Dye and pigment inks for ink jet applications usually strive for different parts of the non-impact printing market, where their respective key benefits can be fully exploited (brilliancy vs. fastness). The use of pigments as ink jet colorants, instead of dyes, usually provides an adequate answer to image degradation caused by environmental factors such as light, moisture and atmospheric pollutants, and enables the production of digital graphics that meet the stringent durability criteria required for outdoor display. However, the particularities of ink jet technology (firing of tiny droplets through ultra fine nozzles, low ink viscosity...) makes the formulation of pigment inks quite demanding and an accurate selection of the key ingredients is crucial to reliably performing inks and high quality, colorful prints. This paper will review the prerequisites for effective pigmented ink jet inks and give hints to proper pigment selection in terms of chemistry, particle size, surface modification and chemical purity.
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