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  • Thermal Lasers May Upset Offset Printing

Photonics Spectra
Jan 2001
Dan Drollette

BEDFORD, Mass. -- A printing press is the single largest capital investment of a newspaper or a printing house, and press time is precious. The owner loses money every minute that the press is down, such as when the aluminum printing plates are replaced to make way for a new run. And replacing plates can take anywhere from 20 minutes to an hour.

Researchers at CreoScitex may have a way to cut downtime to seven minutes, said Mark Sullivan, business development director. Their solution: plateless digital printing. Using this system, press operators can eliminate several steps in offset printing, one of the most popular ways of printing newspapers, magazines, catalogs, sales sheets and brochures.

Offset printing is based on the fact that oil and water don't mix. Typically, the process begins when a negative of a page is placed on an aluminum plate, which is flooded with light, etched, put on press cylinders and inked. Because oil-based ink sticks to oily image areas and water repels ink from nonimage areas, letters and pictures can be formed on the printing plates.

The digital technology replaces printing plates with a thin coating of what Sullivan called gelatinous "goo." When the beam of the company's Squarespot thermal laser imaging system strikes it, dark and light areas are created, forming an image of a page. The remainder of the process uses the usual offset method. At the end of the press run, the goo is wiped off and a fresh batch is applied for the next run.

For proprietary reasons, Sullivan could not describe the laser system any further, except to say that it relies upon the thermal features of an 830-nm laser and produces halftone dots with hard-edge characteristics. And although the resulting print physically contains 4000 dots per inch, the human eye perceives it at a higher resolution, usually about 10,000 dpi.

The company is working with press manufacturers to develop laser imaging systems that can be mounted onto all varieties of offset printing presses. It expects to have a commercial product in two years.

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