GB2339405A - Laminated glazing - Google Patents

Description

1 2339405 LAMINATED GLAZINGS - This invention relates to glazings, and in

particular to laminated glazings having a high intrusion resistance.

Glazings for automotive use comprise safety glass which may be laminated (widely used for windscreens) or toughened (widely used for sidelights and backlights). Both types of glazing provide some degree of impact resistance, with laminated glazings having certain advantages over toughened glass so that, although laminated glazings are more expensive to manufacture than toughened glass, it would be desirable for all automotive glazings to be laminated to give improved intrusion resistance and to improve occupant retention in collisions. However, while conventional laminated glass (using polyvinylbutyral interlayer) provides better intrusion resistance than toughened glass, it will not resist a sustained attack especially when (as in the case of opening side lights) it is not permanently secured around its periphery by the glazing system used.

Attempts have been made to improve the impact resistance of laminated glazings by incorporating polycarbonate as an impact resistant ply in the laminate. Unfortunately, a polycarbonate ply at least 3 mm thick is required because polycarbonate is prone to stress cracking at lower thicknesses. However, while a 3 nim polycarbonate layer provides sufficient impact resistance for most purposes in a laminated glazing, when a 3 mm polycarbonate is laminated between glass panes (to provide the durability required for most uses) the resultant glazing becomes relatively thick and heavy, making it unsuitable for general automotive use.

Another form of impact resistant laminated glazing available in high performance products, such as aircraft windows, is known as a bilayer which comprises a single glass ply 2 bonded to a plastics layer. The plastics layer may comprise a number of individual plies with each ply having at least one function it lends to the glazing, for example a ply may have impact resistant properties or perhaps resistance to scratching. The plastics layer includes a rigid polymeric ply, for example acrylic or polycarbonate, which has impact resistant properties. These bilayer constructions are arranged in use so that the polymeric ply faces the inside of the aircraft and when impact of the glazing occurs, dangerous spall is avoided within the aircraft cabin. In providing the desired properties for use as an impact resistant glazing these bilayers: are typically more than 5 mm thick. Such a construction would be relatively thick and relatively heavy making it unsuitable for general automotive use.

Our co-pending application PCT/GB98/01113 discloses an impact resistant glazing comprising a ply of a rigid thermoplastic polyurethane laminated between two glass plies. Such a glazing is suitable for automotive use and has reduced thickness and weight over known impact resistant automotive glazings. In some glazing applications, for example external glazings, it may not be necessary for the inner surface of the glazing (for example in an automotive glazing the surface facing the interor of the vehicle) to be as durable as the external surface. Tbus we have now found that the weight and thickness of impact resistant glazings may be further reduced by incorporating a rigid thermoplastic polyurethane ply in a bilayer construction.

According to an aspect of the present invention there is provided a bilayer glazing comprising an impact resistant ply of rigid thermoplastic polyurethane bonded to a glass ply. The glazing may be for automotive use and arranged in use so that the polymeric ply faces the inside of the vehicle, thereby avoiding dangerous spall within the vehicle when impact of the glazing occurs.

3 An impact resistant layer for use in an automotive multiple layer glazing must have resistance to penetration properties and also be rigid. Rigidity is required because in multiple layer glazings such as laminates, the interlayer provides a certain degree of stiffness to the glazing. A laminated glazing having a non-rigid interlayer, such as PVB, loses its stiffness once the glass plies have been fractured, for example by a blow with a harnmer. Once the glazing has been penetrated it can be easily removed from its frame. When a rigid interlayer, such as polycarbonate, is used in a multiple layer glazing, the integrity of the glazing does not deteriorate when the glass ply is fractured and removal of the glazing from its frame is not made any easier. 11us a rigid impact resistant layer can be defined as one which when employed in a multiple layer glazing does not compromise the integrity of the glazing once the glass plies have been fractured. The rigidity of a material may also be measured in terms of its tensile (Youngs) modulus and the family of rigid thermoplastic polyurethanes have a tensile modulus of greater than 500 MPa, and the preferred materials have a modulus of at least 1000 MPa so that adequate stiffness can be achieved using layers no more than about I mm thick. In an especially preferred embodiment the tensile modulus of the impact resistant layer is about 2000 MPa or greater. The modulus values referred to herein are as measured in accordance with ASTM D638.

