Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Th~ present inven-tion relates to an improved
xerographic processing system for producing very hig~
quality electrostatically developed images by the trans-
fer of these images to support material, such as sheets
of plain paper with a minimum of background carryover,
and fixing the transEerred images by means which produces
copy having little or no adverse quality aspects such
as background, oil deposits, curl or any other cause
for the degradation of images.
- In conventional xerography, a xerographic plate
comprising a layer of photosensitive insulating material
affixed to a conductive backing is used to support electro-
static latent images. In the xerographic process, the
photosensitive surface is electrostatically charged,
and the charged surface is then exposed to a light pat-
tern of the image being reproduced to thereby discharge
the surface in the areas where light strikes the surface.
'rhe undischarged areas o`f the surface thus form an electro-
static charge pattern (an electrostatic latent image)
conforming to the orlginal pattern. The latent image
is then developed by contacting it w~lth developing material
having a finely divided electrostatically attractable
powder referred to as "toner". Toner is held on the
image areas by the electrostatic charge on the surface.
Where the charge is greater, a greater amount of toner
is deposited. Thus, a toner image is produced in con-
formity with a light image of the copy being reproduced.
Generally, the developed image is then transferred to
a suitable support material (e.g. paperj, and the image
is affixed thereto to form a permanent record of the
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original document.
The developing material normally comprises
relatively large carrier beads, which may be insulatively
coated metal, and the relatively smaller dry ink particle
toner. Due to the triboelectric relationships between
the two, the smaller toner particles attach themselves
to the carrier in great numbers. As the developing material
is brought into contact with the photoreceptor surface,
electrostatic charges on the photoreceptor tends to separate
10 the toner particles from the carrier and deposit the
same onto the photoreceptor in accordance with the latent
image charge pattern. The carrier, some of which may
be denuded or partially denuded, is returned to a devel-
oper sump for replenishing with toner particles.
In the practlce of xerography, the support
material is caused to move in synchronized contact with
the photosensitive surface during the transfer operation,
and an electrical potential opposite from the polarity
of the toner is applied to the side of the paper remote
~20 from the photosensitive sur~ace to electrostatically
attract the toner lmage from the surface to the paper.
Some modern high speed duplicating machines
utilize an electrically biased transfer roll to effect
the image transfer. Although a biased transfer roll
25 system effects very good to excellent copy quality, certain
copy quality deficiencies may be present. The most notable
of these is the difficulty of transferring very small sizes
of toner particles, say on the order of 3 to 10 micron
diameter sizes. This inability is apparent because of
30 the geometry of a roller type electrostatic transfer device.
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As the surface of roller approaches the nip at which trans-
fer of toner particles occu~, there is a tendency for
voltage breakdo~m if the transfer potential is too high.
Lowering of the transfer voltage to avoid voltage breakdown,
will limit the size oE toner particles which can be made
to adhere to support material.
In general, conventional xerographic machines
are capable of producing good quality images, however, their
respective developing systems suffer serious deficiencies
in certain other areas. A more noted deficiency is the
inability to reproduce contrast in image areas. In the
reproduction of high contrast copies such as letters, trac-
ings, and the like,.it is common to select the toner particles
and carrier materials so that their mutual electrication
is governed in most cases by the distance between their
relative positions in the triboelectric series. However,
when otherwise compatible ! toner particles and car~ier
mate.rials which are removed from each other in the tribo-
electric series by too great a distance, may result in very
faint images because the attractive forces betwee~ the
carrier and toner particles compete with the attractive
forces between the electrostatic latent image and the toner
particles.
