WO2026009004A1

WO2026009004A1 - A laminated glazing

Info

Publication number: WO2026009004A1
Application number: PCT/GB2025/051482
Authority: WO
Inventors: John Ridealgh; Giovanni Gagliardi; Gustavo BENEDETTO; Philip Savage; John Buckett
Original assignee: Pilkington Technology Management Ltd
Current assignee: Pilkington Technology Management Ltd
Priority date: 2024-07-05
Filing date: 2025-07-04
Publication date: 2026-01-08
Anticipated expiration: 2027-01-05

Abstract

A laminated glazing comprises a first transparent glass ply, a second transparent glass ply and an adhesive interlayer therebetween, wherein the adhesive interlayer comprises a light and heat absorbing layer, which layer has a visible light transmittance less than or equal to 8%; the laminated glazing has a heat reflecting coating between the first transparent glass ply and the light and heat absorbing layer, which coating has a visible light reflectance of at least 30%; the exterior surface of the second transparent glass ply has a low emissivity coating thereon, providing that the exterior surface has an emissivity of less than or equal to 0.17; and wherein the laminated glazing has a total solar energy transmittance of less than or equal to 10%.

Description

A LAMINATED GLAZING

The present invention concerns a laminated glazing. It particularly, but not exclusively, concerns a laminated glazing which is suitable for use in a vehicle, such as a motor vehicle, as a roof light.

Nowadays, motor vehicle roof lights generally require a laminated glazing including one or more solar control elements. The roof light may be designed to limit the amount of heat it transmits in hot weather and to reduce the amount of heat it transmits in cold weather so that it provides a degree of thermal comfort for the occupants of the vehicle. The roof light should, however, transmit sufficient visible light to enable the occupants of the vehicle to see through it without experiencing glare or an interfering light reflection from the interior of the vehicle.

To these ends, a roof light may comprise a tinted glass and/or a tinted interlayer material and a low emissivity (low E) coating provided on the exterior surface of the laminated glazing closest to the interior of the vehicle.

WO 2020/234593 Al discloses one such motor vehicle roof light. The motor vehicle roof light is intended to achieve low visible light transmittance and low internal visible light reflection. The roof light is obtained by providing a low E coating that is also an antireflective coating. The roof light has an internal light reflectance of less than 4% with a total solar energy transmittance of less than 22%, in particular, 18%.

A roof light may also include a heat reflecting coating provided on a interior surface of the laminated glazing or on an outer (or inner) surface of the interlayer material.

US 2020/0384739 Al discloses one such motor vehicle roof light. The motor vehicle roof light is intended to achieve an internal visible light reflectance of less than 6% with the lowest energy transmittance.

The roof light is obtained by adjusting the tinted components so that they provide, together with the low E and infrared reflecting (IRR) coatings, that the roof light conforms to a transmittance index, designated A, corresponding to the ratio of light transmittance (LT) of the roof light over the product of the light transmittance of the low E coated pane and the energy transmittance (TE) of the glazing. The roof light is said to have a total solar energy transmittance (TTS) of less than 50% and, preferably, less than 25%.

However, the aforementioned motor vehicle roof lights do not provide sufficient solar control and thermal insulation enabling them to be used in a motor vehicle without a roof blind and without reliance on air conditioning, especially when the area of the roof light is relatively large as compared to roof area of the vehicle.

Accordingly, there exists a need for a roof light having a total solar energy transmittance permitting its use in a motor vehicle, without a roof blind and without reliance on air conditioning, which meets the requirements for sufficient visible light transmission and low internal visible light reflection.

The present inventors have surprisingly found a laminated glazing which may meet that need. Advantageously, the laminated glazing can have a neutral and aesthetically pleasing external colour.

Accordingly, in a first aspect, the present invention provides a laminated glazing, comprising a first transparent glass ply, a second transparent glass ply and an adhesive interlayer therebetween, wherein the adhesive interlayer comprises a light and heat absorbing layer, which layer has a visible light transmittance less than or equal to 8%; the laminated glazing has a heat reflecting coating between the first transparent glass ply and the light and heat absorbing layer, which coating has a visible light reflectance of at least 30%; the exterior surface of the second transparent glass ply has a low emissivity coating thereon, providing that the exterior surface has an emissivity of less than or equal to 0.17; and wherein the laminated glazing has a total solar energy transmittance of less than or equal to 10%.

As is conventional in the art, the adhesive interlayer joins a major surface of the first transparent glass ply to a major surface of the second transparent glass ply. In terms conventional to the art, in which the opposing major surfaces of the glass plies are referred to from 1 to 4 from outside to inside the laminated glazing when in it is installed as a vehicle or building window, the interior surface of the first glass transparent ply is surface 2 of the laminated glazing and the exterior surface of the second transparent glass ply is surface 4 of the laminated glazing.

The total solar energy transmittance (TTS) of the laminated glazing refers to its total solar energy transmittance when the exterior surface of the second transparent glass ply forms an interior surface of, for example, a vehicle or building when the laminated glazing is in its installed position.

As used herein, a reference to a value of total solar energy transmittance is a reference to the total solar energy transmittance measured in accordance with ISO 13837:2008, convention A with a wind speed of 14 km/h.

The laminated glazing may have a total solar energy transmittance from 5% to less than 10%. In some embodiments, in which both of the glass plies comprise a float glass, the laminated glazing has a total solar energy transmittance of about 9.8%. In other embodiments, in which the first transparent glass ply comprises an extra clear glass, and the second transparent glass ply comprises a float glass, the total solar energy transmittance of the laminated glazing may be significantly lower than 10%.

The heat reflecting coating is designed to reflect a significant portion of the visible light as well as most of the infrared light in solar light incident the laminated glazing. By contrast, a conventional heat reflecting coating is designed to reflect most of the infrared light and to maximise transmittance of the visible light.

The visible light reflectance of the heat reflecting coating refers to its visible light reflectance in the laminated glazing. The heat reflecting coating may have a visible light reflectance from 35% to 60%, for example, 37%, 45% or 55%.

As used herein, a reference to a value of visible light reflectance is a reference to the visible light reflectance measured in accordance with BS EN 410:2011, Illuminant D65 with 2° observer.

Note that when the heat reflecting coating is provided on a float glass pane of thickness 2.0 mm or 2.1 mm, it may have a (glass side) visible light reflectance at normal incidence greater than or equal to 20%, in particular, from 25% to 50%, for example, from 26% to 44%.