Preferably a layer resistant to scratching is applied to the unbonded side of the rigid thermoplastic polyurethane to enhance the durability of the glazing.

The use of a thermoplastic material for the impact resistant layer facilitates the production of curved glazings, as it may be thermoformed to the required shape of the glazing during lamination.

4 The rigid thermoplastic polyurethane ply will normally have a thickness of at least 0.20 nun (in order to provide adequate impact resistance) with thicknesses in- the range 0.5 to 2mm, especially 0.5 to 1.5 rnm being appropriate for most applications.

The thermoplastic polyurethanes have poor resistance to ultra violet radiation, presumably due to inclusion of aromatic units in the polymer chains (the flexible thermoplastic polyurethanes currently used in aircraft glazings are aliphatic in character, and do not suffer the same deterioration on exposure to ultra-violet radiation). Thus they would not normally be considered suitable for use in external glazings. However, these materials may be satisfactorily protected from ultra-violet radiation so that it becomes suitable for external use by incorporating it in a bilayer glazing with an ultra-violet absorbing and/or reflecting ply outside (i.e. between the rigid thermoplastic ply and the source of incident ultra-violet light, normally the sun) the rigid thermoplastic ply, providing a durable, impact resistant glazing, suitable for automotive use.

The ultra-violet reflecting or absorbing ply or plies used should transmit no more than about 20% (measured in accordance with ISO 9050) of the incident ultra-violet solar radiation and preferably less than 10% and especially less than 5%. The non-transmitted ultra-violet will normally be substantially absorbed by a ply or plies of the glazing on the outside of the impact resistant ply, although it may be at least partially reflected, for example, by incorporating a reflective coating, such as a metal coating, in the Iarrdnate outside the impact resistant ply.

A pane of high performance solar control glass (such as OPTIGRUN 90 or EZKOOL glass, each glass available in commerce from companies within the Pilkington Group) may be used to absorb ultra-violet light, usually in conjunction with an additional ply, between the glass ply and the impact resistant layer, of an ultra-violet absorbing interlayer material. Such an interlayer material may itself be a thermoplastic polyvinylbutyral or polyurethane, normally an aliphatic polyurethane and much softer than the rigid thermoplastic polyurethane used for the impact resistant ply.

While certain plastics, such as polycarbonates, polyurethanes and polyvinylacetals have properties which make them useful in glazing applications, for most glazing applications it is preferred to use such plastics plies in conjunction with a glass ply or plies because of the good optics and high durability of glass. Where the plastic plies are thermoset, as for example, acrylics, they may be bonded to glass either by incorporating a thermoplastics interlayer ply between the thermoset plastic ply and the glass and autoclaving, or by using a curable "castinplace" interlayer material to form an interlayer in-situ between the thermoset ply and the glass, the interlayer so formed adhering to both the thermoset ply and the glass and bonding them together. Where the plastics plies are thermoplastic, they are normally bonded directly to glass by heating the plies together under pressure in an autoclave.

T'hus, it was anticipated that the rigid thermoplastic polyurethanes used in the present invention would be bonded directly to the glass ply by autoclaving, avoiding the need to use a separate bonding layer. However, it has been found that much better adherence can be achieved, with the glazing displaying greatly enhanced energy absorption and impact resistance, if the rigid thermoplastic polyurethane ply is bonded to the glass ply using a relatively low modulus interlayer material, preferably a thermoplastic material to which the glass and rigid thermoplastic plies are bonded, by heating under pressure.