. Another deficiency found in conventional develop-
ing systems is their inability to reproduce density with
acceptable fidelity. Although image density may be improved
in conventional developing systems by Increasing the toner
concentration in the developer mixture, u~desirably high
background toner deposition as well as increased toner im-
paction and agglomeration is encountered when the toner
1~3~89~
concentration in the developer mixture is excessive, that
is, there is insufficient carrier surface for t~e amount
of toner. As an alternative, the initial electrostatogra-
phic plate charge may be increased -to improve the density
of the deposited powder image, but the plate charge would
ordinarily have to be excessively high in order to attract
the toner particles away from the carrier particles. Ex-
cessively high electrostatographic plate charges are not
only undesirable because of the high power consumption
necessary to maintain the electrostatographic plate at-
high potentials, but also because the high potential causes
the carrier particles to adhere to the electrostatographic
plate surface rather than merely roll across and off the
electrostatographic plate surface.
' ' Print deletion and massive carr~over of carrier
` particles often occur when carrier particles adhere to re-
usable electrostatographic image surfaces. Massive carrier
carry-over problems are particularly acute when the developer
' is employed in solid area coverage machines where excessive
quantities of toner particles are removed from carrier
' partic~es thereby leaving many carrier particles substan-
tially bare of toner par,ticles.
Another xerographic processing step which seriously
degrades quality is in the area of image ~ixing on support
material such as copy sheets. By far and large the vast
majority of xerographic reproduction machines in conventional
use utilizes a fixing apparatus comprising a heated fuser
roller and a backup roller in contact with the fuser roller
to provide a nip through which unfixed images on support
material are conveyed. In order to prevent o~fset, that
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is, the adherence of toner paeticle to the fuser roller,
various types of materials have been utilized for the outer
coating of this roller. The more notable attempt to elim- -
inate or minimize offset has been the use of oil such as
silicone oil upon the fuser roll by means of the application
of a very thin layer of the oil. Other attempts have in-
volved the use of special materials for the fuser roller
such as silicone rubber. It is well known that a thin
layer of silicone rubber alone may inhibit offsetting of
toner particles. In some instances, however, some very
small quantities of silicone oil are nevertheless needed
but not in such quantities as other fuser roller materials
have been found to need. In any event, even the use of
silicone rubber as the outer coating of the fuser roller
without the supplemental use of silicone rubber has pro-
duced silicone oil from the silicone rubber materla1.
The use of silicone oil directly results in each
copy sheet acquiring some degree of oil embedded in the
material. With the use of silicone rubber alone, for a
fuser roller the silicone oil generated during the fusing
operation also becomes embedded in the support material
but to a lesser degree. These intrusions by silicone oil
may be acceptable for ordinary standard reproduction needs.
However, for high grade quality, reproductions at very high
speeds, this intrusion of silicone oil is unacceptable.
For machines which are capable of duplex operation, that
- is, the reproduction of images on both sides of sheets of
paper, the presence of silicone oil in the paper material
caused by the production of an image on a first side of
a copy sheet can adversly affect the xerographic processing
.
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during the second movement of the sheet through the repro-
duction machine for the production of an image on the-other
side.
The present invention contemplates the use of
fixing techniques which avoids the production of silicone
oil by any means. The technique, ~nown as "flash" fusing,
is capable of producing matte finishes of images which in
the industry has been considered the ultimate in finished
copy. The conventional roll type fusing as described above
generally results in solid area fused images which have
a high gloss appearance, and therefore not considered as
top grade quality reproduction.
One of the problems in utilizing flash fusing
techniques is that conventional equipment generally utilized
in this technique cannot adequately fuse images wherein
the plle heights of the toner particles are too high or
beyond the fusing limits for the energy released during
a flash. The flashed energy generally cannot carry through
to the lower levels of the toner particles, or those levels
which are directly in contact with the support material.
This inability is more pronounced for use in machines cap-
able of high speed production, say on the order of 70 copies
or more per minute. Consequently, the images especially
those of high density will not be completely fixed and smearing
and smudges will occur. The present invention contemplates
the use of the flash fusing technique in conjunction with
a specific range of toner particle sizes wherein pile heights
which are presented to the fixing apparatus are of relatively
small dimensions even for the most dense images so that
complete fusing is possible for all specific velocities
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:
of movement of sheets through the fusing apparatus. Highest
quality reproductions have been achieved utilizing this -
combination for line copy images, solid area coverage and
half-tones without the necessity of eEfecting machine adjust-
ments and parameter changes.
