COATED GLASS PANE

Abstract

The present invention relates to a coated glass pane, a method of producing a coated glass pane, a multiple glazing comprising a coated glass pane and a use of a coated glass pane and/or multiple glazing in a building or vehicle. The coated glass pane includes a glass substrate and a coating suitable for reflecting infra-red radiation. The coating includes a base layer including an oxide of zirconium and titanium Zr.sub.xTi.sub.yO.sub.z and the atomic proportion of Zr based on Zr and Ti in the base layer, calculated as x/(x+y), is from 0.40 to 0.95.

Claims

1-25. (canceled)

26. A coated glass pane comprising a glass substrate and a coating, wherein the coating comprises, in sequence from the glass substrate: a base layer adjacent to and in contact with the glass substrate; a silver-based functional layer; and an upper dielectric layer, wherein: the base layer comprises an oxide of zirconium and titanium Zr.sub.xTi.sub.yO.sub.z; and the atomic proportion of Zr based on Zr and Ti in the base layer, calculated as x/(x+y), is from 0.40 to 0.95.

27. A coated glass pane according to claim 26, wherein the atomic proportion of Zr based on Zr and Ti in the base layer, calculated as x/(x+y), is from 0.50 to 0.90, preferably from 0.55 to 0.85, more preferably from 0.60 to 0.80, yet more preferably from 0.62 to 0.67.

28. A coated glass pane according to claim 26, wherein the atomic % of titanium in the base layer, calculated as Ti in the total composition, is from 1 to 25, preferably from 5 to 20, more preferably from 8 to 15.

29. A coated glass pane according to claim 26, wherein the atomic % of oxygen in the base layer, calculated as O in the total composition, is from 60 to 70, preferably from 62 to 66, more preferably from 63 to 65.

30. A coated glass pane according to claim 26, wherein the atomic % of zirconium in the base layer, calculated as Zr in the total composition, is from 12 to 35, preferably from 15 to 25.

31. A coated glass pane according to claim 26, wherein the thickness of the base layer in nm is from 6 to 60, preferably from 8 to 45, more preferably from 10 to 30.

32. A coated glass pane according to claim 26, wherein the Zr factor of the base layer, calculated as the thickness of the base layer in nm multiplied by the atomic proportion of Zr based on Zr and Ti in the base layer, is from 1 to 35, preferably from 5 to 20, more preferably from 7 to 15, even more preferably from 8 to 12.

33. A coated glass pane according to claim 26, wherein the coating further comprises a growth promotion layer between the base layer and the silver-based functional layer, preferably the silver-based functional layer is in direct contact with the growth promotion layer and/or the growth promotion layer is based on an oxide of zinc.

34. A coated glass pane according to claim 33, wherein the growth promotion layer is in direct contact with the base layer.

35. A coated glass pane according to claim 26, wherein the coating further comprises a stabilisation layer between the base layer and the growth promotion layer, preferably the stabilisation layer is in direct contact with the base layer.

36. A coated glass pane according to claim 35, wherein the coating further comprises a separation layer between the stabilisation layer and the growth promotion layer, preferably the separation layer is in direct contact with the stabilisation layer.

37. A coated glass pane according to claim 26, wherein the coating further comprises a barrier layer between the silver-based functional layer and the upper dielectric layer, preferably the barrier layer is in direct contact with the silver-based functional layer.

38. A coated glass pane according to claim 26, wherein the coating further comprises a second silver-based functional layer between the silver-based functional layer and the upper dielectric layer, preferably the coating further comprises a central dielectric layer between the silver-based functional layer and the second silver-based functional layer and/or a second barrier layer between the second silver-based functional layer and the upper dielectric layer.

39. A coated glass pane according to claim 38, wherein the coating further comprises a third silver-based functional layer between the second silver-based functional layer and the upper dielectric layer, preferably the coating further comprises a second central dielectric layer between the second silver-based functional layer and the third silver-based functional layer and/or a third barrier layer between the third silver-based functional layer and the upper dielectric layer.

40. A coated glass pane according to claim 26, wherein the coated glass pane has a Rg a* of from 6 to +6.5 and Rg b* of from 14 to 2.5.

