Wide-format Printing: Selecting fabrics for backlit graphics

Photos courtesy TVF

By Mike Compton
Many print service providers (PSPs) are working with fabrics today for backlit graphics, while others are still seeking to learn about and enter this high-growth market. Mainstream applications include trade-show booths, museum exhibits, point-of-purchase (POP) retail displays, interior decor, storefronts, curved architectural structures, sports venue banners, airport ads and ceiling displays, among many others.

At the same time, there are many fabrics to choose from, with different weights and construction characteristics suitable for different applications.

Knitted vs. woven
One of the most basic choices is between knitted and woven fabrics.

Knitted fabrics typically offer better stretch characteristics for the frame systems for backlit graphics. They can even be easily used with curved frame structures. One of the advantages of their stretch capabilities is ensuring dimensional stability, as the stretching of printed graphics should be as uniform as possible.

Densely knitted fabrics provide stronger opacity for the diffusion of light-emitting diode (LED) illumination. Lock stitch construction prevents the accidental tearing of finished graphics and allows them to be cold-cut, rather than hot-knifed.

Woven fabrics can also be used for backlit graphic applications, depending on the density of the weave and, again, opacity and stretch capacity. They are best-suited for flat display frame structures, as they offer less stretching for curved frames.

These fabrics feature loose-end weave construction, so they require hot-knifing to seal their edges to prevent fraying. Depending on their precise type of weave, they may reveal ‘hot spots’ from LED illumination, particularly when finished images are viewed from an angle.

Both knitted and woven fabrics for backlit graphics range in weight from 113 to 312 g (4 to 11 oz) per 0.8 m2 (1 sq yd).

Coated vs. uncoated
Today’s premium fabrics that have been manufactured with backlit graphic applications in mind feature print-receptive diffuser coatings. By dispersing the light from the LEDs, these coatings help provide even illumination across the finished images.

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Coatings prevent the aforementioned hot spots, which can be an issue with uncoated fabrics, and also eliminate ‘pinholes,’ where light could show through an open weave or knit and distract from the printed image’s quality. A properly coated fabric eliminates the need for an additional diffuser panel behind the graphic.

Coated fabrics are also recommended because they can be printed with a variety of inkjet technologies, including heat-transfer and direct dye sublimation, durable aqueous ‘latex’ and ultraviolet-curing (UV-curing) printers.

Extra attention may be needed when printing and handling coated fabrics, but the efforts pay off by yielding brilliant backlit graphics upon completion.

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