(A) thin barrier adhesive fabricated via initiated chemical vapor deposition for laminated encapsulation

Abstract

A barrier adhesive for the laminated encapsulation system is fabricated via initiated chemical vapor deposition (iCVD) process. In the laminated encapsulation method, the adhesive is necessary to laminated the barrier film. Most of adhesive is consist of polymer, which has high permeability to water vapor and oxygen. To prevent penetration of the water vapor and oxygen through the adhesive layer, the thickness and the free-volume of the adhesive should be minimized. iCVD facilitates the free-radical polymerization with smooth polymer surface and precise thickness control even in low-thickness scale while maintaining the chemical property of the monomer. Via iCVD process, poly(glycidyl methacrylate-co-2-hydroxyethyl acrylate) [p(GMA-co-HEA)] is synthesized in sub-micrometer thickness scale. The adhesive property was originated from the epoxide in GMA. HEA has low glass transition temperature ($T_g$), so the copolymer of GMA and HEA can be softened. Optimization of the injected monomer flow rate is proceeded for adhesive property and low-temperature crosslinking. To enhance the crosslink of p(GMA-co-HEA), post annealing was proceeded. However, the thermal stress can damage the organic electronic devices, so the post-annealing was carried out in the mild condition as possible. Also, the thickness of the adhesive layer was minimized and the crosslink density was optimized to prevent the side-penetration of water vapor and oxygen. As the thin adhesive layer shows both adhesive and barrier properties, it can be applied to the laminated encapsulation system for organic device, to block the exposure to water vapor and oxygen effectively.