Coated glass pane

Abstract

A coated glass pane and a method of preparing same comprising at least the following layers in sequence: a glass substrate; a lower anti-reflection layer, a silver-based functional layer; a barrier layer; an upper dielectric layer; and a topmost dielectric layer which comprises an oxide of zinc (Zn), tin (Sn) and zirconium (Zr); and wherein the amount of zirconium in the topmost dielectric layer comprises at least 10 atomic percent zirconium.

Claims

1. A coated glass pane comprising at least the following layers in sequence: a glass substrate; a lower anti-reflection layer; a silver-based functional layer; a barrier layer; an upper dielectric layer; and a topmost dielectric layer which comprises an oxide of zinc (Zn), tin (Sn) and zirconium (Zr); and wherein the amount of zirconium in the topmost dielectric layer comprises at least 10 atomic percent zirconium.

2. The coated glass pane according to claim 1, wherein the topmost dielectric layer based on an oxide of zinc (Zn) and tin (Sn) and zirconium (Zr) comprises at most 35 atomic % zirconium.

3. The coated glass pane according to claim 1, wherein the barrier layer is in direct contact with the silver-based functional layer.

4. The coated glass pane according to claim 1, wherein the lower anti-reflection layer comprises in sequence from the glass substrate either; a layer based on an oxide of zinc (Zn) and tin (Sn) and/or an oxide of tin (Sn); a separation layer; and a top layer based on an oxide of zinc (Zn), or, a layer based on an oxide of zinc (Zn) and tin (Sn) and/or an oxide of tin (Sn); and a top layer based on an oxide of zinc (Zn).

5. The coated glass pane according to claim 4, wherein the separation layer comprises: a metal oxide; and/or an (oxi)nitride of silicon and/or an (oxi)nitride of aluminium and/or alloys thereof.

6. The coated glass pane according to claim 4, wherein the lower anti-reflection layer further comprises: a base layer based on an (oxi)nitride of silicon and/or an (oxi)nitride of aluminium and/or alloys thereof, located between the glass substrate and the layer based on an oxide of zinc (Zn) and tin (Sn) and/or an oxide of tin (Sn).

7. The coated glass pane according to claim 6, wherein the base layer based on an (oxi)nitride of silicon and/or an (oxi)nitride of aluminium and/or alloys thereof has a thickness of from 20 to 40 nm.

8. The coated glass pane according to claim 4, wherein the layer based on an oxide of zinc (Zn) and tin (Sn) and/or an oxide of tin (Sn) of the lower anti-reflection layer has a thickness of from 0.5 to 10 nm.

9. The coated glass pane according to claim 6, wherein the layer based on an oxide of zinc (Zn) and tin (Sn) and/or an oxide of tin (Sn) of the lower anti-reflection layer is located directly on the base layer based on an (oxi)nitride of silicon and/or an (oxi)nitride of aluminium.

10. The coated glass pane according to claim 5, wherein the separation layer based on a metal oxide and/or an (oxi)nitride of silicon and/or an (oxi)nitride of aluminium and/or alloys thereof has a thickness of from 0.5 to 5 nm, and, wherein when the separation layer is based on a metal oxide, said metal oxide separation layer is selected from the group consisting of: Ti, Zn, NiCr, InSn, Zr, Al and/or Si.

11. The coated glass pane according to claim 5, wherein the separation layer further includes one or more other chemical elements chosen from at least one of the following elements: Ti, V, Mn, Co, Cu, Zn, Zr, Hf, Al, Nb, Ni, Cr, Mo, Ta, Si, or from an alloy based on at least one of these materials.

12. The coated glass pane according to claim 4, wherein the top layer of the lower anti-reflection layer, based on an oxide of zinc (Zn), comprises a thickness of from 4 to 10 nm.

13. The coated glass pane according to claim 1, wherein the silver-based functional layer has a thickness of from 5 to 20 nm.

14. The coated glass pane according to claim 4, wherein the top layer based on an oxide of Zn in the lower anti-reflection layer is in direct contact with the silver-based functional layer.

