EP0041399B1 - Appareil et procédé de développement électrostatographique - Google Patents

Appareil et procédé de développement électrostatographique Download PDF

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Publication number
EP0041399B1
EP0041399B1 EP81302440A EP81302440A EP0041399B1 EP 0041399 B1 EP0041399 B1 EP 0041399B1 EP 81302440 A EP81302440 A EP 81302440A EP 81302440 A EP81302440 A EP 81302440A EP 0041399 B1 EP0041399 B1 EP 0041399B1
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EP
European Patent Office
Prior art keywords
development
developer
applicator
toner
layer
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
Application number
EP81302440A
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German (de)
English (en)
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EP0041399A3 (en
EP0041399A2 (fr
Inventor
Dan A. Hays
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Xerox Corp
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Xerox Corp
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Priority to AT81302440T priority Critical patent/ATE11604T1/de
Publication of EP0041399A2 publication Critical patent/EP0041399A2/fr
Publication of EP0041399A3 publication Critical patent/EP0041399A3/en
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Publication of EP0041399B1 publication Critical patent/EP0041399B1/fr
Expired legal-status Critical Current

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    • 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
    • G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
    • G03G15/08—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer
    • G03G15/09—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer using magnetic brush

Definitions

  • This invention relates to an electrostatographic developing apparatus and process, and in particular to an electrostatographic developing apparatus including apparatus including a developer applicator for applying developer material to an electrostatic latent image on a flexible imaging surface, the developer material comprising magnetically attractable carrier particles and toner particles, means within the applicator for establishing a magnetic field around the applicator for bringing the developer material to the development zone, the magnetic field having a region of reduced strength in the development zone, as compared with its strength at the entrance and exit of said zone, and means for establishing an electric field between the applicator and the imaging surface in the development zone.
  • apparatus including a developer applicator for applying developer material to an electrostatic latent image on a flexible imaging surface, the developer material comprising magnetically attractable carrier particles and toner particles, means within the applicator for establishing a magnetic field around the applicator for bringing the developer material to the development zone, the magnetic field having a region of reduced strength in the development zone, as compared with its strength at the entrance and exit of said zone, and means for
  • Image field neutralization can occur, however, if there is a sufficiently high developer flow rate and multiple development rollers. Image field neutralization is herein defined to occur when the potential due to a layer of charged toner deposited on the imaging member is equal but opposite to the potential due to the charged imaging member. In the absence of a bias on the development roller, image neutralization produces a zero development electric field.
  • the charge density of the toner layer is less than the image charge density for the condition of image field neutralization.
  • the difference in charge density depends on the relative thicknesses of the imaging member and toner layer. If the thickness of the charged toner layer is much less than the imaging member, image field neutralization occurs when the toner charge density neutralizes the image charge density.
  • the solid area deposition is not limited by a layer of net-charged developer near the imaging member, since this charge is dissipated by conduction to the development roller.
  • the solid area deposition is, however, limited by image field neutralization, provided there is sufficient toner available at the ends of the developer brush, while the toner supply is limited to the ends or tips of the bristles, since tone cannot be extracted from the bulk of the developer where the high developer conductivity collapses the electric field within the developer, at any location, and confines it to the region between the latent image and the developer.
  • the solid area deposition is limited by toner supply at low toner concentrations.
  • the toner supply is limited to a layer of carrier material adjacent to the image bearing member since the magnetic field stiffens the developer and hinders developer mixing in the development zone.
  • IBM TDB Vol. 17 No. 9 of Feb. 1975 pages 2684-6 discloses a magnetic brush development system using a reduced field in part of the development zone and variations in magnetic field to cause turbulence and tumbling of the carrier to free toner and make it available for copy development.
  • the present invention is intended to provide such an apparatus, and is characterised in that the flexible imaging member is a tensioned member which is deflected by a portion of the surface of the- applicator so as to be spaced from the applicator in use by at least one layer of carrier particles, the arrangement being such that there is relative movement between the applicator and the imaging surface, whereby. the carrier particles therebetween are caused to make rotational movements, such movements, together with the electric field, producing a migration of toner particles towards the imaging surface.
  • the invention also provides an electrostatographic development process comprising applying developer material by means of an applicator to an electrostatic latent image on a flexible imaging member, the developer material comprising magnetically attractable carrier particles and toner particles, establishing a magnetic field around the applicator for bringing the developer material to the development zone, the magnetic field having a reduced strength region in the development zone as compared with its strength at the entrance and exit of said zone, and applying an electric field between the applicator and the imaging member in the development zone, characterised by deflecting a tensioned, flexible imaging member around a portion of the surface of the applicator so that it is spaced from the applicator by at least one layer of carrier particles, and causing relative movement between the applicator and the imaging surface so that the carrier particles therebetween make rotational movements, such movements, together with the electric field, producing a migration of toner particles towards the imaging surface.
  • the toner migration rate depends generally on the amount of developer agitation, the magnitude of the electrical field applied to the development zone, and the length of the development zone, which depends on the amount or degree of deflection of the flexible imaging member.
  • the magnitude of the electric field is inversely proportional to the developer thickness, and directly proportional to the difference in potential between the charged imaging member and the bias on the development roller.
