EP0708378B1 - Entwickler des Zweikomponententyps, Entwicklungsverfahren und Bildherstellungsverfahren - Google Patents

Entwickler des Zweikomponententyps, Entwicklungsverfahren und Bildherstellungsverfahren Download PDF

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Publication number
EP0708378B1
EP0708378B1 EP95306880A EP95306880A EP0708378B1 EP 0708378 B1 EP0708378 B1 EP 0708378B1 EP 95306880 A EP95306880 A EP 95306880A EP 95306880 A EP95306880 A EP 95306880A EP 0708378 B1 EP0708378 B1 EP 0708378B1
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EP
European Patent Office
Prior art keywords
magnetic
particles
carrier
toner
developer
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EP95306880A
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English (en)
French (fr)
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EP0708378A3 (de
EP0708378A2 (de
Inventor
Yoshinobu C/O Canon Kabushiki Kaisha Baba
Yuzo c/o Canon Kabushiki Kaisha Tokunaga
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Canon Inc
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Canon Inc
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Publication of EP0708378A3 publication Critical patent/EP0708378A3/de
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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
    • G03G9/1088—Binder-type carrier
    • G03G9/10884—Binder is obtained other than by reactions only involving carbon-carbon unsaturated bonds
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G9/00—Developers
    • G03G9/08—Developers with toner particles
    • G03G9/0819—Developers with toner particles characterised by the dimensions of the particles
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G13/00—Electrographic processes using a charge pattern
    • G03G13/06—Developing
    • G03G13/08—Developing using a solid developer, e.g. powder developer
    • G03G13/09—Developing using a solid developer, e.g. powder developer using magnetic brush
    • 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
    • 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
    • G03G9/108—Ferrite carrier, e.g. magnetite
    • 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
    • G03G9/108—Ferrite carrier, e.g. magnetite
    • G03G9/1085—Ferrite carrier, e.g. magnetite with non-ferrous metal oxide, e.g. MgO-Fe2O3

Definitions

  • the present invention relates to a two-component type developer for developing electrostatic images in electrophotography, electrostatic recording, etc., a developing method and an image forming method.
  • charged toner particles are caused to form a toner image by utilizing an electrostatic function of the electrostatic latent image.
  • a two-component type developer comprising a toner and a carrier in mixture is suitably used in a full color copier or printer required of high image qualities.
  • a representative effort may be to use a toner and a carrier having smaller particle sizes.
  • the use of a smaller particle size toner provides an increased difficulty in powder handling and increased difficulties in optimization of electrophotographic performances, such as those of transfer and fixing other than development. Accordingly, the improvement in image quality by an improvement in toner alone poses a certain limit.
  • the densification of the magnetic brush may be accomplished by effecting a development at a part between magnetic poles in the developing sleeve or use of a smaller strength of magnetic poles in the developing sleeve from a process aspect. These measures may suppress the influence of magnetic brush but may be accompanied with difficulties because of insufficient constraint of the developer, such as scattering and poor conveyance performance. Thus, these cannot be simply adopted.
  • the densification of magnetic brush may also be accomplished by use of magnetic carrier particles having a smaller particle size or a lower magnetic force.
  • JP-A 59-104663 has proposed the use of a magnetic carrier having a small saturation magnetization. If a magnetic carrier having a small saturation magnetization is simply used, the thin-line reproducibility may be improved but, as the constraint of magnetic carrier particles on the developing sleeve is weakened, a so-called "carrier attachment" phenomenon of the magnetic carrier being transferred to a photosensitive drum to cause an image defect is liable to occur.
  • JP-B Japanese Patent Publication
  • JP-B 5-8424 for example has proposed to use a magnetic carrier and a toner of smaller particle sizes to effect a non-contactive development under a vibrating electric field.
  • the JP-B reference contains a description to the effect that the case of a magnetic carrier having a higher resistivity is effective for improving the carrier attachment in a developing process using a vibrating electric field.
  • the use of such a magnetic carrier having a higher specific resistance has been found insufficient in improving the carrier attachment to provide higher image qualities in some cases, particularly where a carrier core having a low specific resistance is exposed to the surface even in a small proportion.
  • a magnetic resin carrier is caused to have a bulk resistivity which is higher than those of the carriers having iron powder core or metal oxide core (of, e.g., ferrite, magnetite).
  • iron powder core or metal oxide core of, e.g., ferrite, magnetite.
  • a magnetic resin carrier allowed to contain an increased amount of magnetic material by using a magnetic material having different particle diameter ratios, it is possible to provide a higher magnetic constraint force if the internally added magnetic material comprises a magnetic material having a low resistivity.
  • the use of such a magnetic carrier has failed in sufficiently improving the carrier attachment in some cases when used in a developing process utilizing an alternating magnetic field.
  • the present invention provides a two component developer as defined in claim 1 of the accompanying claims, a developing method as defined in claim 16 of the accompanying claims, and a full colour image forming method as defined in claim 20 of the accompanying claims.
  • Embodiments of the present two-component developer can obviate carrier attachment and reduce or prevent the occurence of fog so that high-quality toner images can be obtained.
  • Embodiments of the present two-component developer exhibit reduced or prevented toner scattering, exhibit prolonged life, and are subject only to slight image quality degradation during copying or printing on a large number of sheets.
  • a two-component type developer for developing an electrostatic image comprising: at least a toner and a magnetic carrier; wherein
  • a developing method for developing an electrostatic image comprising the steps of:
  • an image forming method wherein the above-mentioned steps are repeated with at least a magenta developer, a cyan developer, and a yellow developer respectively, each satisfying the requirements of the above-mentioned two-component type developer, and a full color image is formed at least with the resultant magenta toner image, cyan toner image and yellow toner image.
  • Figure 1 is a schematic view of an apparatus for practicing an embodiment of the developing method according to the present invention.
  • Figure 2 is an illustration of an apparatus for measuring the (electrical) resistivity of a magnetic carrier, a carrier core and a metal oxide.
  • Figure 3 is a schematic view of an apparatus for practicing an embodiment of the image forming method according to the present invention.
  • Figure 4 is a sectional illustration of a magnetic carrier core particle according to an embodiment of the invention wherein non-magnetic metal oxide (hematite) particles are locally present at the core particle surface in preference to ferromagnetic metal oxide (magnetite) particles.
  • hematite non-magnetic metal oxide
  • magnetite ferromagnetic metal oxide
  • the above-mentioned objects have been accomplished by a two-component type developer of which the toner and the magnetic carrier have been improved in combination.
  • the present invention uses a magnetic carrier comprising composite particles such that the composite particles comprise magnetic iron compound particles, non-magnetic metal oxide particles, and a binder comprising a phenolic resin; and the composite particles contain the magnetic iron compound and the non-magnetic metal oxide in a total proportion of 80 - 99 wt. %; the magnetic iron compound particles having a number-average particle size ra, the non-magnetic metal oxide particles having a number-average particle size r b satisfying r b /r a > 1.0.
  • the higher-resistivity non-magnetic metal oxide particles are caused to be preferentially present at the carrier particle surface, so as to effectively increase the carrier resistivity.
  • the developer according to the present invention is effective in preventing charge injection into the carrier and preventing carrier attachment to faithfully reproducing an electrostatic latent image.
  • the carrier surface can be provided with a higher resistivity than in the case where the magnetic iron oxide particles are exposed to the carrier or core surface, thereby effectively preventing the charge injection.
  • the magnetic carrier particle surfaces are provided with minute unevenness so as to better carry the toner particles.
  • toner having a weight-average particle size D4 of at most 10 ⁇ m and a sharp particle size distribution as represented by a number-average particle size D1 satisfying a ratio D4/D1 of at most 1.5 in combination with a magnetic carrier comprising composite particles comprising magnetic iron oxide particles and, non-magnetic metal oxide particles bound by a phenolic resin, it is possible to provide a two-component type developer free from fog or toner scattering and providing a good dot reproducibility.
  • the developer according to the present invention is little liable to be deteriorated and can continually provide high-quality images similarly as at the initial stage presumably for the following reason.
  • a developer is deteriorated during a long period of use thereof because the toner and the magnetic carrier are damaged primarily due to a magnetic shear or gravitational shear acting between the toner and the carrier or between the carrier particles in the developing vessel.
  • the toner is basically consumed, but the magnetic carrier is repeatedly used without being consumed so that the damage given to the surface thereof is accumulated.
  • a magnetic carrier comprising composite particles formed of a magnetic iron compound, a non-magnetic metal oxide and phenolic resin
  • the magnetic shear acting between the toner and the carrier and between the carrier particles may be reduced to reduce the surface damage exerted to the carrier particles.
  • the magnetic carrier particles used in the present invention are provided with a surface unevenness of fine particles inclusive of magnetic particles and non-magnetic metal oxide particles so that, when the magnetic carrier particles are coated with a resin, the adhesion between the magnetic carrier particles (core particles) and the coating resin is improved to suppress the peeling of the coating resin layer.
  • a smaller particle size of magnetic carrier is preferred from the viewpoint of a higher image quality but is liable to increase the carrier attachment based on a relation between the magnetic force and the particle size.
