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Direct Masters And Direct Negative by Resistive Ribbon Techniques

IP.com Disclosure Number: IPCOM000120903D
Original Publication Date: 1991-Jun-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 4 page(s) / 163K

Publishing Venue

IBM

Related People

Cohen, MS: AUTHOR

Abstract

The direct negative and direct plate (DN/DP) are currently made by an electro-erosion process whereby a thin aluminum layer is selectively removed in the image areas. The local removal of aluminum renders the selected area transparent (for use as a direct negative) and hydrophobic (for use as a direct master); the unselected background area is both opaque and hydrophilic. The principle of fabrication of the direct-master and negative by electro-erosion may thus be described as a "subtractive" mechanism.

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Direct Masters And Direct Negative by Resistive Ribbon Techniques

      The direct negative and direct plate (DN/DP) are
currently made by an electro-erosion process whereby a thin aluminum
layer is selectively removed in the image areas.  The local removal
of aluminum renders the selected area transparent (for use as a
direct negative) and hydrophobic (for use as a direct master); the
unselected background area is both opaque and hydrophilic.  The
principle of fabrication of the direct-master and negative by
electro-erosion may thus be described as a "subtractive" mechanism.

      Attempts have been made to create a direct master using
resistive ribbon technology by locally fusing a hydrophobic ink onto
a hydrophilic background.  The press life of such masters was
relatively short because of the poor adhesion of the hydrophobic ink
to the background area.  What is proposed here is the use of the
resistive ribbon technology not with such an "additive" approach
where hydrophobic ink is added to a hydrophilic background, but with
a "subtractive" approach whereby material is selectively removed, in
direct analogy to the electro-erosion approach. The subtractive
approach with the resistive ribbon technology can provide a direct
negative as well as a direct master.

      Selective subtractive removal of material by the resistive
ribbon technique has been demonstrated by the successful employment
of this technology in the "correction" mode (*) for ink on paper.
Here fresh ribbon contacts previously printed old ink and a reduced
current is used to fuse the ink of the ribbon to this old ink.  Then,
while maintaining contact of the ribbon to the ink by activation of a
special "correction bar" for that purpose, the fused ink bond is
allowed to cool.  The ribbon is separated from the old-ink position
only after cooling, so that the weakest joint becomes the adhesive
interface of the old ink to the paper, and the old ink is lifted off
the paper.

      Writing with a resistive ribbon can be done by using this
correction technique to remove material locally from an opaque,
hydrophilic foil, thereby rendering that foil locally transparent
(for the direct negative) as well as hydrophobic (for the direct
master).  For a specific implementation of this approach, a structure
very similar to that used for the electro-erosion DN/DP, i.e., a thin
aluminum film on a rough polymer-containing underlayer can be used.
Here the rough surface (which may not be absolutely necessary) is
advantageous because its high specific surface area serves to attract
more water.  Local chain and cool-down of the resistive ribbon while
writing in the "correction mode" is designed to remove the aluminum
layer locally.

      It should be noted that the thickness of the metallic films on
current foils is severely limited in the electro-erosion application
by the relatively low energy available for local removal of those
films.  This limitation is much les...