Why disappearing ink isn't just for spies

The fact that 21 percent of black-and-white copier documents are returned to the recycling bin on the same day they are produced has inspired some tech companies to investigate alternatives

According to Brinda Dalal, an anthropologist at Xerox's Palo Alto Research Center (PARC), of the 1,200 pages of printed information the average office worker prints per month, 44.5 percent are for daily use, such as assignments, drafts or emails.

The problem is that, in most offices, paper is commonly used as a medium of display rather than storage or transfer. Dalal discovered that 21 percent of black-and- white copier documents are returned to the recycling bin on the same day they are produced.

In most companies, documents are created and transferred between individuals digitally, and then stored either on central servers or personal computers. They are only printed out or copied when needed for meetings, editing and annotating, or reading away from a computer, all of which imply a fairly transient use for the printed document.

The result is, of course, an enormous quantity of waste paper, paper that is not only increasingly expensive to buy, but that involves the use of a considerable amount of natural resources, in particular energy.

It takes about 202,000 Joules to manufacture one sheet of virgin paper. Recycling that sheet takes a further 114,000 Joules. When you consider that, this year alone, about 2.5 trillion pages will be printed worldwide, it is clear that the production and recycling of paper represents an enormous amount of energy usage; not to mention the cutting down of a few forests.

Xerox transient paper technology
Xerox is just one of the companies investigating how to use paper more efficiently. The company believes the solution to this environmental problem is to reuse the paper.

Reusable paper is, of course, hardly a new idea. Medieval monks reused velum manuscripts by scraping off the top layer containing the ink from the original document to create a clean surface suitable for writing a new document — known as palimpsests.

The idea of scraping off the top layer to expose a clean new surface for writing has been adapted to paper. Right up until 2005 it was possible in the US to buy a reusable paper called Eaton's Corrasable Bond, which had a glazed surface that could be removed by friction.

However, such techniques are hardly suitable in an era of photocopiers and computer printers. In response to Brinda Dalal's research on paper usage in offices, the solution developed by Xerox's researchers at Palo Alto and Xerox Research Centre of Canada labs over the past three years is an office copier/printer system that creates paper-based transient documents where the printed information simply disappears within about 16 hours, allowing the paper to be reused.

"Despite our reliance on computers to share and process information, there is still a strong dependence on the printed page for reading and absorbing content. Of course, we'd all like to use less paper, but we know from talking with customers that many people still prefer to work with information on paper. Self-erasing documents for short-term use offers the best of both worlds," says Paul Smith, manager of Xerox Canada Research Centre's new materials design and synthesis lab.

In fact, the self-erasing concept itself  is not entirely new. In the 1990s, Japanese office-equipment maker Ricoh developed a commercial system that removed toner from paper in order to make it possible to recycle individual sheets up to 10 times. However, this system failed commercially and is no longer available.

In 2003 Toshiba also developed and marketed a system using a special blue, decolourable ink that disappeared when the paper was heated in a special eraser box. However, the high price of the erasing system and the paper and the toner, coupled with the time and effort required to erase documents has meant that this product has rarely been seen outside Japan.

Xerox has yet to make a decision to go to market with its technology. "This will remain a research project for some time," said Eric Shrader, Xerox PARC area manager, industrial inkjet systems. "Our experiments prove that it can be done, and that is the first step, but not the only one, to developing a system that is commercially viable."

However, the Xerox system's developers do believe that their technique solves most of the major commercial limitations that earlier developers such as Toshiba and Ricoh encountered. Its first advantage is that it requires no special eraser system — the print simply disappears after 16 hours. Second, no special toner...

...is required. Third, paper is used, unlike the Toshiba system which uses sheets of PET — the type of plastic used in drinks bottles — and costs over $5 per sheet. Sheets of special coated paper for the Xerox system will cost little more than an ordinary sheet of paper.

In environmental terms this is a very attractive concept. Not only does the technique use no toner, itself a source of pollution in the office, but re-imaging a sheet of Xerox erasable paper takes only about 200 Joules, so every re-use can save an enormous amount of energy. With 30 to 100 re-uses per sheet, this represents a very large saving in energy.

The Xerox erasable paper, or "transient paper" as the company prefers to call it, is simply an ordinary sheet of printer paper that is coated with a thin layer of a special chemical that changes from transparent to black when exposed to light of a certain frequency. This paper is not only cheap to produce, but it can also be pre-printed with coloured letter-headings, logos and so on. 

So the Xerox transient paper looks and feels like an ordinary sheet of photocopied or laser printed paper, although the print is more grey than black. The difference, of course, is that the print will completely disappear within 16 to 20 hours of printing, leaving just the original blank sheet of paper that can then be re-used to print another document.

