9
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.