GB2403731A

GB2403731A - Solar control glazing

Info

Publication number: GB2403731A
Application number: GB0316248A
Authority: GB
Inventors: Neil Barton; Ashley Carl Torr
Original assignee: Pilkington Automotive Ltd; Pilkington PLC
Current assignee: Pilkington Group Ltd; Pilkington Automotive Ltd
Priority date: 2003-07-11
Filing date: 2003-07-11
Publication date: 2005-01-12
Also published as: CN1823021B; CN1823021A; GB0316248D0

Abstract

A vehicle glazing is disclosed comprising a pane of tinted glass, tinted by at least 0.5 to 4.0 % wt. of total iron (calculated as Fe2O3), having a low emissivity coating on one of its surfaces. The coating has an emissivity from 0.05 to 0.4 and may include a transparent conductive oxide (and optionally a dopant), or a metal layer and at least one dielectric layer. The glass is preferably toughened glass. Also disclosed is a laminated glazing comprising an outer ply of tinted glass 21, tinted as above, laminated by a sheet of interlayer material 24 to an inner ply 22, which has a low emissivity coating 23 on its external surface. The inner ply may be clear glass or tinted glass. The interlayer material may be clear PVB or tinted PVB, and it may further be infra-red reflecting. Either of the glazings may be used as a vehicle roof glazing.

Description

240373 1 Solar Control Glazing The present invention relates to a vehicle

glazing, especially to a solar control vehicle glazing, which is coated and tinted, and which may further be incorporated into a laminated glazing also for use in a vehicle.

Tinted glazings having a coating on one of their surfaces to impart solar control properties to said glazing are known, particularly glazings of this type which are intended for architectural use. One such glazing is described in EP 1 004 550 At and is referred to as a heat-reflecting glass suitable for use in windows of buildings, especially in double glazing units. The glass substrate is coated with at least one layer of a film mainly comprising silicon. The resultant heat-reflecting glass thus has low visible light reflectance and a green, bronze or grey reflected colour tone.

US 6,538,192 B1 describes a tinted, coated glazing for use in the roof of a vehicle.

It particularly describes a laminated roof glazing comprising an outer pane of "extra clear" glass (i.e. having a total iron content less than 0. 1 % by weight), a laminating interlayer accommodating an array of photovoltaic cells which cover only a portion of said glazing, and an inner pane of tinted (and optionally coated) glass. The outer pane of extra clear glass has maximised energy transmission to allow the proper functioning of the photovoltaic cells, whilst the inner pane is tinted, and optionally coated with an athermic coating, to specifically reduce the maximised energy transmission through the portion of the glazing not covered by the photovoltaic array, thereby increasing vehicle passenger comfort. The optional coating is provided on the interior surface of the inner pane of tinted glass (i.e. the surface facing into the laminate) such that it is in contact with the interlayer. In this position, the coating is devoid of contact with the environment external to the glazing, and is protected from degradation and abrasion.

The laminated roof glazing described in US 6,538,192 B1 has a specific purpose; namely to reduce the energy drain on a vehicle's power source by using, and aptly locating, photovoltaic cells in the glazing. The purpose for which the laminated glazing is intended therefore dictates the requirements for a high energy transmission (i.e. greater than 80 %) outer pane of glass, and a tinted inner pane of glass which thereby compensates for the increased energy transmission (compared to standard clear glass) of the outer glass. /

It would be desirable to provide a vehicle glazing that reduces the amount of energy, especially heat energy, in the form of incident solar radiation which would otherwise be transmitted through said glazing.

It would be especially desirable to provide a laminated glazing for use in a vehicle, that reduces the amount of energy, especially heat energy, in the form of incident solar radiation which would otherwise be transmitted through said glazing.

We have found that such vehicle glazings may be achieved by providing a pane of glass which is tinted by use of at least iron and which has a low emissivity coating on one of its surfaces.

According to a first aspect of the present invention there is provided a vehicle glazing comprising a pane of tinted glass, said glass having a colourant portion including 0.5 to 4.0 % (by weight of the glass) of total iron (calculated as Fe2O3), and a low emissivity coating on a surface of that pane.

The total iron content of the glass plays an important role in determining both the level of absorption of incident energy achieved by the glazing, and also the overall tint of the glazing. The total iron content is thus preferably in the range (% by weight) from 0.8 to 2.0, further preferably from 1.0 to 1.8 and most preferably from 1.3 to 1.6. The tint exhibited by the glazing is preferably a grey, blue or green tint (although a bronze tint is also envisaged), and is further preferably a dark tint (i.e. the glazing has a visible light transmission of 50 % or less).