41. A coated glass pane according to claim 26, wherein the sheet resistance Rs is less than 8 /.

42. A coated glass pane according to claim 26, wherein the coated glass pane is a heat treatable coated glass pane.

43. A coated glass pane according to claim 26, wherein the coated glass pane is a heat treated coated glass pane, preferably the heat treated coated glass pane is a thermally bent coated glass pane and/or a thermally strengthened coated glass pane.

44. A coated glass pane according to claim 43, wherein the thermally strengthened coated glass pane achieves Class 1 to EN 12600.

45. A coated glass pane according to claim 43, wherein the heat treated coated glass pane has a change in colour characteristics E* compared to a comparable annealed coated glass pane of less than or equal to 3.

46. A coated glass pane according to claim 43, with a hazescan value of less than 90.

47. A method of manufacturing a coated glass pane according to claim 26, comprising the steps of: i) providing a glass substrate; ii) providing a base layer; iii) providing a silver-based functional layer; and iv) providing an upper dielectric layer.

48. A method of manufacturing a coated glass pane according to claim 47, wherein the base layer, and/or the silver-based functional layer, and/or the upper dielectric layer are provided by physical vapour deposition.

49. A multiple glazing unit comprising a coated glass pane according to claim 26, preferably wherein the multiple glazing unit is a laminated glazing unit and/or an insulated glazing unit.

Description

[0167] FIG. 1 illustrates a schematic cross-sectional view of a coated glass pane according to a first embodiment of the present invention.

[0168] FIG. 2 illustrates a schematic cross-sectional view of a coated glass pane according to a second embodiment of the present invention.

[0169] FIG. 3 illustrates a schematic cross-sectional view of a coated glass pane according to a third embodiment of the present invention.

[0170] FIG. 4 illustrates a chart of Hazescan and sheet resistance after heat treatment, Rs T, against atomic proportion of Zr based on Zr and Ti for coated glass panes comprising coatings comprising only one silver layer.

[0171] FIG. 5 illustrates a chart of Hazescan and sheet resistance after heat treatment, Rs T, against Zr factor for coated glass panes comprising coatings comprising only one silver layer.

[0172] FIG. 6 illustrates a chart of Hazescan and sheet resistance after heat treatment, Rs T, against atomic proportion of Zr based on Zr and Ti for coated glass panes comprising coatings comprising two or more silver layers.

[0173] FIG. 7 illustrates a chart of Hazescan and sheet resistance after heat treatment, Rs T, against Zr factor for coated glass panes comprising coatings comprising two or more silver layers.

[0174] In the figures like features are represented with like numerals.

[0175] FIG. 1 depicts a coated glass pane 100 according to a first embodiment of the present invention comprising a glass substrate 1 and a coating 2, wherein the coating 2 comprises, in sequence from the glass substrate 1: a base layer 3 adjacent to and in contact with the glass substrate 1; a silver-based functional layer 5; and an upper dielectric layer 7, wherein: the base layer 3 comprises an oxide of zirconium and titanium; and the atomic proportion of Zr based on Zr and Ti in the base layer is from 0.40 to 0.95.

[0176] FIG. 2 depicts a coated glass pane 200 according to a second embodiment of the present invention, comprising a glass substrate 1 and a coating 2, wherein the coating 2 comprises, in sequence from the glass substrate 1: a base layer 3 adjacent to and in contact with the glass substrate 1; a lower dielectric layer 4 comprising a stabilisation layer 41, a separation layer 42, and a growth layer 43; a silver-based functional layer 5; a barrier layer 6; an upper dielectric layer 7, and a protection layer 8, wherein: the base layer 3 comprises an oxide of zirconium and titanium; and the atomic proportion of Zr based on Zr and Ti in the base layer is from 0.40 to 0.95.

[0177] FIG. 3 depicts a coated glass pane 300 according to a third embodiment of the present invention, comprising a glass substrate 1 and a coating 2, wherein the coating 2 comprises, in sequence from the glass substrate 1: a base layer 3 adjacent to and in contact with the glass substrate 1; a lower dielectric layer 4 comprising a stabilisation layer 41, a separation layer 42, and a growth layer 43; a first silver-based functional layer 51; a first barrier layer 61; a central dielectric layer 9; a second silver based functional layer 52; a second barrier layer 62; an upper dielectric layer 7, and a protection layer 8, wherein: the base layer 3 comprises an oxide of zirconium and titanium; and the atomic proportion of Zr based on Zr and Ti in the base layer is from 0.40 to 0.95.

