R & D
UV-Light and UV curing. UV-light is just light/electromagnetic
waves, with a wavelength
that cannot be seen by the human eye. In fact it is energy, like
any other wavelength you know of. Starting at longer wavelengths,
which you meet in heating, i.e. Infra Red area going down to
microwave oven, visible light and then UV-Light ending at radioactive
radiation. Each wavelength can be used for specific purposes.
But as always when trying to generate a certain wavelength you loose
energy. For example a standard light bulb only emits 10% of visible
light, the rest is heat / IR radiation.
Generating UV-Light with a Mercury lamp would also give you a
loss. However it is more efficient, giving some 30% of UV radiation
(see under Lamp). UV Light is defined to be in the range of 200 Nm
to 400 Nm, just under the visible light. In fact UV light goes under
200 NM but this cannot exist in free air, and even the low UV-C (near 200
Nm) will be absorbed by air (hitting the oxygen molecule) after just
a few cm, creating ozone. The useful UV is
again divided into three areas - UV-A 315-380Nm, UV-B 280-315 Nm and
UV-C 200-280 Nm. Normally UV is the "curing power", but on
some older colours and special applications, heat or higher
wavelength (moving up from UV-C>B>A) is required.
The interesting thing about UV Light in this context is the ability to
start a chemical process. The chemicals used in UV ink, lacquer or glue,
photo initiators, are
sensitive to UV-Light. The UV Light
starts a process transforming the liquid stuff into being solid.
This process, provided that enough energy is present, happens in a
split second where the single molecules forms long chains, and
||As seen the chains are formed when the
UV-light hits the photo initiators. The colour is instantly
"dryed", ready to print the next colour on the machine.
UV Curing is not as simple as described above. The Ink for example, consist of many different types of chemicals and of course
the colour pigments. Different colours are sensitive to different
wavelengths, within the UV-range; and depending on the pigments and
the amount of pigments, they can be easy or hard to cure.
But even the major ink-manufacturer claim that UV-light is all
that is needed to cure their Ink. This is a common mistake; as known
heat will speed up any chemical process. So even within UV curing
some colour-series will need heat to dry and will actually fail
without. This is one of the reasons for choosing different UV-lamp
For further information on the curing process Please take a look
||It is seen that the difference in UV output is
in the UV-C region. The energy from the UV-C region has moved
up in UV-B and UV-A, on the Iron doped lamp.
As the UV-C is difficult to handle; it's easy to loose energy in
reflection and in air, the choice of an Iron doped lamp can be
For further information:
further information on lamp types: Alpha