Toner

Toner is a powder used in laser printers and to form the printed text and images on the paper, in general with a toner cartridge. In its early form it was a mix of carbon powder and iron oxide. Then, to improve the quality of the printout, the carbon was melt-mixed with a polymer. Toner particles are melted by the heat of the fuser, and are thus bonded to the paper.

In earlier photocopiers, this low-cost carbon toner was poured by the user from a bottle into a reservoir in the machine. Later copiers, and laser printers from the first 1984 Hewlett-Packard LaserJet, feed directly from a sealed toner cartridge.

Laser toner cartridges for use in color copiers and printers come in sets of cyan, magenta, yellow and black (CMYK), allowing a very large color gamut to be generated by mixing.

The specific polymer used varies by manufacturer but can be a styrene acrylate copolymer, a polyester resin, a styrene butadiene copolymer, or a few other special polymers. Toner formulations vary from manufacturer to manufacturer and even from machine to machine. Typically formulation, granule size and melting point vary the most.

Originally, the particle size of toner averaged 14–16 micrometres or greater. To improve image resolution, particle size was reduced, eventually reaching about 8–10 micrometers for 600 dots per inch resolution. Further reductions in particle size producing further improvements in resolution are being developed through the application of new technologies such as Emulsion-Aggregation. Toner manufacturers maintain a quality control standard for particle size distribution in order to produce a powder suitable for use in their printers.

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