COATED GLASS PANE

Abstract

The present invention relates to a transparent substrate comprising a multiple layer coating stack and the use of same in the manufacture of a double glazing unit, wherein the multiple layer coating stack comprises, n functional metal layer, m; and n plus 1 (n+1) dielectric layer, d, wherein the dielectric layers are positioned before and after each functional metal layer, and wherein n is the total number of functional metal layer in the stack counted from the substrate and is greater than or equal to 3; and wherein each dielectric layer comprises one or more layers, characterized in that the geometrical layer thickness of each functional metal layer in the coating stack Gm, is greater than the geometrical layer thickness of each functional metal layer appearing before it in the multiple layer coating stack, that is, Gmi+1>Gm.sub.i wherein i is the position of the functional metal layer in the coating stack counted from the substrate, and wherein for each dielectric layer d located before and after each functional metal layer m, the optical layer thickness of each dielectric layer (opln) is greater than or equal to the optical layer thickness of the dielectric layer (opln−1) positioned before it in the coating stack with the proviso that: twice the optical layer thickness of the first dielectric layer (opl.sub.1) in the coating stack, is less than the optical layer thickness of the second dielectric layer (opl.sub.2) in the coating stack, that is, (2×opl.sub.1)<opl.sub.2; and twice the optical layer thickness of the last dielectric layer (opl.sub.n+1) in the coating stack, is greater than the thickness of the optical layer thickness of the penultimate dielectric layer (opl.sub.n), that is, (opl.sub.n)<(opl.sub.n+1)×2.

Claims

1.-23. (canceled)

24. A transparent substrate comprising a multiple layer coating stack, wherein the coating stack comprises: i) n functional metal layer, m; and ii) n plus 1 (n+1) dielectric layer, d, wherein the dielectric layers are positioned before and after each functional metal layer, and wherein n is the total number of functional metal layer in the stack counted from the substrate and is greater than or equal to 3; and wherein each dielectric layer comprises one or more layers, characterized in that: the geometrical layer thickness of each functional metal layer in the multiple layer coating stack Gm, is greater than the geometrical layer thickness of each functional metal layer appearing before it in the multiple layer coating stack, that is,
Gm.sub.i+1>Gm.sub.i, wherein i is the position of the functional metal layer in the multiple layer coating stack counted from the substrate, and wherein, for each dielectric layer d located before and after each functional metal layer m, the optical layer thickness of each dielectric layer (opl.sub.n) is greater than or equal to the optical layer thickness of the dielectric layer (opl.sub.n−1) positioned before it in the coating stack with the proviso that: twice the optical layer thickness of the first dielectric layer (opl.sub.1) in the coating stack, is less than the optical layer thickness of the second dielectric layer (opl.sub.2) in the coating stack, that is, (2× opl.sub.1)<opl.sub.2; and twice the optical layer thickness of the last dielectric layer (opl.sub.n+1) in the coating stack, is greater than the thickness of the optical layer thickness of the penultimate dielectric layer (opl.sub.n), that is, (opl.sub.n)<(opl.sub.n+1)×2.

25. The transparent substrate according to claim 24, wherein the functional metal layer comprises silver.

26. The transparent substrate according to claim 24, wherein the number of functional metal layers n, in the multiple layer coating stack comprises from 3 to 6.

27. The transparent substrate according to claim 24, wherein the number of functional metal layers in the multiple layer coating stack comprises 4.

28. The transparent substrate according to claim 24, wherein each dielectric layer comprises one or more layers of material selected from: TiOx, SnO.sub.2, ZnO, ZAO, ZnO:Al, ZrOx, TiOx, Nb.sub.2O.sub.5, Ta.sub.2O.sub.5, In.sub.2O.sub.3, Al.sub.2O.sub.3, SiO.sub.2 or alloys or mixtures thereof, including ZnSnOx, InSnOx, and/or an (oxi)nitride of silicon and/or an (oxi)nitride of aluminium and/or alloys thereof.

29. The transparent substrate according to claim 24, wherein the multiple layer coating stack comprises: a first dielectric layer, d.sub.1; a first functional metal layer m.sub.1; a second dielectric layer, d.sub.2; a second functional metal layer m.sub.2; a third dielectric layer, d.sub.3; a third functional metal layer m.sub.3; a fourth dielectric layer d.sub.4.

30. The transparent substrate according to claim 24, wherein the multiple layer coating stack comprises: a first dielectric layer, d.sub.1; a first functional metal layer m.sub.1; a second dielectric layer, d.sub.2; a second functional metal layer m.sub.2; a third dielectric layer, d.sub.3; a third functional metal layer m.sub.3; a fourth dielectric layer d.sub.4; a fourth functional metal layer m.sub.4; a fifth dielectric layer, d.sub.5.

31. The transparent substrate according to claim 24, wherein each functional metal layer comprises a thickness of between 5 and 25 nm.

32. The transparent substrate according to claim 29, wherein the first dielectric layer d.sub.1 comprises in sequence from the glass substrate; a layer based on an oxide of titanium (Ti), and/or a layer based on an oxide of zinc (Zn).

33. The transparent substrate according to claim 29, wherein the second, third, fourth and fifth dielectric layers d.sub.2, d.sub.3, d.sub.4 and d.sub.5 each comprise in sequence from the glass substrate; i) a layer based on an oxide of zinc (Zn); and ii) a layer based on an oxide of zinc (Zn) and tin (Sn), and/or an oxide of tin (Sn).

