The design of an inkjet printer requires the mechanical components, the imaging ink and, in many cases, the receiving material. Ink chemistry is a key link, determining different properties such as viscosity, droplet flight, corrosion properties, surface tension, drying time, dot shape, optical density and edge acuity, fade resistance and compatibility with printing surfaces.
Traditionally, inks have been liquid, with a water or solvent base. Continuous inkjet inks are typically based on one of a variety of solvents and dry quickly on both porous and non-porous substrates. Impulse inkjet printers require high boiling point inks, usually water-based inks. Several recently commercialized or wax materials are melted to be sprayed, but solidify immediately on the receiver. Proponents claim that solid ink solves print quality problems caused by ink wicking undesirably into paper fibers, though at the cost of considerable system complexity and embossed output, which some find objectionable.
Ink formulation involves a series of trade-offs, depending on the type of printing system and the requirements of the target application. For example, in a pulse-jet system where there is a risk of nozzle clogging, the inks must not dry inside the nozzle; however once ejected, they need to dry fast enough on the paper to minimize paper fiber feathering. The difficulty of the job ranges from the fact that very few inkjet printers today offer true plain paper printing; most systems require special clay-coated paper to prevent perspiration, a drawback in office environments.
Colorants in inkjet inks also present challenges. Because pigment particles can make ink too viscous, possibly causing clogging or excessive fraying, use dye instead. Problems that arise include lack of optical density (light gray shade) and archiving issues due to fading tendencies.
The success of inkjet printing depends on developing requirements to match system capabilities to printing . For many years, inkjet products have prioritized speed and surface independence over image quality (for example, for package coding and direct mail). Recent improvements in reliability, resolution, paper tolerance, and colorants could finally bring high-quality office printing and color applications within reach.
Inkjet has been one of the most challenging output technologies, requiring significant R&D spending and a long history of failed products. However, recent advances suggest that the allure of inkjet as a potentially elegant, low-cost printing solution will eventually be justified.