The low emissivity coating is preferably provided on the interior surface of the pane of tinted glass. By "the interior surface" of said glass is meant the surface of that pane of glass which would form an interior surface of the vehicle into which the glazing may be fitted.

The coating usually includes a metal layer and, advantageously, may also include a dopant material, for example, fluorine or antimony. A number of low emissivity coatings are known in the art, any of which may be used in accordance with the present invention. The emissivity of a particular coating refers to the tendency of that coating to radiate energy. Thus a low emissivity coating is a poor thermal radiator (compared to a blackbody entity, which is a perfect radiator and is defined as having an emissivity of unity). Low emissivity coatings may be provided as one of two principal types: "hard" coatings and "soft" coatings.

A hard coating may be deposited in an "on-line" process, in which the coating is pyrolytically deposited onto the surface of float glass during its formation, in known manner, for example by use of a chemical vapour deposition process. Generally, deposition occurs in the region of a float line where the glass ribbon is at a temperature of between 400 and 760 C; glass of this temperature may be found towards the exit of the tin bath, in the lehr gap (i.e. in the gap between the tin bath and the annealing lehr) and in the hot-end of the annealing lehr. As the glass is fully annealed (i.e. sequentially cooled from its higher temperature state to room temperature), the coating is cured, thus the coating species which initially fused to the glass surface via pyrolysis effectively forms part of the final glass product. The coated side of the glass may be further subjected to a polishing process to reduce the microscopic rugosity of the coated surface to produce a glass that may be more easily handled.

A soft coating is one that is deposited onto the surface of a piece of glass subsequent to complete manufacture of the glass, i.e. in a separate process from the float process. Hence the deposition process is an "offline" process. Off-line coatings include sputtered coatings which are deposited, for example by use of a magnetic sputtering technique under vacuum conditions.

The low emissivity coating present on the glass used in the glazing of the present invention preferably has an emissivity in the range from 0.05 to 0.4; the actual value being measured according to EN 12898 (a published standard of the European Association of Flat Glass Manufacturers). Hard coatings generally have emissivities greater than 0. 15 (and preferably less than 0.2), whilst soft coatings generally have emissivities greater than 0.05 (and preferably less than 0. 1). In both cases, the emissivities may be compared with the assumed normal emissivity of clear uncoated glass, which has a value of around 0.89.

Typically a low emissivity coating comprises a single layer of metal oxide, which is preferably a transparent conductive oxide. Oxides of metals such as tin, zinc, indium, tungsten and molybdenum may be comprised in the single layer of metal oxide.

Alternatively silicon oxide may be used. Usually the coating further comprises a dopant, for example fluorine, chlorine, antimony, tin, aluminium, tantalum, niobium, indium or gallium, so that coatings such as fluorine-doped tin oxide and tin-doped indium oxide may result.

Another type of low emissivity coating may comprise a multilayer coating stack which normally includes a metal layer (or a conductive metal compound) and at least one dielectric layer. The multilayer stack structure may be repeated to further enhance the emissivity of the coating. Amongst other similar metals, silver, gold, copper, nickel and chromium may be used as the metal layer in a multilayer stack; indium oxide, antimony oxide or the like may be used as the conductive metal compound. Coatings comprising one or two layers of silver interleaved between layers of a dielectric such as an oxide of silicon, aluminium, titanium, vanadium, tin or zinc are typical multilayer stacks.

Generally the one or more layers from which the coating is formed are of the order of tens of nanometres in thickness.

The glass used in the glazing of the present invention may be flat or it may be curved, and in addition it may be toughened by means of any known toughening process, for example by thermal or chemical tempering. When the glass is subjected to a heat treatment process, for example tempering or bending, this may be before or after deposition of the low emissivity coating. Should the heat treatment process occur after deposition of the coating, the coating should be one which is not degraded by the exposure to elevated temperature.

Usually the glass will be in a thickness of 8 mm or less (yet greater than 1.5 mm), however a thickness in the range from 2 mm to 6 mm is preferred.

The pane of tinted glass used in the glazing of the present invention generally has a clear base glass composition in the range (by weight): SiO2 68 - 75 % Al2O3 0 - 5 % Na2O 10-18 % K2O 0-5% MgO 0-10 % CaO 5-15% SO3 0-2% The glass may also contain other additives, for example, refining aids, which would normally be present in an amount of up to 2 %.

