UV-crosslinkable acrylic pressure sensitive adhesives (PSAs) were synthesized by copolymerization of 2-ethylhexyl acrylate (2-EHA), vinyl acetate (VAc), acrylic acid (AA), 2-hydroxyethyl methacrylate (2-HEMA) and 4-acryloyloxydiethoxy-4'-chlorobenzophenone (unsaturated photoinitiator), with varying contents of 2-HEMA and photoinitiator, by solution polymerization. The UV-crosslinking behavior of the PSAs was studied by ATR-FT-IR spectroscopy, and PSA performance was characterized by probe tack, peel resistance and shear adhesion failure temperature (SAFT). As 2-HEMA acts as a good hydrogen donor to benzophenone, the efficiency of the photoreaction was enhanced; thus with increasing contents of 2-HEMA and photoinitiator in the PSAS the incorporation of benzophenone groups in the PSAs, even at low UV doses, was quite fast. In addition, as the crosslinking reaction proceeds via photo-reaction mainly between 2-HEMA and photoinitiator, the probe tack and peel resistance of the PSAs having high concentrations of 2-HEMA and photoinitiator rapidly decreased in the early stage of UV irradiation due to increased crosslink density. These phenomena were also observed in the SAFT test, with the PSAs containing high levels of 2-HEMA and photoinitiator showing high SAFT values at low UV doses.