Wide-format Printing: Ink options for fabrics, soft signage and interior décor

by all | 14 July 2015 2:46 pm

By Ken VanHorn and Tommy Martin
In the wide-format digital printing industry, the term ‘textile’ has been used to encompass a variety of applications, materials and processes, including wearables, soft signage, interior décor, environmental graphics and other applications using dye sublimation, direct-to-fabric printing or another transfer process.

Both dye sublimation and direct-to-fabric processes have seen a resurgence in recent years, driven by the larger shift from traditional analogue screenprinting to digital wide-format printing. Today’s inkjet printing options for textile-based interior décor and soft signage applications include solvent-based, ‘eco-solvent,’ durable aqueous ‘latex’, ultraviolet-curable (UV-curable) and even solvent UV inks.

Different printing technologies offer different strengths and are suitable for different applications. Signmakers need to understand these processes from the perspective of the specific inks.

Dye sublimation inks
Also called ‘dispersion inks,’ dye sublimation inks yield vibrant colours that can stand up to repeated washing. They are limited to printing on polyester-based or polymer-coated materials and offer lower outdoor longevity than some of the other options. As such, they are primarily used in the active sportswear and exhibit graphics markets.

Typically, but not always, dye sublimation inks use a transfer process, i.e. they are printed to an inexpensive paper before they are transferred to a textile substrate. In the post-printing step, the printed transfer paper roll is aligned to the ‘accepting’ fabric roll and the two are then processed together in a calender heat press for 30 to 45 seconds at high temperatures, up to 204 C (400 F).

The transfer process allows users to sublimate not only polyester-based textiles, but also a wide range of polyester-coated rigid substrates, including unusual shapes like coffee mugs. The transfer paper itself is relatively easy to handle and the resulting graphics can convey sharp colours and clear images.

Dye sublimation inks can also be printed directly onto fabrics, eliminating the need for transfer paper and reducing the number of steps in the overall process; but the fabrics for direct printing need to be coated, which increases their cost, and post-processing is required to set the dyes. Choices are also reduced, as coated fabrics are limited in terms of both type and weight. Further, wide-format graphics printed directly to fabrics do not appear as sharp and their colours do not ‘pop’ as much as with transfer-based sublimation.

Reactive inks
Reactive inks involve a chemical process using a molecular dye that yields excellent washable durability and lightfastness for such applications as home furnishings. The inks can be printed onto pretreated natural-fibre textiles, such as cotton, linen, silk, rayon, hemp, viscose (wood cellulose) and bamboo.

Once printed, the fabric must be steamed and washed. The steaming process is important to cure and set the dyes in the fabric. Depending on the type of steamer used, this process will take anywhere from 10 to 20 minutes. The washing, meanwhile, is necessary to clear off any uncured ink or coating, which is especially important for bed linens and apparel.

No detergents or chemicals are needed for the washing process, just hot water and time to dry the fabric. This process will add a soft hand back to the fabric that was lost to precoating.

Acid inks
Acid inks are etched into fabrics to offer strong outdoor longevity, making them ideal for flags and banners. They are also used in swimwear.

An acid ink can be used on pretreated synthetic materials, such as nylon and spandex, as well as on pretreated natural fabrics like silk, wool, angora, alpaca and some types of leather. The same steaming and washing process used with reactive inks is required to finish fabrics printed using acid inks.

Textile pigment inks
Textile pigment inks offer excellent lightfastness and can be used on all fibres. This type of ink uses a heat fixation process and requires a resin-based carrier to bond it to the fabric. The inclusion of the resin removes pigments, resulting in less washable durability.

These inks are general-purpose formulations, more commonly used in offset and traditional analogue methods than in digital inkjet printing.

Solvent/eco-solvent inks
The most versatile inks are solvent-based or ‘eco-solvent’ variations. They are widely used for outdoor signage, durable graphics and specialty applications like transfer-based T-shirt images.

