Continuous-feed Inkjet : The Web Paper ChallengeSeptember 2012 By Jack Miller
hile the market for print has been in decline since 2000, digital printing has continued to grow at double-digit rates, and the new generation of continuous-feed inkjet presses promises to accelerate this growth. At drupa 2012, we saw a host of new entrants, as well as upgrades from the earlier entrants: one drupa visitor reported seeing 18 different inkjet engines. As Figure 1 shows, the speed and productivity of inkjet presses has grown, and inkjet printing has grown apace.
Printers face a number of tradeoffs in selecting presses, ink and paper for production inkjet. This article will explore the challenges and solutions relating to paper in key applications, including transactional and transpromo, book, direct mail and general commercial printing.
Inkjet inks can be dye-based or pigment-based. In general, pigment inks are more expensive and higher quality, while dye-based inks still produce good color, but colors may be slightly less brilliant and less permanent. Dye-based inks are good for transactional and some direct mail applications, while pigment inks are better for some book applications and general commercial printing where ink coverage is high with four colors.
Water In, Water Out
Both types of inks contain a lot of water, and the water creates a challenge. Dennis Essary, director of digital papers for NewPage Corp., explains: "The water has to go in and leave pigment on the surface, and then the water has to be driven out by heat. This requires a surface that looks smooth, but is actually quite open." This is especially challenging for coated papers, and more so for glossy papers, where coatings are smooth and appear to create a continuous, closed surface.