  • the electric field potential is about 300 volts across the developer layer.
  • the development electric field is 300 volts across 0.5 mm; i.e., 600 V/mm.
  • degree of developer agitation is proportional to the shear rate and development time.
  • increased developer agitation is obtained when the developer layer is thin, for example, one layer of carrier particles and the development zone is long, which length ranges from 0.5 cm to 5 cm with a preferred length being between 1 cm and 2 cm. However, lengths outside these ranges may be used providing the objectives of the present invention are accomplished.
  • the magnetic field is generally less than 150 gauss and preferably less than 20 gauss. If desired, ferromagnetic material such as steel can be used to shape and reduce the magnetic field in the development zone.
  • a development system based on a self-agitated development zone has a number of advantages over conventional systems, for example, solid area and line development is at its maximum, since the toner charge neutralizes the fields from the image charge; and development, limited by image field neutralization enables the present system to develop in one embodiment low voltage images associated with thin image bearing members.
  • the amount of toner deposited on the imaging bearing member is substantially independent of the spacing between the development roll, and the image bearing member, within the range of 0.05 millimeters to 1.5 millimeters.
  • FIG. 1 Illustrated in Figure 1 is the development zone of the apparatus of the present invention designated 10, which is comprised of a positively charged image bearing member 1, negatively charged toner particles 2, attached to positively charged carrier particles 3, a developer transporting member 4, which also serves as a development electrode, toner depleted layer D, which layer has carrier particles containing a positive charge, this layer having less tone on the carrier than the adjacent carrier layers, C, B, and A, a biased voltage source 6, and a toner developed layer 7.
  • A, B, C, and D designate layers of developer comprised of carrier and toner particles.
  • the image bearing member 1, and developer transporting member 4, in this embodiment are moving in the direction shown by the arrows 5 and 5a. In this illustration the transporting member 4 is moving at a greater speed than the image bearing member 1.
  • the shape of the carrier particles is not necessarily completely spherical as shown, that is, most carrier particles are non-spherical with surfaces that can be jagged or textured. Further, the toner particles 2 can be charged positively, and the carrier particles 3, can be charged negatively. Such a developer would be useful in systems where the image bearing member is charged negatively.
  • the arrows within the carrier particles 3, indicate that such particles are moving in both directions, first in one direction, for example, slightly to the right than in another direction, slightly to the left. While moving in one direction, then another, the particles are also rotating as more clearly illustrated in Figures 1A-1C. This movement or agitation which results in improved development of images, is caused primarily by the movement of the imaging member 1, and developer transporting member 4, as indicated herein.
  • the development electrode 4 is moving at a surface speed which is faster than the speed of the imaging member 1, both the development electrode and the imaging member moving in the same direction.
  • This relative motion between the development electrode 4 and imaging member 1 causes the developer which is comprised of toner particles 2, and carrier particles 3, to be agitated by a shearing action.
  • the shearing action causes movement of the carrier particles 3, that is, the carrier particles rotate in both a clockwise and counterclockwise direction, but on the average tend to rotate in a counterclockwise direction.
  • the developer agitation the development electric field, and deflection of the flexible imaging member allow toner particles 2 adhering to the carrier particles 3 to migrate towards the imaging member 1.
  • the toner particles closest to the imaging member 1 are deposited on the imaging surface, therefore the carrier particles adjacent the imaging surface lose some of the toner particles adhering thereto, which toner particles must be replaced in order to continue to achieve high quality development, and in particular, solid area development. In order for this to occur, toner particles must be transferred from adjacent carrier layers, and this transfer is caused on a continual and constant basis by the shearing action mentioned hereinbefore.
  • Maximum agitation which is preferred, is obtained when the magnetic field in development zone is low, and the developer layer is thin, that is, ranging in thickness from about 0.05 millimeters to about 1.5 millimeters and preferably from about 0.4 millimeters to 1.0 millimeters. by low magnetic field it is meant that the field strength is generally less than 150 gauss.
  • toner migration results in a toner depleted layer D and although the toner depleted carrier is positively charged, the effect of this charge layer on the toner motion in the bulk of the developer is small due to the proximity of the layer to the development electrode.
  • both solid area and line development will cease when the charge on the imaging member is essentially neutralized with charged toner. Accordingly, the availability of toner for solid area development is enhanced for a self-agitated two-component insulative development system, and when the electrostatic force und development agitation are sufficient, nearly all of the toner in the developer bulk will deposit on the image bearing member.
  • the degree of developer agitation is defined by the product of the shear rate and development time.
  • the average shear rate is equal to the absolute value of the difference in the devopment roller or electrode velocity, Vp, and imaging member velocity, V,, divided by the developer thickness, L, i.e., the average shear rate equals
  • the development time is equal to the development zone length, W, divided by the absolute value of the development roller speed, V R i.e. the develoment time equals W/ V R
  • V the degree of developer agitation is equal to or where V is equal to V ⁇ /V and is positive or negative when the development roller or electrode moves in the same or opposite direction to the image bearing member respectively.
  • the quantity 1-1/V is typically near a value of 1 in which case the degree of developer agitation is approximated by W/L, i.e., the ratio of the developer zone length to the developer layer thickness.
  • W the degree of developer agitation
  • the developer agitation ranges from 2 to 1000 units and preferably from 10 to 50 units.
  • Figure 1A, 1B, and 1 C there is shown in some detail in Figure 1A, 1B, and 1 C, what is occurring at each of the different layers of developer, designated A, B, and C when employing the imaging process und apparatus of the present invention.
  • the numerical and letter designations illustrate the identical components as described with reference to Figure 1, with the addition that Z represents an area or zone of the carrier particles which have been depleted of toner particles.
