UV LED cure is becoming more and more prevalent in several converting areas. UV-curable inkjet has used UV LED cure for pinning for many years. Generally a mercury lamp was used at the end of the press to fully cure the inkjet ink. Today, UV LED cure is being used for the entire inkjet ink converting operation. Flexo presses are being sold or retrofitted to fully use UV LED lamps. These presses include four-color process inks, plus white inks and clearcoats or overprint varnishes (OPVs). UV LED lamps are being installed on sheetfed offset presses, both in retrofits and OEM. For these types of offset presses, UV LED lamps have replaced HUV lamps as the UV curing system of choice. Other than for offset presses, these applications generally require low-viscosity formulations. All of these graphic arts applications require fast cure.
For food packaging applications, the converted product must meet, in addition to performance properties, the requirements for migration into food. The Specific Migration Limits (SMLs) of the appropriate regulation must be met. These SMLs tend to be in the parts per billion (ppb) levels.