Inkjet inks – Pigment or dye-based? A technical comparison

Dye-based ink

On one side, we find dye-based inks using a dye which is usually organic. This is somewhat similar to the ink used in a common fountain pen: in a solvant (often plain water, sometimes alcohol, exceptionally an oil) colored molecules are presented coming from an organic chemical compound.

This could be seen as quite similar to water-colour painting. Canon is mostly using this type of ink for its inkjet printers.

Pigment ink

Exactly at the opposite are the inks incorporating a pigment. It is no longer a colored chemical solution but a liquid holding some colored particles. These are most often mineral compounds selected for their very good stability; they are often protected by an additional thin resin coating.

Oil painting is using a very similar technique (using particles that may be much larger than those used for inkjet printers).

Epson introduced sets of pigment-base inks when they started promoting long-life prints on matte papers (one century or more).

Dye-based ink

This technology is very well mastered in the industry for years (they started long before inkjet printers appeared on the market).

Pigment ink

Pigment technology is difficult to master (taking into account the small size of the particles to create in large quantities). You have to manufacture nano-sized particles that will be coated in a thin resin layer.

The resin will be used to protect the pigment against external mechanical and chemical attacks, but it also helps in transporting easily the particle inside the ink (and through the nozzles) and fixing it onto the paper.
It is easily seen that these contrdictory constraints make this technology more difficult to master.

As the ink is actually suspended inside a holding liquid, this creates some problems for storage (to avoid sedimentation) and moving the ink.

When drying, this ink could easily plug the holes used to project the ink on the paper. This requires specific attention to ink management.

Dye-based ink

This ink is generally cheap (even if the manufacturing cost is only one factor in determining the selling price of inkjet ink).

Dye is quite fragile. When exposed to light (and Ultra-Violet light), the colored molecule can easily be broken and loose its color. this leads to prints that loose their original colors and fade to white or change their colors in time.

Ozone and several other common pollutants also are able to break chemically down the color molecules. The result is the same as with light.

Drying time is directly linked to the drying time of the solvant on the paper (this can lead to premature closing of nozzles if the ink is set to dry quickly on paper). On the contrary, if the paper is not able to absorb quickly the ink and its solvant, there is a risk of ink flow or paper deformation. To favor a fast drying, it is better to use a microporous paper (despite its bad consequences on chemical degradation of the resulting print).

Pigment ink

This solution gives the best possible lifetime for your prints (specialy if the paper is designed to protect the ink as many matte papers selected for archival, but not microporous papers). It is thus no surprise that Epson printers for archival and long lifetime purposes are using such pigments (resulting in more than a century of conservation).

Degradation of pigments by gazeous pollutants and ozone is very limited. The presence of the resin coating limits it further.

Color density is usually better, or easier to reach than with dye-based inks.

However, pigments tends to promote a defect known as bronzing where, when brightly lit or lit under low incidence, the print will show unpleasant metal-like reflections

Manufacturing cost being higher, ink prices are quite high too for the user.