EP4139259A1

EP4139259A1 - Low-emissivity glazing and method of its production

Info

Publication number: EP4139259A1
Application number: EP21721046.7A
Authority: EP
Inventors: John Viktor ELOFSSON; Sankara PILLAY; Rickard Tim GUNNARSSON; Konstantinos SARAKINOS
Original assignee: Mimsi Materials AB
Current assignee: Mimsi Materials AB
Priority date: 2020-04-21
Filing date: 2021-04-21
Publication date: 2023-03-01
Also published as: WO2021214108A1

Abstract

The present document discloses a glazing in the form of a window glass which comprises a transparent glass substrate, and a coating, which comprises, in order outward from the transparent glass substrate, a seed layer and a functional metal Ag alloy layer. The functional metal Ag alloy layer comprises a Ag alloy consisting essentially of Ag and Al. An Al content is 0.05-0.20 at.%, preferably 0.08-0.14 at.% or more preferably 0.10-0.12 at.% of the Ag alloy, the rest being Ag, and the functional metal Ag alloy layer has a thickness of 5-20 nm, preferably 8-15 nm or more preferably 8-12 nm. The glazing has a solar direct transmittance of at least 30 %, preferably at least 40 %, more preferably at least 50 % as determined according to the European standard EN 410.

Description

LOW-EMISSIVITY GLAZING AND METHOD OF ITS PRODUCTION

Technical Field

The present disclosure relates to a glazing for use as window glass and a method of producing a glazing.

Background

Glazings with a high visible transmittance and high infrared (IR) reflectance are desirable in many applications, allowing light in the visible portion of the electromagnetic spectrum to pass through the glazing while reflecting IR radiation to reduce heat transfer through the glazing.

Common types of glazings that are used in architectural applications include clear and tinted float glass, tempered glass, laminated glass as well as a variety of coated glasses, all of which can be glazed singly or as double, or even triple, glazing units. It is known to provide coatings on window glass in order to reflect IR radiation that is otherwise transferred through the glass from inside the building, while still allowing solar radiation to pass through the glass from outside the building. The most efficient type of coating comprises one functional metal layer, which typically is made of silver (Ag) owing to its high electrical conductivity resulting in high IR reflectivity characteristics.

The functional metal layer is deposited between anti-reflective layers of which each typically include at least one dielectric layer for tuning the optical properties of the glazing. These anti-reflective layers also ensure the protec tion of the functional metal layer from chemical attack and/or mechanical stress.

The optical and electrical properties of the glazing are directly related to the material used as a functional metal layer, thickness of the functional metal layer and the quality of the functional metal layer in terms of, e.g., crystallinity, grain size and interfacial roughness. US 2006/0255727 A1 is related to a thin film reflector and transparent electrical conductor for use as, e.g., a window coating, comprising of a transparent substrate coated with a stack of layers comprising a functional metal layer of a Ag alloy.

A particular challenge is to increase transmittance of rays in the visible and near IR spectrum, such as 300 - 2500 nm, while maintaining high electrical conductivity resulting in high reflectance in the long wavelength IR part of the spectrum, such as 5 - 50 pm.

Summary

It is an object of the present disclosure to provide a glazing for use as window glass.

Further objects are to provide a method of producing a glazing and use of a sputtering target for applying a surface coating.

The invention is defined by the appended independent claims. Embodi ments are set forth in the dependent claims, in the following description and in the drawings.

According to a first aspect there is provided a glazing in the form of a window glass. The glazing comprises a transparent glass substrate and a coating. The coating comprises in order outward from the transparent glass substrate: a seed layer, a functional metal Ag alloy layer covering and in direct contact with the seed layer. The functional metal Ag alloy layer compri ses a Ag alloy consisting essentially of Ag and Al. An Al content is 0.05-0.20 at.%, preferably 0.08-0.14 at.%, more preferably 0.10-0.12 at.% of the Ag alloy, the rest being Ag, and the functional metal Ag alloy layer has a thick ness of 5-20 nm, preferably 8-15 nm or more preferably 8-12 nm. The glazing presents a solar direct transmittance of at least 30 %, preferably 40 %, more preferably 50 % as determined according to the European standard EN 410.