The toner particles contemplated for this purpose
in turn must be related to the various potentials utilized
during the xerographic processing. For instance, a charging
potential for distributing uniform charge on the photoreceptor
utilized in the xerographic processing must be correlated
to the toner particles dimensions as well as the tribore-
lationship of the toner particles relative to the host
~ ' .
carrier beads. Similarly, the developing technique must
also be correlated. If magnetic brush development techniques
are utilized, the electrical bias for the magnetic brush
must be integrated with the toner particles and carrier
.,
beads and the electrostatic charge levels of the latent
images. In addition, thé transfer blas utilized to trans-
fer toner particles from the photoreceptor surface to one
j side of the support material must also be related;to ~
the toner particles~and carrier béads, the~charging potential
, ~ , -
- and the bias on the magnetic brush. The transfer corona
generating device must be suitable to effect transfer of
the smallest toner particles say on the order of 3 to 8
microns in diameter. This necessitates the use of a corona
generating device having one or more electrode wires which
when energized with the suitable potential sprays ions on
i the back side of the sheet of paper durin~ the transfer
step.
From the foregoing it will be appreciated that
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the present invention contemplates the integrated action
of various xerographic processing steps and parameters in
order to acquire reproduced images of the highest quality.
The integrated action involves the use of flash fixing tech-
niques, parameters and characteristics of toner particlesand carrier beads, various electrical biases and potentials
utilized for corona generating devices and a specific type
of corona generation.
Prior issued patents disclosing the use of flash
fusing system do not correlate this method of toner fixing
to the size of toner and carrier particles, nor other para-
meters utilized in electrostatographic processing. In the
German Patnet No. 2,505,416, there is a specific disclosure
of circuitry for a flash fusing system. In the German Patent
No. 2,638,658, the disclosure is directed to the application
of heat in a flash fusing system compared to other types
of fixing systems. In the U.S. Patent No. 3,445,626, the
disclosure is restricted to circuitry to accomplish multiple
triggering of a flash fusing lamp. Similarly, the U.S.
Patent No. 3,871,761 is more concerned with specific cir-
cuitry for a flash lamp in a flash fusing system. None
of the foregoing patents address the significance of flash
fusing of toned images made up of relatively small diameter
toner particles.
It is therefore an object of an aspect of the present
invention to produce xerographic images of the highest quality.
It is an object of an aspe~t of the invention to
integrate various xerographic processing steps and parameters
which has a combined action adapted to effect the reproduc-
tion of images of the highest quality.
According to one aspect or this inven~ion~here is provided an electrostatographic processing system
having developer mixture of finely~divided toner particles
electrostatically clinging to the surface of carrier par-
ticles; a corona device for uniformly charging the photo-
sensitive surface prior to production of an electrostatic
latent image; a development apparatus for developing the
latent image; a transfer station whereat support material
is placed into contact with the photosensitive surface
bearing a developed image for receiving the same; and an
image fixing station whereat support material is conveyed
for effecting the fixing of a transferred image thereon,
the improvement comprising:
the toner particles having a particle diameter
in the range of between about 3 microns and about 15 microns,
and the carrier particles having a particle diameter in
the range of between about 15 microns and about 65 microns,
and
a fusing device at the fixing station having a
flash energy emitting device arranged to direct pulses of
energy upon the transferred toned image on the support
material, means connected to said flash energy emitting
device for effecting energization thereof in timed sequence
relative to the movement of the support material through
the ~ixing station.
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The above objects and others are accomplished
and will be more fully understood from the following des-
cription of apparatus shown by wa~ of example in the accom-
panying drawings in which:
Fig. 1 is a schematic view of an electrostatic
type reproduction machine embodying the principles of the
present invention;
Fig. 2 is a schematic circuit representation of
the flash fusing system utilized in the present invention;
and
FigO 3 is a series of timing diagrams of signals
and pulses produced in the present invention for control
purposes.