34. The transparent substrate according to claim 33, wherein the third dielectric layer d.sub.3, further comprises a layer based on an oxide of titanium (Ti).

35. The transparent substrate according to claim 30, wherein the fifth dielectric layer d.sub.5, further comprises a layer based on an oxide of zirconium (Zr).

36. The transparent substrate according to claim 29, wherein the optical layer thickness of the first dielectric layer d.sub.1, is the range 30-70 nm.

37. The transparent substrate according to claim 29, wherein the optical layer thickness of the second dielectric layer d.sub.2, is the range 60-180 nm.

38. The transparent substrate according to claim 29, wherein the optical layer thickness of the third dielectric layer d.sub.3, is the range 70-200 nm.

39. The transparent substrate according to claim 29, wherein the optical layer thickness of the fourth dielectric layer d.sub.4, is the range 80-220 nm.

40. The transparent substrate according to claim 29, wherein the optical layer thickness of the fifth dielectric layer d.sub.5, is the range 45-120.

41. The transparent substrate according to claim 29, wherein the coating stack further comprises one or more layer based on NiCr.

42. The transparent substrate according to claim 41, wherein the or each layer based on NiCr is in direct contact with one or more silver functional layer.

43. A double glazing unit incorporating a transparent substrate with a multiple layer coating stack according to claim 24.

44. The double glazing unit according to claim 43, wherein the angular dependence for a* and b* outside reflection from 0° to 60° comprises less than or equal to 5; more preferably less than or equal to 4.0; most preferably less than or equal to 3.0.

45. The double glazing unit according to claim 43, further comprising a colour shift with thickness variation of 3% for one layer of less than or equal to 5; more preferably less than or equal to 4.0; most preferably less than or equal to 3.0.

46. The double glazing unit according to claim 43, further comprising a selectivity of greater than or equal to 1.9, more preferably greater than or equal to 2.0, and most preferably greater than or equal 2.1.

Description

[0119] Embodiments of the present invention will now be described herein, by way of the non-limiting examples and with reference to FIGS. 1 to 5 in which:

[0120] FIG. 1 is a cross section view of a double glazing unit.

[0121] FIG. 2 is a graphical representation of the angular dependence (in degrees) of the outside reflection of a standard double glazing unit (DGU) versus b* and prepared with a coated glass according to example 1.

[0122] FIG. 3 is a graphical representation of the angular dependence (in degrees) of the outside reflection of a standard double glazing unit (DGU) versus b* prepared with a coated glass according to example 2.

[0123] FIG. 4 is a graphical representation of the angular dependence (in degrees) of the outside reflection of a standard double glazing unit (DGU) versus a* prepared with a coated glass according to example 3.

[0124] FIG. 5 is a graphical representation of the angular dependence (in degrees) of the outside reflection of a standard double glazing unit (DGU) versus a* prepared with a coated glass according to example 4.

[0125] In FIGS. 2 and 3, b* represents the change in colour from blue to yellow according to the CIE LAB colour space, and in FIGS. 4 and 5, a* represents the change in colour from green to red according to the CIE LAB colour space.

[0126] For the following examples, details of which are provided in Table 1, the coatings were deposited on 6 mm thick standard float glass pane 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.

[0127] 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.

[0128] Titanium oxide (TiOx) layers were deposited from a metallic titanium (Ti) or conductive oxide titanium (TiO.sub.x) target in an argon/oxygen (Ar/O.sub.2) sputter atmosphere.

[0129] The ZnO:Al growth promoting layers were sputtered from Al-doped zinc metallic targets (aluminium (Al) content about 2 weight %) in an Ar/O.sub.2 sputter atmosphere.

[0130] The functional layers that in all examples consisted of essentially pure silver (Ag) were sputtered from silver targets in an argon (Ar) sputter atmosphere without any added oxygen and at a partial pressure of residual oxygen below 10.sup.−4 mbar.

[0131] The barrier layers of Al-doped zinc oxide also referred to as ZAO, located above the silver-based functional layers, were sputtered from conductive oxide targets, ZnO.sub.x:Al targets in a pure Argon (Ar) sputter atmosphere without added oxygen.

[0132] The layers of NiCr (which may serve as absorbing and/or barrier layers) located directly above the silver-based functional layers, were sputtered from a metallic NiCr-target in a pure Argon sputter atmosphere.

TABLE-US-00001 TABLE 1 In the table the geometrical layer thicknesses provided are in nm. Example 2 Example 3 Layer Example 1 (Comparative) (Comparative) Example 4 1 TiO.sub.x (19) TiO.sub.x (33) TiO.sub.x (22) TiO.sub.x (22.5) 2 ZnO:Al (3.5) 3 Ag (9.3) Ag (14) Ag (11.3) Ag (8.9) 4 ZAO (2) ZAO (2) ZAO (2) ZAO (2) 5 ZnSnO.sub.x (66) ZnSnO.sub.x (73) ZnSnO.sub.x (80) ZnSnO.sub.x (66) 6 Ag (11.5) Ag (14) Ag (14.6) Ag (12) 7 ZAO (2) ZAO (2) ZAO (2) ZAO (2) 8 ZnSnO.sub.x (31) ZnSnO.sub.x (38) ZnSnO.sub.x (25) ZnSnO.sub.x (35) 9 TiO.sub.x (29) TiO.sub.x (30) TiO.sub.x (33) TiO.sub.x (30.5) 10 ZnO:Al (3.5) 11 Ag (15.6) Ag (14) Ag (15) Ag (14.5) 12 ZAO (2) ZAO (2) ZAO (2) NiCr (0.3) 13 ZnSnO.sub.x (77) ZnSnO.sub.x (63) ZnSnO.sub.x (62) ZnSnO.sub.x (79) 14 Ag (17.4) Ag (14) Ag (15.5) Ag (16.9) 15 ZAO (2) ZAO (2) ZAO (2) NiCr (0.8) 16 ZnSnO.sub.x (41) ZnSnO.sub.x (37) ZnSnO.sub.x (17) ZnSnO.sub.x (41) Substrate 6 mm 6 mm 6 mm 6 mm thickness Properties T.sub.L 59 54 47 50 g-value 27 26 22 23 Selectivity 2.18 2.07 2.13 2.17 Δa*, 0°-60° 1 3.9 12.1 2.2 Δb*, 0°-60° 2.9 9.4 1.7 2.5 Δa*, 3% 2.5 6.2 10.6 2.9 Δb*, 3% 2.8 8.0 3.2 2.3

