Hybrid UV LED Device for Simulating Spectrum of High-Pressure Mercury Lamp: Evaluation in UV Curing Process

Abstract

A hybrid ultra-violet light emitting diode (UV LED) comprising short and long wavelength UV LEDs (310, 340, and 365 nm) was developed and compared with the high-pressure mercury lamp for UV curing of a mixture of diurethane dimethacrylate, 1-hydroxy- cyclohexyl phenyl ketone, and diphenyl (2,4,6-trimethylbezoyl) phosphine oxide. The curing ability of the hybrid UV LED combinations was evaluated by comparing the thickness of the un-polymerized layer, calculated from the mass before and after rinsing the UV-cured film under air. The results indicated that among the combinations of UV LEDs, the combination of 365 nm and 310 nm UV LEDs provided the thinnest un-polymerized layer. This result was comparable to that obtained with the high-pressure mercury lamp. Nevertheless, the thickness of the un-polymerized layer achieved with the high-pressure mercury lamp was less than that with any of the UV LED combinations. The data show that the 405 nm line of the high-pressure mercury lamp functions to photopolymerize the monomer and is indispensable for the UV curing process.