"Transient paper has added security uses. You can imagine that even if you had left your document out in the open in the office, by mistake, then by the next day there'd be nothing on it, so if you had left sensitive data lying about you'd know it wouldn't be there by morning," says Xerox's Paul Smith.

Printing transient documents will require a special printer, and Xerox has developed and demonstrated prototype units that incorporate a special optical print head, which can deliver the pixel-sized dots of light needed to print an image.

Another useful feature of the printer/copier mechanism is that it can be used to erase text. Rather than waiting for the print on a page to disappear naturally, the page can be fed back into the machine where it will be erased and made available for immediate use. More impressively, the system can be used to erase and correct a specific typo on a page, a great feature if you have ever printed out 100 copies of a document and then noticed a serious mistake.

According to Paul Smith, the researchers have considered people's need  to annotate documents and have produced a special pen with a light head that will allow hand-written notes to be created on any sheet of transient paper. These notes, like the printed text being annotated, will disappear after 16 hours.

Has transient paper arrived too late?
Xerox is at pains to point out that its transient paper technology is not yet commercially available, and no decision has been made as to when it will be marketed, if at all.

Indeed, some industry analysts believe that given the rapid development of flexible e-paper display technologies, the Xerox product is 10 years too late, and will be obsolete before it comes to market.

Electronic alternatives to traditional paper and printer technology are already under development, such as document reader devices.

These devices will use an electrophoretic display technology developed by E-Ink that generates a high-contrast image that, like paper, is readable in ambient light conditions. With a resolution of 170dpi, such electrophoretic e-paper displays offer a reading experience that is not dissimilar to reading conventional newsprint and, unlike the LCD displays used in laptops, will not require the use of a backlight.

Early generations of reader devices using rigid electrophoretic e-paper displays are now in production, the best known is probably the Sony PRS-500, which is currently available only in the US and Japan. Another well-known device is the Iliad Reader from Irex Technologies of the Netherlands.

Irex Technologies is already targeting paper replacement as an application for their reader, and to facilitate this it has incorporated a PDF viewer into the device, which allows the display of any PDF document downloaded into it. The device even incorporates a wireless stylus that allows the user to annotate documents.

Using the Iliad's USB docking connector, it is possible to quickly and easily download several thousand PDF pages from a PC to the reader. Once stored...

...in the reader's flash memory, they can be accessed and read whenever necessary on this lightweight portable reader.

With a screen resolution of 1,024x768 (in a portrait orientation) on a eight-inch display, standard A4 documents are much reduced in size, and small print can be very hard to visually resolve.

But technology developments mean that this current e-paper display-size limitation will disappear within the next couple of years, as devices emerge with A4-sized flexible displays. When this happens, the paper-replacement application for such devices should take off rapidly, as people start to see these devices as a viable alternative to the printer/copier and the paper document for portable offline document reading.

Is there a future for transient paper?
E-paper-based display devices will undoubtedly have a big impact on the use of printed paper publications and documents. 

A number of large newspapers around the world, such as Les Echos in Paris, are examining the use of such readers as way of delivering digital editions to their readers. Meanwhile, book publishers such as Random House and Harper Collins are digitising their entire list so that they are ready to take advantage of the arrival of e-paper based readers.

If e-paper-based readers become widely used to read digital publications, they will undoubtedly also be used to read corporate and private documents that would today be printed on a laser or ink jet. Indeed, many analysts are predicting that sales of printers and copiers will have dropped considerably by 2020, with e-paper-based readers being widely used as printer-replacement devices.

So where does this leave Xerox with their transient paper? The answer is not necessarily as an environmentally friendly printing technology — e-paper readers are probably much better — but as an important contributor to a small but very important niche: information security.

While it is possible to encrypt digital files and lock them away in password-protected systems, they become vulnerable to theft once they are printed out. Someone may forgetfully leave a copy lying on a desk, or fail to shred it, throwing it in the bin instead. In such cases, the document is vulnerable to being viewed by unauthorised individuals both inside and outside the company.

The photocopier has long been seen as a weak point in corporate security. It is all too easy for a disaffected employee to take unauthorised copies of confidential documents. By using only transient paper copiers in a company, the utility of photocopiers is retained, while the security risk is greatly reduced.

The time limit of sensitive data printed on transient paper, whereby the contents disappears 16 hours after it is printed, is long enough for data to be used in meetings yet short enough to prevent it accidentally turning up on a waste dump, or worse still on the desk of a competitor or an inquisitive journalist.

It seems Xerox is still looking for a market for their transient paper technology, and it is emphatic that it has yet to make a decision as to whether it will become a commercial product. Its future may lie not in being the green paper product researchers first envisaged, but in offering companies a degree of security they have long sought.