31 January 2014

Digital prints on fabrics...

Digital prints on fabrics...

Digital textile printing is described as any ink jet based method of printing colorants onto fabric. Most notably, digital textile printing is referred to when identifying either printing smaller designs onto garments and printing larger designs onto large format rolls of textile. Examples are: flags, banners and signs.
Digital textile printing can be divided into:
·         Direct to garment
·         Visual communication
·         Interior decoration
Digital textile printing started in the late 1980s as a possible replacement for analog screen printing. With the development of a dye-sublimation printer in the early 1990s, it became possible to print with low energy sublimation inks and high energy disperse direct inks directly onto textile media, as opposed to print dye-sublimation inks on a transfer paper and, in a separate process using a heat press, transfer it to the fabric.

The ‘textile market’ comprises many different applications and requirements. The intended use of the fabric is the most important starting point to identify exactly what’s needed to produce a specific end-product. A ‘textile’ product may vary from natural yarns for garments, through to synthetic fibres for flags and banners. A ‘textile product’ can be a wall mounted banner, a stand-alone pop-up banner, a beach flag, country flag or company flag. It can be a carpet, back-lit frame, curtain, room divider, building wrap, bed cover, a garment and much more. The predominant textile media used in visual communication is a polyester based fabric. In the USA, nylon is often used for flags. In northern Europe, polyspun material has been the choice of fabric for traditional flag printing. In today’s market, a woven or knitted polyester is the de facto standard. This differs from the predominant coated vinyl or pvc media used in the sign and display industry. The production process needs to fit requirements for the type of ink: high energy sublimation (also known as disperse direct), low energy sublimation , acid, reactive and pigment. In turn, the type of ink chemistry needs to fit requirements for the media (such as polyester, nylon, cotton, silk). Based on the media and ink combination, the choice comes for infra-red fixation, heat-press sublimation or steaming. The structure of the fabric also needs attention, for example whether it is woven, non-woven or knitted.
Polyester fabric is printed mostly with dye-sub or disperse direct ink, although UV and solvent inks can also be used. The great benefit of sublimation ink is the fact that the colorants will bond with the fibre during sublimation or fixation. The colours are ‘inside’ the media and don’t stay within the coating and on top of the media, as it is the case with UV-curable formulations. Even latex inks on porous textiles can suffer from abrasion or ‘rub-off’. Low energy sublimation ink is easier to print with, but has the disadvantage of colours fading faster; its UV resistance, or light-fastness, is less resistant than equivalents using high energy disperse direct ink. Dye-sub can also suffer from a ‘halo’ effect which results in less sharp images. The disperse direct ink is a ‘stronger’ ink than the dye-sub kind, and this is very important for outdoor use, such as for fence fabric, flags and banners: artwork will last longer.