The major attributes of pulsed UV technology: deep penetration,
thermal management, energy efficiency, and fast curing are all indicators
of pulsed UV’s ability to handle difficult curing applications.
To understand how pulsed UV achieves its unique curing results, we
need to understand more about UV.
UV can be delivered either continuously or in pulses. If we consider
how the energy is delivered by these two means, we quickly understand
significant differences. For example, consider two ways of expending
1200 Joules of energy: one can either power a 10 watt continuous lamp
for 120 seconds, or power a 400,000 watt pulsed lamp for 3 milliseconds.
The difference in peak power is readily apparent. This is analogous
to penetrating a block of wood with a nail: one could press a nail
into the wood with a finger for 10 seconds without effect, or exert
the same amount of energy and drive the nail instantaneously into
the wood with a single strike of a hammer. Pulsed UV, like the hammer,
delivers light at high peak power to achieve deep penetration.
The high-peak-power UV pulses penetrate thick and/or semi-opaque
substrates much more effectively than, for example, UV light from
continuous mercury UV lamps.
Pulses can deliver the energy necessary to cure an adhesive or
coating in short, microsecond pulses. In addition to delivering
more energy in a shorter period of time, users can specify both
the pulse duration and frequency, which allows for appropriate cooling
zones between the pulses to be designed into the process. This essentially
eliminates the possibility of substrate changes from exposure to
unwanted thermal energy.
Pulsed UV lamps are ideal for start-stop-start operations because
they can turn on and off instantly. This results in significant
savings in energy, lamp maintenance, and safety on high-volume manufacturing
lines. The lamp is only on during the cure cycle. It is safer for
the operators if the lamp is completely off when not curing. As
an additional safety benefit, the pulsed UV source does not include
any hazardous materials, such as mercury.
Pulsed UV curing achieves higher overall system energy efficiency.
The high peak pulses and the instant on/off capability greatly reduce
the average mains power requirements. In one manufacturing line,
the average power requirement was reduced from 6,000 Watts (using
mercury vapor lamps) to less than 1,000 Watts when they converted
to pulsed UV systems.
Lamp Spectra
At Xenon, we offer application-specific lamp types. The Xenon lamp
inherently produces a broadband spectrum suitable for chemistries
that absorb UV light from 180 nm to 800 nm. Our lamps are available
with up to four different spectral cut-offs, producing wavelength
properties suitable for specific types of curing challenges.
Effective Spectral Cut-off Point:
Type A: 370 nm: best for visible light cures.
Type B: 240 nm: offers optimum UV performance.
Type C: 190 nm: cuts off deeper UV.
Type D: 160 nm: allows deep UV.
Shown below is a typical spectrum for a type C lamp.
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