[0133] Table 1 provides details of the layer sequences for comparative coated glass panes and coated glass panes according to the present invention along with the results for each layer sequence in terms of:

[0134] Light transmission (T.sub.L), g-value, Selectivity, colour shift Δa*, Δb* under angular 0°-60° measurement and colour shift Δa*, Δb* for a thickness variation of 3%. All values are for a double glazing unit (DGU). The colour shift is always the shift of the outside reflection. For each example, the layers were deposited onto a 6 mm float glass pane in the sequence shown starting with the layer at the top of each column.

[0135] Colour characteristics—the colour characteristics for each sample 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).

[0136] In the following the examples in which the optical layer thickness of the coating is provided, the optical layer thickness is determined using a refractive index value of 2.45 for TiOx, a refractive index of 2.07 for ZnO:Al, ZAO and a refractive index of 2.07 for ZnSnOx.

Example 1

[0137] The coating sequence described in Example 1 was prepared as follows. Onto a 6 mm float glass pane a first titanium oxide (TiO.sub.x) layer was applied to form a first dielectric coating sequence with an optical layer thickness opl.sub.1 of 46.6 nm. Atop the titanium oxide (TiO.sub.x) layer was then applied a layer of aluminium doped zinc oxide (ZnO:Al) with an optical thickness 7.3 nm. Consequently, a first dielectric layer is formed with an optical thickness opl.sub.1 of 53.9 nm. Atop the ZnO:Al layer was then applied a first silver functional layer (Ag layer 1) to a coating thickness of 9.3 nm. A barrier layer of aluminium-doped zinc oxide (ZAO) with an optical layer thickness of 4.1 nm was then deposited on the first silver functional layer (Ag layer 1) to protect the first silver functional layer against the subsequent second coating layer sequence of tin and zinc oxide (ZnSnO.sub.x) applied with an optical layer thickness of 136.6 nm. Consequently, a second dielectric layer sequence was formed comprising a layer of tin and zinc oxide (ZnSnO.sub.x) and aluminium-doped zinc oxide (ZAO) with a combined optical layer thickness opl.sub.2 of 140.7 nm. Next a second silver functional layer (Ag layer 2) was applied above the second dielectric layer, with a thickness of 11.5 nm. This was followed again by second barrier layer of aluminium-doped zinc oxide (ZAO) with an optical layer thickness of 4.1 nm applied above the second silver functional layer (Ag layer 2). The second barrier layer of aluminium-doped zinc oxide (ZAO) was then coated with a second dielectric coating layer of tin and zinc oxide (ZnSnO.sub.x), with an optical layer thickness of 64.2 nm. A second titanium oxide (TiO.sub.x) layer was applied to form a coating with an optical layer thickness of 71.1 nm. A second aluminium doped zinc oxide (ZnO:Al) was coated on the titanium oxide with an optical thickness of 7.3 nm, to complete a third dielectric layer sequence formed from a layer of aluminium-doped zinc oxide (ZAO), a layer of tin and zinc oxide (ZnSnO.sub.x), a layer of titanium oxide (TiO.sub.x), and an aluminium doped zinc oxide layer (ZnO:Al) comprising an optical layer thickness opl.sub.3 of 146.7 nm. Above the third dielectric layer sequence was then applied a third silver functional layer (Ag layer 3) with a thickness of 15.6 nm. Again, a layer of aluminium-doped zinc oxide (ZAO) with an optical layer thickness of 4.1 nm was applied atop the third silver functional layer (Ag layer 3), and above the third layer of aluminium-doped zinc oxide (ZAO) was applied a third layer of tin and zinc oxide (ZnSnO.sub.x) with an optical layer thickness of 159.4 nm to form a fourth dielectric layer sequence, with a combined optical layer thickness, opl.sub.4 of 163.5 nm. A fourth silver functional layer (Ag layer 4) with a thickness of 17.4 nm was then applied above the third layer of tin and zinc oxide (ZnSnO.sub.x). Again, a layer of aluminium-doped zinc oxide (ZAO) with an optical layer thickness of 4.1 nm was deposited above the fourth silver functional layer (Ag layer 4). Finally, a fourth layer of tin and zinc oxide (ZnSnO.sub.x) with an optical layer thickness of 82.8 nm was applied above the fourth layer of aluminium-doped zinc oxide (ZAO) to complete the fifth dielectric sequence with a combined optical layer thickness opl.sub.5 of 86.9 nm.

