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Direct Photonegative for Electroerosion Printer

IP.com Disclosure Number: IPCOM000103515D
Original Publication Date: 1990-Dec-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 1 page(s) / 59K

Publishing Venue

IBM

Related People

Afzali-Ardakani, A: AUTHOR [+3]

Abstract

In electroerosion printing, a thin metal layer is eroded by an electrical current pulse to create a pattern of imaged and non-imaged (i.e., non-eroded) areas representative of the desired information. The printing medium is usually comprised of a substrate 10, a base or under layer 12, an erodable metal layer 14 (such as Al), and a lubricating overlayer 16. This plate can be used as a direct photonegative or as a short-run direct master if top layer 16 is removed prior to use. However, due to the moderate adhesion of the evaporated aluminum film 14 to the base coat composite 12 (e.g., pigmented polyurethane), the aluminum layer wears off readily due to friction caused by passing through print rollers.

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Direct Photonegative for Electroerosion Printer

      In electroerosion printing, a thin metal layer is eroded by an
electrical current pulse to create a pattern of imaged and non-imaged
(i.e., non-eroded) areas representative of the desired information.
The printing medium is usually comprised of a substrate 10, a base or
under layer 12, an erodable metal layer 14 (such as Al), and a
lubricating overlayer 16.  This plate can be used as a direct
photonegative or as a short-run direct master if top layer 16 is
removed prior to use.  However, due to the moderate adhesion of the
evaporated aluminum film 14 to the base coat composite 12 (e.g.,
pigmented polyurethane), the aluminum layer wears off readily due to
friction caused by passing through print rollers.  When the aluminum
layer wears off (starts at 1000-1500 copies), the hydrophobic base
coat 12 in non-imaged areas becomes exposed and causes toning of the
non-imaged areas.  Another reason for the relatively short lifetime
of this plate is that the evaporated aluminum film does not cover the
base coat uniformly so that pinholes develop in the metallized
surface of the plate.  These pinholes are of such a dimension that
they do not interfere when the plate is used as photonegative.
However, when the plate is used as a short-run direct master they act
as a nucleous of wear of metal film during the printing process.

                            (Image Omitted)

      In order to overcom...