[0178] Example embodiments of the present invention will now be described herein, by way of example only.

[0179] For all examples the coatings were deposited on 4 mm thick standard float glass panes with a light transmittance in the region of 90% using AC and/or DC magnetron (or pulsed DC) sputtering devices, medium-frequency sputtering being applied where appropriate.

[0180] Base layers comprising an oxide of zirconium and titanium were reactively co-sputtered from a first target of titanium metal and a second target of zirconium metal in an argon/oxygen (Ar/O.sub.2) sputter atmosphere with approximately 12% oxygen. The proportions of Zr and Ti were varied by altering the sputtering power over the targets. The power of the Ti target was varied between 0.4 and 1.5 kW, and the power of the Zr target was varied between 0.15 and 1.5 kW.

[0181] Dielectric layers of an oxide of zinc and tin were reactively sputtered from zinc-tin targets (weight ratio Zn:Sn approximately 50:50) in an argon/oxygen (Ar/O.sub.2) sputter atmosphere.

[0182] Dielectric layers of an oxide of zinc (Zn), tin (Sn) and zirconium (Zr) were co-sputtered using metallic ZnSn (weight ratio Zn:Sn approximately 50:50) and Zr targets in an Ar/O.sub.2 or pure argon (Ar) atmosphere.

[0183] The titanium oxide (TiO.sub.x) layers were deposited from metallic titanium (Ti) targets in an argon/oxygen (Ar/O.sub.2) sputter atmosphere.

[0184] The ZnO:Al growth promoting top layers of the lower dielectric layers were sputtered from Al-doped Zn targets (aluminium (Al) content about 2 weight %) in an Ar/O.sub.2 sputter atmosphere.

[0185] The functional layers that in all examples consisted of essentially pure silver (Ag) were sputtered from silver targets in an Ar sputter atmosphere without any added oxygen and at a partial pressure of residual oxygen below 10-5 mbar.

[0186] The barrier layers located above the silver-based functional layers of zinc aluminium oxide (also referred to as ZAO), were sputtered from conductive ZnO.sub.x:Al targets comprising 2% AlO.sub.x by weight in a pure Argon (Ar) sputter atmosphere with less than 5% oxygen.

[0187] Table 1 provides details of a number of comparative coated glass panes and coated glass panes according to the present invention. Comparative example CE1 was prepared by sputtering a soda-lime silica glass sheet to provide a glass pane with a coating comprising, in order from the glass surface: SiN.sub.x (20 nm), ZnSnO.sub.x (4 nm), ZAO(8 nm), Ag (10 nm), NiCrO.sub.x (1 nm) ZAO(6 nm), SiN.sub.x (24 nm), ZnSnO.sub.x (9 nm). CE1 is a baseline coating with properties which are acceptable in many situations. However, as discussed above, it is desirable to provide alternative coatings that are more suitable for architectural and automotive applications.

[0188] Further comparative examples CE2 and CE3, and examples 1 to 20 were produced in a similar manner, but the SiN.sub.x base layer of CE1 was replaced by Zr.sub.xTi.sub.yO.sub.z layers to provide a coating comprising, in order from the glass surface: Zr.sub.xTi.sub.yO.sub.z, ZnSnO.sub.x (4 nm), ZAO(8 nm), Ag (10 nm), NiCrO.sub.x (1 nm) ZAO(6 nm), SiN.sub.x (24 nm), ZnSnO.sub.x (9 nm). The Zr.sub.xTi.sub.yO.sub.z layers were of varying compositions and thicknesses, as disclosed in Table 1.

