EP0801335B1 - Magnetic coated carrier, two-component type developer and developing method - Google Patents

Magnetic coated carrier, two-component type developer and developing method Download PDF

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Publication number
EP0801335B1
EP0801335B1 EP97302356A EP97302356A EP0801335B1 EP 0801335 B1 EP0801335 B1 EP 0801335B1 EP 97302356 A EP97302356 A EP 97302356A EP 97302356 A EP97302356 A EP 97302356A EP 0801335 B1 EP0801335 B1 EP 0801335B1
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EP
European Patent Office
Prior art keywords
magnetic
metal oxide
coated carrier
particles
toner
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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EP97302356A
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German (de)
English (en)
French (fr)
Other versions
EP0801335A1 (en
Inventor
Yoshinobu Baba
Takeshi Ikeda
Yuko Sato
Hitoshi Itabashi
Yuzo Tokunaga
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Canon Inc
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Canon Inc
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Publication of EP0801335A1 publication Critical patent/EP0801335A1/en
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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
    • 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
    • G03G9/0821—Developers with toner particles characterised by physical parameters
    • 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
    • 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
    • G03G9/0827—Developers with toner particles characterised by their shape, e.g. degree of sphericity
    • 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
    • G03G9/1088—Binder-type carrier
    • G03G9/10882—Binder is obtained 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
    • G03G9/10—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
    • G03G9/10—Developers with toner particles characterised by carrier particles
    • G03G9/113—Developers with toner particles characterised by carrier particles having coatings applied thereto
    • G03G9/1132—Macromolecular components of coatings
    • 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
    • G03G9/113—Developers with toner particles characterised by carrier particles having coatings applied thereto
    • G03G9/1132—Macromolecular components of coatings
    • G03G9/1135—Macromolecular components of coatings obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
    • G03G9/1136—Macromolecular components of coatings obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds containing silicon atoms