  • Figure 1 A there is illustrated a carrier particle 3, of layer A, which is depleted of toner particles 2, in the area or zone Z; while Figure 1 B, illustrates the transfer of toner particles 2, from carrier particle 3, of layer B, to carrier particle 3, of layer A, resulting in a toner depleted area or zone Z, on carrier particle 3, layer B.
  • 8 represents the interface area between carrier particles.
  • toner particles 2 transfer from carrier particles 3 of layer C, to carrier particles 3, of layer B and there results a toner depleted layer or zone Z, on carrier particle 3, layer C.
  • the carrier particles of layers A, and B for example, reference Figure 1 B come into contact with each other, forcing the toner particles 2 between the carrier 3 of layers A and B, to in effect decide what carrier particles to remain with; those of layer A, or those of layer B.
  • the toner particles move from the carrier particles of layer B, to the carrier particles of layer A, thereby replacing the depleted toner particles on the carrier of layer A in order that such particles will be available to deposit on the imaging member and cause development.
  • zone Z no toner particles are present, since the electrical fields transferred the toner from the carrier beads, for example the carrier beads of layer A, to the imaging member 1. This is caused primarily because of the rocking motion of the carrier beads 3, which motion further causes a positive charge to be contained on the carrier particles.
  • the apparatus and process of the present invention are employed in an imaging system, there is provided increased line and increased solid area development even when the developers have a rather low toner concentration in comparison to the developers used in conventional systems.
  • the minimum toner concentration for acceptable solid area development depends on several factors including the ratio of the development roller speed to photoreceptor speed and the degree of developer agitation which depends on the magnetic field strength, the development zone length and the spacing between the imaging member and the development roll.
  • the solid area development is 0.5 mg/cm 2 for a development voltage of 300 volts, a speed ratio of 3, a magnetic field less than 20 gauss, a development zone length of 3.3 cm and a developer layer thickness of 0.5 mm.
  • Illustrated in Figure 2 is a conventional magnetic brush development system, wherein two component insulative developer material is used, this illustration being provided in order to more clearly point out the advantages of the present invention in some respects over conventional magnetic brush systems.
  • the imaging system of Figure 2 is comprised of an imaging member 1, negatively charged toner particles 2, positively charged carrier particles 3, development electrode 4, developed toner layer 7, image developer interface 9, and a biased voltage source 6.
  • the developer, that is, toner plus carrier is a two-component insulative developer as described with reference to Figure 1.
  • the magnetic field causes the developer to form bead chains or bristles which are rigid or stiff.
  • developer agitation is limited to a region near the image developer interface 9, as no agitation is occurring with the other developer particles, transfer of toner from the carrier particles does not result, thereby in effect rendering these other developer particles substantially useless.
  • the charge density on the developer layer A is equal to the negative of the toner charge density 7 on the image bearing member, divided by the ratio of the development roll speed to imaging member speed.
  • the electric field from the layer of charged developer A is highly effective in reducing the net electric field at the image developer interface. This electric field becomes zero despite the fact that the image charge is not neutralized by toner charge.
  • Solid area development with insulative developers is limited by field collapse even though a sufficient supply of toner might be contained within the first layer of developer A. Furthermore, the solid area development rate decreases when the toner concentration is low and the stiffening of developer by the magnetic field aids in limiting the supply of toner.
  • FIG. 3 Illustrated in Figure 3 is an enlarged view of a development zone containing conductive developer.
  • 1 represents the imaging member
  • 2 represents negatively charged toner particles
  • 3 represents positively charged carrier particles
  • 4 is a development electrode
  • 6 represents the voltage source
  • 7 represents the developed toner layer.
  • the charged image bearing member induces an opposite charge in the layer of developer adjacent to the image.
  • Toner in the developer (within the layer of developer) is inaccessible since the electric field is zero because of the high developer conductivity, and the magnetic field stiffens the developer and reduces the migration of toner to the image bearing member, that is, toner particles are not transferred from one layer of carrier particles, such as B to another layer of carrier particles such as A, and thus no development will occur after a short period of time.
  • toner development onto the imaging member only occurs from the first bead layer 1.
  • the amount of toner transferred from one layer of carrier particles to another layer of carrier particles is substantially zero, whereas with the system of the present invention, toner particles are being constantly replenished to the first layer of carrier particles, which replenishment is important for efficient solid area development, and efficient development of lines.
  • FIG 4 represents an electroded cell for measuring the development properties of developer under controlled conditions.
  • the developer is located in a conducting tray 11 that can be biased with a voltage supply.
  • the upper electrode 12 is coated with an insulating material such as a polyester or photoreceptor layer 13, which is contacted with the developer 14, when a bias is applied to the developer tray 11. Movement of the electrode as indicated by the arrow causes agitation of the developer layer.
  • the toner density developed onto layer 13 is measured by weighing the electrode assembly before and subjecting the assembly to an air jet for the purpose of removing loose toner particles.
  • the toner weight per unit area was 0.23 mg/cm 2 which was deposited on an insulation overcoated electrode 12 under the following conditions; a developer bed thickness of 1.5 mm, an applied voltage of 600 volts and an electrode displacement of 1.9 cm.
  • the developed toner mass decreased to 0.09 mg/cm 2 .
  • the larger developed toner mass for magnetic field free conditions is attributed to increased developer agitation.
  • the toner weight developed on the image bearing member is proportional to the ratio of the development roll speed to the imaging member speed. Thus when this ratio is 2, and under the conditions stated herein, the toner weight per unit area of 0.46 mg/cm 2 would be obtained on the image bearing member. This would result in an acceptable reflective optical density of ( I ).
  • the solid area development increases since the development electric field is higher.
  • the developed toner density is 0.28 mg/cm 2 compared to the 0.09 mg/cm 2 obtained for a developer thickness of 1.5 millimeters.
