When choosing dyed for water based inkjet inks the choice is a bit limited as the vehicle restricts the types of dyes. It is a fact that water based ink will accept only dyes that are water soluble. Dyes that are used for water based inkjet inks must provide colours that are highly saturated. Should scatter or refract only a very little amount of light. Various class of dyestuffs has been developed like reactive, direct, acid or base for application in Inkjet Inks.

Water based Ink-jet inks that has good pH stability may be made by using yellow dyes and buffers. Examples can be given of yellow dyes made from water-soluble azo and bis azo dyes. Some of the products in this category are C.I. Direct Yellow 142, C.I. Direct Yellow 86, C.I. Direct Yellow 132, C.I. Direct Yellow 173 etc.

As the inkjet inks are employed for very delicate purposes that requires precision, so the dyes used must be of very high standard and quality. It should show the following qualities.

• Extremely low salt content (content with respect to Chlorine, Sulfate, Calcium, Magnesium, pH, solubility, strength and shade).
• Light and water fastness should be high.
• Excellent tinctorial strength and brilliancy.
• Fairly good surface tension.
• High purity: The users well understand the critical importance of high purity in inkjet printing. It is pertinent to employ purification techniques that enables to remove inorganic salts along with tracing of filter inks andorganics to levels of submicrons. A combination of the following processing technology is a must:
  • Reverse osmosis/Ultrafiltration- for removal of inorganic salt.
  • Ion exchange - to improving solubility.
  • Carbon treatment - that improves surface tension.
  • Microfiltration - effective in removal of 99.9% of insolubles.
  • Specialized cartridge filtration (low to the level of 0.2 micron) - that can filter out most insolubles.
• Protection against gas fade stability.