While the present invention is describe~ in rela-
tion to the utilization of the magnetic brush developmenttechnique, it is not to be limited thereto. Other, known
development techniques may be employed in the processing
system described herein, such as, "cascade" development,
"powder cloud" development, and "touch down" development.
In using these other techniques, there will be need ~or
re-optimizing structures and circuitry. Magnetic brush
development provides a more suitable environment for op-
timum quality. For further descriptions of thes~ tech-
niques, reference is made to the copending Canadian
patent application Serial No. 322,602 filed February 28,
1979 and to the same assignee.
The processing system for the present invention
envisions the use of the developer material disclosed and
claimed in the above-referred to Canadian application.
Specifically, the present processing system
-,t ~, --10--
contemplates the use of toner having a particle size in
the range of 3 microns to about 15 microns, and conductive/
magnetic, metallic carrier materials, preferably nickel,
having a particle diameter in the range of between about
15 microns and about 65 microns. It has been found that
the developer materials of this classification when used
in the present invention provlde vastly improved results
over conventional developer materials. Even better results
were obtained when, and it is preferred that, the toner
materials have a particle diameter in the range of between
about 3 microns and about 10 microns and the carrier materials
have a particle diameter in the range of between about
10 microns and about 40 microns. Optimum results were
obtained when the toner materials had a particle diameter
in the range of between about 3 microns and-about 8 microns
and the carrier materials have a particle diameter in
the range of between about 8 microns and about 24 mlcrons.
For a general understanding of an electrostatlc
reproduction machine in which the present invention may
be incorporated, reference is made to Fig. l. As in all
electrostatic reproduction machines of the type illustrated,
a light image of an original is projected onto the photo-
sensitive surface of a xerographic plate to form an electro-
static latent image thereon. Thereafter, the latent image
is developed with an oppositely charged developing material
comprising carrier beads and toner particles triboelectrically
adhering thereto to form a xerographic powder image corres-
ponding to the latent image on the photosensitive surface.
The powder image is then electrostatically transferred to
a transfer member such as a sheet of paper to which it may
--11-- - -
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~3~
be fixed by a fusing device whereby the toner image is caused
permanently to adhere to the transfer member.
In the illustrated machine 10, an original 12
to be copie~ is placed upon a transparent support platen
14 fixedly arranged in an illumination assembly indicated
generally by the reference numeral 16. While upon the platen,
the illumination assembly flashes light rays upon the original,
thereby producing image rays corresponding to the informational
areas on the original. The image rays are projected by
means of an optical system 18 to an exposure station 20
for exposing the surface of a moving xerographic plate in
the form of a flexible photoconductive belt or photoreceptor
22. In moving in the direction indicated by the arrow,
prior to reaching the exposure station 20, that portion
of the belt being exposed would have been uniformly charged
to approximately ~500 to ~600 volts by a corona generating
device 24 located at a belt run extending between thé belt
supporting rollers 26 and 28. The exposure station extends
between the roller 28 and a third roller 30.
20 ~ The e~posure of the photosensitive surface of
the belt to the light image discharges the surface in the
areas struck by light whereby al~ electrostatic latent image
remains on the belt in image configuration corresponding
to the light image projected from the original on the support
platen. As the belt~continues its movement, the latent
image passes around the roller 30 and through a developing
station 32 where a developing apparatus indicated generally
by the reference numeral 34 is positioned. The developing
apparatus 34 preferably comprises a plurality of magnetic
brushes 36 which carry developing material to the surface
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of the upwardly moving belt 22. As the developing material
is applied to the belt, toner particles in the development
material are electrostatically attracted to the charged
photosensitive surface to form a powder image (an electro-
:static developed image). The brushes 36 for the apparatus
34 are electrically connected to a d.c. power supply 37
by way of a bus bar 38 to be electrically biased in accor-
dance with the electrical field needed be-tween the brushes
and the photoreceptor 22. A variable resistance device
39 is connected to the circuit to permit variation in the
magnetic brush biasing in accordance with the particular
toner/carrier electrostatic characteristics and the electro-
static charge of the latent image being developed. The
apparatus 34 is electrically insulated from the remaining
structure of the machine so that the electrically conductive
carrier particles do not short out, or cause electrical
. . , ~ . .