  • the developed density increases to 0.80 mg/cm 2 compared to the 0.23 mg/cm 2 obtained when the developer thickness is 1.5 mm.
  • the increase in solid area development for the magnetic field-free case is due to a high agitation of the thin developer layer. The agitation increases the toner supply and displaces the developer net-charge towards the development electrode. Increased solid area development is thus obtained by making the developer layer thin and the development zone magnetic field free.
  • Self-agitation of developer in the development zone requires relative motion between the developer transporting electrode member and the image bearing member.
  • the electrode When the electrode is brought into contact with the developer without lateral movement, a small quantity of toner is transferred to the electrode when a voltage is applied and the electrode is removed.
  • the electrode When the electrode is displaced while in contact with the developer, increased development occurs since the developer is agitated by the relative motion, the degree of agitation depending on the magnitude of the relative displacement which is the product of the relative speed and displacement time.
  • a high solid area development rate is achieved when the development zone is thin, magnetic field free, and long, such development systems containing a means of flowing fresh developer through the development zone. Since the developer transporting roller is typically moving at a speed faster than the image bearing member, developer will tend to accumulate at the entrance to the magnetic field free zone. To ensure good developer flow, a strong magnetic field at the zone entrance helps to establish proper developer flow through the succeeding low magnetic field region. A strong magnetic field at the exit region of the developer zone reduces carrier adhesion to the image bearing member, and prevents scavenging of the toner in solid areas, since as the electrode spacing increases the fields in the solid areas decrease.
  • FIG. 5 Illustrated in Figure 5 is a development system that incorporates the features of a thin and low magnetic field development zone, as well as a high magnetic field at the entrance and exit regions of the development zone.
  • a flexible image bearing member 1 and a development roller 15, containing magnets 16 therein, attached to a core or "keeper" 17.
  • the roller 15 obtains developer 18 (toner and carrier) when it passes through the development sump 19.
  • Metering blade 20 is used to control the thickness of the developer material.
  • Region (21) allows developer to remain on the roller 15, while region 22 insures good developer flow and region 23 prevents developer from contacting the latent image surface as the electrode spacing increases.
  • developer agitation occurs in the region of low magnetic field
  • the image bearing member can be a belt photoreceptor or an electroreceptor (charge patterns generated by electrical means; such as in electronic printers), both of which can be partially wrapped around the developer-covered development roller.
  • the developer layer provides the spacing between the development roller and image bearing member. Steel shunting inside the development roller is used to reduce the magnetic field between the magnetic poles at the entrance and exit regions. Designating v as the ratio of the development roller velocity and imaging member velocity, good developer flow is obtained when the value of v is greater than zero and less than -1. If v is greater than -1, but less than zero inadequate developer flow results in the development zone.
  • a thin layer of developer is applied to the development roller with the aid of the metering blade 20, closely spaced from the development roller.
  • the uniformity of the developer thickness is determined by the dimensional accuracy of the roller and the straightness of the metering blade.
  • the developer layer thickness is approximately equal to the metering blade gap setting, while when the metering blade is located where the magnetic field is tangential to the roll, the developer layer thickness is approximately 0.4 of the metering gap setting.
  • a reduced developer layer thickness is obtained because the developer bead chains tangential to the development roll are magnetically attracted to the mass of developer peeled away by the metering blade. Developer metering in a tangential magnetic field enables one to obtain a thin developer layer of approximately 0.5 mm when the metering gap is set at 1.2 millimeters.
  • Figure 6 is a graph of data displaying the solid area development characteristics of the self-agitated development system depicted in Figure 5.
  • This figure also includes data obtained with a conventional single development roll magnetic brush development system.
  • the curve G represents data obtained for self-agitated development with a 0.4 mm gap, (distance between imaging member and transporting member) while curve H represents data obtained with a conventional magnetic brush system, 1.5 mm gap.
  • the same developer with a toner concentration of 2.7 percent and fluoropolymer coated ferrite beads was used for both systems operating at a speed ratio v of 2.
  • Increased development with the self-agitated system, curve G is attributed to the thin developer layer (0.4 mm), low magnetic field (20 gauss) and long development zone (3 cm).
  • curve H the gap between the photoreceptor and development roller is maintained at 1.5 mm.
  • the magnetic field is 500 gauss over the development zone length of 0.5 cm.
  • the reflection image density for the self-agitated system, curve G is greater than 1, while for conventional systems at 200 volts the reflection image density, curve H, is less than 0.2.
  • the spacing between hhe development roller and image bearing member is determined by the developer layer thickness. As indicated this spacing typically ranges from about 0.05 millimeters to about 1.5 millimeters and preferably from about 0.4 millimeters to about 1.0 millimeters.
  • the magnetic field within the central area of the development zone is generally less than 150 gauss and preferably less than 20 gauss, while the magnetic field at the entrance and exit regions of the development zone is radially directed and typically 300 to 800 gauss, with magnetic poles being of like polarity.
  • the magnetic field profile is obtained by a suitable choice of permanent magnets.
  • steel shunting inside the development roll can provide magnetic field shaping at the surface of the development roll.
  • the length of the development zone depends on the configuration of the image bearing member and developer transport member.
  • the image bearing member is a belt partially wrapped around a development roller with a diameter which is typically 3.8 cm to 6.4 cm.
  • the length of contact between the developer and image bearing member ranges from 0.5 cm to 5 cm.
  • the preferred length is 1 cm to 2 cm. Idler rolls positioned against the backside of the belt can be used to alter the belt path.
  • Figure 7 illustrates one example of a self-agitated development system design that incorporates the use of an idler roll.
  • the purpose of the idler roll, or rolls, is to allow freedom in the position of the zones, such as the paper transport zone for example in an electrophotographic or similar apparatus.