[0138] The layer sequence for example 1 may therefore be expressed in terms of optical layer thickness and geometric layer thickness for the silver function layers as: [0139] glass/TiO.sub.x, opl=46.6 nm/ZnO:Al, opl=7.3 nm/Ag.sub.1 9.3 nm/ZAO, opl=4.1 nm/ZnSnO.sub.x, opl=136.6 nm/Ag.sub.2 11.5 nm/ZAO, opl=4.1 nm/ZnSnO.sub.x, opl=64.2 nm/TiO.sub.x, opl=71.1 nm/ZnO:Al, opl=7.3 nm/Ag.sub.3 15.6 nm/ZAO, opl=4.1 nm/ZnSnO.sub.x 159.4 nm/Ag.sub.4 17.4 nm/ZAO, opl=4.1 nm/ZnSnO.sub.x, opl=82.8 nm,

[0140] The ‘opl’ values expressed above and in relation to the following examples is the optical layer thickness of a material and is based on the product of the refractive index for the material and the geometrical layer thickness of the material measured at a wavelength of 550 nm.

[0141] The optical layer thicknesses for each of the five dielectric layer sequences opl.sub.1 to opl.sub.5 may be summarized as: [0142] opl.sub.1=53.9 nm, opl.sub.2=140.7 nm, opl.sub.3=146.7 nm, opl.sub.4=163.5 nm, opl.sub.5=86.9 nm.

[0143] In addition, in respect of example 1, the thickness of each silver functional layer dAg increases as the distance of the silver functional layer to the glass substrate increases. That is for example, the thickness of the second silver functional layer dAg.sub.2 is greater than the thickness of the first silver functional layer dAg.sub.1.

[0144] Consequently, in respect of Example 1 and according to the present invention, the following relationships are satisfied: [0145] i) with respect to the thicknesses of the silver functional layers,

dAg.sub.1<dAg.sub.2<dAg.sub.3<dAg.sub.4; and [0146] ii) with respect to the thickness of the combined dielectric layer sequences before, after and between each of the silver functional layers,

(opl.sub.1×2)<opl.sub.2<opl.sub.3<opl.sub.4<(opl.sub.5×2)

[0147] A double glazing unit (DGU) (1) as illustrated in FIG. 1 was prepared using a 6 mm glass sheet (2) with a coating (5) as described in example 1. That is, a 6 mm thick float glass sheet (2) with a coating as detailed in example 1 was assembled with a second 4 mm thick uncoated float glass sheet (3). The two sheets of glass (2, 3) were assembled such that the coated side (5) of the coated glass sheet (2) faced the interspace (8) (referred to as position two in the DGU when installed), that is, the coated glass sheet (2) is closer to the external environment (10) than the uncoated glass sheet (3), to form a thermal insulation double-glazing unit. The glass sheets were positioned with an interspace distance of 16 mm between them and, the interspace gap (8) was filled with a 90% argon gas and 10% air filling. The uncoated face (4) of the coated glass sheet (2) was therefore present at position 1, and the two uncoated faces (6) and (7) of the second glass sheet (3) were present at positions 3 and 4 respectively. The properties of the double glazing with the low-e coating at position 2, were measured in accordance with EN 410. The results are as provided in Table 2:

TABLE-US-00002 TABLE 2 Parameter Measured value Light transmittance (T.sub.L) 59 G-value 27 Selectivity 2.18 Δa*, 0°-60° 1.0 Δb*, 0°-60° 2.9 Δa*, 3% 2.5 Δb*, 3% 2.8

[0148] In Table 2, the Selectivity value is equal to the ratio of the light transmission and g-value for the double glazing unit, wherein each value is calculated using EN 410 incorporated herein by reference.

[0149] The difference in the outside reflection of the DGU prepared with the coating of Example 1 according to the present invention for a view angle of 0° and 60°, in terms of a* and b* was found to be for Δa*=1.0 and Δb*=2.9. A graphical representation of the change in b* versus viewing angle for Example 1 is shown in FIG. 2, indicating that the coating used in example 1 is within required limits.

[0150] Also, in relation to the DGU prepared with the coating of Example 1 according to the present invention, the colour shifts with thickness variation of 3% are for Δa*=2.5 and Δb*=2.8. That is, the values for Δa* and Δb* for the DGU prepared using a coating according to the present invention, are within the accepted limit of 5, and are also within the preferred limit of 4, and are even within the especially preferred limit of 3.

