Adhesion performance and recovery of acrylic pressure-sensitive adhesives thermally crosslinked with styrene–isoprene–styrene elastomer blends for flexible display applications

Abstract

Fixing layers in flexible displays requires acrylic pressure-sensitive adhesives (PSAs) that can withstand deformation and folding stress. In this study, the effects of a styrene–isoprene–styrene (SIS) elastomer on the adhesion performance and recovery of an acrylic PSA were investigated. In simple blends, the peel strength and probe tack of a PSA sheet decreased slightly as the SIS content increased owing to the elastomer’s soft nature. In contrast, the lap shear stress increased slightly owing to entanglement of the SIS polymer chains. In stress relaxation tests, the effect of SIS on PSA recovery was limited by weak bonding. Therefore, the use of thermal crosslinking to improve bonding within PSA/SIS blends was examined. Although increased crosslinking decreased the peel strength and probe tack, the adhesion properties were maintained and the lap shear stress and strain increased. Further, PSA recovery improved in stress relaxation tests, but a specific strain could not be endured above 1 phr crosslinking agent. Thus, crosslinking with an elastomer plays an active role in the adhesion performance and recovery of acrylic PSAs. However, as the PSA sheet becomes opaque in the presence of SIS, the display applications of this system are limited and further improvements are necessary.