  • the numerical designations 15, 16, 17, 19, 21, 22 and 23 represent the same components as described in Figure 5.
  • the idler roll in the region 22 is designated 24. It is understood that a second idler roll could be placed near the region 23 to alter the path of the imaging member without causing a change in the operation of the development system.
  • the system shown in Figure 7 is operating in a mode in which the development roller and imaging member are moving in opposite directions.
  • FIG. 8 there is illustrated an electrophotographic printing machine employing an imaging member 1 having a photoconductive surface deposited on a conductive substrate, such as aluminized Mylar (Trademark), which is electrically grounded.
  • the imaging member 1, or the photoconductive surface can be comprised of numerous suitable materials as described herein.
  • the photoconductive material is comprised of a transport layer containing small molecules of N,N,N',N'-tetraphenyt-[l,1'-biphenyt] 4-4'-diamine, or similar diamines (m-TBD) dispersed in a polycarbonate and a generation layer of trigonal selenium.
  • Imaging member 1 moves in the direction of arrow 27 to advance successive portions of the photoconductive surface sequentially through the various processing stations disposed about the path of movement thereof.
  • the imaging member is entrained about a sheet-stripping roller 28, tensioning system 29, and drive roller 30.
  • Tensioning system 29 includes a roller 31 having flanges on opposite sides thereof to define a path through which member 1 moves.
  • Roller 31 is mounted between guides 22 attached to springs 32. Springs 32 are tensioned such that roller 31 presses against the imaging belt member 1. In this way, member 1 is placed under the desired tension. The level of tension is relatively low permitting member 1 to be relatively easily deformed.
  • drive roller 30 is mounted rotatably and in engagement with member 1. Motor 33 rotates roller 30 to advance member 1 in the direction of arrow 27. Roller 30 is coupled to motor 33 by suitable means such as a belt drive. Sheet-stripping roller 28 is freely rotatable so as to readily permit member 1 to move in the direction of arrow 27 with a minimum of friction.
  • a corona generating device indicated generally by the reference numeral 34, charges the photoconductive surface of imaging member 1 to a relatively high, substantially uniform potential.
  • the charged portion of the photoconductive surface is advanced through exposure station I.
  • An original document 35 is positioned face down upon transparent platen 36.
  • Lamps 37 flash light rays onto original document 35.
  • the light rays reflected from original document 35 are transmitted through lens 38 forming a light image thereof.
  • Lens 38 focuses the light image onto the charged portion of the photoconductive surface to selectively dissipate the charge thereon. This records an electrostatic latent image on the photoconductive surface which corresponds to the informational areas contained within original document 35.
  • imaging member 1 advances the electrostatic latent image recorded on the photoconductive surface to development station J.
  • a self-agitated development system indicated generally by the reference numeral 39, advances a developer material into contact with the electrostatic latent image.
  • the self-agitated development system 39 includes a developer roller 40 which transports a layer of developer material comprising magnetic carrier particles and toner particles into contact with imaging member 1.
  • developer roller 40 is positioned such that the brush of developer material deforms imaging member 1 in an arc such that member 1 conforms at least partially, to the configuration of the developer roller.
  • the electrostatic latent image attracts the toner particles from the carrier granules forming a toner powder image on the photoconductive surface of member 1.
  • the development roller 40 returns the developer material to the sump of development system 39 for subsequent re-use.
  • the detailed structure of the development system 39 has been described herein, with reference to Figures 1, 1A, 1B, 1C, 5 and 7.
  • Imaging member 1 then advances the toner powder image to transfer station K.
  • a sheet of support material 44 is moved into contact with the toner powder image.
  • the sheet of support material 44 is advanced to transfer station K by a sheet feeding apparatus (not shown).
  • the sheet feeding apparatus includes a feed roll contacting the uppermost sheet of a stack of sheets. The feed roll rotates so as to advance the uppermost sheet from the stack into a chute. The chute directs the advancing sheet of support material into contact with the photoconductive surface of member 1 in a timed sequence so that the toner powder image developed thereon contacts the advancing sheet of support material at transfer station K.
  • Transfer station K includes a corona generating device 46 which sprays ions onto the backside of sheet 44. This attracts the toner powder image from the photoconductive surface to sheet 44. After transfer, sheet 44 moves in the direction of arrow 48 onto a conveyor (not shown) which advances sheet 44 to fusing station L
  • Fusing station L includes a fuser assembly, indicated generally by the reference numeral 50, which permanently affixes the transferred toner powder image to sheet 44.
  • fuser assembly 50 includes a heated fuser roller 52 and a back-up roller 54.
  • Sheet 44 passes between fuser roller 52 and backup roller 54 with the toner powder image contacting fuser roller 52. In this manner, the toner powder image is permanently affixed to sheet 44.
  • a chute guides the advancing sheet 44 to a catch tray for subsequent removal from the printing machine by the operator.
  • Cleaning station M includes a rotatably mounted fibrous brush 56 in contact with the photoconductive surface. The particles are cleaned from the photoconductive surface by the rotation of brush 56 in contact therewith. Subsequent to cleaning, a discharge lamp (not shown) floods photoconductive surface 1 with light to dissipate any residual electrostatic charge remaining thereon prior to the charging thereof for the next successive imaging cycle.
  • Illustrative examples of the photoconductive surface of flexible image bearing member 1 include inorganic and organic photoreceptor materials such as for example amorphous selenium, selenium alloys, including alloys of selenium-tellurium, selenium arsenic, selenium antimony, selenium-tellurium-arsenic, cadmium sulfide, zinc oxide, polyvinylcarbazole, and layered organic photoreceptors, such as those containing an injecting contact, carbon dispersed in a polymer, overcoated with a transport layer, which in turn is overcoated with a generating layer, and finally an overcoating of an insulating organic resin, such as those described in U.S. Patent 4,251,612.
  • inorganic and organic photoreceptor materials such as for example amorphous selenium, selenium alloys, including alloys of selenium-tellurium, selenium arsenic, selenium antimony, selenium-tellurium-ars
  • organic photoreceptor materials include, 4-dimethylaminobenzylidene, benz- hydrazide; 2-benzylidene-amino-carbazole, 4-dimethylamino-benzylidene, polyvinyl carbazole; (2-nitro-benzylidene)-p-bromo-aniline; 2,4-diphenyl quinazoline, 1,2,4-triazone; 1,5-diphenyl-3-methyl pyrazoline 2-(4'-dimethyl- amino phenyl) benzoxazole; 3-amino-carbazole; polyvinylcarbazole-trinitrofluorenone charge transfer complex; phthalocyanines and mixtures thereof, and the like.