Comparative Example 2

[0151] The coating sequence described in Example 2 was prepared as follows. Onto a 6 mm float glass pane a first titanium oxide (TiO.sub.x) layer was applied to form a first dielectric coating sequence opl.sub.1 with an optical layer thickness of 80.9 nm. Atop the titanium oxide (TiO.sub.x) layer was then applied a first silver functional layer (Ag layer 1) to a coating thickness of 14 nm. A barrier layer of aluminium-doped zinc oxide (ZAO) with an optical layer thickness of 4.1 nm was then deposited on the first silver functional layer (Ag layer 1) to protect the first silver functional layer against the subsequent second coating layer sequence of tin and zinc oxide (ZnSnO.sub.x) applied with an optical layer thickness of 151.1 nm. Consequently, a second dielectric layer sequence was formed comprising a layer of tin and zinc oxide (ZnSnO.sub.x) and aluminium-doped zinc oxide (ZAO) with a combined optical layer thickness of 155.2 nm. Next a second silver functional layer (Ag layer 2) was applied above the second dielectric layer, with a thickness of 14 nm. This was followed again by second barrier layer of aluminium-doped zinc oxide (ZAO) with an optical layer thickness of 4.1 nm applied above the second silver functional layer (Ag layer 2). The second barrier layer of aluminium-doped zinc oxide (ZAO) was then coated with a second dielectric coating layer of tin and zinc oxide (ZnSnO.sub.x), with an optical layer thickness of 78.7 nm. A second titanium oxide (TiO.sub.x) layer was applied to form a coating with an optical layer thickness of 73.5 nm, to complete a third dielectric layer sequence opl.sub.3 formed from a layer of aluminium-doped zinc oxide (ZAO), a layer of tin and zinc oxide (ZnSnO.sub.x), and a layer of titanium oxide (TiO.sub.x) and comprising a combined optical layer thickness of 156.3 nm. Above the third dielectric layer sequence was then applied a third silver functional layer (Ag layer 3) with a thickness of 14 nm. Again, a layer of aluminium-doped zinc oxide (ZAO) with an optical layer thickness of 4.1 nm was applied atop the third silver functional layer (Ag layer 3), and above the third layer of aluminium-doped zinc oxide (ZAO) was applied a third layer of tin and zinc oxide (ZnSnO.sub.x) with an optical layer thickness of 130.4 nm to form a fourth dielectric layer sequence, opl.sub.4, with a combined optical layer thickness of 134.6 nm. A fourth silver functional layer (Ag layer 4) with a thickness of 14 nm was then applied above the third layer of tin and zinc oxide (ZnSnO.sub.x). Again, a layer of aluminium-doped zinc oxide (ZAO) with an optical layer thickness of 4.1 nm was deposited above the coated on the fourth silver functional layer (Ag layer 4). Finally, a fourth layer of tin and zinc oxide (ZnSnO.sub.x) with an optical layer thickness of 76.6 nm was applied above the fourth layer of aluminium-doped zinc oxide (ZAO) to complete the fifth dielectric sequence, opl.sub.5, with a combined optical layer thickness of 80.7 nm.

[0152] The layer sequence for Example 2 may therefore be expressed as: [0153] glass/TiO.sub.x, opl=80.9 nm/Ag 14 nm/ZAO, opl=4.1 nm/ZnSnO.sub.x, opl=151.2 nm/Ag 14 nm/ZAO, opl=4.1 nm/ZnSnO.sub.x, opl=78.7 nm/TiO.sub.x, opl=73.5 nm/Ag 14 nm/ZAO, opl=4.1 nm/ZnSnO.sub.x 130.4 nm/Ag 14 nm/ZAO, opl=4.1 nm/ZnSnO.sub.x, opl=76.6 nm,

[0154] The optical layer thicknesses for each of the five dielectric layer sequences opl.sub.1 to opl.sub.5 in comparative Example 2 may be summarized as:

opl.sub.1=80.9 nm, opl.sub.2=155.2 nm, opl.sub.3=156.3 nm, opl.sub.4=134.5 nm, opl.sub.5=80.7 nm.

[0155] Consequently, for comparative Example 2, the following relationship with respect to the thicknesses of the silver functional layers is not satisfied:

dAg.sub.1<dAg.sub.2<dAg.sub.3<dAg.sub.4.

[0156] Instead, with respect to the thickness of the silver functional layers for comparative Example 2, the following relationship exists:

dAg.sub.1=dAg.sub.2=dAg.sub.3=dAg.sub.4.

[0157] That is, the thickness of each silver functional layer is equal for all layers.

[0158] Also, with respect to the thickness of the combined dielectric layer sequences before, after and between each of the silver functional layers, for Comparative Example 2, the relationship:

(opl.sub.1×2)<opl.sub.2<opl.sub.3<opl.sub.4<(opl.sub.5×2)

[0159] is not fulfilled, and instead, twice the optical thickness of the first dielectric layer (opl.sub.1× 2) is greater than the optical thickness of second dielectric layer opl.sub.2; and the combined optical thickness layer opl.sub.3 is greater than the combined optical thickness layer opl.sub.4.

[0160] Consequently, for Comparative Example 2 the following relationship between the combined optical layer thicknesses exists:

(opl.sub.1×2)>opl.sub.2<opl.sub.3>opl.sub.4<(opl.sub.5×2)

[0161] A double glazing unit (DGU) (1) as illustrated in FIG. 1 was prepared using a 6 mm glass sheet (2) with a coating (5) as described in comparative Example 2. That is, a 6 mm thick float glass sheet (2) with a coating as detailed in Example 2 was assembled with a second 4 mm thick uncoated float glass sheet (3). The two sheets of glass (2, 3) were assembled such that the coated side (5) of the coated glass (2) sheet faced the interspace (8) (referred to as position two in a DGU when installed), and with the coated glass sheet (2) closer to the external environment (10) than the uncoated glass sheet (3), to form a thermal insulation double-glazing unit. The glass sheets were positioned with an interspace distance of 16 mm between them and the interspace gap (8) was filled with a 90% argon gas and 10% air filling. The uncoated face (4) of the coated glass sheet (2) was therefore present at position 1, and the two uncoated faces (6) and (7) of the second glass sheet (3) were present at positions 3 and 4 respectively. The properties of the double glazing with the low-e coating of comparative Example 2 at position 2, were measured in accordance with EN 410. The results are as provided in Table 3:

TABLE-US-00003 TABLE 3 Parameter Measured value Light transmittance (TL) 54 G-value 26 Selectivity 2.07 Δa*, 0°-60° 3.9 Δb*, 0°-60° 9.4 Δa*, 3% 6.2 Ab*, 3% 8.0

[0162] In Table 3, the Selectivity value is equal to the ratio of the light transmission and g-value for the double glazing unit, wherein each value is calculated using EN 410 incorporated herein by reference.

