Optical properties of digital inks on straw-containing papers with TiO2-based coating upon ageing

Compared to papers derived from virgin fibres, recycled papers possess somewhat limited optical, strength and printing properties. Strength properties are usually increased by blending recycled fibres with virgin fibres in pulp for paper production, while optical and printing properties are often improved by coating after the paper is being manufactured. In this study, the usability of virgin fibres derived from straw as the agricultural residue of wheat, barley and triticale crops for paper production was evaluated based on the stability of prints on laboratory-made paper. For that purpose, in laboratory conditions, the papers with the addition of straw pulp in the pulp of recycled fibres were formed and prior to printing they were coated with TiO2-based coating. Process inks, in full-tone, were applied on coated straw-containing papers by digital printing process. Optical properties of digital prints upon accelerated ageing were evaluated based on Euclidean colour difference calculated from spectrophotometric values measured on black and magenta prints before and after 48 h and 96 h of ageing. The obtained results were compared with those provided by printing substrates made only from recycled fibres with and without TiO2-based coating. It was observed that TiO2-based coating has no influence on the stability of black digital prints, while each layer of TiO2-based coating reduces deviations in magenta colour upon ageing.