Is it possible to use UV-LED ink to do t-shirt print?
To print a process color image on a T-shirt today, most printers use pigmented water-based inkjet inks, or they use dye-sublimation inks for direct- or transfer-printing. The former can be used for cotton and cotton blends but the latter can only be used on synthetics. Both may require pretreatments to hold out the ink and to control color bleed.
UV-LED inks could provide a desirable alternative. It would not depend on fabric type and should provide very good wash-fastness and rub-fastness. Aside from the safety concerns, typical UV-LED inks do not stretch sufficiently to meet the needs of apparel applications.
However, at a recent trade show I saw a UV-LED T-shirt printer for the first time. The printer manufacturer sourced the inks, which when cured, can stretch with the fabric, even fabric with spandex. So, what about UV curing and any potential bad actors that may remain?
UV-LED Fabric Printing
UV inks are very low in viscosity when printed and will penetrate the fabric. To receive curing radiation from the UV-LED lamp the ink must be exposed directly to the UV light. To adhere to the fabric the inks must penetrate deep into the fabric's surface.
It's possible that some of the ink could be shielded from direct UV light exposure by the overlapping fibers of the fabric. Without full UV light exposure, the reactive chemicals (monomers and oligomers) remain reactive and thus could pose an irritation threat to the person wearing the garment.
I posed this concern to the folks selling the printer at the trade show where I first saw it, and they recommend a post-print heat treatment in a heat press to insure complete reaction of the ink. They indicated that their inks, in finished T-shirts after heat treatment, passed a CPSIA (Consumer Product Safety Improvement Act) textile compliance test for skin irritation. That sounds great.
I consulted with a supplier of UV-curing ink ingredients and asked if this claim was reasonable. Not knowing the formulation or the test procedure he could not render a judgement. He did mention that other ingredients that are normally added to UV inks for stabilizing the ink would remain and that the heat in a heat press may not be sufficient to cause a reaction for monomers remaining in the ink.
After contacting the printer manufacturer, I learned that the ink formula—in addition to containing the typical light-sensitive photo initiators that trigger the curing reaction when exposed to UV light—also includes heat-sensitive thermal initiators that further trigger the reaction when exposed to heat from the heat press. This would cure any inks that did not get exposed to the UV light and eliminate the possibility of un-cured ink hiding in the fibers.
Company Name: Fei Yue Digital Technology Co.,LTD
Whatsapp: +86 18252072197
Address: Central Road 323, Nanjing, Jiangsu, China