  • Illustrative examples of materials for the transporting member 4 include virtually any conducting material made for this purpose, such as stainless steel, aluminum and the like.
  • Texture in the development roller provides traction necessary for good developer transport from the developer sump and through the development zone.
  • the development roll texture is obtained by one of several methods involving flame-spray treating, etching, knurling, etc.
  • the developer material is comprised of a toner resin, colorant or pigment, and a suitable insulating magnetic carrier material.
  • insulating as used throughout the description, is meant sufficiently non-conducting for charge not to flow from the transport member to the ends of the carrier particles nearest the image bearing member within a time that is less than the development time. In one embodiment thus the range of development times is calculated as follows:
  • any suitable material may be employed as the toner resin in the system of the present invention, typical of such resins are polyamides, epoxies, polyurethanes, vinyl resins and polymeric esterification products of a dicarboxylic acid and a diol comprising a diphenol.
  • Any suitable vinyl resin may be employed in the toners of the present system including homopolymers or copolymers of two or more vinyl monomers.
  • vinyl monomeric units include: styrene, p-chloro-styrene vinyl naphthalene, ethylenically unsaturated mono olefins such as ethylene, propylene, butylene, isobutylene and the like; vinyl esters such as vinyl chloride, vinyl bromide, vinyl fluoride, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate and the like; esters of alphamethylene aliphatic monocarboxylic acids such as methyl acrylate, ethyl acrylate, n-butylacrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl alphachloroacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate and the like; acrylonitrile,
  • toner resins containing a relatively high percentage of styrene are preferred since greater image definition and density is obtained with their use.
  • the styrene resin employed may be a homopolymer of styrene or styrene homologs of copolymers of styrene with other monomeric groups containing a single methylene group attached to a carbon atom by a double bond. Any of the above typical monomeric units may be copolymerized with styrene by addition polymerization.
  • Styrene resins may also be formed by the polymerization of mixtures of two or more unsaturated monomeric materials with a styrene monomer.
  • the addition polymerization technique employed embraces known polymerization techniques such as free radical, anionic and cationic polymerization processes. Any of these vinyl resins may be blended with one or more resins if desired, preferably other vinyl resins which insure good triboelectric properties and uniform resistance against physical degradation. However, non-vinyl type thermoplastic resins may also be employed including resin modified phenolformaldehyde resins, oil modified epoxy resins, polyurethane resins, cellulosic resins, polyether resins and mixtures thereof.
  • esterification products of a dicarboxylic acid and a diol comprising a diphenol may be used as a preferred resin material for the toner composition of the present invention.
  • These materials are illustrated in U.S. Patent No. 3,655,374, the diphenol reactant being of the formula as shown in column 4, beginning at line 5 of this patent and the dicarboxylic acid being of the formula as shown in column 6 of the above patent.
  • the alkyl pyridinium compound is used and 10 percent by weight of pigment such as carbon black, about 85 percent by weight of resin material is used.
  • Optimum electrophotographic resins are achieved with styrene butylmethacrylate copolymers, styrene vinyl toluene copolymers, styrene acrylate copolymers, polyester resins, predominantly styrene or polystyrene based resins as generally described in U.S. Reissue 24,136 to Carlson and polystyrene blends as described in U.S. Patent No. 2,788,288 to Rheinfrank and Jones.
  • the toner resin particles can vary in diameter, but generally range from about 5 micronmeters to about 30 micronmeters in diameter, and preferably from about 10 micrometers to about 20 micrometers.
  • any suitable pigment or dye may be employed as the colorant for the toner particles, such materials being well known and including for example, carbon black, nigrosine dye, aniline blue, calco oil blue, chrome yellow, ultramarine blue, DuPont oil red, methylene blue chloride, phthalocyanine blue and mixtures thereof.
  • the pigment or dye should be present in sufficient quantity to render it highly colored so that it will form a clearly visible image on the recording member.
  • the toner may comprise a black pigment such as carbon black or a black dye such as Amaplast black dye available from the National Aniline Products Inc.
  • the pigment is employed in amounts from about 3 percent to about 20 percent by weight based on the total weight of toner, however, if the toner color employed is a dye, substantially smaller quantities of the color may be used.
  • charge control agents primarily for the purpose of imparting a positive charge to the toner resin.
  • charge control agents includes quaternary ammonium compounds as described in U.S. Patent 3,970,571, and alkyl pyridinium halides such as cetyl pyridinium chloride, as described in U.K. Patent Application No. 7916357, publication No. 2023298.
  • any suitable insulating magnetic carrier material can be employed as long as such particles are capable of triboelectrically obtaining a charge of opposite polarity to that of the toner particles.
  • the carriers can be selected so that the toner particles acquire a charge of a positive polarity and include materials such as steel, nickel, iron, ferrites, magnetites and the like.
  • the carriers can be used with or without a coating, examples of coatings including fluoropolymers such as polyvinylidene fluoride, methyl terpolymers and the like. Also nickel berry carriers as described in U.S.
  • Patents 3,847,604 and 3,767,598 can be employed, provided they are rendered insulating in accordance with the process defined herein, these carriers being nodular carrier beads of nickel characterized by a surface of reoccurring recesses and protrusions providing particles with a relatively large external area.
  • the carrier particles, or their cores are of materials that have a conductivity which is such as to dissipate net charge accumulation from the development process such as for example steel shot carriers.
  • the diameter of the coated carrier particle ranges from about 50 to about 1000 micrometers, thus allowing the carrier particle to possess sufficient density and inertia to avoid adherence to the electrostatic images during the development process.
  • the carrier may be employed with the toner composition in any suitable combination, however, best results are obtained when about 1 part toner is used and about 10 to about 4000 parts by weight of carrier.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Dry Development In Electrophotography (AREA)
  • Magnetic Brush Developing In Electrophotography (AREA)

