US3838054A - Electrostatic developer composition containing both rough and smooth carrier particles - Google Patents

Electrostatic developer composition containing both rough and smooth carrier particles Download PDF

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US3838054A
US3838054A US00236724A US23672472A US3838054A US 3838054 A US3838054 A US 3838054A US 00236724 A US00236724 A US 00236724A US 23672472 A US23672472 A US 23672472A US 3838054 A US3838054 A US 3838054A
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particles
surfaced
carrier
rough
smooth
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W Trachtenberg
Cabe J Mc
G Kasper
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Eastman Kodak Co
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Eastman Kodak Co
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Priority to US00236724A priority Critical patent/US3838054A/en
Priority to CA163,201A priority patent/CA995952A/en
Priority to GB1255273A priority patent/GB1390872A/en
Priority to FR7309826A priority patent/FR2176900B1/fr
Priority to BE129093A priority patent/BE797133A/xx
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    • 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
    • G03G9/107—Developers with toner particles characterised by carrier particles having magnetic components
    • G03G9/1087—Specified elemental magnetic metal or alloy, e.g. alnico comprising iron, nickel, cobalt, and aluminum, or permalloy comprising iron and nickel
    • 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
    • G03G9/107—Developers with toner particles characterised by carrier particles having magnetic components
    • G03G9/1075—Structural characteristics of the carrier particles, e.g. shape or crystallographic structure
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
    • Y10T428/2982—Particulate matter [e.g., sphere, flake, etc.]

Definitions

  • This invention relates to a particulate carrier vehicle and a dry electrographic developer composition containing such a carrier vehicle.
  • the particulate carrier vehicle described herein contains a mixture of rough-surfaced magnetically responsive particles, e.g., sponge iron powder and smooth-surfaced magnetically responsive particles, e.g., smooth, spherical iron particles.
  • This invention relates to electrography and to a dry developer composition useful, for example, in the magnetic brush development of latent electrostatic charge images.
  • these electrophotographic processes have in common the steps of employing a normally insulating photoconductive element which is prepared to respond to imagewise exposure with electromagnetic radiation by forming an electrostatic charge pattern.
  • the electrostatic charge pattern is then rendered visible by a development step in which the charged surface of the photoconductive element is brought into contact with a suitable developer mix.
  • One method for applying the developer mix is by the well-known magnetic brush process.
  • Such a process generally utilizes apparatus of the type described, for example, in US. Pat. No. 3,003,- 462, Streich, issued Oct. 10, 1961, and customarily comprises a non-magnetic rotatably mounted cylinder having fixed magnetic means mounted inside. The cylinder isarranged to rotate so that part of the surface is immersed in or otherwise contacted with a supply of developer mix.
  • the granular mass comprising the developer mix is magnetically attracted to the surface of the cylinder.
  • the particles thereof arrange themselves in bristle-like formations resembling a brush.
  • the bristle formations of the developer mix tend to conform to the lines of magnetic flux, standing erect in the vicinity of the poles and laying substantially flat when said mix is outside the environment of the magnetic poles.
  • the continually rotating tube picks up development mix from a supply source and returns part or all of this material to the supply. This mode of operation assures that fresh mix is always available to the copy sheet surface at its point of contact with the brush.
  • the roller performs the successive steps of developer mix pickup, brush formation, brush contact with the photoconductive element, brush collapse and finally mix release.
  • smooth, preferably curved-surfaced magnetic carrier particles such as substantially spherical iron particles, or the like may, in certain cases, be preferable to the rough-surfaced carrier particles described above.
  • This latter type of magnetic material i.e. smooth-surfaced magnetic particles
  • this latter type of magnetic material when used as a carrier in a magnetic-brush development composition, also provides good solid area reproduction.
  • a more detailed description of this latter type of magnetic carrier material may be found in Canadian Pat. 838,061 issued Mar. 31, 1970.
  • a method of making such smooth-surfaced magnetic particles may be found in US. Pat. 3,099,041 issued July 30, 1963.
  • smooth-surfaced magnetic particles as carrier materials in a developer composition.
  • a primary difiiculty encountered is the relatively high density of solid iron and similar ferromagnetic carrier materials which have these physical characteristics, i.e. smooth surfaces.
  • Such high density, smooth particles tend to exhibit undesirable toner throwofi and difiicult toner replenishment characteristics.
  • these particles are quite dense and smooth, and accordingly flow extremely well in a magnetic brush developer system, these particles also have a relatively low apparent volume. Therefore, for optimum results, one generally uses about twice the weight level of these smooth-surfaced iron carrier particles in comparison to the weight of carrier required when one utilizes more conventional magnetic carriers such as the iron filings and reduced iron oxide particles, discussed hereinabove.
  • the latter more conventional magnetic carrier particles are characterized by a much lower density and a much higher apparent volume. Because of the generally high weight level of smooth-surfaced iron particles which may be required to obtain an optimum apparent volume for use in magnetic brush development compositions, there is a much higher torque requirement on the rotatably mounted magnetic-brush cylinder. And, of course, because a greater weight of these smooth-surfaced iron carrier particles is required, significantly greater costs are involved.
  • a further defect of many conventional electrostatic developer compositions relates to the mix life or the useful life of the developer mix.
