It is the scope of this Nordic R&D project on "Innovative development of the ink-jet technology" to utilise the outcome of national research programmes and to establish a Nordic network of research institutes, material suppliers, printer manufacturers and end users of the ink-jet technology.
The focus is on developing a normative specification and documentation of adequate measuring techniques for materials and process parameters for different application of the ink-jet technology. Special attention is paid to the influence of paper and ink properties on spreading and penetration, an hence, on print quality. Print quality is here seen in terms of image analytical factors, like dot size, darkness and roundness.
The first two steps of the project included an inventory of Nordic and international re-search results on ink-jet printing and a documentation of measuring methods, especially methods for drop formation, spreading and absorption when printing with different printer heads and substrates. These steps have been reported in a separate report.
The further work focused on practical material characterisation and nteraction mechanisms in ink-jet printing. In these tests a representative selection of substrates and inks were further analysed on a laboratory level and test printed. Based on the results recom-mendations for material properties and process conditions, as well as measuring methods have been developed, and are reported here.
The project also discovered still remaining problem areas in the ink-jet method, where improvement can be achieved through a continued co-operation between scientists, material suppliers, equipment manufacturers and end-users. At the end we present preliminary plans for such a developing project.
A summary of the survey
Based on the results collected from the literature and earlier studies at the research partners, the following general conclusions made be drawn about the known interactions in ink-jet printing:
- Absorption properties of the substrate and the tone value of the ink determines the intensity of the print
- Spreading dynamics depend on the amount of liquid in the ink, the kinetic energy of the droplets, rheology of the ink (ink dependent) and the surface energy and absorptivity of the substrate
- The inks are solvent-based, oil-based, water-borne, UV-curable or hot-melt or combinations of these; colorants are dyes or pigments
- Print quality is preferably evaluated by image analysis in parameters from dots, fonts, lines and solid areas
- Dynamic interactions are measured with a high-speed CCD camera for small drops
- Surface energy is evaluated using contact angles, dynamic wetting, surface energy composition, and profilometry
- The most important ink characteristics for the interaction with the substrate are rheology, surface tension and particle size distribution
Project duration: 01.10.2001 - 30.06.2003