The heat reflecting coating may also have an infrared light reflectance in the laminated glazing between 70% and 90%, for example, between 70% and 85% measured in accordance with ISO 13837:2008, convention A with a wind speed of 14 km/h.

Note that unless indicated otherwise herein, the visible light reflectance and the infrared reflectance values mentioned herein are integrated values obtained at normal incidence of light in the wavelength regions, respectively from 380 nm to 780 nm and from 780 nm to 2500 nm of the electromagnetic spectrum.

The low emissivity coating may provide that the laminated glazing has a low internal visible light reflectance. A low internal visible light reflectance reduces or minimises glare from light originating the dashboard of a vehicle when the laminated glazing is used as a roof light in a vehicle.

Accordingly, the exterior surface of the second transparent glass ply (surface 4) may have a visible light reflectance below 8%. Preferably, it has a visible light reflectance from 1% to 5%, for example, from 1% to 3% or 4%.

Advantageously, the laminated glazing has a direct solar energy transmittance (TDS) of less than or equal to 2%, in particular, less than or equal to 1.7%. This direct solar energy transmittance improves the thermal comfort of the occupants of a vehicle from direct transmittance of heat.

As used herein, the direct solar energy transmittance refers to the solar energy transmitted directly through the laminated glazing determined in accordance with ISO 13837:2008, convention A, with a wind speed of 14 km/h.

Advantageously, the laminated glazing has a total transmittance of visible light which is sufficient for the occupants of the vehicle to see through it. The total transmittance of visible light of the laminated glazing may be from 1% to 5%, for example, less than or equal Advantageously, the laminated glazing has a solar energy absorption which helps to prevent heating of the transparent glass plies to uncomfortably hot temperatures. The solar energy absorption of the laminated glazing is preferably less than 60%, in particular, less than or equal to 50%, measured in accordance ISO 13837:2008, convention A with a wind speed of 14 km/h.

Each transparent glass ply comprises a substantially transparent glass. The transparent glass may comprise a soda-lime-silica glass, a borosilicate glass or an aluminosilicate glass. Preferably, however, the transparent glass comprises a soda-lime-silica glass. Suitable soda- lime-silica glasses include those having a soda-lime-silica glass having a glass composition (by weight), SiO₂ 69 to 74 %; AI2O3 0 to 3 %; Na₂O 10 to 16 %; K₂O 0 to 5 %; MgO 0 to 6 %; CaO 5 to 14 %; SO3 0 to 2 %; and Fe₂O3 (total iron) 0.005 to 0.11%. The composition may also contain other additives, for example, refining aids, which would normally be present in an amount of up to 2%.

Such a glass can be described as a "clear" glass or an "extra-clear" glass depending on its Fe₂O3 (total iron) content. A clear glass has a Fe₂O3 (total iron) content around 0.11% whereas an extra-clear glass has a Fe₂O3 (total iron) content below 0.01%. A glass having a Fe₂O3 (total iron) content around 0.06% may be described as a "mid-iron". In any case, the glass may be a float glass.

The first transparent glass ply and the second transparent ply may comprise a float glass or the first transparent glass ply may comprise an extra clear float glass and the second transparent glass ply a clear float glass.

A suitable clear float glass is sold in the United Kingdom under the trade name Optifloat™ and a suitable extra clear float glass is sold in the United Kingdom under the trade name Optiwhite™ by Pilkington Group Limited.

In any case, the first transparent glass ply and the second transparent glass ply each have a visible light transmittance at 2.1 mm thickness greater than or equal to 88%, for example, greater than or equal to 91%.

As used herein, a reference to a value of visible light transmittance is a reference to the visible light transmittance measured in accordance with BS EN 410, Illuminant D65 with 2° observer. Unless indicated otherwise herein, the value is that obtained at normal incidence of light.

The first transparent glass ply and the second transparent glass ply may each have a thickness from 1.6 mm to 2.6 mm, for example, 2.0 mm and 2.2 mm respectively or 2.1 mm each. Alternatively, one of the transparent glass plies may have a thickness lower than 1.6 mm, for example, less than 0.7 mm and the other transparent glass ply a thickness of 2.0 mm or 2.1 mm. The first transparent glass ply may, in particular, be a chemically toughened clear float glass of thickness about 0.5 mm.

The light and heat absorbing layer absorbs infrared light as well as visible light. The light and heat absorbing layer may, in particular, have a visible light transmittance of less than or equal to 6% and an infrared light transmittance less than or equal to 10% at a thickness of 0.76 mm.

The light and heat absorbing layer may comprise a layer of a thermoplastic polymer, in particular, one or more of a polyvinyl butyral (PVB), a copolymer of ethylene such as ethylene vinyl acetate (EVA), a polyurethane (PU), a polycarbonate, a polyvinyl chloride (PVC) or a copolymer of ethylene and methacrylic acid.

The light and heat absorbing layer may have a thickness between 0.3 mm and 2.3 mm, in particular, between 0.3 mm and 1.6 mm. It may, for example, have a thickness of 0.38 mm, 0.76 mm or 0.81 mm. In preferred embodiments, the light absorbing layer has a thickness of 0.76 mm.

Suitable PVB layers include the solar control polyvinyl butyral (PVB) films sold by Eastmann Chemical Company under the trade name Saflex® with product names SL47 5208, SL47 5206 and SL47 5202.

In one embodiment, the heat reflecting coating is provided on the interior surface of the first transparent glass ply (surface 2). In that case, the adhesive interlayer may be formed by the light and heat absorbing layer alone.

In another embodiment, the heat reflecting coating is provided on at least one carrier film embedded in the adhesive interlayer. In that case, the adhesive interlayer may be formed from the light and heat absorbing layer, the at least one carrier film and a clear additional layer. The layers are arranged so that the light and heat absorbing layer is behind the heat reflecting coating in the laminated glazing viz., the light and heat absorbing layer is nearest to the interior surface (surface 3) of the second transparent glass ply.

The carrier film may comprise any polymer suitable for coating and inclusion in an adhesive interlayer of the type described above. The film may, in particular, comprise a polyethylene terephthalate (PET) film of thickness 20 pm to 100 pm, for example, about 50 pm. The clear additional layer may be a thermoplastic polymer as described above and, in particular, a clear PVB film having a thickness of 0.38 mm or 0.76 mm.

