Canon Kabushiki Kaisha

Masao Takano

Takashige Kasuya

Hiroshi Yusa

Yuki Karaki

Kazuo Maruyama

Takakuni Kobori

Nobuyuki Okubo

Tsutomu Onuma

Keita Nozawa

Motoo Urawa

Masaichiro Katada

A magnetic toner includes magnetic toner particles containing at least a binder resin and a magnetic iron oxide. The magnetic iron oxide contains 0.2 to 4.0% by weight of at least one metal element selected from the group consisting of Mn, Zn, Ni, Cu, Co, Cr, Cd, Al, Sn and Mg, and 0.2 to 0.8% by weight of silicon element on the basis of an iron element; the ratio (B.sub.si /A.sub.Si).times.100 of the content B.sub.Si of the silicon element present in the magnetic iron oxide up to an iron element solubility of 20% by weight to the total content A.sub.Si of the silicon element present in the magnetic iron oxide is 45 to 85%; the ratio (C.sub.si /A.sub.Si).times.100 of the content C.sub.Si of the silicon element present in the magnetic iron oxide up to an iron element solubility of 10% by weight to the total content A.sub.Si is 35 to 70%; and the magnetic toner has a weight average particle diameter of 3.5 to 10.0 .mu.m, and contains 0 to 30% by volume of magnetic toner particles having a volume particle diameter of 12.7 .mu.m or more determined from a volume distribution.

Magnetic toner, image forming method and process cartridge

A toner for forming an image has toner particles containing at least a colorant, a binder resin and a wax. The toner has (i) a circularity distribution in which the toner has an average circularity of 0.900 to less than 0.965, contains 20 to 60% by number of particles with a circularity of less than 0.95 and has a mode circularity of 0.90 or more; and (ii) a particle size distribution in which the toner has a circle-equivalent average diameter of 2.0 to 10.0 .mu.m and has at least one peak of frequency by number in the region of a circle-equivalent diameter of 0.6 to 3.0 .mu.m and at least one peak of frequency by number in the region of a circle-equivalent diameter of from more than 3.0 .mu.m to 10.0 .mu.m. The wax has an endothermic main peak as measured by DSC of 60 to 120.degree. C. The binder resin contains THF soluble matter and 0 to 5.0% by weight of THF insoluble matter. The THF soluble matter having a molecular-weight distribution as measured by GPC in which the THF soluble matter has a content (M1) of 5% or less of a component with a molecular weight of less than 50,000, a content (M2) of 20 to 45% of a component with a molecular weight of 50,000 to 500,000, and a content (M3) of 2 to 25% of a component with a molecular weight exceeding 500,000 and the following condition (1) is satisfied:

Toner for forming an image, image forming method and heat-fixing method

A magnetic black toner for electrophotography, includes: (a) magnetic black toner particles containing a binder resin, a magnetic material in 30-200 wt. parts per 100 wt. parts of the binder resin, and a first solid wax, and (b) first inorganic fine powder. The first solid wax (ii) provides a DSC heat-absorption main peak in a range of 60.degree.-120.degree. C., and (iii) shows a molecular weight distribution factor Mw/Mn of 1.0-2.0. The binder resin (iv) has a THF (tetrahydrofuran)-insoluble content of at most 5 wt. %, and (v) contains a THF-soluble content showing a GPC molecular weight distribution including a content (M1) of 40-70% in molecular weights of below 5.times.10.sup.4, a content (M2.ltoreq.M1) of 20-45% in molecular weights of 5.times.10.sup.4 -5.times.10.sup.5, and a content (M3&lt;M2) of 2-25% in molecular weights exceeding 5.times.10.sup.5. (vi) The magnetic black toner exhibits a tan .delta. of 0.5-3.0 in a range of 150.degree.-190.degree. C. and a tan .delta. at 150.degree. C. that is equal to or larger than a tan .delta. at 100.degree. C. The magnetic black toner shows a good fixability in an oil-less fixation system to provide a fixed image having a gloss comparable to one obtained by a non-magnetic color toner.

Magnetic black toner and multi-color or full-color image forming method

Growing community of inventors

Susono, Japan

Masao Takano