  • Mix life is defined herein to mean the total number of reproductions that may be produced by an electrographic system before the developer composition becomes inoperable, i.e. fatigued.
  • an improved particulate carrier vehicle and an improved dry electrographic developer composition containing such a carrier vehicle comprises a mixture of rough-surfaced magnetically responsive particles and smooth-surfaced magnetically responsive particles.
  • the smooth-surfaced particles have rounded edges and curvilinear surfaces to provide enhanced flow through an electrographic development apparatus.
  • the electrical properties of the carrier mixture may be varied to provide certain advantageous results.
  • the smooth-surfaced carrier particles may be modified to provide smooth-surfaced particles which have a relatively high or intermediate electrical resistance.
  • a carrier mixture comprising smoothsurfaced, electrically insulating magnetic particles and rough-surfaced, electrically conductive magnetic particles provides a useful carrier composition.
  • a carrier mixture comprising rough-surfaced electrically insulating magnetic particles and smooth-surfaced electrically conducting magnetic particles provides a developer composition giving useful results.
  • a carrier composition comprising rough-surfaced electrically conductive magnetic particles and smooth-surfaced electrically conductive magnetic particles also provides a carrier composition yielding substantially improved results.
  • carrier composition comprising roughsurfaced electrically insulating magnetic particles and smooth curvilinear-surfaced, electrically insulating magnetic particles provides a developer composition yielding useful results.
  • the carrier mixture and dry electrographic developers containing such mixtures provide at least one or more of the following advantages: improved image characteristics such as substantial reduction or elimination of edge-effect, increased mix life of the developer composition containing the carrier mixture of the invention, improved flow properties, reduced toner throw off i.e. reduction in the amount of toner thrown out of the developer composition as it flows through a magnetic brush development system, reduction in abrasion of the reusable photoconductive element used in an electrophotographic image system, ease of cleaning a photoconductive element used in an electrophotographic imaging system and ease of toner replenishment.
  • FIGS. 1 and 2 illustrate certain of the advantages provided by the invention.
  • FIG. 1 illustrates the dependence of developer resistance on the composition and resistivity of the carrier vehicle.
  • FIG. 2 illustrates the improved flow times obtainable using a developer containing a carrier vehicle comprising rough-surfaced and smooth-surfaced carrier particles.
  • a particular sample of microsize magnetic particles may be viewed, for example, at x magnification.
  • magnetic particles having rough surfaces are readily distinguished from magnetic particles having smooth surfaces.
  • rough-surfaced particles when viewed at 100 magnification have one or more of the following characteristics: substantially larger surface area than smooth, curvilinearsurfaced particles sieved to the same mesh size; thin knife edges; pitted, fissured surfaces; bristle-like protrusions; irregular shapes.
  • the smooth surfaced particles when viewed at 100x magnification have the following characteristics: smooth, substantially continuous and substantially unbroken surfaces; generally curved surfaces, preferably with few visible edges or corners (if corners or edges are present, they typically appear as corners or edges of an equidimensional particle, e.g., a smooth-surfaced cubical particle, or they are rounded and blunt); preferably these particles have similar shapes, typically an oval or spherical shape, to promote gOOd flow properties. Accordingly, throughout the present specification and appended claims, the terms rough-surfaced and smooth-surfaced are defined in terms of the above-described 100 identirfication procedure.
  • the rough-surfaced magnetic particles of the present invention may be selected from a variety of magnetic particles having the aforementioned surface properties.
  • these carrier particles have an average size within the range of from about 1200 microns to about 30 microns or less with particularly useful results being obtained with particles having an average size Within the range of from about 300 microns to about 60 microns.
  • the phrase average size refers to the average thickness of particles when measured along several axes. Average size also refers generally to the approximate size of the openings in a standard sieve series which will just retain or just pass a given particle. The phrase average size is thus not meant to imply that only perfectly uniform dimensioned particles can be used.
  • the magnetic properties of these carrier particles may be imparted to the particles by a variety of techniques.
  • These rough-surfaced magnetic particles may be formed from a non-magnetic core material such as organic resinous material or inorganic material such as a salt crystal or crystals, etc. having a magnetic overcoat applied thereto.
  • a non-magnetic core material such as organic resinous material or inorganic material such as a salt crystal or crystals, etc. having a magnetic overcoat applied thereto.
  • these particles may have a magnetic core overcoated with a non-magnetic material such that the resultant particles have a rough surface.
  • these rough-surfaced carrier'particles may be composed of a hollow magnetic ball having a rough surface.
  • these particles are solid ferromagnetic materials having rough surface characteristics. Such materials are well known in the electrographic art and are conventionally utilized in many magnetic brush development processes.
  • rough-surfaced particles examples include iron and'steel filings, sponge iron powder, etc. These materials are sold under various trade names such as SCM Corporation Glidden 475 electrolytic iron powder and Hoeganaes Corporation Ancor EH80-150 iron powder.
  • these rough-surfaced magnetic particles have a relatively low apparent density less than about 3.5 grams per milliliter, preferably on the order of from about 2 to about 3 grams per ml. Accordingly, in view of their low apparent density, these preferred particles typically may be characterized as porous, rough-surfaced particles.