TABLE-US-00001 TABLE 1 Zr.sub.xTi.sub.yO.sub.2 Composition Atomic Base layer atomic % proportion thickness Zr Hazescan TL % Rs AD RS Rs T Rf a* Rf b* Rf Example Zr Ti O of Zr nm Factor T AD TL / / / AD AD E* CE1 20 58 82 5.2 6.3 1.7 4.6 CE2 2.1 34.1 62.9 0.06 16 0.93 225 83 4.9 5.9 1.6 4.3 1.33 4.9 2 CE3 2.1 34.1 62.9 0.06 16 0.93 214 82.9 5.4 5.7 1.5 4.2 1.44 4.65 2 1 17 18.4 64.6 0.48 16 7.68 97 82.5 5.5 6.1 2.1 4 0.25 5.86 1.9 2 19.7 15.6 64.7 0.56 16 8.93 70 82.8 5.6 5.5 1.7 3.8 0.25 6.12 1.4 3 20.4 14.6 65 0.58 16 9.33 93 81.9 5.8 6.3 2 4.3 0.8 9.1 2.5 4 20.4 14.6 65 0.58 16 9.33 95 81.3 6.2 6.4 1.9 4.5 1.6 10.5 3 5 20.7 14.7 64.6 0.58 11.4 6.67 116 83.5 3.8 6.2 2 4.2 0.49 11.16 2.6 6 20.7 14.7 64.6 0.58 14 8.19 73 82.3 5.4 5.8 1.8 4 0.38 10.4 2.6 7 20.7 14.7 64.6 0.58 14 8.19 69 82.5 5.6 5.7 1.9 3.8 0.33 8.09 1.8 8 20.7 14.7 64.6 0.58 16 9.36 80 82.5 5.9 6 2.2 3.8 0.35 7.09 2.4 9 20.7 14.7 64.6 0.58 16 9.36 80 81.7 5.6 5.9 2 3.9 3.75 10.5 3.7 10 20.7 14.7 64.6 0.58 18 10.53 84 82.6 5.6 6.2 1.4 4.8 2.36 8 3.5 11 20.7 14.7 64.6 0.58 18 10.53 86 82.7 5.6 5.9 1.5 4.4 2.36 7.27 2.9 12 20.7 14.7 64.6 0.58 20 11.69 63 83.5 5.4 5.8 1.9 3.9 0.28 1.16 0.6 13 20.7 14.7 64.6 0.58 20 11.69 64 83.3 5.8 5.6 2 3.6 0.39 0.81 1 14 21.9 13.6 64.5 0.62 16 9.87 58 81.9 5.6 6 2.1 3.9 0.33 9.49 2.6 15 22.9 12.3 64.8 0.65 16 10.41 45 82.1 5.5 6 2.1 3.9 0.47 8.19 2.5 16 22.9 12.3 64.8 0.65 16 10.41 65 81.9 5.5 5.8 2 3.8 0.44 5.8 2.2 17 25 10.7 64.6 0.70 16 11.20 56 81.5 6 6.6 2.3 4.3 1.65 9.6 3.3 18 26.3 8.2 65.5 0.76 16 12.20 47 81.3 5.2 6.6 2.2 4.4 1.8 10.5 2.8 19 32.2 3.4 64.4 0.90 16 14.47 81 81.7 4 6.4 2.1 4.3 1 9.91 1.8 20 32.2 3.4 64.4 0.90 16 14.47 135 81.6 2.7 6.5 1.6 4.9 1.37 10.47 2.8

[0189] Immediately after deposition of all of the coatings, the coated glass sheet parameters (such as sheet resistance (Rs), UV-vis optical performance) for the coated glass panes were measured. The samples were then heat treated in the region of 650 C. for 5 minutes. Thereafter, Hazescan, sheet resistance (Rs), UV-vis optical performance were measured and the change in light transmittance (TL), and the change in colour characteristics (described by changes in a*, b* and Y) upon heat treatment (E*), calculated there from as discussed below. The measured and calculated results are provided in Table 1, as follows: haze, TL % ADpercentage (%) light transmittance value for the glass substrate before heat treatment, TLthe change in percentage (%) light transmittance upon heat treatment, Rs AD /sheet resistance before heat treatment, RSchange in sheet resistance upon heat treatment, Rs Tsheet resistance after heat treatment, Rf a* ADfilm reflected a* colour component after deposition and before heat treatment, Rf b* ADfilm reflected b* colour component after deposition and before heat treatment, and Rf E*which is a measure of the change in film side reflectance upon heat treatment.

[0190] The methodology used to collect the data in Table 1 is set out below.

