Residue-free and nondestructive separation of transparent adhesive thin films using the interfacial coating of thermo-responsive nanocapsules

Abstract

The effective separation of flexible optoelectronic panels bonded with transparent adhesive films is an innovative technology that enables the reuse of expensive devices, reducing manufacturing costs in multilayered flexible displays. Herein, we present an effective, facile strategy for heat-triggered detachment of adhesive thin films with high optical transparency by interfacial coating with thermo-responsive nanocapsules. These temperature-sensitive nanocapsules, comprising reactive benzenesulfonyl hydrazide cores and polyacrylonitrile-poly(methyl methacrylate) copolymer shells, were simply prepared through a one-pot synthesis using surfactant-free emulsion polymerization. The synthesized nanocapsules were mixed with UV-curable resins and applied as a thin interfacial layer on the substrate through blade coating and UV curing, producing a transparent, uniform nanocapsule layer of 10 μm with extensive coverage. A transparent double-layered adhesive film was achieved by stacking optically clear adhesive film on the interfacial nanocapsule layer. Compared with pure transparent adhesive film, this double-layered adhesive film containing interfacial nanocapsule layer yields a remarkable optical transparency of 99.1 % and high initial adhesion strength of 98.2 %. Furthermore, a short-time heat treatment at 100 °C produces numerous gas microbubbles in the interfacial region between the substrate and optical thin film, facilitating their clean and spontaneous detachment with an outstanding desorption efficiency of 78.7 %. Our separation approach will be helpful for providing a promising way to dismantle polymer thin films without surface damage in wide industries from semiconductor packaging to flexible devices.