Critical Factors for digital Printing on Paperboard : Runnability, Functionality & Print Quality

Abstract: More than ten years ago, the first digital print units were introduced on the market and since then, the technology has developed rapidly. Digital printing on packaging material is, however, a rather new area, but a probable prediction is that there soon will be a market need for board products that can be used for digital printing. In order to become successful in digital packaging printing it is, however, important to gain knowledge about the interaction between the substrate and the press, when it comes to runnability, functionality and print quality. Test printing was performed on paperboard, in digital print units based on both dry and liquid toner electrophotographic technology. Print quality was mainly investigated with subjective evaluation. Regarding functionality, investigation of taste and odor,creasing, toner adhesion and stability of whiteness in digital printed paperboard were performed. The runnability was investigated by subjective observances during printing trials, but also additive mesaurements. The subjective print quality evaluation indicated that paperboard, successfully could be used within digital printing in the same extent as paper grades. The differences in print quality were mainly explained with different characteristics of the paperboard i.e. if the paperboard, for example,had initial unevenness, high roughness or higher moisture content. However, the print units and their settings, also, played an important role. The functionality studies mainly showed a positive result, but regarding toner adhesion some problems occurred in the liquid toner technology. Furthermore, the three main problems concerning runnability were; feeding in sheet fed print units, cutting in web fed print units and increasing curl or non-flatness after printing.