Photoinitators & Doped Lamps
Different photoinitiators such as inks, adhesives and varnishes respond to different wavelengths (nm) of UV light in order to cure.
Metal Halide (doped) lamps are effectively mercury lamps but with additional additives. These additives modify the spectral output and enhance certain wavelengths nanometres (nm).
Most curing photoinitiators are activated using near UV (200-400nm range)
- UV-A (315-370 nm): curing bulk substrate (e.g. print press, labels and packaging)
- UV-A (370-400 nm): curing heavier inks/substrates (e.g. silk screen, Japanese)
- UV-V (400-450 nm): deep penetration for thick layers like varnishes (e.g. furniture)
- UV-B & UV-C: (100-315) used in conjugation with UV-A to cure the very surface of substrate
Spectral Output = UV Radiant Output Vs. Wavelength
Mercury Vapour Lamp: 254nm – 365nm
- Typical ink, polymer and resin manufacturers in Europe and the Americas are designed to cure around 365 nm wavelengths
Iron Iodide Lamp – enhances UV output at 380nm
- Typical inks, polymers and resins with photoinitiators in Japan are designed to cure at 380 nm wavelengths
Gallium Lamps – enhances UV output at 415nm
- A longer UVA wavelengths – cures thicker surfaces such as varnishes on furniture.