  • the smooth-surfaced magnetic particles utilized in the present invention have an average size within the range of from about 1200 microns to about 30 microns or less with particularly useful results being obtained with particles having an average size within the range of from about 300 microns to about 60 microns.
  • these smooth-surfaced particles may generally have a composition similar to the rough-surfaced particles.
  • These smooth-surfaced particles may be composed of a non-magnetic core overcoated with a magnetic material such that the resultant particle has a smooth surface. Or, these particles may have a.,magnetic core overcoated with a non-magnetic material such that the resultant particles have a smooth surface.
  • these particles may be composed of hollow magnetic balls having smooth surface characteristics.
  • these materials are solid ferromagnetic particles having a relatively high apparent density.
  • Such solid particles typically, by themselves, have an apparent density greater than about 3.5 grams per ml.; preferably an apparent density within the range of from about 4.0 grams per ml. to about 5.0 grams per ml.
  • the magnetic remanance of these solid, smoothsurfaced magnetic iron particles is preferably significantly higher than the magnetic remanance of the preferred low density rough-surfaced iron or steel particles used in the carrier mixture.
  • these smooth-surfaced iron particles have a magnetic remanance of about 8 or more maxwells.
  • smooth-surfaced magnetic carrier particles are solid particles Which are substantially oval or spherical in shape and which are prepared by methods such as that described in U.S. Pat. 3,099,041, hereby incorporated in the present invention by reference thereto.
  • Other useful smooth curvedsurfaced magnetic carrier particles and methods of preparing the same are described in Canadian Pat. 838,061.
  • solid ferromagnetic particles such as various iron, nickel, and cobalt compounds and alloys and mixtures thereof are preferred magnetic materials useful in the invention
  • other magnetically-responsive materials may be used.
  • a number of extremely small magnetically-responsive particles may be joined together by a binder material such as a resin to form a larger magnetic particle having the appropriate surface characteristics for use in the present invention.
  • a carrier particle is described in Miller, Canadian Pat. 835,317 dated February 24, 1970.
  • the relative amounts of the rough-surfaced magnetic particles and the smooth-surfaced magnetic particles comprising the carrier mixtures of the present invention may vary widely.
  • the carrier mixture should contain at least about 10% by weight of the rough-surfaced magnetic particles, and preferably from about -75% by weight of the rough-surfaced magnetic particles with the remainder of the carrier mixture comprising the smooth-surfaced magnetic particles.
  • amounts somewhat less than or more than the aforementioned percentages may be utilized, it will be recognized that an amount much lower or much higher than those specified will lead to a carrier mixture which has nearly the same properties of a mixture composed solely of rough-surfaced particles or solely of smooth-surfaced particles and will not provide the advantages obtained using a mixture of these particles.
  • a carrier mixture comprising from about 25 to about 50 by weight of electrically conductive roughsurfaced magnetic particles and from about to about 50 by weight of electrically conductive, smooth, curvilinear-surfaced magnetic particles in admixture with a suitable electroscopic toner material provides a developer having certain definite advantages.
  • a maximum of smooth-surfaced magnetic particles in a developer mixture is obtained when both the rough-surfaced and the smooth-surfaced particles have a relatively low electrical resistivity. (See FIG. 1 and Example 7.)
  • a developer comprising a carrier vehicle containing a mixture of electrically conducting smooth, curvilinear-surfaced and rough-surfaced magnetic particles.
  • a preferred embodiment of the present invention relates to a carrier comprising a mixture of electrically conducting smooth-surfaced and rough-surfaced magnetic particles
  • the present invention is not limited thereto.
  • the electrical properties of the developer mixture of the present invention may be varied to include electrically insulating particles therein.
  • electrically insulating and electrically conducting are defined herein as follows: electrically insulating carrier particles or developer mixes (i.e., mixtures of carrier particles and dry toner powder) have an electrical resistance greater than about ohms up to 10 ohms and higher whereas electrically conducting carrier particles or developer mixes are defined as having a lower electrical resistance, i.e., less than about 10 ohms down to 10 ohms or lower.
  • the electrical resistance of carrier particles and developer mixes as defined herein is measured according to the following test: A 15 gram quantity of the particular carrier particles or developer mix to be tested is selected. A cylindrically-shaped bar magnet having a circular end of about 6.25 square cm. in area is used to attract the 15 grams of sample carrier and hold it in the form of a brush. After formation of the brush, the bar magnet is positioned with the brush-carrying end approximately parallel to "and about 0.5 cm. from a burnished copper plate.
  • resistance of the particles in the magnetic brush is then measured between the magnet and the copper plate.
  • Electrostatic developer compositions of the present invention can be prepared by mixing from about 90 to about 99% by weight of the above-described carrier vehicle with from about 10 to about 1% by weight of a suitable electroscopic toner material.
  • the toner material (or marking particles) useful in dry electrographic developer compositions are generally comprised of a resin binder and a colorant.
  • Suitable toners can be selected from a wide variety of materials to give desired physical properties to the developed image and the proper triboelectric relationship to match the carrier particles used.
  • any of the toner powders known in the art are suitable for mixing in the developer composition of this invention.
  • the toner may be comprised solely of colorant material without any resinous binder.
  • the toner may be composed solely of a colorless material, such as a resinous material, having the desired physical and triboelectric properties.