By “glazing” is herein meant a transparent glass substrate coated with a stack of thin film materials or layers.

The glazing can be used as a glass component of a building’s facade or internal surfaces (such as the glass panes in an insulated glass unit).

The glazing may be transparent. By transparent is herein meant a glazing having visible light transmittance typically of the order of 30-90 %. The glazing may be a sheet. Such a sheet may be planar, single curved or double curved.

By window glass is herein meant a window glass for a building. It may also be a roof glass, glass fagade or a door glass.

By transparent glass substrate is herein meant a substrate having a visible light transmittance typically of the order of 30-95 %.

The transparent glass substrate may be substantially planar.

By “consists essentially of” is herein meant that the functional metal Ag alloy layer consists essentially of, or consists of, Ag and Al. The Ag alloy layer contains substantially only elemental Ag and Al, but may contain insubstantial or incidental amounts of impurities ordinarily associated with Ag and Al, and may also contain incidental insubstantial or substantial amounts of materials that do not materially affect the basic and novel characteristics of the functional metal Ag alloy layer.

As a non-limiting example, the functional metal Ag alloy layer may contain less than 0.1 wt.%, preferably less than 0.05 wt.%, most preferably less than 0.01 wt.% of other components, such as incidental impurites.

The Al content is herein calculated as a ratio of the alloying agent Al to the sum of the amounts of the silver and the Al. This means that possible incidental impurities are not included in the alloying agent content.

The layers of the coating may, but need not, form a continuous layer onto the layer it is deposited upon or substrate.

The optical properties and the electrical properties of the glazing are directly related to the material used as a functional metal layer, thickness of the functional metal layer and the quality of the functional metal layer in terms of, e.g., crystallinity, grain size and interfacial roughness.

Experimental data discussed in the following description show that the coating of the glazing, where the functional metal Ag alloy layer has Al content in the interval above, has improved characteristics in terms of higher solar direct transmittance for the same sheet resistance as compared to a coating with an unalloyed Ag functional metal layer. The glazing presents a solar direct transmittance, as determined according to the European standard EN 410, which is higher than a solar direct transmittance of a glazing having a coating with the same layer structure and same sheet resistance as the functional metal Ag alloy layer, but wherein the functional metal Ag alloy layer is replaced by an unalloyed Ag functional metal layer.

The glazing presents a solar direct transmittance, as determined according to the European standard EN 410, which is at least 1 %, preferably at least 2 % higher than a solar direct transmittance of a glazing having a coating with the same layer structure and same sheet resistance as the functional metal Ag alloy layer, but wherein the functional metal Ag alloy layer is replaced by an unalloyed Ag functional metal layer.

The electrical conductivity of the functional metal layer is directly related to its emissivity, such that a higher conductivity (equivalent to a lower resistivity) leads to a lower emissivity. A low emissivity is equivalent to a high reflectance in the long wavelength IR part of the spectrum, such as 5 - 50 pm.

By emissitivity of a material means its effectiveness in emitting energy as thermal radiation.

The the functional metal Ag alloy layer thickness may be selected from a group consisting of about 5-6 nm, about 6-7 nm, about 7-8 nm, about 8-9 nm, about 9-10 nm, about 10-11 nm, about 11-12 nm, about 12-13 nm, about 13-14 nm, about 14-15 nm, about 15-16 nm, about 16-17 nm, about 17-18 nm, about 18-19 nm, and about 19-20 nm.

The seed layer may have a thickness of 2-25 nm, preferably 3-15 nm.

The seed layer may consist essentially of zinc oxide or zinc oxide doped by an additional element, such as aluminum.

The coating may further comprise at least two anti-reflective layers, each having at least one dielectric layer, wherein the seed layer and the functional metal Ag alloy layer is situated in between said anti-reflective layers. The seed layer may be in direct contact with the anti-reflective layer that is situated closest to the transparent glass substrate. The functional metal Ag alloy layer may, but need not, be in direct contact with the anti- reflective layer that is situated furthest away from the transparent glass substrate.