Accordingly, the laminated glazing may have an overall thickness less than or equal to 6 mm, in particular, less than or equal to 5.5 mm.

As indicated above, the heat reflecting coating differs from a conventional heat reflecting coating in that it is adapted to reflect a significant proportion of visible light rather than to minimise the reflection of visible light. The visible light reflectance of the heat reflecting film reduces the heat absorption and re-emission of solar radiation by the adhesive interlayer to an extent that the total solar energy transmittance of the laminated glazing is less than 10.0%.

The heat reflecting coating may, like a conventional heat reflecting coating, comprise a stack of transparent dielectric layers of refractive index from 1.8 to 2.4 and two or more silver layers, for example, two, three or four silver layers, wherein each silver layer is sandwiched between two or more dielectric layer sequences.

As used herein, a reference to a value of refractive index of a layer is a reference to the value obtained at a wavelength of light of 550 nm. The refractive index value may be determined from physical measurement of thickness of a layer using a stylus profilometer and optical modelling of its transmittance and reflectance spectra.

The stack may comprise a base layer sequence, an intervening layer sequence, and a top layer sequence wherein a first silver layer is sandwiched between the base layer sequence and the intervening layer sequence and a second silver layer is sandwiched between the intervening layer and the top layer sequence. The stack may also comprise a third silver layer and an additional intervening layer sequence wherein the third silver layer is sandwiched between a first intervening layer sequence and a second intervening layer sequence.

The base layer sequence may comprise one or more dielectric layers, the intervening layer sequence may comprise three or more dielectric layers, wherein one of the dielectric layers derives from an oxygen barrier layer for silver layer which it contacts, and the top layer sequence may comprise one or more dielectric layers.

The transparent dielectric layers may comprise any of the metal oxides and/or metal nitrides used in a conventional heat reflecting coating. In any case, the optical thickness of the or each intervening layer sequence is selected so that it is not antireflective but reflective for a significant portion of visible light.

The thickness of the or each intervening layer sequence may be 90 nm or above, in particular, from 90 nm to 120 nm, for example, from 100 nm to 110 nm. The optical thickness of the or each intervening sequence may be above 180 nm, in particular, from 200 nm to 240 nm, for example, from 205 nm to 220 nm.

The thickness of each silver layer may range from 10.0 nm to 30.0 nm. The overall thickness of the silver layers may range from 35.0 nm to 45.0 nm, in particular from 38.0 nm to 41.0 nm.

In preferred embodiments, the stack comprises just two silver layers. In this stack the base layer sequence comprises a layer of zinc oxide (ZnO) or aluminium doped oxide (ZnO:AI, 2 to 3% by weight AI2O3) in contact with the first transparent glass ply or the carrier film and the first silver layer, the intervening layer sequence comprises a layer of a titanium oxide (TiO_x) in contact with the first silver layer, a layer of zinc tin oxide (ZnSnOx, 45 to 75% by weight SnOz) in contact with the layer of a titanium oxide, and a layer of zinc oxide (ZnO) or aluminium doped zinc oxide (ZnO:AI, 2 to 3% by weight AI2O3) in contact with the layer of zinc tin oxide and the top layer sequence comprises a layer of a titanium oxide (TiO_x) in contact with the second silver layer, a layer of zinc tin oxide (ZnSnOx, 45 to 75% by weight SnO2) in contact with the layer of a titanium oxide (TiO_x) and a layer of silicon dioxide (SiCh) or aluminium-doped silicon dioxide (SiCh: Al, 10% to 20% by weight AI2O3) in contact with the layer of zinc tin oxide. Note that the dielectric TiO_x layer above the silver layer results from a thin (about 2 nm) barrier layer of titanium which protects the silver layer by scavenging oxygen during the formation of the dielectric layers overlying the silver layer. The stack may be formed using other barrier layers without altering the optical and thermal properties of the heat reflecting coating.

In the preferred embodiment, the intervening layer sequence has an overall thickness from 100 nm to 110 nm, in particular, from 100 nm to 107.5 nm and each silver layer has a thickness from 10 nm to 30 nm.

In the preferred embodiments, the stack may comprise, in order from the first transparent glass ply, a first layer of zinc oxide (ZnO) or aluminium doped zinc oxide (ZnO:AI, 2 to 3% by weight AI2O3), a second layer of silver, a third layer of a titanium oxide (TiO_x), a fourth layer of zinc tin oxide (ZnSnO_x, 45 to 75% by weight SnCh), a fifth layer of zinc oxide (ZnO) or aluminium doped zinc oxide (ZnO:AI, 2 to 3% by weight AI2O3), a sixth layer of silver, a seventh layer of a titanium oxide (TiO_x), an eighth layer of zinc tin oxide (ZnSnO_x, 45 to 75% by weight SnO2) and a ninth layer of silicon dioxide (SiO2) or aluminium-doped silicon dioxide (SiO2:AI, 10 to 20% by weight AI2O3).

In one such embodiment, the first layer has a thickness of 48 nm, the second layer has a thickness of 10 nm or 11 nm, the third layer has a thickness of 2 nm, the fourth layer has a thickness of 69 nm, the fifth layer has a thickness of 31 nm, the sixth layer has a thickness of 27 nm, the seventh layer has a thickness of 2 nm, the eighth layer has a thickness of 43 nm and the ninth layer has a thickness of 1 nm.

In another such embodiment, the first layer has wherein the first layer has a thickness of 46 nm, the second layer has a thickness of 11 nm, the third layer has a thickness of 2 nm, the fourth layer has a thickness of 68 nm, the fifth layer has a thickness of 30 nm, the sixth layer has a thickness of 28 nm, the seventh layer has a thickness of 2 nm, the eighth layer has a thickness of 27 nm and the ninth layer has a thickness of 1 nm.

In a further such embodiment, the first layer has a thickness of 37 nm or 38 nm, the second layer has a thickness of 22 nm or 23 nm, the third layer has a thickness of 2 nm, the fourth layer has a thickness of 75 nm, the fifth layer has a thickness of 30 nm, the sixth layer has a thickness of 18 nm or 19 nm, the seventh layer has a thickness of 2 nm, the eighth layer has a thickness of 31 nm and the ninth layer has a thickness of 1 nm.

In these, and other embodiments having only two silver layers, the heat reflecting coating has an overall thickness from 200 nm to 240 nm, in particular, from 210 nm to 235 nm, for example, 215 nm, 220 nm or 230 nm.

