One of the newest and hottest trends within the decorated apparel industry is direct-to-film (DTF) printing, a transfer technology that enables users to print designs onto polyethylene terephthalate (PET) film using water-based pigment inks. Since this is a transfer technology, the design is printed in reverse order in relation to traditional digital printing. The image is reversed so that its orientation is mirrored—the CMYK colors (i.e., cyan, magenta, yellow, black) are printed first, followed by the white ink. The wet ink is powdered with a hot-melt adhesive and then cured. Once cured, the image can be transferred to apparel using a heat press.
When compared to direct-to-garment (DTG) printing, DTF offers the ability to avoid fabric pre-treatment, which is often required when printing with DTG. DTF will also work on fabrics like polyester and nylon, which are often difficult (if not impossible) for DTG. In addition, there’s a much lower learning curve for printing DTF transfers compared to DTG. When compared with dye-sublimation, DTF enables the user to decorate a wider range of fabrics and fabric colors. DTF is also more efficient than other transfer technologies like heat-transfer vinyl because there is no cutting and weeding with DTF, which saves time.
As with other digital print technologies, DTF is great for full-color, photorealistic images. The possible range of color is limited only by the gamut of inks being used. Fine lines, small text, and high detail images are no problem for DTF. All this being said, color profiling can be a challenge for those who are unfamiliar with color management and ICC profiles. Special RIP software is also required to create a white print layer and to mirror the image so the transfer prints in the correct orientation.
To date, the majority of DTF printers have originated from China. They are often modified Epson printers or platforms using Epson printheads (models commonly include 1–4 printheads). Optional configurations include additional printheads to jet added white, CMYK, or fluorescent channels. Print speeds will vary based on the number of printheads. At the same time, however, the available printer models fall within one of three categories:
Slow (25–35 sq. ft./hr.)
Medium (80–100 sq. ft./hr.)
Fast (150+ sq. ft./hr.)
Costs per square foot (including PET film, ink, and powder adhesive) range between $0.50 and $0.90. The reported washfast durability is above 100 laundry cycles.
While preparing the image for print is particularly important, applying the hot-melt adhesive is equally so with DTF; it uses a hot-melt powder made of polyurethane resin ground into adhesive powder. While there are no harmful emissions, the powder adhesive is exceptionally fine and can generate dust, so it’s important to wear respiratory protection when working with the powder. It’s also best to keep the inkjet printer at a safe distance from the powder coating process to keep adhesive dust from penetrating the sensitive parts inside the printer.
The powder itself comes in white and black, depending on the general color of the fabric that is going to be decorated. The powder is best applied using an automatic powder shaker for rolls of printed PET film, but it can also be manually applied when using cut sheets of PET film. The biggest factor associated with applying the powder adhesive is achieving a consistent, even coating. Once cured, the transfer is applied at 315°F (157°C) for 15 seconds at medium pressure for cotton fabrics. For heat-sensitive fabrics like polyester, the press time can be reduced.
The PO-TRY DTF printers represents the newest offerings in the industry, and these devices require no powder adhesive. With this system, the transfer adhesive prints at the same time as the white ink pass, eliminating the powdered adhesive process as well as the dust it can generate. This new approach represents an emerging trend in inkjet printing whereby chemistry is being jetted in addition to CMYKW inks.