[0191] CE2 and CE3 have unacceptably high Hazescan values, which are apparently caused by the low atomic proportion of Zr, 0.6, and/or low Zr factor of 0.93.

[0192] Example 1 has a Hazescan value which is improved compared to CE2 and CE3, and may be acceptable in some situations, but is not superior to the baseline coating. However, the improvement in sheet resistance due to heat treatment is superior for example 1 when compared to CE1. As such, the increase in atomic proportion of Zr and/or Zr factor has improved the properties of the coating.

[0193] Example 2 exhibits a good Hazescan value of 70, lower than the comparative examples CE1 and CE2. However, the colour coordinates for the coating side reflection are in a desirable area, and example 1 exhibits a lower Rf E* value than other examples, indicating excellent colour consistency following heat treatment.

[0194] Example 12 exhibits a good Hazescan value of 63, excellent transmission before and after heat treatment and Rs T of less than 4. The Rf a* and b* are slightly positive, which may be desirable in some situations, and are not significantly altered by heat treatment as indicated by the low Rf E* value.

[0195] Example 15 exhibits an exceptional Hazescan value of 45 and a good Rs AD of 6 which is enhanced by heat treatment to a large extent to provide a Rs T of less than 4.

[0196] FIG. 4 depicts the Hazescan of comparative examples CE2 and CE3 and examples 1 to 20 against atomic proportion of Zr. It can be seen that Hazescan improves with increasing atomic proportion of Zr, reaching a minimum of 45 for a Zr proportion of 0.65, but then increases with atomic proportion of Zr above this. Good Hazescan values of less than 70 are achievable by atomic proportions of Zr of 0.55 to 0.85, and excellent Hazescan values of less than 60 are achievable by atomic proportions of Zr of from 0.6 to 0.8.

[0197] FIG. 4 also depicts Rs T of comparative examples CE2 and CE3 and examples 1 to 20 against atomic proportion of Zr. It can be seen that, similarly to Hazescan, Rs T decreases with increasing atomic proportion of Zr to a minimum Rs T of 3.6 at a Zr proportion of 0.58, and then increases with atomic proportion of Zr above this. Good Rs T values of less than 4 are achievable with atomic proportions of Zr of 0.55 to 0.85.

[0198] FIG. 5 depicts the Hazescan of comparative examples CE2 and CE3 and examples 1 to 20 against Zr factor. It can be seen that Hazescan improves with increasing Zr factor, reaching a minimum of 45 for a Zr factor of 10.53, but then increases with Zr factor above this. Good Hazescan values of less than 70 are achievable by Zr factors of from 7 to 15, and excellent Hazescan values of less than 60 are achievable by Zr factors of from 9 to 12.

[0199] FIG. 5 also depicts Rs T of comparative examples CE2 and CE3 and examples 1 to 20 against Zr factor. It can be seen that, similarly to Hazescan, Rs T decreases with increasing Zr factor to a minimum Rs T of 3.6 at a Zr factor of 11.69, and then increases with Zr factor above this. Good Rs T values of less than 4 are achievable with Zr factors of from 7 to 15.

[0200] Coated glass panes with more than one silver layer were investigated. A comparative example CED was prepared by sputtering with the following layers from the glass surface: SiN.sub.x (18 nm); ZnSnO.sub.x (13 nm); ZAO(3 nm); Ag (9.5 nm); NiCrO.sub.x (1 nm); ZAO(7 nm); SiN.sub.x (40 nm); ZnSnO.sub.x (11 nm); ZAO(14 nm); Ag (12.8 nm); NiCrO.sub.x (1 nm); ZAO(5 nm); SiN.sub.x (21 nm); ZnSnO.sub.x (8 nm).

[0201] Examples D1 to D6 were prepared by sputtering, using the same methods.

[0202] In D1, and D3 to D6 the SiN.sub.x base layer of CED was replaced with a layer of Zr.sub.xTi.sub.yO.sub.z, to provide a coating according to the present invention comprising: Zr.sub.xTi.sub.yO.sub.z; ZnSnO.sub.x (13 nm); ZAO (3 nm); Ag (9.5 nm); NiCrO.sub.x (1 nm); ZAO (7 nm); SiN.sub.x (40 nm); ZnSnO.sub.x (11 nm); ZAO (14 nm); Ag (12.8 nm); NiCrO.sub.x (1 nm); ZAO (5 nm); SiN.sub.x (21 nm); ZnSnO.sub.x (8 nm).

