provide the components, and components added for a purpose other than achieving the technical effect of the invention. Typically, when referring to compositions, a composition consisting essentially of a set of components will comprise less than 5% by weight, typically less than 3% by weight, more typically less than 1% by weight of non-specified components.

[0011] The term “consisting of” or “consists of” means including the components specified but excluding other components.

[0012] Whenever appropriate, depending upon the context, the use of the term “comprises” or “comprising” may also be taken to include the meaning “consists essentially of” or “consisting essentially of”, and also may also be taken to include the meaning “consists of’ or “consisting of”.

[0013] References herein such as “in the range x to y” are meant to include the interpretation “from x to y” and so include the values x and y.

[0014] In the context of the present invention a transparent material or a transparent substrate is a material or a substrate that is capable of transmitting visible light so that objects or images situated beyond or behind said material can be distinctly seen through said material or substrate.

[0015] In the context of the present invention the “thickness” of a coating or layer is, for any given location at a surface of the coating or layer, represented by the distance through the coating or layer, in the direction of the smallest dimension of the coating or layer, from said location at a surface of the coating or layer to a location at an opposing surface of said coating or layer.

[0016] In the context of the present invention a “derivative” is a chemical substance related structurally to another chemical substance and theoretically derivable from it.

[0017] In the context of the present invention “room temperature” means 20°C.

[0018] The molar % of a substance in the gaseous mixture is defined as: (the number of moles of said substance in the gaseous mixture I the total number of moles in the gaseous mixture) x 100%.

[0019] Preferably the source of tin is selected from one or more of dimethyltin dichloride, diethyltin dichloride, dibutyltin diacetate, tetra methyl tin, methyltin trichloride, triethyltin chloride, trimethyltin chloride, ethyltin trichloride, propyltin trichloride, isopropyltin trichloride, sec-butyltin trichloride, t-butyltin trichloride, phenyltin trichloride, and carbethoxyethyltin trichloride. Preferably the source of tin is dimethyltin dichloride.

[0020] Preferably the source of fluorine is selected from one or more of R4NF, wherein R is H or Ci to C4 alkyl (e.g. t-butyl, propyl, ethyl, methyl); HF or acetyl fluoride. Preferably the source of fluorine is HF. Preferably the molar ratio of the source of fluorine in the gaseous mixture during deposition of the layer based on fluorine-doped tin oxide that is directly beneath the outermost layer based on fluorine-doped tin oxide : the source of fluorine in the gaseous mixture during deposition of the outermost layer based on fluorine-doped tin oxide is from 0.1 to 1.2, more preferably from 0.3 to 1.1 , even more preferably from 0.3 to 1 , even more preferably from 0.4 to 1 , most preferably from 0.5 to 1 .

[0021] In some preferred embodiments the molar ratio of the source of fluorine in the gaseous mixture during deposition of the layer based on fluorine-doped tin oxide that is directly beneath the outermost layer based on fluorine-doped tin oxide : the source of fluorine in the gaseous mixture during deposition of the outermost layer based on fluorine-doped tin oxide is from 0.1 to 0.3, alternatively from 0.3 to 0.5, alternatively from 0.5 to 0.7, alternatively from 0.7 to 0.9, alternatively from 0.9 to 1.1.

[0022] Preferably, during deposition of the outermost layer based on fluorine-doped tin oxide, the gaseous mixture has a molar % of the source of fluorine of from 0.3 to 5%, more preferably from 0.7 to 2.5%, even more preferably from 1 to 2%, most preferably from 1.2 to 1.9%.

[0023] Preferably, during deposition of the layer based on fluorine-doped tin oxide that is directly beneath the outermost layer based on fluorine-doped tin oxide, the gaseous mixture has a molar % of the source of fluorine of from 0.1 to 3%, more preferably from 0.1 to 2%, even more preferably from 0.5 to 1.5%, most preferably from 0.8 to 1.4%.