The coating may further comprise at least one blocker layer covering and in direct contact with the functional metal Ag alloy layer, wherein the at least one blocker layer is further away from the transparent glass substrate as compared to the functional metal Ag alloy layer it is covering.

The coating may further comprise at least one diffusion barrier layer situated in between the transparent glass substrate and the anti-reflective layer that is closest to the transparent glass substrate.

The coating may further comprise at least one top layer covering and in direct contact with the anti-reflective layer that is furthest away from the transparent glass substrate, wherein the at least one top layer is further away from the transparent glass substrate as compared to the anti-reflective layer it is covering.

The glazing may have a light transmittance of at least 30 %, preferably at least 50 % or at least 70 % as determined according to the European standard EN 410.

According to a second aspect, there is provided a method of producing a glazing in the form of a window glass having a solar direct transmittance of at least 30 %, preferably 40 %, more preferably 50 %. The method comprises providing a transparent glass substrate, applying, by Physical Vapor Deposition, in order outward from the transparent glass substrate: a seed layer, a functional metal Ag alloy layer covering and in direct contact with the seed layer to the transparent glass substrate, such that the functional metal Ag alloy comprises a Ag alloy layer consisting essentially of Ag and Al. An Al content is 0.05-0.20 at.%, preferably 0.08-0.14 at.%, more preferably 0.10- 0.12 at.% of the Ag alloy, the rest being Ag, and the functional metal Ag alloy layer is provided to a thickness of 5-20 nm, preferably 8-15 nm or 8-12 nm.

The glazing presents a solar direct transmittance, as determined according to the European standard EN 410, which is higher than a solar direct transmittance of a glazing having a coating with the same layer structure and same sheet resistance as the functional metal Ag alloy layer, but wherein the functional metal Ag alloy layer is replaced by an unalloyed Ag functional metal layer.

The seed layer may be provided to a thickness of 2-25 nm, preferably 3-15 nm.

The seed layer provided may be a layer consisting essentially of zinc oxide or zinc oxide doped by an additional element, such as aluminium.

The method may further comprise providing at least two anti-reflective layers, each having at least one dielectric layer, such that the seed layer and the functional metal Ag alloy layer is situated in between said anti-reflective layers.

The method may further comprise providing at least one blocker layer covering and in direct contact with the functional metal Ag alloy layer wherein the at least one blocker layer is further away from the substrate as compared to the functional metal Ag alloy layer it is covering.

The method may further comprise providing at least one diffusion barrier layer situated in between the transparent glass substrate and the anti- reflective layer that is closest to the transparent glass substrate.

The method may further comprise providing at least one top layer covering and in direct contact with the anti-reflective layer that is furthest away from the transparent glass substrate.

The additional layers, such as anti-reflective layers, blocker layer, seed layer, diffusion barrier layer and top layer may be deposited by Physical Vapor Deposition (PVD).

The functional metal Ag alloy layer may be deposited from a Ag alloy sputtering target.

The functional metal Ag alloy layer may be provided to a thickness of about 5-6 nm, about 6-7 nm, about 7-8 nm, about 8-9 nm, about 9-10 nm, about 10-11 nm, about 11-12 nm, about 12-13 nm, about 13-14 nm, about 14- 15 nm, about 15-16 nm, about 16-17 nm, about 17-18 nm, about 18-19 nm, or about 19-20 nm. According to a third aspect, there is provided use of a sputter target for applying a surface coating on a transparent glass substrate. The sputtering target comprises a homogeneous body of Ag alloy target material. The Ag alloy target material consists essentially of Ag and Al. An Al content is 0.05-0.20 at.%, preferably 0.08-0.14 at.% or 0.10-0.12 at.% of the Ag alloy, the rest being Ag.

Brief Description of the Drawings

Fig. 1 schematically illustrates an example of a glazing structure.

Fig. 2 illustrates functional metal Ag alloy layers wherein the alloying agent content is homogeneously and inhomogeneously distributed.

Detailed Description

The concept disclosed herein will now be explained in more detail. Initially, the structure of a glazing is described, thereafter the method of producing such a glazing is described. Finally, characterization results of the glazing are discussed.

