Guide to UV Measurement
UV Exposure: Irradiance, Spectral Distribution, Time, and Temperature
There are four key factors of UV exposure that affect the curing and the consequent performance of the UV curable material. Simply stated, these are the minimum exposure parameters that are required to sufficiently define the process:
irradiance – either peak or profile of radiant power arriving at a surface, measured in W/cm² or mW/cm²;
-
spectral distribution – relative radiant power versus wavelength, in nanometers (nm);
-
time (or speed) – time of exposure – energy is the time-integral of irradiance measured in J/cm² or mJ/cm², and
-
infrared (IR) or heat – usually observed by the temperature rise of the substrate, °F or degrees C.
Energy is not included in key factors of UV exposure because it is a secondary measure – it is a combination of two other variables, irradiance and time. Why measure Energy? Energy can be a useful measure in process control.
Note also that “dose” is a term that applies to Electron Beam and other ionizing radiation – not to UV.