Effects of monomer functionality on physical properties of 2-ethylhexyl acrylate based stretchable pressure sensitive adhesives

Abstract

Recently, the interest in flexible displays has been increasing due to the demand for wearable and flexible electronics which can be curved, bent and/or stretched without impinging their performance. Most importantly, the development of stretchable adhesives is indispensable in order to adhere the components of the stretchable display without defects or flaws at interfaces during operation. In this study, UV curable pressure sensitive adhesives (PSAs) composed of acrylic monomers were successfully characterized in terms of physical properties for the stretchable display application. With the base monomer of 2-ethylhexyl acrylate, various acrylic monomers exhibited different properties, especially instantaneous strain reversibility was achieved using methyl acrylate (MA) and 2-hydroxyethyl acrylate (HEA). Interestingly the MA incorporated PSA became more elastic as strain increased from 15% to 30%, reducing hysteresis loss close to zero. Acrylic acid (AA) containing PSA showed significantly higher peel adhesion compared to the other monomers. Rheological studies are also performed to support the aspect of the peel adhesion values which correspond to the trend of loss modulus (G”). Transmittance of each synthesized PSA was sufficiently clear (>95%) demonstrating the feasibility of synthesized UV curable PSAs for optically clear adhesives.