A double-layered optically clear adhesive with enhanced resistance to waviness and impact, designed for use in high-end mobile display

Abstract

In high-tech display industries, excellent impact resistance and surface waviness implementation technologies have gained much attention as the products are being lightweight and thinned. In particular, as a black pixel defining layer is adopted instead of a polarizer used to prevent external light reflection, impact resistance performance and surface quality characteristics are problematic. Herein, we proposed the double-layered optically clear adhesive (OCA) structure consisting of urethane-acrylate type OCA and UV-curable acrylic OCA for simultaneously achieving impact resistance and surface quality performances. Urethane simultaneously contains the soft segment and the hard segment based on hydrogen bonding between urethane functional groups, indicating high shock absorption performance. In addition, due to this unique structure, it exhibited a high modulus in the compression direction, thereby realizing excellent surface waviness. The UV-curable acrylate OCA can implement basic properties of adhesives such as tacky, adhesion, and inkstep cover capability, while at the same time securing indentation resistance with high modulus after UV curing. Optimization of impact resistance performance and surface waviness according to the thickness and laminating order of the proposed double-layered OCA was performed, and as a result, the double-layered OCA in panel/urethane-acrylate type OCA 100 μm/UV-curable acrylic OCA 25 μm/window structure showed the improved surface quality of 0.22 Kc value improved by 56.8 % and impact resistance of 5.1 cm improved by 100 % compared to the conventional OCA.