15. The coated glass pane according to claim 1, wherein the barrier layer has a thickness of from 1 to 10 nm, and wherein, the barrier layer comprises a layer based on an oxide of zinc (Zn) or, the barrier layer comprises NiCrOx.

16. The coated glass pane according to claim 1, wherein the upper dielectric layer comprises: i) a layer based on an oxide of zinc (Zn) and tin (Sn) and/or an oxide of tin (Sn); ii) a layer based on an oxide of zinc (Zn); and iii) a layer based on an (oxi)nitride of silicon and/or an (oxi)nitride of aluminium.

17. The coated glass pane according to claim 16, wherein the thickness of the layer based on an oxide of zinc (Zn) and (Sn) and/or an oxide of tin (Sn) in the upper dielectric layer is in the range 1 to 10 nm and, wherein the thickness of the layer based on an oxide of zinc (Zn) in the upper dielectric layer is in the range 1 to 10 nm, and, wherein the thickness of the layer based on an (oxi)nitride of silicon and/or an (oxi)nitride of aluminium in the upper dielectric layer is in the range 20 to 40 nm.

18. The coated glass pane according to claim 1, wherein the topmost dielectric layer based on an oxide of zinc (Zn) and tin (Sn) comprises 15 to 35 atomic % zirconium.

19. The coated glass pane according to claim 1, wherein the pane comprises more than one silver-based functional layer, and, wherein each silver-based functional layer is spaced apart from an adjacent silver-based functional layer by an intervening central anti-reflection layer.

20. The coated glass pane according to claim 4, wherein when the separation layer in the lower anti-reflection layer is based on a metal oxide, said metal oxide comprises an oxide of zinc (Zn) and/or an oxide of titanium (Ti).

21. A method of manufacturing a coated glass pane in accordance with claim 1, comprising: i) providing a glass substrate; ii) providing a lower anti-reflection layer; iii) providing a silver-based functional layer; iv) providing a barrier layer; and v) providing an upper dielectric layer; and vi) providing a topmost dielectric layer which comprises an oxide of zinc (Zn), tin (Sn) and zirconium (Zr); and wherein the amount of zirconium in the topmost dielectric layer comprises at least 10 atomic percent zirconium; and wherein any portion of the barrier layer that is in direct contact with the silver-based functional layer is deposited by sputtering in an atmosphere with less than 5 volume percent oxygen.

22. A multiple glazing unit incorporating a coated glass pane in accordance with claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the present invention will now be described herein, by way of the non-limiting examples and with reference to FIGS. 1 and 2.

(2) FIG. 1 is an atomic force microscope (AFM) image of the topmost surface of comparative example 1.

(3) FIG. 2 is an atomic force microscope (AFM) image of the topmost surface of example 4 which comprises ZnSnZrOx with 29 atomic percent zirconium (at. % Zr).

DETAILED DESCRIPTION OF THE INVENTION

(4) Embodiments of the present invention will now be described herein, by way of example only:

(5) 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.

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

(7) 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.

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

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

(10) 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.sup.−5 mbar.

(11) The barrier layers of Al-doped zinc oxide (ZnO:Al) (also referred to as ZAO), located above the silver-based functional layers, were sputtered from conductive ZnOx:Al targets in a pure Argon (Ar) sputter atmosphere without added oxygen.

(12) The layers of mixed silicon aluminium nitride (Si.sub.90Al.sub.10N.sub.x) were reactively sputtered from mixed Si.sub.90Al.sub.10 targets in an Argon/Nitrogen (Ar/N.sub.2) sputter atmosphere containing only residual oxygen.

(13) The layers of AlN were reactively sputtered from an Al target in an Argon/Nitrogen (Ar/N.sub.2) sputter atmosphere containing only residual oxygen.

