Digital textile printing began in earnest in the 1990s, but technology, market, and supply chain challenges have kept it from going truly mainstream. So far. At the same time, older analog technologies, primarily screen printing, have dominated the textile printing market for decades. However, all of these challenges—technology, market, and even supply chain—are gradually being overcome, and digital textile printing, in all its myriad forms, may well be on its way to displace traditional textile printing methods.
Talking about the “textile printing market” is a bit like talking about the “commercial printing market.” It includes a wide variety of products and niches, each of which has its own dynamics. Different types of textile printing niches are very different from each other.
We can identify three general categories of textile printing:
- signage/visual communication
In the full white paper, we will look at all three of these categories. In this feature excerpt, we will concentrate on signage/visual communication and specifically soft signage, although many of the same considerations apply across all of these categories.
The term “soft signage” is one of those terms that can mean different things to different people, but for the purposes of this feature and the forthcoming white paper, we will define soft signage as “display graphics printed on a textile- or fabric-based substrate.” This is distinct from what might call “hard signage” that is printed either directly on a rigid material like board or plastic, or is printed on paper then mounted.
This category can include, but is by no means limited to:
- Point-of-sale/point-of-purchase (POP/POS) displays
- Indoor wall graphics
- Trade-show displays
- Block outs
- Outdoor advertising
- Backdrops (theater/TV)
Currently, many of these product areas (like POP/POS displays, posters, and other types of displays) are printed on rigid or at least mountable materials, while those that are printed on soft substrates (like flags) are still often printed using an analog process.
The top product areas for companies in this category, according to research conducted by the SGIA, are banners, indoor wall graphics and window displays, with indoor wall graphics seeing the strongest growth. We are also seeing a large growth in flags and banners—national flags, to be sure, but also flags and banners for different clubs, groups, or organizations. Soft wayfinding signage at events—such as “this way to the keynote address in Room 201C”—is also on the rise.
Screen printing has come to dominate the textile printing market, but historically other methods for printing on fabrics, either directly or indirectly, existed. One of the most popular—taking a backseat only to screen—is dye-sublimation. There are many “flavors” of dye-sublimation, but for the purposes of printing on textiles, it has traditionally involved a two-step process, although that is changing. Dye-sub inks comprise a pigment suspended in a liquid solvent. Images are first printed onto a transfer paper, which is then brought into contact with a polyester fabric using a heat press. Under heat and pressure, the dye turns into a gas (i.e., sublimates) and imprints the fabric, solidifying onto the fibers. The advantage of the process is that the resultant print is waterproof.
(Sublimation is a physical process whereby a solid transitions directly to the gas phase without first passing through the liquid phase. One common example of sublimation in action is dry ice—frozen carbon dioxide—solid chunks or pellets of which immediately become a gas at room temperature, or at the temperature of, say, a Pink Floyd concert, for those who recall such things.)
There are now also dye-sublimation inks that can print directly onto fabrics without requiring a transfer sheet. We’ll return to this, but different types of fabrics have required different types of inks; printing on some types of natural fibers like cotton or linen requires a reactive dye ink, while printing on synthetic fibers like polyester, or natural fibers like wool requires an acid dye ink.
Printing—virtually any printing—is the result of a complex physical and chemical relationship between ink and substrate, and the quality of the resulting print will be a direct result of that relationship. One of the biggest stumbling blocks in the area of textile printing has been getting inks to adhere to fabrics and then be able to survive whatever end use is intended for the printed materials. New ink developments like ultraviolet (UV) curing and latex have solved many of these challenges, and it could be said that it is largely the new inksets that have allowed direct digital textile printing to be poised for takeoff.
Wide-format printing in general uses a variety of different ink technologies, not all of which are relevant to the textile/soft signage conversation:
Solvent inks—These inks largely consist of volatile organic compounds (VOCs) which evaporate readily and thus the ink dries quickly. Solvent inks, being pigment- rather than dye-based, makes them long-lasting and fade-resistant. They are also inexpensive and waterproof. The vapors can be toxic, and discarding the detritus is an environmental issue. So-called eco-solvent inks consist of a “milder” type of solvent that take longer to evaporate and can require heat, but are less hazardous.
Aqueous inks—These inks use as their primary solvent water (or some other relatively benign liquid vehicle) and can be dye- or pigment-based. Aqueous inks often require special coated substrates to adhere properly, and are not always well-suited to non-paper substrates such as plastics or vinyls.
Ultraviolet-curing (UV) inks—These inks consist of chemicals that, when exposed to ultraviolet light, dry more or less instantly. They can be used on a wide variety of substrates such as plastics, vinyl, foil, and other specialty substrates, and offer increased health and safety for press operators and the environment. Some new presses use cooler and faster LED UV curing lamps.
Latex inks—“Latex” is a generic chemical term that refers to a “stable dispersion (emulsion) of polymer microparticles in an aqueous medium,” and latex inks are water-based, and they are able to print on a wide variety of coated and uncoated substrates, especially textiles, for both indoor and outdoor use on the same machine. They also dry quickly.
