CA1132181A - Electrostatographic processing system - Google Patents
Electrostatographic processing systemInfo
- Publication number
- CA1132181A CA1132181A CA321,527A CA321527A CA1132181A CA 1132181 A CA1132181 A CA 1132181A CA 321527 A CA321527 A CA 321527A CA 1132181 A CA1132181 A CA 1132181A
- Authority
- CA
- Canada
- Prior art keywords
- microns
- image
- support material
- toner particles
- range
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000012545 processing Methods 0.000 title claims abstract description 27
- 239000002245 particle Substances 0.000 claims abstract description 89
- 238000012546 transfer Methods 0.000 claims abstract description 32
- 238000011161 development Methods 0.000 claims abstract description 23
- 239000000463 material Substances 0.000 claims description 54
- 238000004519 manufacturing process Methods 0.000 claims description 8
- 150000002500 ions Chemical class 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 6
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 4
- 230000006872 improvement Effects 0.000 claims description 4
- 239000007921 spray Substances 0.000 claims description 3
- 229910052759 nickel Inorganic materials 0.000 claims description 2
- 239000000696 magnetic material Substances 0.000 claims 1
- 230000002596 correlated effect Effects 0.000 abstract description 6
- 239000004615 ingredient Substances 0.000 abstract 1
- 230000018109 developmental process Effects 0.000 description 17
- 238000000034 method Methods 0.000 description 15
- 230000033458 reproduction Effects 0.000 description 13
- 230000000694 effects Effects 0.000 description 12
- 108091008695 photoreceptors Proteins 0.000 description 11
- 239000011324 bead Substances 0.000 description 9
- 229920002545 silicone oil Polymers 0.000 description 9
- 239000000843 powder Substances 0.000 description 7
- 229920002379 silicone rubber Polymers 0.000 description 6
- 239000004945 silicone rubber Substances 0.000 description 6
- 239000003990 capacitor Substances 0.000 description 5
- 230000032258 transport Effects 0.000 description 5
- 230000009471 action Effects 0.000 description 4
- 239000012876 carrier material Substances 0.000 description 4
- 230000000875 corresponding effect Effects 0.000 description 4
- 230000007812 deficiency Effects 0.000 description 4
- 230000007723 transport mechanism Effects 0.000 description 4
- 230000015556 catabolic process Effects 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 230000008901 benefit Effects 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000006731 degradation reaction Methods 0.000 description 2
- 238000005286 illumination Methods 0.000 description 2
- 238000005507 spraying Methods 0.000 description 2
- 229910052724 xenon Inorganic materials 0.000 description 2
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 description 2
- 241000183024 Populus tremula Species 0.000 description 1
- 230000001154 acute effect Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 238000005513 bias potential Methods 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 238000012217 deletion Methods 0.000 description 1
- 230000037430 deletion Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 238000005421 electrostatic potential Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 230000003472 neutralizing effect Effects 0.000 description 1
- 239000000615 nonconductor Substances 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 229920000136 polysorbate Polymers 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 230000000153 supplemental effect Effects 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
- 230000001052 transient effect Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G9/00—Developers
- G03G9/08—Developers with toner particles
- G03G9/0819—Developers with toner particles characterised by the dimensions of the particles
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G9/00—Developers
- G03G9/08—Developers with toner particles
- G03G9/10—Developers with toner particles characterised by carrier particles
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G15/00—Apparatus for electrographic processes using a charge pattern
- G03G15/20—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat
- G03G15/2003—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat using heat
- G03G15/2007—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat using heat using radiant heat, e.g. infrared lamps, microwave heaters
- G03G15/201—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat using heat using radiant heat, e.g. infrared lamps, microwave heaters of high intensity and short duration, i.e. flash fusing
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G9/00—Developers
- G03G9/08—Developers with toner particles
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Developing Agents For Electrophotography (AREA)
- Fixing For Electrophotography (AREA)
- Dry Development In Electrophotography (AREA)
- Control Or Security For Electrophotography (AREA)
Abstract
ELECTROSTATOGRAPHIC PROCESSING SYSTEM
ABSTRACT OF THE DISCLOSURE
A xerographic processing system is disclosed and incorporates the art of flash fusing with the size/or triboelectric relationship of toner and carrier particles and being correlated with one or more of the various pro-cessing parameters of xerographic processing such as, charging potential, exposure levels, development bias. The nature of the application of the toner transfer potential is also an ingredient to the system in achieving utmost quality.
ABSTRACT OF THE DISCLOSURE
A xerographic processing system is disclosed and incorporates the art of flash fusing with the size/or triboelectric relationship of toner and carrier particles and being correlated with one or more of the various pro-cessing parameters of xerographic processing such as, charging potential, exposure levels, development bias. The nature of the application of the toner transfer potential is also an ingredient to the system in achieving utmost quality.
Description
~32~
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 ~J
1~3Z~8~L
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.
.
~132~
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 .
, .
" ,,,, ~3Z~8~
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 .
~ . .
~.. ' .. . .
~3;~8~
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 ~3;2~8~
:
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 ." ,, , ' ~ -8 ~L~3~8~
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.
-9a-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 ~ , ~ . . . . .
~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 ~32~8~L
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 ~.3~
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 ~32~
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 .
~32~8~
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, z~
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 ~L3Z~
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 ~, - - - , ~L~
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 . , ~ . .
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 ~32~L
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.
.~ . , ~ ' .. . . . . .
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 ~J
1~3Z~8~L
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.
.
~132~
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 .
, .
" ,,,, ~3Z~8~
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 .
~ . .
~.. ' .. . .