[0203] In D2 both the SiN.sub.x base layer and the ZnSnO.sub.x layer immediately adjacent to the base layer of CED were replaced with a single layer of Zr.sub.xTi.sub.yO.sub.z of thickness 17.5 nm, to provide a coating according to the present invention comprising: Zr.sub.xTi.sub.yO.sub.z (17.5 nm); ZAO(3 nm); Ag (9.5 nm); NiCrO.sub.x (1 nm); ZAO (7 nm); SiN.sub.x (40 nm); ZnSnO.sub.x (11 nm); ZAO (14 nm); Ag (12.8 nm); NiCrO.sub.x (1 nm); ZAO (5 nm); SiN.sub.x (21 nm); ZnSnO.sub.x (8 nm).

TABLE-US-00002 TABLE 2 CED D1 D2 D3 D4 D5 D6 Zr.sub.xTi.sub.yO.sub.2 Zr 20.7 20.7 20.4 22.8 25 26.3 Composition Ti 14.7 14.7 14.6 12.5 10.7 8.2 atomic % O 64.6 64.6 65 64.6 64.6 65.5 Atomic proportion 0.58 0.58 0.58 0.65 0.70 0.76 of Zr Base layer 18 13 17.5 12 12 12 12 thickness nm Zr Factor 7.60 10.23 6.99 7.75 8.40 9.15 Hazescan after 39 68 54 64 52 42 41 toughening TL % AD 70 71.5 70.9 69.3 69.4 69 68.8 TL 10.6 10.7 9.8 11.6 11.2 11.9 11.7 Rs AD / 3 2.7 2.7 2.9 2.8 2.9 2.9 RS 0.4 0.9 0.8 0.9 0.8 0.9 0.9 Rs T 2.6 1.8 1.9 2 2 2 2 Rf a* AD 1.29 0.94 2.64 1.06 0.7 2.2 1.9 Rf b* AD 0.1 0.68 3.34 1.34 1.3 1.9 1.5 Rf E* 2.9 6 6.7 5.6 5.8 5.9 6.1

[0204] Examples D1 to D6 offer superior sheet resistance compared to CED, both before and after heat treatment. In addition, Examples D1 to D6 offer good, and in some cases excellent Hazescan results. As depicted in FIG. 6, for coatings including two or more silver layers an increase in atomic proportion of Zr based on Zr and Ti of the base layer is associated with a decrease in Hazescan value, and an atomic proportion of Zr based on Zr and Ti of from 0.6 to 0.8 is particularly beneficial.

[0205] As depicted in FIG. 7 Hazescan reaches a minimum value at a Zr factor of 9.15. For coatings including two or more silver layers a Zr factor of the base layer from 8 to 10 is particularly beneficial.

[0206] The methodologies used to collect the above disclosed data include:

[0207] Light TransmittanceThe values stated for the change in percentage (%) light transmittance upon heat treatment (TL) of the coated glass panes were derived from measurements using illuminant D65, for a 10 degree observer field of view across wavelengths ranging from 350-1050 nm.

[0208] Sheet Resistance/Change in sheet resistance for examplesSheet resistance measurements were made using a NAGY SRM-12. This device utilises an inductor to generate eddy currents in a 100 mm100 mm coated sample. This produces a measurable magnetic field, the magnitude of which is related to the resistivity of the sample. With this method the sheet resistance can be calculated. The instrument was used to measure the sheet resistance of samples before and after heat treatment at 650 C. for 5 minutes.

[0209] Colour characteristicsThe colour characteristics for each of sample were measured and reported using the well-established CIE LAB L*, a*, b* coordinates (as described for example in paragraphs [0030] and [0013] of WO 2004/063111A1, incorporated herein by reference). In some situations, it is desirable for the coated pane to exhibit neutral colours in transmission (T), glass side reflection (Rg), and coating, i.e. film, side reflection (Rf), that is a* and b* values from 5 to +5, preferably from 2 to +2. However, in some applications and markets more blue colours are desirable, wherein a* and b* are both <0 and may even be <5 for strongly blue colours. Alternatively, bronze colours are sometimes desirable, wherein a* and b* are both >0 and may even be >5.

