Design and Application of a Photo–Thermal Dual‐Curing Encapsulation Adhesive Based on a Modified IPDA /Epoxy Resin System

ABSTRACT In this study, an epoxy addition approach was used to modify isophorone diamine (IPDA). By adjusting the molar ratio of epoxy groups to IPDA, the effects of the modification level on the mechanical properties, gelation kinetics, strength, and optical transmittance of the thermosetting system were examined. The results show that the optical properties of the thermosetting system, including transmittance, haze, and yellowness index, improve as the modification level increases. While tensile strength slightly declines, impact strength and elongation at break increase significantly. Among the tested formulations, the ER2 thermal‐curing system, with a 22% modification level, demonstrated the best overall performance, extending the storage lifetime from 24 to 288 h. Its impact strength and elongation at break increased by 67.4% and 94.0%, respectively, compared to the unmodified system. Additionally, the ER2‐based photo–thermal dual‐curing system, combined with a light‐curable acrylic resin, achieved complete curing under a single light exposure without secondary heating. This system exhibited notably lower volume shrinkage and yellowness index than the single‐cure acrylic resin, offering an efficient and energy‐saving solution for high‐reliability optical encapsulation applications.