If developing a sustainable graphics-printing process is a goal for your business, consider how the latest generation of UV-curable screen inks can help. This discussion looks at the history of UV inks, recent ink-formulation developments, and ways you can increase productivity while helping to reduce carbon dioxide emissions.
Formulation of UV inks has improved over the last 30+ years. The biggest contributing factors have been the improvements in raw materials, printing machines, UV-curing units, and the print process. Today’s UV graphics inks provide faster curing, denser colors, multipurpose functionality, more stable printing, and lower ink deposit/higher ink coverage.
Faster curing has been continuously pushed with regard to printing more product in a shorter period of time with less waste and lower cure output on the UV cure units. The UV inks for graphics screen printing are considered high performance and cure at 80- 100 millijoules (mJ—a measure of UV dose) and 600+ milliwatts (mW—a measure of UV irradiance) for most colors. Older UV inks or specialty inks may require up to 150-180 mJ and 600 mW or more. An ink that requires more UV output to cure can bring the following disadvantages:
• requires a decrease in belt speed (may not be an option due to heat sensitivity of the substrate), resulting in slower printing
• requires an increase of the wattage, leading to more energy usage
• requires the use of two lamps instead of one lamp in an attempt to increase UV output
• may carry a higher potential of undercuring issues, resulting in potential waste of finished materials and reprinting of the job
See the sidebar “Energy Savings & CO2 Emissions Reduction with Faster Curing UV Screen Inks,” on page 36 for a comparison of the energy used for various UV-curing-station settings. The setting required is based on the level of output needed to properly cure the ink deposit. Using today’s faster curing UV inks on properly maintained UV curing stations, a cure level of 80-100 mJ and 600+ mW can often be achieved with a 200-watt setting.
Keep in mind that UV curing units can vary greatly from shop to shop and within a shop in terms of performance. The amount of irradiance and dose from each UV cure unit needs to be measured. The mJ and mW values mentioned are representative of measurements of the UVA bandwidth (320-390 nm) taken with a standard radiometer.
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