Preferably, the heat reflecting coating is a sputtered (off-line coating). It may alternatively be a part-sputtered coating, wherein the base layer sequence, for example, is laid down (inline) by chemical vapour deposition.

Note that a substitute layer may be used in place of a zinc oxide layer in the base layer sequence or the intervening layer sequence. The substitute layer may comprise a material of similar refractive index and characteristics as zinc oxide, such as silicon nitride (SisN^, aluminium nitride (AIN), zirconium dioxide (ZrCh), or tin oxide (SnCh).

Note also that substitute layers for zinc oxide and zinc tin oxide which comprise materials of different refractive index as compared to zinc oxide and zinc tin oxide (n = 1.96 and 2.05 respectively) may be used in the intervening layer sequence provided that their thicknesses provide that intervening layer sequence conforms to the aforementioned optical thickness.

The base layer sequence may alternatively or additionally comprise a layer of silicon nitride (SisN4). The intervening layer sequence may comprise a layer of titanium dioxide (TiCh, n = 2.4) and a layer or zirconium oxide (ZrCh) instead of the layer of zinc oxide (ZnO, n = 2.1) or the layer of aluminium doped zinc oxide (ZnO:AI, 2 to 3% by weight AI2O3) and the zinc tin oxide layer (ZnSnOx, 45 to 75% by weight SnCh).

The present inventors have found that the light and heat absorbing layer effectively decouples the internal reflectance behaviour from the external reflectance behaviour of the laminated glazing so that, in principle, the low emissivity coating may be any known to the art.

Accordingly, the low emissivity coating may be a hard or soft coating. The low emissivity coating may, depending on its thickness, provide that the exterior surface of the second transparent glass ply has an emissivity from 0.05 to 0.17, in particular, from 0.10 to 0.16, for example, from 0.12 or 0.16.

As used herein, a reference to a value of emissivity is a reference to an emissivity value determined in accordance with BS EN 12898:2019.

Preferably, the low emissivity coating is a low emissivity-low reflectance coating, and in particular, the low emissivity-low reflectance coating described in international patent application WO 2020/234593 Al (the disclosure of which is incorporated herein in its entirety).

Accordingly, the low emissivity coating may comprise a stack of transparent dielectric layers including a transparent conductive metal oxide. The transparent conductive metal oxide may be a fluorine-doped tin oxide (SnO2:F), an antimony-doped tin oxide (SnO2:Sb), or another doped tin oxide.

The stack may comprise, in order from the second transparent glass ply, a first layer of refractive index greater than or equal to 1.6 and thickness less than or equal to 50 nm, a second layer of refractive index lower than that of the first layer and thickness less than or equal to 50 nm; a third layer of refractive index greater than that of the second layer and thickness less than 500 nm, and a fourth layer of refractive index lower than the refractive index of the third layer and thickness less than or equal to 100 nm.

For example, the first layer may a refractive index greater than or equal to 1.8 nm, in particular, between 1.8 and 2.4 and preferably between 1.8 and 2.0. The second layer may have a refractive index between 1.4 and 1.6, preferably between 1.4 and 1.5. The third layer may have a refractive index of 1.6 or more, in particular, 1.8 to 2.0. The fourth layer may have a refractive index less than or equal to 1.7, in particular, between 1.4 and 1.7, for example, between 1.5 and 1.7 or 1.4 and 1.5.

In a preferred embodiment, the stack comprises a first layer of tin oxide (SnCh), a second layer of silicon oxide (SiCh), a third layer of fluorine-doped tin oxide (F:SnO2) or antimony- doped tin oxide (Sb:SnO2), and a fourth layer of silicon oxide (SiCh) wherein the first layer has a thickness of 50 nm or less, the second layer has a thickness of 50 nm or less, the third layer has a thickness less than 500 nm and the fourth layer has thickness 100 nm or less. In this embodiment, the first layer may have a thickness of 28 nm, the second layer may have a thickness of 19 nm, the third layer may have a thickness of 319 nm and the fourth layer may have a thickness of 57 nm. In these and other embodiments, the low emissivity- low reflectance coating may have an overall thickness up to 700 nm, in particular, from 400 nm to 600 nm, for example 427 nm.

The stack may comprise, at least in part, transparent metal oxides other than those mentioned above. The third layer may, for example, comprise indium tin oxide (ITO), gallium doped zinc oxide (Ga:ZnO) or silicon doped zinc oxide (Si:ZnO). The fourth layer may be doped to additionally comprise aluminium oxide (AI2O3), titanium dioxide (TiCh), zirconium oxide (ZrOz), boron oxide (B2O3), phosphors pentoxide (P2O5). Alternatively, the fourth layer may comprise aluminium oxide (AI2O3), zirconium oxide (ZrCh), tin oxide (SnCh) or mixtures thereof.

The low emissivity-low reflectance coating provides that the laminated glazing has a visible light reflectance from its interior surface (surface 4) from 1 % to 5%, in particular, from 1% to 4%, for example 3.6%.

The above-mentioned decoupling means that the internal reflectance colour is largely determined by the low emissivity coating and the external reflectance colour is largely determined by the heat reflecting coating. The decoupling allows for some selection of the external colour reflectance for the laminated glazing by tuning the heat reflecting coating independently from the low emissivity coating.

In a preferred embodiment, the laminated glazing has an external reflectance which is an attractive neutral blue colour of surprising stability over a large range of viewing angles. In this embodiment, the first transparent glass ply has a colour reflectance of L* about 68, a* about -12.5 to -2.5 and b* about -10 to -6 over an incidence range from normal to 80°.

As used herein, a reference to a colour value is a reference to a value measured in accordance with BS EN 410:2011, Illuminant D65 with 10° observer.

In another preferred embodiment, the laminated glazing is light green in colour which varies only slightly over normal viewing angles. In this embodiment, the laminated glazing has a colour reflectance at the first transparent glass ply of L* about 68, a* about -8.5 to -3.5 and b* about -2 to -7 over an incidence range from normal to 80°.

In a further preferred embodiment, the laminated glazing has an intense saturated green colour which varies greatly between through deep saturated colours in the blue-green region of the colour spectrum over normal viewing angles. In this embodiment, the laminated glazing has a colour reflectance at the first transparent glass ply of L* about 68, a* - 17.5 to about -7.5 and b* about 0 to -12 over an incidence range from normal to 80°.