  • the magnetic carrier used in the present invention may have a number-average particle size in the range of 1 - 1000 ⁇ m and may preferably have a number-average particle size of 1 - 300 ⁇ m, so as to provide high image quality.
  • a number-average particle size of 5 - 100 ⁇ m is further suitable from the viewpoints of higher image quality, carrier attachment prevention and prevention of developer deterioration during continuous image formation.
  • the magnetic carrier has a number-average particle size in excess of 1000 ⁇ m, the specific surface area of the magnetic brush rubbing the photosensitive drum is reduced, thus being liable to fail in supplying a sufficient amount of toner and leave rubbing traces with the magnetic brush, so that this is not desirable from the viewpoints of high density and high image quality.
  • a magnetic carrier having a number-average particle size smaller than 1 ⁇ m is liable to cause the carrier attachment because of a smaller particle size per carrier particle. The method of measuring the particle size of magnetic carrier particles relied on herein will be described hereinafter.
  • the magnetic properties of the magnetic carrier used in the present invention it may be appropriate to use a magnetic carrier having a saturation magnetization ( ⁇ s ) of 10 - 80 Am 2 /kg (emu/cm 3 ). It is further preferred to use a magnetic carrier having a saturation magnetization of 15 - 60 Am 2 /kg (emu/cm 3 ).
  • the magnetization of the magnetic carrier may be appropriately selected depending on the particle size of the carrier.
  • a magnetic carrier having a magnetization in excess of 80 Am 2 /kg (emu/cm 3 ) is liable to result in a magnetic brush formed on a developer sleeve at developing pole having a low density and comprising rigid ears, thus being liable to result in rubbing traces in the resultant toner images and image defects, such as roughening of halftone images and irregularity of solid images, particularly due to deterioration in long continuous image formation on a large number of sheets.
  • the magnetic carrier is caused to exert only an insufficient magnetic force to result in toner attachment or a lower toner-conveying performance.
  • the magnetic properties referred to herein are values measured by using an oscillating magnetic field-type magnetic property auto-recording apparatus ("BHV-30", available from Riken Denshi K.K.). Specific conditions for the measurement will be described hereinafter.
  • BHV-30 oscillating magnetic field-type magnetic property auto-recording apparatus
  • the magnetic carrier used in the present invention has an (electrical) resistivity of at least 1x10 12 ohm.cm at an electric field intensity of 5x10 4 V/m. If the resistivity is below 1x10 12 ohm.cm, the above-mentioned carrier attachment and a lower dot-reproducibility due to charge leakage from the latent image in the process of development are liable to be caused.
  • the method of measuring the resistivity of magnetic carrier referred to herein will be described hereinafter.
  • the magnetic iron component constituting the core of the magnetic carrier may preferably comprise an iron-containing metal alloy, magnetite or ferrite showing magnetism as represented by a general formula of MO.Fe 2 O 3 or MFe 2 O 4 , wherein M denotes a divalent or monovalant metal, such as Mn, Fe, Ni, Co, Cu, Mg, Zn, Cd, or Li. M denotes a single species or plural species of metals.
  • alloys such as silicon steel, permalloy, sendust, Fe-Co and alnico
  • iron-based oxide materials such as magnetite, ⁇ -iron oxide, Mn-Zn-based ferrite, Ni-Zn-based ferrite, Mn-Mg-based ferrite, Li-based ferrite, and Cu-Zn-based ferrite.
  • magnetite is most preferably used.
  • the magnetic iron component used in the present invention may preferably have a saturation magnetization of at least Am 2 /kg (30 emu/g).
  • non-magnetic metal oxide may include: one or plural species of metals, such as Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Ba and Pb.
  • specific examples of the non-magnetic metal oxides may include: Al 2 O 3 , SiO 2 , CaO, TiO 2 , V 2 O 5 , CrO 2 , MnO 2 , Fe 2 O 3 , CoO, NiO, ZnO, SrO, Y 2 O 3 and ZrO 2 .
  • the above-mentioned magnetic iron compound and non-magnetic metal oxide may preferably be dispersed in a resin to form carrier core particles.
  • Examples of preferred combination may include: magnetite and hematite ( ⁇ -Fe 2 O 3 ), magnetite and ⁇ -Fe 2 O 3 , magnetite and SiO 2 , magnetite and Al 2 O 3 , magnetite and TiO 2 , and magnetite and Cu-Zn-based ferrite.
  • magnetite and hematite is preferred in view of the price and the resultant carrier strength.
  • the magnetic iron compound particles In the case of dispersing the magnetic iron compound and the non-magnetic metal oxide in a resin to form a carrier core, the magnetic iron compound particles have a number-average particle size r a and the non-magnetic metal oxide particles have a number-average particle size r b satisfying a ratio r b /r a exceeding 1.0. If the ratio is 1.0 or below, the magnetic iron compound particles generally having a lower resistivity are liable to be exposed to the surface, thus failing to achieve an increased resistivity of the carrier and prevent the carrier attachment.
  • a larger r b /r a ratio is preferred so that the larger non-magnetic metal oxide particles appear at the carrier particle surface to prevent carrier injection into the carrier, thereby preventing the carrier attachment and a lowering in dot reproducibility due to charge leakage from the latent image.
  • a r b /r a ratio of 1.2 - 5.0 is further preferred in order to provide a good combination of the effect of increasing the magnetic carrier resistivity and a reinforcement of carrier strength.
  • the above-preferred particle size ratio range is based on a discovery that, when filler particles of different sizes are simultaneously blended and dispersed in a resin to form carrier (core) particles, the particles of a larger particle size are preferentially present at the carrier (core) surface.
  • the number-average particle size r a of the magnetic iron compound may preferably be 0.02 - 5 ⁇ m while it can be varied depending on the carrier particle size.
  • the non-magnetic metal oxide particles may preferably have a number-average particle size r b of 0.05 - 10 ⁇ m. The method of measuring the particle size of metal oxides referred to herein will be described hereinafter.
  • a total volume Pal of magnetic iron compound particles and a total volume Pbl of non-magnetic metal oxide particles respectively appearing in an inside part of a carrier (core) particle section, and a total volume Pa2 of magnetic iron compound particles and a total volume Pb2 of non-magnetic metal oxide particles respectively appearing at a surface part of the carrier (core) particle section are set to satisfy Pb1/Pa1 ⁇ 1 and Pb2/Pa2 > 1, so as to provide a higher resistivity.
  • the magnetic iron compound particles may preferably have a resistivity of at least 1x10 3 ohm.cm and the non-magnetic metal oxide particles may preferably have a resistivity higher than that of the magnetic iron compound particles. More preferably, the non-magnetic metal oxide particles may have a resistivity of at least 10 8 ohm.cm. If the magnetic particles have a resistivity below 1x10 3 ohm.cm, it is difficult to have a desired resistivity of carrier even if the amount of the magnetic iron compound dispersed is reduced, thus being liable to cause charge injection leading to inferior image quality and invite the carrier attachment.
  • the metal oxide having a larger particle size has a resistivity below 1x10 8 ohm.cm, it becomes difficult to sufficiently increase the carrier core resistivity, thus being difficult to accomplish the above-mentioned effect.
  • the method of measuring resistivities of metal oxides referred to herein will be described hereinafter.
  • the magnetic carrier contains the magnetic iron compound and the non-magnetic metal oxide in a total content of 80 - 99 wt. %. If the total content is below 80 wt. %, the carrier (core) particles are liable to agglomerate with each other during the particle formation thereof, particularly by direct-polymerization. This can lead to a fluctuation in particle size distribution and a failure in good triboelectrification. Above 99 wt. %, the resultant carrier strength is lowered, and problems, such as carrier cracking, are liable to occur during continuous image formation on a large number of sheets.
  • the non-magnetic metal oxide particles occupy 5 - 70 wt. % of the total of the magnetic iron compound particles and the non-magnetic metal oxide particles. Below 5 wt. %, it becomes difficult to increase the resistivity of the carrier (core). Above 70 wt. %, the resultant magnetic carrier can have only a small magnetic force, thus being liable to invite the carrier attachment.
  • the magnetic carrier according to the present invention may preferably have a bulk density of 1.0 - 2.0 g/cm 3 .
  • the carrier attachment is liable to be cause while it can depend on the magnetic force.
  • the resultant developer is liable to be deteriorated during continuous image formation on a large number of sheets while it can also depend on the magnetic force of the magnetic carrier.
  • the bulk density of a magnetic carrier may be measured according to JIS K5101.
  • the magnetic carrier is constituted by using phenolic resin as a binder resin.
  • the magnetic carrier used in the present invention may for example, be prepared by mixing a monomer (i.e., a binder resin precursor), a magnetic iron compound and a non-magnetic metal oxide, and subjecting the mixture to polymerization to directly produce carrier core particles.
  • the monomer for the polymerization may comprise a combination of a phenol and an aldehyde. More specifically, for producing carrier (core) particles comprising a cured phenolic resin a mixture of a phenol, an aldehyde, a magnetic iron compound and a non-magnetic metal oxide may be subjected to suspension polymerization in the presence of a basic catalyst and a dispersion stabilizer in an aqueous medium.