  • the toner powder selected When the toner powder selected is utilized with magnetic carrier particles in a magnetic-brush development arrangement, the toner clings to the carrier by triboelectric attraction.
  • the carrier particles acquire a charge of one polarity and the toner acquires a charge of the opposite polarity.
  • the toner normally acquires a positive charge and the carrier a negative charge.
  • Useful toner particles can be prepared by various methods. Two convenient techniques for preparing these toners are spray-drying or melt-blending followed by grinding. Spray-drying involves dissolving the resin, colorant and any additives in a volatile organic solvent such as dichloromethane. This solution is then sprayed through an atomizing nozzle using a substantially non-reactive gas such as nitrogen as the atomizing agent. During atomization, the volatile solvent evaporates from the airborne droplets, producing toner particles of the uniformly colored resin. The ultimate particle size is determined by varying the size of the atomizing nozzle and the pressure of the gaseous atomizing agent. Further details relating to spraydrying may be found in Carlson, U.S. Pat. 2,357,809 issued Sept.
  • particles of a diameter between about /2 i and about 30 are used, with particles between about 2p. and 15 being preferred, although larger or smaller particles can be used Where desired for particular development or image considerations.
  • Suitable toners can also be prepared by melt-blending. This technique involves melting a powdered form of polymer or resin and mixing it with suitable colorants and additives. The resin can readily be melted or heated on compounding rolls which are also useful to mix or otherwise blend the resin and addenda so as to promote the complete intermixing of these various ingredients. After thorough blending, the mixture is cooled and solidified. The resultant solid mass is then broken into small pieces and finely ground to form a free-flowing powder of toner particles.
  • melt-blending technique is described in Walkup, US. Pat. 2,618,551 issued Nov. 18, 1951. Of course, various other techniques for making toner particles may also be used.
  • certain spray-freeze drying techniques may be modified to provide useful methods for preparing toner particles.
  • An example of such a modified spray freeze drying technique is described in Product Licensing Index, Volume 84, Apr. 1971, pages 343 6.
  • the resultant toner particles usually range in size from about A: to about 30a.
  • the resin material used in preparing the toner can be selected from a wide variety of materials, including natural resins, modified natural resins and synthetic resins.
  • useful resins are balsam resins, colophony, and shellac.
  • suitable modified natural resins are colophonyl-modified phenol resins and other resins listed below with a large proportion of colophony.
  • Suitable synthetic resins are all synthetic resins known to be useful for toner purposes, for example, polymers, such as certain polycarbonate resins described in US. patent application Ser. No.
  • vinyl polymers and copolymers including polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyvinyl acetals, polyvinyl ether, polyacrylic and polymethacrylic esters, polystyrene, including substituted polystyrenes; polycondensates, e.g., polyesters, such as phthalate, terephthalic and isophthalic polyesters, maleinate resins and colophony-mixed esters of higher alcohols; phenolformaldehyde resins, including modified phenol-formaldehyde condensates; aldehyde resins; ketone resins; polyamides; polyurethanes, etc.
  • polyesters such as phthalate, terephthalic and isophthalic polyesters, maleinate resins and colophony-mixed esters of higher alcohols
  • phenolformaldehyde resins including modified phenol-formaldehyde condensates
  • chlorinated rubber and polyolefins such as various polyethylenes, polypropylenes, polyisobutylene, are also suitable.
  • Typical toner materials having incorporated therein styrene containing materials are disclosed in the following US. Patents: Solar 2,917,- 460 issued Dec. 15, 1959; Carlson Re. 25,136 issued Mar. 13,1962; Rheinfrank et al. 2,788,288 issued Apr. 9, 1957; Walkup et al. 2,638,416 issued Apr. 12, 1953; Wise 2,618,- 552 issued Nov. 18, 1952; and Copley 2,659,670 issued Nov. 17, 1953.
  • styrene containing toner resins are copolymers prepared from a monomeric blend of (a) 40-60% by weight styrene or styrene homolog; (b) 20- 50% by weight of lower alkyl acrylate and methacrylate, e.g. alkyl methacrylates and alkyl acrylates having up to 3 carbon atoms in the alkyl group; and (0) 530% by weight of higher alkyl acrylates and methacrylates, e.g. alkyl methacrylates and alkyl acrylates having 6-20 or more carbon atoms in the alkyl group.
  • Colorants useful in the practice of this invention can be selected from a variety of materials such as dyestuffs or pigments. Such materials serve to color the toner and thus render it more visible. Suitable toner materials having appropriate caking and charging properties can, of course, be prepared without the use of a colorant material Where it is desired to have a developed image of low optical opacity. In those instances where it is desired to have high optical opacity, the colorants usedcan, in principle, be selected from virtually all of the compounds mentioned in the Color Index, Vols. I and II, Second Edition, Included among the vast number of useful colorants would be such materials as Hansa Yellow G (C.I. 11680), Nigrosine Spirit soluble (C.I. 50415), Chromogen Black ETOO (CI.
