PROCESS FOR PREPARING A COATED GLASS SUBSTRATE

Abstract

A chemical vapour deposition process for preparing a coated glass substrate, said process comprising at least the following steps in sequence: a) providing a glass substrate having a surface, b) depositing a layer based on SiCO and/or SiNO on the surface of the glass substrate, c) exposing the layer based on SiCO and/or SiNO to a gaseous mixture (i) comprising water, and d) subsequently depositing a layer based on a TCO over the layer based on SiCO and/or SiNO.

Claims

1.-17. (canceled)

18. A chemical vapour deposition process for preparing a coated glass substrate, said process comprising at least the following steps in sequence: a) providing a glass substrate having a surface, b) depositing a layer based on SiCO and/or SiNO on the surface of the glass substrate, c) exposing the layer based on SiCO and/or SiNO to a gaseous mixture (i) comprising water, and d) subsequently depositing a layer based on a TCO over the layer based on SiCO and/or SiNO.

19. The process according to claim 18, wherein exposing the layer based on SiCO and/or SiNO to a gaseous mixture (i) comprising water in step c) thereby incorporates oxide ions into the layer based on SiCO and/or SiNO.

20. The process according to claim 18, wherein step c) occurs without the deposition of a further layer onto the layer based on SiCO and/or SiNO.

21. The process according to claim 18, wherein the gaseous mixture (i) also comprises oxygen.

22. The process according to claim 18, wherein between steps c) and d) the layer based on SiCO and/or SiNO is exposed to a gaseous mixture (iii) comprising oxygen.

23. The process according to claim 18, wherein the gaseous mixture (i) comprises a ratio of water to oxygen of at least 1.5:1 by volume, preferably at least 3:1 by volume.

24. The process according to claim 18, wherein the gaseous mixture (i) comprises 25% to 65% by volume water and 2% to 20% by volume oxygen.

25. The process according to claim 18, wherein in step c) the water is delivered at a flow rate of at least 50 slm (standard litres per minute), preferably at least 100 slm, more preferably at least 150 slm, most preferably at least 190 slm; but preferably at most 350 slm, more preferably at most 300 slm, even more preferably at most 250 slm, most preferably at most 210 slm.

26. The process according to any of claim 21, wherein in step c) the oxygen is delivered at a flow rate of at least 15 slm, more preferably at least 20 slm, even more preferably at least 25 slm, most preferably at least 30 slm; but preferably at most 55 slm, more preferably at most 50 slm, even more preferably at most 45 slm, most preferably at most 40 slm.

27. The process according to claim 18, wherein step b) is carried out in a non-oxidising atmosphere.

28. The process according to claim 18, wherein steps b), c) and d) are all carried out in a float bath.

29. The process according to claim 18, wherein step b) is carried out by exposing the surface of the glass substrate to a gaseous mixture (ii) comprising a silicon source, a carbon source and an oxygen source.

30. The process according to claim 18, wherein the layer based on a TCO is deposited directly on to the layer based on SiCO.

31. The process according to claim 18, wherein step c) is carried out when the transparent glass substrate is at a temperature of at least 640° C., more preferably at least 670° C., but preferably at most 760° C., more preferably at most 740° C.

32. The process according to claim 18, wherein the coated glass substrate exhibits a sheet resistance of at most 21 ohms/sq, preferably at most 20 ohms/sq, but preferably at least 5 ohms/sq, more preferably at least 10 ohms/sq.

33. The process according to claim 18, wherein the coated glass substrate exhibits a haze, when tested in accordance with ASTM D1003-13, of at least 0.5%, preferably at least 0.8%, more preferably at least 1%, most preferably at least 1.2%, but preferably at most 5%, more preferably at most 3%, even more preferably at most 2.5%, most preferably at most 2.3%.

Description

[0068] 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:

[0069] FIG. 1 is a schematic view, in cross-section, of a coated glazing in accordance with the present invention;

[0070] FIG. 2 is a schematic view, in vertical section, of an installation for practicing the float glass process which incorporates several CVD apparatuses for preparing a coated glazing in accordance with the present invention.

[0071] FIG. 1 shows a cross-section of a coated glazing 1 according to certain embodiments of the present invention. Coated glazing 1 comprises a transparent float glass substrate 2 that has been sequentially coated using CVD with a layer based on SiCO 3, a layer based on fluorine doped tin oxide (SnO.sub.2:F) 4 and a layer based on tin oxide (SnO.sub.2) 5.