Definitions

  • the present invention relates to a magnetic carrier for constituting a developer, a two-component type developer and a developing method for use in an image forming method, such as electrophotography and electrostatic recording.
  • electrostatic (latent) image development step charged toner particles are attached to an electrostatic (latent) image by utilizing electrostatic interaction with the electrostatic latent image, thereby forming a toner image.
  • the method using a two-component type developer comprising a mixture of a toner and a carrier has been suitably used in full-color copying machines and full-color printers requiring especially high image quality.
  • the magnetic carrier used in the two-component type developer there have been commercialized iron powder carrier, ferrite carriers and magnetic material-dispersed resin carriers.
  • An iron powder carrier because of its low resistivity, can cause a leakage of charge from an electrostatic image via the carrier to disturb the electrostatic image, thus resulting in image defects.
  • Even a ferrite carrier having a relatively high resistivity can fail in preventing charge leakage from an electrostatic image via the carrier in some cases, especially in a developing method including application of an alternating electric field.
  • the carrier has a large saturation magnetization, the magnetic brush is liable to be rigid, thus being liable to leave a brushing trace in the resultant and toner image.
  • a magnetic material-dispersed resin carrier wherein magnetic fine particles are dispersed in a binder resin.
  • the magnetic material-dispersed resin carrier compared with a ferrite carrier, has a relatively high resistivity, a small saturation magnetization and a small true specific gravity, so that the magnetic brush of the carrier is less rigid and can provide good toner images free from brushing trace.
  • the carrier is liable to cause carrier attachment. Further, if the carrier particle size is reduced along with the use of a smaller particle size toner, the carrier is liable to have a lower charge-imparting ability to a toner and result in a developer of a lower flowability.
  • JP-A 7-43951 has proposed a magnetic material-dispersed resin carrier having a prescribed particle size distribution.
  • the JP publication discloses a resin carrier production process wherein a magnetic material is kneaded together with a binder resin for dispersion, and the kneaded product after cooling is pulverized and classified, wherein the pulverization is improved to provide a sharp particle size distribution so as to solve the above problems.
  • the magnetic material-dispersed resin carrier prepared through the process is applicable to a monochromatic image formation but has a room for further improvement when it is applied to a full-color copying machine or a full-color printer requiring a high degree of color reproducibility.
  • a generic object of the present invention is to provide a magnetic coated carrier, a two-component type developer and a developing method using such a two-component type developer, having solved the above-mentioned problems.
  • a more specific object of the present invention is to provide a magnetic coated carrier capable of exhibiting an excellent toner-chargeability especially in combination with a small-particle size toner and free from carrier attachment, a two-component type developer including such a magnetic coated carrier, and a developing method using the two-component type developer.
  • Another object of the present invention is to provide a magnetic coated carrier showing excellent flowability and capable of obviating image deterioration and liberation of metal oxide particles even in a continuous image formation on a large number of sheets, a two-component type developer including such a magnetic coated carrier, and a developing method using the two-component type developer.
  • a further object of the present invention is to provide a two-component type developer capable suppressing the occurrence of fog and adapted to a cleaner-less image forming process, and a developing method using the two-component type developer.
  • Another object of the present invention is to provide a two-component type developer adapted to a low-temperature fixation process and a cleaner-less process, having an improved durability in repetitive use and free from filming on a photosensitive member and a developing method using the two-component type developer.
  • Another object of the present invention is to provide a stable developing method adapted to a low-temperature fixation process and free from melt-sticking of the developer on a developer-carrying member for a long period.
  • a magnetic coated carrier comprising: magnetic coated carrier particles comprising magnetic carrier core particles each comprising a binder resin and metal oxide particles, and a coating layer surface-coating each carrier core particle, wherein
  • a two-component type developer for developing an electrostatic image comprising: a toner and the above-mentioned magnetic coated carrier.
  • a developing method comprising: carrying the above-mentioned two-component type developer on a developer-carrying member enclosing therein a magnetic field generating means, forming a magnetic brush of the two-component type developer on the developer-carrying member, causing the magnetic brush to contact an image-bearing member, and developing an electrostatic image on the image-bearing member while applying an alternating electric field to the developer-carrying member.
  • Figure 1 is a schematic illustration of a developing section of an image forming apparatus suitable for practicing an embodiment of the developing method according to the invention.
  • Figure 2 is an illustration of an apparatus for measuring the (electrical) resistivity of a carrier, a carrier core, and a non-magnetic metal oxide.
  • Figure 3 is a schematic illustration of a surface unevenness state of a developer-carrying member.
  • Figure 4 is a schematic view of a full-color image forming apparatus to which the developing method according to the invention is applicable.
  • a magnetic coated carrier having a broad particle size distribution is liable to cause carrier attachment (i.e., attachment of carrier particles onto an electrostatic (latent) image-bearing member) selectively with respect to its small particle size fraction.
  • carrier attachment i.e., attachment of carrier particles onto an electrostatic (latent) image-bearing member
  • toner-carrying performance of a carrier is also affected by its particle size distribution and a carrier having a broad particle size distribution is liable to result in an unstable triboelectric charge of toner due to a lowering in flowability of the developer.
  • the flowability of a developer is also affected by the surface shape of toner particles in case of a small toner particle size.
  • a magnetic coated carrier having a shape factor SF-1 of 100 - 130 provides an improved flowability of the developer leading to a further improved toner-charging performance.
  • the magnetic coated carrier of the present invention has a number-average particle size (Dn) of 5 - 100 ⁇ m, preferably 10 - 70 ⁇ m. If Dn is smaller than 5 ⁇ m, it becomes difficult to well prevent the carrier attachment onto a non-image part due to a fine particle size fraction in the carrier particle size distribution. Dn larger than 100 ⁇ m can result in image irregularity due to its largeness while the brushing trace due to rigid magnetic brush can be obviated.
  • Dn number-average particle size
  • the carrier contains at most 25 % by number (cumulative) of particles having particle sizes of at most Dn x 2/3.
  • the proportion is preferably at most 15 % by number, further preferably at most 10 % by number, in order to better prevent the carrier attachment even in case of a fluctuation in developing bias (voltage) as a developing condition of an image forming apparatus concerned.
  • Dn/ ⁇ ⁇ 4.0 is preferred. Below 3.5, the flowability of the developer is lowered when combined with a small particle size toner having a weight-average particle size (D4) of 1 - 10 ⁇ m, thus resulting in an unstable toner-chargeability.
  • the binder resin constituting the carrier core particles used in the present invention may preferably be three-dimensionally crosslinked. This is because the control of carrier particle size distribution is closely related with the carrier production process.
  • a magnetic material-dispersed resin carrier has been generally produced through a process wherein a binder resin and magnetic powder in a prescribed blend ratio are melt-kneaded under heating and the kneaded product is, after being cooled, pulverized and classified to provide a carrier.
  • the particle size distribution can be narrowed to some extent through an improvement in the pulverization step as disclosed in JP-A 7-43951.
  • the occurrence of some fine powder fraction is inevitable.
  • the particulation of the polymerizable mixture is proceeded while the monomer is polymerized to be gelled simultaneously with the introduction of the metal oxide particles thereinto, thereby allowing the production of carrier core particles having a uniform particle size distribution and particularly with little fine powder fraction. Further, by three-dimensionally crosslinking the resin, the magnetic fine particles dispersed therein can be further firmly bound therewith.
  • the carrier particle size is also reduced corresponding to the toner.
  • D4 weight-average particle size
  • a radically polymerizable monomer examples of which may include: styrene; styrene deviatives, such as o-methylstyrene, m-methylstyrene, p-methoxystyrene, p-ethylstyrene, and p-tert-butylstyrene; acrylic acid, methacrylic acid; acrylate esters, such as methyl acrylate, ethyl acrylate, n-butyl acrylate, n-propyl acrylate, isobutyl acrylate, octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, and phenyl acrylate; methacrylate esters, such as methyl methacrylic acid; styrene deviatives, such as o-methyls
  • These monomers may be used singly or in mixture so as to provide a polymer composition exhibiting preferred properties.
  • the binder resin of the carrier core particles is three-dimensionally crosslinked.
  • a crosslinking agent it is preferred to use a compound having at least two polymerizable double bonds in one molecule.
  • examples of such a crosslinking agent may include: aromatic divinyl compounds, such as divinylbenzene and divinylnaphthalene; ethylene glycol diacrylate, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, 1, 4-butanediol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol dimethacrylate
  • the binder resin for the carrier core particles may also be produced from other monomers, examples of which may include: bisphenols and epichlorohydrin as starting materials for epoxy resins; phenols and aldehydes for phenolic resins; urea and aldehydes for urea resins, and melamine and aldehydes for melamine resins.
  • the most preferred binder resin may be phenolic resins as produced from starting materials, such as: phenol compounds, such as phenol, m-cresol, 3,5-xylene, p-alkylphenol, resorcin, and p-tert-butylphenol; and aldehyde compounds, such as formalin, para-formaldehyde, an furfural.
  • phenol compounds such as phenol, m-cresol, 3,5-xylene, p-alkylphenol, resorcin, and p-tert-butylphenol
  • aldehyde compounds such as formalin, para-formaldehyde, an furfural.
  • formalin para-formaldehyde
  • the basic catalyst may suitably be one ordinarily used for production of resol resins. Examples thereof may include: ammonia water, and amines, such as hexamethylenetetramine, diethyltriamine and polyethyleneimine.
  • the metal oxide for use in the carrier core particles of the carrier according to the present invention may comprise magnetite or ferrite as represented by the formula of MO ⁇ Fe 2 O 3 (or MFe 2 O 4 ), wherein M denotes a tri-valent, di-valent or monovalent metal ion.
  • M may include: Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Ba, Pb and Li.
  • M may represent one or plural species of metals.
  • Suitable examples of magnetic metal oxides may include: iron-based oxide materials, such as magnetite, Zn-Fe-based ferrite, Mn-Zn-Fe-based ferrite, Ni-Zn-Fe-based ferrite, Mn-Mg-Fe-based ferrite, Ca-Mn-Fe-based ferrite, Ca-Mg-Fe-based ferrite, Li-Fe-based ferrite, and Cu-Zn-Fe-based ferrite. It is also possible to use such a magnetic metal oxide in mixture with a non-magnetic metal oxide.
  • 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, CuO, ZnO, SrO, Y 2 O 3 and ZrO 2 .
  • a preferred type of combination of plural species of metal oxides may include a combination of a low-resistivity magnetic metal oxide and a high-resistivity magnetic or non-magnetic metal oxide.
  • a combination of a low-resistivity magnetic metal oxide and a high-resistivity non-magnetic metal oxide is particularly preferred.
  • 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 , magnetite and Ca-Mn-Fe-based ferrite, and magnetite and Ca-Mg-Fe-based ferrite.
  • magnetite and hematite is particularly preferred.
  • the metal oxide showing magnetism may preferably have a number-average particle size of 0.02 - 2 ⁇ m while it can vary depending on the number-average particle size of the carrier core particles.
  • a metal oxide showing magnetism and having a generally lower resistivity may preferably have a number-average particle size ra of 0.02 - 2 ⁇ m