Claims (9)

1. Appareil de développement électrostato- graphique comprenant un applicateur (15) de révélateur destiné à appliquer un matériau révélateur (18) à une image électrostatique latente sur une surface (1) flexible de formation d'image, le matériau révélateur comprenant des particles (3) de porteur et des particles de toner (2) attirables magnétiquement, un moyen (16) à l'intérieur de l'applicateur afin d'établir un champ magnétique autour de l'applicateur dans le but d'amener le matériau révélateur dans la zone de développement, le champ magnétique comportant une région (21) où règne une intensité réduite dans la zone de développement, par rapport à son intensité à l'entrée et à la sortie de ladite zone, et un moyen pour établir un champ électrique entre l'applicateur et la surface de formation d'image dans la zone de développement, caractérisé en ce que l'élément (1) flexible de formation d'image est un élément soumis à une tension qui est dévié par une partie de la surface de l'applicateur (15) de manière à être espacé de l'applicateur pendant l'utilisation suivant au moins une couche de particules de porteur, l'agencement étant tel qu'il y a un mouvement relatif entre l'applicateur et la surface de formation d'image, d'où il résulte que les particules de porteur situées entre sont amenées à faire des mouvements de rotation, de tels mouvements, en même temps que le champ électrique, produisant une migration des particules de toner vers la surface (1) de formation d'image.
2. Appareil selon la revendication 1, où l'élément (1) de formation d'image est espacé de l'applicateur (15) dans la zone de développement suivant un interstice compris entre 0,05 et 1,5 mm.
3. Applicateur selon la revendication 2, où l'interstice est compris entre 0,4 et 1,0 mm.
4. Appareil selon l'une quelcoque des revendications 1 à 3, où l'applicateur (15) est disposé de manière à se déplacer à une vitesse comprise entre 6 cm/s et 100 cm/s et la surface (1) de formation d'image est disposée de manière à se déplacer à une vitesse comprise entre 5 cm/s et 50 cm/s.
5. Appareil selon l'une quelconque des revendications 1 à 4, où le champ magnétique dans la région où règne une intensité réduite est inférieur à 150 gauss.
6. Appareil selon l'une quelconque des revendications 1 à 5, où le champ électrique dans la zone de développement est d'environ 600 V/mm.
7. Appareil selon l'une quelconque des revendications 1 à 6, où la zone de développement a une longueur comprise entre 0,5 et 5 cm.
8. Appareil selon l'une quelconque des revendications 1 à 7, où l'applicateur (15) est un rouleau monté en rotation autour d'un jeu fixe d'aimants (16) afin d'établir le champ magnétique, et la surface (1) de formation d'image est la surface d'un ruban flexible disposé de manière à être déviée par le rouleau pour venir en contact avec le matériau révélateur sur la surface du rouleau dans la zone de développement.
9. Procédé de développement électrostato- graphique comprenant l'application de matériau révélateur (18) au moyen d'un applicateur (15) sur une image électrostatique latente sur un élément (1) flexible de formation d'image, le matériau révélateur comprenant des particules de porteur et des particules de toner attirables magnétiquement, l'établissement d'un champ magnétique autour de l'applicateur pour amener le matériau révélateur dans la zone de développement, le champ magnétique ayant une region (21) d'intensité réduite dans la zone de développement par rapport à son intensité à l'entrée et à la sortie de ladite zone, et l'application d'un champ électrique entre l'applicateur et l'élément de formation d'image dans la zone de développement, caractérisé par la déviation d'un élément (1) flexible de formation d'image, soumis à une tension, autour d'une partie de la surface de l'applicateur (15) de sorte qu'il se trouve espacé de l'applicateur d'au moins une couche de particules de porteur, et la provocation d'un mouvement relatif entre l'applicateur et la surface de formation d'image de sorte que les particules de porteur se trouvant entre subissent des mouvement de rotation, de tels mouvements, avec le champ électrique, produisant une migration des particules de toner vers la surface (1) de formation d'image.
EP81302440A 1980-06-02 1981-06-02 Appareil et procédé de développement électrostatographique Expired EP0041399B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT81302440T ATE11604T1 (de) 1980-06-02 1981-06-02 Elektrostatographisches entwicklungsgeraet und verfahren.