Normally the glass used in the glazing has a ferrous oxide content (calculated as FeO) in the range 0.05 to 1.6 % by weight. Absorption of total energy that is incident on i the glazing (especially that which is incident on the uncoated surface of the glazing), in particular heat energy in the form of IR radiation, may be achieved by regulating the ferrous oxide content of the glazing. Preferably the ferrous oxide content is greater than 0.4 % by weight, further preferably greater than 0.8 % by weight and most preferably greater than 1.2 % by weight. The higher the ferrous oxide content of the glass, the more total energy is absorbed by the glass, particularly near infra red ("NIR") radiation, which is IR radiation of comparatively short wavelength and thus high energy. The relationship between radiation of a specific wavelength (a) and its corresponding energy (E) is given by: E=hc where h is Planck's constant and c is the speed of light.

Solar energy absorbed by the glass, however, does not remain absorbed; it is re- radiated by the glass over a different wavelength range than that of the incident energy and in all directions, thus at least some radiation is directed away from the low emissivity coating whilst some is directed towards it. The re-radiated energy includes an IR component of longer wavelength and thus lower energy than the incident NIR component.

The low emissivity coating is a poor radiator of long wavelength IR radiation and therefore reduces the total amount of energy passing into a vehicle glazed with a solar control glazing of the present invention.

Preferably the pane of tinted glass comprised in the glazing includes 5 to 350 ppm by weight of cobalt oxide (calculated as CO3O4). In addition to the colourant properties of cobalt, it serves to reduce the visible light transmission of the glass in which it is present.

Thus cobalt oxide is preferably included in the glass in the range from 40 to 320 ppm, further preferably from 100 to 270 ppm and most preferably from 150 to 230 ppm by weight.

Advantageously, the glass used in the glazing has a nickel content (calculated as NiO) in the range up to 500 ppm, and preferably it is greater than 55 ppm, further preferably greater than 100 ppm and most preferably greater than 200 ppm. Moreover, the glass preferably also has a selenium content (calculated as Se) in the range up to 70 ppm, although preferably it is less than 55 ppm, further preferably less than 35 ppm and most preferably less than 20 ppm. Nickel is an ingredient that is added to a glass composition to achieve a grey to brown colour tone, whilst selenium aids achievement of a bronze to grey tone when in co- existence with cobalt.

Normally the glazing has a visible light transmission of 50 % or less. The visible light transmission of a glazing is measured using C.I.E. Illuminant A ("LTA") over the wavelength range 380 nm to 780 nm at 5 nm intervals from the uncoated side of the glazing. The darker the tint of the glazing however, the less visible light is transmitted; transmission of 36 % or less, still less 28 %, and further 20 % or less, is thus preferred. In Europe, legislation dictates that a vehicle windscreen must have not less than 75 % visible light transmission (whereas legislation in the United States requires not less than 70 %).

Front passenger door glasses in both Europe and the United States are required to have not less than 70 % visible light transmission; all other vehicle glass (for example a backlight or a sunroof) may have less than 70 %. Thus the glazing of the present invention is preferably limited to use as an "other glass".

The glazing preferably has a transmitted energy of 30 % or less, when measured at Air Mass 2, ISO 9050. Transmitted energy ("TE"), also known as direct solar heat transmission ("DSHT") is measured at Air Mass 2 (simulating rays from the sun incident at an angle of 30 to the horizontal) over the wavelength range 350 to 2100 rim at 50 rim intervals. The low emissivity coating appears to be successful in suppressing the reradiated energy, especially lower energy IR radiation (in addition to incident lower energy IR radiation), thereby reducing the amount of heat transmitted through said glazing.

Further preferably, therefore, the glazing has a transmitted energy of less than 20 % and most preferably less than 10 %.

Absorption of higher energy IR radiation followed by at least partial reduction of re-radiated lower energy IR radiation by the glazing is especially desirable to vehicle manufacturers in our current commercial climate. Achievement of superior vehicle passenger comfort, for example by minimising the heat gain in the interior of a vehicle, and reduced demand on the resources of a vehicle, for example by reducing the need to use air-conditioning systems and the like, is thus a high priority for today's vehicle manufacturers.

As discussed earlier, the low emissivity coating used in the present invention is provided on the interior surface of the pane of tinted glass, in which position it may reduce the level of IR radiation from the sun that passes through the glazing (including the re-radiation of longer wavelength radiation that is the direct result of absorption of shorter wavelength IR radiation that is incident on the uncoated surface of said glazing).

This effect is likely to have most utility during summer months when the amount of solar radiation that is incident on a glazing will usually be at its greatest.

However, the coated, tinted glazing of the present invention has additional benefits. During winter months in particular, when heating of the interior of a vehicle is necessary, for example to de-mist the windows of the vehicle, the low emissivity coating (which is in direct contact with the environment inside the vehicle) may also inhibit the escape of heat radiation from inside the vehicle to the environment external to the vehicle.

Minimising the amount of heat loss from a vehicle may serve to reduce the "cold- shoulder effect". This effect essentially characterizes the localised coolness in temperature that may be felt by a passenger in a vehicle when they are positioned close to a window, most often a side glazing. The cold-shoulder effect is a result of a vehicle's tendency to lose heat to the outside world, particularly via it's windows and especially on a cold day. A low emissivity coating may reduce this heat loss by reflecting longer wavelength (lower energy) IR radiation back into the vehicle, where it may heat the localised cool air close to the windows.

According to a second aspect of the present invention there is provided a laminated glazing, for use in a vehicle, comprising an outer ply of tinted glass, said glass having a colourant portion including 0.5 to 4.0 % (by weight of the glass) of total iron (calculated as Fe2O3), an inner ply and a sheet of interlayer material laminated therebetween, and a low emissivity coating on the external surface of the inner ply.

Conveniently, the low emissivity coating may be the same as that described in the first aspect of the invention, with the exception that in this second aspect, it is provided on the interior surface of the laminated glazing itself. By "the interior surface" of the laminated glazing is meant the exposed surface of said glazing which would form an interior surface of the vehicle into which the glazing may be fitted (i.e. the external surface of the inner ply). If conventional surface- numbering terminology is used, wherein the surface of the laminate which contacts the environment external to a vehicle is known as surface 1 and the surface which contacts the internal environment is known as surface 4, then the coating is supported on surface 4 (the performance of a low emissivity coating on surface 2 or surface 3 is currently less than satisfactory).

Such a glazing is optimally provided in a thickness of 10 mm or less (yet greater than 3 mm), however a thickness in the range from 4 mm to 7 mm is preferred.

Furthermore, each ply comprised in the laminate is advantageously of thickness in the range from 1.5 mm to 5 mm, although 2 mm to 3.5 mm is preferred.

The sheet of interlayer material is often a sheet of transparent plastic, for example polyvinylbutyral or such other suitable laminating material, and is ordinarily provided in a thickness of 0.76 mm. Alternatively the sheet of interlayer material may be tinted to have an optimum visible light transmission of 35 % or less, preferably 18 % or less.

Furthermore, the sheet of interlayer material may absorb infra-red radiation, for example when it comprises tin-doped indium oxide.

The outer ply of tinted glass may include other colourant components, which may advantageously be the same additional colourants that were suggested earlier for the pane of tinted glass in the first aspect of the invention.

The inner ply, on a surface of which the low emissivity coating is provided, may be clear glass whose composition may include, for example (by weight), 72.1 % sio2, 1. l % Al2O3, 13.5 % Na2O, 0.6 % K2O, 8.5 % CaO, 3.9 % MgO, 0.2 % SO3 and optionally up to 0.2 % Fe2O3 (preferably less than 0.15 %), or it may be tinted glass which has a colourant portion including 0.5 to 4.0 % (by weight of the glass) of total iron (calculated as Fe2O3), 0.05 to 1.6 % by weight of ferrous oxide (calculated as FeO), 5 to 350 ppm by weight of cobalt oxide (calculated as CO3O4), a visible light transmission of 75 % or less and a transmitted energy of 45 % or less. Alternatively, the inner ply may be a polycarbonate, acrylic or other similar material.

The total iron content of the inner ply of glass is preferably in the range (% by weight) from 0.8 to 2.0, further preferably from 1.0 to 1.8 and most preferably from 1.3 to 1.6. Similarly, the cobalt content is preferably in the range from 40 to 320 ppm, further preferably from 100 to 270 ppm and most preferably from 150 to 230 ppm. Ordinarily, if tinted, the inner ply of glass may be grey, blue or green tinted, or possibly even bronze tinted glass. Usually the inner ply of glass has a visible light transmission of 55 % or less, although 36 % or less, and still further 20 % or less, is preferred.

