Vehicle crime is a continuing problem for both vehicle owners and vehicle manufacturers. In the UK alone hundreds of vehicles are stolen each day and many are broken into and have property stolen from within the vehicle. Furthermore, many vehicles are damaged by vandals. Vehicle manufacturers have made attempts to reduce the risk of the theft of or damage to vehicles by introducing a number of security features for vehicles such as sophisticated door locking systems, the provision of intruder alarms etc. Despite the introduction of such features the actions of thieves and vandals continue to place a heavy burden on vehicle owners.

The glazings of a vehicle may be seen as weak points with respect to the security of the vehicle and when broken, for example by impact/s with a brick or pick axe handle or the like, can provide a point of entry for thieves and/or vandals. Glazings for automotive use comprise safety glass which may be toughened or laminated. Toughened glass is one which has been heated and then cooled sufficiently rapidly to create compressive stresses at the surface, balanced by tensile stresses in the core. When broken it shatters into fragments with blunt edges. Laminated glass comprises a number of plies of sheet material and includes at least one glass ply which is adhered to a plastic layer. The glass, when struck, cracks but the splinters adhere to the plastic layer.

Both types of glazing provide some degree of intrusion resistance, with laminated glazings generally showing better performance than toughened glazings. A toughened glazing usually requires only one sharp blow to break it and allow access into the interior of the vehicle. Several blows may be required to penetrate a laminated glazing and it may take 30 seconds or more of continuous blows for the glazing to be penetrated to allow access into the vehicle. Toughened glazings are less expensive to manufacture than laminated glazings and in the UK most vehicles have a laminated windscreen to satisfy occupant retention requirements, the remainder of the vehicle's glazings being toughened. Aware of this and the relative intrusion resistance properties of laminated and toughened glazings, a person wishing to gain unlawful access into a vehicle usually attacks one of the toughened glazings.

Despite the fact that laminated glazings are more expensive to manufacture than toughened glazings, some cars are manufactured in which all glazings are laminated and it is more difficult to gain access to such a vehicle through one of its glazings than it would be to a vehicle which includes a toughened glazing. However, when incorporated into a vehicle there is no apparent difference in the appearance of toughened and laminated glass, and so a person wishing to gain unlawful access into a vehicle is just as likely to attack a laminated glazing of an"all laminated"vehicle, as a toughened glazing of a conventionally glazed vehicle. After a single sharp blow to the glazing the person would realise which type of glazing is under attack and in view of the time and effort required to penetrate a laminated glazing, it is believed that the person will be deterred from further attacking the glazing once they realise it is laminated, and possibly move on to find another vehicle containing a toughened glazing. Provided this is the case then access to the interior of the vehicle through the laminated glazing will be denied, but in all likelihood the glazing will have been damaged (for example the outer glass ply will probably be cracked) to the extent that it requires replacement, at a cost usually borne by the vehicle owner as a direct cost for a replacement laminated glazing or an indirect cost by way of increased insurance premiums.

In view of the above mentioned problems it is desirable to provide a vehicle glazing with means which act as a deterrent to a person wishing to gain unlawful access into a vehicle.

According to an aspect of the present invention there is provided a vehicle glazing comprising a plurality of plies of sheet material bonded to one another, the glazing having two outer surfaces and a plurality of inner surfaces each being major surfaces of the plies, wherein the glazing is provided with a mark indicating a security related attribute of the vehicle. Once the mark has been seen by someone attempting to gain unlawful access to the vehicle, it is believed that person will be deterred from attacking and hence damaging the vehicle.

The mark may be provided between the outer surfaces of the glazing and preferably on at least one inner surface of the glazing. Applying the mark in this way avoids it being soiled and also prevents it being damaged or removed from the glazing.

The glazing may comprise a plastic layer bonded between two glass plies and the mark may be incorporated in the plastic layer of the glazing which also avoids soiling of the mark and also prevents it being damaged or removed from the glazing.

The mark may be applied directly to a surface of the glazing, and suitable methods include printing, such as screen printing, pad printing or ink jet printing, or spraying (over a mask if necessary). Alternatively, it may be applied to a sticker which in turn is applied to a surface of the glazing.

In a laminated glazing according to the invention the mark preferably indicates the glazing is laminated to serve as a deterrent to discourage attack on the glazing from those attempting to gain unlawful access to the vehicle.

When incorporated into vehicles there is no apparent difference in the appearance of toughened and laminated glass, and so some individuals may be tempted to mark a toughened glazing to spuriously indicate it is laminated. Consequently it is desirable that a mark can be applied to a laminated glazing in such a way that it is evident that the glazing must be laminated. This may be achieved by applying the mark on to the glazing at least twice and on different surfaces, at least one being an inner surface. Application of the mark in this way utilises the effect of parallax and so it is evident that the glazing is laminated. The glazing may be provided with marks that are offset from each other and/or of different size.