  • nigrosine salts such as nigrosine salts of monoand (ii-functional organic acids having from about 2 to about 20 carbon atoms such as chloroacetic acid, stearic acid, sebacic acid, lauric acid, azelaic acid, adipic acid, abietic acid and the like. Nigrosine salts of this type are disclosed in Belgian Pat. 734,570 dated Aug. 14, 1969. Carbon black also provides a useful colorant as disclosed in Walkup, US.
  • the amount of colorant added may vary over a wide range, for example, from about 3 to about 20 percent of the weight of the resin binder. Particularly goOd results are obtained when the amount is from about 5 to about percent. In certain instances, it may be desirable or preferred to omit the colorant, in which case the lower limit of concentration would be zero.
  • organic melt viscosity modifying agents for the resin binder may be incorporated in the toner particles. If such viscosity modifying agents are utilized, the ratio of melt viscosity modifying agent to resin binder generally can vary from about 1:3 to about 1.5: 1. Further information concerning these viscosity modifying agents may be found in Merrill et al., US. Application Ser. No. 23,031, filed Mar. 26, 1970.
  • H Refers to Hoeganaes Corp. Ancor EH80-150 sponge iron powder, a rough-surfaced powder sieved to 80 +120 mesh.
  • W Refers to high density, smooth-surfaced spherical iron powder particles obtained from the Nuclear Metals Division of Whittaker Corp. having an average particle size within the sieve range of 70 +170 mesh and an apparent density of about 4.64 g./ml.
  • Insulating Refers to the coating of the magnetic particles with a thin layer of a polymeric material such as a vinylidene chloride-acrylonitrile-acrylic acid terpolymer or a metal ion-linked carboxylic acid-a-olefin copolymer (such as those sold under the trademark of Elvax dispersions by E. I. du Pont & Co.) to provide particles which are electrically insulating as defined hereinbefore.
  • a polymeric material such as a vinylidene chloride-acrylonitrile-acrylic acid terpolymer or a metal ion-linked carboxylic acid-a-olefin copolymer (such as those sold under the trademark of Elvax dispersions by E. I. du Pont & Co.) to provide particles which are electrically insulating as defined hereinbefore.
  • a polymeric material such as a vinylidene chloride-acrylonitrile-acrylic acid terpolymer or a metal ion-linked carboxylic
  • SA means solid area development predominates. That is, one obtains good copies of solid area images including good fill-in of solid area images.
  • S-S means semisolid area development predominates characterized by slight loss in density of the center of a copy of a 25 mm. square solid image.
  • M means medium area development predominates characterized by a large loss in density of the center of a copy of a 25 mm. square solid image.
  • S-F means semi-fringed development predominates wherein little density is produced in the center of a copy of a 25 mm. square solid image.
  • F means fringed development predominates wherein no density is produced over the majority of the internal area of a copy of a 25 mm. square solid image.
  • Line Reproduction Refers to the ability to reproduce fine, weak and unsharp lines.
  • smoothness Refers to the ability to reproduce solid area images free from scratches, mottle, etc.
  • Throwofi Refers to the developers ability to hold toner without dusting as the developer is mechanically agitated.
  • Replenishment Refers to the developers ability to accept toner in the replenishment mode.
  • Flow Refers to the developers ability to be carried around the magnetic brush during development.
  • P,A,S Refer to the ratings of poor, acceptable and superior, respectively.
  • Example 1 Part 1 of Table I lists the data which are obtained when a carrier vehicle containing a mixture of rough-surfaced electrically insulating particles and rough-surfaced electrically conducting particles is used. Note particularly that the weakness and strengths of the mixtures are controlled by the individual carrier components.
  • a carrier mixture of this type exhibits three defects: poor fine-line reproduction, poor quality solid-area reproduction, and poor flow characteristics.
  • This rough-surfaced carrier material appears to have properties which prevent it from perforning satisfactorily; e.g., rough-surfaced sponge iron has a craggy surface which is rough and irregular.
  • particles of this type are highly abrasive during the development operation causing poor fine-line reproduction, scratchy solid areas and characters, and poor developer flow.
  • Carrier A in this example is H-Conducting.
  • Carrier B in this example is H-Insulating, having a thin external layer composed of vinylidene chloride-acrylonitrileacrylic acid copolymer.
  • Example 2 Part 2 of Table I included for purposes of comparison shows that both conducting and insulating smooth-surfaced iron particles are acceptable in all imaging characteristics, but fall short with regard to throwolf and replenishment.
  • the iron particles used in this example are quite dense, spherical and extremely smooth, quite different from the particles used in Example 1.
  • the electrographic properties of these smooth-surfaced particles are also different from those exhibited by the particles used in Example 1. If the insulating and conducting particles used in this example are mixed together, the carrier mixture is at best, a poor compromise.
  • Carrier A in this example is W-Conducting.
  • Carrier B in this example is W-Insulating,
  • Example 3 Part 3 of Table I shows the results obtained when smooth-surfaced particles are mixed with rough-surfaced particles in accordance with the present invention. In order for a mixture to be judged acceptable in all areas, it should have an A or S rating in every category.
  • the data of Part 3 indicate that a mixed carrier vehicle of the invention satisfies all categories.
  • the smoothsurfaced particles contribute to the imaging properties to the extent that acceptable mages are generated, despite the presence of the rough-surfaced particles.
  • the roughsurfaced particles provide the necessary physical properties to hold the toner in the developer bulk.
