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US 4,137,188 AGranted
Magnetic toner for electrophotography
OwnerShigeru Uetake, Katsutoshi Tozawa +1inventors
InventorsShigeru Uetake, Katsutoshi Tozawa, Keiji Sato
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OwnerShigeru Uetake, Katsutoshi Tozawa +1inventors
InventorsShigeru Uetake, Katsutoshi Tozawa, Keiji Sato
Estimating the term…
An insulating magnetic toner useful as a one component developer for electro-photography consisting essentially of a ferro-magnetic material, a resin and a charge controlling agent. The preferred toner mixture has an average particle size in the range from about 7 to about 30 .mu.m and is substantially free of particles having a size smaller than 1 .mu.m. The toner is preferably prepared by mixing a ferromagnetic material, a resin and a charge controlling agent, heat kneading, cooling and then granulating the mixture to form fine particles, contacting the pacticles with a hot gas of a temperature higher than the toner softening point and lower than 500.degree. C to fuse particles smaller than about 1 .mu.m to larger particles, cooling and selecting the particles of an average particle size of about 7 to about 30 .mu.m.
A process of making an insulating magnetic toner, useful as a one component developer for electrophotography comprising the steps of mixing ferromagnetic particles, a thermoplastic resin and a charge controlling agent, heat kneading, cooling and granulating the resulting mixture into fine particles, contacting the fine particles with a hot gas of a temperature higher than the toner softening point and lower than 500.degree. C. for a length of time sufficient so that particles smaller than about 1 .mu.m in size fuse to larger particles thereby reducing the content in percent by weight of the toner particles smaller than about 1 .mu.m in size to a range between 0.10 and 0.00, cooling the particles and then selecting the particles having an average particle size in the range of about 7 to about 30 .mu.m.
An insulating magnetic toner useful as a one component developer for electrophotography prepared by a process comprising the steps of mixing ferromagnetic particles, a thermoplastic resin and a charge controlling agent, heat kneading, cooling and granulating the resulting mixture into fine particles, contacting the fine particles with a hot gas of a temperature higher than the toner softening point and lower than 500.degree. C. for a length of time sufficient so that particles smaller than about 1 .mu.m in size fuse to larger particles thereby reducing the content in percent by weight of the toner particles smaller than about 1 .mu.m in size to a range between 0.10 and 0.00 cooling the particles and selecting the particles having an average particle size in the range of about 7 to about 30 .mu.m.
Dependencies are inferred from the claim text.