Browse Prior Art Database

SOLID AREA SUPPRESSION IN LIQUID DEVELOPMENT

IP.com Disclosure Number: IPCOM000023588D
Original Publication Date: 1978-Apr-30
Included in the Prior Art Database: 2004-Mar-31
Document File: 4 page(s) / 728K

Publishing Venue

Xerox Disclosure Journal

Abstract

Advantages of edge development for certain electrostatic copying requirements are well known; for example, edge deve1- opment provides increased exposure latitude and background suppression when line copy is made from low-contrast originals. This disclosure provides a method of suppressing development at interiors of large, uniformly charged areas while allowing development to take place at edges of electro-static images in the polar liquid development modes exemplified by the disclosure of U-S, Patent 3,084,043, where liquid developer is applied to an image by a patterned applicator, for example, a gravure cylinder.

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Page 1 of 4

XEROX DISCLOSURE JOURNAL

SOLID AREA SUPPRESSION IN LIQUID
DEVELOPMENT
Gary L~ Whittaker

Proposed Classification
U~S~Cle 355/10
Iflte Cl~ G03g 15/10

Advantages of edge development for certain electrostatic
copying requirements are well known; for example, edge deve1~
opment provides increased exposure latitude and background
suppression when line copy is made from low-~contrast
originals. This disclosure provides a method of suppressing
development at interiors of large, uniformly charged areas
while allowing development to take place at edges of electro~
static images in the polar liquid development modes
exemplified by the disclosure of U~S, Patent 3,084,043, where
liquid developer is applied to an image by a patterned
applicator, for example, a gravure cylinder.

Volume 3 Number 2 March/April 1978 119

[This page contains 1 picture or other non-text object]

Page 2 of 4

SOLID AREA SUPPRESSION IN LIQUID DEVELOPMENT (Cont~d)

The essential elements are illustrated in the drawing where
photoconductor 1 is placed on base material 2 having a resis~
tivity the value of which depends upon imaging parameters.
Base material 2 is held by conducting support material 3.
Inked gravure applicator 4 acts as an electrode. Ink 5 is
located in the depressed areas or "valleys" of gravure appli-~
cator 4,

During the charging and exposure of the photoconductor, the
gravure applicator (electrode) is in a position where it has
no effect thereon. The resistivity of base material 2 has a
short electrical relaxation time relative to the time in which
charging current is applied to the photoconductor and the time
interval between exposure and development. During charging
and following exposure, base material 2 acts as a conductor;
and the imagewise charge ~ and its counter charge (Q) at
the photoconductor/base interface assumes a spatial
distribution accordingly. The imagewise charge density (Q~)
has an abrupt or sharp edge whereas the counter charge density
(Q) spreads in the vicinity of the edge to produce a more
gradual drop in charge density across the image boundary pro-
ducing a "soft" edge.

Development of the image occurs in a short time compared to
the electrical relaxation time of the base. Therefore, the
counter charge (Q) is "frozen" in place during development,
and base material 2 acts as an insulator, The electrical
field (E) on gravure applicator (electrode) 4 is the algebraic
sum of the field (E~) induced by the positive image charge and
the field (E) induced by the negative counter charge or:

E E+ + E

The field plots (graph) 7 shown in the drawing are
qualitative. The plots or graph 7 indicate the expected
spatial behavior of the field on the electrode near an edge
shown by dotted line 6. Segments or parts of photoconductor 1
and gravure applicator 4 correspond to the analogous regions
on graph 7. Field (E~) is drawn with a sharp edge because
charge (Q÷) is close to the electrode. Field (E) is drawn
with a "soft" edge, The total field, E, is the algebraic sum
and has a high positive peak a...