In Fig. 1 a non-limiting example of a structure of a glazing 1 is schematically illustrated. The glazing 1 comprises a transparent glass substrate 11 and a coating 10 comprising multiple layers of thin film materials. Starting from the transparent glass substrate 11 and with increasing distance from the transparent glass substrate 11 , the coating 10 comprises an optional diffusion barrier layer 12, an anti-reflective layer 13, a seed layer 14, a functional metal Ag alloy layer 15, an optional blocker layer 16, an anti- reflective layer 17 and an optional top layer 18.

The transparent glass substrate 11 may be a glass substrate, such as a soda-lime glass substrate. The substrate may be homogeneous or laminated, comprising one or more glass layers and, e.g., one or more polymer films. Preferably, an outwardly exposed surface, on which the coating is deposited, is made of glass.

The dimension of the transparent glass substrate 11 may range from over-sized glass panes, which, e.g., may be 3300 x 6000 mm or 3210 x 15000 mm or larger, down to small structures, e.g., 200 x 200 mm. The described glazing is, however, not limited to any specific size of the substrate.

The thickness of the transparent glass substrate may be about 0.3 mm to 25 mm, or about 2 mm to 8 mm or 4 mm to 6 mm. The described coating is, however, not limited to any thickness of the substrate 11.

An optional diffusion barrier layer 12 may be formed on the transparent glass substrate 11. The diffusion barrier layer may be a layer consisting essentially of aluminum oxide, silicon nitride or zinc stannate.

The diffusion barrier layer 12 may act as a barrier layer and the purpose of the diffusion barrier layer is to prevent sodium ions from diffusing from the glass into the other layers, such as the functional metal Ag alloy layer 15, of the coating 10. Diffusion into the functional metal Ag alloy layer 15 may have detrimental effects on said layer.

The anti-reflective layer 13 may be formed either directly on the transparent glass substrate 11 or on the optional diffusion barrier layer 12.

The anti-reflective layer 13 may comprise at least one dielectric layer consisting essentially of a metal oxide, such as tin oxide, zinc oxide, zinc tin oxide, titanium oxide, silicon oxide, niobium oxide or zirconium oxide, or a metal nitride, such as silicon nitride or titanium nitride.

The purpose of the anti-reflective layer 13 is to tune the optical properties of the glazing 1 by tailoring the thickness of the at least one dielectric layer. The anti-reflective layer 13 may also protect the functional metal layer 15 from chemical attack and/or mechanical stress.

The thickness of the anti-reflective layer 13 may be about 5 to 120 nm, or about 15 to 100 nm, or about 20 nm to 90 nm.

On top of the anti-reflective layer 13, a seed layer 14 may be formed. The seed layer 14 may be a layer consisting essentially of zinc oxide or zinc oxide doped by an additional element, such as aluminum.

The purpose of the seed layer 14 is to improve the quality of the functional metal Ag alloy layer 15. For example, it may impose an epitaxial relationship for the functional metal layer 15 so that the crystallites in the functional metal layer 15 favour to grow with a (111 ) out-of-plane oriented texture and in that way increases electrical conductivity of the functional metal layer 15. The seed layer 14 may also confer mechanical support to the functional metal layer 15.

The thickness of the seed layer 14 may be about 2 to 25 nm, or about 3 to 15 nm.

The functional metal layer 15 may be formed onto the seed layer 14 or directly on the anti-reflective layer 13.

The functional metal Ag alloy layer 15 is a Ag alloy. The Ag alloy is Ag alloyed with Al. The alloying agent content of the Ag alloy may be homogeneously distributed, or the alloying agent content of the Ag alloy may be inhomogeneously distributed. A non-limiting example of the homogeneously and inhomogeneously distributed alloying agent contents is schematically illustrated in Fig. 2, wherein the functional metal Ag alloy layer thickness measured in the direction outward from the transparent substrate in nanometers is represented on the horizontal axis, wherein the alloying agent content in at.% is represented on the vertical axis, wherein a homogenously distrubuted alloy is represented by the solid line and wherien an inhomo- genously distributed alloy is represented by the dashed curve.

