Applying Time Temperature Superposition to Large Strain Shear data in Foldable Applications

Optically Clear Adhesives (OCA’s) are commonly used in electronics applications and serve important mechanical functions in addition to meeting optical needs. As technology progresses, electronics have moved from large stationary devices to smaller more mobile devices with curved or even foldable displays. This move has significantly increased the mechanical performance requirements from OCA’s. One such need is the ability to decouple stresses seen from large strains in a folded device. Current rheology test methods are available to measure the stress response of OCA’s at large strains. However, as OCA’s are viscoelastic materials, their performance is rate and temperature dependent, necessitating multiple rates and temperatures be run to assess the OCA’s performance in conditions relevant to the application. In this work we explore the use of the Time Temperature Superposition principle, commonly used in linear small strain experiments, on foldable OCA’s at large non-linear strain conditions in order to predict shear decoupling performance at multiple rates and temperatures.