[0024] Preferably, the gaseous mixture has a molar % of water of from 5 to 65%, more preferably from 20 to 50%, even more preferably from 30 to 40%, most preferably from 34 to 38%.

[0025] Preferably, the gaseous mixture has a molar % of molecular oxygen of from 10 to 70%, more preferably from 25 to 55%, even more preferably from 35 to 45%, most preferably from 40 to 44%.

[0026] Preferably, the gaseous mixture has a molar % of the source of tin of from 0.1 to 10%, more preferably from 0.5 to 5%, even more preferably from 1 to 4%, most preferably from 2 to 3%. Preferably the gaseous mixture has a molar ratio of the source of tin : the source of fluorine of from 1 :1.5 to 10:1 , more preferably from 1 :1 to 7:1 , even more preferably from 1.3:1 to 5:1 , most preferably from 1.4:1 to 3:1.

[0027] Preferably, during deposition of the outermost layer based on fluorine-doped tin oxide, the gaseous mixture has a molar ratio of the source of tin : the source of fluorine of from 1 :1.5 to 7:1 , more preferably from 1 :1 to 4:1 , even more preferably from 1.2:1 to 3:1 , most preferably from 1 .4: 1 to 2: 1 .

[0028] Preferably, during deposition of the layer based on fluorine-doped tin oxide that is directly beneath the outermost layer based on fluorine-doped tin oxide, the gaseous mixture has a molar ratio of the source of tin : the source of fluorine of from 1 :1.2 to 10:1 , more preferably from 1.1 :1 to 5:1 , even more preferably from 1.5:1 to 4:1 , most preferably from 1.9:1 to 3:1.

[0029] Preferably, for the coating based on fluorine-doped tin oxide, the fluorine-doped tin oxide is SnO2:F. Preferably the coating based on fluorine-doped tin oxide consists essentially of, more preferably consists of, fluorine-doped tin oxide, preferably SnO2:F.

[0030] Preferably, the coating based on fluorine-doped tin oxide exhibits a sheet resistance of at most 50 ohm / sq, more preferably at most 40 ohm / sq, even more preferably at most 30 ohm / sq, most preferably at most 25 ohm / sq, but preferably at least 5 ohm / sq, more preferably at least 10 ohm / sq, even more preferably at least 15 ohm / sq. Preferably, the coating based on fluorine-doped tin oxide exhibits a sheet resistance of from 15 ohm / sq to 30 ohm / sq, more preferably from 17.5 ohm / sq to 21.5 ohm / sq. The sheet resistance exhibited by the coating based on fluorine-doped tin oxide can be measured using a 4- point probe method and a commercially available 4-point probe.

[0031] Preferably, the coating based on fluorine-doped tin oxide has a room temperature electron mobility of at least 10 cm2 / Vs, more preferably at least 20 cm2 / Vs, even more preferably at least 25 cm2 / Vs, most preferably at least 30 cm2 / Vs, but preferably at most 200 cm2 / Vs, more preferably at most 100 cm2 / Vs, even more preferably at most 50 cm2 / Vs, most preferably at most 40 cm2 / Vs.

[0032] In embodiments where the coating based on fluorine-doped tin oxide includes one or more layers based on fluorine-doped tin oxide in addition to the outermost layer based on fluorine-doped tin oxide and the layer based on fluorine-doped tin oxide that is directly beneath the outermost layer based on fluorine-doped tin oxide, the one or more additional layers based on fluorine-doped tin oxide are deposited between the glass substrate and the aforementioned two layers based on fluorine-doped tin oxide.

[0033] Preferably, the coating based on fluorine-doped tin oxide comprises at least 0.2 atomic% fluorine, more preferably at least 0.4 atomic% fluorine, even more preferably at least 0.6 atomic% fluorine, most preferably at least 0.8 atomic% fluorine, but preferably at most 5 atomic% fluorine, more preferably at most 2 atomic% fluorine, even more preferably at most 1.5 atomic% fluorine, most preferably at most 1.2 atomic% fluorine.

