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
- 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
- Reverse osmosis/Ultrafiltration- for removal of inorganic
- 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.