Development of a multilayer thin‐film solar control windshield

The trend in automotive glazing design has been towards more steeply sloped windshields with larger glass areas, resulting in greater transmission of solar radiation. Driver comfort, air conditioning load, and fabric deterioration are some of the challenges manufacturers of automotive glazing face because of these new designs. Ultraviolet and solar infrared radiation must be effectively reduced while visible light transmission must be maintained above 70% (the legal limit). The windshield surface, which receives up to 60% of the solar irradiation incident upon the vehicle glazing, is traditionally tinted, resulting in absorption and reradiation. The most effective means of reducing the solar heat load, however, is by using a multilayer coating which reflects the solar energy. The coating consists of two layers of silver sandwiched between antireflective dielectric metal oxide layers. The coating is applied to the inner surface of the outer glass light of the laminated windshield using the dc magnetron sputtering process. For the coating process to be both cost effective in manufacturing, and suitable for a variety of complex shaped windshields, the glass is first coated flat, and subsequently bent and laminated. The coating process can then be integrated into the windshield manufacturing process without limiting throughput. This multilayer coating, specifically developed to be bent on soda–lime–silicate glass, remains stable and uniform for complex, and small radius of curvature bends. The development of this coating in the laboratory, transfer into production, and integration into the windshield manufacturing process is described.