Thermal stress in antireflective coatings on polymer substrates

Antireflective coatings on polymer substrates as required for ophthalmic lenses and transparent display windows have to fulfill challenging requirements concerning their environmental stability. The mismatch of thermal properties of polymers and inorganic coatings causes stresses that may reduce the durability and dimensional stability of coated polymers. This study shows that ex-situ measurements of stresses have to be executed on polymer substrates rather than on inorganic substrates to record the residual film stress. Additionally, a concept of an elastic multilayer is applied to calculate stress gradients inside of single films and antireflective coatings during and after the deposition process on polymer substrates. For the development of coated polymer optics of high-stability it is essential to take into account the stress gradients across the coatings, and to apply special coating designs and optimized coating deposition parameters.