[0163] The difference in the outside reflection of the DGU prepared with the coating according to comparative Example 2 for a view angle of 0° and 60°, in terms of a* and b* was found to be for Δa*=3.9 and Δb*=9.4. A graphical representation of the change in b* versus viewing angle for Example 2 is shown in FIG. 3.

[0164] Also, in relation to the DGU prepared with the coating of example 2 (not according to the present invention), the colour shifts with thickness variation of 3% are for Δa*=6.2 and Δb*=8.0. That is, the values for Δa* and Δb* for the DGU using the coating detailed in Comparative Example 2 far exceed even the acceptable limit of 5.

Example 3

[0165] The coating sequence described in comparative Example 3 was prepared as follows. Onto a 6 mm float glass pane a first titanium oxide (TiO.sub.x) layer was applied to form a first dielectric coating sequence with an optical layer thickness opl.sub.1 of 53.9 nm. Atop the titanium oxide (TiO.sub.x) layer was then applied a first silver functional layer (Ag layer 1) to a coating thickness of 11.3 nm. A barrier layer of aluminium-doped zinc oxide (ZAO) with an optical layer thickness of 4.1 nm was then deposited on the first silver functional layer (Ag layer 1) to protect the first silver functional layer against the subsequent second coating layer sequence of tin and zinc oxide (ZnSnO.sub.x) applied with an optical layer thickness of 165.6 nm. Consequently, a second dielectric layer sequence was formed comprising a layer of tin and zinc oxide (ZnSnO.sub.x) and a layer of aluminium-doped zinc oxide (ZAO) with a combined optical layer thickness opl.sub.2 of 169.7 nm. Next a second silver functional layer (Ag layer 2) was applied above the second dielectric layer, with a thickness of 14.6 nm. This was followed again by second barrier layer of aluminium-doped zinc oxide (ZAO) with an optical layer thickness of 4.1 nm applied above the second silver functional layer (Ag layer 2). The second barrier layer of aluminium-doped zinc oxide (ZAO) was then coated with a second dielectric coating layer of tin and zinc oxide (ZnSnO.sub.x), to an optical layer thickness of 51.8 nm. A second titanium oxide (TiO.sub.x) layer was applied to form a coating with an optical layer thickness of 80.9 nm, to complete a third dielectric layer sequence formed from a layer of aluminium-doped zinc oxide (ZAO), a layer of tin and zinc oxide (ZnSnO.sub.x), and a layer of titanium oxide (TiO.sub.x) comprising an optical layer thickness opl.sub.3 of 136.8 nm. Above the third dielectric layer sequence was then applied a third silver functional layer (Ag layer 3) with a thickness of 15 nm. Again, a layer of aluminium-doped zinc oxide (ZAO) with an optical layer thickness of 4.1 nm was applied atop the third silver functional layer (Ag layer 3), and above the third layer of aluminium-doped zinc oxide (ZAO) was applied a third layer of tin and zinc oxide (ZnSnO.sub.x) with an optical layer thickness of 128.3 nm to form a fourth dielectric layer sequence with a combined optical layer thickness, opl.sub.4 of 132.4 nm. A fourth silver functional layer (Ag layer 4) with a thickness of 15.5 nm was then applied above the third layer of tin and zinc oxide (ZnSnO.sub.x). Again, a layer of aluminium-doped zinc oxide (ZAO) with an optical layer thickness of 4.1 nm was deposited above the coated on the fourth silver functional layer (Ag layer 4). Finally, a fourth layer of tin and zinc oxide (ZnSnO.sub.x) with an optical layer thickness of 31.1 nm was applied above the fourth layer of aluminium-doped zinc oxide (ZAO) to complete the fifth dielectric sequence with a combined optical layer thickness opl.sub.5 of 35.2 nm.

[0166] The layer sequence for comparative Example 3 may therefore be expressed as: [0167] glass/TiO.sub.x, opl=53.9 nm/Ag 11.3 nm/ZAO, opl=4.1 nm/ZnSnO.sub.x, opl=165.6 nm/Ag 14.6 nm/ZAO, opl=4.1 nm/ZnSnO.sub.x, opl=51.8 nm/TiO.sub.x, opl=80.9 nm/Ag 15 nm/ZAO, opl=4.1 nm/ZnSnO.sub.x 128.3 nm/Ag 15.5 nm/ZAO, opl=4.1 nm/ZnSnO.sub.x, opl=31.1 nm.

[0168] The combined optical layer thicknesses for each of the five dielectric layer sequences opl.sub.1 to opl.sub.5 may be summarized as:

opl.sub.1=53.9 nm, opl.sub.2=169.7 nm, opl.sub.3=136.8 nm, opl.sub.4=132.4 nm, opl.sub.5=35.2 nm.

