The use of UV light as a curing technology has been around for a long time. In the last few years it has become more popular since the technology on the lamps and the materials side has greatly improved. Applications are now on sheetfed, web and wide format inkjet equipment. The major advantages of UV inks are:
1) Press sheets are dry when they come off the press
2) Higher throughput speed than Infra-Red drying
3) No Volatile Organic Compounds released in the air
4) Resist smudging and abrasion
5) UV Coatings have a “wet look”
6) Do not have solvents to penetrate uncoated stocks
Most printers buy UV power supply systems that may be supplied by the manufacturer of the equipment but made by someone else. Understanding how UV lamps work can improve their performance and save you money.
There are series power supply for different applications. Low-pressure UV lamps may be used for disinfecting purposes, curing nails and dental fillings, or water purification. The type of lamp used in printing applications is usually a medium pressure, linear (straight tubes), mercury vapor arc lamp. Medium pressure UV lamps cure inks and coatings instantly. It is a photochemical, not a heat process. It allows the equipment to run at very high speeds for extended periods.
General use light bulbs have a filament. The electricity causes the filament to glow, producing light. Medium pressure UV lamps do not have a filament. They utilize a high voltage charge to ionize a mercury/gas mixture in the lamp creating a plasma that emits UV light. This system requires a high voltage/amperage power supply (typically a magnetic ballast transformer with a high voltage capacitor bank). The ballast is wired in series with the lamp and performs two functions. Initially, the ballast provides a high voltage charge to ‘strike’ or ‘ionize’ the mercury. Then, once the mercury is ionized, the ballast reduces the voltage and amperage required to keep the mercury ionized and emit a stable stream of UV light.