The inhomogeneously distributed alloying agent content may be divided into three zones. In the direction outward from the transparent substrate, the three zones may be a first composition layer zone, a gradient composition layer zone, and a second composition layer zone that are covering and in direct contact with each other. The first composition layer zone and the second composition layer zone each consist of a majority of Ag or Ag alloy. The alloying agent content of the first composition layer zone may be higher than the alloying agent content of the second composition layer zone, or the alloying agent content of the first composition layer zone may be lower than the alloying agent content of the second composition layer zone. The gradient composition layer zone may have an alloying agent content that is substantially the same as the first composition layer zone where the first composition layer zone and the gradient composition layer zone are in direct contact with each other. The gradient composition layer zone may have an alloying agent content that is substantially the same as the second composition layer zone where the second composition layer zone and the gradient composition layer zone are in direct contact with each other. The alloying agent content within the gradient composition layer zone may be transient.

The functional metal Ag alloy layer may have high IR reflectivity characteristics.

The purpose of the functional metal Ag alloy layer 15 is to reduce the long wavelength IR radiation through the glazing, while still being transparent in the visible spectrum and allowing solar radiation to pass through the glazing.

The thickness of the functional metal Ag alloy layer 15 may be about 5 to 20 nm, or about 8 to 15 nm, or about 8 nm to 12 nm.

The glazing 1 may further comprise an optional blocker layer 16 formed on top of the functional metal Ag alloy layer 15.

The blocker layer 16 may be an oxidized metal layer, based on nickel chrome, nickel, chrome, niobium, titanium or zinc, or a metal nitride layer, based on nickel chrome or chrome.

The purpose of the blocker layer 16 is to improve the quality of the functional metal Ag alloy layer 15 by protecting the functional metal Ag alloy layer during deposition of a subsequent layer, such as the anti-reflective layer 17.

The thickness of the blocker layer 16 may be about 0.5 to 6 nm, or about 1 to 4 nm.

The anti-reflective layer 17 may then be formed on the blocker layer 16 or directly on the functional metal Ag alloy layer 15. The anti-reflective layer 17 may comprise at least one dielectric layer consisting essentially of a metal oxide, such as tin oxide, zinc oxide, zinc tin oxide, titanium oxide, silicon oxide, niobium oxide or zirconium oxide, or a metal nitride, such as silicon nitride or titanium nitride. The purpose of the anti-reflective layer 17 is to tune the optical properties of the glazing 1 by tailoring the thickness of the at least one dielectric layer.

The anti-reflective layer 17 may also protect the functional metal layer 15 from chemical attack and/or mechanical stress.

The thickness of the anti-reflective layer 17 may be about 5 to 120 nm, or about 15 to 100 nm, or about 20 nm to 90 nm.

A top layer 18 may be formed on the anti-reflective layer 17.

The top layer 18 may comprise a nitride, e.g., silicon nitride, or an oxide, e.g., aluminum oxide or titanium oxide.

The purpose of the top layer 18 is to protect the underlying layers from mechanical damage, e.g., scratches, and chemical attacks.

The coating 10 may be used as a so-called low-emissivity coating. The emissivity of such a coating is typically < 0.10, preferably < 0.07.

The main purpose of a low-emissivity coating is to reflect long wavelength IR radiation, such as 5 - 50 pm, back into the interior of, e.g., a building such that the heat is not lost to the outside of the building while at the same time allowing solar radiation (such as 300 - 2500 nm) to pass from the outside into the interior of a building to capture free energy.

For a low-emissivity coating, typically only one single functional metal layer situated in between two anti-reflective layers, together with a seed layer and optional layers discussed above, is formed on the substrate, such as a glass pane, thus forming a glazing.

Method for production of the glazing

Each of the layers of the coating 10 in Fig. 1 is formed by Physical Vapor Deposition (PVD), such as magnetron sputtering, evaporation, arc evaporation, pulsed laser deposition and combinations thereof. Preferably, the layers are deposited by magnetron sputtering.

The layers of the coating 10 may be deposited one layer at a time.

The different layers may be deposited in the same or in different sputter zones. The sputter zones may be spatially separated. Alternatively, the sputter zones may be completely or partially overlapping sputtering zones.

