The Study on the Photopolymerization Reaction of UV-LED Inkjet Ink

The study on the photopolymerization reaction of UV-LED inkjet ink is very significant in order to improve the curing speed. The effects of the type and content of photoinitiator, the content of pigment and the intensity of light source on the curing speed of yellow UV-LED inkjet ink were studied by the combinative test method between touch method and real-time infrared spectroscopy. Meanwhile, the optimal proportion of photoinitiator was determined by formula experiment, and then, the content of pigment was obtained by combining the color density of ink. The results showed the absorptivity of photoinitiator to the light source of UV-LED and the quantum yield of active species impact seriously the curing speed of ink. The effect of the content of photoinitiator on the reaction speed of photopolymerization exhibited the tendency is fast increase firstly, and then, stabilization, slight decrease finally. The reaction speed of photopolymerization improved with the increase of the intensity of light source. The curing speed of ink decreased with the increase of the content of pigment, and the optimal content was 2–3% under guaranteeing the appropriate color density. The curing speed of yellow UV-LED inkjet ink was the best of all by using photoinitiators ITX, 910 and 819 (the mass ratio is 38:34:29).