  • another metal oxide preferably having a higher resistivity than the magnetic metal oxide (which may be non-magnetic) may preferably have a number-average particle size rb of 0.05 - 5 ⁇ m.
  • a ratio rb/ra may preferably exceed 1.0 and be at most 5.0.
  • a ratio rb/ra of 1.2 - 5 is further preferred. If the ratio is 1.0 or below, it is difficult to form a state that the metal oxide particles having a higher resistivity are exposed to the core particle surface, so that it becomes difficult to sufficiently increase the core resistivity and obtain an effect of preventing the carrier attachment. On the other hand, if the ratio exceeds 5.0, it becomes difficult to disperse the metal oxide particles in the resin, thus being liable to result in a lower mechanical strength of the magnetic carrier and liberation of the metal oxide. The method of measuring the particle size of metal oxides referred to herein will be described hereinafter.
  • the magnetic particles may preferably have a resistivity of at least 1x10 3 ohm.cm, more preferably at least 1x10 5 ohm.cm.
  • magnetic metal oxide particles may preferably have a resistivity of at least 1x10 3 ohm.cm, and preferably non-magnetic other metal oxide particles may preferably have a resistivity higher than that of the magnetic metal oxide particles.
  • the other metal oxide particles may have a resistivity of at least 10 8 ohm.cm, further preferably at least 1x10 10 ohm.cm.
  • the magnetic metal oxide 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 metal oxide 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 object of the present invention.
  • the method of measuring resistivities of metal oxides referred to herein will be described hereinafter.
  • the metal oxide-dispersed resin carrier core used in the present invention may preferably contain 50 - 99 wt. % of the metal oxide. If the metal oxide content is below 50 wt. %, the charging ability of the resultant magnetic carrier becomes unstable and, particularly in a low temperature-low humidity environment, the magnetic carrier is charged and is liable to have a remanent charge, so that fine toner particles and an external additive thereto are liable to be attached to the surfaces of the magnetic carrier particles. In excess of 99 wt. %, the resultant carrier particles are caused to have an insufficient strength and are liable to cause difficulties of carrier particle breakage and liberation of metal oxide fine particles from the carrier particles during a continuous image formation.
  • the magnetic metal oxide in the metal oxide-dispersed resin core containing two or more species of metal oxides dispersed therein, may preferably occupy 30 - 95 wt. % of the total metal oxides.
  • a content of below 30 wt. % may be preferred to provide a high-resistivity core, but results in a carrier exerting a small magnetic force, thus inviting the carrier attachment in some cases. Above 95 wt. %, it becomes difficult to increase the core resistivity.
  • the metal oxide contained in the metal oxide-dispersed resin carrier core has been subjected to a lipophilicity-imparting treatment ("lipophilization") so as to provide magnetic carrier core particles having a sharp particle size distribution and prevent the liberation of metal oxide particles from the carrier.
  • lipophilization a lipophilicity-imparting treatment
  • insolubilized polymerizable particles are gradually formed in the system as the polymerization proceeds while taking therein the metal oxide particles.
  • the lipophilization is believed to exhibit functions of promoting uniform and high-density taking-in of the metal oxide particle.
  • the lipophilization may preferably be performed as a surface-treatment with a coupling agent, such as a silane coupling agent, a titanate coupling agent or an aluminum coupling agent, or a surfactant. It is particularly preferred to effect a surface-treatment with a coupling agent, such as a silane coupling agent or a titanate coupling agent.
  • a coupling agent such as a silane coupling agent or a titanate coupling agent.
  • the silane coupling agent may have a hydrophobic group, an amino group or an epoxy group.
  • hydrophobic group may include alkyl group, alkenyl group, halogenated alkyl group, halogenated alkenyl group, phenyl group, halogenated phenyl group, or alkyl phenyl group.
  • a preferred class of silane coupling agents having a hydrophobic group may be those represented by the following formula: R m SiY n , wherein R denotes an alkoxy group, Y denotes an alkyl or vinyl group, and m and n are integers of 1 - 3.
  • Preferred examples of the silane coupling agent having a hydrophobic group may include: vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, methyltrimethoxysilane, methyltriethoxysilane, isobutyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, n-propyltrimethoxysilane, phenyltrimethoxysilane, n-hexadecyltrimethoxysilane, n-octadecyltrimethoxysilane, and vinyltris( ⁇ -methoxy)-silane.
  • silane coupling agent having a hydrophobic group selected from the group consisting of vinyltrichlorosilane, hexamethyldisilazane, trimethylsilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, ⁇ -chloroethyltrichlorosilane, ⁇ -chloroethyltrichlorosilane, and chloromethyldimethylchlorosilane.
  • a silane coupling agent having a hydrophobic group selected from the group consisting of vinyltrichlorosilane, hexamethyldisilazane, trimethylsilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane,
  • silane coupling agent having an amino group may include: ⁇ -aminopropyltrimethoxysilane, ⁇ -aminopropylmethoxydiethoxysilane, N- ⁇ -aminoethyl- ⁇ -aminopropyltrimethoxysilane, ⁇ -aminopropylmethyldiethoxysilane, N- ⁇ -aminoethyl- ⁇ -aminopropylmethyldimethoxysilane, ⁇ -2-aminoethylaminopropyltrimethoxysilane, and N-phenyl--aminopropyltrimethoxysilane.
  • silane coupling agent having an epoxy group may include: ⁇ -glycidoxypropylmethyldiethoxysilane, ⁇ -glycidoxypropyltriethoxysilane, and ⁇ -(3,4-epoxycyclohexyl)trimethoxysilane.
  • titanate coupling agent may include: isopropyltriisostearoyl titanate, isopropyltridodecylbenzenesulfonyl titanate, isopropyltris(dioctylpyrophosphate) titanate, isopropyltri(N-aminoethyl-aminoethyl) titanate, and isopropyl-4-aminobenzene-sulfonyl-di(dodecylbenzenesulfonyl) titanate.
  • the aluminum coupling agent may for example be acetoalkoxyaluminum diisopropylate.
  • the magnetic carrier core particles may be prepared by subjecting to polymerization a polymerization system formed by dissolving or dispersing the above-mentioned monomer and metal oxide particles in a solvent and adding thereto an initiator or catalyst and optionally a surfactant or dispersion stabilizer.
  • the solvent may comprise a substance wherein the monomer is soluble but the polymerizate thereof constituting the binder resin is insoluble to be precipitated as the polymerization proceeds.
  • Such a solvent may include: linear or branched aliphatic alcohols, such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, bert-butyl alcohol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, isopentyl alcohol, tert-pentyl alcohol, 1-hexanol, 2-methyl-1-pentanol, 4-methyl-2-pentanol, 2-ethylbutanol, 1-heptanol, 2-heptanol, 3-heptanol, 2-octanol, and 2-ethyl-1-hexanol; aliphatic hydrocarbons, such as pentane, 2-methylbutane, n-hexane, cyclohexane, 2-methylpentane, 2,2-dimethylbutane, 2,3-di
  • a dispersion stabilizer examples of which may include: polystyrene, polymethyl methacrylate, phenol novolak resin, cresol novolak resin, styrene-acrylic copolymer; vinyl ether polymers, such as polymethyl vinyl ether, polyethyl vinyl ether, polybutyl vinyl ether, and polyisobutyl vinyl ether; polyvinyl alcohol, polyvinyl acetate, styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, polyvinylpyrrolidone, polyhydroxystyrene, polyvinyl chloride, polyvinyl acetal, cellulose, cellulose acetate, nitrocellulose, alkylated celluloses, hydroxyalkylated celluloses such as hydroxymethylcellulose and hydroxypropylcellulose, saturated alkyl polyester resins, aromatic polyester resins, polyamide resins, polyacetals, and polycarbonate resins.
  • the polymerization of the above-mentioned monomer may be performed in the presence of a polymerization initiator, which may be a radical polymerization initiator.
  • polymerization initiator may include: azo-type polymerization initiators, such as 2,2'-azobis-(2,4-dimethylvaleronitrile), 2,2'-azobisisobutylonitrile, 1,1'-azobis(cyclohexane-2-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile; amidine compounds, such as 2,2'-azobis(2-aminodipropane)-dihydrochloride, 2,2'-azobis(N,N'-dimethyleneisobutylamidine), and 2,2'-azobis(N,N'-dimethyleneisobutylamidine; peroxide-type polymerization initiators such as benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide
  • Carrier core particles comprising a setting-type phenolic resin may be produced by polymerizing a phenol and an aldehyde in the presence of a basic catalyst in an aqueous medium containing metal oxide particles dispersed therein.
  • Examples of the basic catalyst may include ammonia water, hexamethylenetetramine, and diethyltriamine.
  • a chain transfer agent examples of which may include: halogenated hydrocarbons, such as carbon tetrachloride, carbon tetrabromide, dibromoethyl acetate, tribromomethyl acetate, dibromoethylbenzene, dibromoethane, and dichloroethane; diazothioether, hydrocarbon homologues, such as benzene, ethylbenzene and isopropylbenzene; mercaptans, such as tert-dodecylmercaptan, and n-dodecylmercaptan; and disulfides, such as diisopropylxanthogene disulfides.
  • halogenated hydrocarbons such as carbon tetrachloride, carbon tetrabromide, dibromoethyl acetate, tribromomethyl acetate, dibromoethylbenzene, dibromoe
  • the monomer and the solvent form a uniform solution, and the metal oxide particles have been lipophilized. It is further preferred that the above ingredients are sufficiently dispersed in advance of the polymerization, followed by addition of a catalyst or polymerization initiator to initiate the polymerization so as to provide a sharp particle size distribution of magnetic carrier core particles.
  • the resultant polymerizate particles are washed with the solvent, dried, e.g., by vacuum drying and optionally subjected to classification to provide a narrower particle size distribution.
  • the classification may be performed by using vibrating sieves or a multi-division classifier utilizing an inertia force so as to remove fine and coarse powder fractions.
  • the magnetic coated carrier according to the present invention may be obtained by coating the above-prepared magnetic carrier core particles with an appropriate coating material.
  • the coating rate may preferably be 0.1 - 10 wt. %, more preferably 0.3 - 5 wt. %.
  • the coating may preferably be performed so as to provide a metal oxide particle-exposure density at the carrier core particle surface of 0.1 - 10 particles/ ⁇ m 2 , more preferably 0.5 - 5 particles/ ⁇ m so as to well prevent the carrier attachment and prevent the excessive charge-up of the toner.
  • the coating rate is below 0.1 wt. %, the effect of coating the carrier core particles is low, thus resulting in a lower toner-chargeability (i.e., a lower ability of triboelectrically charging the toner) especially after a continuous image formation.
  • the coating rate exceeds 10 wt. %, the carrier flowability is liable to be lowered, thus resulting in inferior images during continuous image formation on a large number of sheets.
  • the method of determining the metal oxide particle-exposure density at the carrier core particle surface will be described later.
  • the coating material may comprise a thermoplastic resin or a thermosetting resin.
  • the thermoplastic resin may include: polystyrene resin, polymethyl methacrylate resin, styrene-acrylate copolymer, acrylic resin, 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 acetate, nitrocellulose, methylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, cellulose derivative, novolak resin, low-molecular weight polyethylene, saturated alkyl polyester resin, polyethylene terephthalate, polybutylene terephthalate, aromatic polyester resins such as polyarylate, polyamide resin
  • thermosetting resin may include: phenolic resin, modified phenolic resin, maleic resin, alkyd resin, epoxy resin, acrylic resin, unsaturated polyester formed by polycondensation of maleic anhydride-terephthalic acid-polyhydric alcohol, urea resin, melamine resin, urea-melamine resin, xylene resin, toluene resin, guanamine resin, melamine-guanamine resin, acetoguanamine resin, glyptal resin, furan resin, silicone resin, acryl-modified silicone resin, epoxy-modified silicone resin, silicone alkyd resin, polyimide, polyamideimide resin, polyetherimide resin, and polyurethane resin. These resins may be used singly or in mixture. Further, a thermoplastic resin may be subjected to curing by mixing a curing agent.
  • the magnetic coated carrier may preferably be produced 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 by spray drying.
  • This coating method may suitably be used for coating the magnetic carrier-dispersed resin core particles with a thermoplastic resin.
  • 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.
  • the magnetic coated carrier according to the present invention may preferably designed to be substantially spherical in shape as represented by a shape factor SF-1 in the range of 100 - 130. If SF-1 exceeds 130, 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.
  • SF-1 shape factor
  • MX LNG denotes the maximum diameter of a carrier particle
  • AREA denotes the projection area of the carrier particle.
