Studies on fastness properties of ink jet prints on coated papers

摘要

Novel low-cost coatings intended for ink jet printing have been developed recently. Studies on their print quality have mainly focused on the optical and geometrical properties of the image, whereas their effect on long-term print quality has been largely ignored.The objectives of this thesis were to evaluate the applicability of vibrational spectroscopic methods for studying ink jet prints and to clarify the mechanisms contributing to the permanence of small-scale ink jet prints on coated papers. Light and water fastness in the time-scale of the print's end use were of particular interest. These were studied using experimental inks and coatings with known compositions.The first part of the study concerned the applicability of vibrational spectroscopic methods for studying ink jet prints. According to the results, differences between the samples originating from changes in exposure to light could be detected with both FTIR and Raman spectroscopy. The most suitable techniques were the FTIR-ATR, confocal NIR-Raman, UV resonance Raman and Kerr gated resonance Raman methods.The second part of the thesis detailed the issues related to the mechanisms contributing to print permanence. The results suggested that the light and water fastness of ink jet prints were affected by both the physical properties of the coatings and the chemical paper-ink interactions. The latter played the dominant role, whereas the significance of physical paper properties depended on the type of ink and the coating. As a rule, the stronger the chemical paper-ink interactions were, the less relevance the physical properties of the coating had. Results also indicated that light and water fastness could be markedly influenced by the type of colorant, but also by choosing the right coating ingredients.