UV/LED PHOTOINITIATOR AND CURE STUDY

Traditional medium pressure mercury lamps produce a wide spectrum of radiation,

including significant emissions in the ultra violet region, specifically UVC, UVB, UVA and

UVV. This spectral breadth allows for the selection of photoinitiator(s) to optimize the

cure of acrylate-based inks, coatings, adhesives, sealants and composites according to

the type and intensity of the light source as well as accounting for species within the

formulation that block and/or absorb UV light (e.g. pigments and fillers).

Unfortunately, these traditional mercury lamps yield 70-75% radiation in non-useful

wavelengths, most notably high energy infrared light that produces significant heat. The

need to keep typical Hg lamps cool requires voluminous airflow, and, thus, additional

energy. Such high air flow eliminates the practicality of using inert gas to improve

surface cure. (Costly inert gas would be constantly exhausted along with cooling air.)

The science of producing a suitably high flux of intense UV photons with light emitting

diodes has made remarkable progress in the past ten years. There are now many

commercial applications for UV/LED technology, allowing for the wider use of heatsensitive

substrates and providing for more economical overall UV-cure by eliminating

huge air handling structure and cost. (When water cooling in high output [>4 W/cm]

systems is figured in, energy savings estimates are as high as 50% versus a typical Hg

lamp system.1,5) Ancillary benefits include a compact, quieter process with “instant

on/off” capability, fewer environmental concerns (i.e. no waste mercury or ozone) and

much longer-lasting UV light sources (20,000 hr. vs. 2000 hr.).