  • a magnetic iron compound is first subjected to polymerization for particle formation to form a slurry, and a monomer, a non-magnetic metal oxide and another additive, if any, are added to the slurry to effect a second step polymerization, or a three or more step polymerization process for repeating the above steps.
  • the phenols as a monomer may include phenol, resorcinol; alkylphenols, such as m-cresol, p-tert-butylphenol, o-propylphenol, and alkylphenols, and derivatives of these. Among these, phenol is particularly preferred because of a particle forming characteristic and a cost.
  • the phenolic resin may be crosslinked.
  • the magnetic carrier used in the present invention may preferably be in a coated form with an appropriate coating resin selected according to the chargeability of the toner used in the present invention.
  • the coating can also be effected by using a resin containing non-magnetic metal oxide particles in order to control the resistivity of the carrier core or improve the lubricity of the magnetic carrier.
  • a resin-coated magnetic carrier may be effective in preventing charge injection into the magnetic carrier, preventing an excessively high resistivity of the carrier an excessive charge of the magnetic carrier and stabilizing the triboelectric charge of the toner.
  • the non-magnetic metal oxide dispersed in such a coating resin may comprise one or more species in mixture selected from the above-mentioned metal oxides.
  • THe coating amount of such a coating material may suitably be 0.5 - 10 wt. %, particularly 0.6 - 5 wt. %, based on the carrier core weight.
  • the coating amount is below 0.5 wt. %, it is difficult to sufficiently coat the carrier core particles and control the ability of triboelectrically charging the toner with the coating resin.
  • the resistivity may be in a desired range, but there may result in a lower flowability and image deterioration after continuous image formation on a large number of sheets, because of an excessive resin coating rate.
  • the coating resin used in the present invention may suitably be an insulating resin, which may be either a thermoplastic resin or a thermosetting resin.
  • the thermoplastic resin may include: polystyrene; acrylic resins, such as polymethyl methacrylate, and styrene-acrylic acid copolymer; styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, vinyl chloride resin, vinyl acetate resin, polyvinylidene fluoride resin, fluorocarbon resin, perfluorocarbon resin, solvent-soluble perfluorocarbon resin, polyvinyl alcohol, polyvinyl acetal polyvinylpyrrolidone, petroleum resin, cellulose; cellulose derivatives, such as cellulose acetate, nitrocellulose, methyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose; novolak resin, low-molecular weight polyethylene, saturated alkyl polyester resins; aromatic polyester resin
  • thermosetting (or curable resin may include: phenolic resin, modified phenolic resin, maleic resin, alkyd resin, epoxy resin, acrylic resin, unsaturated polyesters obtained by polycondensation among maleic anhydride, terephthalic acid and polyhydric alcohol, urea resin, melamine resin urea-melamine resin, xylene resin, toluene resin, guanamine resin, melamine-guanamine resin, aetoguanamine resin, glyptal resin, furan resin, silicone resin, polyimide resin, polyamideimide resin, polyetherimide resin, and polyurethane resin.
  • thermoplastic resins or thermosetting resins may be used singly or in mixture. It is also possible to use a mixture of a thermoplastic resin and a curing or hardening agent to provide a cured resin.
  • the coated magnetic carrier may preferably be produced through by spraying a coating resin solution onto carrier core particles in a floating or fluidized state to form a coating film on the core particle surfaces, or spray drying.
  • Other coating methods may include gradual evaporation of the solvent in a coating resin solution in the presence of a metal oxide under application of a shearing force. More specifically, the solvent evaporation may be performed at a temperature above the glass transition point of the coating resin, and the resultant clustered metal oxide particles may be then disintegrated. Alternatively, the coating film may be cured under heating, followed by disintegration.
  • the metal oxide may have a particle shape suitably selected for a developing system used.
  • the metal oxide used in the present invention may preferably have a sphericity of at most 2. If the sphericity exceeds 2, the resultant developer is caused to have a poor fluidity and provides a magnetic brush of an inferior shape, so that it becomes difficult to obtain high-quality toner images.
  • the toner used in the present invention has a weight-average particle size (D4) of at most 10 ⁇ m, preferably 3 - 8 ⁇ m. Further, it is important that the weight-average particle size (D4) and the number-average particle size (D1) provides a ratio (D4/D1) of at most 1.5.
  • the toner has a weight-average particle size (D4) exceeding 10 ⁇ m, the toner particles for developing electrostatic latent images become so large that development faithful to the latent images cannot be performed and toner scattering is liable to be caused.
  • D4 weight-average particle size
  • the ratio (D4/D1) of the weight-average particle size (D4) to the number-average particle size (D1) of a toner exceeds 1.5, the toner is caused to have a broad charge distribution, thus being liable to cause difficulties, such as charging failure and particle size deviation of developing toner particles.
  • the weight-average particle size and number-average particle size of toners may be measured, e.g., by using a Coulter counter. Details thereof will be descried later.
  • the toner used in the present invention may comprise a binder resin, examples of which may include: polystyrene; polymers of styrene derivatives, such as poly-p-chlorostyrene, and polyvinyltoluene; styrene copolymers, such as styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylate copolymer, styrene-methacrylate copolymer, styrene-methyl ⁇ -chloromethacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene
  • Examples of the comonomer to be used in combination with a styrene monomer for providing styrene copolymers may include vinyl monomers, including: acrylic acid; acrylic acid esters or derivatives thereof, such as methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile, and acrylamide; maleic acid; half esters and diesters of maleic acid, such as butyl maleate, methyl maleate, and dimethyl maleate; vinyl esters, such as vinyl acetate and vinyl chloride; vinyl ketones, such as vinyl methyl ketone, and vinyl hexyl ketone; and vinyl ethers,
  • the crosslinking agent may principally comprise a compound having at least two polymerizable double bonds.
  • examples thereof may include: aromatic divinyl compounds, such as divinylbenzene, and divinylnaphthalene; carboxylic acid esters having two double bonds, such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, and 1,3-butanediol dimethacrylate; divinyl compounds, such as divinylaniline, divinyl ether, divinyl sulfide and divinyl sulfone; and compounds having three or more ethylenic double bonds. These compounds may be used alone or in mixture.
  • the crosslinking agent may preferably be used in a proportion of 0.01 - 10 wt. %, further preferably 0.05 - 5 wt. %, based on the binder resin.
  • a binder resin for a pressure-fixable toner examples of which may include: polyethylene, polypropylene, polymethylene, polyurethane elastomer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, ionomer resin, styrene-butadiene copolymer, styrene-isoprene copolymer, linear saturated polyester, paraffin, and other waxes.
  • the toner used in the present invention can be used in combination with a charge control agent which is incorporated in (internally added to) or blended with (externally added to) the toner particles.
  • a charge control agent which is incorporated in (internally added to) or blended with (externally added to) the toner particles.
  • Examples of a positive charge control agent may include: nigrosine and modified products thereof with aliphatic acid metal salts; quaternary ammonium salts, such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate, and tetrabutylammonium tetrafluoroborate; diorganotin oxides, such as dibutyltin oxide, dioctyltin oxide, dicyclohexyltin oxide; dibutyltin borate, dioctyltin borate, and dicyclohexyltin borate. These compounds may be used singly or in combination of two or more species. Among these, nigrosine-based compounds and quaternary ammonium salts are particularly preferred.
  • a negative charge control agent such as organic metal salts, organic metal complexes, and chelate compounds.
  • organic metal salts such as organic metal salts, organic metal complexes, and chelate compounds.
  • acetylacetone metal complexes inclusivee of monoalkyl-substituted and dialkyl-substituted derivatives
  • salicylic acid metal complexes inclusive of monoalkyl-substituted and dialkyl-substituted derivatives
  • their corresponding salts are preferred.
  • Salicylic acid-based metal complexes or salicylic acid-based metal salts are particularly preferred.
  • preferred negative charge control agent may include: aluminum acetylacetonate, iron (II) acetylacetonate, 3,5-di-tert-butylsalicylic acid chromium complex or salt, and 3,5-di-tert-butylsalicylic acid zinc complex or salt.
  • the above charge control agent may preferably be used in a proportion of 0.1 - 20 wt. parts, particularly 0.2 - 10 wt. parts, per 100 wt. parts of the binder resin.
  • the above charge control agent When used for color image formation, it is preferred to use a colorless or pale-colored charge control agent.
  • the colorant for the toner it is possible to use a dye and/or a pigment known heretofore. Examples thereof may include: carbon black, Phthalocyanine Blue, Peacock Blue, Permanent Red, Lake Red, Rhodamine Lake, Hansa Yellow, Permanent Yellow and Benzidine Yellow.
  • the colorant may be added in an amount of 0.1 - 20 wt. parts, preferably 0.5 - 20 wt. parts, per 100 wt. parts of the binder resin.
  • the colorant may preferably be added in a proportion of at most 12 wt. parts, further preferably 0.5 - 9 wt. parts, per 100 wt. parts of the binder resin.
  • the toner constituting the developer according to the present invention can further contain a wax, such as polyethylene, low-molecular weight polypropylene, microcrystalline wax, carnauba wax, sasol wax or paraffin wax in order to improve the releasability at the time of hot pressure fixation.