  • a magnetic carrier exerting a low magnetic force as represented by a magnetization of 40 - 250 emu/cm 3 , more preferably 50 - 230 emu/cm 3 , respectively at 1 kilo-oersted.
  • 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 250 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 long and rigid ears, thus being liable to result in rubbing traces in the resultant toner images, and deterioration of the developer during a continuous image formation.
  • image defects such as roughening of halftone images and irregularity of solid images, are liable to occur particularly due to deterioration of the toner.
  • the magnetic carrier is caused to exert only an insufficient magnetic force to result in a lower toner-conveying performance, and toner attachment, even if the fine powder fraction of the carrier is removed.
  • 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 toner used in the present invention may have a weight-average particle size (D4) of 1 - 10 ⁇ m, preferably 3 - 8 ⁇ m. Further, in order to effect good triboelectrification free from occurrence of reverse charge fraction and good reproducibility of latent image dots, it is preferred to satisfy such a particle size distribution that the toner particles contain at most 20 % by number in accumulation of particles having particle sizes in the range of at most a half of the number-average particle size (D1) thereof and contain at most 10 % by volume in accumulation of particles having particle sizes in the range of at least two times the weight-average particle size (D4) thereof.
  • D4 weight-average particle size
  • the toner particles contain at most 15 % by number, further preferably at most 10 % by number, of particles having sizes of at most 1/2 x D1, and at most 5 by volume, further preferably at most 2 % by volume of particles having sizes of at least 2xD4.
  • 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 even if the magnetic force of the magnetic carrier is lowered, and extensive toner scattering is caused when subjected to electrostatic transfer. If D4 is below 1 ⁇ m, the toner causes difficulties in powder handling characteristic.
  • D4 weight-average particle size
  • the triboelectrification of such fine toner particles cannot be satisfactorily effected to result in difficulties, such as a broad triboelectric charge distribution of the toner, charging failure (occurrence of reverse charge fraction) and a particle size change during continuous image formation due to localization of toner particle sizes.
  • the cumulative amount of particles having sizes of at least two times the weight-average particle size (D4) exceeds 10 % by volume, the triboelectrification with the metal oxide becomes difficult, and faithful reproduction of latent images becomes difficult.
  • the toner particle size distribution may be measured, e.g., by using a laser scanning-type particle size distribution meter (e.g., "CIS-100", available from GALIA Co.).
  • the particle size and particle size distribution of the toner used in the present invention are closely associated with the particle size and its distribution of the magnetic carrier.
  • the magnetic carrier has a number-average particle size of 15 - 50 ⁇ m
  • it is preferred that the toner has a weight-average particle size of 3 - 8 ⁇ m and both the toner and the carrier have narrow particle size distributions so as to provide a good chargeability and high-quality images.
  • the toner has a shape factor SF-1 of 100 - 140, and has been produced through a directed polymerization process while leaving a residual monomer content (Mres) of at most 1000 ppm.
  • the residual toner at a light potential part to be developed is allowed to remain thereat but the residual toner at a dark potential part is attracted to the developer-carrying member under the action of a developing field, thus being removed.
  • the performances, such as continuous image forming characteristic, of a developer in the simultaneous development and clearing system or cleaner-less image forming system is closely associated with the magnetic force of the carrier and the residual monomer content in the toner.
  • the effect of the carrier has been described above.
  • the residual monomer content has influences as follows.
  • the residual monomer is contained in the toner particles and affects the thermal behavior around the glass transition point of the toner.
  • the monomer is a low-molecular weight component so that it functions to plasticize the toner particles.
  • the toner subjected to discharging or corona shower receives an actinic action thereof on its binder layer.
  • the monomer chains in the resin may be severed to result in resin decomposition products and low-molecular weight components or, reversely, the resin decomposition product may promote the polymerization.
  • the residual monomer in the toner may be activated by the actinic function of the charging member for the photosensitive member.
  • the toner contains reactive low-molecular weight components which compete with each other.
  • the charge control agent contained in the toner particles is also a compound relatively rich in electron donating and receiving actions. For these factors in combination which have not been fully clarified as yet, the presence of residual monomer promotes gradual change in surface properties of the toner particles, such as toner flowability and chargeability.
  • the toner may preferably have a low residual monomer content of at most 1000 ppm, more preferably at most 500 ppm, further preferably at most 300 ppm, so as to provide good continuous image forming characteristic and good quality images.
  • the method of determining the residual monomer content in a toner will be described later.
  • the toner may preferably have a shape factor SF-1 of 100 - 140, more preferably 100 - 130. This is particularly effective in a simultaneous developing and cleaning system or a cleaner-less image forming system.
  • the shape factor SF-1 represents a sphericity, and SF-1 exceeding 140 means an indefinite shape different from a sphere. If the toner has a SF-1 exceeding 140, the toner is liable to provide a lower toner transfer efficiency from a photosensitive member to a transfer material and leave much residual toner on the photosensitive member.
  • toner particles prepared directly through a polymerization process may have a shape factor SF-1 close to 100 and have a smooth surface. Because of the surface smoothness, an electric field concentration occurring at the surface unevennesses of the toner particles can be alleviated to provide an increased transfer efficiency or transfer rate.
  • the toner particles used in the present invention may preferably have a core/shell structure (or a pseudo-capsule structure). Such toner particles having a core/shell structure may be provided with a good anti-blocking characteristic without impairing the low-temperature fixability.
  • a toner having a core/shell structure prepared by forming a shell enclosing a core of a low-softening point substance through polymerization allows easier removal of the residual monomer from the toner particles in a post-treatment step after the polymerization step.
  • the core principally comprises a low-softening point substance.
  • the low-softening point substance may preferably comprise a compound showing a main peak at a temperature within a range of 40 - 90 °C on a heat-absorption curve as measured according to ASTM D3418-8. If the heat-absorption main peak temperature is below 40 °C, the low-softening point substance is liable to exhibit a low self-cohesion leading to a weak anti-high temperature offset characteristic. On the other hand, if the heat-absorption peak temperature is above 90 °C, the resultant toner is liable to provide a high fixation temperature.
  • toner particle preparation through the direct polymerization process including particle formation and polymerization within an aqueous medium, if the heat-absorption main peak temperature is high, the low-softening point substance is liable to precipitate during particle formation of a monomer composition containing the substance within an aqueous medium.
  • the heat-absorption peak temperature measurement may be performed by using a scanning calorimeter ("DSC-7", available from Perkin-Elmer Corp.).
  • the temperature correction for the detector of the apparatus may be made based on the melting points of indium and zinc, and the heat quantity correction may be made based on the melting heat of indium.
  • a sample is placed on an aluminum-made pan, and a blank pan is also set as a control, for measurement at a temperature-raising rate of 10 °C/min. The measurement may be performed in a temperature range of 30 - 160 °C.
  • Examples of the low-softening point substance may include: paraffin wax, polyolefin wax, Fischer-Tropsche wax, amide wax, higher fatty acid, ester wax, and derivatives and graft/or block copolymerization products of these waxes.
  • the low-softening point substance may preferably be added in a proportion of 5 - 30 wt. % of the toner particles.
  • the toner particles may suitably be blended with an external additive. If the toner particles are coated with such an external additive, the external additive is caused to be present between the toner particles and between the toner and carrier, thereby providing an improved flowability and an improved life of the developer.
  • the external additive may for example comprise powder of materials as follows: metal oxides, such as aluminum oxide, titanium oxide, strontium titanate, cerium oxide, magnesium oxide, chromium oxide, tin oxide, and zinc oxide; nitrides, such as silicon nitride carbides, such as silicon carbide; metal salts, such as calcium sulfate, barium sulfate, and calcium sulfate; aliphatic acid metal salts such as zinc stearate, and calcium stearate; carbon black, silica, polytetrafluoroethylene, polyvinylidene fluoride, polymethyl methacrylate, polystyrene, and silicone resin.
  • metal oxides such as aluminum oxide, titanium oxide, strontium titanate, cerium oxide, magnesium oxide, chromium oxide, tin oxide, and zinc oxide
  • nitrides such as silicon nitride carbides, such as silicon carbide
  • metal salts such as calcium sulfate, barium sul
  • These powders may preferably have a number-average particle size (D1) of at most 0.2 ⁇ m. If the average particle size exceeds 0.2 ⁇ m, the toner is caused to have a lower flowability, thus resulting in lower image qualities due to inferior developing and transfer characteristic.
  • D1 number-average particle size
  • Such an external additive may be added in an amount of 0.01 - 10 wt. parts, preferably 0.05 - 5 wt. parts, per 100 wt. parts of the toner particles.
  • Such external additives may be added singly or in combination of two or more species. It is preferred that such external additives have been hydrophobized (i.e., subjected to hydrophobicity-imparting treatment).
  • the external additive 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 according to nitrogen adsorption.
  • the toner particles and the external additive may be mixed with each other by means of a blender, such as a Henschel mixer.
  • the resultant toner may be blended with carrier particles to form a two-component type developer.
  • the two-component type developer may preferably contain 1 - 20 wt. %, more preferably 1 - 10 wt. %, of the toner.
  • the toner in the two-component type developer may preferably have a triboelectric charge of 5 - 100 ⁇ C/g, more preferably 5 - 60 ⁇ C/g. The method for measuring the toner triboelectric charge will be described later.
  • the toner particles may for example be produced through a process when a binder resin, a colorant and other internal additives are melt-kneaded, and the melt-kneaded product is the cooled, pulverized and classified.
  • the toner binder resin 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,
  • the toner particles may for example be produced through a suspension polymerization process for directly producing toner particles, a dispersion polymerization process for directly producing toner particles in an aqueous organic solvent medium in which a monomer is soluble but the resultant polymer is insoluble, or an emulsion polymerization process, as represented by a soap-free polymerization process, for directly producing toner particles by polymerization in the presence of a water-soluble polar polymerization initiator.
  • the suspension polymerization under normal pressure or an elevated pressure may particularly preferably be used in the present invention because an SF-1 of the resultant toner particles can readily be controlled in a range of 100 - 140 and fine toner particles having a sharp particle size distribution and a weight-average particle size of 4 - 8 ⁇ m can be obtained relatively easily.
  • An enclosed structure of the low-softening point substance in the toner particles may be obtained through a process wherein the low-softening point substance is selected to have a polarity in an aqueous medium which polarity is lower than that of a principal monomer component and a small amount of a resin or monomer having a larger polarity is added thereto, to provide toner particles having a core-shell structure.
  • the toner particle size and its distribution may be controlled by changing the species and amount of a hardly water-soluble inorganic salt or a dispersant functioning as a protective colloid; by controlling mechanical apparatus conditions, such as a rotor peripheral speed, a number of pass, and stirring conditions inclusive of the shape of a stirring blade; and/or by controlling the shape of a vessel and a solid content in the aqueous medium.