In the preferred and other embodiments, the laminated glazing may have a colour transmission of L* about 17 to 25, a* about -6 to + 6 and b* about 2 to 13.

The laminated glazing may be a roof light for a land or sea vehicle, in particular, for a motor vehicle, such as a passenger motor vehicle or a farm vehicle. The laminated glazing may, however, be used as a back light or as a side light in such vehicles. It may also be used in architectural structures, for example, as a window and, in particular, as a roof light, in a building.

In a second aspect, the present invention provides a land or sea vehicle including a roof light comprising the laminated glazing of the first aspect. The vehicle may be a motor vehicle, such as a passenger motor vehicle or a farm vehicle.

The roof light may be a so-called large area roof light viz., a roof light having surface area from 1.4 m² to 2.5 m², in particular, greater than or equal to 1.4 m², or greater than or equal to 1.9 m² or 2.0 m². In a preferred embodiment, the vehicle does not have a roof blind for the roof light.

Embodiments in this aspect of the present invention will be apparent from those described in relation to the first aspect.

In a third aspect, the present invention provides a method for the manufacture of a laminated glazing according to the first aspect, comprising: providing a first transparent glass ply, having the heat reflecting coating on a surface thereof; providing a second transparent glass ply, having the low emissivity coating on a surface thereof; providing the light and heat absorbing layer as the adhesive interlayer; and laminating the first transparent glass ply, the second transparent glass ply and the adhesive interlayer together whereby to form the laminated glazing with the heat reflecting coating provided on an interior surface of the first transparent glass ply.

The lamination of the first transparent glass ply, the second transparent glass ply and the adhesive interlayer may be carried by an ordinary lamination process. The first and second transparent glass plies may be heated with the adhesive interlayer therebetween in an autoclave to a lamination temperature in the range 90°C to 160°C at a pressure in the range 100 kPa to 2000 kPa. The process may employ a preliminary "pre-nip" step in which the first and second transparent glass plies are heated with the adhesive interlayer therebetween to a pre-nip temperature of, for example, 80°C to 99°C under a reduced atmospheric pressure.

The method may comprise coating a transparent glass ply with the heat reflecting coating to form the first transparent ply. The coating may be carried out by any suitable technique known to the art. Preferably, the coating is an off-line process and in particular, a physical deposition process, such as cathode sputtering, in particular magnetron cathode sputtering. The thickness of the each of the layers of the heat reflecting coating may be controlled by adjusting sputtering power, line speed and process gas parameters.

In preferred embodiments, all of the dielectric layers are deposited by magnetron cathode sputtering. In this process, the first transparent glass ply is transported sequentially past magnetron sputtering cathodes holding the appropriate target materials to produce the required layer sequence, thickness and stoichiometry. The silver layers and the barrier layers are deposited in an atmosphere of pure argon and the overlying dielectric layers are deposited in an atmosphere of argon and oxygen (so called reactive sputtering). A sputtering power supply is chosen, for example, from a DC, a pulsed DC, a bipolar pulsed DC, or a medium Frequency (MF) power supply, for each cathode as appropriate to the formation of the particular dielectric layer. Note, however, that the layers of zinc oxide may alternatively be formed by sputtering at a zinc-aluminium oxide ceramic target using pure argon as the process gas. In some embodiments, the heat reflecting coating is applied after cutting, printing on and shaping of the transparent glass ply. In other embodiments, using barrier layers other than titanium, the heat reflecting coating may be applied before cutting and shaping of the transparent glass ply. If a chemical toughening step is employed, the heat reflecting coating is applied after that step.

The method may further comprise coating of the second transparent glass ply with the low emissivity coating. The coating may be carried out by any suitable technique known to the art. Preferably the coating is carried out in-line with a float glass production process by a chemical vapour deposition.

Embodiments in this aspect of the present invention will be apparent from those described in relation to the first and second aspects.

In a fourth aspect, the present invention provides a method for the manufacture of a laminated glazing according to the first aspect, comprising: providing a first transparent glass ply; providing a second transparent glass ply, having the low emissivity coating on a surface thereof; providing a multilayer comprising the light and heat absorbing layer, a carrier film having the heat reflecting coating on a surface thereof and an additional layer as the adhesive interlayer; and laminating the first transparent glass ply, the second transparent glass ply and the light and heat absorbing adhesive interlayer layer together whereby to form the laminated glazing with the light and heat absorbing layer behind the heat reflecting coating and contacting the interior surface of the second transparent glass ply.

The lamination of the first transparent glass ply, the second transparent glass ply and the adhesive interlayer may be carried by an ordinary lamination process.

The method may comprise coating one or more carrier films with the heat reflecting coating in a roll-to-roll process by sputtering in much same way as for the first transparent glass ply.

The method may further comprise coating of the second transparent glass ply with the low emissivity coating. Embodiments in this aspect will be apparent from those described in relation to the first, second and third aspects.

In a fifth aspect, the present invention provides a coated transparent glass ply, wherein the coating is a heat reflecting coating which, when provided on a clear float glass of thickness 2.0 mm or 2.1 mm, has at normal incidence, a (glass side) visible light reflectance greater than or equal to 20%.

Embodiments in this aspect of the present invention will be apparent from those described in relation to the first, second and third aspects.

In a sixth aspect, the present invention provides an adhesive interlayer for a laminated glazing, which interlayer is a multilayer including a carrier layer having a coating thereon, wherein the coating is a heat reflecting coating which, when provided on a clear float glass of thickness 2.0 mm or 2.1 mm, has at normal incidence, a (glass side) visible light reflectance greater than or equal to 20%.

Embodiments in this aspect of the present invention will be apparent from those described in relation to the first to fifth aspects.

The present invention will now be described in more detail with reference to the following non-limiting embodiments and the accompanying drawings in which:

Figure 1 is a schematic cross-sectional view of a roof light according to an embodiment of the present invention;

Figure 2 is a schematic view of the heat reflecting coating of one embodiment of the roof light of Figure 1 as compared to a conventional heat reflecting coating;

Figure 3 is a graph showing the visible and infrared light reflectance of the heat reflecting coating of one embodiment of the roof light of Figure 1; -

Figure 4 is a graph showing a plot of external colour reflectance of several embodiments of the roof light of Figure 1;

Figure 5 shows (a) a plan view and (b) a cross-section elevation view of apparatus for determining the solar control performance of the roof light of Figure 1;

Figure 6 shows graphs (a) to (c) reporting the solar control performance of the roof light of Figure 1 and the solar control performance of a prior art roof light; and Figure 7 shows graphs (a) to (d) reporting a difference in solar control performance of the roof light of Figure 1 as compared to the prior art roof light.

