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A dry film makes a very hot photo debut.

A photographic film that doesn't need silver or developing chemicals may soon appear in commercial print shops.

Called VerdeFilm by its developer, Xerox Corp., the new film replaces silver halide with a selenium-based compound that reacts to light only when the film is under an electric charge. The new product's chief advantage, the company says, is that it eliminates the multistage chemical processing required by most conventional photographic films.

"This is a dry process," says Edward H. Ernst, general manager of Verde Print Technologies, a Xerox division. "No wet chemicals or effluents are added to or taken away from the film."

The process is based on electrophotography, Ernst says. The film consists of a sheet of aluminized mylar with a 1-micrometer-thick layer of a heat-sensitive polymer. Embedded in the polymer are selenium particles. Unaffected by light in its resting state, the film becomes photosensitive only when subjected to an electrical charge. Then, when exposed to light and gently heated, the film reveals an image--a process akin to that used in laser printing.

"By putting the film in an electric field and exposing it to light, the film's photo-conducting particles become charged," Ernst says. "When you heat the film, the charged particles migrate toward the back of the film, toward the aluminized mylar, which acts as an electrode. Finally, when the film cools, the particles stay fixed in their new positions, leaving a permanent image."

Casual exposure to light doesn't wreck the film -- another advantage. "Loading this film is like dropping paper into a laser printer," says Ernst.

In its current form. VerdeFilm will prove most useful for high-resolution black-and-white "intermediate master images," used by industrial printers to make magazines, catalogs, and posters. Xerox reports no plans to market a color VerdeFilm or consumer version.

The name VerdeFilm implies a "green," or environmentally friendly, technology, says Xerox spokesman John Rasor, in line with the company's goal of reducing the hazardous effluents common to silver-halide photography. California has classified the new film as "casually disposable," Xerox reports, with selenium leakage below detection levels. The company also plans to recycle exposed film, removing the selenium for reuse.
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Title Annotation:Xerox Corp's VerdeFilm photographic film does not require multistage chemical processing
Author:Lipkin, Richard
Publication:Science News
Article Type:Brief Article
Date:Nov 6, 1993
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