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Super-Long-Run Offset Masters by Electro-Erosion Printing

IP.com Disclosure Number: IPCOM000119290D
Original Publication Date: 1991-Jan-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 76K

Publishing Venue

IBM

Related People

Cohen, MS: AUTHOR [+3]

Abstract

Electro-erosion printing can be used to make long-run direct offset lithographic masters. Such masters are expected to be useable for tens of thousands of copies. There is also a need in the printing industry for offset masters which can print hundreds of thousands to one million copies; such super-long-run masters are often used, for example, in web offset presses.

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Super-Long-Run Offset Masters by Electro-Erosion Printing

      Electro-erosion printing can be used to make long-run
direct offset lithographic masters.  Such masters are expected to be
useable for tens of thousands of copies.  There is also a need in the
printing industry for offset masters which can print hundreds of
thousands to one million copies; such super-long-run masters are
often used, for example, in web offset presses.

      A preferred method for making such offset lithographic masters
by conventional means is by the fabrication of so-called bimetallic
plates.  Here two different metals are used, one of which is
hydrophylic while the other is hydrophobic.  Typically, copper is
used for the hydrophobic layer while aluminum is used for the
hydrophylic layer.  The master is provided with a photosensitive
overlayer which acts as a mask for subsequent etching in acid to
define the two different kinds of surfaces.

      The mask can be defined by electro-erosion, rather than by a
photographic process, as indicated in Fig. 1.  The two different
metal surfaces (thick copper 10 and Al layer 12) are defined by
etching through a mask.  The overlayer 14 is used as an etching mask,
and contains graphite in a crosslinked binder, so it is very tough
and resistant to the etching solution.

      Figs. 2-4 illustrate in more detail the process for making the
super-long-run master.  The topmost two layers 16, 18 comprise a mask
wherein the tip layer 16 is preferably made of a polymer containing
graphite and the layer 18 immediately beneath it is a thin aluminum
layer about 50 nm thick.  Under layer 18 is a thin, hard insulating
layer 20, w...