[0034] The coating based on fluorine-doped tin oxide can be deposited directly on the surface of the substrate. Alternatively, said coating based on fluorine-doped tin oxide may be deposited indirectly on the surface of the substrate i.e. said coating based on fluorine- doped tin oxide may be deposited over one or more previously deposited layers. For example, said coating based on fluorine-doped tin oxide may be deposited over and contact a layer based on silica. In some embodiments said coating based on fluorine- doped tin oxide may be deposited over and contact a layer based on silica, and wherein said layer based on silica contacts a subjacent layer based on a metal oxide, e.g. tin oxide.

[0035] Preferably the coating based on fluorine-doped tin oxide has a thickness of at least 200 nm, more preferably at least 220 nm, even more preferably at least 230 nm, most preferably at least 240 nm, but preferably at most 300 nm, more preferably at most 290 nm, even more preferably at most 280 nm, most preferably at most 270 nm. Preferably the coating based on fluorine-doped tin oxide has a thickness of from 200 to 300 nm, more preferably from 240 to 280 nm. Preferably each of the layers based on fluorine- doped tin oxide has a thickness of from 60 to 200 nm, more preferably of from 90 to 160 nm, more preferably of from 100 to 150 nm. Preferably the thickness of the outermost layer based on fluorine-doped tin oxide is between 25% and 70% of the thickness of the coating based on fluorine-doped tin oxide. Preferably the thickness of the layer based on fluorine-doped tin oxide that is directly beneath the outermost layer based on fluorine-doped tin oxide is between 25% and 70% of the thickness of the coating based on fluorine-doped tin oxide. In an embodiment, the coating based on fluorine-doped tin oxide is pyrolytic. As used herein, the term “pyrolytic” may refer to the coating or a layer thereof being chemically bonded to the glass substrate or another layer.

[0036] Preferably said surface of the substrate is a major surface of the substrate. Preferably the substrate is transparent. Preferably the substrate is a transparent glass substrate. The transparent glass substrate may be a clear metal oxide-based glass pane. Preferably the glass pane is a clear float glass pane, preferably a low iron float glass pane. By clear float glass, it is meant a glass having a composition as defined in BS EN 572-1 and BS EN 572-2 (2004). For clear float glass, the Fe2Os level by weight is typically 0.11%. Float glass with an Fe2Os content less than about 0.05% by weight is typically referred to as low iron float glass. Such glass usually has the same basic composition of the other component oxides i.e. low iron float glass is also a soda-lime- silicate glass, as is clear float glass. Typically low iron float glass has less than 0.02% by weight Fe2Os. Alternatively the glass pane is a borosilicate-based glass pane, an alkali-aluminosilicate-based glass pane, or an aluminium oxide-based crystal glass pane.

[0037] The CVD may be carried out in conjunction with the manufacture of the substrate, preferably a transparent glass substrate. In an embodiment, the transparent glass substrate may be formed utilizing the well-known float glass manufacturing process. Preferably the process is carried out in conjunction with the manufacture of the substrate via the float glass process. In this embodiment, the transparent glass substrate may also be referred to as a float glass ribbon. Conveniently the CVD may be carried out either in the float bath, in the lehr or in the lehr gap. The preferred method of CVD is atmospheric pressure CVD (e.g. online CVD as performed during the float glass process). However, it should be appreciated that the CVD process can be utilised apart from the float glass manufacturing process or well after formation and cutting of the glass ribbon.

[0038] Preferably, the formation of the gaseous mixture comprises heating the source of tin and / or any further precursor compound. Precursor compounds may at some point be a liquid or a solid but may be volatile such that they can be vaporised or sublimed for use in a gaseous mixture. Once in a gaseous state, precursor compounds can be included in a gaseous stream and utilized in the CVD process. Preferably the formation of the gaseous mixture comprises heating the source of tin, the source of fluorine and / or any further precursor compound using a thin film evaporator system. Thin film evaporator systems are particularly suited to production scale processes.