(14) TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Comparative Comparative Comparative Example 4 Example 5 Si.sub.90Al.sub.10N.sub.x Si.sub.90Al.sub.10N.sub.x Si.sub.90Al.sub.10N.sub.x Si.sub.90Al.sub.10N.sub.x Si.sub.90Al.sub.10N.sub.x (33) (33) (33) (33) (33) ZnSnO.sub.x (4) ZnSnO.sub.x (4) ZnSnO.sub.x (4) ZnSnO.sub.x (4) ZnSnO.sub.x (4) TiO.sub.x (2) TiO.sub.x (2) TiO.sub.x (2) TiO.sub.x (2) TiO.sub.x (2) ZnO:Al (7) ZnO:Al (7) ZnO:Al (7) ZnO:Al (7) ZnO:Al (7) Ag (9) Ag (9) Ag (9) Ag (9) Ag (9) ZnO:Al (2) ZnO:Al (2) ZnO:Al (2) ZnO:Al (2) ZnO:Al (2) ZnSnO.sub.x (2) ZnSnO.sub.x (2) ZnSnO.sub.x (2) ZnSnO.sub.x (2) ZnSnO.sub.x (2) ZnO:Al (4) ZnO:Al (4) ZnO:Al (4) ZnO:Al (4) ZnO:Al (4) Si.sub.90Al.sub.10N.sub.x Si.sub.90Al.sub.10N.sub.x Si.sub.90Al.sub.10N.sub.x Si.sub.90Al.sub.10N.sub.x Si.sub.90Al.sub.10N.sub.x (25) (25) (25) (25) (25) ZnSnO.sub.x (8) ZnSnO.sub.x (8) ZnSnZrO.sub.x ZnSnZrO.sub.x (12) (12) ZrO.sub.x (4) ZrO.sub.x (12) Outer-most 33 at. % Zn, 34% Zr 34% Zr 29 at. % Zr 21 at. % Zr layer metal 15 at. % Sn 3 at. % Zn 10 at. % Zn content 3 at. % Sn 7 at. % Sn Sliding 45 36 43 33-37 41 angle (°) Scratch 0.3 0.8 1.3 1.2 1.0 load (N) T.sub.L 87.2 87.7 87.6 87.2 87.5 ΔT.sub.L 3.0 2.2 2.2 2.1 2.1 Rs AD 6.65 5.82 6.21 6.22 5.77 (ohm/sq) Rs HT 4.26 — 4.74 4.11 3.78 (ohm/sq) ΔRs 2.4 — 1.5 2.1 2 (ohm/sq) T ΔE* 1.39 1.24 1.35 1.10 1.13 Oil-rub 0 3 2 3 6 Hazescan 68 94 75 70 70

(15) TABLE-US-00002 TABLE 2 Example 6 Example 7 Example 8 Comparative Comparative Comparative Example 9 SiNx (28) SiNx (28) SiNx (28) SiNx (28) ZnSnOx (4) ZnSnOx (4) ZnSnOx (4) ZnSnOx (4) ZnOx (8) ZnOx (8) ZnOx (8) ZnOx (8) Ag (7.3) Ag (7.3) Ag (7.3) Ag (7.3) NiCrOx (1) NiCrOx (1) NiCrOx (1) NiCrOx (1) ZAO (5) ZAO (5) ZAO (5) ZAO (5) AlNx (50) AlNx (50) AlNx (50) AlNx (50) ZnSnOx (21) ZnSnOx (21) ZnSnOx (21) ZnSnOx (21) ZnOx (8) ZnOx (8) ZnOx (8) ZnOx (8) Ag (16.5) Ag (16.5) Ag (16.5) Ag (16.5) NiCrOx (1) NiCrOx (1) NiCrOx (1) NiCrOx (1) WNx (4) WNx (4) WNx (4) WNx (4) AlNx (16) AlNx (16) AlNx (16) AlNx (16) ZnSnOx (9) ZnSnOx (5) ZnSnZrOx (9) ZrOx (9) ZrOx (4) Outer-most No data 34% Zr 34% Zr 29 at. % Zr layer metal 3 at. % Zn content 3 at. % Sn Sliding 26 28 25 24 angle (°) Scratch 5 4 3 3 load (N) T.sub.L 47.8 48.4 47.7 48.5 ΔT.sub.L 6.3 6.1 6.9 5.8 Rs AD 3.01 2.92 3.19 2.87 (ohm/sq) Rs HT 2.04 1.97 2.07 1.96 (ohm/sq) ΔRs 0.97 0.95 0.91 0.91 (ohm/sq) T ΔE* 8.5 7.8 11.4 6.7 Oil-rub 5 9 6 4 Hazescan 92 56 81 62

