Advancements in shorter wavelength LED technology and its impact on UV curing applications.
Advances in UV LED technology over the past half-decade have facilitated the replacement of Hg-based UV lamps by UVA LED lamps in some curing applications. The semiconductor nature of LEDs affords them numerous benefits over conventional UV-curing technologies, such as instant on/off capability, distinct wavelength selection, minimal heat transfer to the substrate, and lack of mercury and ozone, among more. However, the low wall plug efficiency of LEDs at non-UVA wavelengths had rendered them impractical for many curing applications. Over the past three years, improvements in material and semiconductor design has improved output power for commercially available UVB and UVC LEDs while the price per milliwatt has fallen by 90%. Many applications that fail with UVA LEDs alone may potentially succeed with exposures combining UVC, UVB and UVA LEDs, bringing the full benefit of LEDs to those markets. This paper will examine the effect of combined UVC/UVB/UVA exposures, varying irradiance, wavelength, and energy, on such formulations to determine the most effective combination on a wide range of traditionally ‘broadband’ chemistries.