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Long Run Offset Masters Prepared by Electroerosion

IP.com Disclosure Number: IPCOM000103518D
Original Publication Date: 1990-Dec-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 1 page(s) / 54K

Publishing Venue

IBM

Related People

Afzali-Ardakani, A: AUTHOR [+4]

Abstract

Electroerosion can be used to prepare direct negatives and offset masters. The recording medium generally is comprised of a substrate, or support layer, a thin conductive layer (such as Al) that is electrically erodable, a base layer between the conductive layer and the substrate, and a protective lubricating layer on the conductive layer. In response to signals applied to a recording head containing multiple recording styli, electrical arcs can be created to erode the thin conductive layer in selected patterns. Since the metal layer (Al) is hydrophilic and the exposed base layer regions are oleophilic, the eroded recording medium can be used as an offset master.

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Long Run Offset Masters Prepared by Electroerosion

      Electroerosion can be used to prepare direct negatives and
offset masters. The recording medium generally is comprised of a
substrate, or support layer, a thin conductive layer (such as Al)
that is electrically erodable, a base layer between the conductive
layer and the substrate, and a protective lubricating layer on the
conductive layer.  In response to signals applied to a recording head
containing multiple recording styli, electrical arcs can be created
to erode the thin conductive layer in selected patterns.  Since the
metal layer (Al) is hydrophilic and the exposed base layer regions
are oleophilic, the eroded recording medium can be used as an offset
master.

      When this offset master is used for printing, the thin Al film
in the non-eroded (non-image) area begins to wear after several
hundred copies.  Since the underlying base coat is oleophilic, the
non-imaged areas will now begin to attract ink, and the master will
no longer be usable.  To solve this problem, the Al layer is replaced
by Al2O3, which has a much longer press life.

      Due to its non-conductivity and hardness, aluminum oxide cannot
be applied onto the base layer either alone or in conjunction with
the metal layer prior to the electroerosion process.  One way to
overcome this difficulty is to convert the non-imaged areas (the
areas which have not been electroeroded and are covered by aluminum
film) of the recording medium...