(16) TABLE-US-00003 TABLE 3 Example 13 Example 14 Example 10 Example 11 Example 12 (1 kW (2.5 kW Comparative Comparative Comparative ZrOx) ZrOx) SiNx (20) SiNx (20) SiNx (20) SiNx (20) SiNx (20) ZnSnOx (4) ZnSnOx (4) ZnSnOx (4) ZnSnOx (4) ZnSnOx (4) ZnOx (8) ZnOx (8) ZnOx (8) ZnOx (8) ZnOx (8) Ag (9.8) Ag (9.8) Ag (9.8) Ag (9.8) Ag (9.8) NiCrOx (1) NiCrOx (1) NiCrOx (1) NiCrOx (1) NiCrOx (1) ZAO (5) ZAO (5) ZAO (5) ZAO (5) ZAO (5) AlNx (41) AlNx (41) AlNx (41) AlNx (41) AlNx (41) ZnSnOx (17) ZnSnOx (17) ZnSnOx (17) ZnSnOx (17) ZnSnOx (17) ZnOx (9) ZnOx (9) ZnOx (9) ZnOx (9) ZnOx (9) Ag (12.5) Ag (12.5) Ag (12.5) Ag (12.5) Ag (12.5) NiCrOx (1) NiCrOx (1) NiCrOx (1) NiCrOx (1) NiCrOx (1) ZAO (5) ZAO (5) ZAO (5) ZAO (5) ZAO (5) AlNx (22) AlNx (22) AlNx (22) AlNx (22) AlNx (22) ZnSnOx (7) ZnSnOx (3) ZnSnZrOx (7) ZnSnZrOx (7) ZrOx (7) ZrOx (4) Outer-most No data 34% Zr 34% Zr 21 at. % Zr 29 at. % Zr layer metal 10 at. % Zn 3 at. % Zn content 7 at. % Sn 3 at. % Sn Sliding 30 29 25 25 24 angle (°) Scratch 8 4 4 7 8 load (N) T.sub.L 69.1 70.7 71.3 74.1 71.1 ΔTL 12.9 11.8 11.1 7.6 11.1 Rs AD 4.77 4.39 4.25 3.81 4.44 (ohm/sq) Rs HT 2.43 2.41 2.38 2.32 2.37 (ohm/sq) ΔRs 2.34 1.98 1.87 1.49 2.07 (ohm/sq) T ΔE* 5.60 5.16 4.89 3.44 4.87 Oil-rub 2 3 3 3 1 Hazescan 77 130 130 111 95

(17) Tables 1, 2 and 3 provide details of the layer sequences for a number of comparative coated glass panes and coated glass panes according to the present invention along with the results of each stack tested for: outermost layer metal content, hazescan, oil rub test value, sliding angle test value, scratch load test value, T.sub.L%—percentage (%) light transmittance value for the glass substrate before heat treatment, ΔT.sub.L—the change in percentage (%) light transmittance upon heat treatment, Rs AD—sheet resistance before heat treatment, Rs HT—sheet resistance after heat treatment, Δ Rs (ohm/square)—change is heat resistance, and T ΔE*—which is a measure of the change in transmitted colour upon heat treatment.

(18) The methodology used to collect the data in Tables 1, 2 and 3 is set out below. For each example, the layers were deposited on to a glass pane in the sequence shown starting with the layer at the top of each column.

(19) Oil rub test—an oil rub test serves to simulate the influence of cutting oils used for cutting glass panes on the mechanical robustness of a coating. Coated glass panes that do not withstand an oil rub test are difficult to process and are unsuitable for most practical applications. The coated samples defined in Tables 1, 2 and 3 were rubbed using a felt pad with an area 1.2×1.2 cm soaked in microscope oil of refractive index 1.52 (1.515 to 1.517). The samples are subjected to 500 cycles with a 1,000 g load at a speed of 37 cycles per minute. The oil rubbed samples were then evaluated using an internal evaluation system on a perfectness scale of 0 (perfect, no damage) to 9 (part of coating stack completely removed). A score of 6 or less is preferred.

