Solutions of an acrylic copolymer pressure sensitive adhesive with different concentrations of propylene glycol (PG) and oleic acid (OA) were cast on a PET film. A rolling ball tack test was carried out on the adhesive coated tapes with different thicknesses. The results were explained on the basis of the surface (energy and roughness) and viscoelastic properties of the copolymer, which were related to the glass-transition temperature. The 60-mu m PG samples with an approximately equal glass-transition temperature and surface energy did not have a significantly different tack value. The tack value of the 30-mu m tapes decreased with PG concentrations above 15% (w/w), which was related to an increase in the surface roughness with a more prominent effect at the lower thickness. OA, which improved both the surface and viscoelastic properties, increased the tack value up to 15% (w/w). However, the tack value decreased above 15% (w/w). This was explained on the basis of OA large crystals, which can decrease viscoelastic energy dissipations and form a mechanically weak surface layer. (c) 2005 Wiley Periodicals, Inc.