The development of textile specific ink chemistry is an ongoing effort in the area of digital textile printing. Jetable inks must be highly purified in order to reliably run through the sensitive ink jet nozzles. Ink sets that are currently available are based on traditional printing chemistry and include acid dyes, reactive dyes, disperse dyes, and pigments. At [TC]² we are currently printing with reactive and acid dyes as well as nano colorant pigment inks.

As in the conventional printing environment, the ink chemistry must be matched with the appropriate fiber type to ensure permanent color fixation. The selection of colorants available make it possible to print a wide variety of fiber types:

Acid dyes - silk, nylon and wool
Reactive dyes - cotton, rayon, linen and silk
Disperse dyes - polyester
Pigments - not fiber specific, often used for cotton and blends (e.g. poly/cotton)

Color Fixation
Most print systems require post-processing to enable the fixation process to occur. While dye based printing systems all involve penetration of the colorant into the fiber, pigment printing involves adhesion of the color to the surface of the fiber via a binder.

Reactive and Acid Dyes - normally require color fixation in the presence of steam at atmospheric conditions. Reactive dyes typically require less than 15 minutes of steaming, while acid dyes normally require at least 30 minutes of steaming.

Disperse dyes - The requirements of disperse dyes depend on the type of disperse ink being utilized. Some disperse dyes are applied via 'sublimation' using dry heat to 'transfer' an image from a paper carrier to the fabric. These colorants are increasingly being promoted for direct printing of polyester substrates for soft signage applications. Note that in addition, there is a specialized group of disperse dyes suitable for direct printing that require a greater amount of energy to enable fixation than those called 'sublimation inks'. These colorants are often steamed under pressurized conditions to drive the color into the fiber.

Pigments - dry heat or 'curing' is typically used to activate the binder system.

Research & Development
Ongoing research in the ink development area has lead to improvements in color brilliance, fastness, and jettability. Reactive and acid inks were first to enter the marketplace, while disperse and pigment inks have been more challenging chemistry types to formulate. Development of alternate colorant chemistries is of particular interest to digital print users as innovative approaches may reduce or eliminate wet finishing requirements and other pre and post processing steps for the creation of a more efficient print process. In this area, [TC]² is currently investigating the application of nano colorants as a chemistry type that reduces processing requirements and supports more eco-friendly textile coloration. This research has been supported in part by [TC]² member, Yuhan-Kimberly, a developer of textile colorants for digital printing and now Expand Systems, US distributor of the technology. Click here to learn more about this research.

Links
Visit our vendor directory to learn more about ink chemistry options.