  • a wax such as polyethylene, low-molecular weight polypropylene, microcrystalline wax, carnauba wax, sasol wax or paraffin wax in order to improve the releasability at the time of hot pressure fixation.
  • the toner used in the present invention may suitably be used in mixture with fine powder externally added thereto, inclusive of fine particles of inorganic materials, such as silica, alumina and titanium oxide; and fine particles of organic materials, such as polytetrafluoroethylene, polyvinylidene fluoride, polymethyl methacrylate, polystyrene and silicone resin. If such fine powder is externally added to the toner, the fine powder is caused to be present between the toner and carrier particles, or between the toner particles, so that the developer may be be provided with an improved flowability and an improved life.
  • the above-described fine powder may preferably have an average particle size of at most 0.2 ⁇ m.
  • Such fine powder may preferably have a specific surface area of at least 30 m 2 /g, particularly 50 - 400 m 2 /g, as measured by the BET method using nitrogen adsorption.
  • the fine powder may suitably be added in a proportion of 0.1 - 20 wt. parts per 100 wt. parts of the toner.
  • the binder resin of a vinyl-type or non-vinyl-type thermoplastic resin, a colorant, an optional charge control agent and other additives may be sufficiently blended in a mixer and then melt-kneaded by a hot kneading means, such as heated rollers, a kneader or an extruder to compatibly knead the resins and disperse or dissolve therein the pigment or dye.
  • a hot kneading means such as heated rollers, a kneader or an extruder to compatibly knead the resins and disperse or dissolve therein the pigment or dye.
  • the thus-kneaded product is thereafter cooled for solidification, pulverized and classified to obtain toner particles.
  • the toner particles thus obtained can be used as they are but may preferably be used in mixture with fine powder externally added thereto as described above.
  • the mixing of the toner and the fine powder may be effected by using a blender, such as a Henschel mixer.
  • the resultant toner carrying such an external additive is mixed with the magnetic carrier to provide a two-component type developer.
  • the toner may preferably occupy 1 - 20 wt. %, more preferably 1 - 10 wt. %, in a typical case while it can depend on the developing process.
  • the toner in the two-component type developer may suitably be provided with a triboelectric charge of 5 - 100 ⁇ C/g, most preferably 5 - 60 ⁇ C/g. The method of measuring triboelectric charges referred to herein will be described hereinafter.
  • the developing method using the two-component type developer according to the present invention may for example be performed by using a developing means as shown in Figure 1. It is preferred to effect a development in a state where a magnetic brush contacts a latent image-bearing member, e.g., a photosensitive drum 3 under application of an alternating electric field.
  • the alternating electric field may preferably have a peak-to-peak voltage of 500 - 5000 volts and a frequency of 500 - 10000 Hz, preferably 500 - 3000 Hz, which may be selected appropriately depending on the process.
  • the waveform therefor may be appropriately selected, such as triangular wave, rectangular wave, sinusoidal wave or waveforms obtained by modifying the duty ratio. If the application voltage is below 500 volts it may be difficult to obtain a sufficient image density and fog toner on a non-image region cannot be satisfactorily recovered in some cases. Above 5000 volts, the latent image can be disturbed by the magnetic brush to cause lower image qualities in some cases.
  • a frequency below 500 Hz may result in charge injection to the carrier, which leads to lower image qualities due to carrier attachment and latent image disturbance, in some cases. Above 10000 Hz, it is difficult for the toner to follow the electric field, thus being liable to cause lower image qualities.
  • a contact width (developing nip) C of the magnetic brush on the developing sleeve 1 with the photosensitive drum 3 at 3 - 8 mm in order to effect a development providing a sufficient image density and excellent dot reproducibility without causing carrier attachment.
  • the developing nip C is narrower than 3 mm, it may be difficult to satisfy a sufficient image density and a good dot reproducibility. If broader than 8 mm, it may become difficult to sufficiently prevent the carrier attachment.
  • the developing nip C may be appropriately adjusted by changing a distance A between a developer regulating member 2 and the developing sleeve 1 and/or changing the gap B between the developing sleeve 1 and the photosensitive drum 3.
  • the image forming method according to the present invention may be particularly effectively used in formation of a full color image for which a halftone reproducibility is a great concern by using at least 3 developing devices for magenta, cyan and yellow, adopting the developers and developing method according to the present invention and preferably adopting a developing system for developing digital latent images in combination, whereby a development faithful to a dot latent image becomes possible while avoiding an adverse effect of the magnetic brush and disturbance of the latent image.
  • the use of the toner having a sharp particle size distribution is also effective in realizing a high transfer ratio in a subsequent transfer step. As a result, it becomes possible to high image qualities both at the halftone portion and the solid image portion.
  • the use of the two-component type developer according to the present invention is also effective in avoiding the lowering in image quality in a continuous image formation on a large number of sheets because of a low shearing force acting on the developer in the developer vessel.
  • the color electrophotographic apparatus shown in Figure 3 is roughly divided into a transfer material (recording sheet)-conveying section I including a transfer drum 315 and extending from the right side (the right side of Figure 3) to almost the central part of an apparatus main assembly 301, a latent image-forming section II disposed close to the transfer drum 315, and a developing means (i.e., a rotary developing apparatus) III.
  • a transfer material recording sheet
  • a latent image-forming section II disposed close to the transfer drum 315
  • a developing means i.e., a rotary developing apparatus
  • the transfer material-conveying section I is constituted as follows. In the right wall of the apparatus main assembly 301, an opening is formed through which are detachably disposed transfer material supply trays 302 and 303 so as to protrude a part thereof out of the assembly. Paper (transfer material)-supply rollers 304 and 305 are disposed almost right above the trays 302 and 303. In association with the paper-supply rollers 304 and 305 and the transfer drum 315 disposed leftward thereof so as to be rotatable in an arrow A direction, paper-supply rollers 306, a paper-supply guide 307 and a paper-supply guide 308 are disposed.
  • Adjacent to the outer periphery of the transfer drum 315, an abutting roller 309, a glipper 310, a transfer material separation charger 311 and a separation claw 312 are disposed in this order from the upperstream to the downstream alone the rotation direction.
  • a transfer charger 313 and a transfer material separation charger 314 are disposed inside the transfer drum 315.
  • a portion of the transfer drum 315 about which a transfer material is wound about is provided with a transfer sheet (not shown) attached thereto, and a transfer material is closely applied thereto electrostatically.
  • a conveyer belt means 316 is disposed next to the separation claw 312, and at the end (right side) in transfer direction of the conveyer belt means 316.
  • a fixing device 318 is disposed. Further downstream of the fixing device is disposed a discharge tray 317 which is disposed partly extending out of and detachably from the main assembly 301.
  • the latent image-forming section II is constituted as follows.
  • a photosensitive drum e.g., an OPC photosensitive drum
  • a latent image-bearing member rotatable in an arrow direction shown in the figure is disposed with its peripheral surface in contact with the peripheral surface of the transfer drum 315.
  • a discharging charger 320 Generally above and in proximity with the photosensitive drum 319, there are sequentially disposed a discharging charger 320, a cleaning means 321 and a primary charger 323 from the upstream to the downstream in the rotation direction of the photosensitive drum 319.
  • an imagewise exposure means including, e.g., a laser 324 and a reflection means like a mirror 325, is disposed so as to form an electrostatic latent image on the outer peripheral surface of the photosensitive drum 319.
  • the rotary developing apparatus III is constituted as follows. At a position opposing the photosensitive drum 319, a rotatable housing (hereinafter called a "rotary member") 326 is disposed. In the rotary member 326, four-types of developing devices are disposed at equally distant four radial directions so as to visualize (i.e., develop) an electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 319.
  • the four-types of developing devices include a yellow developing device 327Y, a magenta developing device 327M, a cyan developing apparatus 327C and a black developing apparatus 327BK.
  • the moving peripheral speeds (hereinafter called "process speed") of the respective members, particularly the photosensitive drum 319 may be at least 100 mm/sec, (e.g., 130 - 250 mm/sec).
  • the photosensitive drum 329 After the charging of the photosensitive drum 319 by the primary charger 323, the photosensitive drum 329 is exposed imagewise with laser light modulated with a yellow image signal from an original 328 to form a corresponding latent image on the photosensitive drum 319, which is then developed by the yellow developing device 327Y set in position by the rotation of the rotary member 326, to form a yellow toner image.
  • a transfer material (e.g., plain paper) sent via the paper supply guide 307, the paper supply roller 306 and the paper supply guide 308 is taken at a prescribed timing by the glipper 310 and is wound about the transfer drum 315 by means of the abutting roller 309 and an electrode disposed opposite the abutting roller 309.
  • the transfer drum 315 is rotated in the arrow A direction in synchronism with the photosensitive drum 319 whereby the yellow toner image formed by the yellow-developing device is transferred onto the transfer material at a position where the peripheral surfaces of the photosensitive drum 319 and the transfer drum 315 abut each other under the action of the transfer charger 313.
  • the transfer drum 315 is further rotated to be prepared for transfer of a next color (magenta in the case of Figure 3).
