Page "Inkjet printing" Paragraph 19

; UV-curable inks: these inks consist mainly of acrylic monomers with an initiator package.

After printing, the ink is cured by exposure to strong UV-light.

Ink is exposed to UV radiation where a chemical reaction takes place where the photo-initiators cause the ink components to cross-link into a solid.

Typically a shuttered mercury-vapor lamp is on either side of the print head, and produces a great amount of heat to complete the curing process ( this lamp is used for free radical UV ink, which is what the majority of flatbed inkjet systems use ).

UV inks do not evaporate, but rather cure or set as a result from this chemical reaction.

No material is evaporated or removed, which means about 100 % of the delivered volume is used to provide coloration.

This reaction happens very quickly, which leads to instant drying that results in a completely cured graphic in a matter of seconds.

This also allows for a very fast print process.

As a result of this instant chemical reaction no solvents penetrate the substrate once it comes off the printer, which allows for high quality prints .< REF name =" Auto5I-4 "/>< REF name =" Auto5I-5 "/> The advantage of UV-curable inks is that they " dry " as soon as they are cured, they can be applied to a wide range of uncoated substrates, and they produce a very robust image.

Disadvantages are that they are expensive, require expensive curing modules in the printer, and the cured ink has a significant volume and so gives a slight relief on the surface.

Though improvements are being made in the technology, UV-curable inks, because of their volume, are somewhat susceptible to cracking if applied to a flexible substrate.

As such, they are often used in large " flatbed " printers, which print directly to rigid substrates such as plastic, wood or aluminium where flexibility is not a concern.