Dye-sublimation inks—As mentioned earlier, these inks consist of a pigment suspended in a liquid solvent that, under heat and pressure, turns into a gas and thus prints on the fabric. Dye-sublimation inks may require a transfer paper to “offset” the image from the imaging heads to the substrate, although newer systems are taking the transfer paper out of the process and printing directly on the substrate. It is also common to see references to “aqueous sublimation ink,” which means that the liquid vehicle is largely water-based. Direct-to-print print dye sub has advantages over dye-sub utilizing thermal transfer, such as better penetration of ink/pigment in the textile substrate, no need for transfer paper, and greater flexibility.
For the purposes of digital textile printing, we can sum up the advantages and disadvantages of each as follows:
Table 1: Advantages and Disadvantages of Major Ink Technologies for Textile Printing
ability to print on many kinds of materials
no hazardous vapors
resistance to solvents (like cleaners)
no hazardous vapors
wide color gamut
washability, esp. sublimation transfer
tendency to “stiffen” fabric
inability to print flags/duplexed materials because of front and back density issues
lack of abrasion-resistance on porous materials
lack of color vibrancy
high drying energy consumption
lack of UV resistance/lightfastness
need for transfer press if using sublimation transfer
“halo” effect, or softness in the printed image
VOCs/hazardous vapors; need for ventilation system
require coated textiles for proper adhesion, durability
Some disadvantages can be obviated by switching substrates, and it should be no surprise that inks generally perform better on substrates that are treated or coated in some fashion. Advantages and disadvantages can also vary based on the end use of a given printed product. That is, “lightfastness” is an issue for materials designed for outdoor applications, but not so much for indoor applications. “Durability” will be an issue only if a particular product is designed to be manhandled ion some way, but not necessarily if it is going to be used as static signage. Signage that is only very temporary—think of the wayfinding example earlier—will not need to be durable or longlasting.
Traditionally, the substrate of choice for soft signage and many other applications in the “visual communication” category has been some form of polyester. While it is common to use the term, “polyester” as if it referred to one kind of material, the term refers to a broad class of polymers and there are a number of different kinds of polyester, both natural and synthetic. When we speak of “polyester,” though, we typically refer to polyethylene terephthalate (PET).
Nylon is another common synthetic fabric and remains one of the most widely used synthetic textiles. (Nylon is not chemically considered a polyester but is rather a polyamide.) Its claim to fame was as a replacement for silk, but has come to be used in a wide variety of textiles, especially flags.
Natural fibers are also commonly used for textiles and textile printing. Cotton, silk, wool, and yarns are commonly used, but natural fiber-based substrates have traditionally been the purview of screen printing, as inks used in digital printing systems have had challenges with natural fibers. Printing on synthetics has tended to be easier.
As with any printing application, thought needs to be given to what will eventually be done with the print when it comes off press. In textile printing, finishing processes can be as varied as in other types of wide-format or specialty printing, and can include sewing, cutting, welding, grommeting, and more. If you are printing apparel, there may be clasps, zippers, and other fasteners to include. If you are printing signage, how will it be displayed? It may need to be installed in some kind of frame, which needs to be taken into account.
One common textile finishing process is calendering (the term derives from a similar process in papermaking), which squeezes the printed fabric through metal rollers under high temperature and pressure. The purpose is severalfold; it fixes the ink onto the fibers, it imparts a high smoothness to, and dewrinkles, the printed fabric (rather like ironing a shirt), and/or it adds some kind of texture or effect to the print by using rollers that have some kind of pattern on them.
Calendering units have traditionally been sold as separate standalone offline units, but some newer textile printing devices offer inline calendering, which is a cost and space saving for shops.
Opportunities for Print Service Providers
Two weeks ago, my colleague Marco Boer of IT Strategies wrote in this space, “it is now possible in 2013 to say that digital textile printing has achieved breakthrough success in soft signage and production apparel printing. Vendor revenues for dedicated systems and ink for digital printing of textiles have come close to $1 billion and are growing at 16%.” He adds:
In general, in both the low- and high-end markets about three-fourths of output on dedicated roll-to-roll textile printers is soft signage and one-fourth is the other apparel-related output. In other words, soft signage drives the growth of roll-to-roll dedicated inkjet textile systems.
The advantages of soft signage vs. hard signage for the end user are many. For one thing, it is lighter and easier and cheaper to transport and install. Think of a fabric banner that can be rolled up and shopped in a tube vs. a large rigid display. The opportunities for the print provider lie in identifying exploitable niches. At present, soft signage is not substantially displacing other kinds of signage—either printed on other types of wide-format printing technologies, or using analog methods—but is creating demand for new kinds of signage, or products that would have been prohibitively expensive if produced using other means. At the same time, few wide-format print providers—and few textile print providers—specialize in a single product area; most offer up to a dozen different products, albeit related to each other in how they are produced. Think of it as “specialist diversification.”
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