  • the photosensitive drum 319 is charge-removed by the discharging charger 320, cleaned by a cleaning blade or cleaning means 321, again charged by the primary charger 323 and then exposed imagewise based on a subsequent magenta image signal, to form a corresponding electrostatic latent image.
  • the electrostatic latent image is formed on the photosensitive drum 319 by imagewise exposure based on the magenta signal
  • the rotary member 326 is rotated to set the magenta developing device 327M in a prescribed developing position to effect a development with a magenta toner. Subsequently, the above-mentioned process is repeated for the colors of cyan and black, respectively, to complete the transfer of four color toner images.
  • the four color-developed images on the transfer material are discharged (charge-removed) by the chargers 322 and 314, released from holding by the glipper 310, separated from the transfer drum 315 by the separation claw 312 and sent via the conveyer belt 316 to the fixing device 318, where the four-color toner images are fixed under heat and pressure.
  • a series of full color print or image formation sequence is completed to provide a prescribed full color image on one surface of the transfer material.
  • the respective color toner images can be once transferred onto an intermediate transfer member and then transferred to a transfer material to be fixed thereon.
  • the fixing speed of the fixing device is slower (e.g., at 90 mm/sec) than the peripheral speed (e.g., 160 mm) of the photosensitive drum. This is in order to provide a sufficient heat quantity for melt-mixing yet un-fixed images of two to four toner layers.
  • an increased heat quantity is supplied to the toner images.
  • At least 300 particles are taken at random from a sample carrier by observation through an optical microscope at a magnification of 100 - 5000, and an image analyzer (e.g., "Luzex 3" available from Nireco K.K.) is used to measure the horizontal FERE diameter of each particle as a particle size, thereby obtaining a number-basis particle size distribution and a number-average particle size, from which the number-basis proportion of particles having sizes in the range of at most a half of the number-average particle size is calculated.
  • an image analyzer e.g., "Luzex 3" available from Nireco K.K.
  • BHV-30 oscillating magnetic field-type magnetic property automatic recording apparatus
  • a magnetic carrier is placed in an external magnetic field of 10 kilo-oersted to measure a saturation magnification under this state. More specifically, a magnetic carrier powder sample is sufficiently tightly packed in a cylindrical plastic cell having a volume of ca. 0.07 cm 3 so as not to cause movement of carrier particles during the movement. In this state, a magnetic moment is measured and divided by an actual packed sample volume to obtain a magnetization (intensity of magnetization) per unit volume.
  • the resistivity of a carrier is measured by using an apparatus (cell) E as shown in Figure 2 equipped with a lower electrode 21, an upper electrode 22, an insulator 23, an ammeter 24, a voltmeter 25, a constant-voltage regulator 26 and a guide ring 28.
  • the cell E is charged with ca. 1 g of a sample carrier 27, in contact with which the electrodes 21 and 22 are disposed to apply a voltage therebetween, whereby a current flowing at that time is measured to calculate a resistivity.
  • a magnetic carrier is in powder form so that care should be taken so as to avoid a change in resistivity due to a change in packing state.
  • Photographs at a magnification of 5,000 - 20,000 of a sample metal oxide powder are taken through a transmission electron microscope ("H-800", available from Hitachi Seisakusho K.K.). At least 300 particles (diameter of 0.01 ⁇ m or larger) are taken at random in the photographs and subjected to analysis by an image analyzer ("Luzex 3", available from Nireco K.K.) to measure a horizontal FERE diameter of each particle as its particle size. From the measured values for the at least 300 sample particles, a number-average particle size is calculated.
  • the presence ratio between the magnetic iron compound and non-magnetic metal oxide inside the magnetic carrier particle and at the surface of the magnetic carrier particle or core particle may be measured in the following manner.
  • Carrier section samples may be prepared by dispersing carrier particles or carrier core particles within an epoxy resin, followed by fixation by solidification, and slicing the carrier-embedded resin samples by a microtome (e.g., "FC4E", available from REICHER-JUNG).
  • a microtome e.g., "FC4E", available from REICHER-JUNG.
  • Arbitrary selected particle sections are observed and photographed at a magnification of 5,000 to 20,000 through a scanning electron microscope ("S-800", available from Hitachi Seisakusho K.K.), and the photographed particle sections were analyzed by an image analyzer ("Luzex 3" available from Nireco K.K.) to measure a horizontal FERE diameter D for each dispersed particle section.
  • S-800 scanning electron microscope
  • Luzex 3 image analyzer
  • the volume of each dispersed particle is calculated to be ⁇ D 3 /6.
  • an inside region is defined as a region of from the center to the radius x0.3
  • a surface region is defined as a region of from the radius x0.95 to the radius x1.0.
  • each carrier (core) particle For each carrier (core) particle, the total volume per unit area ( ⁇ m 2 ) of magnetic iron compound particles and non-magnetic metal oxide particles respectively appearing in the inside region of the particle section concerned are calculated and denoted by Pa1 and Pb1 respectively, and the total volumes per unit area ( ⁇ m 2 ) of magnetic iron compound particles and non-magnetic metal oxide particles respectively appearing in the surface region are calculated and denoted by Pa2 and Pb2, respectively.
  • the values Pa1, Pb1, Pa2 and Pb3 are averaged with respect to 20 carrier (core) particles for calculation of ratios Pa1/Pb1 and Pa2/Pb2.
  • a sample compound or metal oxide is placed between and so as to evenly contact the electrodes 21 and 22 in a cell shown in Figure 2 and, under this state, a voltage is applied between the electrodes to measure a current passing therebetween as a result, from which a resistivity is calculated.
  • the sample is packed while reciprocally rotating the lower electrode 21.
  • a surfactant alkylbenzenesulfonic acid salt
  • the sample liquid is supplied to a Coulter counter ("Multisizer", available from Coulter Electronics Inc.) with an aperture size of, e.g., 17 ⁇ m or 100 ⁇ m to obtain a volume-basis particle size distribution in the range of 2 - 40 ⁇ m, from which a number-basis particle size distribution, a number-average particle size (D1) and a weight-average particle size (D4) are calculated by a personal computer.
  • a Coulter counter (“Multisizer", available from Coulter Electronics Inc.) with an aperture size of, e.g., 17 ⁇ m or 100 ⁇ m to obtain a volume-basis particle size distribution in the range of 2 - 40 ⁇ m, from which a number-basis particle size distribution, a number-average particle size (D1) and a weight-average particle size (D4) are calculated by a personal computer.
  • Multisizer available from Coulter Electronics Inc.
  • a toner and a magnetic carrier are weighed to provide a mixture containing 5 wt. % of the toner, and the mixture is subjected to mixing for 60 sec. by a Turbula mixer.
  • the resultant powder mixture (developer) is placed in a metal container equipped with a 500-mesh electroconductive screen at the bottom, and the toner in the developer is selectively removed by sucking at a suction pressure of 250 mmHg through the screen by operating an aspirator.
  • the magnetic carrier core particles were surface-coated with a thermosetting silicone resin in the following manner. So as to provide a coating resin rate of 1.0 wt. %, a 10 wt. % carrier coating resin solution in toluene was prepared. Into the solution, the carrier core particles were added, and the resultant mixture was heated under the action of a shearing force to vaporize the solvent to provide a coating on the carrier core. The resultant coated magnetic carrier particles were subjected to curing for 1 hour at 250 °C, followed by disintegration and sieving through a 100-mesh sieve, to obtain coated magnetic carrier particles, which showed a number-average particle size (D1) of 43 ⁇ m and a sphericity (SF1) of 1.04.
  • D1 number-average particle size
  • SF1 sphericity
  • the coated magnetic carrier showed a resistivity (Rs) of 9x10 13 ohm.cm and a saturation magnetization ⁇ s of 28 emu/g.
  • the properties of the coated magnetic carrier are inclusively shown in Table 1 appearing hereinafter.
  • toners were prepared in the following manner.
  • Polyester resin 100 parts (condensation product between bisphenol and fumaric acid) C.I. Pigment Yellow (colorant) 4.5 parts Cr-complex salt of di-t-butyl-salicylic acid (negative charge control agent, pale) 4 parts
  • the materials were sufficiently preliminarily blended, melt-kneaded, cooled and coarsely crushed by a hammer mill into particle sizes of ca. 1 - 2 mm. Then, the product was further pulverized by an air jet-type pulverizer. The pulverizate was classified by an Elbow Jet classifier to recover a negatively chargeable yellow powder (non-magnetic yellow toner).
  • the yellow toner showed a weight-average particle size (D4) of 8.6 ⁇ m, a number-average particle size (D1) of 6.5 ⁇ m, and a ratio (D4/D1) of 1.32.
  • the toner showed a triboelectric charge (TC) of -27.1 ⁇ C/g when measured together with the above-prepared coated magnetic carrier (at a toner concentration of 5 wt. %).
  • Polyester resin 100 parts (same as for yellow toner) C.I. Pigment Red 122 4 parts
  • C.I. Basic Red 12 1 part Cr-complex salt of di-t-butyl-salicylic acid 4 parts
  • a negatively chargeable magenta powder (non-magnetic magenta toner) was prepared in the same manner as the yellow toner.
