GB2482513A

GB2482513A - Vehicle glazing with an IR reflective coating

Info

Publication number: GB2482513A
Application number: GB1013144.9A
Authority: GB
Inventors: David Andrew Richards
Original assignee: Pilkington Group Ltd
Current assignee: Pilkington Group Ltd
Priority date: 2010-08-05
Filing date: 2010-08-05
Publication date: 2012-02-08
Also published as: GB201013144D0

Abstract

A vehicle glazing 10, e.g. a windscreen, with an infra-red reflective coating 11 and a shade band 14 is described. The glazing has at least one radiation transmissive area 13 which is free from the coating, and which comprises at least 2% of the area of the glazing. The shade band extends across the radiation transmissive area, which itself extends across the width of the glazing. The radiation transmissive area may occupy substantially all of the daylight opening area of the windscreen above the AS 1 line 20 as defined in American National Standards Institute standard ANSI/SAE Z26.1-1996, Section 7. The total solar transmittance TTS (ISO 13837:2008, Convention A, wind velocity 4 m/s) of the glazing is less than 50%, preferably less than 40%. The radiation transmissive area may be used to transmit signals to or from an antenna, receiving instrument, electronic key, and/or a vehicle separation monitoring device. The glazing is intended to reduce the passage of solar heat, but allow electromagnetic communication signals to pass.

Description

VEHICLE GLAZING

The present invention relates to a glazing for a vehicle, and particularly a glazing adapted to reduce the passage of solar heat, commonly referred to as a solar control glazing.

More particularly, the invention relates to a solar control glazing through which electromagnetic communication signals may pass. The glazing may be laminated, and may in particular be a windscreen for a vehicle.

Over recent years a need has developed for solar control glazings having improved performance. Apart from a general desire to improve standards of passenger comfort, concern for the environment has focussed attention on solar heat gain in vehicles, i.e. the rise in the internal temperature of a vehicle resulting from solar radiation. In particular, pressure has developed to reduce carbon dioxide emissions from vehicles for environmental reasons connected with the influence of atmospheric carbon dioxide on the climate. Various approaches have been followed, one of which seeks to reduce the amount of energy used for air-conditioning of vehicles, especially in hot sunny regions of the world. The type of glass used to glaze vehicles can have a significant effect on solar gain, and reducing solar gain in turn reduces both the power rating of the air-conditioning plant required, and the length of time for which it needs to be operated. This yields a reduction in carbon dioxide emissions associated with the air-conditioning plant, which in vehicles manifests itself in reduced ftiel consumption, since the air-conditioning plant is driven by the vehicle's engine.

Legislation in many countries stipulates a minimum light transmission for certain vehicle windows, e.g. for the windscreen and front side glazing, where a light transmission of 70% or 75% is required. This generally means that only a modest solar control performance can be achieved with body-tinted glazings (i.e. glazings comprising tinted glass), and reflective coated glazings must be employed to improve the solar control performance beyond what is achievable with body-tinted glazings.

With the continuing increase in many different forms of communication to and from vehicles, it is also desirable to pass signals in the form of electromagnetic radiation through vehicle windows. However, since solar radiation (which includes visible, infra-red and ultra-violet wavelengths) represents just one part of the same electromagnetic spectrum which also includes radio wavelengths and microwaves, this gives rise to a technical conflict, because coatings which reflect solar radiation are generally also impervious to radio and microwave signals.

One solution to this problem is disclosed in US 5,620,799. This document describes a glazing which has an infra-red reflective coating covering its whole surface except for a small delimited area through which signals may pass. The glazing is fitted with a data transmitter and receiver which are aligned with the delimited area. A coloured band filter may also be provided as part of an intermediate layer of polyvinyl butyral (PVB) making up the glazing.

Unfortunately, this solution is not suitable for data transmitters or receivers whose position within the vehicle is variable, or otherwise uncertain, for instance hand-held devices, or devices retro-fitted by the end-user of the vehicle.

A need therefore exists for a solar control glazing having a high solar control performance, but which still allows electromagnetic signals to pass to and/or from data receiving and/or transmitting devices of variable position.

According to the present invention, there is provided a vehicle glazing over which an infra-red reflective coating extends, the glazing having at least one radiation transmissive area which is free from the coating and a shade band extending across the width of the glazing, wherein the shade band extends across the radiation transmissive area, and said area comprises at least 2% of the area of the glazing.

Whereas until now it has been thought that such radiation transmissive areas should be kept as small as possible to avoid impairing the solar control performance of the glazing, this invention makes use of the realisation that with an appropriate choice of shade band it is possible to considerably increase the size of the radiation transmissive area without in fact significantly compromising the solar control performance. This advantageously enables data transmitters or receivers to be used in a variety of positions within the vehicle. These positions may be variable, i.e. changing, as in the case of hand-held devices. Furthermore, multiple such devices may be used. The invention also facilitates the installation of devices which change position according to whether the vehicle is intended for driving on the left-hand side of the carriageway or the right-hand side thereof.