The sputter zones may be stationary and the transparent glass substrate may be moveable. The transparent glass substrate may be passed through a sputter zone or between successive sputter zones by means of translation, and/or rotation of the substrate in relation to the sputter zones.

Alternatively, the substrate may be stationary and the sputter zones may surround and face, or at least partially face, the stationary substrate.

The dimensions of the sputtering zones may depend on the application and on the size of the substrate to be coated.

The deposition sources may be so-called sputtering targets.

There may be different deposition sources used for each deposited layer. Alternatively, the same deposition source may be used for deposition of a number of different layers.

The functional metal layer may be deposited from one single deposition source, such as an alloy sputtering target. Alternatively, the functional metal layer is deposited from two separate deposition sources. For example, there may be one deposition source providing the Ag and one deposition source providing the alloying agent Al. If the functional metal layer is deposited from separate deposition sources, the deposition of Ag and the alloying agent Al may take place simultaneously.

Each of the deposited layers may, but need not, form a continuous layer onto the previous layer or onto the substrate.

Prior to deposition of the seed layer 14 and the functional metal layer 15, additional layers may be deposited onto the substrate. Examples of such layers are a diffusion barrier layer 12 and an anti-reflective layer 13.

Additional layers may be deposited onto the functional metal layer 15. Examples of such layers are a blocker layer 16, an anti-reflective layer 17 and/or a top layer 18.

As an example, for deposition of the functional metal layer, the PVD system in which the deposition of layers take place may have a base pressure of about 10² Pa or below. A typical pressure in the PVD system when using a sputtering gas or working gas, such as Ar, is in the range of 0.1 to 2 Pa.

Typically, the substrate is not intentionally heated during deposition of the layers of the coating.

Characterization results of the glazing

Table 1 lists the sheet resistance and solar direct transmittance for glazings with different Al content of the functional metal Ag alloy layer. For comparison, values for an otherwise identical glazing, but where an unalloyed Ag functional metal layer is employed is also listed in Table 1. As can be seen, all glazings exhibit the same sheet resistance, whereas the solar direct transmittance is a function of the Al content. The solar direct transmittance is observed to be higher for glazings with a functional metal Ag alloy layer with an Al content of 0.09, 0.11 and 0.14 at.% as compared to the solar direct transmittance of the unalloyed Ag functional metal layer (0 at.% Al).

Table 1. Sheet resistance and solar direct transmittance for glazings where the Al content of the functional metal Ag alloy layer is varied. Table 2 lists the sheet resistance and solar direct transmittance for glazings with a constant Al content of 0.11 at.% where the thickness of the functional metal Ag alloy layer is varied in order to achieve different sheet resistance values. For comparison, values for an otherwise identical glazing, but where an unalloyed Ag functional metal layer is employed is also listed in Table 2. As can be seen, the solar direct transmittance is higher for glazings consisting of a functional metal Ag alloy layer with an Al content of 0.11 at.% as compared to glazings with an unalloyed Ag functional metal layer (0 at.% Al) for all listed sheet resistance values.

Table 2. Sheet resistance and solar direct transmittance for glazings with a constant Al content of the functional metal Ag alloy layer at different sheet resistance values. Glazings with unalloyed functional metal alloy layers (0 at.% Al content) are also included for reference.

Experimental details Coatings, comprising multiple thin layers, were deposited by means of magnetron sputtering on 50 x 50 mm² soda lime glass substrates in a coating chamber. Two different deposition series were produced, one where the Al content of the functional metal Ag alloy layer was varied (0.09, 0.11 and 0.14 at.%) at a constant sheet resistance and one where the Al content of the functional metal Ag layer was held constant at 0.11 at.% for different thicknesses in order to vary the sheet resistance. For reference, unalloyed Ag functional metal layers were also deposited at otherwise the same process conditions. The following coating layer structure was used in all experiments: 4 mm glass/19 nm TiOx/5 nm ZnOx:AI/Ag or Ag alloy/3 nm ZnOx:AI/35 nm ZnOx:AI. The Al dopant content of the ZnOx:AI target employed was 2 wt.% Al. The electrical properties of the coatings were measured using a 4-point probe to determine the sheet resistance. The optical properties in terms of transmittance and reflectance of the glazing were measured with an UV/VIS/NIR spectrophotometer in the wavelength range 250-2500 nm. The alloying agent content of the functional metal layer was determined using X-ray flourescence measurements of about 300 nm thick functional metal layers deposited directly on silicon substrates without the deposition of any other layers.