It is found that the use, as an adhesive, of an interlayer, preferably a preformed thermoplastic interlayer, of low modulus (for example, less than 100 MPa, preferably less than 10 NTa) between the glass and the high modulus rigid polyurethane prevents cracks propagating through an outer glass ply into the rigid interlayer; it is believed that a low tensile modulus adhesive does this by blunting the crack tip. A thin adhesive layer having a thickness 6 of as little as 10 microns and ideally about 100 n-dcrons or more can be used for this purpose, although the ready availability of suitable soft adhesive materials in greater thicknesses e.g. 0.38 mm may make it more convenient to use somewhat thicker layers (for example up to 0.4 mm) than necessary. Preferably the low modulus adhesive interlayer is a thermoplastic interlayer, especially a polyurethane. In an automotive glazing according to the present invention it is generally preferred to use a polyurethane interlayer material since, as discussed in our co- pending application PCT/GB98/01113, commercially available polyvinylbutyral interlayer materials generally provide less satisfactory impact resistance at low temperature.

The glass ply will normally have a thickness of at least 0.7 nu-n and preferably at least 1. 1 mm and especially a thickness of about 1.5 mm or more to provide improved resistance to stone chipping. The glass ply may be semi-toughened; this is especially desirable when the laminate is to be used for opening sidelights in vehicle doors, and are required to withstand slamming of the door with the window unsupported on at least one edge. On the other hand, to avoid excessive weight and thickness, it will generally be desirable, for automotive glazings, to use a glass ply of thickness not greater than about 2.6 mm, commonly no greater than 2.3 mrrL As will be appreciated from the above discussion, use of the structure of the present invention permits the production of durable laminates, including curved laminates, with good impact resistance and intrusion resistance, with thicknesses no greater than about 4 mm (say 4 mm 0.5 mm) or even thinner (say 3 mm 0.5 nun). Thus not only does the reduced thickness possible with the glazings of the present invention save weight and material, but enables the glazings to be fitted into openings (especially openings in motor vehicles) designed to be glazed with conventional non-dnal 4 mm or 3 mm glazings. However, some vehicle 7 openings are designed to be glazed with glazings nominally 6mm or more and so the glass ply may be up to 5mm or more.

Embodiments of the invention will now be described with reference to the accompanying drawings in which:

Figure 1 is a fragmentary cross section of a multiple layer glazing according to the present invention.

Figure 2 is a schematic side view of an asymmetric automotive glazing in a frame showing the pattern of impact points required in BS AU 209 (part 4:1995).

Figure 3 is a fragmentary cross section of a modified version of the glazing of Figure I additionally incorporating a reflective metal layer.

Figures 4 to 7 are graphs, as explained more fully below, showing changes in yellowness index with prolonged exposure to ultra-violet radiation of various laminate samples incorporating a rigid thermoplastic polyurethane ply.

Referring to Figure I a bilayer glazing generally designated 10 comprises a glass ply 20 bonded to a plastics layer 30. The plastics layer comprises a low modulus adhesive interlayer 3 1, a rigid impact resistant ply 32 and a layer 33 resistant to scratching. When used in automotive applications the glazing is arranged with the glass ply facing the exterior of the vehicle.

A rigid impact resistant material particularly suitable for use in the present invention is sold under the brand name ISOPLAST, available in commerce from the Dow Chemical Company, and is a rigid thermoplastic polyurethane sensitive to ultra-violet radiation having a tensile modulus of about 2000 MPa.

The low modulus interlayer 31 may be of a thermoset resin cast and cured in situ between impact resistant ply 32 and glass ply 20, but is preferably of preformed thermoplastics 8 interlayer material used to adhere the impact resistant ply to the glass ply by heating under pressure. 'Me thermoplastic interlayer material may be a low modulus thermoplastic polyurethane or a thermoplastic polyvinylbutyral, commercially available interlayers of both materials generally having a significant ultra-violet absorption. Examples of low modulus interlayers that are particularly suitable for use in the present invention are Morton PE 399 (available in commerce from Stevens Urethane of Holyoke, Massachusetts, USA) or Tecoflex AG-8451 primerless film (available in commerce from Lehmann & Voss & Co of Hamburg, Germany). The Tecoflex primerless film has particularly good ultra-violet absorbing properties (with a 0.38 mm thick film absorbing substantially all the incident solar ultra-violet radiation measured in accordance ISO 9050) and is preferred as it may be used in thin layers without any additional absorption provided by the glass ply or an additional reflecting metal layer. Tecoflex AG-8451 available from Lehmann & Voss & Co, Germany.