(20) Heat treatability tests—immediately after deposition of all of the coatings in each example, the coating stack parameters (such as hazescan, sheet resistance (Rs), light transmittance (T.sub.L)) and colour co-ordinates for the coated glass panes were measured. The samples were then heat treated in the region of 650° C. for 5 minutes. Thereafter, the hazescan value, sheet resistance (Rs), percentage light transmittance (T.sub.L) and colour coordinates were again measured and the change in light transmittance (ΔT.sub.L), and the change in transmission colour upon heat treatment (T ΔE*), calculated therefrom. The measured results are also provided in Tables 1, 2 and 3 above.

(21) The values stated for the change in percentage (%) light transmittance upon heat treatment (ΔT.sub.L) of the coated glass panes in Examples 1 to 14 were derived from measurements according to EN 140, the details of which are incorporated herein by reference.

(22) Sheet Resistance/Change in sheet resistance—sheet resistance measurements were made using a NAGY SRM-12 for examples 1 to 14. This device utilises an inductor to generate eddy currents in a 100 m×100 mm coated sample. This produces a measureable 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.

(23) Colour characteristics—the colour characteristics for each of sample 1 to 14 were measured and reported using the well-established CIE LAB L*, a*, b* coordinates (as described for example in paragraphs [0030] and [0031] of WO 2004/063111A1, incorporated herein by reference). The change in transmission colour upon heat treatment, T ΔE*=((Δa*).sup.2+(Δb*).sup.2+(ΔL*).sup.2).sup.112, wherein ΔL*, Δa* and Δb* are the differences of the colour values L*, a*, b* of the coated glass pane each before and after a heat treatment. ΔE* 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 no noticeable colour modification caused by the heat treatment. For layer sequences comprising two or more silver-based functional layer, lower T ΔE* values provide an indication of the stability of the sequences; the lower the T ΔE* values the more superior the results and appearance of the coated glass pane.

(24) Hazescan—A haze scoring system was applied to each of Examples 1 to 14. The quality assessment evaluation system described herein 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 1003-61.

(25) 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.

(26) 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. 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.

(27) AFM analysis—an atomic force microscope (AFM) was used in Peak Force Tapping mode with ScanAsyst (PFTSA) to determine the topography of a range of examples including examples 1, 2 and 4 from Table 1, along with examples 15 and 16 for which the concentration of zirconium in the uppermost layer was varied as indicated in Table 4. The mode of imaging the samples used a probe consisting of a silicon nitride cantilever with a silicon tip (radius around 2 nm). The results of the analysis are provided in Table 4.

(28) In Table 4, Sa is the arithmetical mean height, Sq is the root mean square height, Sz (or Z-range) is the maximum peak to valley distance, Sdr (or surface area difference) is the surface area of the ‘scanned’ surface relative to the area of the projected flat x, y plane.

(29) It can be seen from the results in Table 4 that examples 15 and 16 were found to be smoother in terms of all three parameters (Sa, Sq, Sz) than comparative examples 1 and 2. Also, it can be seen that reducing the amount of zirconium (Zr) in the outermost layer is detrimental to the smoothness of the uppermost layer.

(30) TABLE-US-00004 TABLE 4 Sa Sq Sz Sdr (nm) (nm) (nm) (%) Example 1 (ZnSnOx top) - Comparative 0.48 0.61 5.7 2.1 Example 2 (Thin ZrOx top) - Comparative 0.45 0.56 6.4 1.2 Example 4 (ZnSnZrOx top) - 29 atomic % 0.32 0.41 3.8 0.4 Zirconium (Zr) Example 15 (ZnSnZrOx top) - 27 atomic % 0.37 0.47 5.4 0.8 Zirconium (Zr) Example 16 (ZnSnZrOx top) - 12 atomic % 0.49 0.64 7.1 1.5 Zirconium (Zr)

(31) As can be seen also from a comparison of FIGS. 1 and 2 in relation to examples 1 and 4 respectively, the topography of the topmost dielectric surface for example 4 for ZnSnZrOx with 29 atomic percent zirconium (at. % Zr) has a maximum height of 2.9 nm. In contrast, the topography of the topmost surface of example 1 with a ZnSnOx dielectric top layer has a maximum height of 4.5 nm, that is, an improvement in peak height when using a topmost dielectric of ZnSnZrOx of over 30%.

