Optimization of Recovery and Relaxation of Acrylic Pressure-Sensitive Adhesives by Using UV Patterning for Flexible Displays

For flexible displays, recovery and relaxation of acrylic pressure-sensitive adhesives (PSA) must be enhanced; however, only a few studies have focused on their optimization. High cross-linking density of the PSA leads to improved recovery but deteriorates the stress relaxation; thus, it is difficult to perform optimization by simply controlling the cross-linking density. Herein, it was determined that a UV-patterned PSA with both high and low cross-linking densities in a single layer enables the optimization of both recovery and relaxation. By introducing the UV-patterned PSA, the elasticity and recovery largely deteriorated but the stress relaxation was significantly improved, compared to that of the nonpatterned PSA, and this effect was enhanced with increases in the applied strain. Thereby, the recovery and relaxation were well-optimized with both values above 71% only at 300% strain. The recovery and relaxation of PSA had, respectively, a positive and negative correlation with the storage modulus.