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Paper: The Digital Difference

The idea of a paperless society was advanced more than 30 years ago, but even in this age of Kindles and Nooks and iPads it remains just that—an idea. Paper has yet to disappear even as electronic media grab larger and larger shares of the communications cycle. That said, the same digital...


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The idea of a paperless society was advanced more than 30 years ago, but even in this age of Kindles and Nooks and iPads it remains just that—an idea. Paper has yet to disappear even as electronic media grab larger and larger shares of the communications cycle. That said, the same digital technology that has enabled this electronic communications also has driven more printed communications from offset output to digital production.

"Our paper sales for color digital print applications, such as production inkjet, are growing exponentially as we continue to build strong business relationships around technical problem solving in the pressroom," said  Tony McDowell, VP Sales and Marketing, Finch Paper. “We plan to continue to re-align our sales and technical resources as customers shift from lithography to digital print output."

There are basically three ways to put marks on paper—analog offset, digital toner, and digital inkjet. Offset produces a static printed piece and, while capable of high-end color quality, is most economical with longer press runs. As this technology gives way to digital output, both printed and electronic, paper volumes used for offset will continue to decline. This leaves digital as the only potential growth area for paper. In fact, paper for digital presses is now the fastest growing category in paper manufacturing.

Toner vs. Inkjet

For commercial production printers, digital output can be divided into two categories—inkjet and toner. Each presents its own set of considerations when it comes to paper selection. Currently, toner is far and away the leading digital output technology in the commercial printing industry. However, developments in inkjet are allowing that output technology to make inroads, particularly in the areas of transpromo, direct mail, and book production. (Inkjet is also a major player in the wide-format arena, which can involve substrates other than paper.)

Inkjet production presses are available now from major vendors such as Océ, HP, Kodak, and Xerox. Papers for use in those devices must be adapted to the characteristics of inkjet printing. With high water content, inkjet inks tend to soak into uncoated papers or sit on top of coated stock. Paper manufacturers have worked with inkjet vendors to formulate papers that address these drawbacks. As inkjet devices become more common, the variety of both coated and uncoated inkjet-compatible papers is increasing.

According to Frank Edmonds, Senior Vice President, Global Paper and Supplies Distribution Group, Xerox Corporation, “Inkjet papers are custom designed for inkjet applications, particularly full color applications. They are surface-treated to ensure good text definition, low color mottle (non-uniformity in the image color), and minimal feathering. The surface treatment also acts as a barrier to control ink drop penetration. This maximizes the brightness of the colors. It also enhances the sheet's smoothness, which affects image quality as well.”

Among the players in the inkjet digital paper arena is Appleton Coated, which offers an inkjet coated paper. According to Ann Whalen, Appleton's senior vice president of marketing and customer services, "In 2011, we firmly established Utopia Book Inkjet as a premier coated product for the new high-speed web inkjet platforms emerging in the publishing industry, and are now developing dull and gloss coated Utopia Inkjet products for the expected growth in commercial print and direct mail applications."

Toner-based devices present an entirely different challenge when it comes to selecting the most suitable papers. Since this remains the dominant digital output technology for commercial printers it deserves a more detailed look into the necessary characteristics of paper for use in toner-based output devices.

Electrophotographic Printing

Today’s toner-based electrophotographic printers have come a long way since their introduction into the commercial printing industry in the 1970s. With production-speed output and outstanding color quality, these presses have become the workhorses for commercial digital printers. Nonetheless, toner-based technology still has its own set of drawbacks and considerations when it comes to paper selection.

In any printing environment, there are three basic considerations for paper:

  1. Runnability, the ability to run through the output device smoothly
  2. Printability, the quality and look of the printed piece
  3. Usability, the characteristics needed for proper finishing and distribution

Toner-based output devices add other demands on paper due mostly to two steps in the electrophotographic process—toner transfer and fusing.

Toner transfer is accomplished by placing a charge on the paper prior to it reaching the photoreceptor. The efficiency of the process depends on the characteristics of the paper, including thickness and moisture content. Where there are variations, toner may not adhere correctly causing toner specks or ghosting.

Once the toner image is placed on the paper it must be fused. Here again, the efficiency of toner fusing depends on the characteristics of the paper. While most toner-based digital presses such as those from Xerox, Konica Minolta, Ricoh, Kodak, Xeikon, etc. use dry toner that is fused with heat and pressure, the HP Indigo press uses Electroink, which is fused at lower temperatures and pressures. Digital papers are certified separately for dry and liquid toner use.

Paper Characteristics

Moisture level is one of the more important considerations in digital printing paper use. Too dry and there can be static and paper jams. Too moist and paper can curl and cause jams. Moisture levels not only are dependent on how the paper is milled, but also on how it has been stored.

Full-color digital printing, with heavier toner coverage and higher fuser temperatures, calls for more stringent paper quality control to prevent jams in the complex paper paths. Important characteristics are surface properties, surface strength, dimensional stability, grain direction, smoothness, and charging characteristics.

Also important is paper opacity because heavier toner coverage can lead to images showing through on two-sided digital print jobs. “The demands of color laser printers are different than those of black and white printers,” said Edmonds. “When you use color, you subject the paper to four layers of toner. With black and white printing, only one layer of toner is applied. For this reason, high-quality color printing papers have a different set of product specifications.”

According to Chris Harrold, Vice President, Business Development, Digital Media, Mohawk Fine Papers, “The same characteristics that make a great offset paper apply to digital paper: formation, smoothness, brightness, and opacity. All four of these qualities play a role in superior print results and shouldn’t be overlooked. In addition, digital papers are made to specific calipers, contain less moisture, and are precision-cut to digital sheet sizes/rolls. Digital papers may also have a product-specific surface treatment for toner and inkjet applications.”

Sources

With the growing importance of digital printing, the available variety of papers specifically formulated to meet digital printing demands is steadily increasing. Digital papers rated and approved for the various toner and inkjet digital presses are available from most paper manufacturers and distributors and from the makers of the digital output devices. For a listing of sources, see the vendors listed under Consumables & Suppliers, Paper, Digital Print Media at: www.MyPrintResource.com.

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