IPN structured UV-induced peelable adhesive tape prepared by isocyanate terminated urethane oligomer crosslinked acrylic copolymer and photo-crosslinkable trifunctional acrylic monomer

In this paper, a linear isocyanate terminated urethane oligomer, polyethylene glycol modified isophorone diisocyanate oligomer (PEG-IPDI), was prepared by the reaction of polyethylene glycol and isophorone diisocyanate. It is mixed as a cross-linking agent with an acrylic copolymer composed of 2-ethylhexyl acrylate, butyl acrylate, methyl methacrylate, hydroxyethyl acrylate and acrylic acid to form a network pressure sensitive adhesive (PSA) through the reaction of isocyanate groups in PEG-IPDI with hydroxyl and carboxyl groups in acrylic copolymer chains. By blending this network PSA with a photo-initiator and a trifunctional acrylic monomer in a certain ratio, the UV-curable PSA was obtained. After uniformly coating it on the treated polyethylene terephthalate film, a UV-induced peelable PSA tape for a silicon wafer dicing process was prepared. The PSA network formed before UV irradiation was held together with another network produced by UV irradiation of the trifunctional acrylate monomer to give an interpenetrating network (IPN) structure. The results showed that this novel UV-curable PSA tape with IPN structure had strong peel strength before UV irradiation, and could meet the fixed requirements of silicon wafer cutting process. After UV curing, the peel strength was remarkably lowered due to the formation of IPN structure. Compared to those semi-IPN structured PSA tapes prepared with traditional multi-functional urethane acrylate oligomers, the adhesion performances of IPN structured UV peelable PSA tape prepared in this work were similar, but the remaining adhesive on the wafer after the release of the UV cured tape was greatly reduced.