Treatment of Heat Sensitive Surfaces
For energy-saving processing of heat-sensitive plastic surfaces, Easytec GmbH, Aachen, Germany, offers UV-LED emitters with optical irradiation intensities ranging from 2 W/cm2 to 16 W/cm2. The emitters generate energy savings of 75 % compared with conventional gas discharge lamps. Further savings accrue from the handling technology: working widths can be adjusted via a control element and unneeded segments can be switched off. Furthermore, the speed with which the UV-LED emitters can be switched ON/OFF – in just a few milliseconds – means that energy and electricity costs can be saved by switching them off at each gap between workpieces. For greater application versatility, the emitters come in various designs. All kinds of irradiation windows are possible in any given housing, so that entire surfaces can be covered without intersecting or overlapping spots. What is more, shadows and over-exposures of the kind produced by strings of smaller UV-LED systems are avoided. The UV emitters can be operated with different wavelength peaks in the range 365 to 410 nm. Even on irregular parts, power output of 16 W/cm2 is possible. Special applications involving greater distances are possible, e.g. for 3-D parts, which can be processed at a power output of up to 24 W/cm2.
Until now, conventional final curing of UV coatings on heat-sensitive substrates such as plastic parts, films or paper required the use of conventional gas discharge lamps. UV-LEDs, however, emit so-called “cold radiation”. This consists of a monochromatic spectrum of pure UV wavelengths, and so there is no infrared radiation to generate heat. A further advantage is the long lifetime of LEDs of up to 50,000 hours. Emitter warm-up times, too, are eliminated, as the diodes can be switched on within a few milliseconds. Running costs can be further reduced by switching off the emitters where there are small gaps in the workflow.
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