The technology, with which inks, varnishes, silicones and adhesive are cured using UV light, has plenty to offer the printing and coating industry. Since the start of this millennium, LEDs have been used in addition to arc lamps for UV curing.
The light-emitting diodes are based on semiconductor connections, which convert current directly into light. If electricity flows through an LED in the forward direction, it emits energy in the form of visible light, infrared or even ultraviolet radiation. LED UV systems work in the UVA/UVV range between 365 and 405 nm. Experience has shown that an LED performs best in a wavelength range of 385 nm when used for UV curing.
UV LEDs are used anywhere their specific advantages are required. LED UV units can be used as soon as they are switched on. They release very little heat on to the substrate, which means they can be positioned very close to the substrate surface, i.e. at a distance of 10 to 20 mm. The compact systems are cascadable and have a particularly long service life. The LEDs on an array (field) can also be individually controlled, according to where light is required on the substrate.
The efficiency of an LED chip is known as External Quantum Efficiency (EQE). This describes the ability of the LED to convert electrons into photons. EQE does not set the standard for the daily efficiency of an LED, however. The output requirements and optical applications also need to be taken into consideration.
LED UV systems are used in both the printing industry and a number of other industries where coatings play a role. LED-UV technology currently makes up the greatest proportion of adhesive curing and inkjet printing. In the coming years, a significant increase in the market share of LED UV systems is expected.