~ shorts relative to the machine~ -
¦ The developed electrostatic image is transported
by the belt 22 to a transfer station 39 where a sheeL of
paper is moved at a speed in synchronism with the moving
belt in order to effect transfer o~ the developed image.
Located adjacent the transfer station 39 is ~a sheet guide
roller 40 which is rotatably arranged on the frame of the
machine to receive individual sheets from a sheet conveyor
41 of a transport mechanism 42 and to guide each sheet to
the transfer station 9.
The sheet transport mechanism 42 transports sheets
of paper seriatim from a paper supply system indicated generally
by the reference numeral 44 to the developed image on the
~ 30 belt as the same is carried around the roller 26.
¦ At the transport station 39, a transfer corona
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generating device 48 having one or more corona emitting
wires is positioned to effect the back side of a sheet of
a sheet of paper as -the ].atter is moved or fed between the
photoreceptor belt 22 and the device 48. The corona emi~ting
wire in the device ~8 is electrically biased by means of
a circuit 50 with sufficient voltage to effect ion spray
upon the adjacent side of each sheet of paper passing there-
beneath so that the developed image on the belt may be electro-
statically attracted to its ad]acent side of the sheet of
paper as the latter is brought into contact therewith.
As a sheet emerges from the transfer station 39,
a charge is deposited thereon by a detack corona generating
device 52 to lessen the electrostatic attractiGn between
the belt 22 and the sheet so that the latter can be removed
by a vacuum stripping and transport mechanism S~. The sheet
is thereafter retained on the underside of the vacuum stripping
transport mechanism 5~ for movement into a fuser asssmbly
indicated generally by the reference numeral 56 wherein
the powder image on the sheet is permanently affixed thereto.
After fusing, the finished copy is discharged at a suitable
point for collection. The toner particles remaining as
resid~le on the belt 22 are carried by the belt to a cleaning
apparatus 58. The cleaning apparatus 58 comprises a corona
discharge device 60 for neutralizing charges remaining on
the untransferred toner particles, a rotating brush 62 mounted
within a housing 64 and a vacuum outlet 66.
The fusing apparatus 56 envisioned in this invention
is of the flash fusing type and comprises one or more flash
Xenon lamps 67 suitably mounted in a cavity enclosure 68
positioned below and in close proximity to the transport
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54. Each sheet of paper bearing a toned image to-be-fused
is conveyed in an inverted condition by the trarlsport 5~,
and into and out oE the cavit~ 68. As each sheet moves
through the cavity in close proximity to the lamp 67, ener-
.: ,
gization of the lamps effect Eixing oE the toned images
upon the sheets. In the drawing, two lamps 67 are shown,
electrically connected in series to a rectifier circuit
70 which in turn is electrically connected to the secondary
coil of a transformer T-l. The primary coil for the trans-
former is electrically connected by way of a filter box
72 to a suitable source of a.c. current. Connected across
the output terminals of the d.c. rectifier 70 is a charging
capacitor 73 which is capable of storing very high voltage
with a short time constant in order to ener~ize the flash
lamps 67 and produce energy capable oE fixing toner developed
on a sheet of paper in the fusing apparatus 56. A bleed
resistor 74 is connected across the capacitor 73 to discharge
the same, and a lamp 75 is utilized to indicate when high
~ voltage is on the capacitor.
~ Since it is desirable that the flash lamps 67
be adapted for energization to produce suffic1ent energy
to effect adequate fixing of toner images on a sheet of
paper, the circuit illustrated in Fig. 2 is capable of fully
energizing the lamps 67 at the rate of two flashes per image
to be fused. It will be understood that more flashes may
be devised and for shorter periods of time. In order to
effect quick and complete ignition of the flash lamps 67,
the lamps are associated with a triggering arrangement having
triggering wires 78, one associated with each of the flash
J0 lamps 67 respectively, connected to the output coll 7g of
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a trigger coil system having its other coil 8Q connected
to a pulse forming network or triggering device generally
indicated at 81. As will be described, the network 81 is
adapted to produce one or more pulses Eor energizing the
S trigger wires 78 thereby efEecting flashing of the flash
lamps 67 once per pulse emitted by the triggering device 81.
