Comparison of the nanomechanical and nanoscratch performance of antiscratch layers on organic lenses

The combination of transparency, toughness and low weight makes polycarbonate (PC) very attractive for eyewear applications. However, PCs are easily scratched in the normal use environment because of their softness. Antiscratch coatings, based on PC, can significantly alter surface sensitive properties of polymers, including hardness and scratch/wear resistance. In this work the nanomechanical and nanoscratching performance of two commercially available antiscratch coatings are compared, as protective overcoats of organic lenses. Their nanoscratch behavior is investigated using a NanoIndenter XP system with a lateral force measuring attachment. Low load scratch tests were used to evaluate the scratch resistance and the friction coefficient (μ) of the antiscratch coatings. The scratch process revealed a fully elastic recovery/deformation of the coatings. Testing under a normal load of 6 mN resulted in slight grooving at the layer surface; however, in-situ profiling of the scratch trace showed no evidence of failure. The values of μ were found in the range of 0.1–0.3. The nanoscratch results are compared with abrasion tests that are typically used in the industry.