The glass ply 20 may be of an iron containing solar control glass, such as OPTIGRUN green glass, which contains about 0.90% by weight total iron (calculated as R203), to provide or supplement the ultra-violet absorption provided by interlayer 31. When the ultra-violet absorption provided by the glass is sufficient on its own to satisfactorily protect the ISOPLAST ply from incident solar ultra-violet radiation, for example when a high light transmission is not required and a thick outer ply is satisfactory, the glass ply may be sufficient on its own to satisfactorily protect the impact resistant ply from ultra-violet solar radiation, and it will be unnecessary for the interlayer material used to absorb in the ultra-violet. In other cases however, it may be important to supplement the ultra-violet absorption of the glass by using ultra- violet absorbing interlayer material as described above, or by using an ultra-violet reflecting coating as described hereinafter.

9 The layer 33 resistant to scratching applied to the unbonded side of the rigid thermoplastic polyurethane enhances the durability of the glazing One such suitable layer is in the form of a coating and is available from SDC Coatings Inc, Anaheim, California, USA. Other conventional layers resistant to scratching may be used, examples of which are a self healing polyurethane layer, or a hard coat which may be applied to a layer of polyethylene tereplithalate. The layer resistant to scratching and/or the adhesive layer used to bond it to the rigid thermoplastic polyurethane (if required) may contain an ultra violet absorber In order to demonstrate the impact resistant properties of a bilayer glazing of the present invention a number of samples were constructed and tested. 100 mm diameter pre-cut discs of 2.1 nun float glass, 0.38 mm thick Tecoflex AG-8451 and ISOPLAST nominally 1 mm thick, were placed together side by side, vacuum bagged and autoclaved for 40 minutes at 125C and 150 psi. A disc of 2.1 mm float glass was placed against the exposed ISOPLAST face during autoclaving to prevent marking of the softened ISOPLAST. The specimens were placed in a test jig and were tested using a Rosand IFW5 Instrumented Falling Weight Impact Tester and the 100 nun diameter test specimen was impacted on its glass surface by a 20 mm diameter spherically tipped hardened tool-steel probe which is attached, via a piezoelectric force transducer, to a mass. This mass may be varied between I and 50 kg and may be dropped freely from a height of up to 2m, giving a maximum impact velocity of 6 m/s and a maximum impact energy of approximately 1000J. In the present tests the mass used was 25 kg which was dropped under gravity from a height sufficient to impart enough energy to the mass to penetrate the samples.

The test was configured so that there is excess energy available and the test specimen was fully penetrated by the probe. The excess energy was then absorbed by hydraulic shock absorbers and the mass was brought to rest. The velocity of the probe was measured optically immediately before impact and the force exerted on the probe by the specimen was detected by the force transducer and was sampled digitally through the impact event, From the known mass, the velocity of the probe at the moment of impact and the measured force, the instantaneous energy absorbed by the specimen can be calculated throughout the impact event. To permit its storage and subsequent processing, the analogue signal from the force transducer was converted into a digital format by a 12 bit, 4000 data point data recorder which measured the amplitude of the force signal at regular, discrete intervals.

The results are shown in the following table and it should be noted that the data for energy absorption has been normalized to 1 mm ISOPLAST thickness.