  • Carrier A in this example is H-Conducting.
  • Carrier B in this example is W-Insulating, having a thin external layer composed of a vinylidene chloride-acrylonitrile-acrylic acid copolymer.
  • Example 4 Part 4 of the table again shows the improved results obtained by the use of the mixed carrier of this invention.
  • This example differs from Example 3 in that the rough, irregularly-surfaced iron is overcoated with a polymer to make it electrically insulating and the smooth-surfaced iron is nickeled to make it more conducting.
  • the table indicates that the insulating rough-surfaced carrier by itself satisfies most of the tested requirements. This is to be expected, since the overcoat material may, to an extent, fill up the interstitial voids in the carrier rendering it more round and smooth. But the rounding and smoothing operation does not convert such particles completely to smooth-surfaced particles.
  • the insulating rough-surfaced particles have at least one weakness which prevents a carrier of these particles from being totally accepted.
  • such a carrier provides primarily fringing and semifringing developed images apparently due to the infiuence of the insulating polymer coating and does not give good reproduction of solid area images.
  • a carrier should be admixed with a solid-area carrier, in this case conducting smoothsurfaced iron particles. The admixture of smooth-surfaced iron particles also improves the flow properties of the carrier.
  • Carrier A in this example is H-Insulating having a thin external layer composed of a vinylidene chloride-acrylo nitrile-acrylic acid copolymer.
  • Carrier B in this example is W-Conducting.
  • Example 5 Part 5 of the table shows that this invention is not restricted to the use of insulating/conducting carrier mixtures only.
  • a smooth-surfaced conducting carrier and a rough-surfaced conductive carrier are mixed together, the superior properties of each blend together to produce mixtures which are acceptable in every category.
  • Carrier A is H-Conducting.
  • Carrier B is W-Conducting.
  • Example 6 Part 6 of the table indicates that the advantages of the invention can be realized by a mixture of two insulating mixtures. Note in particular the superior performance of the mixtures in the ratios of 40/60 and 35/65.
  • Carrier A is H-Insulating, having a thin outer layer composed of a dried Elvax resinous dispersion, said outer layer containing about 33% by weight of electrically conductive carbon particles having a particle size within the range of 1-20 microns.
  • Carrier B is W-Insulating, having a thin external layer composed of a dried Elvax resinous dispersion, said outer layer containing about 35% by weight of small electrically conductive carbon particles having a particle size within the range of 1-20 microns.
  • Example 7 Table I shows that flow, smoothness and line reproduction are improved by the use of a smooth particle.
  • replenishment and throwoif are improved by the use of a rough particle. It is advantageous, therefore, to add a maximum of smooth carrier component to produce the desired image while maintaining good replenishment and throwoff characteristics.
  • FIG. 1 of this example illustrates that for a given developer resistivity a maximum of smooth carrier component in a mixture is obtained when both particles are of low resistivity.
  • the materials used to obtain the data on which FIG. 1 is based are described below as follows:
  • the low resistivity carrier particles used in FIG. 1 are prepared by utilizing ferromagnetic particles having an oxide surface such that the electrical resistance of the particles is less than about 10 ohms using the resistance test described hereinbefore.
  • the polymer coating is composed of a dried Elvax resinous dispersion as described hereinbefore.
  • the higher resistance carrier particles used in FIG. 1 of this example are prepared in a manner such that the oxide surface on the ferromagnetic particles provides particles having a resistance greater than about 10 ohms.
  • carrier A is composed of W iron particles having an Elvax coating thereon and has a relatively high electrical resistance.
  • Carrier B is composed of H iron particles having an Elvax coating thereon and has a relatively low resistance.
  • Carrier C is composed of W iron'particles having an Elvax coating thereon and has a relatively low electrical resistance.
  • the horizontal axis represents the weight percent of smooth curvilinear-surfaced iron particles, i.e., W iron particles, present in a carrier vehicle composed of a mixture of smooth and rough-surfaced particles.
  • the vertical axis of the graph represents the electrical resistance of a developer containing 3-5 by weight toner and -97% by weight of the carrier vehicles represented on the horizontal axis. The electrical resistance of a given developer is determined as indicated earlier in the present specification.
  • dry developers used in Examples 1-7 above contain from about 3 percent to about 5 percent by weight of toner which is composed of particles of a black pigmented polycarbonate resin, said resin particles described in US. patent application Ser. No. 34,557, filed May 4, 1970, and Product Licensing Index, Volume 84, April 1971, pages 69-70.
  • FIG. 2 based on this example illustrates the improvement in developer flow achieved by the addition of smooth, curvilinear-surfaced carrier particles to a carrier vehicle composed of a mixture of smooth and rough-surfaced particles.
  • the data on which FIG. 2 is based is obtained using W-iron particles having an Elvax coating as the smooth, curvilinear-surfaced particles and H-iron particles having an Elvax coating as the roughsurfaced iron particles.
  • the horizontal axis represents the weight percent of smooth, curvilinear-surfaced iron particles, i.e., W iron particles, present in a carrier vehicle composed of a mixture of smooth and rough-surfaced, i.e., H-iron particles.