[0039] When a thin film evaporator system is used, preferably the source of tin is heated to a temperature of at least 110°C, more preferably at least 140°C, even more preferably at least 150°C, most preferably at least 155°C, but preferably at most 210°C, more preferably at most 180°C, even more preferably at most 170°C, most preferably at most 165°C. Again, these preferred ranges are beneficial in terms of controlling the deposition of the coating based on fluorine-doped tin oxide.

[0040] The gaseous mixture may further comprise one or more carrier gas or diluents, for example, nitrogen and / or helium, preferably nitrogen. Thus, the process may further comprise providing a source of the one or more carrier gas or diluents from which separate supply lines may extend.

[0041] Preferably, the gaseous mixture is delivered to a coating apparatus. In certain embodiments, the gaseous mixture is fed through a coating apparatus and discharged from the coating apparatus utilizing one or more gas distributor beams prior to deposition of the coating based on fluorine-doped tin oxide. Preferably, the gaseous mixture is formed prior to being fed through the coating apparatus. For example, the source of tin, source of fluorine, molecular oxygen, water and preferably a carrier gas or diluent such as nitrogen, may be mixed in a feed line connected to an inlet of the coating apparatus. In other embodiments, the gaseous mixture may be formed within the coating apparatus.

[0042] The gaseous mixture may be directed toward and along the substrate. Utilising a coating apparatus aids in directing the gaseous mixture toward and along the substrate. Preferably, the gaseous mixture is directed toward and along the substrate in a laminar flow.

[0043] Preferably, the coating apparatus extends transversely across the substrate and is provided at a predetermined distance thereabove. The coating apparatus is preferably located at, at least, one predetermined location. When the process is utilised in conjunction with the float glass manufacturing process, the coating apparatus is preferably provided within the float bath section thereof. However, the coating apparatus may be provided in the annealing lehr, and / or in the gap between the float bath and the annealing lehr.

[0044] It is desirable that the gaseous mixture be kept at a temperature below the thermal decomposition temperature of the source of tin and any further precursor compound to prevent pre-reaction before the mixture reaches the surface of the substrate. Within the coating apparatus, the gaseous mixture is preferably maintained at a temperature below that at which it reacts and is delivered to a location near the surface of the substrate, the substrate being at a temperature above the reaction temperature. The gaseous mixture may react at or near the surface of the substrate to deposit the coating based on fluorine-doped tin oxide on said surface.

[0045] The process may preferably be carried out when the glass substrate, preferably a transparent glass substrate, is at a temperature in the range 450°C to 800°C, more preferably when the transparent glass substrate is at a temperature in the range 550°C to 750°C. Depositing a coating by CVD when the substrate is at these preferred temperatures affords greater crystallinity of the coating, which can improve toughenability (resistance to heat treatment).

[0046] The process may be a dynamic process in which the substrate is moving at the time of deposition. Preferably, during deposition the substrate moves at a predetermined rate of, for example, greater than 3m / min, more preferably between 3m / min and 20 m / min.

[0047] As detailed above, preferably the process is carried out during the float glass production process at substantially atmospheric pressure. Alternatively the CVD may be carried out using low-pressure CVD or ultrahigh vacuum CVD. The CVD may be carried out using aerosol assisted CVD or direct liquid injection CVD. Furthermore, the CVD may be carried out using microwave plasma-assisted CVD, plasma-enhanced CVD, remote plasma-enhanced CVD, atomic layer CVD, combustion CVD (flame pyrolysis), hot wire CVD, metalorganic CVD, rapid thermal CVD, vapour phase epitaxy, or photo-initiated CVD. The glass substrate will usually be cut into sheets after deposition of any CVD layer(s) for storage or convenient transport.