The infra-red reflective coating may be of any of the well-known types which are commonly used on vehicle windows. For instance, it may be a sputtered metallic coating applied under vacuum conditions, e.g. containing one or more silver layers. Alternatively, it may be a pyrolytically deposited coating produced by a chemical vapour deposition process, comprising transparent conductive oxides, normally metal oxides.

A radiation transmissive area may also be referred to as a "deletion area" or "deletion window", since it is usually produced by locally removing the coating. However, the radiation transmissive area may also be produced by not depositing the coating in the area in question, e.g. by shading or masking techniques. Alternatively, the coating may be deposited on a carrier foil, which is trimmed before incorporation into the glazing. Such techniques are particularly useful when the radiation transmissive area is relatively large, as is proposed in the present invention.

A shade band is defined as any area of the glazing with a reduced regular transmittance, referring to light transmittance. This definition may be found in Regulation 43 of Addendum 42 to the Agreement Concerning the Adoption of Uniform Technical Prescriptions for Wheeled Vehicles, etc, made under the auspices of the Economic Commission for Europe, a United Nations body. The most recent revision is dated 11 February 2004, and the Regulation is commonly referred to in abbreviated form as "ECE R43". The corresponding US Federal Regulation 49 CFR 571 requires compliance with technical standard SAE Ji 00, reaffirmed November 1999, which includes a similar definition for a shade band.

In practice, a shade band takes the form of a translucent tinted area intended to reduce glare from the sun for the occupants of a vehicle, and is positioned immediately adjacent to and below the top edge of a glazing. Shade bands are most common on windscreens, and are generally blue, green or grey in colour.

Now that it is possible to increase the size of the radiation transmissive area without compromising solar performance, the radiation transmissive area may be made substantially larger than previously known. For instance, the radiation transmissive area may comprise at least 5% or 10% or 20% or 30% of the area of the glazing. In practice the limit is set by another aspect of the regulations referred to above, namely that depending on where in the vehicle the glazing is installed, a sufficient area of the window must remain sufficiently transparent to afford satisfactory vision for the driver.

The vehicle glazing may have a single radiation transmissive area, or alternatively it may have a plurality of radiation transmissive areas distributed across its width.

Preferably, the radiation transmissive area extends across the full width of the daylight opening area of the glazing, i.e. excluding any opaque areas. This allows maximum flexibility in the positioning of data transmitters and receivers. The radiation transmissive area may vary in its extent, and may comprise at least 5% or 10% or 25% or 50% or 75% or 90% or 95% of the area of the shade band. The radiation transmissive area may vary in its depth as well as its width, which results in many possible configurations.

The term "daylight opening area" is defined in ECE R43 as the whole glazing area, excluding any opaque obscuration but including any shade band. "Opaque obscuration" means any area of the glazing preventing light transmission. An opaque obscuration area is most commonly found in the form of a black band around the periphery of a glazing, where it serves to obscure the vehicle bodywork on which the glazing is mounted, and to protect the adhesive with which the glazing is bonded to the bodywork from ultraviolet light. An obscuration band is generally screen printed onto the glass using a ceramic ink which is then fired.

Preferably, the shade band extends over substantially all of the radiation transmissive area or areas. Although regulations may allow relatively small areas of a glazing to be free from both the infra-red reflective coating and alternative means of solar control, such as the shade band, the presence of such areas will naturally result in a lesser solar control performance.

In the case where the vehicle glazing is a vehicle windscreen, it is obviously important that the driver has a satisfactory view through the windscreen. Consequently, the regulations referred to above require a light transmission of at least 70% in the critical vision area in front of the driver's eyes, and the extent of this critical area is defined is some detail in the regulations It is, for instance, not permissible to allow the shade band to encroach into this critical vision area. The US regulation requires vehicle glazings to comply with American National Standards Institute standard ANSI/SAE Z26. 1-1996, and this standard requires glazings to be marked with a line denoted the AS 1 line, which indicates the maximum extent of shade band in a downward direction from the top edge of the glazing towards the vision area.

Preferably, the radiation transmissive area occupies substantially all of the daylight opening area of the glazing above the AS 1 line as defined in American National Standards Institute standard ANSI/SAE Z26.1-1996, Section 7.

The vehicle glazing may be laminated, in particular it may comprise at least two plies of sheet glazing material with at least one ply of plastics interlayer material extending between the plies of glazing material, which may be glass. The infra-red reflective coating preferably extends over an internal surface of one of the plies, where it is protected from adverse external influences. The coating may be present on either the glass or plastic plies, or on a further ply of plastics material which serves as a carrier film for the coating. A convenient way of providing the shade band in a laminated glazing is to use tinted plastics interlayer material, i.e. interlayer material which incorporates a dye, usually in a band adjacent one edge of the ply of interlayer material.

