Frequently Asked Questions
UV means ultra violet and refers the a certain set of wavelengths in the Electromagnetic spectrum and in a curing application usually refers to 200 – 400 nano metres, 400 nano metres is the start of visible light part of the spectrum, the violet end of the rainbow and is just below the wavelengths that our eyes can see.
When people talk about UV they are usually referring to the light used to cure substances, such as inks varnishes and adhesives to name a few and this light until fairly recently has been generated by using a lamp, usually a Medium Pressure Mercury Arc Lamp (MPA) to give it it’s technical term, this emits light in a fairly broad electromagnetic band with about 70% in the Infra-Red wavelengths, about 15% in the visible wavelengths and the remainder in the UV wavelengths with peaks usually around 254nm, 308nm, 320nm and 365nm. Usually these lamps have a limited useful life, typically around 1000 hours, the lamp itself gets very hot as it has to evaporate the mercury in order to emit light in the correct wavelengths and is therefore quite inefficient typically only converting about 15% of the input electrical energy to UV output.
UV LED is a different way of generating UV light using Light Emitting Diodes, these emit light in narrow wavelength bands usually at the upper end of the UV wavelengths, for instance 365nm and 395nm are the most common wavelengths. They are much more efficient at generating the light, typically up to 50% of the electrical energy is emitted as UV light, they only emit light in the specified wavelength and a narrow band either side (about 20 nm), but this can be a weakness as well as some chemistry needs a wide band of UV to cure properly. Heat is a by product of passing the electrical current through the diode, but this is not projected with the light, but is retained in the LED and the LED itself has to be cooled, by not projecting the light the substrate is subjected to much lower heat, making it suitable for heat sensitive application.
Want to know more? Read our White paper on Understanding UV