Preferably the ferrous oxide content of the inner ply of glass is greater than 0.4 % by weight, further preferably greater than 0.8 % by weight and most preferably greater than 1.2 % by weight, whilst the transmitted energy is advantageously less than 30 %, and furthermore less than 21 %.

The laminated glazing preferably has a visible light transmission of 35 % or less, further preferably of 18 % or less and most preferably of 10 % or less. Advantageously, the laminated glazing has a transmitted energy of 20 % of less. Of further advantage is transmitted energy of 15 % or less, and further still, of 11 % or less.

The glazing according to the first or second aspects of the invention may be used as a roof glazing in a vehicle. It may be provided either as a conventional sun-roof glazing, or as a glazing that constitutes substantially the entire roof area of a vehicle, which is often referred to as a "full-area roof light".

For a better understanding, the present invention will now be more particularly described, by way of non-limiting example, with reference to and as shown in the accompanying drawings wherein: Figure I is a cross sectional view through a vehicle glazing, and Figure 2 is a cross sectional view through a laminated vehicle glazing in which the low emissivity coating is provided on surface 4.

Vehicle glazing 10 of Figure 1 comprises glass pane 11 which has inner surface 12 and outer surface 13 (labelled with respect to a vehicle into which glazing 10 may be fitted). Inner surface 12 is provided with coating 14; coating 14 may be located directly on inner surface 12, or it may be located on one or more further coating layers (not shown) which are located on inner surface 12. Such further coating layers may be barrier layers to protect glazing 10 from species which may otherwise have a tendency to migrate from coating 14 into glazing 10.

Glass pane 11 may be grey glass which has a base glass composition including (by weight) 72.1 % sio2, 1.l % Al2O3, 13.5 % Na2O, 0.6 % K2O, 8. 5 % CaO, 3.9% MgO and 0.2 % SO3, and a colourant portion comprising (by weight) 1.45 % total iron (calculated as Fe2O3), 0.30 % ferrous oxide (calculated as FeO), 230 ppm CO3O4, 210 ppm NiO and 19 ppm Se hereinafter referred to as composition 1. Such a glass is currently available as GALAXSEETM from Pilkington plc in the United Kingdom.

Coating 14 is a low emissivity coating. When coating 14 has an emissivity, 8, as shown in Table 1 below, and is provided on glass pane 11 (of composition I as described above), resultant glazing 10 exhibits the following properties at the thicknesses specified:

Table 1

Ex. E Thickness of LTA TE TSHT b* glazing 10 (%) (%) (%) a I 0.05 5 mm 9. 8 5.2 19.3 -7.4 4.7 2 0. I 5 mm 11 9 24.5 -4.2 3.6 3 0.45 5 mm 11 9.4 28.9 -4.4 2.7 4 = 5 mm 11.9 10.4 34.5 -4.2 2.4 0.05 6 mm 6.6 3.5 17.9 -7.1 4.6 0. I 6 mm 7.3 5.9 22.1 -4.4 3.6 7 0.45 6 mm 7.4 6.2 26.5 -4.6 2.8 6 mm 7.9 6.9 32 -4.4 2.5 Examples 4 and 8 are comparative examples which illustrate prior art versions of glazing which are not provided with coating 14. The total solar heat transmission ("TSHT") of the glazing is the sum of heat that is directly transmitted through the glazing (i.e. TE) and the heat that is absorbed by the glass of the glazing and subsequently re-radiated. The TSHT measurements were taken according to the Society of Automotive Engineers' published standard SAE J1796 at 14 k. p.h.. Parameters a* and b* are colour co-ordinates according to the CIELAB system (measured at D65, 2 observer), and are used to define the colour of glazing 10.

