Canon Kabushiki Kaisha

Naoto Kitamori

Hisayuki Ochi

Manabu Ohno

Tetsuya Kuribayashi

Tetsuhito Kuwashima

Norio Hikake

Hitoshi Uchide

Hirohide Tanikawa

Katsuhiko Tanaka

Tsutomu Kukimoto

Masaki Uchiyama

Yasuo Mitsuhashi

Seiichi Kato

Nobuyuki Asaoka

A developer for developing electrostatic images, comprising: at least, 100 wt. parts of a negatively chargeable magnetic toner having a volume-average particle size of 5 to 30 microns; 0.1 to 3 wt. parts of positively chargeable resin particles having an average particle size of 0.1 to 1.0 micron; and 0.05 to 3 wt. parts of hydrophobic silica fine powder having a triboelectric chargeability of -100 to -300 .mu.c/g.

One component developer for developing electrostatic image and image

A developer for developing electrostatic images, comprising: 100 wt. parts of a toner comprising toner particles, and 0.01-3 wt. parts of silica powder which has a particle size of 0.006-0.2 micron and is not fixed to the surfaces of the toner particles; the toner particles comprising 100 wt. parts of colored resinous particles (A) and 0.05-5 wt. parts of silica powder comprising silica particles which have a particle size of 0.002-0.2 micron and have been embedded in the surfaces of the colored resinous particles by mechanical impact means.

Developer for developing electrostatic images

A developer for developing electrostatic images, comprising: at least, 100 wt. parts of a negatively chargeable magnetic toner having a volume-average particle size of 5 to 30 microns; 0.1 to 3 wt. parts of potitively chargeable resin particles having an average particle size of 0.1 to 1.0 micron; and 0.05 to 3 wt. parts of hydrophobic silica fine powder having a triboelectric chargeability of -100 to -300 .mu.c/g.

A positively chargeable, one component type magnetic developer, comprises:

Positively chargeable one component magnetic developer

Colored resinous particles suitable for use in toner powder for developing electrostatic latent images are produced from a pulverized feed at a good production efficiency and with a sharp particle size distribution through a classifying and pulverizing system including a second pulverization step associated with a second classification step in addition to a first classification step, such a second classification step and first pulverization step. The pulverized feed supplies to the first classification step is classified into a first classified fine powder and a first coarse powder, which is then pulverized in the first pulverization step and recycled to the first classification step. The first classified fine powder is supplied to the second classification step and classified therein into a second classified fine powder and a second coarse powder, which is then pulverized in the second pulverization step and recycled to the first classification step or the second classification step. The second pulverization step is effected under the action of an impact force which is smaller than that exerted in the first pulverization step.

Process for producing toner powder

A positively chargeable toner for developing electrostatic images in electrophotography, electrostatic recording, electrostatic printing, etc. The toner contains a binder resin, a colorant or magnetic material, and a diorganotin borate. Because of the diorganotin borate contained, the toner has a uniform and stable triboelectric chargeability. The improved properties of the toner are enhanced when it is combined with positively chargeable fine silica powder.

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Yokohama, Japan

Naoto Kitamori