  • the outer shell resin of toner particles may comprise styrene-(meth)acrylate copolymer, or styrene-butadiene copolymer. In the case of directly producing the toner particles through the polymerization process, monomers of these resins may be used.
  • Such monomers may include: styrene and its derivatives such as styrene, o-, m- or p-methylstyrene, and m- or p-ethylstyrene; (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, octyl (meth)acrylate, dodecyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and diethylaminoethyl (meth)acrylate; butadiene; isoprene; cyclohexane; (meth)acrylonitrile, and acrylamide.
  • These monomers may be used singly or in mixture of two or more species so as to provide a theoretical glass transition point (Tg), described in "POLYMER HANDBOOK", second addition, III-pp. 139 - 192 (available from John Wiley & Sons Co.), of 40 - 75 °C. If the theoretical glass transition point is below 40 °C, the resultant toner particles are liable to have lower storage stability and durability. On the other hand, if the theoretical glass transition point is in excess of 75 °C, the fixation temperature of the toner particles is increased, whereby respective color toner particles are liable to have an insufficient color-mixing characteristic particularly in the case of the full-color image formation.
  • Tg glass transition point
  • the theoretical glass transition point is below 40 °C, the resultant toner particles are liable to have lower storage stability and durability.
  • the fixation temperature of the toner particles is increased, whereby respective color toner particles are liable to have an insufficient color-mixing characteristic particularly in the case of the full-color image formation.
  • the molecular-weight distribution of THF-soluble content of the outer shell resin may be measured by gel permeation chromatography (GPC) as follows.
  • GPC gel permeation chromatography
  • the toner particles are subjected to extraction with toluene for 20 hours by means of a Soxhlet extractor in advance, followed by distilling-off of the solvent (toluene) to obtain an extract.
  • An organic solvent e.g., chloroform
  • a low-softening point substance is dissolved and an outer resin is not dissolved is added is added to the extract and sufficiently washed therewith to obtain a residue product.
  • the residue product is dissolved in tetrahydrofuran (THF) and subjected to filtration with a solvent-resistant membrane filter having a pore size of 0.3 ⁇ m to obtain a sample solution (THF solution).
  • THF solution tetrahydrofuran
  • the sample solution is injected in a GPC apparatus ("GPC-150C", available from Waters Co.) using columns of A-801, 802, 803, 804, 805, 806 and 807 (manufactured by Showa Denko K.K.) in combination.
  • GPC-150C available from Waters Co.
  • the identification of sample molecular weight and its molecular weight distribution is performed based on a calibration curve obtained by using monodisperse polystyrene standard samples.
  • the THF-soluble content of the outer shell resin may preferably have a number-average molecular weight (Mn) of 5,000-1,000,000 and a ratio of weight-average molecular weight (Mw) to Mn (Mw/Mn) of 2 - 100.
  • a polar resin In order to enclose the low-softening point compound in the outer resin (layer), it is particularly preferred to add a polar resin.
  • a polar resin may include styrene-(meth)acrylic acid copolymer, styrene-maleic acid copolymer, saturated polyester resin and epoxy resin.
  • the polar resin may particularly preferably have no unsaturated group capable of reacting with the outer resin or a vinyl monomer constituting the outer resin. This is because if the polar resin has an unsaturated group, the unsaturated group can cause crosslinking reaction with the vinyl monomer, thus resulting in an outer resin having a very high molecular weight, which is disadvantageous because of a poor color-mixing characteristic.
  • the toner particles having an outer shell structure can further be surface-coated by polymerization to have an outermost shell resin layer.
  • the outermost shell resin layer may preferably be designed to have a glass transition temperature which is higher than that of the outer shell resin layer therebelow and be crosslinked within an extent of not adversely affecting the fixability, in order to provide a further improved anti-blocking characteristic.
  • the method for providing such an outer shell resin layer is not particularly restricted but examples thereof may include the following:
  • the colorant used in the present invention may include a black colorant, yellow colorant, a magenta colorant and a cyan colorant.
  • non-magnetic black colorant may include: carbon black, and a colorant showing black by color-mixing of yellow/magenta/cyan colorants as shown below.
  • yellow colorant may include: condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methin compounds and arylamide compounds. Specific preferred examples thereof may include C.I. Pigment Yellow 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 109, 110, 111, 128, 129, 147, 168 and 180.
  • magenta colorant may include: condensed azo compounds, diketopyrrolpyrrole compounds, anthraquinone compounds, quinacridone compounds, basis dye lake compounds, naphthol compounds, benzimidazole compounds, thioindigo compounds an perylene compounds. Specific preferred examples thereof may include: C.I. Pigment Red 2, 3, 5, 6, 7, 23, 48:2, 48:3, 48:4, 57:1, 81:1, 144, 146, 166, 169, 177, 184, 185, 202, 206, 220, 221 and 254.
  • cyan colorant may include: copper phthalocyanine compounds and their derivatives, anthraquinone compounds and basis dye lake compounds. Specific preferred examples thereof may include: C.I. Pigment Blue 1, 7, 15, 15:1, 15:2, 15:3, 15:4, 60, 62, and 66.
  • colorants may be used singly, in mixture of two or more species or in a state of solid solution.
  • the above colorants may be appropriately selected in view of hue, color saturation, color value, weather resistance, transparency of the resultant OHP film, and a dispersibility in toner particles.
  • the above colorants may preferably be used in a proportion of 1 - 20 wt. parts per 100 wt. parts of the binder resin.
  • the charge control agent may be used in the present invention including known charge control agents.
  • the charge control agent may preferably be one which is colorless and has a higher charging speed and a property capable of stably retaining a prescribed charge amount.
  • the charge control agent may particularly preferably be one free from polymerization-inhibiting properties and not containing a component soluble in an aqueous medium.
  • the charge control agent may be those of negative-type or positive-type.
  • the negative charge control agent may include: metal compounds organic acids, such as salicylic acid, dialkylsalicylic acid, naphtoic acid, dicarboxylic acid and derivatives of these acids; polymeric compounds having a side chain comprising sulfonic acid or carboxylic acid; borate compound; urea compounds; silicon compound; and calixarene.
  • Specific examples of the positive charge control agent may include: quaternary ammonium salts; polymeric compounds having a side chain comprising quaternary ammonium salts; guanidine compounds; and imidazole compounds.
  • the charge control agent may preferably be used in a proportion of 0.5 - 10 wt. parts per 100 wt. parts of the binder resin.
  • the charge control agent is not an essential component for the toner particles used in the present invention.
  • Examples of the polymerization initiator usable in the direct polymerization may include: azo-type polymerization initiators, such as 2,2'-azobis-(2,4-dimethylvaleronitrile), 2,2'-azobisisobutylonitrile, 1,1'-azobis(cyclohexane-2-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile; and peroxide-type polymerization initiators such as benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, and lauroyl peroxide.
  • azo-type polymerization initiators such as 2,2'-azobis-(2,4-dimethylvaleronitrile), 2,2'-azobisisobutylonitrile, 1,1'-azobis(cyclohexan
  • the addition amount of the polymerization initiator varies depending on a polymerization degree to be attained.
  • the polymerization initiator may generally be used in the range of about 0.5 - 20 wt. % based on the weight of the polymerizable monomer.
  • the polymerization initiators somewhat vary depending on the polymerization process used and may be used singly or in mixture while making reference to 10-hour half-life period temperature.
  • an inorganic or/and an organic dispersion stabilizer in an aqueous dispersion medium.
  • the inorganic dispersion stabilizer may include: tricalcium phosphate, magnesium phosphate, aluminum phosphate, zinc phosphate, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate, bentonite, silica, and alumina.
  • organic dispersion stabilizer may include: polyvinyl alcohol, gelatin, methyl cellulose, methyl hydroxypropyl cellulose, ethyl cellulose, carboxymethyl cellulose sodium salt, polyacrylic acid and its salt and starch. These dispersion stabilizers may preferably be used in the aqueous dispersion medium in an amount of 0.2 - 10 wt. parts per 100 wt. parts of the polymerizable monomer mixture.
  • an inorganic dispersion stabilizer a commercially available product can be used as it is, but it is also possible to form the stabilizer in situ in the dispersion medium so as to obtain fine particles thereof.
  • tricalcium phosphate for example, it is adequate to blend an aqueous sodium phosphate solution and an aqueous calcium chloride solution under an intensive stirring to produce tricalcium phosphate particles in the aqueous medium, suitable for suspension polymerization.
  • Examples of the surfactant may include: sodium dodecylbenzenesulfonate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, sodium laurate, potassium stearate, and calcium oleate.
  • the toner particles according to the present invention may also be produced by direct polymerization in the following manner.
  • a polymerizable monomer a low-softening point substance (release agent), a colorant, a charge control agent, a polymerization initiator and another optional additive are added and uniformly dissolved or dispersed by a homogenizer or an ultrasonic dispersing device, to form a polymerizable monomer composition, which is then dispersed and formed into particles in a dispersion medium containing a dispersion stabilizer by means of a stirrer, homomixer or homogenizer preferably under such a condition that droplets of the polymerizable monomer composition can have a desired particle size of the resultant toner particles by controlling stirring speed and/or stirring time.
  • the stirring may be continued in such a degree as to retain the particles of the polymerizable monomer composition thus formed and prevent the sedimentation of the particles.
  • the polymerization may be performed at a temperature of at least 40 °C, generally 50 - 90 °C. The temperature can be raised at a latter stage of the polymerization. It is also possible to subject a part of the aqueous system to distillation in a latter stage of or after the polymerization in order to remove the yet-polymerized part of the polymerizable monomer and a by-product which can cause and odor in the toner fixation step. After the reaction, the produced toner particles are washed, filtered out, and dried. In the suspension polymerization, it is generally preferred to use 300-3000 wt. parts of water as the dispersion medium per 100 wt. parts of the monomer composition.
  • the toner particles can be further subjected to classification for controlling the particle size distribution.
  • classification for controlling the particle size distribution.
  • the developing method according to the present invention may for example be performed by using a developing device as shown in Figure 1. It is preferred to effect a development in a state where a magnetic brush formed of a developer contacts a latent image-bearing member, e.g., a photosensitive drum 3 under application of an alternating electric field.
  • a developer-carrying member (developing sleeve) 1 may preferably be disposed to provide a gap B of 100-1000 ⁇ m from the photosensitive drum 3 in order to prevent the carrier attachment and improve the dot reproducibility. If the gap is narrower than 100 ⁇ m, the supply of the developer is liable to be insufficient to result in a low image density. In excess of 1000 ⁇ m, the lines of magnetic force exerted by a developing pole S1 is spread to provide a low density of magnetic brush, thus being liable to result in an inferior dot reproducibility and a weak carrier constraint force leading to carrier attachment.
  • 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.
  • V forward a voltage component for producing toner transfer to the image-bearing member.
  • 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.
  • Vback fog-removing voltage
  • primary charge voltage a lower primary charge voltage on the photosensitive member, thereby increasing the life of the photosensitive member.
  • Vback may preferably be at most 200 volts, more preferably at most 180 volts.
  • a contrast potential of 200 - 500 volts so as to provide a sufficient image density.