[0048] Where the substrate is a float glass substrate, preferably said surface of the substrate is the gas side surface. Coated glass manufacturers usually prefer depositing coatings on the gas side surface (as opposed to the tin side surface for float glass) because deposition on the gas side surface can improve the properties of the coating. Preferably the coating based on fluorine-doped tin oxide is deposited at a deposition rate of at least 2.5 nm per second (nm / sec), more preferably at least 5.0 nm / sec, even more preferably at least 10.0 nm / sec or more, but preferably at most 60 nm / sec, more preferably at most 50 nm / sec, even more preferably at most 40 nm / sec. In certain embodiments, said coating is deposited at a dynamic deposition rate of 280 nm x m / min or more. Preferably the process further comprises, following deposition of the coating based on fluorine-doped tin oxide, exposing the substrate to an environment that is under a vacuum and is at a temperature of from 450°C to 750°C.

[0049] Preferably the environment is at a temperature of from 500°C to 700°C, more preferably from 550°C to 650°C, even more preferably from 575°C to 625°C, most preferably from 590°C to 610°C.

[0050] Preferably the environment is under a vacuum of less than 101.325 kPa, more preferably less than 100.5 kPa, even more preferably less than 95 kPa, but preferably more than 0.1 kPa, more preferably more than 1 kPa, even more preferably more than 50 kPa.

[0051] Preferably the substrate is exposed to the environment for at least 5 minutes, more preferably for at least 7 minutes, even more preferably at least 10 minutes, even more preferably at least 13 minutes, but preferably at most 1 hour, more preferably at most 30 minutes, even more preferably at most 20 minutes.

[0052] According to a third aspect of the present invention there is provided use of the coated glass article of the present invention in architectural, automotive or electronic device applications.

[0053] Any invention described herein may be combined with any feature of any other invention described herein mutatis mutandis.

[0054] It will be appreciated that optional features applicable to one aspect of the invention can be used in any combination, and in any number. Moreover, they can also be used with any of the other aspects of the invention in any combination and in any number. This includes, but is not limited to, the dependent claims from any claim being used as dependent claims for any other claim in the claims of this application. The reader’s attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

[0055] All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive.

[0056] Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0057] The invention will now be further described by way of the following specific embodiments, which are given by way of illustration and not of limitation, with reference to the accompanying drawings in which:

[0058] Fig. 1 is a schematic view, in cross-section, of a coated glass article produced in accordance with certain embodiments of the present invention;

[0059] Fig. 2 is a schematic view, in vertical section, of an installation for practicing the float glass process which incorporates several CVD apparatuses for carrying out the process in accordance with certain embodiments of the present invention; and

[0060] Fig. 3 is a graph of electron mobility and electron concentration vs HF ratio for several examples according to the present invention.

[0061] Figure 1 shows a cross-section of a coated glass article 1 according to certain embodiments of the present invention. Coated glass article 1 comprises a transparent float glass substrate 2 that has been sequentially coated using CVD with a layer based on SnC>23, a layer based on SiC>24, a layer based on fluorine doped tin oxide (SnO2:F) 5, a second layer based on fluorine doped tin oxide (SnO2:F) 6 and a second layer based on SnC>2 7.

[0062] As discussed above, the process of the present invention may be carried out using CVD in conjunction with the manufacture of the glass substrate in the float glass process. The float glass process is typically carried out utilizing a float glass installation such as the installation 10 depicted in Figure 2. However, it should be understood that the float glass installation 10 described herein is only illustrative of such installations.

[0063] As illustrated in Figure 2, the float glass installation 10 may comprise a canal section

[0064] 20 along which molten glass 19 is delivered from a melting furnace, to a float bath section 11 wherein the glass substrate is formed. In this embodiment, the glass substrate will be referred to as a glass ribbon 8. However, it should be appreciated that the glass substrate is not limited to being a glass ribbon. The glass ribbon 8 advances from the bath section 11 through an adjacent annealing lehr 12 and a cooling section 13. The float bath section 11 includes: a bottom section 14 within which a bath of molten tin 15 is contained, a roof 16, opposite side walls (not depicted) and end walls 17. The roof 16, side walls and end walls 17 together define an enclosure 18 in which a nonoxidizing atmosphere is maintained to prevent oxidation of the molten tin 15.

