Exhibition Poster Printing - Ink Technology
Posted: Tuesday, July 07, 2009
by Matthew Theobald
Exhibition display solutions
Types of Ink.
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. These molecules have a very high colour saturation and in combination are able to produce a wide range of colours. However the ability to resist light isnt good and they are subject to damage by water once printed onto the substrate. Because the colour is dissolved, it exists at a molecular level and as such it is much more accepting of variations in the quality of the substrate and more importantly the coating on that substrate.
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 much more fade resistant and can have a limited outdoor application as they are not adversely affected by water once they have dried. 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.
The pigment is held in solution in a carrier together with an adhesive. Once the droplet of ink is sprayed onto the substrate the solvent evaporates leaving the pigment to stick to the surface with resin.
The Solvent inks are delivered onto the substrate using Piezo printhead technology that ensures an accurate and fast print.
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.
The resultant print is weatherproof and fade-proof and, to a certain extent, scratch-proof.
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.
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Matt has been involved in the design and production of exhibition stands for 2 decades and has run his large-format digital printing business in Maidenhead for the last 8 years. http://www.exdisplay.co.uk
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