The defects of polyester films used for glass curtain walls, such as discoloration, peeling, and wrinkling, are thought to be caused by degradation. This occurs in a short period (approximately 1/10) of the conventional service lifetime. A comprehensive investigation demonstrated that extremely low ultraviolet (UV) absorber (2,2’,4,4’-tetrahydroxybenzophenone) content in the adhesive coating caused the defects, instead of degradation. To increase bond strength, adhesives are blended using ester compounds with a polar group and small molecular weight, and hence, are easily degraded. Therefore, excess UV absorber addition is essential for extending the lifetime of the film and its function.