[0065] In operation, the molten glass 19 flows along the canal 20 beneath a regulating tweel

[0066] 21 and downwardly onto the surface of the tin bath 15 in controlled amounts. On the molten tin surface, the molten glass 19 spreads laterally under the influence of gravity and surface tension, as well as certain mechanical influences, and it is advanced across the tin bath 15 to form the glass ribbon 8. The glass ribbon 8 is removed from the bath section 11 over lift out rolls 22 and is thereafter conveyed through the annealing lehr 12 and the cooling section 13 on aligned rolls. The deposition of coatings preferably takes place in the float bath section 11 , although it may be possible for deposition to take place further along the glass production line, for example, in the gap 28 between the float bath 11 and the annealing lehr 12, or in the annealing lehr 12.

[0067] As illustrated in Figure 2, four CVD apparatuses 9, 9A, 9B, 9C are shown within the float bath section 11. Thus, depending on the frequency and thickness of the coating layers required it may be desirable to use some or all of the CVD apparatuses 9, 9A, 9B, 9C. One or more additional coating apparatuses (not depicted) may be provided. One or more CVD apparatus may alternatively or additionally be located in the lehr gap 28. Any by-products are removed through coater extraction slots and then through a pollution control plant. For example, in an embodiment, a tin oxide layer is formed using CVD apparatus 9A, a silica layer is formed using CVD apparatus 9, a fluorine doped tin oxide layer is formed utilizing CVD apparatus 9B, apparatus 9C is utilized to form a second fluorine-doped tin oxide layer and an additional coating apparatus is used to form a second tin oxide layer. A suitable non-oxidizing atmosphere, generally nitrogen or a mixture of nitrogen and hydrogen in which nitrogen predominates, may be maintained in the float bath section 11 to prevent oxidation of the molten tin 15 comprising the float bath. The atmosphere gas is admitted through conduits 23 operably coupled to a distribution manifold 24. The non-oxidizing gas is introduced at a rate sufficient to compensate for normal losses and maintain a slight positive pressure, on the order of between about 0.001 and about 0.01 atmosphere above ambient atmospheric pressure, so as to prevent infiltration of outside atmosphere. For the purposes of describing the invention, the above-noted pressure range is considered to constitute normal atmospheric pressure.

[0068] CVD is generally performed at essentially atmospheric pressure. Thus, the pressure of the float bath section 11 , annealing lehr 12, and / or in the gap 28 between the float bath

[0069] 11 and the annealing lehr 12 may be essentially atmospheric pressure. Heat for maintaining the desired temperature regime in the float bath section 11 and the enclosure 18 is provided by radiant heaters 25 within the enclosure 18. The atmosphere within the lehr 12 is typically atmospheric air, as the cooling section 13 is not enclosed and the glass ribbon 8 is therefore open to the ambient atmosphere. The glass ribbon 8 is subsequently allowed to cool to ambient temperature. To cool the glass ribbon 8, ambient air may be directed against the glass ribbon 8 by fans 26 in the cooling section 13. Heaters (not shown) may also be provided within the annealing lehr

[0070] 12 for causing the temperature of the glass ribbon 8 to be gradually reduced in accordance with a predetermined regime as it is conveyed therethrough.

[0071] Examples

[0072] Examples 1-3 according to the invention were prepared using atmospheric pressure CVD as part of the float glass process. The transparent glass substrate used for each Example was clear soda-lime-silica glass with a thickness of 4 mm.

[0073] The SnC>2 layers were deposited over the glass surface using the following components:

[0074] • N2 carrier gas, O2, and dimethyltin dichloride,

[0075] The SiC>2 layers were deposited over the glass surface using the following components:

[0076] • N2 carrier gas, He carrier gas, O2, C2H4, and SiH4.

