Preparation of UV-curable PSAs by grafting isocyanate-terminated photoreactive monomers and the effect of the functionality of grafted monomers on the debonding properties on Si wafers

Abstract

Photoreactive pressure-sensitive adhesives (PSAs) were prepared by grafting mono- or difunctional photoreactive monomers onto acrylic PSA, and their adhesion properties were evaluated before and after ultraviolet (UV) curing for application as dicing tape. In this study, the NCO-terminated difunctional photoreactive monomer (NDPM) was newly synthesized and compared with 2-acryloxyloxyethyl isocyanate (AOI), a monofunctional monomer. The 180° peel strengths of pristine and photoreactive PSAs were similar before UV curing (1850–2030 gf/25 mm). After UV curing, the 180° peel strengths of the photoreactive PSAs decreased significantly and converged to nearly zero. When a UV dose of 200 mJ cm⁻² was used, the 180° peel strength of 40% NDPM-grafted PSA decreased to 8.40 gf/25 mm, which was much lower than that of 40% AOI-grafted PSA (39.26 gf/25 mm). NDPM-grafted PSA also showed that its storage modulus shifted more to the upper right side of Chang's viscoelastic window than AOI-grafted PSA, and this is because NDPM provided a higher degree of crosslinking than AOI. Furthermore, SEM-EDS analysis showed that UV-cured NDPM-grafted PSA retained almost no residue on the silicon wafer after debonding.