Digital Transfers

Digital Transfers in a World of Sublimation

Wayne Potter is vice president of marketing development for Air Waves Inc., Lewis Center, Ohio. He has 30-plus years’ experience in the heat transfer and digital imaging market.

I have devoted a considerable number of my articles to polymer coated heat-transfer papers, eco-solvent heat-transfer flex, and sheet-feed inkjet sublimation. These digital techniques have made their mark and are playing an increasing role in small-scale apparel decoration.

Historically, most milestones in this area were achieved using screen printing technology.  Now, digital plays an increasing role in producing decorated cut parts. For years, the manufacturers of direct digital inkjet printing promised their technology would substantially influence textile printing. In fact, there was a claim that this technology would overtake dye-sublimation transfer printing. This hasn’t happened but the technology still exists is seriously challenging analog printing technologies. I refer to this as the “other inkjet.”

Digital roots

A good portion of digital growth has been in the so-called soft signage area. Recent surveys by industry groups indicate that more than 75 percent of those surveyed report growth in textile décor applications.

This new specialized digital inkjet printing technology has many faces beyond direct–to-garment printing. Back in the early 90s, wide-format inkjet color printers came to market. Followed shortly thereafter by large (18"–100") and grand (100"-plus) format, this inkjet technology was modified to print sublimation dye inks directly onto synthetic fabrics. A heating step was required to diffuse the printed dye into the fibers of the synthetic fabric. As the technology developed, many major printer manufacturers began to produce inkjet printers designed for direct printing on textiles.

This process has been around since the early 1990s when wide-format color inkjet printers became widely used.  Throughout the past 25 years, inkjet technology has changed with an ever-wider assortment of nozzles, higher resolution heads, smaller droplet sizes, and new feeder types. 

However, interest in adapting wide-format color inkjet technology to textile printing took longer. Initially, printer manufacturers modified inkjet printers to print with sublimation dyes, either directly or indirectly to polyester fabrics. As the technology developed, printing onto cotton, nylon, silk, and other cellulose-based textile fibers became a reality. 

Originally, textiles were paper-backed so that they could run through the pinch and grit feed-roller components of an inkjet printer. In the early 2000s, the Hewlett Packard Designjet 5,000 series printers were modified to accept these paper-backed textiles. The technique allowed for production of banners and signage and although discontinued, many are still in use today.

Obviously, feeding was an issue and paper-backed fabric could only take the industry so far. Several mainstream manufacturers modified paper roll-to-roll inkjet printers for textile production.  Although the industry-standard pinch and grit feed systems proved to be problematic for many textiles, over time the roller components matured and eventually gave way to a roll-to-roll tension system that evenly fed the fabric through the printer.

The next step was the development of a new fabric transport coupled with a bulk-ink delivery system that would become the catalyst for many other innovations in early direct-to-fabric inkjet printing. 

As general printer technology advanced, so did roll-to-roll transport systems. In Italy, sticky moving belt transport systems came into being, and eventually spread to the domestic high-end textile printer market as well. This technology holds the fabric in place so there is no stretch during printing. 

Gradually, stand-alone roll-to-roll inkjet printers with integrated components began showing up. What followed were high-end textile inkjet printers paired with stand-alone heat fixation units.

Dye details

Dyeing and decorating textiles produces a considerable amount of waste and consumes a large amount of water in the process. Now, with mass customization of textiles and pressures on sustainability, I believe there is pressure on the market for cleaner running, lower priced equipment, which is where dye-sublimation comes into play.

Dye-Sublimation is a broad encompassing term that is often misinterpreted by users. The technology most familiar to small-scale decorators is only one of a number of dyes that can be used to decorate textiles. Given this, what are the other dyes that are used in direct-to-fabric textile decoration?

The sublimation that is near and dear to our hearts is intended to decorate polyester. The ink chemistry used in the direct printing of textiles must be appropriate for the fabric to be decorated. Contrary to popular belief, cotton, silk, nylon, and wool can also be printed using dye-sublimation inkjet technology—the proper techniques and inks just need to be put into place. The following dye types are all suitable for dye sublimation for fabric and should be considered tools for any decorators arsenal.

Acid dyes

Acid dyes are salts of organic acids. They are typically water-soluble and have an affinity to silk, wool and nylon. The fibers in these textiles have positively charged ions that are naturally attracted to the negatively charged ions in the acid dye. Once directly printed to the fabric, these dyes must be steamed to set them. During the steaming process, the ink molecules form a powerful bond with the fiber in the fabric and the subsequent scouring or washing removes any latent dye before use.

Reactive Dyes

Reactive dyes are a group of highly colored organic chemical substances that attach themselves to the fabric by a chemical reaction that involves sharing of electron pairs between the dye and the fiber. Fiber reactive dyes are among some of the most permanent dye use for textiles. Reactive dyes must also be steamed to fix them into the fiber and then subsequently washed to remove the residual printed dye. Reactive dyes are faster and require considerably less time to fix. 

Dispersed polyester dyes

Dispersed polyester dyes are used most commonly by decorators for printing directly onto polyester textiles. Low energy dispersed dyes that are typically printed onto a special paper and then transferred to the fabric with a heat transfer machine. Decorators also use these dyes for decorating mugs and other hard surface items. 

There are two additional classes of dispersed dye: medium and high. Medium energy dyes are suitable for indirect carrier paper printing while high energy dispersed dyes are used to print directly on to textiles and are the top choice for direct digital inkjet printing.  In this method, after the fabric has been printed, the dye is heat set in an oven or with a heat-calendaring machine.

Traditional textile printing produces a large amount of toxic dye waste and water and has high-energy usage, both taxing on the environment. Digital textile printing with dye sublimation is a viable alternative since energy savings can be quite substantial and there is less chemical waste. The overall production footprint is also reduced.

Many traditional textile decorators look at digital inkjet printing and cite what it can’t do compared to their technology. However there is a growing group of designers, textile artists and creative Internet entrepreneurs that look at direct to fabric inkjet and say why not? Perfect for sampling and small run production, this digital form of decoration addresses many of today’s issues from a reduced environmental impact to the modular nature of modern life. Paired with highly detailed finished designs and improved technology, when weighed against other more traditional methods of decoration, this digital wunderkind can increasingly hold its own.