  • magenta toner 100 wt. parts of the above magenta toner, and 8.0 wt. part of hydrophobized titanium oxide fine powder were blended with each other in a Henschel mixer to obtain a magenta toner carrying the titanium oxide fine powder externally added thereto.
  • the toner showed a triboelectric charge (TC) of -25.3 ⁇ C/g when measured together with the above-prepared coated magnetic carrier.
  • Polyester resin 100 parts (same as for yellow toner) Copper-phthalocyanine pigment 5 parts Cr-complex salt of di-t-butyl-salicylic acid 4 parts
  • a negatively chargeable cyan powder (non-magnetic cyan toner) was prepared in the same manner as the yellow toner.
  • cyan toner 100 wt. parts of the above cyan toner, and 0.8 wt. part of hydrophobized titanium oxide fine powder were blended with each other in a Henschel mixer to obtain a cyan toner carrying the titanium oxide fine powder externally added thereto.
  • the toner showed a triboelectric charge (TC) of -27.8 ⁇ C/g when measured together with the above-prepared coated magnetic carrier.
  • a negatively chargeable black powder (non-magnetic black toner) was prepared in the same manner as the yellow toner.
  • the toner showed a triboelectric charge (TC) of -26.3 ⁇ C/g when measured together with the above-prepared coated magnetic carrier.
  • each developing device was designed to have a spacing A of 600 ⁇ m between a developer carrying member (developing sleeve) 1 and a developer-regulating member (magnetic blade) 2, and a gap B of 500 ⁇ m between the developing sleeve 1 and an electrostatic latent image-bearing member (photosensitive drum) 3.
  • a developing nip C at that time was 5 mm.
  • the developing sleeve 1 and the photosensitive drum 3 were driven at a peripheral speed ratio of 1.75:1.
  • a developing sleeve S1 of the developing sleeve was designed to provide a magnetic field of 1 kilo-oersted, and the developing conditions included an alternating electric field of a rectangular waveform having a peak-to-peak voltage of 2000 volts and a frequency of 2000 Hz, a developing bias of -470 volts, a toner developing contrast (Vcont) of 325 volts, a fog removal voltage (Vback) of 100 volts, and a primary charge voltage on the photosensitive drum of -570 volts.
  • Vcont toner developing contrast
  • Vback fog removal voltage
  • a digital latent image on the photosensitive drum 3 was developed by a reversal development mode.
  • the resultant images showed a high solid part image density (representatively as measured at a cyan toner image portion), were free from roughening of dots, and showed no image disorder or fog at the image or non-image portion due to carrier attachment.
  • a continuous full-color image formation was performed on a large number of 30,000 sheets. Thereafter, an imaging test was performed similarly as the initial stage.
  • the solid image of cyan toner showed a high density, and the halftone showed a good reproducibility. Further, no fog or carrier attachment was observed.
  • the cyan developer after the continuous image formation was observed through a SEM (scanning electron microscope), the peeling of the coating resin on the carrier was not observed, but a good surface state similarly as that of the initial coated magnetic carrier surface.
  • Example 2 The above materials were subjected to polymerization similarly as in Example 1 except for changing the amounts of the basic catalyst and water.
  • the polymerizate particles were classified to obtain a magnetic-powder dispersed carrier core.
  • the resultant carrier core showed a resistivity (Rs) of 5.2x10 12 ohm.cm.
  • the core particles were coated with a coating resin mixture of styrene-acrylate resin/fluorine-containing resin of 7/3 at a coating rate of 1.0 wt. % otherwise in a similar manner as in Example 1.
  • the thus-obtained coated magnetic carrier was blended with the four color toners prepared in Example 1 to prepare four two-component type developers each having a toner concentration of 7 wt. %.
  • the respective toners showed triboelectric charges of yellow: -30.2 ⁇ C/g, magenta: -28.7 ⁇ C/g, cyan: -32.9 ⁇ C/g and black: -29.8 ⁇ C/g, respectively, when measured at a toner concentration of 5 wt. %.
  • the developers were charged in the same image forming apparatus and used for development under the same developing conditions as in Example 1.
  • images at the initial stage showed particularly excellent dot and thin-line reproducibility and high resolution, and were free from carrier attachment.
  • the images thereafter showed almost similar image qualities as those at the initial stage. No carrier attachment was observed in the continuous image formation.
  • the surface of the carrier after the continuous image formation was similarly good as that at the initial stage.
  • a magnetic carrier core was prepared through two-step polymerization by using the following materials.
  • the first step polymerization was performed similarly as in Example 1 except for changing the amounts of the basic catalyst and water.
  • the above-mentioned materials for the second step was charged and subjected to similar suspension polymerization to obtain polymerizate particles.
  • the polymerizate particles were classified to obtain magnetic powder-dispersed resin carrier core particles.
  • a core particle showed a section as schematically shown in Figure 4 wherein the magnetite particles were present inside and larger ⁇ -Fe 2 O 3 particles were present at the surface.
  • the core particles were coated with the same coating resin as in Example 1 but at a different coating rate of 1.3 wt. %.
  • the thus-obtained coated magnetic carrier was blended with the four color toners prepared in Example 1 to prepare four two-component type developers each having a toner concentration of 8 wt. %.
  • the respective toners showed triboelectric charges of yellow: -25.1 ⁇ C/g, magenta: -24.3 ⁇ C/g, cyan: -27.7 ⁇ C/g and black: -23.0 ⁇ C/g.
  • the developers were charged in the same image forming apparatus and used for development under the same developing conditions as in Example 1 except for changing the spacing A between the developing sleeve 1 and the magnetic blade 2 to 800 ⁇ m.
  • obtained images showed excellent dot reproducibility and high resolution, and were free from carrier attachment.
  • the images thereafter showed almost similar image qualities as those at the initial stage. No carrier attachment was observed in the continuous image formation.
  • the surface of the carrier after the continuous image formation was similarly good as that at the initial stage.
  • Example 2 The above materials were subjected to polymerization similarly as in Example 1.
  • the polymerizate particles were classified to obtain a magnetic powder dispersed resin carrier core.
  • the core particles were coated with the same coating resin as in Example 1 but at a different coating rate of 2.0 wt. %.
  • a toner was prepared in the following ingredients.
  • Polyester resin (same as in Ex. 1) 100 parts Copper-phthalocyanine pigment 6 parts Cr-complex salt of di-t-butylsalicylic acid 5 parts
  • negatively chargeable cyan powder (cyan toner) was prepared in the same manner as in Example 1 except for changing the pulverization and classification conditions.
  • One hundred parts of the cyan toner and 1.5 wt. parts of hydrophobized titanium oxide fine powder were blended with each other in a Henschel mixer to obtain a cyan toner carrying the titanium fine powder externally added thereto.
  • the cyan toner was blended with the coated magnetic carrier at a toner concentration of 8 wt. % and subjected to mono-color-mode image formation in the same developing apparatus and under the same developing conditions as in Example 1. As a result, good images were obtained both at the initial stage and after continuous image formation on 30,000 sheets similarly as in Example 1.
  • the carrier surface state after the continuous image formation was similar as that at the initial stage.
  • the carrier core prepared in Example 1 was used as a magnetic carrier without coating, and blended with the same four toners as in Example 1 to prepare four developers each having a concentration of 8 wt. %.
  • the respective toners showed triboelectric charges of yellow: -38.4 ⁇ C/g, magenta: -35.7 ⁇ C/g, cyan: -39.4 ⁇ C/g and black: -36.6 ⁇ C/g.
  • Example 2 The developers were charged in the same image forming apparatus and used for development under the same developing conditions as in Example 1. As a result, similarly as in Example 1, images at the initial stage showed high resolution, and were free from carrier attachment. As a result of a continuous full-color image formation on 30,000 sheets, the images thereafter showed almost similar image qualities as those at the initial stage. No carrier attachment was observed in the continuous image formation.
  • Example 2 The above materials were subjected to polymerization similarly as in Example 1.
  • the polymerizate particles were classified to form a magnetic powder dispersed resin carrier core.
  • the core particles were coated with styrene/2-ethylhexyl methacrylate (50/50) copolymer otherwise similarly as in Example 1 to provide a coating rate of 1.2 wt. %.
  • the thus-obtained coated magnetic carrier was blended with the cyan toner prepared in Example 1 to prepare a developer.
  • the toner showed a triboelectric charge of -27.2 ⁇ C/g.
  • the developer was charged in the same image forming apparatus and used for mono-color-mode development under the same developing conditions as in Example 1. As a result, good image qualities were obtained both at the initial stage and after 30,000 sheets of continuous image formation similarly as in Example 1.
  • the carrier attachment prevention performance was good both before and after the continuous image formation.
  • the carrier surfaces after the continuous image formation were good similarly as those at the initial stage.
  • Fe 2 O 3 , CuO and ZnO were weighed so as to provide a composition of 50 mol. %, 27 mol. % and 23 mol. %, respectively, and were mixed with each other by a ball mill.
  • the mixture was calcined at 1000 °C, and pulverized by a ball mill.