Fabrics used with these inks need a solvent-resistant coating or the oils can wick and negatively affect the base substrate. Post-print processing is not required, although some colours may appear less vibrant, requiring the addition of an overlaminate to make them ‘pop.’

Latex inks
Relative newcomers to the digital textile printing industry, latex inks are water-based and can be printed onto the surfaces of coated or uncoated non-wearable fabrics, canvas or wallpaper, among other materials. They typically require a higher level of heat fixation than with eco-solvent inks, but their advantage over dye sublimation inks is they can be printed directly onto materials that cannot be post-processed at quite as high temperatures as those of a calender heat press without risking distortion or discolouration.

Compared to some other types of inks on fabrics, latex-based prints may be more subject to wrinkling and suffer from lower scratch resistance.

UV-curable inks
Many printers today use UV light to cure (‘set’) inks onto the surface of an uncoated substrate. These inks are compatible with most closed woven fabrics, such as canvas, but some may require the addition of a primer layer to keep the ink on the top surface of the substrate to ensure proper curing.

UV inks are widely used in flatbed printers to produce signage and graphics on rigid media and in roll-to-roll printers for vinyl and other flexible media. As such, they vary in terms of flexibility. Some are too brittle for use on fabrics, but others are sufficiently flexible for soft signage applications.

Solvent UV inks
As the term implies, solvent UV inks marry the best attributes of solvent-based and UV-curable inks. The solvent component is aggressive with the accepting layer of the media, fixing the pigment to the substrate, while the subsequent UV curing both contributes to the graphics’ durability and ensures vivid colours with a smooth, glossy finish. These types of inks are best-suited for tightly woven soft signage and interior décor applications.

Opportunities in all segments
The exhibit industry has seen soft signage grow as a trend because it is light, easily rolled and packaged and less prone to damage than many rigid graphic applications. Exhibitry opportunities ranging from short trade shows to longer art shows have been met with soft signage. A six-
month exhibit, for example, might use indoor soft signage for wayfinding purposes, complementing outdoor banners for promotional purposes.

Soft signage is also increasingly popular among retailers and brand managers. Flags, wind sails, ‘dancers’ and other dynamic applications not only catch people’s attention, but also are easy to handle and less expensive to ship than rigid retail graphics. Many sign shops’ existing solvent or eco-solvent printers can produce graphics on canvas or reinforced polyamide-based fabrics for awnings and other outdoor-durable applications.

Indoors, stretch-frame fabric lightboxes are becoming increasingly popular, as they can be integrated as design elements in a retail or office environment or as part of an exhibit. Direct-to-fabric printing can produce colours that remain vibrant when backlit.

Similarly, interior décor offers many strong opportunities for sign and print shops. The environmental graphic design (EGD) sector has turned to softer materials to impart a ‘homier’ feeling for office lobbies, medical treatment areas, hotel rooms and other spaces. Wallcoverings, wallpaper, flooring, mats, curtains, upholstery, wall art and bedcoverings can all be digitally printed, using dye sublimation, reactive, textile pigment, latex, UV and/or solvent UV technologies.

Growth potential for all business types
Across the board, new opportunities have emerged for wide-format digital printing with transfer-based and direct dye sublimation, eco-solvent, latex and solvent UV inks. These opportunities are fuelled not only by the inks themselves, but also by the growing availability of specialty fabrics designed for a broad range of markets, including high fashion, performance apparel and industrial textiles. With this increasing selection of fabrics, new and emerging markets have become open to sign industry technology.

As such, rather than having to be outsourced, many soft signage and other fabric media applications can now be produced in-house, using familiar raster image processor (RIP) software and printing equipment. Further, digital technology and direct printing have made one-off and short-run fabric graphics more easily achievable, helping sign shops to expand their business and increase their profits.

Ken VanHorn is director of marketing and business development and Tommy Martin is the textile and apparel business development group manager for Mimaki USA. For more information, visit www.mimakiusa.com[5].

Source URL: https://www.signmedia.ca/wide-format-printing-ink-options-for-fabrics-soft-signage-and-interior-decor/

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