  • the frequency can affect the process, and 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 between 3 - 8 mm, it becomes possible to satisfy a sufficient image density and a good dot reproducibility. If broader than 8 mm, the developer is apt to be packed to stop the movement of the apparatus, and 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 developing method according to the present invention may particularly suitably be adopted in a full-color image forming process wherein a halftone producibility is thought much of, while using the developer according to the present invention for developing digital latent images, whereby the dot latent images can be reproduced faithfully without adverse effect of the magnetic brush and without disordering electrostatic images.
  • the developer of the present invention it is possible to realize not only high image qualities at the initial stage but also prevention of image quality deterioration during a continuous image formation on a large number of sheets because of a suppressed shearing force applied to the developer in the developing device.
  • the developer-carrying member used in the present invention may preferably satisfy the following surface state conditions, as illustrated in Figure 3: 0.2 ⁇ m ⁇ center line-average roughness (Ra) ⁇ 5.0 ⁇ m, 10 ⁇ m ⁇ average unevenness spacing (Sm) ⁇ 80 ⁇ m and 0.05 ⁇ Ra/Sm ⁇ 0.5.
  • Ra and Sm refer to a center line-average roughness and an average unevenness spacing defined by JIS B0601 (and ISO 468) and obtained by the following formula:
  • the developer-carrying member shows an insufficient developer-conveying ability so that an image density irregularity is liable to be caused particularly in a continuous image formation. If Ra exceeds 5 ⁇ m, the developer-carrying member is excellent in toner-conveying ability but exerts too large a constraint force at a developer conveying regulation zone as by a regulating blade to cause deterioration by rubbing of an external additive to the toner particle surfaces, thus being liable to cause a lowering in image quality during a successive image formation.
  • Ra/Sm is below 0.05, the developer-carrying member shows too small a toner-retention force so that the retention of toner on the developer-carrying member becomes difficult and the conveyance to the developer regulation zone is not controlled, whereby an image density irregularity is liable to be caused. If Ra/Sm exceeds 0.5, the toner entering the concavities is not mixed circulatively with the other toner, so that the toner melt-sticking is liable to occur.
  • Ra and Sm described herein are based on those measured according to JIS-B0601 by using a contact-type surface roughness tester ("SE-3300", mfd. by Kosaka Kenkyusho K.K.) by using a measurement length 1 of 2.5 mm and effecting measurement at arbitrarily selected several points on the surface of a developer-carrying member.
  • SE-3300 contact-type surface roughness tester
  • a developer-carrying member may be provided with a prescribed surface roughness, e.g., by sand blasting with abrasive particles comprising irregularly shaped or regularly shaped particles, rubbing of the sleeve with sand paper in directions in parallel with the axis thereof (i.e., directions perpendicular to the developer-conveying direction) for providing unevenness preferentially formed in the circumferential direction, chemical treatment, and coating with a resin followed by formation of resinous projections.
  • a prescribed surface roughness e.g., by sand blasting with abrasive particles comprising irregularly shaped or regularly shaped particles, rubbing of the sleeve with sand paper in directions in parallel with the axis thereof (i.e., directions perpendicular to the developer-conveying direction) for providing unevenness preferentially formed in the circumferential direction, chemical treatment, and coating with a resin followed by formation of resinous projections.
  • the developer-carrying member used in the present invention may be composed of a known material, examples of which may include: metals, such as aluminum, stainless steel, and nickel; a metal body coated with carbon, a resin or an elastomer; and elastomer, such as natural rubber, silicone rubber, urethane rubber, neoprene rubber, butadiene rubber and chloroprene rubber in the form of an unfoamed, or foamed or sponge form, optionally further coated with carbon, a resin or an elastomer.
  • metals such as aluminum, stainless steel, and nickel
  • elastomer such as natural rubber, silicone rubber, urethane rubber, neoprene rubber, butadiene rubber and chloroprene rubber in the form of an unfoamed, or foamed or sponge form, optionally further coated with carbon, a resin or an elastomer.
  • the developer-carrying member used in the present invention may assume a shape of a cylinder or a sheet.
  • the color electrophotographic apparatus shown in Figure 4 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 4) 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 4).
  • 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 200 particles are taken at random from a sample carrier and photographed through a scanning electron microscope at a magnification of 100 - 5000.
  • Each enlarged photograph is placed on a tablet (available from Wacom Co.) connected to a computer, and the tablet is manipulated manually to measure the horizontal FERE diameter of each particle as a particle size, thereby obtaining a number-basis particle size distribution including a standard deviation ⁇ and a number-average particle size (Dn), from which the number-basis proportion of particles having sizes in the range of at most a half of the number-average particle size ( ⁇ 1/2Dn%) is calculated.
  • Magnetic carrier is placed in an external magnetic field of 1 kilo-oersted to measure its magnification.
  • the magnetic carrier powder sample is sufficiently tightly packed in a cylindrical plastic cell 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 weight to obtain a magnetization (emu/g).
  • the true density of the carrier particles is measured by a dry-type automatic density meter ("Accupic 1330", available from Simazu Seisakusho K.K.) and the magnetization (emu/g) is multiplied by the true density to obtain a magnetization per volume (emu/cm 3 ).
  • the resistivity of a carrier or a carrier core 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 density of exposure of metal oxide particles at the carrier surface of coated magnetic carrier particles is measured by using enlarged photographs at a magnification of 5,000 - 10,000 taken through a scanning electron microscope ("S-800", available from Hitachi Seisakusho K.K.) at an accelerating voltage of 1 kV.
  • S-800 scanning electron microscope
  • Each coated magnetic carrier particle is observed with respect to its front hemisphere to count the number of exposed metal oxide particles (i.e., the number of metal oxide particles protruding out of the surface) per unit area. Protrusions having a diameter of 0.01 ⁇ m or larger may be counted. This operation is repeated with respect to at least 300 coated metal oxide particles to obtain an average value of the number of exposed metal oxide particles per unit area.
  • a prescribed amount of a sample carrier is calcined at 500 °C for 2 hours to determine the calcination weight loss as a total resin content.
  • a similar prescribed amount of the sample carrier is soaked for dissolution within tetrahydrofuran (THF) for 2 hours and, after drying, the dissolution weight loss is determined as a non-crosslinked resin content.
  • a surfactant alkylbenzenesulfonic acid salt
  • 2 - 20 mg of a sample toner is added.
  • the sample suspended in the electrolyte liquid is subjected to a dispersion treatment for 1 - 3 min. and then to a particle size distribution measurement by a laser scanning particle size distribution analyzer ("CIS-100", available from GALAI Co.). Particle in the size range of 0.5 ⁇ m - 60 ⁇ m are measured to obtain a number-average particle size (D1) and a weight-average particle size (D4) by computer processing.
  • D1 number-average particle size
  • D4 weight-average particle size
  • the percentage by number of particles having sizes of at most a half of the number-average particle size is calculated.
  • the percentage by volume of particles having sizes of at least two times the weight-average particle size is calculated.
  • 0.2 g of a sample toner is dissolved in 4 ml of THF and the solution is subjected to gas chromatography under the following conditions to measure the monomer content according to the internal standard method.
  • the lipophilization for the magnetic and ⁇ -Fe 2 O 3 was performed by adding 1.0 wt. part of ⁇ -aminotrimethoxysilane to 99 wt. parts of magnetite or 99 wt. parts of ⁇ -Fe 2 O 3 , and each mixture was stirred at 100 °C for 30 min. in a Henschel mixer.
  • the dried precipitate was further dried at 180 °C at a reduced pressure of at most 5 mmHg, thereby to obtain spherical magnetic carrier core particles containing the magnetite and the hematite in a phenolic resin binder.
  • the particles were caused to pass through a 60 mesh-sieve and a 100 mesh-sieve to remove the coarse particle fraction, and then to removal of fine and coarse powder fraction by using a multi-division pneumatic classifier utilizing the Coanda effect ("Elbow Jet Labo EJ-L-3", available from Nittetsu Kogyo K.K.), thereby to recover carrier core particles having a number-average particle size (Dn) of 31 ⁇ m.
  • 100 wt. parts of the carrier core particles were surface-coated with a silicone resin composition comprising 0.5 wt. part of a straight silicone resin of which substituents were all methyl groups and 0.025 wt. part of ⁇ -aminopropyltrimethoxysilane in the following manner.
  • a silicone resin composition comprising 0.5 wt. part of a straight silicone resin of which substituents were all methyl groups and 0.025 wt. part of ⁇ -aminopropyltrimethoxysilane in the following manner.
  • the above silicone resin composition was dissolved at a concentration of 10 wt. % in toluene to form a carrier coating solution.
  • the coating solution was mixed with the carrier core particles while continuously applying a shearing force to vaporize the solvent, thereby effecting the coating.
  • Carrier No. 1 exhibited an average surface exposure density of metal oxide (denoted by MO-exposure rate) of 2.3 (particles)/ ⁇ m 2 .
  • Carrier No. 1 magnetic coated carrier
  • Carrier No. 2 By effecting a silicone resin coating similarly as in Example 1, Carrier No. 2 (magnetic coated carrier) was obtained.
  • Carrier No. 3 By effecting a silicone resin coating similarly as in Example 1, Carrier No. 3 (magnetic coated carrier) was obtained.
  • Phenol 7.5 wt.parts Formalin solution (Same as in Example 1) 11.25 " Magnetite (lipophilized, Same as in Example 1) 44 " ⁇ -Fe 2 O 3 44 " (lipophilized, Same as in Example 1)
  • the magnetic carrier core particles were subjected to a similar silicone resin coating as in Example 1 to prepare Carrier No. 4.
  • melt-kneaded product 100 wt. parts of polyester resin, 500 wt. parts of magnetite powder, 2 wt. parts of carbon black and 1.5 wt. part of silica were sufficiently blended and melt-kneaded in a pressurized kneader. After cooling, the melt-kneaded product was coarsely crushed by a feathermill and finely pulverized by a jet mill including a collision plate having a shape of truncated cone (an apex angle of the removed cone of 120 deg., providing a trapezoidal transverse section) under a pulverization air pressure of 2.5 kg.f/cm 2 , followed by classification by a multiplexer to obtain Carrier No.
  • Magnetic carrier core particles were prepared in the same manner as in Example 1 except for using the magnetite particles and ⁇ -Fe 2 O 3 particles without the lipophilization treatment and without classification by the multi-division classifier.
  • the carrier core particles were subjected to surface-coating with straight silicone resin composition similarly as in Example 1 to prepare Carrier No. 10 (magnetic coated carrier).
  • Carrier Nos. 1 - 10 The properties of Carrier Nos. 1 - 10 are inclusively shown in the following Table 1.
  • Pigment Blue 15:3 (colorant) 15 wt. parts
  • Dialkylsalicylic acid metal compound charge control agent 5 wt. parts
  • Saturated polyester 10 wt. parts
  • the polymerizable monomer composition was charged, and the system was stirred at 11,000 rpm (by TK-Homomixer) for 10 min. at 60 °C in an N 2 -environment to disperse the composition into a particulate form. (This step is hereinafter referred to a "particulation”.) Then, the system was stirred by a paddle stirrer and heated to 80 °C to effect polymerization for 10 hours. After the polymerization, the system was subjected to distilling-off of the residual monomer under a reduced pressure, cooling, addition of hydrochloric acid to dissolve the calcium phosphate, filtration, washing with water and drying to obtain cyan toner particles.
  • Cyan Toner A exhibited a weight average particle size (D4) of 6.0 ⁇ m, a number-average particle size (D1) of 4.7 ⁇ m, a percentage (cumulative) by number of particles having sizes of at most a half of D1 (hereinafter denoted by " ⁇ 1/2 ⁇ D1%") of 6.9 %N ("%N” represents a percent by number), and a percentage (cumulative) % volume of particles having sizes of at least two times D4 (hereinafter denoted by " ⁇ 2 ⁇ D4%") of 0 %V (“%V” represents % by volume), a shape factor SF-1 of 103, a residual monomer content (Mres) of 400 ppm.
  • the toner particles had a core/shell structure enclosing the ester was at the core.
  • the ester was enclosed within the toner particles to provide core/shell structure.