  • the resultant powder in 100 parts, 0.5 part of polysodium methacrylate and water were mixed with each other in a wet ball mill to form a slurry.
  • the slurry was formed into particles by a spray drier.
  • the carrier was surface-coated with a resin in the same manner as in Example 1.
  • the thus-obtained carrier was blended with the cyan color toner prepared in Example 1 to prepare developer.
  • the cyan toner showed a triboelectric charge of -26.9 ⁇ C/g.
  • the developer was charged in the same image forming apparatus and used for monocolor-mode development under the same developing conditions as in Example 1.
  • the resultant images showed a high solid part image density but were inferior with respect to roughening of dots and halftone reproducibility.
  • Image disorder due to carrier attachment was not recognized at the image part or non-image part, but toner fog was recognized.
  • melt-sticking of toner was observed on the carrier. Images formed after the continuous image formation were accompanied with further inferior roughening of halftone part and further inferior fog.
  • the core particles were coated similarly as in Example 1.
  • the thus-obtained coated magnetic carrier was blended with the cyan toner prepared in Example 1 to prepare a developer.
  • the cyan toner showed a triboelectric charge of -28.8 ⁇ C/g.
  • the developer was charged in the same image forming apparatus and used for monocolor-mode development under the same developing conditions as in Example 1. As a result, halftone images at the initial stage were accompanied with roughening, and carrier attachment was recognized.
  • the core particles were coated similarly as in Example 1.
  • the thus-obtained coated magnetic carrier was blended with the cyan toner prepared in Example 1 to prepare a developer.
  • the cyan toner showed a triboelectric charge of -30.8 ⁇ C/g.
  • the developer was charged in the same image forming apparatus and used for development under the same developing conditions as in Example 3. As a result, the carrier attachment prevention was good, but halftone images were accompanied with some disorder of dot shape and recognizable roughening.
  • the carrier was the same coated carrier as in Example 1.
  • a cyan toner was prepared from the same composition and in the same manner as in Example 1 but under different pulverization and classification conditions.
  • the toner was blended with 0.5 wt. % of titanium oxide externally added thereto similarly as in Example 1.
  • the cyan toner showed a triboelectric charge of -20.1 ⁇ C/g when measured together with the above prepared magnetic carrier at a toner concentration of 5 wt. %.
  • the cyan toner was blended with the above coated magnetic carrier to prepare a developer.
  • the developer was charged in the same image forming apparatus and used for monocolor-mode development under the same developing conditions as in Example 1. As a result, high image density was obtained but halftone images showed somewhat inferior dot reproducibility and were accompanied with roughening.
  • Example 1 100 wt. parts of the carrier core prepared in Example 1 was blended with a coating liquid containing 2 parts of thermosetting phenolic resin and 6 parts of ⁇ -Fe 2 O 3 (same as used in Example 1) at a concentration of 10 % in toluene, and the solvent was evaporated under the application of a shearing force to effect the coating. Further, the resin was cured at 160 °C under the application of a shearing force to form coated magnetic carrier particles. The coated carrier particles were then disintegrated and classified.
  • a coating liquid containing 2 parts of thermosetting phenolic resin and 6 parts of ⁇ -Fe 2 O 3 (same as used in Example 1) at a concentration of 10 % in toluene, and the solvent was evaporated under the application of a shearing force to effect the coating. Further, the resin was cured at 160 °C under the application of a shearing force to form coated magnetic carrier particles. The coated carrier particles were then disintegrated and classified.
  • the thus-obtained coated magnetic carrier was blended with the four-color toners prepared in Example 1 to prepare four two-component type developers each having a toner concentration of 8.0 wt. %.
  • the respective toners showed triboelectric charges of yellow: -25.5 ⁇ C/g, magenta: -25.1 ⁇ C/g, cyan: -25.9 ⁇ C/g, and black: -24.3 ⁇ C/g.
  • the developers were charged in the same image forming apparatus and used for development under the same developing conditions. As a result, images having an excellent halftone reproducibility and a high image density were obtained. Particularly, the triboelectric charges of the toner during the continuous image formation were stable.
  • Example 7 The coated magnetic carrier prepared in Example 7 was further coated with the same silicone resin as used in Example 1 in a similar manner as in Example 1.
  • the thus-obtained coated magnetic carrier was blended with the four-color toners prepared in Example 1 to prepare four two-component type developers each having a toner concentration of 8.0 wt. %.
  • the respective toners showed triboelectric charges of yellow: -23.0 ⁇ C/g, magenta: -22.5 ⁇ C/g, cyan: -24.4 ⁇ C/g, and black: -23.2 ⁇ C/g.
  • the developers were charged in the same image forming apparatus and used for development under the same developing conditions. As a result, images having an excellent halftone reproducibility and a high image density were obtained. Particularly, the developers showed a broad latitude of Vback for preventing fog and carrier attachment, and excellent stabilities.
  • a magnetic carrier core was prepared through two-step polymerization by using the following materials.
  • Phenol 2.5 parts Formalin (same as in Ex. 1) 1.5 parts Magnetite (same as in Ex. 1 5 parts ⁇ -Fe 2 O 3 (same as in Ex. 1) 9 parts
  • the core particles were coated similarly as in Example 1.
  • the thus-obtained coated magnetic carrier was blended with the four color toners prepared in Example 1 to prepare four two-component type developers each having a toner concentration of 8 %.
  • the respective toners showed triboelectric charges of yellow: -25.6 ⁇ C/g, magenta: -25.0 ⁇ C/g, cyan: -26.2 ⁇ C/g and black: -24.9 ⁇ C/g.
  • Example 2 The developers were charged in the same image forming apparatus and used for development under the same developing conditions as in Example 1. As a result, similarly as in Example 1, obtained images showed excellent halftone reproducibility and high image densities. Further, the images were free from image disorder image part and non-image part due to carrier attachment and also from toner fog. As a result of a continuous full-color image formation on 30,000 sheets, the resultant images were free from toner scattering, showed a high solid part image density, and good reproducibility of halftone and line images. No carrier attachment was observed in the continuous image formation. As a result of observation of the cyan developer through a SEM after the continuous image formation, no peeling of the coating was observed, and the surface state was similarly good as that of the carrier at the initial stage.
  • the polymerizate particles prepared in Example 9 was further subjected to coating with the polymerization of the following ingredients. Phenol 2 parts Formalin (same as in Ex. 1) 1.2 parts ⁇ -Fe 2 O 3 (same as in Ex. 1) 10 parts
  • the suspension polymerization was performed in the same manner as in Example 3 to obtain a spherical carrier core.
  • the core particles were coated with the same coating resin as in Example 2 but at a different coating rate of 1.0 wt. %.
  • the thus-obtained coated magnetic carrier was blended with the four color toners prepared in Example 1 to prepare four two-component type developers each having a toner concentration of 8 wt. %.
  • the respective toners showed triboelectric charges of yellow: -32.3 ⁇ C/g, magenta: -29.9 ⁇ C/g, cyan: -32.4 ⁇ C/g and black: -30.3 ⁇ C/g.
  • Example 2 The developers were charged in the same image forming apparatus and used for development under the same developing conditions as in Example 1. As a result, similarly as in Example 1, images obtained at the initial stage showed particularly good dot and thin-line reproducibilities and high resolution. Further, no toner scattering, fog or carrier attachment was observed. As a result of continuous full-color image formation on 30,000 sheets, the images thereafter showed almost similar image qualities as those at the initial stage. No toner scattering, fog or carrier attachment was observed in the continuous image formation. The surface of the carrier after the continuous image formation was similarly good as that at the initial stage.
  • the image density of a solid cyan image portion was measured by a Macbeth densitometer ("RD-918 Type" using SPI filter, mfd. by Macbeth Co.), as a relative density of an image printed on a sheet of plain paper.
  • the degree of roughening of halftone image portion was evaluated with eyes with reference to an original image and standard samples.
  • a transparent adhesive tape was applied onto a region of 5 cm x 5 cm between the developing region and the cleaner region on the photosensitive drum to recover magnetic carrier particles attached to the photosensitive drum.
  • the number of attached carrier particles attached in the region of 5 cm x 5 cm was counted, and evaluation was performed based on the number of attached carrier particles per cm 2 calculated therefrom according to the following standard:
  • the average reflection rate Dr (%) of the sheet of plain paper before printing was measured by a reflectometer ("REFLECTOMETER MODEL TC-6DS" mfd. by Tokyo Denshoku K.K.).
  • a solid white image was printed onto the sheet of plain paper, and the reflection rate Ds (%) of the solid white image was measured by the reflectometer.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Developing Agents For Electrophotography (AREA)

Claims (20)

  1. Zweikomponentenentwickler zum Entwickeln eines elektrostatischen Bildes, der mindestens einen Toner und einen magnetischen Träger enthält, wobei der Toner eine gewichtsgemittelte Partikelgröße D4 von maximal 10 µm und eine anzahlgemittelte Partikelgröße D1, die die Beziehung D4/D1 ≤ 1,5 erfüllt, besitzt und der magnetische Träger Verbundpartikel enthält, die Partikel aus einer magnetischen Eisenverbindung, Partikel aus einem nichtmagnetischen Metalloxid und ein Bindemittel umfassen, das ein Phenolharz aufweist, und wobei die Verbundpartikel die magnetische Eisenverbindung und das nichtmagnetische Metalloxid in einem Gesamtanteil von 80-99 Gew.% enthalten, die Partikel der magnetischen Eisenverbindung eine anzahlgemittelte Partikelgröße ra aufweisen und die Partikel des nichtmagnetischen Metalloxides eine anzahlgemittelte Partikelgröße rb besitzen, die die Beziehung rb/ra > 1,0 erfüllt.
