Pigmented/Dye-based Inks
Another major recent development in the inkjet printing industry is the successful implementation and commercialisation of pigmented inks in colour printing applications. Many companies including recognised colour quality leaders like 3M, Dupont and Kodak already have pigmented inkjet ink products on the market.
Dye based inks are made by completely dissolving dyes in a carrier that enables the dye to be easily applied. Dyes are much stronger and produce more colour of a given density per unit of mass. However, one significant advantage of pigment-based as compared to dye-based ink is its colour durability when exposed to light or extreme weather conditions. This feature is critical to applications such as billboards or other large-format displays. Dyes will soak into the paper fibres and spread out more, which means that they are less light fast and fade quicker, often after only 6-12 months, whereas pigmented inks can last several years. Dye inks are also less water resistant, as the pigmented ink’s particles tend to get stuck in paper fibres as the ink dries, so only about 5-10% will re-dissolve if splashed with water. This tendency of dye inks to soak into the fibres can also lead to problems with bleed and wicking and result in poor quality printing.
Pigmented inks are formed by suspending small coloured particles in a carrier, as opposed to dissolving them. Particles are coated in a polymer to generate a static charge around the particle to keep them from sticking together. The pigment sits on the surface of the paper more readily than a dye; hence less ink is needed to create the same density of colour and the small particle size allows sharper image detail. However, as compared to dye-base, pigment-based ink has the inherent disadvantage of particle dispersion instability that may lead to nozzle clogging, and with the aforementioned design trend towards smaller nozzle diameter, this could become more of a concern. Pigmented inks also have a lower rub resistance and are more sensitive to scratching.