Epoxy acrylate is the most widely used oligomer class in UV curing, made by reacting acrylic acid with a bisphenol-A epoxy resin. The aromatic backbone and high crosslink density produce exactly what most UV coatings want: hardness, high gloss, chemical and solvent resistance, and fast cure — at the lowest cost per performance of any oligomer class.
The trade-offs follow from the same chemistry. High crosslink density means limited elongation, so epoxy acrylate alone is a poor choice where the coated substrate has to flex. The aromatic backbone yellows under prolonged light exposure, which rules it out of critical clear coats and whites. And it is inherently very viscous, normally requiring reactive diluents or warm application.
In practice, formulators blend epoxy acrylate with a urethane acrylate to buy back flexibility and adhesion while keeping the hardness and cost advantage.