Energy curing, more specifically, ultraviolet curing has been around since 1960s. However, UV-LED technology is slowly replacing conventional UV curing.
The conventional process is used in various industries, offering several benefits over traditional ‘air’ drying techniques. These processes boost production speed; allow higher print quality, reduced rejection rates and glossy finishes.
UV-LEDs are expected to offer even better processes for a wide range of applications. The technology will utilize photoinitiators, just like the conventional UV systems. However, most companies are not open to invest in UV-LEDs yet.
The reason for this is that many believe there are only limited photoinitiators for use with LED. This is not true; in fact it is actually the opposite.
Photoinitiators in UV/UV-LED curing
Energy curing ink, unlike the conventional air-drying one, has small molecules which make it impossible to create a ‘non-tacky film’. Hence, it requires further processing, applying energy to transform these materials into polymeric networks.
Addition of photoinitiators helps allow the inks to dry. These are chemicals that break down rapidly after reacting with UV light and form highly reactive species. These reactive substances then attack acrylate compounds in inks, resulting in a chain of reactions that leads to polymerization and drying.
Why UV-LED is taking over?
Traditionally, mercury lamps are used for curing which produce an array of ultraviolet emissions. This allows for easier selection of photoinitiators according to the requirements of an application.
The two disadvantages, however, of UV systems is the regulation restricting the use of heavy metal in electrical and electronic equipment, and increased heat generation of useless wavelength generated by the system. The latter requires additional energy and costs to keep the system cool.
UV-LED technology is being adopted for a number of applications, other than UV curing too. Hence, the technological development allows use of several heat sensitive substrates as well.
Photoinitiators for UV-LED
Peak LED lamp wavelength is 365/395 nm and most photoinitiators have primary absorbance below this wavelength. PCI Magazine reviews a few relevant studies and clearly identifies two key points.
First, UV/LED lamps are not monochromatic. Second, the absorption range of most photoinitiators is wide. Hence, a number of photoinitiators can sufficiently absorb in the 365 and 395 nm range, albeit not displaying the maximum absorption. Finding a good match is thus not very difficult.
UV-LEDs are a superior choice owing to comparatively lower costs, higher efficiency and more environmentally-friendly technology.
To find the right photoinitiator for you
FCAD develops high quality photoinitiators for use in various research and development processes. Our representatives can direct you to find the right photoinitiator for your application, based on following details:
2. Formula (free radical or cationic system)
3. Light source
4. Energy type
5. Color requirement (Anti-yellowing or not)
6. Film thickness