Laminated safety glass sheets of the aforedescribed construction are increasingly used as sunscreens, especially for motor vehicles. For this purpose, the thin layer system on the carrier foil typically consists of up to three noble metal layers, preferably of a silver basis, which are embedded in dielectric layers (U.S. Pat. No. 4,799,745). Through the use of a thermoplastic foil as a carrier system, it can be insured that the carrier foil can match the curvature the glass sheets in the course of the heat treatment required for bonding them together. The matching deformation of the carrier foil is supported in that biaxially stretched thermo-plastic carrier foils are used. In connection with the selection of suitable carrier foils reference may be had to, for example, EP 0 077 672 B2 and EP 0 457 209 A2. Especially well suited for bent laminated safety glass sheets are the biaxially stretched carrier foils which are the subject of the older PCT application EP 96-04018 (WO97/10099, Flachglas Automotive GmbH). The two laminate layers serve for adhesive bonding of the carrier foil with the glass sheets and impart safety glass characteristics to the laminate.
For the production of laminated safety glass sheets of the afore-described construction, it has already been proposed to provide a foil prelaminate from the first bonding layer, the carrier foil provided with the thin layer system and the second bonding layer, in which the foils are pressed together, degassed and are prebonded with the use of heat (EP 0 535 128 B1). The thus formed foil laminate with air evacuated from between layers is laid between the two glass sheets, whereupon the laminate of the glass sheets and prefoil laminate is subjected to a degassing process as well as to a prebonding process. Finally, the laminate is finish bonded at increased temperature and higher pressure to the laminated safety glass. This process has been found to be suitable for slightly curved glass sheets. With greater bends, especially complex bends, when this process is carried out in practice, there can be wrinkle formations above all in the edge regions in the carrier foil which have been termed edge corrugations. To overcome this problem various approaches have already been proposed in which a prelamination of at least one bonding layer and the carrier foil is suitably preformed in a special apparatus (WO 94/04 357). Such a process is expensive and requires for each sheet type, a specially prefabricated form.
Tolerance-caused deviation in the glass sheets from the intended shape can give rise in the previously known process, apart from matching defects which influence the optical characteristics of the finished laminated safety glass sheet, to bond defects between the glass sheets and the foil prelaminate.