[0210] The change in transmission colour upon heat treatment, E*=((a*).sup.2+(b*).sup.2+(L*).sup.2).sup.1/2, wherein L*, Aa* and Ab* are the differences of the colour values L*, a*, b* of the coated glass pane each before and after a heat treatment. E* values of less than 3 (for example 2 or 2.5) are preferred for layer sequences with one silver-based functional layer, representing a low and practically non-noticeable colour modification caused by the heat treatment. For layer sequences comprising two or more silver-based functional layer, lower T E* values provide an indication of the stability of the sequences; the lower the T E* values the more superior the results and appearance of the coated glass pane.

[0211] HazescanA haze scoring system was applied to each of the examples and comparative examples, wherein the haze was measured following heat treatment. The quality assessment evaluation system described hereinafter was also used to more clearly distinguish the visual quality of coatings under bright light conditions; properties that are not fully reflected by standard haze values measured in accordance with ASTM D 1003.

[0212] The evaluation system considers the more macroscopic effect of visible faults in the coating which cause local colour variations where the coating is damaged or imperfect (hazescan in Table 1). This assessment analyses the light levels in images of heat treated samples taken using fixed lighting conditions and geometries.

[0213] To generate the images used to calculate hazescan values, samples are placed inside a black box, 30 cm away from the camera lens. Samples are illuminated using a standard 1200 lumen light with a brightness between 2400 and 2800 Lux, as measured at the samples position. The sample is then photographed using a standard aperture size and exposure length of f5.6 and 1 second with focal length of 105 mm and ISO 400. The greyscale of each pixel in the resulting image is then recorded, with a value of 0 representing black and 255 representing white. Statistical analysis of these values is undertaken to give an overall assessment of the haze of the sample, referred to herein as the hazescan value. The lower the hazescan value recorded, the more superior the results. In general, a hazescan value of less than 90, preferably less than 80 and even more preferably less than 70 is desirable. In some specialist applications, where clarity is prioritised, a hazescan value of less than 60 is desired.

[0214] XPS analysisX-ray photoelectron spectroscopy (XPS) depth profiling was carried out on Thermo K-Alpha XPS using an argon ion etch beam operating at 1 keV (M), producing a beam current of 1.71 A, and rastered over a 2.04.0 mm area. A 15 second etch time per level was used with 100 levels of total etching. The X-ray spot size used was 400 m. The binding energy windows used in the acquisition of the profile were: O1s, C1s, Zn2p, Sn3d, Zr3d, Si2p, Ca2p, Na1s and Mg1s. A survey spectrum (which collects the entire 0-1350 eV binding energy range) was also collected to enable the detection of any additional elements present within the coating. As XPS is a quantitative technique, the concentration of each element within a coating layer may be determined and used to calculate a stoichiometry. For each coating, an average stoichiometry was calculated, based on the average concentration of each element in the layer. The first few etch levels were removed to reduce the influence of surface contamination.

[0215] Examples according to the invention incorporating only single silver layers offer excellent colour characteristics, in particular, coatings including only a single silver layer were within the colour box a* 3 to +6.5 and b* 14 to 4 for Rg, and coatings including two or more silver layers were within the colour box a* 6 to 4.8 and b* 18.5 to 2.3 for Rg.

[0216] As demonstrated by the examples, the coated glass panes according to the present invention all exhibit good sheet resistance values after deposition, and a negative change in sheet resistance upon heat treatment, indicating that the silver functional layer is adequately protected from damage.

[0217] The examples according to the invention exhibit good hazescan values before and after heat treatment, which indicates that the stack combinations are not compromised by heat treatment. The panes of the present invention also show a low level of visible damage according to the tests simulating use, processing and handling conditions for coated glass panes. Furthermore, the panes exhibit high light transmittance and low emissivity and/or good solar control properties, with optical properties remaining stable even after heat treatment.

[0218] Surprisingly, coatings according to the present invention exhibit parameters which indicate that they are suitable for applications where toughened panes are required. In particular, hazescan of the examples according to present invention measured following heat treatment was remarkably low, in some cases less than 50.