Digital Printing and Large-Format Displays - Types of Ink

Three main types of ink are used in today's inkjet printers: Solvent, water, and oil based. Oil based inks had a fairly brief career and have now generally been dropped in favour of solvent based inks

There are three main types of ink used in inkjet printers: Solvent, water, and oil based.

Water-based inks: Water-based or Aqueous/thermal inks are divided into two categories, Pigmented Inks and Dye inks.

Dye inks are formulated with the tiny molecules carrying the colour property suspended in a water-based carrier solution. They have a high colour brilliance and a wide gamut of colour. However the ability to resist light isn?t good and they are subject to damage by water once printed onto the substrate. Because the colour is held in solution the size of the colour carrying element is minute and therefore is more tolerant of the make up of the paper it is being printed onto and also tends to dry faster.

Pigmented Inks.

Particles of pigment are held in suspension in a water-based carrier liquid. These particles of pigment have a vastly greater size that the smaller than microscopic molecules dissolved in solution utilized in dye based inks. They are very resistant to fading and the effects ofwater damage and can even be used outside for a limited time. As the pigments have a much bulkier make up the substrate needs to be coated, or be more porous to allow the ink to adhere and dry effectively.

Solvent-based Inks.

Inks in this category can be broken down into 2 groups that are referred to in a number of different ways including: soft, mild, safe, eco, and green as well as hard, real, true, and strong. The term 'eco' is usually attached to products that are in harmony with the environment; however, in the context of solvent inks which utilise chemicals derived from oil, this tag must be treated with a large amount of skepticism. The agressive solvents are able to produce acceptable results on a wide range of medias - generally at a cheaper cost as the media does not need coating as with the milder solvent inks.

Both types of solvent ink uses a fine powder pigment which is dissolved into a solvent carrier fluid combined with a resin or glue. Once the ink is on the surface, the solvent evaporates off (usually with an unpleasant odour filling the room) and the adhesive sticks the pigment particle to the surface.

Piezo print heads spray the ink onto the print surface creating a fast print speed with extremely accurate dot placement and long head lifespan.

Unlike water based inks where the substrate needs to be coated with an ink-receptive layer the solvent process can produce prints suitable for exterior use on non-absorbent, uncoated materials such as self-adhesive vinyl and scrim banner fabrics, pvc and polyester.

Prints produced in this way are far more resilient to fading and scratching.

The Mild Solvent Inks use slow drying carrier fluids and so printers that utilise this type of ink usually have heaters to dry the ink as it is printed.

Agressive solvents dry faster and have the added benefit of softening the substrate surface creating a stronger bond.