Transparent composite coatings with adapted mechanical stress prepared by ion beam sputtering

Oxide materials are often employed for protective and optical coatings, because of their high transparency and their mechanical and chemical stability. However, thin and flexible PMMA foils as carrier substrates with different functions need adapted coating materials with properties beyond the quality of oxide coatings. Especially, high coating stress leads to deformation of the polymer foils and to coating failure due to flaking, folding and cracking. Contrary, organic layers reveal high flexibility and low stress, but the mechanical stability has to be improved. Therefore, a coating material which combines the stability of oxides with the flexibility of the polymers is needed. Ion beam sputtering (IBS) is known as a well suited coating process for the deposition of high quality oxide coatings on temperature sensitive substrates like polymers. Also, IBS can be applied for the production of nearly stress free organic layers for example sputtered from a PTFE target. This study is dedicated to the optical and mechanical properties of composite materials, consisting of sputtered PTFE and oxides for coating of polymer foils.