Sample ISOPLAST Bilayer Energy absorption No thickness 'Mickness for penetration ffim (MM) 1 0.963 3.473 58.1 2 0.985 3.496 47.3 2 0.989 3.502 58.7 4 0.987 3.509 53.2 0.996 3.518 48.4 6 0.989 3.526 48.9 For comparison purposes a bilayer sample comprising a disc of 2.1 mm float glass, 0.38 mm Tecoflex AG-8451 and 1 mm polycarbonate was constructed and tested in the same manner. The value for energy absorption for penetration of the sample was 42 Joules, a figure less than that for all the ISOPLAST bilayer samples. Of course such a polycarbonate bilayer would not be usable as an impact resistant glazing in view of the stress cracking problems encountered with polycarbonate as previously discussed.

In an attempt to define impact resistant glazings it should be noted that the energy absorption for penetration of toughened glass is a figure slightly above 0 Joules and a typical laminated windscreen (2.1 mrn glass plies laminated with 0.76 mm PVB) has a figure of 19.6 Joules. Such a typical windscreen is recognised as having desirable impact resistant properties and so a glazing with a value of energy absorption for penetration greater than that of a typical laminated windscreen can be defined as an enhanced impact resistant glazing.

In further testing glazing samples were fabricated to fit into a Range Rover P38 front driver's door and was held in place with the standard Range Rover framing system. The first bilayer sample comprised 2.1 mm semi-toughened float glass, 0.38 mm thick Tecoflex AG8541 and 1 mm thick ISOPLAST and was tested to see whether it complied with the British Standard BS AU 209 (part 4:1995). This involved subjecting the glazing with a 9.5 kg pendulum to one impact at each of the impact points of the pattern as shown in the circle 54 of Figure 2, which schematically shows an asymmetric automotive glazing 50 in a frame 52 such as a door frame. For a glazing to comply with BS AU 209 (part 4:1995) both of the following statements must apply after the impact testing as described above:- (a) Ilere shall be no separation between the glazing and the body aperture large enough to permit the free passage of a sphere 40 nun 2 mm in diameter.

(b) It shall not be possible to pass a sphere 40 mm 2 mm in diameter freely through any tear or split which develops within the glazing materials.

After receiving the five impacts the sample remained intact in the door frame thus complying with the Standard. After a further twenty impacts on the centre impact point the sample was still intact with only small amounts of glass having been removed from the sample 12 from the impacts. The sample was then repeatedly struck manually with a hammer and it took a further ten blows before the sample was penetrated.

A second bilayer sample comprised 2.1 mm serrii-toughened glass, 0.38 mm thick Morton PE 399 as the adhesive layer and 0.6 mm thick ISOPLAST. On testing to see whether it complied with BS AU 209 (part 4:1995) the bilayer not only stood up to the five impacts required to comply with the Standard, but a further twenty impacts on the centre impact point and five manual impacts from a hammer failed to penetrate the sample.

For comparison purposes a sample was also fabricated to fit into a Range Rover P38 using 2.1 mm serni-toughened glass plies and 0.76 mm PVB (similar to the construction of typical Iarriinated windscreens). "Me glazing remained intact after the five impacts required by BS AU 209 (part 4:1995) but was showing some signs of flexibility. The pendulum fully penetrated the glazing after a further five impacts on the centre impact point.

It should also be noted that a conventional automotive toughened sidelight would break from a single impact under the testing conditions of BS AU 209 (part 4:1995).

Referring to Figure 3 of the drawings, a further modified form of the glazing of Figure 1, generally designated 40, comprises plies 20,31, 32 and 33 corresponding to the same numbered plies of Figure 1, with two additional plies 41 and 42 between adhesive interlayer 31 and glass ply 20. Ply 41 is a film bearing a reflecting m etal layer, for example is a polyester film bearing a thin silver coating, bonded to the glass ply by low modulus adhesive interlayer 42. 1n use, the reflecting metal layer serves as a solar control layer, reducing the total solar energy (heat) transmitted by the windows. It also reflects a proportion of the incident ultra- violet radiation. It will be appreciated that, when such a coating is present, it is not necessary for the glass ply and/or low modulus interlayer to provide as strong ultra-violet absorption to protect impact resistant ply 32 from unacceptable deterioration as would otherwise be necessary.