Referring now to Figure 1, a laminated glazing according to the present invention comprises a roof light, generally designated 10. The roof light 10 has an outer glass pane 11 and an inner glass pane 12 which are joined together by a dark adhesive interlayer 13. The outer glass pane 12 is an ordinary float glass pane of thickness 2.1 mm. The inner glass pane 12 is also an ordinary float glass of thickness 2.1 mm. The dark adhesive interlayer 13 is a heat and light absorbing polyvinyl butyral having a visible light transmittance of 5.9% and thickness 0.76 nm (Saflex® SL47-5206).

The roof light 10 includes a heat reflecting coating 14 on the interior surface of the outer glass pane 11 (surface 2). The heat reflecting coating 14, which is applied to the first pane prior to lamination, has a visible light reflectance greater than 30%. The roof light 10 also includes a low emissivity-low reflectance coating 15 on the exterior surface of the inner glass pane 12 (surface 4).

Referring now to Figure 2, the heat reflecting coating 14 has, in order from the first transparent glass ply 11 (not shown), a first layer 141 of zinc oxide (ZnO), a second layer 142 of silver, a third layer 143 of titanium dioxide (TiCh), a fourth layer 144 of zinc tin oxide (ZnSnOx, 50.5% by weight SnCh), a fifth layer 145 of zinc oxide (ZnO), a sixth layer 146 of silver, a seventh layer 147 of titanium dioxide (TiOz), an eighth layer 148 of zinc tin oxide (ZnSnOx, 50.5% by weight SnOz) and a ninth layer 149 aluminium-doped silicon dioxide (AkSiOz, about 16% by weight AI2O3).

The low emissivity-low reflectance coating 15 has an emissivity of 0.16. The coating 15 has, in order from the second glass ply 12, a first layer of tin oxide (SnO2) at thickness 28.0 nm, a second layer of silicon oxide (SiO2) at thickness 19.1 nm, a third layer of fluorine-doped tin oxide (SnO2:F) at thickness 319.0 nm and a fourth layer of silicon oxide (SiCh) at thickness 56.6 nm.

The heat reflecting coating 14 is designed so that the thickness of the intervening layer sequence viz., the total thickness of the third, fourth and fifth layers 143 to 145 is over 100 nm. The optical thickness of these layers is over 205 nm. The total thickness of the silver layers 142 and 146 is between 37.5 nm and 41.5 nm and the overall thickness of the coating is between 215 nm and 234 nm.

The heat reflecting coating 14 differs from the conventional heat reflecting coating 16 having corresponding layers 161 to 169, in that the thickness of the intervening layer sequence viz., the total thickness of the third, fourth and fifth layers 163 to 165 is greater than in the conventional heat reflecting coating 16. In the heat reflecting coating 16, the third, fourth and fifth layers 163 to 165 have thicknesses which make the intervening layer sequence antireflective for visible light. The total thickness of these layers 163 to 165 is less than 90 nm and the optical thickness less than 190 nm.

Table 1 shows the stack design for the heat reflecting coating 14 in several embodiments (Examples 1 to 3) of the roof light 10. In the Examples, the roof lights 10 are substantially as described above but differ from each other in the thicknesses of the heat reflecting coating 14. Note that the roof lights 10 of the Examples have the same low emissivity-low reflectance coating 15.

Table 1

In Example 1, the total thickness of the third, fourth and fifth layers 143 to 145 is 101.1 nm and provides the laminated glazing with an attractive blue external colour reflectance. In Example 2, the total thickness of the third, fourth and fifth layers 143 to 145 is 100.4 nm and provides the laminated glazing with a light green external colour reflectance. In Example 3, total thickness of the third, fourth and fifth layers 143 to 145 is 107.3 and provides the laminated glazing with an attractive deep green external colour reflectance.

Figure 3 shows the external visible and infrared light reflectance R1 for the laminated glazing of Example 1. The strong local maxima located within the visible range indicates that the heat reflecting coating 14 is not anti reflective for visible light. The laminated glazing 10 reflects a significant portion 17 of visible light with a local reflectance maximum of 45.0% at around 415 nm and a minimum reflectance of about 28.1% at about 655 nm. The laminated glazing also reflects long wave visible light and infrared light with a reflectance of at least 60% in the region from 800 nm to about 2500 nm.

Table 2 shows the thermal and optical properties of the roof light 10 of Example 1. The other Examples 2 and 3 exhibit similar properties and, in particular, a total solar energy transmittance of less than 10%.

Table 2

As may be seen, the roof light 10 has an external visible light reflectance R1 (at surface 1) of about 45%, an internal visible light reflectance R2 (at surface 4) of about 4% and a total transmittance of visible light (T) of about 3%. The total solar energy transmittance (TTS) of the roof light 10 is less than 10%.

The roof light 10 also has a solar absorption of about 47% (46.6%) and a solar energy reflection of about 52% (51.7%). The roof light 10 exhibits negligible transmittance of ultraviolet light measured in accordance with ISO 9050 with air mass coefficient 1.5).

Table 3 reports the external colour reflectance R1 of Examples 1 to 3 of the roof light 10 measured in accordance with the CIELAB colour scale scheme using Illuminant D65, 10° observer, at normal incidence and at incidence of 60°. As may be seen, the roof light 10 of Examples 1 and 2 show a surprising stability in colour between these angles in that there is only a small change in colour co-ordinates a* and b* (towards less green).

Figure 4 shows a plot of the external colour reflectance of Examples 1 to 3 measured in accordance with the CIELAB colour scale scheme at different viewing angles. As may be seen, Example 1 has a colour variation about a* -8 to -6 and b* -10 to -12.5 over the angle range about 0° to 45°. Example 2 has a colour variation about a* -8.5 and about b* -2 to -6 over the same angle range. Example 3 has, by design, a colour variation a* about -17.5 to - 22 and b* about 0 to -8.5 over the same angle range.

Table 3

Figure 5 shows an apparatus for evaluating the solar control performance of the roof light 10. The apparatus comprises a rectangular enclosure 50 which is intended to simulate a vehicle cabin, comprising a wooden box into which the roof light 10 is sealed. The roof light 10, which extends horizontally across substantially the whole of the length and width of the enclosure 50, is installed so that the surface (S4) having the low emissivity coating 15 is the interior surface, i.e. the surface closest to the floor 51 of the enclosure 50. The apparatus includes a K-type thermocouple (tl, t2) on each of the interior surface (S4) and the exterior surface (SI) of the roof light 10. A third K-type thermocouple (t3) is attached to the centre of the interior surface (S4) of the roof light 10 so that it can monitor temperature at a depth within the enclosure 50 corresponding to the intended head position of the average driver (35 cm below S4) when the roof light 10 is in use. A fourth K-type thermocouple (t4) is provided on the floor 51 of the enclosure 50 (60 cm below S4).

The enclosure 50 is supported by two wooden legs 52 each of which extend across substantially the whole of the length of a side of the enclosure 50. The wooden legs ensure an adequate flow of air under the floor 51 of the enclosure 50 - especially when the enclosure 50 is positioned across a gap between two wooden pallets placed upon a rectangular soil bed formed by excavation of earth.

The apparatus also includes a post (about 2 m in height; not shown) upon which another K- type thermocouple (not shown) is provided for measuring ambient air temperature. The post includes a horizontal arm at its upper end which supports a pyranometer (GM6B, from Kipp & Zonen) for measuring global solar radiation.

When adapted by inclusion of a second enclosure, including another roof light and similarly located thermocouples tl to t4, placed beside the enclosure 50, the apparatus can be used to compare the solar control performance of the roof light 10 to the solar control performance of the other roof light.

Figures 6 and 7 show results from one such comparison - conducted in direct sunlight in hot summer time during a period of approximately three months (late June to early September 2024).

In these box tests, the solar control performance of roof light 10 (Example 1, 9a Blue) was compared to that of a commercially produced prior art roof light not having a heat reflecting coating between the first transparent glass ply and a light and heat absorbing layer. The total solar energy transmittance (TTS) of the prior art roof light was 30.3%.

The roof lights were similar in all other respects (materials and dimensions of panes and interlayer) except that the low emissivity coating 15 of roof light 10 was adapted to low reflectance whilst the that of the prior art roof light was not. This difference was, however, inconsequential for solar control because the adaptation does not alter the emissivity of the low emissivity coating.

Measurements were made at each thermocouple and at the pyranometer in intervals of 15 minutes throughout each day (from midnight to midnight).

Figures 6 (a) and (c) report the average temperatures recorded by thermocouples (tl to t4) at these intervals for respectively the prior art roof light and roof light 10. Figure 6 (b) reports average ambient air temperature at these intervals. Note here that all temperatures are averaged over the whole of the 3 month period and that the time lines of Figure 6 (and 7) are indicated by a shortened 24 hour notation.

Referring now to Figures 6 (a) and (b), it can be seen that the prior art roof light exhibited an average temperature on its interior surface (S4) which was generally similar to that of its exterior surface (SI) throughout the day but reached a peak slightly above that of the exterior surface (SI) at peak ambient temperature. The average temperature at the floor 51 of the enclosure 50 was generally similar to the average temperature within its interior (35 mm from S4) throughout the day and both temperatures reached a peak above peak ambient temperature.

Referring now to Figures 6 (c) and (b), it can be seen that roof light 10 exhibited an average temperature on its interior surface (S4) which was substantially lower than that of its exterior surface (SI) at peak ambient temperature. The average temperature at the floor 51 of the enclosure 50 was generally similar to the average temperature within its interior (35 mm from S4) throughout the day and both reached a peak which is below peak ambient temperature.

Considering now Figures 6 (a) and (c), it can be seen that the roof light 10 exhibited average temperatures on its interior surface (S4) and its exterior surface (SI) that were far lower than those on the corresponding surfaces of the prior art roof light at peak ambient temperature. The average temperatures at the floor 51 of the enclosure 50 and within its interior were significantly lower than in the case of the prior art roof light. Figures 7 (a) to (d) particularly point out the average temperature difference exhibited by roof light 10 as compared to the prior art roof light for each of the exterior and interior surfaces, the floor 51 of the enclosure 50 and its interior.

Referring now to Figure 7(a), it is clearly seen that the average temperature difference on the exterior surface (SI) was 11°C at peak ambient temperature. Figure 7 (b) shows that the average temperature difference on the interior surface (S4) was 16°C at peak ambient temperature.

Referring now to Figure 7 (c), it is clearly seen that the average temperature difference within the interior of the enclosure 50 is as much as between 4°C and 5°C at peak ambient temperature. Figure 7 (d) shows that the average temperature difference of the floor 51 of the enclosure 50 is even greater at about 5°C at peak ambient temperature.

Note that the temperature differences at the floor 51 of the enclosure 50 and within its interior are surprisingly high and very significant for air temperature within a vehicle. The temperature differences remain high and significant throughout a major portion of the day (0900h to 1800h).

It will be appreciated, in view of the foregoing, that the present invention can provide an attractive rooflight of fairly neutral outward appearance which not only achieves a total solar energy transmittance of less than 10.0% with low internal light reflectance and sufficient visible light transmittance but does so without significant additional cost as compared to existing roof lights which do not achieve a total solar energy transmittance of less than 10%.

Note that a reference herein to a surface of the laminated glazing as having a coating thereon includes a reference to the coating being in direct contact with that surface.

Claims

1. A laminated glazing, comprising a first transparent glass ply, a second transparent glass ply and an adhesive interlayer therebetween, wherein the adhesive interlayer comprises a light and heat absorbing layer, which layer has a visible light transmittance less than or equal to 8%; the laminated glazing has a heat reflecting coating between the first transparent glass ply and the light and heat absorbing layer, which coating has a visible light reflectance of at least 30%; the exterior surface of the second transparent glass ply has a low emissivity coating thereon, providing that the exterior surface has an emissivity of less than or equal to 0.17; and wherein the laminated glazing has a total solar energy transmittance of less than or equal to 10%.

2. The laminated glazing according to Claim 1, wherein the low emissivity coating provides that the exterior surface of the second transparent glass ply has a visible light reflectance from 1% to 5%.

3. The laminated glazing according to Claim 1 or Claim 2, having a direct solar heat transmittance of less than 2%.

4. The laminated glazing according to any preceding Claim, having a total transmittance of visible light of less than 5%.

