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FLEXO Magazine : August 2014
Efficacy Of UV & LED UV Curing 2013 Rossini Research Scholarship Winners Share Details of Study Natalee Consulo, Lena Haidar, Mark MacManus T he purpose of this study was to provide accurate detailed data related to the print- ability differences between conventional UV flexographic printing and LED UV flexographic printing. Ultraviolet curing for printing purposes, also known as UV curing, is a photochemical process where high intensity ultraviolet light is used to instantly dry the coating, ink or adhesive printed on the substrate. There are many advantages of UV curing over traditional drying methods: • Greater consistency • Increasing production speed • Facilitating superior ink to substrate bonding and resistance to abrasion Currently there are three inking systems—water, solvent and energy curable—of which UV is most common. UV ink systems provide many benefits that include ink holdout, ink durability and less dot gain. Dot gain, also known as Tonal Value Increase (TVI), is the phenome- non where ink halftones grow in size when printed onto the substrate. Upon its impression, the dot will almost always increase in size in virtually every printing method. This can be potentially detrimental to images because the ink dots can increase the density of the image, making it darker and incongruent with the desired physical visual manifestation of what was on the screen or in the original image. There are ways to compensate for this in file preparation for print; however, in the end having less dot gain means an image with greater contrast. This is very important in the print and packaging industry to maximize image quality. The higher the image quality of the product, the more pleasing it is to the human eye. UV ink systems can deliver the necessary quality that clients demand. UV OVERVIEW LED UV technology has recently been commercialized for the narrow web flexographic press and there are few existing data sets comparing the two differing technologies. UV is used in the flexographic indus- try because of the high quality and high durability of the product once it has been cured. There is a large range of substrates that UV can adhere to while delivering a wide spectrum of rich colors. This study examines the economics, sustainability and workflow influences of conventional UV flexo and LED UV flexo printing. Initially, conventional UV and LED UV flexo printing is expensive. Both technologies require up front capital costs and, depending on the size of the press, each ink unit requires an individual lamp to cure its respective ink. However, the differences between the two curing methods are discrepancies in heat energy loss, the space required for the curing lamps and press speed. The outcome of this study docu- ments findings of key variables, potential savings and process benefits 30 FLEXO | AUGUST 2014 FTA TODAY PART 1 INA SERIES