According to a further aspect of the invention there is provided a vehicle glazing provided with a mark indicating a security related attribute of the vehicle wherein the mark is produced from a medium including a luminescent, fluorescent or reflective material. This aspect of the invention applies equally to laminated and toughened vehicle glazings. Vehicles that include toughened glazings have in the past been provided with stickers adhered to the surface of the glazing facing the interior of the vehicle that specify a security feature of the vehicle (for example the provision of an intruder alarm or other security feature). However, these stickers can be dif. ficult to see in the dark and therefore ineffective at night, a time when many vehicle crimes occur. When the mark includes a luminescent material, preferably a phosphorescent material, the mark is visible in daylight and also in darkness (for example at night or in a dimly lit car park). Fluorescent or reflective materials can assist in drawing attention to the mark when it is illuminated in darkness (for example by street lighting or torchlight).

The medium including a luminescent, fluorescent or reflective material may be applied directly to a surface of the glazing and suitable methods include printing, such as screen printing, pad printing or ink jet printing, or spraying (over a mask if necessary), or alternatively it may be applied to a sticker which in turn is applied to a surface of the glazing.

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 laminated vehicle glazing having a mark applied on an inner surface of the glazing.

Figure 2 is a fragmentary cross section of a laminated vehicle having a mark incorporated in a layer of the glazing.

Figure 3 is a fragmentary cross section of a laminated vehicle glazing having two marks applied on different inner surfaces of the glazing.

Figure 4 is a fragmentary cross section of a toughened vehicle glazing having a mark applied on one of its surfaces.

In the drawings like reference numerals refer to like integers. Referring to Figure 1, a laminated vehicle glazing generally designated 10 comprises a plastic interlayer 12, such as polyvinylbutyral (PVB), bonded to glass plies 14 and 16. Each ply of the glazing has two substantially parallel major surfaces each of which has an area significantly greater than any of the other faces of the ply. The glazing has two outer major surfaces (14a, 16a), hereinafter referred to as"outer surfaces", and a number inner major surfaces (12a, 12b, 14b, 16b), hereinafter referred to as"inner surfaces", with the outer surfaces facing the interior and exterior of the vehicle respectively, and each inner surface being in contact with another inner surface of another component of the glazing. In the embodiment shown in Figure 1 the glazing has outer glass surfaces 14a and 16a, inner glass surfaces 14b and 16b which are in contact with inner surfaces 12a and 12b respectively of the plastic interlayer.

Prior to lamination a mark in the form of a logo which indicates the glazing is laminated, is applied to the inner surface 14b of outer ply 14 by screen printing. The ink used to print the mark 18 may be a ceramic ink or a non-ceramic ink. Ceramic inks are commonly used on vehicle glazings and are more durable than non-ceramic inks, but a glazing printed with a ceramic ink requires firing at a temperature in the region of 600 ° C to cause the ceramic material to become fused to the glazing. However, in this embodiment the ink is non-ceramic and contains a luminescent pigment, in particular a phosphorescent pigment, which has a long persistence time as hereinafter defined. A luminescent material (and hence all phosphorescent materials) is one in which excitation energy is absorbed, stored and emitted long after the exciting energy source has been removed.

The expression"persistence time"is used herein to refer to the time taken for the brightness of the phosphorescent component to decay from its maximum value to 10% of that maximum value after the excitation source is removed; a long persistence time is a time of one second or more. However, while persistence times of one second are long in comparison with persistence times of certain phosphorescent pigments, such as those used in cathode ray tubes, it is preferred to use pigments with persistence times of several hours.

It is preferred to use LUMILUX N phosphorescent pigments available in commerce from Riedel-de Haen of Seelze, Germany. These pigments emit light not only during but also for a long time after the source of excitation is removed; the emission is perceptible to adapted eyes for between 10 and 30 hours depending on the particular pigment employed.

A range of emission colours is available, including red, green and yellow.

The ink for printing the mark is made up by adding a proportion of the desired LUMILUX N pigment with a clear epoxy varnish such as that sold under the trade name POLYSCREEN, available in commerce from Sericol UK Ltd, England. The ink is screen printed onto a surface of a 2.1 mm glass ply and allowed to cure, which may be at room temperature for 24 hours, or for 30 to 40 minutes at 150°C. Once cured, a 0.76 mm PVB interlayer is sandwiched between the glass ply which has been printed on and another 2.1 mm glass ply. The arrangement is such that the printed surface of the glass ply is in contact with the PVB interlayer. Air is removed from between the assembled plies by conventional <BR> <BR> <BR> <BR> means, and the assembly is heated in an autoclave at a pressure in the range 8 x 105 Pa to 15<BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> x 105 Pa (8 to 15 bar) and a temperature in the range 135 to 150°C for a period in the range 15 to 45 minutes. The finished glazing is suitable for use as a vehicle glazing.

Suitable sources of excitation for LUMILUX N pigments are uv light, daylight and artificial light, and the emission from the pigment is perceptible to adapted eyes for between 10 and 30 hours depending on the particular pigment employed. Thus, when applied to a vehicle glazing the mark will be visible in daylight and also in darkness, for example at night or in a dimly lit car park, a time when many vehicle crimes occur. Indeed, during the night light from artificial lighting, such as that from the headlights of other passing vehicles or artificial lights provided in car parks, incident on the mark will increase the energy absorbed within the pigment and hence the light emitted therefrom.

