American Hoechst Corporation

Eocom Corporation

William Jeffers

Raimund J Faust

Douglas A Seeley

Shuchen Liu

Klaus-Peter Schoen

Richard E Amtower

Norman L McGowan

This invention relates to an improvement in a photochemical process for the preparation of printing plates wherein a printing plate comprising a photosensitive composition coated on a support is exposed to a pattern of laser light, the intensity of which is modulated in accordance with an input source of information and said printing plate is subsequently developed by removal from said support of that portion of the photosensitive coating composition which is not exposed to said pattern of laser light, the improvement comprising utilizing a pattern of laser light generated by a laser at a wavelength greater than about 450 nm, and utilizing as a photosensitive composition a negative-working condensate of a para-aminobenzene diazonium compound, said compound being present in a quality of at least 25% of the total coating weight.

Dialo printing plate made from laser

This invention relates to an improvement in a photochemical process for the preparation of printing plates wherein a printing plate comprising a photosensitive composition coated on a support is exposed to a pattern of laser light, the intensity of which light is modulated in accordance with an input source of information, and said printing plate is subsequently developed by removal from said support of that portion of the photosensitive coating composition which is not exposed to said pattern of laser light, the improvement comprising utilizing a pattern of laser light generated by a laser, and utilizing as a photosensitive composition a mixture consisting essentially of: (1) a negative-working condensate of a para-amino benzene diazonium compound present in an effective amount sufficient to sensitize said photosensitive composition to laser light, and (2) a colorant capable of absorbing light in the spectral range between about 450 -550 nm, said colorant selectively sensitizing the condensate to said laser light at a wavelength greater than about 450 nm, and being selected from the group consisting of azo, triarylmethane, xanthene and methine compounds.

Preparation of diazo printing plates using laser exposure

An electrophotographic apparatus for producing printing masters utilizing modulated laser light as the exposure source and a continuous process for producing such printing masters involving the steps of plate conveyance, synchronous charging and exposure, and electrostatic development and fusing of electrophotographic printing masters suitable for use in offset or lithographic printing processes. The apparatus comprises a transport system for sequentially conveying printing masters to the exposure platen which retains the masters in a fixed plane for synchronous charging and exposure, utilizing as a light source, a modulated laser beam. The optical and deflecting components of the exposure system are mounted in a moveable carriage member adapted to traverse a plane substantially parallel to the plane of the exposure platen such that the exposure laser will raster scan the platen area. The charging coratron is also preferably mounted on the moveable carriage such that the sequence of charging the electrophotographic master and exposure thereof to the raster scan of the exposure laser are synchronous. The apparatus employs an exposure laser having a power of about less than 1 watt, but sufficient power to provide a light energy on the photoconductive surface of the printing master of at least about 2.times.10.sup.-3 millijoules/cm.sup.2 under operating conditions.

Electrophotographic apparatus and method for producing printing masters

Growing community of inventors

Fair Haven, NJ, United States of America

William Jeffers