  • polyester resin 100 wt. parts of polyester resin, 5 wt. parts of C.I. Pigment Blue 15:3, 5 wt. parts of dialkylsalicylic acid metal compound, and 5 wt. parts of low-molecular weight polypropylene were added and blended within a Henschel mixer. The blend was then melt kneaded through a twin-screw extruder while connecting its vent port to a suction pump for sucking.
  • Toners A - G The properties of Toners A - G are shown in the following Table 2.
  • each developing device was designed to have a spacing A of 550 ⁇ 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 having a polytetrafluoroethylene-dispersed surface protective layer.
  • a developing nip C at that time was 5.5 mm.
  • the developing sleeve 1 and the photosensitive drum 3 were driven at a peripheral speed ratio of 2.0:1.
  • a developing pole 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 2200 Hz, a developing bias of -450 volts, a toner developing contrast (Vcont) of 330 volts (absolute value), a fog removal voltage (Vback) of 80 volts (absolute value), and a primary charge voltage on the photosensitive drum of -530 volts.
  • the developer sleeve was composed of a 25 mm-dia.
  • the resultant images exhibited high solid-part image densities of 1.51 for cyan, 1.56 for yellow, 1.53 for magenta and 1.52 for black and good halftone reproducibilities for the respective colors. Further, no image disorder due to carrier attachment or fog at non-image portion was observed.
  • Respective colors of two-component type developers were prepared in the same manner as in Example 7 except for using Carrier No. 2 instead of Carrier No. 1 and evaluated in the same manner as in Example 7.
  • the resultant images exhibited high solid-part image densities of 1.47 for cyan, 1.49 for yellow, 1.47 for magenta and 1.47 for black and good halftone reproducibilities for the respective colors. Further, no image disorder due to carrier attachment or fog at non-image portion was observed.
  • the resultant images showed solid-part image densities of 1.50, 1.49, 1.52 and 1.48 for cyan, yellow, magenta and black, respectively, which were high similarly as in the initial stage and good halftone reproducibility. No carrier attachment was observed either.
  • the carrier particles therein exhibited a surface state which was substantially identical to that in the initial stage. Further, no liberation of metal oxide particles dispersed in the carrier was observed either.
  • the cyan developer exhibited triboelectric chargeabilities in environments of low temperature/low humidity (L/L), normal temperature/normal humidity (N/N), and high temperature/high humidity (H/H) of -30.3 ⁇ C/g, -28.8 ⁇ C/g and -27.4 ⁇ C/g, respectively, indicating a good environmental stability.
  • Respective colors of two-component type developers were prepared in the same manner as in Example 7 except for using Carrier No. 3 (magnetic coated carrier, comparative) instead of Carrier No. 1 and evaluated in the same manner as in Example 7.
  • the resultant images exhibited high solid-part image densities of 1.45 for cyan, 1.44 for yellow, 1.45 for magenta and 1.46 for black but somewhat inferior halftone reproducibilities for the respective colors. Further, carrier attachment was observed and slight fog occurred at non-image portion.
  • the resultant images showed solid-part image densities of 1.50, 1.48, 1.47 and 1.47 for cyan, yellow, magenta and black, respectively, which were similar to those in the initial stage but exhibited inferior halftone reproducibility and carrier attachment similarly as in the initial stage.
  • the cyan developer exhibited triboelectric chargeabilities in environments of low temperature/low humidity (L/L), normal temperature/normal humidity (N/N), and high temperature/high humidity (H/H) of -31.6 ⁇ C/g, -30.3 ⁇ C/g and -27.7 ⁇ C/g, respectively.
  • Respective colors of two-component type developers were prepared in a similar manner as in Example 7 except for using Carrier No. 4 instead of Carrier No. 1 and evaluated in the same manner as in Example 7.
  • the resultant images exhibited high solid-part image densities of 1.48 for cyan, 1.51 for yellow, 1.48 for magenta and 1.52 for black and good halftone reproducibilities for the respective colors. Further, no image disorder due to carrier attachment or fog at non-image portion was observed.
  • the resultant images showed solid-part image densities of 1.50, 1.53, 1.47 and 1.49 for cyan, yellow, magenta and black, respectively, which were high similarly as in the initial stage and good halftone reproducibility. No carrier attachment was observed either.
  • the carrier particles therein exhibited a surface state which was substantially identical to that in the initial stage. Further, no liberation of metal oxide particles dispersed in the carrier was observed either.
  • the cyan developer exhibited triboelectric chargeabilities in environments of low temperature/low humidity (L/L), normal temperature/normal humidity (N/N), and high temperature/high humidity (H/H) of -31.6 ⁇ C/g, -29.6 ⁇ C/g and -27.5 ⁇ C/g, respectively, indicating a somewhat larger environment-dependence, which was however of a practically non-problematic level.
  • L/L low temperature/low humidity
  • N/N normal temperature/normal humidity
  • H/H high temperature/high humidity
  • Respective colors of two-component type developers were prepared in a similar manner as in Example 7 except for using Carrier No. 5 instead of Carrier No. 1 and evaluated in the same manner as in Example 7.
  • the resultant images exhibited high solid-part image densities of 1.53 for cyan, 1.55 for yellow, 1.53 for magenta and 1.56 for black and very good halftone reproducibilities for the respective colors. Further, no carrier attachment or fog was observed.
  • the resultant images showed solid-part image densities of 1.52, 1.54, 1.53 and 1.52 for cyan, yellow, magenta and black, respectively, which were high similarly as in the initial stage and good halftone reproducibility. No carrier attachment or fog was observed either.
  • the carrier particles therein exhibited a surface state which was substantially identical to that in the initial stage. Further, no liberation of metal oxide particles dispersed in the carrier was observed either.
  • the cyan developer exhibited triboelectric chargeabilities in environments of low temperature/low humidity (L/L), normal temperature/normal humidity (N/N), and high temperature/high humidity (H/H) of -28.8 ⁇ C/g, -27.8 ⁇ C/g and -26.0 ⁇ C/g, respectively, indicating a good environmental stability similarly as in Example 7.
  • Respective colors of two-component type developers were prepared in a similar manner as in Example 7 except for using Carrier No. 6 instead of Carrier No. 1 and evaluated in the same manner as in Example 7.
  • the resultant images exhibited high solid-part image densities of 1.54 for cyan, 1.47 for yellow, 1.44 for magenta and 1.46 for black, and good halftone reproducibilities for the respective colors while they were somewhat inferior than those in Example 7. Further, no carrier attachment or fog was observed.
  • the resultant images showed solid-part image densities of 1.45, 1.48, 1.46 and 1.49 for cyan, yellow, magenta and black, respectively, which were high similarly as in the initial stage and good halftone reproducibility. No carrier attachment or fog was observed either.
  • the carrier particles therein exhibited a surface state which was substantially identical to that in the initial stage. Further, no liberation of metal oxide particles dispersed in the carrier was observed either.
  • the cyan developer exhibited triboelectric chargeabilities in environments of low temperature/low humidity (L/L), normal temperature/normal humidity (N/N), and high temperature/high humidity (H/H) of -32.5 ⁇ C/g, -31.3 ⁇ C/g and -29.9 ⁇ C/g, respectively, indicating a good environmental stability similarly as in Example 7.
  • Respective colors of two-component type developers were prepared in the same manner as in Example 7 except for using Carrier No. 7 instead of Carrier No. 1 and evaluated in the same manner as in Example 7.
  • the resultant images exhibited high solid-part image densities of 1.49 for cyan, 1.52 for yellow, 1.47 for magenta and 1.47 for black and good halftone reproducibilities for the respective colors similarly as in Example 7. Further, no carrier attachment or fog was observed.
  • the resultant images showed solid-part image densities of 1.50, 1.51, 1.49 and 1.50 for cyan, yellow, magenta and black, respectively, which were high similarly as in the initial stage and good halftone reproducibility. No carrier attachment or fog was observed either.
  • the carrier particles therein exhibited a surface state which was substantially identical to that in the initial stage. Further, no liberation of metal oxide particles dispersed in the carrier was observed either.
  • the cyan developer exhibited triboelectric chargeabilities in environments of low temperature/low humidity (L/L), normal temperature/normal humidity (N/N), and high temperature/high humidity (H/H) of -30.5 ⁇ C/g, -28.9 ⁇ C/g and -27.0 ⁇ C/g, respectively, indicating a good environmental stability.
  • Respective colors of two-component type developers were prepared in the same manner as in Example 7 except for using Carrier No. 8 (comparative) instead of Carrier No. 1 and evaluated in the same manner as in Example 7.
  • the resultant images exhibited high solid-part image densities of 1.44 for cyan, 1.46 for yellow, 1.45 for magenta and 1.46 for black but somewhat inferior halftone reproducibilities (accompanied with dot disorder) for the respective colors. Further, carrier attachment and fog were observed.
  • the resultant images showed solid-part image densities of 1.50, 1.51, 1.49 and 1.51 for cyan, yellow, magenta and black, respectively, which were liable to be higher than the initial stage values.
  • the halftone reproducibility and carrier attachment were inferior similarly as in the initial stage.
  • the cyan developer exhibited triboelectric chargeabilities in environments of low temperature/low humidity (L/L), normal temperature/normal humidity (N/N), and high temperature/high humidity (H/H) of -35.2 ⁇ C/g, -31.7 ⁇ C/g and -27.7 ⁇ C/g, respectively, indicating a large environmental dependence.
  • L/L low temperature/low humidity
  • N/N normal temperature/normal humidity
  • H/H high temperature/high humidity
  • Respective colors of two-component type developers were prepared in the same manner as in Example 7 except for using Carrier No. 9 (comparative) instead of Carrier No. 1 and evaluated in the same manner as in Example 7.
  • the resultant images exhibited high solid-part image densities of 1.45 for cyan, 1.46 for yellow, 1.44 for magenta and 1.45 for black but somewhat inferior halftone reproducibilities (accompanied with dot disorder) for the respective colors. Further, some carrier attachment and fog occurred.
  • the resultant images showed solid-part image densities of 1.49, 1.49, 1.47 and 1.48 for cyan, yellow, magenta and black, respectively, which were liable to be higher than in the initial. No carrier attachment was observed, but the halftone reproducibility and fog became even worse than in the initial stage. Further, the cyan developer exhibited triboelectric chargeabilities in environments of low temperature/low humidity (L/L), normal temperature/normal humidity (N/N), and high temperature/high humidity (H/H) of -33.6 ⁇ C/g, -31.5 ⁇ C/g and -27.2 ⁇ C/g, respectively, indicating a large environmental dependence.
  • L/L low temperature/low humidity
  • N/N normal temperature/normal humidity
  • H/H high temperature/high humidity
  • a two-component type cyan developer was prepared in the same manner as in Example 7 except for using Cyan Toner B instead of Cyan Toner A.
  • the cyan developer thus prepared was charged in the same remodeled full-color laser copier and evaluated according to a single color-mode image forming test otherwise in the same manner as in Example 7.
  • the resultant images showed a high solid part image density of 1.49 and a particularly excellent halftone reproducibility. No carrier attachment or fog was observed either.
  • a two-component type cyan developer was prepared and evaluated in the same manner as in Example 13 except for using Cyan Toner C instead of Cyan Toner B.
  • a two-component type cyan developer was prepared and evaluated in the same manner as in Example 13 except for using Cyan Toner D instead of Cyan Toner B.
  • Respective colors of two-component type developers were prepared in the same manner as in Example 7 except for using Carrier No. 10 instead of Carrier No. 1 and evaluated in the same manner as in Example 7.
  • the image density of a solid image portion of an image formed on plain paper was measured as a relative density by using a reflective densitometer equipped with an SPI filter ("Macbeth Color Checker RD-1255", available from Macbeth Co.).
  • the roughness of a halftone image portion on a reproduced image was evaluated by comparing it with an original halftone image and several levels of reference reproduced images by eye observation.
  • a solid white image reproduction was interrupted, and a transparent adhesive tape was intimately applied onto a region on the photosensitive drum between the developing station and cleaning station to sample magnetic carrier particles attached to the region. Then, the number of magnetic carrier particles attached onto a size of 5 cm x 5 cm were counted to determine the number of attached carrier particles per cm 2 .
  • the results were evaluated according to the following standard:

