ABSTRACT
The major in-service failure mechanism of modern solar control
coatings for architectural glass can be mechanical (e.g., scratch
damage). Many of these coatings are multilayer structures of
less than 100 nm thickness and different coating architectures
are possible (i.e., different layer materials, thickness and stacking
order). For high-performance solar control coatings deposited by
physical vapour deposition processes, the active layer is a thin
silver coating (∼8 nm thick) surrounded by anti-reflection coatings (e.g., ZnO, SnO2) and barrier layers (e.g., TiOxNy). Scratches are
often found during delivery of the coated glass (called transit
scratches) and it has been determined that the cause of the scratches
was the polymer balls sprayed onto the glass to separate sheets
while in transportation. This chapter highlights the importance
of using an appropriate simulation test for the transit scratches
and has determined that the polymer/coating friction and how it
controls through-thickness fracture and adhesion of layers within
the multilayer stack is critical in determining performance. To test
the adhesion of the coatings, coated samples have been subjected
to scratch tests using a range of indenters and the most visible
damage has been characterised. Through-thickness cracks were
observed and it was seen that the coating was stripped by the balls
at the weakest point in the coating stack. Microanalysis reveals this
weakest point to be the silver/zinc oxide interface in the materials
analysed in this study.