Claims

1. A glazing (1 ) in the form of a window glass, comprising: a transparent glass substrate (11 ), and a coating (10), comprising, in order outward from the transparent glass substrate (11): a seed layer (14), a functional metal Ag alloy layer (15) covering and in direct contact with the seed layer (14), wherein the functional metal Ag alloy layer (15) comprises a Ag alloy consisting essentially of Ag and Al, wherein an Al content is 0.05-0.20 at.%, preferably 0.08-0.14 at.%, more preferably 0.10-0.12 at.% of the Ag alloy, the rest being Ag, wherein the functional metal Ag alloy layer (15) has a thickness of 5-20 nm, preferably 8-15 nm or more preferably 8-12 nm, and wherein the glazing has a solar direct transmittance of at least 30 %, preferably at least 40 %, more preferably at least 50 % as determined according to the European standard EN 410.

2. The glazing (1 ) as claimed in claim 1 , wherein the glazing presents a solar direct transmittance, as determined according to the European standard EN 410, which is higher than a solar direct transmittance of a glazing having a coating with the same layer structure and same sheet resistance as the functional metal Ag alloy layer (15), but wherein the functional metal Ag alloy layer is replaced by an unalloyed Ag functional metal layer.

3. The glazing (1 ) as claimed in any of the preceding claims, wherein the glazing presents a solar direct transmittance, as determined according to the European standard EN 410, which is at least 1 %, preferably at least 2 %, higher than a solar direct transmittance of a glazing having a coating with the same layer structure and same sheet resistance as the functional metal Ag alloy layer (15), but wherein the functional metal Ag alloy layer is replaced by an unalloyed Ag functional metal layer.

4. The glazing (1 ) as claimed in any of the preceding claims, wherein the functional metal Ag alloy layer (15) thickness is selected from a group consisting of about 5-6 nm, about 6-7 nm, about 7-8 nm, about 8-9 nm, about 9-10 nm, about 10-11 nm, about 11 -12 nm, about 12-13 nm, about 13- 14 nm, about 14-15 nm, about 15-16 nm, about 16-17 nm, about 17-18 nm, about 18-19 nm, and about 19-20 nm.

5. The glazing (1 ) as claimed in any of the preceding claims, wherein the seed layer (14) has a thickness of 2-25 nm, preferably 3-15 nm.

6. The glazing (1 ) as claimed in any of the preceding claims, wherein the seed layer (14) is a layer consisting essentially of zinc oxide or zinc oxide doped by an additional element, such as aluminum.

7. The glazing (1 ) as claimed in any of the preceding claims, wherein the coating (10) further comprises at least two anti-reflective layers (13, 17), each having at least one dielectric layer, wherein the seed layer (14) and the functional metal Ag alloy layer (15) is situated in between said anti- reflective layers (13, 17).

8. The glazing (1 ) as claimed in any of the preceding claims, wherein the coating (10) further comprises at least one blocker layer (16) covering and in direct contact with the functional metal Ag alloy layer (15), and wherein the at least one blocker layer (16) is further away from the transparent glass substrate (11) as compared to the functional metal Ag alloy layer (15) it is covering.

9. The glazing (1 ) as claimed in any of claims 7 to 8, wherein the coating (10) further comprises at least one diffusion barrier layer (12) situated in between the transparent glass substrate (11) and the anti-reflective layer (13) that is closest to the transparent glass substrate (11).

10. The glazing (1 ) as claimed in any of claims 7 to 9, wherein the coating (10) further comprises at least one top layer (18) covering and in direct contact with the anti-reflective layer (17) that is furthest away from the transparent glass substrate (11 ), and wherein the at least one top layer (18) is further away from the transparent glass substrate (11) as compared to the anti-reflective layer (17) it is covering.

