Machine Design

Nanoball toner to shrink color printers

Electrostatic adhesion force makes toner particles in photo-copiers, laser printers, and fax machines, temporarily stick to paper before they are permanently fused by heat.

The detailed physics of electrostatic adhesion forces are unknown. Experiments show these forces to be at least a factor of ten stronger than what Gauss' Law predicts. Gauss' equations quantify electrostatic attraction between two bodies, but assume a large distance between the bodies compared with distances between charges. In practice, contact points can be extremely small; electrostatic forces are strongest where discrete charges lie close to these contact points, explain researchers at the recent AVS International Symposium and Exhibition in San Francisco.

This has important implications for color laser printers, which use black, cyan, magenta, and yellow toners to create four separate images before transferring them onto paper. Today's color printers use a separate belt to accumulate toner images one color at a time. This adds weight, complexity, and cost.

Lower-adhesion toner would make it possible to build each color image onto a single belt without disturbing the other colors. To lessen adhesion, researchers mixed the toner particles with 10-nm-diameter silica nanoballs. The nanoballs prevent a particle's rough edges from touching surfaces, minimizing the number of contact points and adhesion. The advance could lead to single-belt color laser printers that are 70% smaller and much cheaper to build than current models.

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