Absorption wavelength, molar extinction coefficient, and photoreactivity have obvious effects on photoinitiation performance. Photoinitiator directly affects the curing speed, yellowing, and cost. After the photoinitiator molecule absorbs light, it mainly generates active species in the excited triplet state through related chemical action and initiates the polymerization of the system, thereby forming a cross-linked network structure.
LEDs emit a very narrow range wavelength in the range of UV-B and UV-A. Some of them are 285nm, 300nm, 310nm, 365nm, 385nm, 395nm, and 405nm. And UV-B, which contains wavelengths 285nm, 300nm, and 310nm, is still uncommon due to weak illuminance.
UV LED lamps, especially short-wave UV-LEDs, have weak illuminance, which reduces the sensitivity of the photoinitiator to it and affects the quantum efficiency of the photoinitiator’s luminescent chemical reaction.
At present, the wavelengths of UV-LED lamps mainly include 365nm, 385nm, 395nm, and 405nm. However, wavelengths more than 370nm, absorb weakly. Traditional photoinitiators can’t absorb where LED emits. The precise wavelength range of UV LED lamps means that it’s important to find the wavelength that the material’s polymerization initiator is the most sensitive to.