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US15588980A 1980-06-02 1980-06-02
US15580480A 1980-06-02 1980-06-02
US155889 1980-06-02
US155804 1980-06-02

Publications (3)

Publication Number Publication Date
EP0041399A2 EP0041399A2 (fr) 1981-12-09
EP0041399A3 EP0041399A3 (en) 1982-02-03
EP0041399B1 true EP0041399B1 (fr) 1985-01-30

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EP81302440A Expired EP0041399B1 (fr) 1980-06-02 1981-06-02 Appareil et procédé de développement électrostatographique

Country Status (7)

Country Link
EP (1) EP0041399B1 (fr)
AU (1) AU547726B2 (fr)
BR (1) BR8103447A (fr)
CA (1) CA1169716A (fr)
DE (1) DE3168598D1 (fr)
ES (2) ES8304674A1 (fr)
MX (1) MX153982A (fr)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4544618A (en) * 1982-01-18 1985-10-01 Xerox Corporation Development process utilizing conductive materials
JPS604965A (ja) * 1983-06-13 1985-01-11 ゼロツクス・コ−ポレ−シヨン 電子写真式複写機の現像装置
US4637973A (en) * 1984-11-15 1987-01-20 Konishiroku Photo Industry Co., Ltd. Image forming process for electrophotography
EP0371735B1 (fr) * 1988-11-28 1994-01-19 Mita Industrial Co., Ltd. Procédé de développement à brosse magnétique
EP0371737B1 (fr) * 1988-11-28 1994-01-19 Mita Industrial Co., Ltd. Procédé de développement pour la formation d'images à haute qualité
DE68912286T2 (de) * 1988-11-28 1994-04-28 Mita Industrial Co Ltd Magnetbürstenentwicklungsverfahren.

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0032424A1 (fr) * 1980-01-11 1981-07-22 Xerox Corporation Dispositif de développement d'images latentes

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3900001A (en) * 1971-05-25 1975-08-19 Xerox Corp Developing apparatus
US3945343A (en) * 1975-03-24 1976-03-23 General Electric Company Magnetic brush for use in magnetic printing
JPS5948387B2 (ja) * 1977-01-07 1984-11-26 キヤノン株式会社 現像装置
JPS5569155A (en) * 1978-11-20 1980-05-24 Hitachi Ltd Developing method of electrostatic latent image

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0032424A1 (fr) * 1980-01-11 1981-07-22 Xerox Corporation Dispositif de développement d'images latentes

Also Published As

Publication number Publication date
ES519510A0 (es) 1984-05-16
EP0041399A3 (en) 1982-02-03
CA1169716A (fr) 1984-06-26
ES8405167A1 (es) 1984-05-16
ES502718A0 (es) 1983-02-01
ES8304674A1 (es) 1983-02-01
AU7117181A (en) 1981-12-10
AU547726B2 (en) 1985-10-31
DE3168598D1 (en) 1985-03-14
BR8103447A (pt) 1982-02-24
EP0041399A2 (fr) 1981-12-09
MX153982A (es) 1987-03-18

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