Alternatively glass pane 11 may be green glass which has the same base glass composition as glass pane 11 described previously, and a colourant portion comprising (by weight) 1.57 % total iron (calculated as Fe2O3), 0.31 % ferrous oxide (calculated as FeO), 115 ppm CO3O4, 0 ppm NiO and 5 ppm Se - hereinafter referred to as composition 2. Such a glass is currently available as SUNDYM 435_, again from Pilkington pie in the United Kingdom. When coating 14 has an emissivity as shown in Table 2 below, and is provided on glass pane 11 of composition 2, resultant glazing 10 exhibits the following properties at the thicknesses specified:

Table 2

Ex. Thickness of LTA TE TSHT glazing 10 (%) (%) (%) a b 9 0.05 5 mm 23 10.1 23.4 -15.3 2.8 0.18 5 mm 25.6 14 28.7 -11.5 1.3 I 1 0.45 5 mm 25.6 14.5 32.8 -11.8 0 12 5 mm 27.6 15.9 38.5 -11.6 -0.4 13 0.05 6 mm 18.2 7.8 21.6 -16 2.5 14 0.18 6 mm 20.2 10.5 25.9 -12.7 1.2 0.45 6 mm 20.3 10.8 30 -12.9 0 16 6 mm 21.8 11.9 35.6 -12.7 -0.4 Examples 12 and 16 are further comparative examples illustrating prior art versions of glazing 10 which are not provided with coating 14.

Further alternatively glass pane 11 may be green glass which has a similar base glass composition as compositions 1 and 2 described previously, and a colourant portion comprising (by weight) 1.30 % total iron (calculated as Fe2O3), 0.26 % ferrous oxide (calculated as FeO), 128 ppm CO3O4, 80 ppm NiO and 7 ppm Se - hereinafter referred to as composition 3. This composition is similar to composition 2 previously described, thus if this glass were to form glazing 10, the properties of resultant glazing 10 would be similar to those measured and recorded in Table 2.

The cross sectional view of Figure 2 illustrates that laminated vehicle glazing 20 comprises outer glass ply 21, inner glass ply 22 and interlayer ply 24, in the form of a PVB sheet, which nominally has a thickness of 0.76 mm. Outer glass ply 21 is tinted glass and inner glass ply 22 is either tinted or clear glass (as described herein). When outer glass ply 21 alone is tinted, it is preferably of a composition chosen from composition 1, 2 or 3 described previously for glass pane 11; when both outer glass ply 21 and inner glass ply 22 are tinted, it is to the same composition for each, again preferably chosen from composition 1, 2 or 3 described previously for glass pane 11. For the avoidance of doubt, although outer glass ply 21 has been described as the glass ply that is tinted in the case where only one glass ply of glazing 20 is tinted, it is however possible that inner glass ply 22 could be tinted instead of outer glass ply 21.

In Figure 2, surface 4 of glazing 20 (i.e. outer surface of inner glass ply 22) is provided with coating 23, which, as for glazing 10, may be directly or indirectly located on said surface. Interlayer ply 24 interleaves between outer glass ply 21 and inner glass ply 22, laminating the two glass plies together when all three are simultaneously subjected to a lamination process in an autoclave. The following tables illustrate non- limiting examples of laminated glazing 20 when it is comprised of various outer glass ply 21 and inner glass ply 22 composition combinations, and when it is laminated with various types of interlayer material. Thus, when coating 23 is a low emissivity coating having an emissivity value as shown in the Tables, laminated glazing 20 exhibits the properties listed at the glass thicknesses specified, wherein: Table 3 represents the case where outer glass ply 21 and inner glass ply 22 are both tinted to the same colour according to composition 1 above, and interlayer ply 24 is either (a) clear PVB, (b) tinted PVB having 35 % LTA, (c) tinted PVB having 18 % LTA or (d) an IR absorbing PVB as indicated, Table 4 is similar to Table 3 except in that outer glass ply 21 and inner glass ply 22 are both tinted to the same colour according to composition 2 above, Table 5 represents the case where outer glass ply 21 is tinted according to composition 1 above, inner glass ply 22 is clear glass (typically as described earlier), and interlayer ply 24 is either (a) clear PVB, (b) tinted PVB having 35 % LTA, (c) tinted PVB having 18 % LTA or (d) an IR absorbing PVB as indicated, and Table 6 is similar to Table 5 except in that outer glass ply 21 is tinted according to composition 2 above.

