G03G9/107

Core material of magnetic carrier for electrophotographic developer and process for producing the same, magnetic carrier for electrophotographic developer, and two-component system developer
09778586 · 2017-10-03 · ·

The present invention provides a magnetic carrier for an electrophotographic developer which has an excellent durability and a stable charging property and is free from occurrence of spent toner thereonto, and a two-component system developer comprising the magnetic carrier for an electrophotographic developer and a toner. The present invention relates to a core material of a magnetic carrier for an electrophotographic developer comprising spherical composite particles comprising at least ferromagnetic iron oxide fine particles and a cured phenol resin and having an average particle diameter of 1 to 100 μm, a resin index of the spherical composite particles being within the range of 35 to 80%, and a magnetic carrier obtained by coating a surface of respective particles of the magnetic carrier core material with a resin.

Magnetic carrier

Provided is a magnetic carrier, including: a ferrite core particle; and a coating resin, in which: the coating resin has a surface resin layer and a resin composition in the stated order from a surface side thereof; the resin composition contains a resin, and an inorganic particle or carbon black that is subjected to a hydrophilic treatment; the surface resin layer contains a resin, is free of the inorganic particle or the carbon black, and has a thickness of from 0.01 μm or more to 4.00 μm or less; and a moisture percentage change between a moisture percentage when the magnetic carrier is left to stand under an environment of 30° C. and 80% RH for 24 hours, and a moisture percentage when the magnetic carrier is left to stand under an environment of 23° C. and 5% RH for 24 hours after the standing is 0.030 mass % or less.

Ferrite particles, carrier for electrophotographic development using same, and developer for electrophotography

Ferrite particles have, as a main component, a material represented by a composition formula M.sub.xFe.sub.3−xO.sub.4 (where M is at least one type of metal selected from a group made of Mg, Mn, Ca, Ti, Cu, Zn, Sr and Ni, 0<x<1), where the maximum height Rz of the particles falls within a range of 1.40 μm to 1.90 μm, and the degree of distortion Rsk of the particles falls within a range of −0.25 to −0.07. In this way, when the ferrite particles are used as the carrier of an electrophotographic image forming apparatus, even if an image formation speed is increased, the occurrence of a failure is reduced for a long period of time.

ELECTROSTATIC CHARGE IMAGE DEVELOPING CARRIER, ELECTROSTATIC CHARGE IMAGE DEVELOPER, PROCESS CARTRIDGE, IMAGE FORMING APPARATUS AND IMAGE FORMING METHOD

An electrostatic charge image developing carrier includes a magnetic particle and a coating resin layer that covers the magnetic particle and contains an inorganic particle, and the following relation 1 is satisfied: 0<(C−A)/(B−A)≤0.40 (relation 1), in which A is a Net intensity of Si determined by an X-ray fluorescence analysis of a carrier A that is a carrier taken out from a developer A obtained by mixing a carrier and a toner with a silica particle externally added, B is a Net intensity of Si determined by the X-ray fluorescence analysis of a carrier B that is a carrier taken out from a developer B obtained by adding a silica particle to the developer A to obtain a mixture and stirring the mixture with a Turbula stirring apparatus for 20 minutes, and C is a Net intensity of Si determined by the X-ray fluorescence analysis of a carrier C that is a carrier taken out from a mixture C obtained by stirring a toner particle and the carrier B being the carrier taken out from the developer B for 2 minutes with the Turbula stirring apparatus.

ELECTROSTATIC CHARGE IMAGE DEVELOPING CARRIER, ELECTROSTATIC CHARGE IMAGE DEVELOPER, PROCESS CARTRIDGE, IMAGE FORMING APPARATUS AND IMAGE FORMING METHOD

An electrostatic charge image developing carrier includes a magnetic particle and a coating resin layer that covers the magnetic particle and contains a silica particle, and a ratio of Si on a surface of the coating resin layer, determined by an X-ray photoelectron spectroscopy (XPS), is 6 atom % or more and 12 atom % or less.

ELECTROSTATIC CHARGE IMAGE DEVELOPING CARRIER, ELECTROSTATIC CHARGE IMAGE DEVELOPER, PROCESS CARTRIDGE, IMAGE FORMING APPARATUS AND IMAGE FORMING METHOD

An electrostatic charge image developing carrier, contains: a magnetic particle; and a coating resin layer coating the magnetic particle and containing inorganic particles, in which an area ratio of the inorganic particles that is a ratio of a total area of the inorganic particles to an area of the coating resin layer in a cut surface of the coating resin layer along a thickness direction of the coating resin layer is 10% or more and 50% or less.

ELECTROSTATIC CHARGE IMAGE DEVELOPING CARRIER, ELECTROSTATIC CHARGE IMAGE DEVELOPER, PROCESS CARTRIDGE, IMAGE FORMING APPARATUS AND IMAGE FORMING METHOD

An electrostatic charge image developing carrier, contains: a magnetic particle; and a coating resin layer coating the magnetic particle and containing inorganic particles, in which an area ratio of the inorganic particles that is a ratio of a total area of the inorganic particles to an area of the coating resin layer in a cut surface of the coating resin layer along a thickness direction of the coating resin layer is 10% or more and 50% or less.

Electrostatic charge image developing carrier, electrostatic charge image developer, developer cartridge, process cartridge, and image forming apparatus

An electrostatic charge image developing carrier includes a magnetic core particle, and a coating layer that coats surfaces of the magnetic core particle, wherein the coating layer includes a binder resin, thermosetting resin particles, and crosslinked resin particles, and the crosslinked resin particle contains a polymer formed by polymerizing a monomer component including the same monomer as a monomer used in the polymerization of the binder resin.

METHOD FOR PRODUCING CARRIER FOR ELECTROSTATIC CHARGE IMAGE DEVELOPMENT, METHOD FOR PRODUCING ELECTROSTATIC CHARGE IMAGE DEVELOPER, IMAGE FORMING METHOD, AND CARRIER FOR ELECTROSTATIC CHARGE IMAGE DEVELOPMENT

A method for producing a carrier for electrostatic charge image development includes coating magnetic particles by adding the magnetic particles and a coating liquid containing a resin and a solvent to a mixer with a stirring blade to form a resin coating layer on surfaces of the magnetic particles and taking a carrier having the resin coating layer out of the mixer. In the coating, the stirring conditions after the solvent is evaporated and dried by heating in the mixer until the carrier is taken out of the mixer satisfy Formula 1 below and Formula 2 below:


0.2≤peripheral speed πDn (m/s) of stirring blade≤2.0   Formula 1,


1×10.sup.3≤stirring workload (peripheral speed×stirring time T)≤4×10.sup.3   Formula 2, where D represents a diameter (m) of the stirring blade, n represents a number of revolutions (rps) of the stirring blade, and T represents a time (s) from a time point at which, after a load power of the stirring blade before drying of the solvent increases with drying until completion of drying, a load power of the stirring blade decreases to 1.3 times or less the load power of the stirring blade before drying to a time point at which stirring in the mixer is stopped.

METHOD FOR PRODUCING RECYCLED CARRIER, METHOD FOR PRODUCING RECYCLED ELECTROSTATIC CHARGE IMAGE DEVELOPER, IMAGE FORMING METHOD, AND RECYCLED CARRIER

A method for producing a recycled carrier includes: performing classification, the classification including separating a carrier having a coating layer from a collected developer by a centrifugal air classifier, the collected developer containing the carrier and being obtained by collecting an electrostatic charge image developer remaining after image formation; and performing recoating, the recoating including dissolving or thermally melting a coating resin of the separated and classified carrier and then coating the resulting carrier again to produce a recycled carrier.