A Semi-Interpenetrating Double-Network Organic Gel Acrylic Optical Pressure Sensitive Adhesive Designed for Flexible Display

Abstract

In recent years, significant advancements in electronic technology have sparked a robust consumer interest in diverse flexible electronic devices. In order to cater to the demand for displays that can be bent, folded, or stretched, it has become imperative for all electronic components to possess flexibility. Consequently, novel adhesive prerequisites have emerged pertaining to the bonding of flexible display devices. However, conventional optical pressure-sensitive adhesives are susceptible to permanent creep due to their low crosslinking density after undergoing intense folding. Moreover, increasing the crosslinking density of these adhesives significantly compromises their adhesive performance. In this study, the organic gel system was introduced into the optical pressure-sensitive adhesive for the first time, resulting in the preparation of a semi-interpenetrating double-network organic gel structure. The crosslinked first network serves as a robust framework to prevent irreversible deformation of the optical pressure-sensitive adhesive. The incorporation of an uncrosslinked second network effectively enhances the wetting properties of the optical pressure-sensitive adhesive. The synthesized polar small molecules incorporate highly polar urea groups and exhibit a high degree of free mobility, facilitating the formation of extensive and reversible hydrogen bond networks. Analogous to water molecules, these compounds possess a substantial number of hydrogen bonds that are readily broken and rapidly reformed. These highly dynamic hydrogen bonds are crucial for the material's folding process, as they effectively convert mechanical stress into thermal energy, thereby significantly enhancing the material's folding resistance. The optical adhesive developed in this study exhibits superior overall performance, characterized by a peel strength of 14.5 N/25 mm, a 50% strain recovery time of less than 1 second, a stress relaxation rate exceeding 60%, a light transmittance greater than 92%, and a folding endurance surpassing 200,000 cycles.

Keywords: semi-interpenetrating double-network, organic gel, optical adhesive, flexible display