The triggering device 81 operating with the trigger
coil 79 provides a high voltage transient pulse (approxi-
mately 15kv) which is connected to the trigger wires 78.
This arrangement serves as an external trigger for the Xenon
flash lamps 67 and initiates ionization of the gas in these
lamps. The device 81 is supplied with d.c. voltage from
a power supply 82 which includes a full wave rectifier 84
connected to a suitable source of external a.c. supply in-
dicated at 85. The d.c. voltage output for the circuit
~ 82 is on the order of +10 volts and -~20 volts, the latter
¦ of which continuously supplies the device 81. The output
of the device 81 is derived in accordance with the output
of a flashing circuit 87 which IS connected to the device
81 by way of a conductor 88.
- The output of the circuit 87 to the device 81
is initiated by actuation of a paper path switch PPl to
a closed condition. The switch PPl may be suitably located
in the paper path of the machine 10, preferably adjacent
to the fuser assembly 56. As shown in Fig. 1, the switch
PP1 is positioned relative to the sheet transport 54 and
is actuated to a closed position by the leading edge of
a sheet of paper being transported on the lower run of the
transport 54. As shown in Figs. 2 and 3, the closing of
the switch PPl initiates a one shot multivibrator 90 which,
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in turn, provides a pulse output delayed a predetermined
length of time to allow the first portion of a sheet of
paper to enter the fuser cavity 68. This pulse from the
multivibrator 90 is conducted to an OR gate 92 and to another
one shot multivibrator 93 which provides a pulse output
at the time the latter portion of the paper is in the fuser
cavity 68. The OR gate responds to both pulses and connects
to another one shot multivibrator 95 acting as a pulse
shaper with a positive pulse greater in duration than the .
duration of the pulses in the gate 92. This outpu-t is con-
nected by way of a resistor 96 to the two transistors 97,
98. With the transistor 97 being connected to a source
of pulsating electrical power, it is conducting and saturated,
except when the line voltage goes through zero volts. It
serves then as a zero-crossing detector and only allows
the transistor 98 to be turned ON at zero crossings and
when the pulses are present out of the multivibrator ~5.
In this manner, each sheèt of paper being transported through
the fusing apparatus 56 undergoes two fixing flashes by
the flash tubes 67. It will be obvious to the artisan that
additional delay timing multivibrators may be added as input
to the OR gate 92 to effect morQ than two fixing flashes
by the flash lamps 67 for each sheet of paper being trans-
ported into the fixing device 56.
The parameters chosen for the circuit illustrated
in Fig. 2 is such that a relatively small and inexpensive
power pack is devised for charging the capacitor 73 to a
sufficient amount needed to produce that energy from the
flash lamps suitable for completely fixing the toned images
on each sheet of paper. In view of the use of very small
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toner particles say on the order of 3 to 1~ microns in con-
junction with the conductive carrier particles having a
diameter of approximately between 10 and ~0 microns, the
heights of the toner piles presented Eor fixing can ~e well
s within the fusing range for the energy produced by the lamps
67. It is envisioned that some developed images of solld
area, half-tones and line cop~ may have pile heights equiva-
lent to three or more layers of toner particles. Since
the toner par~icle diameters are very small as contemplated
in this invention, the amount of energy for the flash fusing
type of fixing apparatus will require a relatively~small
power pack. Heretofore, fusing apparatus of the flash
fusing type wherein relatively large toner particles were
utilized for development necessitated the use of very large
and powerful power packs comprising a plurality of high
capacity capacitors for storing energy utilized in flashing
the flash lamps.