  • FIG. 2 represents the flowtime in seconds for a unit volume of developer. Flowtimes are determined as follows: Using a Hall Flowmeter, sufiicient developer (toner plus carrier) is allowed to flow through a standard Hall Flowmeter cup #856 (rated at 39.9 seconds) mounted one inch above a 25 ml. receiving cup until the cup is completely filled (25 ml.). The developer is then placed back in the standard cup #856 and the time (in seconds) for all of the developer to flow through the standard orifice is measured as the flowtime.
  • Each of the developers used to provide the data for the FIG. 2 graph are composed of 97% by weight carrier particles and 3% by weight of pigmented thermoplastic resin toner particles.
  • An electrographic developer composition for use in developing electrostatic charge patterns, comprising a free flowing particulate, magnetically-responsive carrier vehicle and particulate electroscopic toner material triboelectric'ally -attractable to said carrier vehicle, said carrier vehicle comprising a mixture of rough-surfaced, irregularly shaped magnetically responsive particles and smooth-surfaced, regularly shaped magnetically responsive particles, said rough and said smooth particles having an average size within the range of from about 1200 microns to about 30 microns, said rough particles being present in an amount of from about percent to about 83 percent by weight of the carrier vehicle.
  • said magneticallyr'e sponsive particles comprise solid particles of ferromagnetic materials selected from the group consisting of iron, cobalt, nickel and alloys and mixtures thereof.
  • A11 electrographic developer composition for use in developing electrostatic charge patterns, comprising a free flowing particulate, magnetically-responsive carrier vehicle and particulate electroscopic toner material triboelectrically-attractable to said carrier vehicle, said carrier vehicle comprising a mixture of rough-surfaced, irregularly shaped magnetically responsive particles and smoothsurfaced, regularly shaped magnetically responsive particles, said rough and said smooth particles having an average size within the range of from about 1200 microns to about 30 microns, said rough and said smooth particles being electrically conductive, and said rough particles being present in an amount of from about 10 percent to about 83 percent by weight of the carrier vehicle.
  • An electrographic developer composition for use in developing electrostatic charge patterns, comprising a free-flowing particulate, magnetically-responsive carrier vehicle and particulate electroscopic toner material triboelectrically-attractable to said carrier vehicle, said carrier vehicle comprising a mixture of rough-surfaced, irregularly shaped ferromagnetic particles having an apparent density less than about 3.5 g./ml. and smooth, regularly shaped convexly-surfaced ferromagnetic particles having an apparent density greater than about 3.5 g./ml., said rough and said smooth particles having an average size within the range of from about 1200 microns to about 30 microns, said rough particles being present in an amount of about 10 percent to about 83 percent by weight of the carrier vehicle.
  • said rough and said smooth particles comprise iron and wherein said rough and said smooth particles have an average size within the range of from about 300 microns to about 60 microns.
  • An electrographic developer composition for use in developing electrostatic charge patterns, comprising a free flowing particulate, magnetically-responsive carrier vehicle and particulate electroscopic toner material triboelectrically-attractable to said carrier vehicle, said carrier vehicle comprising a mixture of (a) rough-surfaced, irregularly shaped, electrically conducting ferromagnetic iron or iron alloy particles having an apparent density within the range of from about 2 to about 3 g./ml.
  • An electrographic developer composition for use in developing electrostatic charge patterns, comprising a free flowing particulate, magnetically-responsive carrier vehicle and particulate electroscopic toner material triboelectrically-attractable to said carrier vehicle, said carrier vehicle comprising a mixture of rough-surfaced, irregularly shaped magnetically responsive particles and smoothsurfaced, regularly shaped magnetically responsive particles, said rough and said smooth particles having an average size within the range of from about 1200 microns to about 30 microns, said rough and said smooth particles being electrically conductive, and said rough particles being present in an amount of from about percent to about 75 percent by weight of the carrier vehicle.
  • An electrographic developer composition for use in developing electrostatic charge patterns, comprising a free flowing particulate, magnetically-responsive carrier vehicle and particulate electroscopic toner material triboelectrically-attractable to said carrier vehicle, said carrier vehicle comprising a mixture of (a) rough-surfaced, irregularly shaped, electrically conducting ferromagnetic iron or iron alloy particles having an apparent density within the range of from about 2 to about 3 g./ml.
