A sharper image

On a computer screen, smaller pixels produce sharper pictures. It's the same with the toner that's used to form the images printed on a laser printer or copier: Smaller particles mean sharper images - plus lower cost per print.

But as toner particles become smaller, the cost of making them by current technology rises exponentially. Several years ago, Xerox researchers realised that toner made by their current technology had just about reached the lower limit in size, and they started looking for a new way to make it.

Toner is the 'dry ink' for laser printers and copiers. It's a mixture of plastic resin, colorant and other toner ingredients. Today, most toner is made by 'melt mixing' the ingredients into strands that are pulverised into small particles - a process that's both inexact and energy intensive.

Because the particles are smashed at random, their size cannot be precisely controlled. Some are too big and others too fine, so they are mechanically sorted to achieve required toner size and size distribution. It's like sifting dust. This method produces toner with average size greater than 7 microns in diameter; making it smaller is not economically practical.

To help out, materials scientists at Xerox Research Centre in Canada, under the direction of Hadi Mahabadi, have now developed a chemical approach to economically creating even smaller toner particles.

They started at the molecular level and perfected a way to grow toner particles under controlled conditions to exactly the size, shape and structure needed. They can now make round or potato-shaped toner particles of about 3-5 microns in diameter.

These toner particles produce prints with sharper images, plus the resulting prints use less toner and therefore cost less. Prints using a 5-micron toner require 40% less toner than those made by a 9-micron toner.

The new process, called emulsion aggregation or EA for short, turns out to have added benefits. It will require less energy to make, generate less waste, contribute to printer reliability, and cut the time it takes for printers to recover from energy-saving sleep modes.

It will be unveiled in new Xerox colour products later in the year.