The overall total solar transmittance TTS of the whole glazing (TTS is measured according to ISO 13 837:2008, Convention A, wind velocity 4 mIs) comprises a component transmitted through the area of the glazing over which the infra-red reflective coating extends, and a component transmitted through the radiation transmissive area, over which the shade band extends. The magnitude of these components may be offset against each other, but ideally both should be minimised to obtain the best solar control performance. Shade bands vary in their solar control performance, and preferably, the shade band has a low total solar transmittance TTS to minimise the component transmitted through the radiation transmissive area. In particular, it is preferable that the total solar transmittance TTS (ISO 13837:2008, S Convention A, wind velocity 4 mIs) of the shade band is less than 60%. Ideally, the total solar transmittance of the shade band matches that of the infra-red reflecting coating.

In terms of overall performance of the glazing, the total solar transmittance TTS of the glazing (ISO 13 837:2008, Convention A, wind velocity 4 mIs) is preferably less than 50%, more preferably less than 40%.

The invention may be used with any kind of data transmitter or receiver. In particular the radiation transmissive area is adapted to allow the passage of signals and data to or from all types of antenna and other signal transmitting or receiving instruments using electromagnetic radiation of any frequency in use, including radio frequencies, microwave and infra-red frequencies. The devices and instruments include, but are not limited to, the following: a road tolling device, and/or a Global Positioning System (GPS) device, and/or an electronic key for locking or unlocking the vehicle or an external door or gate, and/or a vehicle separation monitoring device.

The invention will now be ftirther described by means of the following non-limiting specific embodiments and illustrated with reference to the accompanying drawings in which:-Figure 1 is a front view of a vehicle glazing according to the invention; and Figure 2 is a section on line Il-Il of Figure 1.

Figure 1 shows a vehicle glazing 10 having an infra-red reflective coating 11 extending over a major part of one of its surfaces, preferably an internal surface as shown in Figure 2.

There is a radiation transmissive area 13 through which signals and data carried by electromagnetic radiation may pass. This area 13 is free from the coating, which, being electrically conductive, would if present either block the signals or attenuate them to the extent that they could not be satisfactorily transmitted or received, as the case may be. A shade band 14 extends across the width of the glazing 10 and across the radiation transmissive area 13.

Furthermore, the shade band 14 extends from the upper edge 15 downwards to the ASi line 20, as described above. The shade band extends over the whole of the radiation transmissive area 13. In fact, from an aesthetic aspect, it is desirable for the shade band to extend over the upper edge of the infra-red reflective coating 11, and then terminate with a fade out region, i.e. the intensity of the tint reduces gradually as the shade band 14 extends ftirther downwards, rather than stops abruptly. By extending over the upper edge of the infra-red reflective coating 11, i.e. overlapping it, the shade band 14 serves to disguise the upper edge, which otherwise might be visible. This means that in practice the infra-red reflective coating 11 extends at least a short way above the AS 1 line, in order to achieve this overlap.

The radiation transmissive area is configured to comprise at least 2% of the area of the glazing, although it may comprise considerably more, and preferably comprises up to 30% of the glazing. The particular glazing shown is a laminated vehicle windscreen having an upper edge 15, side edges 16 and 17, and lower edge 18. It is provided with an opaque obscuration band 19, as described above. The daylight opening area 12 of the windscreen is the area within the obscuration band 19, i.e. the area inboard of the dashed line marking the inner edge of the obscuration band. The transparent area of the windscreen is the daylight opening area 12 excluding the shade band 14, i.e. the area within the obscuration band and below the AS1 line 20.

In the embodiment shown in the drawing, the radiation transmissive area 13 extends across the full width of the windscreen, and hence also the full width of the daylight opening area 12. The radiation transmissive area 13 occupies substantially all of the daylight opening area above the AS 1 line 20. However, it would be a simple matter to arrange for the infra-red reflecting coating to extend upwards, substantially above the AS 1 line. This may have the effect of improving the solar control performance, but reduces the size of the radiation transmissive area. The optimum balance needs to be chosen taking the specific requirements of the individual vehicle into account. Generally speaking, however, good performance in terms of passage of signals will be obtained from a radiation transmissive area which extends across the full width of the daylight opening area, even if it does not extend downwards to the ASi line.

Figure 2 shows a section of the vehicle glazing on line Il-Il of Figure 1. Details of the laminated structure of the glazing may be seen more clearly. It comprises inner and outer plies 21, 22 of sheet glazing material, in this case glass, bonded together by a ply 23 of plastics interlayer material which extends between the plies of glass. The most commonly used interlayer material is polyvinyl butyral (PVB), but other interlayer materials are known.

