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Xerox patents offset paper for digital printing

Thursday, 02 August 2007
By Print 21 Online Article

An invention by Bruce Katz, a Xerox paper technologist, means digital printers no longer need paper made through a chemical pulping process. The new Xerox High Yield Business Paper is made the same way as mechanical offset substrates and is being promoted as having less environmental impact than other digital papers.

The breakthrough technology ends two decades of differentiation between offset and digital printing. When Xerox first experimented with mechanical paper, its printers and copiers would not run reliably using the paper. There were two problems – the mechanical paper resulted in excessive dust contamination, and the heat necessary to fuse an image to the paper caused it to curl.

Xerox recognized that the lighter but bulkier mechanical paper had attractive attributes, as opposed to the chemical pulping process substrates it was forced back on. So Xerox scientists went back to the paper lab to see if they could make mechanical paper work in their products.

The problem that Xerox aimed to solve was keeping the paper from curling. That happened because paper actually expands or shrinks as it absorbs or releases moisture. The printer’s fuser acts like a hot iron, fixing the image on the page and forcing moisture out of the paper. The mechanical paper curled, according to Katz, because the “back” and the “front” of the paper shrank at different rates.

In the Xerox media lab, scientists discovered the fibres were aligned in different patterns on each side of paper, resulting in uneven shrinkage. Working with an American paper mill and employing statistical techniques, Katz developed a process that better distributed the fibres on both sides of the paper, reducing the curl so that the paper could run successfully in Xerox copiers and printers.

Xerox has applied for a patent on the process. A surface treatment at the paper mill minimizes the paper dust, which had also caused operational problems.

The new process yields up to double the amount of paper from wood chips. In a chemical pulping process, paper mills separate wood fibres in a water-and-chemical solution, then recover the cellulose, which comprises about 45 percent of the wood, to make paper. Leftover wood chemicals are burned for energy to run the process.

Because the new paper is lighter in weight than paper made by the traditional chemical process, it costs less to ship and mail. It is the first and only paper of its kind that performs reliably in digital printers and copiers.

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