Abstract: A magnetic toner which is excellent in the low temperature fixability and the anti-offset properties is disclosed. The binder resin of the toner comprises a non-crosslinked styrene polymer, a non-crosslinked styrene copolymer or a mixture of these, and a polyolefin, wherein;the binder resin has, in its molecular weight distribution pattern measured by gel permeation chromatography (GPC), at least one maximal point (peak) in each region of a low molecular weight of from 5,000 to 20,000 and of a high molecular weight of from 200,00 to 1,000,000, where a height H1 of a maximum peak in the low molecular weight region, a height H3 of a maximum peak in the high molecular weight region and a height H2 of a minimal point between both of said peaks satisfy the relationship H1:H2:H3 of 3-25:1:1.5-12; and has a weight average molecular weight Mw and a number average molecular weight Mn in a value Mw/Mn of from 15 to 80.

Abstract: A magnetic toner is constituted by at least a binder resin and a magnetic iron oxide. The magnetic iron oxide is characterized by having an Fe(II) content of 18.5-24.1 wt. %, and shows a BET specific surface area of S (m.sup.2 /g) and an X-ray diffraction pattern giving a half-value width W (deg.) of a diffraction peak corresponding to 311 plane of the magnetic iron oxide in spinel structure, the values S and W satisfying: 4.5.times.10.sup.-3 S+0.130.ltoreq.W.ltoreq.4.5.times.10.sup.-3 S+0.160, and 4.5.ltoreq.S.ltoreq.11.0. Alternatively, the magnetic iron oxide is characterized by having a number-average particle size D satisfying a relationship with W of: -0.08D+0.180.ltoreq.W.ltoreq.-0.08D+0.212, and 0.10.ltoreq.D.ltoreq.0.45. The relationship between W and S or D indicates a good crystallinity of the magnetic iron oxide which provides the magnetic toner with a stable performance for a long period of time. The magnetic iron oxide can be obtained through a heating treatment at a temperature of 130.degree.

Abstract: A positively chargeable magnetic toner comprises positively chargeable magnetic toner particles having at least a binder resin, a magnetic substance and a charge controlling agent; wherein the binder resin contains (A) a vinyl polymer having carboxyl groups, acid anhydride groups, partial esters thereof or mixtures of the groups and having and an acid value of 5 to 30, and (B) a copolymer obtained by polymerizing at least a diolefin monomer and a vinyl monomer; and wherein the charge controlling agent contains (C) a quaternary ammonium salt and (D) a nigrosine dye or a triphenylmethane dye, the ratio by weight among the components (A), (B), (C) and (D) being within the range of (A):(B):(C):(D)=80 to 30:70 to 20:2.0 to 0.5: 2.0 to 0.1 relative to 100 parts of the total weight of the components (A) and (B). The present invention also provides an image forming process, an image forming apparatus and a facsimile apparatus, all of which use the positively chargeable magnetic toner.

Abstract: An image forming apparatus is formed by providing a latent image-bearing member for holding an electrostatic image thereon and a toner-carrying member for carrying a prescribed magnetic toner comprising a binder resin and magnetic powder and having a particle size distribution including 12% by number or more of magnetic toner particles of 5 microns or smaller, 33% by number or less of magnetic toner particles of 8-12.7 microns and 2% by volume or less of magnetic toner particles of 16 microns or larger so as to provide a volume-average particle size of 4-10 microns. At the developing station, an alternating bias voltage comprising a DC voltage and an unsymmetrical AC voltage in superposition is applied between the toner-carrying member and the latent image-bearing member to provide an alternating bias electric field comprising a development-side voltage component and a reverse-development side voltage component.

Abstract: An image forming apparatus is formed by providing a latent image-bearing member for holding an electrostatic image thereon and a toner-carrying member for carrying a prescribed magnetic toner comprising a binder resin and magnetic powder and having a particle size distribution including 12% by number or more of magnetic toner particles of 5 microns or smaller, 33% by number or less of magnetic toner particles of 8-12.7 microns and 2% by volume or less of magnetic toner parcitles of 16 microns or larger so as to provide a volume-average particle size of 4-10 microns. At the developing station, an alternating bias voltage comprising a DC voltage and an unsymmetrical AC voltage in superposition is applied between the toner-carrying member and the latent image-bearing member to provide an alternating bias electric field comprising a development-side voltage component and a reverse-development side voltage component.

Abstract: A process for producing a toner comprising:heating a monomer composition containing at least a polymerizable monomer and a release agent to a temperature not lower than the melting point or the softening point of said release agent todissolve the release agent in the polymerizable monomer and therebypreparing a monomer composition in which the release agent is dissolved;cooling the monomer composition to a temperature lower than the melting point or the softening point of the release agent to precipitate said release agent and therebypreparing a monomer composition containing the precipitated releasing agent particles having a number average size of 0.5 to 5 .mu.m;granulating in an aqueous dispersion medium the monomer composition to prepare a particle;carrying out suspension polymerization of the particle of the monomer composition at a temperature lower than the melting point or the softening point of the release agent.

Abstract: A toner for developing electrostatic latent images is produced by a process comprising the steps of: (a) stirring at least water, hardly water-soluble inorganic fine powder and a specific compound thereby to prepare an aqueous dispersion medium; (b) adding a polymerizable monomer composition comprising at least a polymerizable monomer and a polymerization initiator to the aqueous dispersion medium; (c) forming particles of the polymerizable monomer composition in the aquoeus dispersion medium; (d) subjecting the particles of the polymerizable monomer composition to suspension polymerization, thereby to produce toner particles; and (e) removing the hardly water-soluble inorganic fine powder attached to the surfaces of the toner particles by an aqueous alkaline or acidic solution.

Abstract: A process for preparing a toner obtained by a suspension polymerization method comprises stirring a mixture containing at least a polymerizable monomer containing 5 to 500 ppm of a polymerization inhibitor dissolved in the polymerizable monomer and a colorant; preparing a polymerizable monomer composition by adding a polymerization initiator to said mixture; stirring the prepared polymerizable monomer composition; and carrying out suspension polymerization of the polymerizable monomer composition dispersed in an aqueous medium.