  2. Entwickler nach Anspruch 1, bei dem die Partikel der magnetischen Eisenverbindung eine anzahlgemittelte Partikelgröße ra von 0,02-5 µm und die Partikel des nichtmagnetischen Metalloxides eine anzahlgemittelte Partikelgröße rb von 0,05-10 µm besitzen.
  3. Entwickler nach Anspruch 1 oder 2, bei dem die nichtmagnetischen Metalloxidpartikel in einer Menge von 5-70 Gew.% der Gesamtheit der Partikel aus der magnetischen Eisenverbindung und der Partikel aus dem nichtmagnetischen Metalloxid vorhanden sind und der magnetische Träger eine Schüttdichte von 1,0-2,0 g/cm3 aufweist.
  4. Entwickler nach einem der vorangehenden Ansprüche, bei dem der magnetische Träger auf seiner Oberfläche mit einem Harz beschichtet ist, das die Partikel des nichtmagnetischen Metalloxides enthält.
  5. Entwickler nach einem der vorangehenden Ansprüche, bei dem der magnetische Träger auf seiner Oberfläche mit 0,1-10 Gew.% des Harzes beschichtet ist.
  6. Entwickler nach einem der vorangehenden Ansprüche, bei dem der magnetische Träger eine Sättigungsmagnetisierung σs von 10-80 Am2/kg (10-80 emu/g) besitzt.
  7. Entwickler nach einem der vorangehenden Ansprüche, bei dem die magnetische Eisenverbindung Magnetit und das nichtmagnetische Metalloxid Hämatit aufweisen.
  8. Entwickler nach einem der vorangehenden Ansprüche, bei dem der Toner ein nichtmagnetischer Toner ist.
  9. Entwickler nach einem der vorangehenden Ansprüche, bei dem der magnetische Träger die Partikel der magnetischen Eisenverbindung und die Partikel des nichtmagnetischen Metalloxides in einer solchen Verteilung enthält, daß das Gesamtvolumen Pal der Partikel der magnetischen Eisenverbindung und das Gesamtvolumen Pb1 der Partikel des nichtmagnetischen Metalloxides, die jeweils im Inneren der Trägerpartikel oder Trägerkernpartikel vorhanden sind, und das Gesamtvolumen Pa2 der Partikel der magnetischen Eisenverbindung und das Gesamtvolumen Pb2 der Partikel des nichtmagnetischen Metalloxides, die auf einem Oberflächenbereich der Trägerpartikel oder Trägerkernpartikel vorhanden sind, die folgenden Beziehungen erfüllen: Pb1/Pa1 < 1 und Pb2/Pa2 > 1.
  10. Entwickler nach einem der vorangehenden Ansprüche, bei dem die magnetischen Trägerpartikel Trägerkernpartikel aufweisen, die mit 0,6-5 Gew.% eines Überzugsmateriales beschichtet sind.
  11. Entwickler nach Anspruch 10, bei dem die magnetischen Trägerpartikel Trägerkernpartikel umfassen, die mit 0,6-5 Gew.% eines Überzugsmateriales beschichtet sind.
  12. Entwickler nach einem der vorangehenden Ansprüche, bei dem der magnetische Träger eine Sphärizität von maximal 2 besitzt.
  13. Entwickler nach einem der vorangehenden Ansprüche, bei dem seine Trägerpartikel oder Trägerkernpartikel durch Vermischen eines Monomers, einer magnetischen Eisenverbindung und eines nichtmagnetischen Metalloxides und Unterziehen des Gemisches einer Polymerisation des Monomers hergestellt worden sind.
  14. Entwickler nach Anspruch 13, bei dem die Monomere Phenol und Formalin sind.
  15. Entwickler nach einem der vorangehenden Ansprüche, bei dem der magnetische Träger eine Sphärizität von 1,04 bis 1,11 besitzt.
  16. Verfahren zum Entwickeln eines elektrostatischen Bildes mit den folgenden Schritten:
    Vorsehen eines Entwicklerträgerelementes, das eine Magnetfelderzeugungseinrichtung umschließt;
    Ausbilden einer magnetischen Bürste aus dem Zweikomponentenentwickler nach einem der vorangehenden Ansprüche auf dem Entwicklerträgerelement,
    Herbeiführen eines Kontaktes der magnetischen Bürste mit einem Trägerelement für ein latentes Bild und
    Entwicklen eines elektrostatischen Bildes auf dem Trägerelement für das latente Bild zur Ausbildung eines Tonerbildes, während ein alternierendes elektrisches Feld an das Entwicklerträgerelement gelegt wird.
  17. Entwicklungsverfahren nach Anspruch 16, bei dem das elektrostatische Bild ein digitales Bild umfaßt.
  18. Entwicklungsverfahren nach Anspruch 16 oder 17, bei dem das elektrostatische Bild in einem Reversentwicklungsmodus entwickelt wird.
  19. Entwicklungsverfahren nach den Ansprüchen 16, 17 oder 18, bei dem die magnetische Bürste das Trägerelement für das latente Bild mit einem Entwicklungsspalt von 3-8 mm kontaktiert.
  20. Vollfarbbildausbildungsverfahren mit den folgenden Schritten:
    (a) Ausbilden eines elektrostatischen Bildes auf dem Trägerelement für ein latentes Bild und Entwickeln des Bildes mit Magentatoner durch das Verfahren nach einem der Ansprüche 16 bis 19;
    (b) Ausbilden eines elektrostatischen Bildes auf dem Trägerelement für ein latentes Bild und Entwickeln des Bildes mit Cyantoner durch das Verfahren nach einem der Ansprüche 16-19;
    (c) Ausbilden eines elektrostatischen Bildes auf dem Trägerelement für ein latentes Bild und Entwickeln des Bildes mit einem gelben Toner durch das Verfahren nach einem der Ansprüche 16-19 und Kombinieren der Magenta-, Cyan- und gelben Tonerbilder zur Ausbildung des Vollfarbbildes.
EP95306880A 1994-10-05 1995-09-29 Entwickler des Zweikomponententyps, Entwicklungsverfahren und Bildherstellungsverfahren Expired - Lifetime EP0708378B1 (de)

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JP26442894 1994-10-05
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EP0708378A2 EP0708378A2 (de) 1996-04-24
EP0708378A3 EP0708378A3 (de) 1996-05-01
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Cited By (1)

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Publication number Priority date Publication date Assignee Title
DE102005018675A1 (de) * 2005-01-20 2006-07-27 Eastman Kodak Co. Verfahren und Toner umfassendes Gemisch zur Entwicklung eines Tonerbildes auf einem Fotoleiter

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DE69706352T2 (de) * 1996-04-08 2002-04-25 Canon Kk Beschichtete magnetische Trägerteilchen, zwei-Komponententyp-Entwickler und Entwicklungsverfahren
EP0999477B1 (de) * 1998-11-06 2005-11-02 Toda Kogyo Corporation Elektrophotographischer magnetischer Träger
WO2009078493A1 (en) * 2007-12-19 2009-06-25 Ricoh Company, Ltd. Method for producing carrier for electrophotographic developer, carrier for electrophotographic developer, electrophotographic developer, and image forming method
EP2696244B1 (de) * 2012-08-08 2015-12-30 Canon Kabushiki Kaisha Magnetischer Träger und Zweikomponentenentwickler

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US2297691A (en) 1939-04-04 1942-10-06 Chester F Carlson Electrophotography
US4071361A (en) 1965-01-09 1978-01-31 Canon Kabushiki Kaisha Electrophotographic process and apparatus
JPS4223910B1 (de) 1965-08-12 1967-11-17
JPS57128347A (en) * 1981-02-03 1982-08-09 Ricoh Co Ltd Toner for electrophotographic dry type developer
JPS59104663A (ja) 1982-12-08 1984-06-16 Konishiroku Photo Ind Co Ltd 静電荷像現像用キヤリア
JPS60131549A (ja) 1983-12-20 1985-07-13 Konishiroku Photo Ind Co Ltd 現像方法
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DE102005018675A1 (de) * 2005-01-20 2006-07-27 Eastman Kodak Co. Verfahren und Toner umfassendes Gemisch zur Entwicklung eines Tonerbildes auf einem Fotoleiter

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EP0708378A3 (de) 1996-05-01
KR960015106A (ko) 1996-05-22
KR0163996B1 (ko) 1999-03-20
DE69519620D1 (de) 2001-01-18
EP0708378A2 (de) 1996-04-24
HK1014051A1 (en) 1999-09-17
CN1099054C (zh) 2003-01-15
CN1130767A (zh) 1996-09-11

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