Table 3

_ Thickness Thickness Ex. of outer of inner Interlayer LTA TE TSHT a* b* glaS2SlPIY glas2s2ply 11 Nazi S (%) (%) - 17 2.1 mm 2.1 mm a 0.05 7 20.8 -7.6 5.1 18 2.55 mm 2.55 mm a 0.05 9.4 4.9 19.1 -7.4 5 19 2.1 mm 2.1 mm a 0.18 12.3 27 4 3.9 ZS5mm 2.55 mm a 0.13 10.5 3.5 24 -4. 3 3.8 21 2.1mm 2.1mm a 0.45 15.2 12.8 31.2 -4.3 2.8 22 2.55 mm 2.55 mm a 0.45 10.5 3.3 28.2 -4.5 2.9 23 2.1mm 2.1mm a 16.4 14.1 36.8 4 2.5 24 2.55 mm 2.55 mm a 11.4 9.7 33.8 -4.4 2.3 3.1mm 3.1mm b 0.13 2.6 2.4 19.3 -6.9 3.3 26 3.1mm 3.1mm b 2.8 2.9 29 7 2.6 27 3.1mm 3.1mm c 1.4 1.7 18.8 -3.1 3.4 23 3.1mm 3.1mm c 1.5 2.1 23.4 -3.2 2.9 3.1mm 3.2 mm d 0.13 5.3 3.8 20.4 5.1 4.3 3.1mm 3.2 mm d 6.3 4.1 29.8 -5.2 3.9

Table 4 Thickness Thickness _ Ex of outer of inner Interlayer LTA TE TSHT * b*

glass ply glas2s2ply ply 24 E (%) (%) (%) a 31 2.1mm 2.1mm a 0.05 27.6 12.3 25.2 -14.6 3.3 32 2.55 mm 2.55 mm a 0.05 22.3 9.7 23.1 -15.4 3.1 33 2.1mm 2.1mm a 0.13 30.3 17.6 31.4 -10.5 1.3 34 2.55 mm 2.55 mm a 0.18 24.9 13.5 28.1 11.3 1.6 2.1mm 2.1mm a 0.45 30.9 13.1 35.3 -10.8 0.4 36 2.55 mm 2.55 mm a 0.45 24.9 13.3 32.1 -12 0.3 37 2.1mm 2.1mm a 33 20 41 -10.7 0 33 2.55 mm 2.55 mm a 27 15 37.7 1 1 9 0 39 3.1mm 3.1mm b 0.18 3.1 4.4 20.9 -15 1.6 3Imm 31mm - 8.7 5 30.5151 0.5 41 3.1mm 2.55 mm c0.18 4.7 3.2 20 -8.8 2.3 42 3.1mm 2.55 mm c5.1 3.8 29.6 -8.9 1.4 43 3.1mm 3.1mm d 0.18 18 8.2 24.1 -13.5 2.6 44 3.1mm 3.1mm d 19.4 9 33.3 -13.7 1.1

Table 5

_ Thickness Thickness Ex. of outer of inner Interlayer LTA TE TSHT A* b* e ni gla2s2ply ply24 s (%) (%) (%) 3.1mm 2.3 mm a 0.05 20.5 10.5 23.4 -8.1 5.3 46 3.1mm 2.3 mm a 0.18 22.7 18 31.5 41 3.8 47 3.1mm 2.3 mm a 0.45 22.5 18.6 35.5 -4.3 2.7 48 3.1mm 2.3 mm a = 24.3 20.5 41.3 4 2.3 3.1mm 2.3 mm b 0.18 9.3 9 24.4 -8.6 3.5 3.1mm 2.3 mm b = 10.1 10.6 34.4 -8.7 2.3 3.1mm 2.3 mm c 0.18 4.9 6.3 22.3 -3.3 4.1 3.1mm 2.3 mm c = 5.3 7.5 32.3 -3.3 3.2 3.1mm 2.3 mm d 0.18 13.8 28.3 5 5.3 54 3.1mm 2.3 mm d 22.7 15 37.3 5 3.9

Table 6

Thickness Thickness Ex. of outer of inner Interlayer LTA TE TSHT 2 else PLY ply 24 s (%) (%) (TO) a' b' 2.55 mm 2.3 mm a 0.05 40.3 13.6 30 -12.9 4.1 56 2.55 mm 2.3 mm a 0.13 45.1 28.9 40.1 -8 2.3 57 2.55 mm 2.3 mm a 0.45 45.1 29.7 43.8 -8.4 0.8 58 2.55 mm 2.3 mm a = 48.3 32.6 49.3 -8 0.3 59 3.1 mm 2.3 mm b 0.13 16.5 11.4 26.4 - 13.7 2.2 3.1 mm 2.3 mm b 17.3 13.2 36.2 -13.9 0.8 61 3.1 mm 2.3 mm c 0.13 8.6 7.S 23.3 -6.9 3.2 62 3.1 mm 2.3 mm c i 9.2 8.3 33.2 7 2.1 63 3.1 mm 2.3 mm d 0.13 37 19.4 33 -10.1 3.7 64 3.1 mm 2.3 mm d 40.4 21.2 41.8 -10.1 1.8 Examples 23, 24, 26, 28 and 30 in Table 3, examples 37, 38, 40, 42 and 44 in Table 4, examples 48, 50, 52 and 54 in Table 5 and examples 58, 60, 62 and 64 in Table 6 are comparative examples illustrating prior art versions of laminated glazing 20 which do not include coating 14.

