Xerox develops invisible ink

New toner fluoresces under ultraviolet light.

Xerox has developed an invisible ink that fluoresces under ultraviolet light and can be used by most commercial printers.

The technique was developed by Reiner Eschbach, a research fellow in the Xerox Innovation Group, and principal colour scientist Raja Bala.

A special combination of toners creates the effect by using inks that react with the fluorescent agents paper manufacturers use to make their paper seem brighter.

"What amazes people about the new technology is that we can create fluorescent writing on a digital printer without using fluorescent ink," said Eschbach.

"That means a four-colour digital printer can print everything it normally would, and can simultaneously individualise a document with a fluorescent identifier."

Most high-denomination banknotes have some kind of fluorescent colouring, but this is the first time that businesses can use the technology at relatively low cost.

"Just as US currency has a fluorescent thread to authenticate it, I can imagine a time when your cheques will have your signature printed in an [invisible] fluorescent strip," said Eschbach.

"A merchant could easily compare the fluorescent signature with the actual one to validate the cheque."

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