[0169] In relation to the silver functional layers, the following relationship exists:

dAg.sub.1<dAg.sub.2<dAg.sub.3<dAg.sub.4

[0170] However, with respect to the thickness of the combined dielectric layer sequences before, after and between each of the silver functional layers, the relationship observed for Example 1, namely,

(opl.sub.1×2)<opl.sub.2<opl.sub.3<opl.sub.4<(opl.sub.5×2)

[0171] is not fulfilled for comparative Example 3 and instead, the combined optical thickness for the second dielectric sequence layer opl.sub.2 is smaller than twice the combined optical thickness layer opl.sub.1; the combined optical thickness layer opl.sub.2 is greater than the combined optical thickness layer opl.sub.3; and the combined optical thickness layer opl.sub.3 is greater than the combined optical thickness layer opl.sub.4. That is, the following relationship for the combined optical thickness layer thicknesses opl.sub.1 to opl.sub.5 is observed for comparative Example 3

(opl.sub.1×2)>opl.sub.2>opl.sub.3>opl.sub.4<(opl.sub.5×2)

[0172] A double glazing unit (DGU) (1) as illustrated in FIG. 1 was prepared using a 6 mm glass sheet (2) with a coating (5) as described in comparative Example 3. That is, a 6 mm thick float glass sheet (2) with a coating as detailed in example 3 was assembled with a second 4 mm thick uncoated float glass sheet (3). The two sheets of glass (2, 3) were assembled such that the coated side (5) of the coated glass sheet (3) faced the interspace (8) (referred to as position two in a DGU when installed), that is, the coated glass sheet (5) is closer to the external environment (10) than the uncoated glass sheet (3) to form a thermal insulation double-glazing unit. The glass sheets were positioned with an interspace distance of 16 mm between them and the interspace gap (8) was filled with a 90% argon gas and 10% air filling. The uncoated face (4) of the coated glass sheet (2) was therefore present at position 1, and the two uncoated faces (6) and (7) of the second glass sheet (3) were present at positions 3 and 4 respectively. The properties of the double glazing with the low-e coating from comparative Example 3 at position 2, were measured in accordance with EN 410. The results are as provided in Table 4:

TABLE-US-00004 TABLE 4 Parameter Measured value Light transmittance (TL) 47 G-value 22 Selectivity 2.13 Δa*, 0°-60° 12.1 Δb*, 0°-60° 1.7 Δa*, 3% 10.6 Δb*, 3% 3.2

[0173] In Table 4, the Selectivity value is equal to the ratio of the light transmission and g-value for the double glazing unit, wherein each value is calculated using EN 410 incorporated herein by reference.

[0174] The difference in the outside reflection of the DGU prepared with the coating according to comparative Example 3 for a view angle of 0° and 60°, in terms of a* and b* was found to be for Δa*=12.1 and Δb*=1.7. A graphical representation of the change in a* versus viewing angle for Example 3 is shown in FIG. 4.

[0175] Also, in relation to the DGU prepared with the coating of example 3, the colour shifts with thickness variation of 3% are for Δa*=10.6 and Δb*=3.2.

[0176] That is, the values for Δa* for the DGU using the coating detailed in Comparative Example 3 far exceed even the acceptable limit of 5.

Example 4

[0177] The coating sequence described in Example 4 was prepared as follows. Onto a 6 mm float glass pane a first titanium oxide (TiO.sub.x) layer was applied to form a first dielectric coating sequence with an optical layer thickness opl.sub.1 of 55.1 nm. Atop the titanium oxide (TiO.sub.x) layer was then applied a first silver functional layer (Ag layer 1) to a coating thickness of 8.9 nm. A barrier layer of aluminium-doped zinc oxide (ZAO) with an optical layer thickness of 4.1 nm was then deposited on the first silver functional layer (Ag layer 1) to protect the first silver functional layer against the subsequent second coating layer sequence of tin and zinc oxide (ZnSnO.sub.x) applied with an optical layer thickness of 132.5 nm. Consequently, a second dielectric layer sequence was formed comprising a layer of tin and zinc oxide (ZnSnO.sub.x) and aluminium-doped zinc oxide (ZAO) with a combined optical layer thickness opl.sub.2 of 136.6 nm. Next a second silver functional layer (Ag layer 2) was applied above the second dielectric layer, with a thickness of 12 nm. This was followed again by further barrier layer of aluminium-doped zinc oxide (ZAO) with an optical layer thickness of 4.1 nm applied above the second silver functional layer (Ag layer 2). The layer of aluminium-doped zinc oxide (ZAO) was then coated with a layer of tin and zinc oxide (ZnSnO.sub.x), to thickness of 68.3 nm. A layer of titanium oxide (TiO.sub.x) of thickness 74.7 nm was then applied to form a third dielectric layer sequence opl.sub.3 with a combined optical layer thickness of 147.1 nm. Above the third dielectric layer sequence was then applied a third silver functional layer (Ag layer 3) with a thickness of 14.5 nm. On the layer of silver was then applied an absorbing layer of nickel chromium of thickness 0.3 nm, to reduce the transmission of the coating. Above the NiCr-layer a third layer of tin and zinc oxide (ZnSnO.sub.x) with an optical layer thickness of 163.5 nm to form a fourth dielectric layer sequence with a combined effective optical layer thickness, opl.sub.4 of 163.5 nm. A fourth silver functional layer (Ag layer 4) with a thickness of 16.9 nm was then applied above the third layer of tin and zinc oxide (ZnSnO.sub.x). Again, a layer of nickel chromium with an optical layer thickness of 0.8 nm was then applied above the fourth silver layer. Finally, a fourth layer of tin and zinc oxide (ZnSnO.sub.x) with an optical layer thickness of 84.9 nm was applied to complete the fifth dielectric sequence with a combined effective optical layer thickness opl.sub.5 of 86.9 nm.

[0178] The layer sequence for example 1 may therefore be expressed in terms of optical layer thickness and geometric layer thickness for the silver function layers as: [0179] glass/TiO.sub.x, opl=55.1 nm/Ag 8.9 nm/ZAO, opl=4.1 nm/ZnSnO.sub.x, opl=132.5 nm/Ag 12 nm/ZAO, opl=4.1 nm/ZnSnO.sub.x, opl=68.3 nm/TiO.sub.x, opl=74.7 nm/Ag 14.5 nm/NiCr 0.3 nm/ZnSnO.sub.x 163.5 nm/Ag 16.9 nm/NiCr 0.8 nm/ZnSnO.sub.x, opl=84.9 nm.

