UV Glossary
9-7
Part 1061253B
E 2006 Nordson Corporation
photoinitiator A molecule which when exposed to a specific wavelength of energy
forms a reaction that begins the cure process.
photopolymerization Turning a liquid (wet) into a solid (dry) through exposure to UV light.
planar shutter A shutter assembly that is attached to the outside of a lamp head.
The louvered shutter moves perpendicular to the emitted UV light.
polymer A macromolecule consisting of a large number of monomer units.
positive cooling When the cooling air for the lamp head is blown through the lamp
head and onto the substrate being cured. Positive cooling can be
supplied through either an integral or remote cooling fan. With
positive cooling, an additional exhaust system is required to remove
heat and ozone.
post cure The continuation of chemical reactions in the ink or coating after
exposure to UV has ceased.
power density Refer to irradiance.
quartz plate Plates that allow UV energy to penetrate with minimal loss in intensity
and are mounted in front of the lamp head. The plates are used to
prevent positive cooling air and airborne contaminants from contacting
the substrate, negative cooling air from contaminating the bulb and
reflectors, or to remove some of the infrared that is radiated from the
UV bulb. If the goal is to reduce the amount of heat contacting the
substrate, additional cooling air must be blown across the quartz. If
additional air is not used, the quartz will eventually heat up and begin
radiating heat onto the substrate. To further reduce heat, the quartz
can be coated with a material that passes UV light and absorbs
infrared energy.
quartz tube (1) A sealed tube made from a silicate material that is filled with a
precise mixture of mercury and various inert gases and sometimes
fitted with electrical connections. The vapor emits light when it is
energized through the use of either a voltage arc or microwave energy.
Often used to refer to the bulb.
(2) An open tube made from a silicate material through which a
substrate can pass. The tube is often placed in front of a UV lamp
head and flooded internally with Nitrogen. Parts traveling through the
tube are then safeguarded from exposure to the oxygen and ozone in
the lamp head cooling air.
