Electrophotography – Image formation – Development
Reexamination Certificate
2000-01-11
2001-06-26
Grimley, Arthur T. (Department: 2852)
Electrophotography
Image formation
Development
C399S265000, C492S056000
Reexamination Certificate
active
06253053
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a developer roll and a developer roll sleeve. More particularly, the present invention relates to a method for making the roll or sleeve coated with a wear-resistant conductive composition containing additives that improve, for example, the coating life, tribo/toner charging, toner release, or charge blade life.
BACKGROUND OF THE INVENTION
The basic operation of an electrostatographic printing machine is well known to those of ordinary skill. The term “electrostatographic” encompasses both electrophotographic and electrostatic printing. Typically, electrophotographic and electrostatic printing methods utilize a developer roll and a developer roll sleeve in the manner described below, except that electrostatic printing uses an insulating medium while electrophotographic printing uses a photosensitive medium to record an electrostatic latent charge image pattern on the medium.
Inasmuch as the art of electrophotographic printing is well known, reference is made to
FIG. 1
which schematically depicts various parts of an exemplary electrophotographic printing machine. As depicted in
FIG. 1
, a drum
10
having a photoconductive surface
12
is positioned to rotate in direction
14
about a central axis
15
. Around the periphery of drum
10
are provided a first corona generating device
16
, an exposure station
18
, a developer station
20
, a substrate stack
22
to supply single sheets of substrate
22
a
(via registration rolls
30
,
31
, and
32
rotating in the direction indicated by arrows
34
to advance single sheets of substrate
22
a
through chute
31
a
), a second corona generating device
36
, an endless belt
38
, a fixing station
60
, and a cleaning mechanism
40
. These components are used in concert to produce a duplicate image of an original image (not shown) onto a substrate surface such as paper. The various steps involved in a “printing cycle” are described in greater detail below.
During a typical electrophotographic printing cycle, the drum
10
is routinely rotated (typically at uniform speed) in direction
14
to interact with the various components of an electrophotographic printing machine. A typical printing cycle begins with the exposure of the photoconductive surface
12
to a uniform electrostatic charge at the first corona generating station
16
as drum
10
is rotated in direction
14
thereunder. Thus, under the influence of the first corona generating device
16
, the photoconductive surface
12
becomes uniformly charged. As it is subsequently rotated under exposure station
18
, the uniformly charged photoconductive surface
12
is exposed to a photographic light image (of an original image to be duplicated). During such exposure, photoconductive surface
12
on drum
10
is rotated about axis
15
(typically at a uniform rate). Thereby, a duplicate image of the original image intended to be copied is recorded on the photoconductive surface
12
in the form of an electrostatic latent charge image pattern.
At exposure station
18
, exposing light causes the uniform charge on surface
12
of drum
10
to be dissipated to yield the electrostatic latent charge image pattern as noted below. The amount of the uniform charge dissipated is proportional to the intensity of the exposing light. Those portions of photoconductive surface
12
not exposed to light at exposure station
18
continue to maintain a uniform charge. Thus, exposed portions of photoconductive surface
12
exhibit a dissipation of the uniform electrostatic charge while non-exposed portions maintain a uniform electrostatic charge. Thereby, photoconductive surface
12
now retains an electrostatic latent charge image pattern which corresponds to the photographic image of the original document. As photoconductive surface
12
on drum
10
is rotated beyond exposure station
18
, the electrostatic latent charge image pattern recorded thereon is now ready for “development” at developer station
20
.
Development of the electrostatic latent charge image recorded on the photoconductive surface
12
is achieved by transferring toner to the photoconductive surface
12
. For proper development, the toner is transferred to the photoconductive surface
12
in a manner that duplicates the pattern of the electrostatic latent charge image. Effective development is accomplished by transferring toner particles to the electrostatic latent charge image at a controlled rate so that the toner particles adhere electrostatically to the charged areas of the recorded electrostatic latent image. Typically, the degree of transfer of the toner to photoconductive surface
12
at developer station
20
is proportional to the charge carried by the electrostatic latent image.
Commonly, either a one-component (a single component toner) or a two-component toner (carrier and toner) may be used for development of the electrostatic latent charge image. A typical two-component toner comprises toner particles tribo-electrically attached to magnetic carrier granules or beads. A typical one-component toner is a single component particle which has both magnetic and electrostatic properties. When the one-component or the two-component toner is placed in a magnetic field, the toner particles form what is known as a “magnetic brush.” In particular, the toner particles within the magnetic field form relatively long chains which resemble the fibers of a brush. Thus, the term “magnetic brush” is aptly descriptive.
The developer roll
8
is optionally provided with a cylindrical sleeve
8
a
. Typically, the developer roll
8
is provided with an assembly of permanent magnets (not shown). Under the influence of a magnetic field (e.g., produced by the assembly of permanent magnets within the developer roll), the toner particles form the “magnetic brush” on the outer periphery of the developer roll
8
or on the outer periphery of the optimal developer roll sleeve
8
a.
At the developer station
20
, when the electrostatic latent charge image is advanced adjacent to the magnetic brush at nip
100
b
, the electrostatic charge on the photoconductive surface
12
is so biased that it attracts the toner particles away from the magnetic brush disposed on developer roll sleeve
8
a
(or on developer roll
8
).
While a “magnetic brush” development scheme has been described, other development schemes such as “scavengeless” development, single component development, single component scavengeless development and the like may be used. Each of these development schemes use a developer roll sleeve, a developer roll or an equivalent thereof.
By the transfer of toner particles, the photoconductive surface
12
now carries on its surface toner particles in a pattern that corresponds to the electrostatic latent charge image, which in turn corresponds to the photographic image of the original document intended to be duplicated. Hereinafter, the photoconductive surface
12
having toner particles deposited thereon in the aforementioned manner is referred to as the “developed” toner image.
As the drum
10
(together with the developed toner image) is advanced beyond developer station
20
, registration rolls
30
,
31
, and
32
are rotated in the direction of arrows
34
to advance single sheets of substrate
22
a
(e.g., paper) through chute
31
a
. In general, chute
31
a
directs the advancing sheet of substrate
22
a
into contact with drum
10
in a timed relationship so that the developed toner image contacts the advancing sheet of substrate
22
a
at nip location
100
, situated between the second corona generating device
36
and drum
10
. Preferably, the exemplary single sheet of substrate
22
a
is advanced to simultaneously arrive at nip
100
at about the same time as does the leading edge of the developed toner image disposed on surface
12
of drum
10
. At least substantially simultaneously, the second corona generating device
36
is powered-up to apply a spray of ions onto the backside of substrate sheet
22
a
disposed adjacent to the developed toner image at nip location
Litman Alan M.
Malespin Rafael
Zona Michael F.
Grimley Arthur T.
Oliff & Berridg,e PLC
Tran Hoan
Xerox Corporation
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