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Developing Agents For Electrophotography (AREA)
EP97302356A 1996-04-08 1997-04-07 Magnetic coated carrier, two-component type developer and developing method Expired - Lifetime EP0801335B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP8524096 1996-04-08
JP85240/96 1996-04-08
JP8524096 1996-04-08

Publications (2)

Publication Number Publication Date
EP0801335A1 EP0801335A1 (en) 1997-10-15
EP0801335B1 true EP0801335B1 (en) 2001-08-29

Family

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EP97302356A Expired - Lifetime EP0801335B1 (en) 1996-04-08 1997-04-07 Magnetic coated carrier, two-component type developer and developing method

Country Status (5)

Country Link
EP (1) EP0801335B1 (ko)
KR (1) KR100227586B1 (ko)
CN (1) CN1111761C (ko)
DE (1) DE69706353T2 (ko)
HK (1) HK1002876A1 (ko)

Families Citing this family (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0884653B1 (en) * 1997-06-13 2003-05-02 Canon Kabushiki Kaisha Image forming method, image forming apparatus and process cartridge
JP3305236B2 (ja) * 1997-07-04 2002-07-22 戸田工業株式会社 電子写真用磁性キャリア及びその製造法
DE69823154T2 (de) * 1998-01-08 2004-08-26 Powdertech Co. Ltd., Kashiwa Regeneration von Trägerteilchen
JP3927693B2 (ja) * 1998-07-22 2007-06-13 キヤノン株式会社 磁性微粒子分散型樹脂キャリア，二成分系現像剤及び画像形成方法
DE69928062T2 (de) 1998-11-06 2006-07-20 Toda Kogyo Corp. Elektrophotographischer magnetischer Träger
US6312862B1 (en) 1998-11-06 2001-11-06 Canon Kabushiki Kaisha Two-component type developer and image forming method
JP4323684B2 (ja) * 1999-06-30 2009-09-02 キヤノン株式会社 磁性体分散型樹脂キャリアの製造方法
JP3794264B2 (ja) * 2000-12-12 2006-07-05 富士ゼロックス株式会社 電子写真用現像剤および画像形成方法
KR100583437B1 (ko) 2003-10-13 2006-05-26 삼성전자주식회사 전자사진방식 레이저 프린터
JP5517471B2 (ja) * 2008-03-11 2014-06-11 キヤノン株式会社 二成分系現像剤
WO2009125856A1 (ja) * 2008-04-10 2009-10-15 キヤノン株式会社 画像形成装置
KR101548158B1 (ko) 2012-09-07 2015-08-28 제일모직 주식회사 성형품 및 성형품의 제조 방법
KR101515430B1 (ko) 2012-10-24 2015-04-27 제일모직 주식회사 라미네이트 시트, 라미네이트 시트의 제조 방법, 상기 라미네이트 시트를 이용한 성형품 및 성형품의 제조 방법
JP6061673B2 (ja) * 2012-12-28 2017-01-18 キヤノン株式会社 トナー
KR20140087802A (ko) 2012-12-31 2014-07-09 제일모직주식회사 복합재 및 상기 복합재의 제조 방법
KR101665484B1 (ko) 2013-02-21 2016-10-12 롯데첨단소재(주) 수지 조성물 및 이를 이용한 성형품
CN104122751A (zh) * 2013-04-28 2014-10-29 北京京东方光电科技有限公司 绿色光阻组合物、其制备方法、彩色滤光片和显示器件
CN104122750A (zh) * 2013-04-28 2014-10-29 北京京东方光电科技有限公司 红色光阻组合物、其制备方法、彩色滤光片和显示器件

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JPS5793355A (en) * 1980-12-01 1982-06-10 Canon Inc Coated carrier composition for electrophotography
JP3499881B2 (ja) * 1992-02-28 2004-02-23 戸田工業株式会社 無機物粒子含有樹脂複合球状物粉体
EP0650099B1 (en) * 1993-10-15 2000-08-23 Canon Kabushiki Kaisha Carrier for electrophotography, two-component type developer, and image forming method
JP3397483B2 (ja) * 1993-12-29 2003-04-14 キヤノン株式会社 電子写真用キャリア，その製造方法，二成分系現像剤及び画像形成方法
CA2151988C (en) * 1994-06-22 2001-12-18 Kenji Okado Carrier for electrophotography, two component-type developer and image forming method
EP0704767A1 (en) * 1994-08-31 1996-04-03 Mita Industrial Co., Ltd. A two-component type developer
DE69511209T2 (de) * 1994-10-05 1999-11-25 Toda Kogyo Corp Magnetischer Träger für Elektrophotographie

Also Published As

Publication number Publication date
HK1002876A1 (en) 1998-09-25
KR970071156A (ko) 1997-11-07
DE69706353D1 (de) 2001-10-04
EP0801335A1 (en) 1997-10-15
CN1111761C (zh) 2003-06-18
DE69706353T2 (de) 2002-05-29
KR100227586B1 (ko) 1999-11-01
CN1168490A (zh) 1997-12-24

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