[0077] The SnC>2:F layers were deposited over the glass surface using the following components:

[0078] • N2 carrier gas, O2, dimethyltin dichloride, HF, and H2O. For the deposition of the SnO2:F layers, the gaseous mixture comprised 37-47 mol% of O2, 31-41 mol% of H2O, 2.62 mol% of dimethyltin dichloride, 0.9-1.8 mol% of HF, with the remainder being N2 carrier gas.

[0079] The layer sequences of the samples were as follows:

[0080] Examples 1-3: Glass I SnC>21 SiC>21 SnO2:F I SnO2:F I SnC>2

[0081] The thicknesses of the individual layers of the samples were as follows:

[0082] Examples 1-3: Glass I SnO2 (20 - 40nm) I SiO2 (20 - 30nm) I SnO2:F (x2) + SnO2 (300 to 400nm for these 3 layers combined)

[0083] The electrical properties were determined using a commercially available Hall effect sensor and are shown below in Table 1 . The room temperature electron mobility cited in Table 1 in each case represents an average electron mobility over the entire SnO2:F coating comprised of two SnO2:F layers. The HF ratio referred to in Table 1 is the molar ratio of HF in the gaseous mixture during deposition of the fluorine-doped tin oxide layer that is directly beneath the outermost fluorine-doped tin oxide layer : HF in the gaseous mixture during deposition of the outermost fluorine-doped tin oxide layer.

[0084] As can be seen from Table 1 and Figure 3, for a given sheet resistance, by lowering the HF ratio an increased electron mobility is achieved. Conversely, raising the HF ratio results in an increased electron concentration. Different applications of coated glass articles may require different electrical properties and the present invention enables such properties to be fine-tuned to suit particular requirements.

[0085] The invention is not restricted to the details of the foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

CLAIMS1 . A process for manufacturing a coated glass article, said process comprising the following steps in order: providing a glass substrate having a surface, forming a gaseous mixture comprising a source of tin, a source of fluorine, molecular oxygen and water, delivering the gaseous mixture to the surface of the glass substrate, and depositing a coating based on fluorine-doped tin oxide on the surface of the substrate, wherein the coating based on fluorine-doped tin oxide comprises two or more layers based on fluorine-doped tin oxide, wherein the process is carried out using chemical vapour deposition (CVD), and wherein the molar ratio of the source of fluorine in the gaseous mixture during deposition of the layer based on fluorine-doped tin oxide that is directly beneath the outermost layer based on fluorine-doped tin oxide : the source of fluorine in the gaseous mixture during deposition of the outermost layer based on fluorine-doped tin oxide is from 0.01 to 1.5.

2. The process according to claim 1 , wherein the source of tin is selected from one or more of dimethyltin dichloride, diethyltin dichloride, dibutyltin diacetate, tetra methyl tin, methyltin trichloride, triethyltin chloride, trimethyltin chloride, ethyltin trichloride, propyltin trichloride, isopropyltin trichloride, sec-butyltin trichloride, t-butyltin trichloride, phenyltin trichloride, and carbethoxyethyltin trichloride, preferably the source of tin is dimethyltin dichloride.

3. The process according to any preceding claim, wherein the source of fluorine is selected from one or more of R4NF, wherein R is H or Ci to C4 alkyl (e.g. t-butyl, propyl, ethyl, methyl); HF or acetyl fluoride, preferably the source of fluorine is HF.

4. The process according to any preceding claim, wherein the molar ratio of the source of fluorine in the gaseous mixture during deposition of the layer based on fluorine-doped tin oxide that is directly beneath the outermost layer based on fluorine- doped tin oxide : the source of fluorine in the gaseous mixture during deposition of the outermost layer based on fluorine-doped tin oxide is from 0.1 to 1 .2, preferably from 0.3 to 1.1 , more preferably from 0.3 to 1 , even more preferably from 0.4 to 1 , most preferably from 0.5 to 1 .

5. The process according to any preceding claim, wherein the molar ratio of the source of fluorine in the gaseous mixture during deposition of the layer based on fluorine-doped tin oxide that is directly beneath the outermost layer based on fluorinedoped tin oxide : the source of fluorine in the gaseous mixture during deposition of the outermost layer based on fluorine-doped tin oxide is from 0.1 to 0.3.

6. The process according to any of claims 1 to 4, wherein the molar ratio of the source of fluorine in the gaseous mixture during deposition of the layer based on fluorine-doped tin oxide that is directly beneath the outermost layer based on fluorine- doped tin oxide : the source of fluorine in the gaseous mixture during deposition of the outermost layer based on fluorine-doped tin oxide is from 0.3 to 0.5.

7. The process according to any of claims 1 to 4, wherein the molar ratio of the source of fluorine in the gaseous mixture during deposition of the layer based on fluorine-doped tin oxide that is directly beneath the outermost layer based on fluorine- doped tin oxide : the source of fluorine in the gaseous mixture during deposition of the outermost layer based on fluorine-doped tin oxide is from 0.5 to 0.7.

8. The process according to any of claims 1 to 4, wherein the molar ratio of the source of fluorine in the gaseous mixture during deposition of the layer based on fluorine-doped tin oxide that is directly beneath the outermost layer based on fluorine- doped tin oxide : the source of fluorine in the gaseous mixture during deposition of the outermost layer based on fluorine-doped tin oxide is from 0.7 to 0.9.

9. The process according to any of claims 1 to 4, wherein the molar ratio of the source of fluorine in the gaseous mixture during deposition of the layer based on fluorine-doped tin oxide that is directly beneath the outermost layer based on fluorine- doped tin oxide : the source of fluorine in the gaseous mixture during deposition of the outermost layer based on fluorine-doped tin oxide is from 0.9 to 1.1.

10. The process according to any preceding claim, wherein, during deposition of the outermost layer based on fluorine-doped tin oxide, the gaseous mixture has a molar % of the source of fluorine of from 0.5 to 5%, preferably from 0.7 to 2.5%, more preferably from 1 to 2%, most preferably from 1.2 to 1.9%.11 . The process according to any preceding claim, wherein, during deposition of the layer based on fluorine-doped tin oxide that is directly beneath the outermost layerbased on fluorine-doped tin oxide, the gaseous mixture has a molar % of the source of fluorine of from 0.1 to 3%, preferably from 0.1 to 2%, even more preferably from 0.5 to 1 .5%, most preferably from 0.8 to 1 .4%.

12. The process according to any preceding claim, wherein the gaseous mixture has a molar ratio of the source of tin : the source of fluorine of from 1 :1.5 to 10:1 , more preferably from 1 :1 to 7:1 , even more preferably from 1.3:1 to 5:1 , most preferably from 1.4:1 to 3:1.

13. The process according to any preceding claim, wherein, during deposition of the outermost layer based on fluorine-doped tin oxide, the gaseous mixture has a molar ratio of the source of tin : the source of fluorine of from 1 :1.5 to 7:1 , more preferably from 1 :1 to 4: 1 , even more preferably from 1.2: 1 to 3: 1 , most preferably from 1 .4: 1 to 2:1.

14. The process according to any preceding claim, wherein, during deposition of the layer based on fluorine-doped tin oxide that is directly beneath the outermost layer based on fluorine-doped tin oxide, the gaseous mixture has a molar ratio of the source of tin : the source of fluorine of from 1 :1.2 to 10:1 , more preferably from 1.1 :1 to 5:1 , even more preferably from 1.5:1 to 4:1 , most preferably from 1.9:1 to 3:1.

15. The process according to any preceding claim, wherein the coating based on fluorine-doped tin oxide consists essentially of, preferably consists of, fluorine-doped tin oxide, preferably SnO2:F.

16. Use of the coated glass article produced in accordance with any of claims 1 to 15 in architectural, automotive or electronic device applications.

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