Biomass-derived optically clear adhesives for foldable displays.

Acrylic pressure sensitive adhesives (PSAs) are the most widely used and play a crucial role in ensuring the stable operation of foldable displays. With a focus on product sustainability, numerous studies have aimed to enhance eco-friendliness of acrylic PSAs. However, few studies specifically address the development of environmentally friendly acrylic PSAs for foldable devices. In this work, we synthesized new monomers by modifying citronellol, a terpenoid, for use as functional monomers and low glass transition temperature (Tg) monomers in acrylic optical clear adhesives (OCAs). We prepared OCAs using these monomers via an environmentally friendly visible-light-driven polymerization process due to its greater energy efficiency and reduced harm to humans, as opposed to the ultraviolet light that is normally used in conventional photopolymerization processes. Their properties were confirmed through rheological analysis. The resultant OCAs exhibit low Tg, appropriate storage modulus across a wide temperature range, reliable adhesion force to various substrates, and decent creep and recovery properties. These characteristics indicate their potential to enhance the eco-friendliness of foldable devices.