13 Figures 4 and 5 show the yellowing effect of exposing samples of rigid thermoplastics alone or protected within a laminate to ultra-violet (UVA) radiation using an accelerated weathering tester available from The QPanel Company of Ohio, USA. The change in yellowness index (YID) on exposure of three samples as detailed below was measured according to ASTM D1925 using a Pacific Spectragard Color System Instrument Sample I was of unprotected ISOPLAST 300 series 1 mm thick. In sample 2, the 1 mm ISOPLAST was laminated between two plies of 2.1 mrn clear float glass using a 0.38 mm thick interlayer of Tecoflex AG 8541 low modulus thermoplastic interlayer between the rigid thermoplastic ply and each glass and the lay up vacuum bagged and heated in an autoclave for 40 minutes at 125QC and 150 pounds per square inch. Sample 3 was similar to sample 2, but with the clear glass plies replaced by 2.1 mm. plies of EZ- KOOL iron-containing solar control glass.

The results show that both laminate structures provide excellent protection to the rigid thermoplastic ply with the change in yellowness index reduced from about 40 (with no ultraviolet absorbing layer) after 2000 hours to less than 1. Sample 3, using EZ-KOOL glass, gave even better results than Sample 2 using clear glass, although the difference was less than a factor of 2.

Figures 6 and 7 show the yellowing effect when sample Ian-dnates incorporating rigid thermoplastics ply were subjected to accelerated weathering in a XENOTEST 150S instrument, available from Heraeus Instruments, Germany. The instrument was set with a 6-1 (ir to uv filter configuration) and the rain spray cycle set to 30 minutes spray followed by I hour dry, and the Samples irradiated at 1570W/r-n2 In Samples 4 and 5 (Figure 6), a I mm ply of ISOPLAST was sandwiched between 2.1 nun glass plies without adhesive interlayers. In Sample 4 the plies were of clear glass and in 14 Sample 5 the plies were of EZ-KOOL glass. The changes in yellowness index when the samples were irradiated in the XENOTEST instrument as described above are shown in Figure 6; after about 600 hours, the yellowness index for both samples was more than 20.

In Samples 6,7 and 8, 1 mm plies of ISOPLAST rigid thermoplastic were laminated between two 2.1 mrn glass plies using low modulus thermoplastics polyurethane interlayers. In Sample 6, the glass plies were of clear float glass and the interlayers of 0. 15 mm PE 399. In Sample 7, the glass plies were of EZ-KOOL glass and the interlayers of 0. 38 mm TECOFLEX AG 8541. In Sample 8, the glass plies were of EZ-KOOL glass and the interlayers of 0.15 mm PE 399. After 1000 hours irradiation, each of the samples had a change in yellowness index value of less than 4. Surprisingly, the yellowness index for Sample 7 actually appeared to fall on irradiation, presumably due to experimental error. When comparing the results, it can be seen that while glass provides a degree of protection from ultra-violet irradiation, with the iron-containing solar control glass providing enhanced protection (comparing Samples 6 and 8) it may not always be sufficient on its own, but much better results may be achieved using ultraviolet absorbing interlayer in combination with the glass.

Comparing the results obtained above with the results of natural weathering, we concluded that a change of yellowness index measured to ASTM D1925 of more than 20 after 1000 hours in the XENOTEST testing described ab ove would suggest that the laminate would be unsuitable for automotive use. Preferably this value is no more than 8.

Irradiation was repeated using low modulus polyvinylbutyral interlayers in place of the polyurethane interlayers. Again, substantial protection of the rigid thermoplastic ply from yellowing was observed, although we prefer to use polyurethane interlayers as commercially available polyvinylbutyral interlayer gave poor impact performance at temperatures significantly below average ambient In each of samples 2 to 8 the rigid thermoplastic ply is sandwiched between two glass phes and only one surface of the glazing is exposed to the ultra violet source. T'hus it can be seen that these results would apply equally to constructions of the present invention arranged such that the glazing is exposed to ultra violet through the glass surface of the bilayer (to simulate the effect of sunlight on the glazing as if it were an external glazing).

