LED UV replaces the broad-spectrum mercury arc lamp with narrow-band LEDs, typically emitting at 365, 385 or 395 nm. The operational advantages are substantial: much lower energy consumption, no ozone generation, no warm-up time, instant switching, far longer lamp life and much less infrared heat — which matters for heat-sensitive substrates like thin films.
The formulation consequence is what catches people out. LED output is narrow-band and shifted toward longer wavelengths, while most conventional photoinitiators absorb strongly in the shorter UV-C and UV-B regions that mercury lamps provide and LEDs do not. A formulation that cures perfectly under a mercury lamp may not cure at all under LED.
Converting to LED means reformulating the photoinitiator package, usually toward acylphosphine oxide types, and often increasing amine synergist because the lower peak intensity makes oxygen inhibition worse.