~3;~8~
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 ~3;2~8~
:
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 ." ,, , ' ~ -8 ~L~3~8~
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.
-9a-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 ~ , ~ . . . . .
~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 ~32~8~L
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 ~.3~
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 ~32~
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 .
~32~8~
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, z~
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 ~L3Z~
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 ~, - - - , ~L~
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 . , ~ . .
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 ~32~L
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.
.~ . , ~ ' .. . . . . .
Claims (7)
1. 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 fixing station.
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 fixing station.
2. The processing system of claim 1 wherein the size of the toner particles is in the range of about 3 mic-rons to about 10 microns and the carrier particles is in the range of between about 10 microns to about 40 microns.
3. The processing system fo claim 1 wherein the size of the toner particles is in the range of about 3 mic-rons to about 8 microns and the carrier particles is in the range of between about 8 microns to about 24 microns.
4. The processing system of claim 1 wherein the carrier particles comprise conductive magnetic material.
5. The processing system of claim 1 wherein the carrier particles comprise the material nickel.
6. 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, corona generating means at the transfer station having an electrode adapted to spray ions upon the back side of the support material for effecting the transfer of the developed image to the support material, 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 fixing station.
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, corona generating means at the transfer station having an electrode adapted to spray ions upon the back side of the support material for effecting the transfer of the developed image to the support material, 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 fixing station.
7. 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 station whereat development of the latent image has toner particles applied thereto;
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, magnetic developing apparatus at the development station having electrical biasing means for developing electrostatic latent images; 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 fixing station.
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, magnetic developing apparatus at the development station having electrical biasing means for developing electrostatic latent images; 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 fixing station.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US89391778A | 1978-04-06 | 1978-04-06 | |
| US893,917 | 1978-04-06 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1132181A true CA1132181A (en) | 1982-09-21 |
Family
ID=25402334
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA321,527A Expired CA1132181A (en) | 1978-04-06 | 1979-02-14 | Electrostatographic processing system |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS54134649A (en) |
| CA (1) | CA1132181A (en) |
| FR (1) | FR2422193A1 (en) |
| GB (1) | GB2018451B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4271248A (en) * | 1980-01-28 | 1981-06-02 | Xerox Corporation | Magnetic latent image toner material and process for its use in flash fusing developing |
| JPS6247651A (en) * | 1985-08-27 | 1987-03-02 | Canon Inc | Image forming method |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3967962A (en) * | 1973-11-23 | 1976-07-06 | Xerox Corporation | Developing with toner polymer having crystalline and amorphous segments |
| DE2505416A1 (en) * | 1975-02-08 | 1976-08-19 | Agfa Gevaert Ag | Electrophotographic copier using toner powder - using toner powder which is electrostatically attracted to the latent image and fused on it |
| GB1556162A (en) * | 1975-09-16 | 1979-11-21 | Agfa Gevaert | Method for fixing toner images |
| JPS5280126A (en) * | 1975-12-26 | 1977-07-05 | Toshiba Corp | Ticket issue means |
| JPS5280031A (en) * | 1975-12-26 | 1977-07-05 | Tomoegawa Paper Co Ltd | Electrostatography |
| JPS5311034A (en) * | 1976-07-19 | 1978-02-01 | Mitsubishi Electric Corp | Fixing device for toner image |
-
1979
- 1979-02-14 CA CA321,527A patent/CA1132181A/en not_active Expired
- 1979-03-30 JP JP3827279A patent/JPS54134649A/en active Pending
- 1979-04-03 FR FR7908297A patent/FR2422193A1/en active Granted
- 1979-04-04 GB GB7911824A patent/GB2018451B/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS54134649A (en) | 1979-10-19 |
| FR2422193B1 (en) | 1984-04-27 |
| FR2422193A1 (en) | 1979-11-02 |
| GB2018451A (en) | 1979-10-17 |
| GB2018451B (en) | 1982-06-23 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP0010375B1 (en) | Electrostatographic processing system | |
| US2901374A (en) | Development of electrostatic image and apparatus therefor | |
| US4660059A (en) | Color printing machine | |
| US3850519A (en) | Xerographic image transfer apparatus | |
| US4102305A (en) | Development system with electrical field generating means | |
| US3914460A (en) | Development utilizing electric fields | |
| US4282303A (en) | Development method and apparatus | |
| US4876575A (en) | Printing apparatus including apparatus and method for charging and metering toner particles | |
| US3791730A (en) | Apparatus for developing electrostatic latent images | |
| US3707390A (en) | Method for developing electrostatic latent images | |
| US3662711A (en) | Development apparatus | |
| US4371251A (en) | Electrographic method and apparatus providing improved transfer of non-insulative toner | |
| US4027960A (en) | Transfer system for electrostatic reproduction machine | |
| CA1132181A (en) | Electrostatographic processing system | |
| IL31765A (en) | Method and device for the electrostatic charging of surfaces | |
| EP0036290B1 (en) | Apparatus for cleaning particles from a surface | |
| US4572647A (en) | Hybrid development system | |
| US4105320A (en) | Transfer of conductive particles | |
| US4506971A (en) | Transfer system | |
| US6560432B1 (en) | Alloyed donor roll coating | |
| CA1073279A (en) | Treating an electrostatic latent image with charge of same polarity as that of image areas | |
| US3594159A (en) | Electrostatic copying method employing development on side of the imaging sheet opposite the photoconductive coating | |
| CA1134130A (en) | Xerographic process system with high density assist | |
| CA1044958A (en) | Method and apparatus for developing an electrical image | |
| EP0588552B1 (en) | Method and apparatus for charging a photoconductive surface to a uniform potential |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |