GLASS TREATMENT

Abstract

A method is disclosed, for removal of tin deposits from a glass substrate during a float glass manufacturing process. An acidic gas, such as hydrogen fluoride, is delivered to the substrate surface using chemical vapour deposition apparatus.

Claims

1.-18. (canceled)

19. A method of removing tin from a surface of a float glass substrate comprising at least the following steps in sequence: a) providing a float glass substrate that directly or indirectly bears one or more tin deposits on a major surface thereof, and b) removing at least a portion of said tin deposits from said surface of the substrate by reacting said tin deposits with an acidic gas that is introduced via a Chemical Vapour Deposition (CVD) apparatus.

20. The method according to claim 19, wherein the acidic gas comprises a fluorine-containing acid, preferably HF.

21. The method according to claim 19, wherein the acidic gas further comprises water vapour.

22. The method according to claim 21, wherein the ratio of the volume of water vapour to the volume of acid in the acidic gas is at least 0.5.

23. The method according to claim 22, wherein the ratio of the volume of water vapour to the volume of acid in the acidic gas is at most 30.

24. The method according to claim 19, wherein step b) is carried out using a precursor gas mixture comprising HF, nitrogen and water.

25. The method according to claim 19, wherein the method is carried out during the float glass manufacturing process.

26. The method according to claim 25, wherein the CVD apparatus is provided within a float bath section.

27. The method according to claim 19, wherein the glass substrate is moving during step b).

28. The method according to claim 19, wherein step b) is carried out when the glass substrate is at a temperature in the range 550° C. to 700° C.

29. The method according to claim 19, wherein the major surface of the float glass substrate of step a) is coated with at least one layer located between said major surface and said one or more tin deposits.

30. The method according to claim 19, wherein the method further comprises depositing at least one layer on the surface of the substrate following step b).

31. The method according to claim 29, wherein said layer comprises at least one layer based on a transparent conductive coating (TCC), wherein the TCC is a transparent conductive oxide (TCO), and wherein the TCO is one or more of fluorine doped tin oxide (SnO.sub.2:F), zinc oxide doped with aluminium, gallium or boron (ZnO:Al, ZnO:Ga, ZnO:B), indium oxide doped with tin (ITO), cadmium stannate, ITO:ZnO, ITO:Ti, In.sub.2O.sub.3, In.sub.2O.sub.3—ZnO (IZO), In.sub.2O.sub.3:Ti, In.sub.2O.sub.3:Mo, In.sub.2O.sub.3:Ga, In.sub.2O.sub.3:W, In.sub.2O.sub.3:Zr, In.sub.2O.sub.3:Nb, In.sub.2-2xM.sub.xSn.sub.xO.sub.3 with M being Zn or Cu, ZnO:F, Zn.sub.0.9Mg.sub.0.1O:Ga, (Zn,Mg)O:P, ITO:Fe, SnO.sub.2:Co, In.sub.2O.sub.3:Ni, In.sub.2O.sub.3:(Sn,Ni), ZnO:Mn, and/or ZnO:Co.

32. The method according to claim 19, wherein the major surface of the float glass substrate of step a) is coated with at least one layer based on an oxide of a metal or of a metalloid, located between said major surface and said one or more tin deposits.

33. The method according to claim 19, wherein the major surface of the float glass substrate of step a) is coated with at least one layer based on SiO.sub.2, SnO.sub.2, TiO.sub.2, silicon oxynitride and/or aluminium oxide, located between said major surface and said one or more tin deposits.

34. The method according to claim 19, wherein the method further comprises depositing at least one layer based on an oxide of a metal or of a metalloid following step b).

35. The method according to claim 19, wherein the method further comprises depositing at least one layer based on SiO.sub.2, SnO.sub.2, TiO.sub.2, silicon oxynitride and/or aluminium oxide following step b).

36. The method according to claim 19, wherein the major surface of the float glass substrate of step a) is coated with, in sequence from the glass substrate and located between said major surface and said one or more tin deposits: a lower anti-reflection layer, a silver-based functional layer; and at least one further anti-reflection layer.

37. The method according to claim 19, wherein the method further comprises, following step b), depositing in sequence on the glass substrate: a lower anti-reflection layer, a silver-based functional layer; and at least one further anti-reflection layer.

38. A glass substrate produced by the method according to claim 19.

Description

[0046] 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:

[0047] FIG. 1 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 present invention.

[0048] As discussed above, the removal of tin deposits from a surface of a float glass substrate by reacting with an acidic gas that is introduced via a CVD apparatus may be carried out 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 FIG. 1. However, it should be understood that the float glass installation 10 described herein is only illustrative of such installations.

[0049] As illustrated in FIG. 1, the float glass installation 10 may comprise a canal section 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 non-oxidizing atmosphere is maintained to prevent oxidation of the molten tin 15.

[0050] In operation, the molten glass 19 flows along the canal 20 beneath a regulating tweel 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 removal of the tin deposits preferably takes place in the float bath section 11, although it may be possible for the removal 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.

[0051] As illustrated in FIG. 1, four CVD apparatuses 9, 9A, 9B, 9C are shown within the float bath section 11. Thus, depending on the frequency and nature of the tin deposits it may be desirable to use one or more than one of the CVD apparatuses 9, 9A, 9B, 9C, whilst any remaining CVD apparatuses may be utilized to form one or more coating layers if desired. A 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, tin deposits are removed using CVD apparatus 9A, a tin oxide coating is formed utilizing CVD apparatus 9, a silica coating is formed utilizing an adjacent apparatus 9B and the remaining apparatus 9C is utilized to form a fluorine doped tin oxide coating.

[0052] A suitable non-oxidizing atmosphere, generally nitrogen or a mixture of nitrogen and hydrogen in which nitrogen predominates, is 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.

[0053] The CVD removal of tin deposits and deposition of coating layers are 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 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.

[0054] 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 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.

[0055] 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.