This invention relates to glazing panels and particularly but not exclusively to laminated glazing panels intended for automotive side windows and rear windows.
Whilst the invention will be described with particular reference to laminated automotive side windows it may also be used in other applications, for example vehicle windscreens, vehicle backlights, vehicle sunroofs, other vehicle glazing panels and other laminated glazings.
Car sidelights have traditionally be provided as monolithic thermally tempered glass sheets having a thickness of between about 3 mm and 5 mm. The tempering is arranged to increase the mechanical resistance of the glass sheets and to ensure that if the glass sheets shatters it breaks into relatively small, blunt edged pieces so as to minimise potential injury.
It is also known to provide laminated glass sidelights having two sheets of glass laminated together by means of a sheet of polyvinyl butyral (pvb). It has always been considered that the glass sheets in such a structure must be tempered or at least hardened so as to induce a significant level of surface stress in order to provide sufficient mechanical resistance for handling and use and, for example, to withstand repeated slamming of a car door in which the glazing is mounted. The individual sheets of glass in such a structure generally have a thickness of less than 3 mm so as to minimise their weight and it has been difficult or impossible to induce the desired stresses in such thin glass sheets by many conventional manufacturing techniques.
Laminated sidelights comprising a single sheet of glass laminated with a single sheet of plastics, for example a polyurethane, have also been proposed. In addition to the durability and abrasion considerations for such glazings, the difficulty of providing the tempered characteristics perceived necessary with relatively thin sheets of glass has also been problematic.