The terms "inner" and "outer", referring to the plies 21, 22, refer to the interior and exterior of the vehicle, i.e. the inner ply 21 is the ply closest to the interior of the vehicle, and facing the interior. The outer ply 22 is correspondingly the ply closest to the exterior of the vehicle, facing the exterior. The obscuration band 19 is provided on the inward-facing surface of the outer ply 22, but may be provided on a different surface, e.g. the inward-facing surface of the inner ply 21. The infra-red reflecting coating 11 is likewise provided on the inward-facing surface of the outer ply 22, but may be provided on a different surface, e.g. any of the internal surfaces of the plies. It may also be provided on a carrier foil, e.g. of PET, which would be included between the ply 23 of interlayer material and another ply of interlayer material.

The upper limit 24 of the infra-red reflecting coating 11 is indicated by a dotted line.

With regard to the line of section, the radiation transmissive area 13 extends from upper limit 24 to the upper edge 15 of the glazing.

As stated above, the glazing in question is a windscreen, for which regulatory requirements exist regarding light transmission in the driver's vision area. Consequently the shade band 14 may not extend below the AS1 line 20. The shade band 14 is provided by use of tinted plastics interlayer material. A single sheet of interlayer 23 is used for the whole windscreen, but a strip-shaped portion which is adjacent and parallel to the upper edge 15 of the windscreen is tinted to reduce its light and solar heat transmission. The tinted portion of the interlayer is indicated in the drawing by a stipple.

Interlayer material incorporating a suitable shade band is available from the companies Sekisui Chemical Co., Ltd of Japan and DuPont (full name E. I. du Pont de Nemours and Company) of USA. Sekisui supply suitable interlayer material incorporating a blue shade band having 58% TTS, or alternatively a dark grey shade band having 47% TTS and 20% light transmission. DuPont supply suitable interlayer material incorporating a co-extruded blue/green shade band having 42% TTS and 8% light transmission.

As previously stated, the infra-red reflective coating may be any of the well-known types which are commonly used on vehicle windows. For instance, it may be a sputtered metallic coating applied under vacuum conditions, e.g. containing one or more silver layers.

Alternatively, it may be a pyrolytically deposited coating produced by a chemical vapour deposition process, comprising transparent conductive oxides, normally metal oxides.

Claims

Claims 1. A vehicle glazing having an infra-red reflective coating, at least one radiation transmissive area which is free from the coating and a shade band extending across the width of the glazing, wherein the shade band extends across the radiation transmissive area, and said area comprises at least 2% of the area of the glazing.
2. A vehicle glazing as claimed in claim 1, wherein the radiation transmissive area comprises at least 5% or 10% or 20% or 30% of the area of the glazing.
3. A vehicle glazing as claimed in claim 1 or claim 2, wherein the glazing has a plurality of radiation transmissive areas distributed across its width.
4. A vehicle glazing as claimed in any preceding claim, wherein at least one radiation transmissive area extends across the full width of the daylight opening area of the glazing, i.e. excluding any opaque areas.
5. A vehicle glazing as claimed in any preceding claim, wherein the at least one radiation transmissive area comprises at least 5% or 10% or 25% or 50% or 75% or 90% or 95% of the area of the shade band.
6. A vehicle glazing as claimed in any preceding claim, wherein the shade band extends over substantially all of the radiation transmissive area or areas.
7. A vehicle glazing as claimed in any preceding claim, wherein the at least one radiation transmissive area occupies substantially all of the daylight opening area of the glazing above the AS 1 line as defined in American National Standards Institute standard ANSI/SAE Z26.1-1996, Section 7.
8. A vehicle glazing as claimed in any preceding claim, wherein the glazing is laminated, and comprises at least two plies of glazing material with at least one ply of plastics interlayer material extending between plies of glazing material, and wherein the infra-red reflective coating extends over an internal surface of one of the plies.
9. A vehicle glazing as claimed in claim 8, wherein the shade band is provided by use of tinted plastics interlayer material.
10. A vehicle glazing as claimed in any preceding claim, wherein the total solar transmittance TTS (ISO 13837:2008, Convention A, wind velocity 4 mIs) of the shade band is less than 60%.
11. A vehicle glazing as claimed in any preceding claim, wherein the total solar transmittance TTS (ISO 13837:2008, Convention A, wind velocity 4 mIs) of the glazing is less than 50%, preferably less than 40%.
12. A vehicle glazing as claimed in any preceding claim, wherein the at least one radiation transmissive area is adapted to transmit signals to or from an antenna or receiving instrument, including a road tolling device, and/or a Global Positioning System (GPS) device, and/or an electronic key for locking or unlocking the vehicle or an external door or gate, and/or a vehicle separation monitoring device.
13. A vehicle glazing substantially as herein described with reference to and as illustrated in Figures 1 and 2 of the accompanying drawings.