It will be appreciated that uv-absorbing species may be loaded into other suitable adhesive interlayers to give them to required ultra-violet absorbing properties.

It will further be appreciated that in external glazings of the multiple layer type it is the outer side of the glazing that will usually be exposed to more ultra-violet radiation than the inner side from direct sunlight. Consequently most of the protection to ultra-violet radiation should be provided by the outermost ply or plies of the glazing, but it is not a departure from the present invention for a multiple layer glazing to include an ultra violet protective layer on the interior side of the glazing.

It will also be appreciated that a thinner layer of rigid thermoplaspolyurethane may be used, down to a thickness of 0.2 mm. Furthermore, for specialist automotive applications the rigid thermoplastic polyurethane layer may be of a thickness of greater than I nun.

It will still further be appreciated that thinner glass plies may be used down to a thickness of 1.8 mm, 1. 1 mm or even 0.7 mm. It will also be appreciated that the glass plies may be sen-d-toughened prior to being made up into a bilayer which is particularly desirable in opening sidelights as previously described.

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Claims (19)

Claims

1. A bilayer glazing comprising an impact resistant ply of rigid thermoplastic polyurethane, bonded to a glass ply.

2. A bilayer glazing as claimed in claim 1 wherein the impact resistant ply of rigid thermoplastic polyurethane is bonded to the glass ply by an adhesive interlayer.

3. A bilayer glazing as claimed in claim 2 wherein the adhesive interlayer is ultra violet absorbing.

4. A bilayer glazing as claimed in claim 2 or claim 3 wherein the adhesive interlayer is a low modulus interlayer.

5. A bilayer glazing as claimed in any of claims 2 to 4 wherein the adhesive interlayer is of thermoplastic polymer.

6. A bilayer glazing as claimed in claim 5 wherein the adhesive interlayer is of thermoplastic polyurethane.

7. An intrusion resistant automotive bilayer glazing as claimed in any preceding claim.

8. An automotive bilayer glazing as claimed in claim 7 wherein the glass ply has a thickness in the range 1.5 to 2.6 mm.

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9. An automotive bilayer glazing as claimed in any of claims 7 to 8 wherein the rigid thermoplastic polyurethane, ply has a thickness in the range 0.5 to 1.5 MrrL

10. An automotive bilayer glazing as claimed in any of claims 7 to 9 having a thickness of about 4 nun.

11. An automotive bilayer glazing as claimed in any of claims 7 to 9 having a thickness of about 3 mm.

12. An automotive bilayer glazing as claimed in any of claims 7 to 11 including a reflective layer.

13. An automotive bilayer glazing as claimed in claim 12 wherein the reflective layer is a metal layer

14. An automotive bilayer glazing as claimed in any of claims 7 to 13 having a layer resistant to scratching applied to the interior side of the rigid thermoplastic polyurethane ply.

15. An automotive bilayer glazing as claimed in any of claims 7 to 14 including a layer containing an ultra violet absorber on the interior side of the rigid thermoplastic polyurethane ply- 18

16. An automotive layer glazing as claimed in any of claims 7 to 15 being a windscreen, sidelight, rearlight or rooflight.

17. An automotive bilayer glazing as claimed in any of claims 7 to 16 wherein the glass ply is serni-toughened.

18. An automotive bilayer glazing as claimed in any of claims 7 to 175 wherein the glass ply has solar control properties.

19. An automotive bilayer glazing as hereinbefore described with reference to and as illustrated in the accompanying drawings.

19. An automotive bilayer glazing as claimed in any of claims 7 to 18 further including a solar control ply being a ply of polyethylene terephthalate carrying a reflective metal coating.

18. An enhanced intrusion resistant glazing as claimed in any preceding claim.