(32) XPS analysis—X-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 μA, and rastered over a 2.0×4.0 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 μm.

(33) 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.

(34) Summary of Results

(35) Comparative Example 1 comprises a stack with an uppermost layer of ZnSnOx, that is, a topmost dielectric layer devoid of zirconium. Comparative Example 1 exhibits good performances in terms of hazescan value and mechanical robustness tests.

(36) Comparative Example 2 has an arrangement in which the uppermost dielectric layers of the stack comprise ZnSnO.sub.x and ZrOx. This change results in an increase in the hazescan value and a deterioration of the robustness in terms of the oil rub test.

(37) Comparative Example 3 adds a ZrO.sub.x layer as the uppermost dielectric layer. The oil rub test results are improved compared to comparative example 2, and the hazescan value results are comparable with example 1.

(38) Example 4 according to the present invention comprises a layer of ZnSnZrOx as the uppermost layer of the stack, with a zirconium content of 29 atomic percent (at. %). The hazescan value for example 4 is comparable to examples 1 and 3. Example 4 provides an improvement in terms of the scratch load and also the change in light transmittance after heat treatment. Example 4 also provides an improvement in terms of the change in transmission colour upon heat treatment (T ΔE*)

(39) Example 5, also according to the present invention comprises a layer of ZnSnZrOx as the uppermost layer of the stack, with a Zirconium content of 21 atomic percent (at. %). The hazescan value for example 5 is comparable to that for example 4 as well as examples 1 and 3. Example 5 also demonstrates an improvement in terms of the scratch load over comparative examples 1, 2 and 3 as well as the change in light transmittance after heat treatment. Example 5 also provides an improvement in terms of the change in film side reflection colour upon heat treatment (T ΔE*).

(40) In Table 2 there is provided the results for a series of coated glass panes comprising two layers of silver. Examples, 6, 7 and 8 are comparative examples comprising an uppermost layer of ZnSnOx, ZrOx, or ZnSnOx and ZrOx respectively.

(41) For example 9 according to the present invention, it can be seen that for a coating with two silver-based functional layers which also comprises a layer of ZnSnZrOx as the uppermost layer of the stack, with a zirconium content of 29 atomic percent (at. %), the example provides an improved sheet resistance after heat treatment and an improved oil rub test score. Example 9 also provides an improvement in terms of the change in film side reflection colour upon heat treatment (T ΔE*) as with example 4.

(42) In Table 3 there is again provided results for a series of coated glass panes comprising two silver-based functional layers but in which the tungsten nitride layer (WNx) in the upper dielectric layer in examples 6, 7, 8 and 9 have been replaced by a layer of ZAO. In comparative Examples, 10, 11 and 12, the uppermost layer comprises ZnSnOx, ZrOx, or ZnSnOx and ZrOx respectively.

(43) For examples 13 and 14 according to the present invention it can be seen that for the coated glass panes comprising two silver-based functional layers with a layer of ZnSnZrOx as the uppermost layer, there is an improvement in the scratch load, and the change in light transmission value after heat treatment compared to examples 11 and 12. The sheet resistance after heat treatment is also improved for examples 13 and 14 compared with examples 10, 11 and 12.

(44) Therefore it can be seen from the above results that the coated glass panes of the present invention provide good heat treatability and mechanical durability, with an uppermost dielectric layer based on an oxide of zinc (Zn), tin (Sn) and zirconium (Zr); and wherein the amount of zirconium in the layer comprises at least 10 atomic percent zirconium.

(45) The coated glass panes 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.