Magnetic carrier for electrophotographic developing agent and method of producing the same
AssigneeMita Industrial Co., Ltd.
InventorsHideaki Kawata, Tomohide Iida, Yoshiteru Hatase, Hidekazu Tamura, Nobuaki Kawano
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Abstract
A magnetic carrier for electrophotographic developing agent wherein the surfaces of the magnetic core particles are partly coated with a thermosetting resin and a small amount of a low-melting or low-softening thermoplastic resin or wax, and at least recessed portions of the core particles are filled with these coating materials. The magnetic carrier has an electric resistance that is maintained within a range that is suited for forming the image, and suppresses the occurrence of spent toner.
Claims20
A magnetic carrier for an electrophotographic developing agent comprising magnetic core particles and a resin-coated layer provided on the surfaces of the core particles, wherein the resin-coated layer comprises a thermosetting resin and a thermoplastic resin or wax, said thermoplastic resin or wax having a melting point or softening point lower than the thermosetting temperature of the thermosetting resin, and said resin-coated layer comprises the thermosetting resin and the thermoplastic resin or wax at a weight ratio of from 99.5:0.5 to 51:49, the resin-coated layer filling the recessed portions of the core particles and forming a partial coating layer having a coating area ratio of from 0.1 to 60%, wherein the resin-coated layer is in an amount of from 0.01 to 2.0% by weight based on the weight of the magnetic core particles.
A magnetic carrier for an electrophotographic developing agent comprising magnetic core particles and a resin-coated layer provided on the surfaces of the core particles, wherein the resin-coated layer comprises a thermosetting resin and a thermoplastic resin or wax, said thermoplastic resin or wax having a melting point or softening point lower than the thermosetting temperature of the thermosetting resin, and said resin-coated layer comprises the thermosetting resin and the thermoplastic resin or wax at a weight ratio of from 99.1 to 90:10, the resin coated layer filling the recessed portions of he core particles and forming a partial coating layer having a coating area ratio of from 1.0 to 50%, wherein the resin-coated layer is in an amount of from 0.05 to 1.5% by weight based on the weight of the magnetic core particles.
A method of producing a magnetic carrier for an electrophotographic developing agent containing magnetic core particles and a resin-coated layer on the surface of the core particles which comprises applying to the magnetic core particles a solution or a dispersion of a resin composition comprising a thermosetting resin and a thermoplastic resin or wax, said thermoplastic resin or wax having a melting point or softening point lower than the thermosetting temperature of the thermosetting resin, and said resin-coated layer comprises the thermosetting resin and the thermoplastic resin or wax at a weight ratio of from 99:1 to 90:10, and heating the resin composition on the surfaces of the magnetic core particles at a temperature which is not lower than the melting point of the thermoplastic resin and is not lower than the thermosetting temperature of the thermosetting resin, filling the recessed portions of the magnetic core particles and forming a partial coating layer on the surfaces of the magnetic core particles having a coating area ratio of from 1 to 50%, wherein the resin-coated layer is in an amount of from 0.01 to 2.0% by weight based on the weight of the magnetic core particles.
Dependencies are inferred from the claim text.