Sign & Digital Graphics

June '17

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S I G N & D I G I T A L G R A P H I C S • June 2017 • 63 substrates that might otherwise curl or buckle under hot lights. However, the UV-curable inks in both systems are similar and must be treated with respect. As liquids, UV-curable inks are quite hazardous and require careful handling to avoid skin contact. Once the inks are cured they provide a relatively safe and durable image. Adhesion of the ink to the substrate—like all ink technologies— requires some optimization. On porous substrates, especially fabrics, the ink may soak into the surface prior to curing. The UV light must directly contact the ink to achieve curing. If beneath the surface and shielded from the UV light by a paper or fabric fiber the cure may be incomplete. On nonporous surfaces there needs to be proper wetting by the ink and a surface that can bond to the ink when cured. Sometimes a treatment or coating may be required to get optimum perfor- mance. There are a range of substrates available that have been optimized for UV printing. The newest UV-curable ink set to come online is called UVgel, a unique formula developed for Canon USA's new Oce Colorado 1640 printer. The unique gel properties of this ink reduce dot gain and offer other advantages. Although it's too soon to report on how it performs in the field, UV-cure ink safety precautions will certainly still apply. Conclusions With all of these choices—and we didn't even discuss dye-sub inks for fab- ric printing—my best advice is that once you determine the printing applications that you anticipate, test each printer/ink system to determine which best meets your needs. Testing such as this can often be done through printer dealers and dis- tributors. Clearly the ink cost, printer speed and image quality, media cost and availability and final performance of the product you produce all need to be considered. The good news is that you do have a number of viable choices. The decision may not be easy; however, inkjet ink technology has come a long way and can provide great results for a wide variety of applications. SDG A few years ago, strong hot solvents were often used in printers designed for grand-format out- door printing, as with the 2008 HP Scitex XL1200 printer shown here. Les toxic ink sets are avail- able today. (Image courtesy of HP Scitex)

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