The demand for ultraviolet (UV)-crosslinkable pressure-sensitive adhesives (PSAs) has rapidly been increasing. A variety of different PSAs containing new photoreactive pyridinium derivatives have been evaluated for their effectiveness in improving adhesion and cohesion in UV-crosslinkable PSAs. PSAs have been evaluated with respect to the tack, peel adhesion, and shear strength. This article summarizes the breakthrough technology used to achieve better performances in UV-crosslinkable acrylic PSAs. (C) 2007 Wiley Periodicals, Inc.