5. The laminated glazing according to any preceding Claim, wherein the heat reflecting coating comprises a stack of transparent dielectric layers of refractive index from 1.8 to 2.4 and two or more silver layers, for example, two, three or four silver layers, wherein each silver layer is sandwiched between two or more dielectric layer sequences.

6. The laminated glazing according to claim 5, wherein the stack comprises a base layer sequence, one or more intervening layer sequence, and a top layer sequence of dielectric layers wherein the, or each, intervening layer sequence has an optical thickness from 180 nm to 240 nm.

7. The laminated glazing according to Claim 5 or Claim 6, wherein the, or each, intervening layer sequence has a thickness from 90 nm to 120 nm.

8. The laminated glazing according to any of Claims 5 to 7, wherein the stack comprises, in order from the first transparent glass ply, a first layer of zinc oxide (ZnO) or aluminium doped zinc oxide (ZnO:AI, 2 to 3% by weight AI2O3), a second layer of silver, a third layer of a titanium oxide (TiO_x), a fourth layer of zinc tin oxide (ZnSnOx, 45 to 75% by weight SnCh), a fifth layer of zinc oxide (ZnO) or aluminium doped zinc oxide (ZnO:AI, 2 to 3% by weight AI2O3), a sixth layer of silver, a seventh layer of a titanium oxide (TiO_x), an eighth layer of zinc tin oxide (ZnSnOx, 45 to 75% by weight SnO2) and a ninth layer of silicon dioxide (SiCh) or aluminium-doped silicon dioxide (SiCh: Al, 10 to 20% by weight AI2O3).

9. The laminated glazing according to Claim 8, wherein the first layer has a thickness of 48 nm, the second layer has a thickness of 10 nm or 11 nm, the third layer has a thickness of 2 nm, the fourth layer has a thickness of 69 nm, the fifth layer has a thickness of 30 nm, the sixth layer has a thickness of 27 nm, the seventh layer has a thickness of 2 nm, the eighth layer has a thickness 43 nm and the ninth layer has a thickness 1 nm.

10. The laminated glazing according to Claim 8, wherein the first layer has a thickness of 46 nm, the second layer has a thickness of 11 nm, the third layer has a thickness of 2 nm, the fourth layer has a thickness of 68 nm, the fifth layer has a thickness of 30 nm, the sixth layer has a thickness of 28 nm, the seventh layer has a thickness of 2 nm, the eighth layer has a thickness of 27 nm and the ninth layer has a thickness of 1 nm.

11. The laminated glazing according to Claim 8, wherein the first layer has a thickness of 37 nm or 38 nm, the second layer has a thickness of 22 nm or 23 nm, the third layer has a thickness of 2 nm, the fourth layer has a thickness of 75 nm, the fifth layer has a thickness of 30 nm, the sixth layer has a thickness of 18 nm or 19 nm, the seventh layer has a thickness of 2 nm, the eighth layer has a thickness of 31 nm and the ninth layer has a thickness of 1 nm.

12. The laminated glazing according to any preceding Claim, wherein the low emissivity coating comprises a stack of transparent dielectric layers including a transparent conductive metal oxide layer, wherein the stack comprises, in order from the second transparent glass ply, a first layer of refractive index greater than or equal to 1.6 and thickness less than or equal to 50 nm, a second layer of refractive index lower than that of the first layer and thickness less than or equal to 50 nm; a third layer of refractive index greater than that of the second layer and thickness less than 500 nm, and a fourth layer of refractive index lower than the refractive index of the third layer and thickness less than or equal to 100 nm.

13. The laminated glazing according to Claim 12, wherein the stack comprises, in order from the second transparent glass ply, a first layer of tin oxide, a second layer of silicon oxide, a third layer of fluorine-doped tin oxide or antimony-doped tin oxide, and a fourth layer of silicon oxide.

14. The laminated glazing according to Claim 13, wherein the first layer has a thickness of 28 nm, the second layer has a thickness of 19 nm, the third layer has a thickness of 319 nm and the fourth layer has a thickness of 57 nm.

15. The laminated glazing according to any preceding Claim, wherein the first transparent glass ply and the second transparent glass ply each comprise a float glass having a light transmittance of greater than or equal to 88%, in particular, greater than 91% at 2.1 mm thickness.

16. The laminated glazing according to any preceding Claim, having colour transmission L* about 17 to 25, a* about - 6 to + 6 and b* about 2 to 13.

17. The laminated glazing according to any preceding Claim, having solar energy absorption less than 60%, in particular less than or equal to 50%.

18. The laminated glazing according to any preceding Claim, being a roof light for a vehicle.

19. A vehicle, in particular, a motor passenger vehicle, including the vehicle roof light of Claim 18.

20. A method for the manufacture of a laminated glazing according to any of Claims 1 to 18, comprising: providing a first transparent glass ply, having the heat reflecting coating on a surface thereof; providing a second transparent glass ply, having the low emissivity coating on a surface thereof; providing the light and heat absorbing layer as the adhesive interlayer; and laminating the first transparent glass ply, the second transparent glass ply and the adhesive interlayer together whereby to form the laminated glazing with the heat reflecting coating provided on an interior surface of the first transparent glass ply.

21. A method for the manufacture of a laminated glazing according to any of Claims 1 to 18, comprising: providing a first transparent glass ply; providing a second transparent glass ply, having the low emissivity coating on a surface thereof; providing a multilayer comprising the light and heat absorbing layer, a carrier film having the heat reflecting coating on a surface thereof and an additional layer as the adhesive interlayer; and laminating the first transparent glass ply, the second transparent glass ply and the light absorbing adhesive interlayer layer together whereby to form the laminated glazing with the light and heat absorbing layer behind the heat reflecting coating and contacting the interior surface of the second transparent glass ply.

22. A coated transparent glass ply, wherein the coating is a heat reflecting coating which, when provided on a clear float glass of thickness 2.0 mm or 2.1 mm, has a visible light reflectance greater than or equal to 20% at normal incidence of light.

23. An adhesive interlayer for a laminated glazing, which interlayer is a multilayer including a carrier layer having a coating thereon, wherein the coating is a heat reflecting coating which, when provided on a clear float glass of thickness 2.0 mm or 2.1 mm, has a visible light reflectance greater than or equal to 20% at normal incidence.