A fluorescent material (one which absorbs light of short (invisible) wavelength and emits light of longer (visible) wavelength) or a reflective material may be added to the ink composition or may replace the phosphorescent material in the ink composition. These materials may assist in drawing attention to the mark when it is illuminated in darkness (for example by street lighting or by torchlight).

The mark may be applied to an outer surface of the glazing and where this is done it is preferable to apply the mark on the surface of the glazing facing the interior of the vehicle where it will not be subjected to external weathering and is less likely to be damaged or removed by vandals. However, it is preferable to apply the mark between the outer surfaces of the glazing, ie to an inner surface of the glazing such as an inner glass surface as described with reference to Figure 1 (although the mark may equally applied on the inner surface of a plastic layer of the glazing), or to incorporate it into a layer of the laminate as shown in Figure 2. In Figure 2 a section of plastic interlayer 12 has been cut out and a substrate 19 which includes a representation of the mark is inserted into the cut out section. Application of the mark on an inner surface or within a layer of the laminate avoids soiling of the mark and also prevents it from being damaged or removed from the glazing.

In this particular embodiment the mark printed on the glazing is in the form of a logo to indicate the glazing is laminated, however, other forms of mark may be applied to the glazing to indicate other security features of the vehicle.

It will be appreciated that suitable methods of applying the mark directly to a surface of the glazing may be used and include screen printing, pad printing, ink jet printing or spraying (over a mask if necessary). Alternatively the mark may be applied to a sticker which is then adhered to a surface of the glazing by a suitable adhesive.

The mark may be applied to laminated vehicle glazings, in particular curved glazings, which commonly comprise two glass plies bonded by a plastic layer. The glass ply facing the exterior of the vehicle normally has a thickness of 1.5 mm or more to provide improved resistance to stone chipping. The glass ply (or plies) of such a laminate may be semi- toughened which is especially desirable when the laminate is to be used for opening sidelights in vehicle doors which are required to withstand slamming of the door with the window unsupported on at least one edge. A laminated vehicle glazing may alternatively comprise a single glass ply bonded to a plastic layer or it may comprise a combination of multiple glass plies and multiple plastic layers bonded to one another.

The mark is usually applied to the glazing only once but it may be applied more than once. Figure 3 shows a glazing in which a mark has been applied twice. In addition to mark 18 which has been printed on surface 14b, a further mark 18'is applied on surface 16b in such a way that the two marks 18 and 18'are slightly offset from each other. Applying the mark in this manner utilises the effect of parallax and would indicate to a person looking at the glazing that the mark has been applied to more than one surface of the plies and hence it would be evident that the glazing comprises more than one ply (ie it is laminated). This manner of representation of the mark would also serves as a deterrent to discourage attack on the glazing from those attempting to gain unlawful access to the vehicle.

When a non ceramic ink is applied to a glass ply of a laminated glazing which is curved and/or toughened (including being semi-toughened), the glass ply or plies are bent and/or toughened prior to application of the mark. This avoids heat damage to the ink which may be caused during the bending process. However, when a ceramic ink is used the mark is applied prior to bending and/or toughening of the glass ply or plies and the heat required to bend and/or toughen the ply or plies also causes the ceramic material to become fused to the glass ply.

It will be appreciated that laminated vehicle glazings include plastic layers other than PVB. Polycarbonate, acrylic and polyurethane are some examples.

Referring to Figure 4, a toughened vehicle glazing 20 has a mark 18 applied to one of its outer surfaces. The mark indicates an attribute of the vehicle relating to the security if the vehicle. The ink used to print the mark may be a ceramic ink or a non-ceramic ink that contains a luminescent material (in particular a phosphorescent material), a fluorescent material and/or a reflective material each of which aids in the mark being visible in darkness.

As previously described light from artificial lighting, such as that from the headlights of other passing vehicles or artificial lights provided in car parks, incident on the mark will increase the energy absorbed within the phosphorescent pigment and hence the light emitted therefrom. The fluorescent and/or reflective materials may also assist in drawing attention to the mark when it is illuminated in darkness (for example by street lighting or by torchlight).

In a preferred embodiment the ink is non ceramic and contains a phosphorescent pigment as hereinbefore described. Preferably the mark is applied to the surface of the glazing facing the interior of the vehicle where it will not be subjected to external weathering and is less likely to be damaged or removed by vandals.

The toughened glazing may or may not be curved and when a non ceramic ink is used, the mark is applied after the toughening process (and bending process where appropriate) to avoid heat damage to the ink which may be caused during the toughening/bending process.

However, when a ceramic ink is used the mark is applied prior to the toughening/bending process and the heat required to toughen/bend the glass also causes the ceramic material to become fused to the glass.

It will be appreciated that when applying a mark to a either a toughened or a laminated vehicle glazing, suitable methods of applying the ink directly to a surface of the glazing may be used and include screen printing, pad printing, ink jet printing or spraying (over a mask if necessary). Alternatively the mark may be applied to a sticker which is then adhered to a surface of the glazing by a suitable adhesive.