Product manual

UV Glossary
9-5
Part 1105120-01
E 2013 Nordson Corporation
oxygen inhibition Oxygen slows the cure response of UV curable coatings. The higher
the ratio of exposed surface area to coating mass, the greater the
impact oxygen has on the coating.
ozone (O
3
) An unstable, colorless gas with a penetrating odor that is generated by
the reaction of short-wave UV light (184 nanometers) with air.
ozone-inhibiting
(ozone-free) bulbs
Bulbs where the quartz is manufactured with an additive that prevents
the transmission of UV beneath 200 nm in wavelength. It is the
reaction of short-wave UV light (184 nanometers) with air that
produces ozone.
Parts Per Million (PPM) The units of the Threshold Limit Value (TLV) when referring to the
maximum level of a substance that a person should inhale over an
8-hour shift during a 40-hour week without producing an ill effect. Also
refer to Threshold Limit Value.
peak irradiance (peak
power density)
The maximum irradiance measured over a sample period, measured
in joules/cm
2
/sec or watts/cm
2
.
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 lamphead. 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 lamphead is blown through the lamphead
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 lamphead. 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.