Fluorescent microscopy proving resin adhesion to a fluorinated mold surface suppressed by pentafluoropropane in step-and-repeat ultraviolet nanoimprinting

Resin adsorption on fluorinated silica mold surfaces during step-and-repeat ultraviolet nanoimprinting was studied by fluorescent microscopy using a fluorescent UV-curable resist. The fluorescence intensity indicating resin adsorption to the mold surfaces in step-and-repeat UV nanoimprinting under air atmosphere was significantly higher than that under condensable gas pentafluoropropane (PFP) atmosphere. The larger resin adsorption in air was attributable to sticking uncured resin around trapped air bubbles preventing the UV-curable resist from causing acrylate radical photopolymerization and to the small amount of resin components adhering to the mold surface. The entire adsorption of resin components, not only a fluorescent dye doped in a UV-curable resin, was confirmed by high-sensitivity UV-visible absorption spectroscopy and atomic force microscopy in a frictional mode. PFP suppressed obviously stuck uncured resin and entirely adhered resin components to the fluorinated mold surface. The entire adsorption of resin components was compared among three kinds of fluorinated mold surface treated with commercially available antisticking reagents, FAS13 (tridecafluoro-1,1,2,2-tetrahydro- octyltrimethoxysilane), OPTOOL DSX, and OPTOOL AES4-E. It was proved by the fluorescent microscopy that the fluorinated mold surface prepared by chemical vapor surface modification with FAS13 showed the best antisticking property among the fluorinated mold surfaces, because the entire adsorption of resin components was hardly affected by the number of cycles of step-and-repeat UV nanoimprinting and by the positions in the mold surface.