We investigated the formulations of acrylates which were applicable to UV-C LED lamps. The mixtures of acrylate monomers and photoinitiators were placed on silicon wafer or sandwiched between a silicon plate and a CaF₂ plate to obtain sample films. The films were irradiated by UV-C LED lamps which emit 265, 285, and 300 nm-lights. The effect of initiators, irradiation wavelength, and atmosphere on the conversion of the acryl unit was investigated using FT-IR spectroscopy. We found that the photoinitiator O-benzoyl 2,3-butanedione monooxime was the most effective photoinitiator for 265-nm light. The effect of atmosphere in the system was clearly observed.