11. The glazing (1 ) as claimed in any one of the preceding claims, wherein the glazing has a light transmittance of at least 30 %, preferably at least 50 % or at least 70 % as determined according to the European standard EN 410.

12. A method of producing a glazing (1 ) in the form of window glass having a solar direct transmittance of at least 30 %, preferably 40 %, more preferably 50 %, as determined according to the European standard EN 410, comprising: providing a transparent glass substrate (11 ), applying, by Physical Vapor Deposition to the transparent glass substrate (11 ), in order outward from the transparent glass substrate (11 ): a seed layer (14), a functional metal Ag alloy layer (15) covering and in direct contact with the seed layer (14), such that the functional metal Ag alloy layer (15) comprises a Ag alloy consisting essentially of Ag and Al, wherein an Al content is 0.05-0.20 at.%, preferably 0.08-0.14 at.%, more preferably 0.10-0.12 at.% of the Ag alloy, the rest being Ag, and wherein the functional metal Ag alloy layer (15) is provided to a thickness of 5-20 nm, preferably 8-15 nm or more preferably 8-12 nm.

13. The method as claimed in claim 12, wherein the glazing presents a solar direct transmittance, as determined according to the European standard EN 410, which is higher than a solar direct transmittance of a glazing having a coating with the same layer structure and same sheet resistance as the functional metal Ag alloy layer (15), but wherein the functional metal Ag alloy layer is replaced by an unalloyed Ag functional metal layer.

14. The method as claimed in any one of claims 12 to 13, wherein the seed layer (14) is provided to a thickness of 2-25 nm, preferably 3-15 nm.

15. The method as claimed in any one of claims 12 to 14, wherein the seed layer (14) provided is a layer consisting essentially of zinc oxide or zinc oxide doped by an additional element, such as aluminum.

16. The method as claimed in any one of claims 12 to 15, wherein the method further comprises providing at least two anti-reflective layers (13, 17), each having at least one dielectric layer, such that the seed layer (14) and the functional metal Ag alloy layer (15) is situated in between said anti- reflective layers (13, 17).

17. The method as claimed in any one of claims 12 to 16, wherein the method further comprises providing at least one blocker layer (16) covering and in direct contact with the functional metal Ag alloy layer (15), and wherein the at least one blocker layer (16) is further away from the transparent glass substrate (11) as compared to the functional metal Ag alloy layer (15) it is covering.

18. The method as claimed in any one of claims 16 to 17, wherein the method further comprises providing at least one diffusion barrier layer (12) situated in between the transparent glass substrate (11) and the anti- reflective layer (13) that is closest to the transparent glass substrate (11).

19. The method as claimed in any one of claims 16 to 18, wherein the method further comprises providing at least one top layer (18) covering and in direct contact with the anti-reflective layer (17) that is furthest away from the transparent glass substrate (11 ), and wherein the at least one top layer (18) is further away from the transparent glass substrate (11) as compared to the anti-reflective layer (17) it is covering.

20. The method as claimed in any one of claims 12 to 19 wherein the functional metal Ag alloy layer (15) is deposited from a Ag alloy sputtering target.

21. The method as claimed in any of claims 12 to 20, wherein the functional metal Ag alloy layer (15) is provided to a thickness of about 5-6 nm, about 6-7 nm, about 7-8 nm, about 8-9 nm, about 9-10 nm, about 10-11 nm, about 11-12 nm, about 12-13 nm, about 13-14 nm, about 14-15 nm, about 15- 16 nm, about 16-17 nm, about 17-18 nm, about 18-19 nm, or about 19-20 nm.

22. Use of a sputtering target, comprising a homogeneous body of Ag alloy target material, wherein the Ag alloy target material comprises a Ag alloy consisting essentially of Ag and Al, wherein an Al content is 0.05-0.20 at.%, preferably 0.08-0.14 at.%, more preferably 0.10-0.12 at.% of the Ag alloy, the rest being Ag, for applying a surface coating on a transparent glass substrate (11 ) to form a window glass.