[0072] 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 FIG. 2. However, it should be understood that the float glass installation 10 described herein is only illustrative of such installations.

[0073] As illustrated in FIG. 2, 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.

[0074] 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 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.

[0075] As illustrated in FIG. 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 and the amount of gaseous mixture (i) required in step c) 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 SiCO layer is formed utilizing CVD apparatus 9A, a gaseous mixture of water, oxygen and nitrogen is supplied utilizing CVD apparatus 9, and adjacent apparatuses 9B and 9C are utilized to form a fluorine doped tin oxide layer.

[0076] 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.

[0077] 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 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 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.

EXAMPLES

[0078] All layer depositions and exposures of layers to water or water and oxygen were carried out using CVD. All Examples shown in Table 1 below were produced on a float line using a 3.2 mm soda-lime-silica glass substrate. Comparative Examples 1-3 and Examples 4-7 were coated at an average line speed of 11 m/min. The deposition of the base layer of SiCO was carried out at a glass temperature of 725° C. for all Examples. SiCO layers were deposited over the glass surface using a single coater with the following components: [0079] N.sub.2 carrier gas, C.sub.2H.sub.4, SiH.sub.4, and CO.sub.2.

[0080] SnO.sub.2 layers were deposited over the glass surface using a single coater with the following components: [0081] N.sub.2 carrier gas, O.sub.2, dimethyltin dichloride, and H.sub.2O.

[0082] SnO.sub.2:F layers were deposited over the glass surface using two coaters for each of the Examples with the following components: [0083] N.sub.2 carrier gas, O.sub.2, dimethyltin dichloride, HF, and H.sub.2O.

[0084] The exposure of SiCO layers to water or water and oxygen was carried out using a single coater with the following components: [0085] N.sub.2 carrier gas, water and optionally O.sub.2.

[0086] The thicknesses of the layers were as follows: SiCO (30-80 nm), SnO.sub.2:F (320-370 nm) & SnO.sub.2 (50-100 nm). The haze values of the Examples were measured in accordance with the ASTM D1003-13 standard using a BYK-Gardner Hazemeter. Sheet resistance was measured in accordance with a 4-point probe method using a commercially available 4-point probe.

TABLE-US-00001 TABLE 1 Flow rates for SiCO exposure to water or water and oxygen SiCO Exposure Coater SiCO Flow Rate (slm) Example Stack Exposure N.sub.2 H.sub.2O O.sub.2 Comp. Ex. 1 SiCO/SnO.sub.2:F/SnO.sub.2 None 200 0 0 Comp. Ex. 2 SiCO/SnO.sub.2:F/SnO.sub.2 None 200 0 0 Comp. Ex. 3 SiCO/SnO.sub.2:F/SnO.sub.2 None 200 0 0 Ex. 4 SiCO/SnO.sub.2:F/SnO.sub.2 Water/O.sub.2 200 200 35 Ex. 5 SiCO/SnO.sub.2:F/SnO.sub.2 Water 200 200 0 Ex. 6 SiCO/SnO.sub.2:F/SnO.sub.2 Water/O.sub.2 200 200 35 Ex. 7 SiCO/SnO.sub.2:F/SnO.sub.2 Water/O.sub.2 200 200 35

TABLE-US-00002 TABLE 2 a*, b*, sheet resistance and haze exhibited by examples SiCO Sheet Resistance Haze Example Exposure a* b* (ohms/sq) (%) Comp. Ex. 1 None 1.41 4.34 22 1.08 Comp. Ex. 2 None 1.52 2.83 21.21 0.91 Comp. Ex. 3 None 4.63 2.67 22.3 0.91 Ex. 4 Water/O.sub.2 3.69 3.13 17.3 1.38 Ex. 5 Water 2.23 3.56 18 1.53 Ex. 6 Water/O.sub.2 2.71 3.29 17.3 1.39 Ex. 7 Water/O.sub.2 2.88 4.06 17.3 1.26

[0087] As can be seen from the results in Table 2 above, exposing the SiCO layer to water results in an improved (lower) sheet resistance in the final product. The water exposure also provides higher haze which is beneficial for PV cells.

[0088] The exposure of the SiCO layer to the combination of both water and oxygen leads to a further reduction in sheet resistance.

[0089] The a* and b* values shown in Table 2 demonstrate that suitably neutral colours can be achieved when utilising this technique.