Optimization of Multilayer Inorganic/Organic Thin Film Structure for Foldable Barrier Films

Abstract

We report the optimal structure of multilayer inorganic/organic thin film for foldable barrier films which maintain their barrier properties even after a folding test with 1 mm radius. The barrier film consists of PI film, cyclo-aliphatic epoxy-siloxane (CES) hybrid material, and ALD-grown Al2O3. The optimal structure was determined by investigating mechanical properties of the film based on finite element analysis (FEA). In this structure, folding stress and strain in the brittle Al2O3 layer is minimized with values of 5.38 MPa and 0.0048% during a folding test with 1 mm radius. The optimized multilayer inorganic/organic thin film proposed by FEA results was validated by water vapor transmission rate (WVTR) measurement. Despite 10000 times folding test, the WVTR value of the barrier was comparable to that of a non-bending sample. These results demonstrate a potential for applicability to an encapsulation technology for flexible organic light-emitting diodes (OLEDs).