US00236724A 1972-03-21 1972-03-21 Electrostatic developer composition containing both rough and smooth carrier particles Expired - Lifetime US3838054A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
US00236724A US3838054A (en) 1972-03-21 1972-03-21 Electrostatic developer composition containing both rough and smooth carrier particles
CA163,201A CA995952A (en) 1972-03-21 1973-02-08 Electrographic carrier vehicle and developer composition
GB1255273A GB1390872A (en) 1972-03-21 1973-03-15 Carrier vehicle
FR7309826A FR2176900B1 (cs) 1972-03-21 1973-03-20
BE129093A BE797133A (fr) 1972-03-21 1973-03-21 Vehicule sous forme de particules utilisable dans un revelateur electrographique

Applications Claiming Priority (1)

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US00236724A US3838054A (en) 1972-03-21 1972-03-21 Electrostatic developer composition containing both rough and smooth carrier particles

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US (1) US3838054A (cs)
BE (1) BE797133A (cs)
CA (1) CA995952A (cs)
FR (1) FR2176900B1 (cs)
GB (1) GB1390872A (cs)

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3965022A (en) * 1973-06-29 1976-06-22 Minnesota Mining And Manufacturing Company Pressure-fixable developing powder
US3970571A (en) * 1974-12-20 1976-07-20 Eastman Kodak Company Method for producing improved electrographic developer
JPS51117040A (en) * 1975-04-07 1976-10-14 Toshiba Corp Developer for electronic photography
US4078930A (en) * 1975-10-28 1978-03-14 Xerox Corporation Developer compositions comprising toner and carrier
US4125667A (en) * 1974-05-30 1978-11-14 Xerox Corporation High surface area ferromagnetic carrier materials
US4154871A (en) * 1975-09-12 1979-05-15 Minnesota Mining And Manufacturing Company Electrostatic coating method utilizing mixture of rough and spheroidized resin particles
US4179388A (en) * 1977-04-18 1979-12-18 Xerox Corporation Electrostatographic developer with smooth surfaced carrier
US4242434A (en) * 1975-11-26 1980-12-30 Ricoh Company, Ltd. Toner composition for multiple copy electrostatic photography
US4251616A (en) * 1976-01-07 1981-02-17 Sublistatic Holding Sa Magnetic toners and development process
US4332457A (en) * 1977-04-22 1982-06-01 Sharp Kabushiki Kaisha Fixing device for fixing images of an original document on plain paper copy sheets
US4518674A (en) * 1977-07-05 1985-05-21 Konishiroku Photo Industry Co., Ltd. Developing material for electrophotography, process for preparation
US4912005A (en) * 1989-01-26 1990-03-27 Xerox Corporation Toner and developer compositions with conductive carrier components
US5506084A (en) * 1993-12-27 1996-04-09 Brother Kogyo Kabushiki Kaisha Magnetic developer and developing device using same
US5512403A (en) * 1994-08-05 1996-04-30 Eastman Kodak Company Mixture of carrier particles useful in electrographic developers
US5554477A (en) * 1992-06-15 1996-09-10 Kyocera Corporation Developer for developing latent electrostatic images
US6365310B1 (en) * 1985-01-19 2002-04-02 Sanyo Electric Co., Ltd. Developing method and a developer for electrophotography
US20060199094A1 (en) * 2005-03-07 2006-09-07 Xerox Corporation Carrier and developer compositions

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS58199355A (ja) * 1982-05-17 1983-11-19 Toray Ind Inc 二成分系現像剤

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3965022A (en) * 1973-06-29 1976-06-22 Minnesota Mining And Manufacturing Company Pressure-fixable developing powder
US4125667A (en) * 1974-05-30 1978-11-14 Xerox Corporation High surface area ferromagnetic carrier materials
US3970571A (en) * 1974-12-20 1976-07-20 Eastman Kodak Company Method for producing improved electrographic developer
JPS51117040A (en) * 1975-04-07 1976-10-14 Toshiba Corp Developer for electronic photography
JPS5317902B2 (cs) * 1975-04-07 1978-06-12
US4154871A (en) * 1975-09-12 1979-05-15 Minnesota Mining And Manufacturing Company Electrostatic coating method utilizing mixture of rough and spheroidized resin particles
US4078930A (en) * 1975-10-28 1978-03-14 Xerox Corporation Developer compositions comprising toner and carrier
US4242434A (en) * 1975-11-26 1980-12-30 Ricoh Company, Ltd. Toner composition for multiple copy electrostatic photography
US4251616A (en) * 1976-01-07 1981-02-17 Sublistatic Holding Sa Magnetic toners and development process
US4179388A (en) * 1977-04-18 1979-12-18 Xerox Corporation Electrostatographic developer with smooth surfaced carrier
US4332457A (en) * 1977-04-22 1982-06-01 Sharp Kabushiki Kaisha Fixing device for fixing images of an original document on plain paper copy sheets
US4518674A (en) * 1977-07-05 1985-05-21 Konishiroku Photo Industry Co., Ltd. Developing material for electrophotography, process for preparation
US6365310B1 (en) * 1985-01-19 2002-04-02 Sanyo Electric Co., Ltd. Developing method and a developer for electrophotography
US4912005A (en) * 1989-01-26 1990-03-27 Xerox Corporation Toner and developer compositions with conductive carrier components
US5554477A (en) * 1992-06-15 1996-09-10 Kyocera Corporation Developer for developing latent electrostatic images
US5633107A (en) * 1992-06-15 1997-05-27 Kyocera Corporation Developer for developing latent electrostatic images and method of forming images by using the developer
US5506084A (en) * 1993-12-27 1996-04-09 Brother Kogyo Kabushiki Kaisha Magnetic developer and developing device using same
US5512403A (en) * 1994-08-05 1996-04-30 Eastman Kodak Company Mixture of carrier particles useful in electrographic developers
US20060199094A1 (en) * 2005-03-07 2006-09-07 Xerox Corporation Carrier and developer compositions

Also Published As

Publication number Publication date
FR2176900B1 (cs) 1978-04-28
GB1390872A (en) 1975-04-16
FR2176900A1 (cs) 1973-11-02
CA995952A (en) 1976-08-31
BE797133A (fr) 1973-09-21

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