28. Mai 2011

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Know-How Toner technologies: Flowing powder

Toner powder is a laser´s ink. Although it is powder, it flows like a liquid. The complex combination of pigments and additives is the basis for the electrophotographic printing process.

Black and color toners are the most important components of the electrophotographic printing process. Toner is used by small A4 desktop lasers and huge digital printing systems, which print more than 100 pages per minute. There are large-format LED printing systems which produce prints about one meter wide much faster than inkjets. By the way, in this article we`re talking about laser printers, even if LEDs illuminate the organic photo conductor (OPC) - the Operating principle is similar (The article is available in German only).

Toner and printing technology

Laser printing, that is using toner to print, is based on electrophotographic processes. After halftoning the print data, a laser beam projects an image of the page to be printed onto an electrically charged rotating drum, coated with organic photoconductors. Photoconductivity removes charge from the areas exposed to light, where toner will stick later on. More about laser and LED printing can be read in this article: How laser printers work (The article is available in German only).

Laser printing: A laser beam or LEDs projects pictures or text on an organic photoconductors - there the toner sticks to be transferred to the paper.

Prices, market, technological development, advantages and disadvantages

Laser printers for the professional sector are usually more expensive than inkjet printer in initial cost, but running costs are usually at a lower level - so the price of a page printed with toner is usually less than for one printed with ink. In addition, laser printers need no expensive special papers, as a print on plain paper is possible. Another advantage of laser technology is the durability of the prints against UV radiation and moisture.

Laser printing systems achieve resolutions up to 2,400 dpi, such as the Xerox colour 550 / 560. They are however not very well suited for the output of color-consistent documents. This is caused by the different color modes, which are generally less extensive for lasers than for ink printers.

Comparison of technologies: High quality printing with a laser (top), printing with ink (bottom) with finer grid and larger color mode.

However, manufacturers of laser printers strive to improve the print quality. Intentions are is primarily to enhance print quality for fast, professional production printers. Their output quality can be compared more and more with offset printing. So, a lot of things are in motion - but more on that later.

Research and development in toner production is expensive. So manufacturer try to conceal their recipes, though a composition of toner is more or less alike. In addition to the color pigments they consist of resin, metal oxides, lubricants and additives of various kinds. A main component is mostly synthetic resin, which binds industrial soot.

You may want to read more on that: Proper handling of toner (The article is available in German only).

Toner powder: By shaking or by stirring the toner particles are charged electrostatically, the powder looks like a liquid.