With the use of relatively small carrier beads,
a total carrier surface that is greater ~han for larger carrier
beads is available for supporting more toner particles.
Therefore, there is a higher density of toner particles
in the developing material envisioned in this material.
Besides adding to the more complete development of latent
images, this higher density of toner particles serves as
electrical insulators for the electrically conductive carrier
beads to prevent the beads from producing electrical shorts.
The use of relatively small toner particle diameters
and corresponding relatively small carrier particles in
a reproduction machine in turn requires a charging potential
of relatively reduced value. Since the toner and carrier
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sizes are relatively small, there is no need for hi~h potential
chargin~ of the photoreceptor, which in conventional machines
using conventional developing rnaterial is on the order of
900-1100 volts. The charging cirçuit 50 is arranged so
that the charging potential is relatively low, say on the
ordee of -~500 to +600 volts, which parameters are correlated
to the size of the development material particles and the
triboelectric relationship therebetween. It has also been
found that higher quality development occurs when the tribo-
electric relationship between toner and carrier in the present
system was low.
. After image exposure at the exposure station 20,
the electrostatic latent image now has electrostatic poten-tial
- levels generally in the range between 300 and 400 volts,
or at least resulting in an electrostatic back~round~image
contrast wherein there is no need for relatively high develop-
ment biases. Consequently, the arrangement of the- magnetic
electrical bias circuit 37 is such that the potential applied
~o the magnetic brushes 36 is reduced and only sufficient
to insure the removal of toner particles from their parent
carrier particles and attraction to the remaining charged
areas of the latent image. Since low development bias is
utilized in this arrangement, there is little or no need
: for bias variations to account for light originals or dark
backgrounds in the original.
When a sheet of paper is applied to the developed
latent ima~e at the transfer station, the amount of transfer
potential applied by the transfer corona generating device
48 is relatively low only requiring that necessary to insure
that the toner particles will adhere to the sheet of paper
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at stripout of the sheet. Since the invention envisions
the use of an ion spraying corona generating device the
smallest of toner particles will readily adhere to the
sheet of paper as a transferred image.
By virtue of the small toner and carrier par-
ticles, which provide a far greater development capability,
process speeds for conven-tional machines have been in-
creased, for example, by a Eactor of 2.5. However, in
order to accomplish toner fusing at this greater process
speed in conventional machines with conventional developer
material would ordinarily require proportional increase
in fusing power. This requirement is reduced considerably
by the use of the foregoing described deYeloper material,
and in the environment disclosed therewith.
Another advantage in the system described herein
has been demonstrated in the scanning type of document
exposure copiers wherein there is a tendency for the scanning
mechanism to scan at varying velocities due to lack of~
precision in its mechanical parts. These inaccuracies
2a~ effect decreases or variations in image potentials on the
photoreceptor and, when developed out, skips and smears
appear in the finished copy because of the lack of dens~ties
the decreases or variations produce. The foregoing in-
vention when applied to scanning type of copiers eliminates
or minimizes the otherwise lack of density in image areas
caused by varying scanning velocities.
Another advantage in the foregoing described
invention has been observed relative to the usual degrada-
tion of copy quality as developer material continues to
be used repeatedly. It has been found that after the usual
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life of developer material, the quality of copy continued
to be acceptable, thus exhibiting the characteristics
-that the foregoing material in the described environment
has relatively long life.
F~om the foregoing, it will be apparent that the
present invention is concerned with the integrated action
oE a number of processing steps, parameters and values applied
at these processing steps and the parameters and characteristics
of the development material. For complete and Eull interaction
in order ~o obtain the highest possible quality available in
xerographic processing as described in the foregoing, the
invention envisions reduced charging potential for applying
a uniform charge on a photoreceptor prior to exposure, a
correlated development bias potential, a correlated transEer
- 15 potential in conjunction with an ion spraying type of corona
generating device, and the use of a flash fusing-arrangment
capable of providing complete Eusing of ~toned images applied
~ to each sheet of paper.
.~ . , ~ '
-21-
.. . . . . .
