Stacy Hoge, Marketing Communications Manager, Phoseon Technology, Hillsboro, OR
Introduction
LED curing solutions are utilized in the
coatings industry because they offer
highly reliable UV curing due to being
a solid-state device. They provide deep
through-cure and allow low surface
temperatures that enable less expensive
raw inputs.
UV curing technology with light-
emitting diodes (LEDs) is considerably
more eco-friendly and resource-saving
compared to the traditional technolo-
gies. The disposal of heavy metal lamps
made of gallium and mercury is no lon-
ger required. Working conditions for
the line operators are improved as there
is no ozone formation and an exhaust
system is thus not necessary, which
could lead to higher noise levels. The
lower energy consumption of LED light
sources contributes to the protection of
resources. Figure 1 illustrates the LED
curing process.
Characteristics of UV LED
Light Sources
Traditional UV lamps produce UV energy by generating an electric arc inside
an ionized gas (typically mercury) chamber to excite atoms, which then decay,
emitting photons. The photons emitted
cover a broad range of the electromagnetic spectrum including some infrared
and even visible light. Only about 20% is
typically useful for UV curing.
A UV LED generates UV energy in
an entirely different way. As an elec-
tric current (electrons) moves through a
semiconductor device called a diode, it
emits energy in the form of photons. The
specific materials in the diode determine
the photon wavelengths and, in the case
of UV LEDs, the output is typically in
a very narrow band +/- 10 nm. Figure 2
compares the output of a 395 nm LED
light source with a typical traditional UV
lamp. It is important to note the differ-
ence in intensity and wavelength of the
output; both are key to understanding a
UV curing process.
Formulating Chemistries
For efficient and effective UV curing of
a coating, the formulator seeks to overlap the UV light source output with the
spectral absorption of the photoinitiator
(PI). The amount of PI in a typical UV
LED Curing Technology
for Coatings
Figure 1: LED curing process.
