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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, called 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 becomes solid.

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 types.

For further information on the curing process Please take a look at Cibas site.

http://www.cibasc.com/pf/docMDMS.asp?targetlibrary=CHBS_CE_MADS&docnumber=1628 

                                             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 an advantage.

 

For further information: Contact         For further information on lamp types: Alpha Cure 



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