[0180] The optical layer thicknesses for each of the five dielectric layer sequences opl.sub.1 to opl.sub.5 may be summarized as:

opl.sub.1=55.1 nm, opl.sub.2=136.6 nm, opl.sub.3=147.1 nm, opl.sub.4=163.5 nm, opl.sub.5=84.9 nm.

[0181] In addition, in respect of Example 4, the thickness of each silver functional layer dAg increases as the distance of the silver functional layer to the glass substrate increases. That is for example, the thickness of the second silver functional layer dAg.sub.2 is greater than the thickness of the first silver functional layer dAg.sub.1.

[0182] Consequently, in respect of Example 4 according to the present invention, the following relationships are satisfied: [0183] i) with respect to the thicknesses of the silver functional layers,

dAg.sub.1<dAg.sub.2<dAg.sub.3<dAg.sub.4; and [0184] ii) with respect to the thickness of the combined dielectric layer sequences before, after and between each of the silver functional layers,

(opl.sub.1×2)<opl.sub.2<opl.sub.3<opl.sub.4<(opl.sub.5×2)

[0185] A double glazing unit (DGU) (1) as illustrated in FIG. 1 was prepared using a 6 mm glass sheet (2) with a coating (5) as described in Example 4. That is, a 6 mm thick float glass sheet (2) with a coating as detailed in Example 4 was assembled with a second 4 mm thick uncoated float glass sheet (3). The two sheets of glass (2, 3) were assembled such that the coated side (5) of the coated glass sheet (3) faced the interspace (8) (referred to as position two in a DGU when installed), that is, the coated glass sheet (5) is closer to the external environment (10) than the uncoated glass sheet (3) to form a thermal insulation double-glazing unit. The glass sheets were positioned with an interspace distance of 16 mm between them and the interspace gap (8) was filled with a 90% argon gas and 10% air filling. The uncoated face (4) of the coated glass sheet (2) is therefore present at position 1, and the two uncoated faces (6) and (7) of the second glass sheet (3) are present at positions 3 and 4 respectively. The properties of the double glazing with the low-e coating at position 2, were measured in accordance with EN 410. The results are as provided in Table 5:

TABLE-US-00005 TABLE 5 Parameter Measured value Light transmittance (T.sub.L) 50 G-value 23 Selectivity 2.17 Δa*, 0°-60° 2.2 Δb*, 0°-60° 2.5 Δa*, 3% 2.9 Δb*, 3% 2.3

[0186] In Table 5, the Selectivity value is equal to the ratio of the light transmission and G-value for a double glazing unit, wherein each value is calculated using EN 410 incorporated herein by reference.

[0187] The difference in the outside reflection of the DGU prepared with the coating according to comparative Example 4 for a view angle of 0° and 60°, in terms of a* and b* was found to be for Δa*=2.2 and Δb*=2.5. A graphical representation of the change in a* versus viewing angle for Example 4 is shown in FIG. 5.

[0188] Also, in relation to the DGU prepared with the coating of Example 4, the colour shifts with thickness variation of 3% are for Δa*=2.9 and Δb*=2.3. That is, the values for Δa* and Δb* for the DGU prepared using the coating of Example 4, according to the present invention, are within the accepted limit of 5, and are also within the preferred limit of 4, and are even within the especially preferred limit of 3.

Summary of Results

[0189] Therefore, it can be seen from the above results that the coated glass sheets prepared according to the present invention (that is, Examples 1 and 4) provide good solar control performance with a high selectivity 2.18 and 2.17. Also, both of Examples 1 and 4 show a small variation of the outside colour under different viewing angle when placed in a façade. For both examples, the colour change under different viewing angle when placed in a double glazing unit is as preferred, with a value of less than 3.0 for Δa* and Δb*.

[0190] In terms of the production of double glazing units (DGUs), it is an important advantage associated with the present invention of being able to offer DGU's which demonstrate a low change in colour as the thickness of the coating layer changes. For both of Examples 1 and 4, there was a change of less than 3 for both Δa* and Δb*, for a thickness variation in the fourth dielectric layer of the coating stack sequence of 3%.

[0191] In contrast, in comparative Example 2, were all of the silver layers are of the same thickness, and also, the optical thickness relationship for each of the dielectric layers required of the present invention is not fulfilled, the selectivity is 2.07, and the colour shift for the coated substrate under different viewing angles (0°-60°) when formed into a DGU is above 5 for b*, and actually Δb*=9.4. The colour change with a thickness variation of 3% for the second dielectric layer of Example 2 is also above 5, with values of Δa*=6.2 and Δb*=8.0 respectively.

[0192] In comparative Example 3, the required optical thickness relationship for the dielectric layers according to the present invention is again not fulfilled. Instead, the optical layer thicknesses for the dielectric layers in Example 3 decrease instead of increasing, as one moves away from the glass substrate. In addition, the selectivity is 2.13, and the colour shift under different viewing angles (0°-60°) for the DGU formed with a coated glass according to Example 3, is above 5 for a*, and actually, Δa*=12.1. Finally, the colour change recorded with a thickness variation of 3% for the fourth dielectric layer in Example 3 for a* is also above 5, with a value for Δa*=10.6.