Claims

Claims: 1. A vehicle glazing comprising a pane of tinted glass, said glass

having a colourant portion including 0.5 to 4.0 % (by weight of the glass) of total iron (calculated as Fe203), and a low emissivity coating on a surface of that pane.
2. A vehicle glazing as claimed in claim 1 wherein the coating is provided on the interior surface of the pane of tinted glass.
3. A vehicle glazing as claimed in claim 1 or claim 2 wherein the coating has an emissivity in the range from 0.05 to 0.4.
4. A vehicle glazing as claimed in any preceding claim wherein the coating includes a transparent conductive oxide.
5. A vehicle glazing as claimed in claim 4 wherein the coating further includes a dopant.
6. A vehicle glazing as claimed in any one of claims 1, 2 or 3 wherein the coating includes a metal layer and at least one dielectric layer.
7. A vehicle glazing as claimed in any preceding claim wherein the pane of tinted glass is toughened glass.
8. A vehicle glazing as claimed in any preceding claim wherein the pane of tinted glass has a thickness in the range from 1.S mm to 8 mm.
9. A vehicle glazing as claimed in any preceding claim wherein the pane of tinted glass includes 0.05 to 1.6 % by weight of ferrous oxide (calculated as FeO).
10. A vehicle glazing as claimed in any preceding claim wherein the pane of tinted glass includes 5 to 350 ppm by weight of cobalt oxide (calculated as CO3O4).
11. A vehicle glazing as claimed in any preceding claim wherein the pane of tinted glass includes up to 500 ppm by weight of nickel oxide (calculated as NiO).
12. A vehicle glazing as claimed in any preceding claim wherein the pane of tinted glass includes up to 70 ppm by weight of selenium metal.
13. A vehicle glazing as claimed in any preceding claim having a visible light transmission of 50 % or less and a transmitted energy of 30 % or less.
14. A laminated glazing, for use in a vehicle, comprising an outer ply of tinted glass, said glass having a colourant portion including 0.5 to 4.0 % (by weight of the glass) of total iron (calculated as Fe2O3), an inner ply and a sheet of interlayer material laminated therebetween, and a low emissivity coating on the external surface of the inner ply.
15. A laminated glazing as claimed in claim 14 wherein the glazing has a thickness in the range from 3 mm to 10 mm.
16. A laminated glazing as claimed in claim 15 wherein each ply has a thickness in the range from 1.5 mm to 5 mm.
17. A laminated glazing as claimed in any of claims 14 to 16 wherein the sheet of interlayer material is transparent and comprises polyvinylbutyral.
18. A laminated glazing as claimed in claim 17 wherein the sheet of interlayer material is tinted to have a visible light transmission of 35 % or less.
19. A laminated glazing as claimed in claim 17 or claim 18 wherein the sheet of interlayer material is infra-red absorbing.
20. A laminated glazing as claimed in any of claims 14 to l9 wherein the inner ply is clear glass.
21. A laminated glazing as claimed in any of claims 14 to 19 wherein the inner ply is tinted glass which has a colourant portion including 0.5 to 4.0 % (by weight of the glass) of total iron (calculated as Fe2O3), 0.05 to 1.6 % by weight of ferrous oxide (calculated as FeO), 5 to 350 ppm by weight of cobalt oxide (calculated as CO3O4), a visible light transmission of 75 % or less and a transmitted energy of 45 % or less.
22. A laminated glazing as claimed in any of claims 14 to 21 having a visible light transmission of 35 % or less and a transmitted energy of 20 % or less.
23. Use of a glazing as claimed in claim I or claim 14 as a roof glazing.
24. A vehicle glazing substantially as hereinbefore described with reference to and as shown in the accompanying drawings.
25. A laminated glazing substantially as hereinbefore described with reference to and as shown in the accompanying drawings.