UNDERSTANDING THE UV CURING PROCESS

UNDERSTANDING THE
UV CURING PROCESS

High intensity ultra violet light is required to cure or fix UV curable ink. Exposure to a UV light source causes the photo initiator in the ink to react with the acrylic polymer, hardening it and fixing it to the print media.

UV curable inks are formulated to cure under very specific lighting conditions. The ink formulation and characteristics differ from manufacturer to manufacturer and UV curable inks and UV light sources are not interchangeable.

There are two UV light source technologies to consider when purchasing a large format digital inkjet printer: traditional Mercury Vapour lamps and newer UV LED curing systems.

Mercury Vapour Lamps

Mercury vapour lamps are the most commonly used light source in UV curable print technology. High intensity ultraviolet light is created by passing electricity through vaporised mercury in a high-pressure tube. Mechanical shutters open and close to expose the lamps during printing. The high energy light source ensures that ink is fully cured.

Although the technology is well established, mercury vapour lamps are not considered eco-friendly. The lamps take time to warm up, they consume a lot of electricity and they generate heat, which can affect heat sensitive media. The lamps also lose efficiency over time and need to be replaced after 1,000 or so hours of use.

Mercury vapour systems generally costs less to buy than UV LED systems but have higher maintenance costs and consume more energy.

Advantages:

Lower initial cost of acquisition
Proven technology produces high quality results

Disadvantages:

Lamps need to warm up before use, reducing productivity
Lamps need to cool down before relighting, reducing productivity
Heat can cause sensitive media to warp, reducing the range of applications
Lamps degrade and need replacement, increasing maintenance costs
High energy consumption increases overheads
Lamps contain mercury and metal halides that are potentially harmful to the environment