Hitachi Metals, Ltd.

Akihiko Funakawa

Masumi Asanae

Masahisa Ochiai

Tsutomu Saitou

Fumio Kimura

Ryuji Goto

Toshihiko Noshiro

A developer for developing an electrostatic latent image is disclosed. It is obtained by mixing a chargeable magnetic toner mainly composed of a binder resin and magnetic powder, which toner has a volume resistivity of 10.sup.13 .OMEGA..multidot.cm or greater, with a magnetic carrier having a volume resistivity of 10 .OMEGA..multidot.cm or greater and less than 10.sup.6 .OMEGA..multidot.cm at a weight ratio of between 10:90-90:10. A method of forming an image is also disclosed. An electrostatic latent image is formed on an image carrier. A magnetic brush formed of the developer slides against the surface of the image carrier. The visualized toner image is transferred to a recording medium. The previously-applied toner remaining on the surface of the image carrier is removed after transferring is completed and an electrostatic latent image is visualized when the magnetic brush slides against the surface of the image carrier.

Developer for developing electrostatic latent image

A developer for developing an electrostatic latent image by a developing method of a type in which residual toner particles on an image-bearing member are recovered therefrom and reused for developing the electrostatic latent image, which comprises a magnetic toner and a magnetic carrier. The magnetic toner comprises a binder resin having a number average molecular weight of 2,000-100,000, a weight average molecular weight of 5,000-500,000, and a melt viscosity of 10.sup.5 P or less at 120.degree. C., a release agent having a softening point of 160.degree. C. or lower; and a magnetic powder. The magnetic toner particle is externally added on a surface thereof or internally added thereto with a surface treating agent comprising a fine powder of at least one metal salt of stearic acid, a fine powder of at least one inorganic oxide and an optional resin powder.

Developer for electrostatic latent image development

A magnetic toner includes at least binding resin (for instance, a styrene-acryl resin) and magnetic powder (for instance, Mn--Zn ferrite or Ni--Zn ferrite) having a saturation magnetization of at least 50 emu/g and a coercive force as measured under the magnetic field of 10 kOe not exceeding 50 Oe. An image formed by using this magnetic toner has high quality and is free of tailing.

Magnetic toner

A magnetic developer comprising magnetic toner particles each comprising a binder resin, magnetic powder and a first charge-controlling agent, and magnetic carrier particles in mixture, and further containing 0.05 to 1 part by weight of a second charge-controlling agent being provided on the outer surfaces of the magnetic toner particles on the basis of 100 parts by weight of the magnetic toner particles has better triboelectric characteristics and a highly stabilized image density in the continuous development.

Magnetic developer

A developing method in which a recording region is formed between a movable image carrying element made of a photo-semiconductive material with light-transmitting properties and a hollow-cylindrical, non-magnetic sleeve opposing the image carrying element and accommodating a permanent magnet with a plurality of magnetic poles thereon. An optical signal corresponding to an original is radiated onto the recording region from the back surface of the image carrying element so that toner in a magnetic developer supplied onto the sleeve, and conveyed to the recording region by relative movement of the sleeve and the permanent magnet is selectively adhered onto the surface of the image carrying element. The magnetic developer is a mixture of a toner capable of being charged into a same polarity as the image carrying element, and magnetic particles capable of being charged into either the opposite or same polarity with respect to that of the toner. The toner has a volume resistivity of not less than 10.sup.12 .OMEGA..multidot.cm, and an average particle size of 5 to 20 .mu.m. The magnetic particles have a volume resistivity of more than 2.times.10.sup.5 .OMEGA..multidot.cm but not more than 10.sup.12 .OMEGA..multidot.cm, and an average particle size of 10 to 100 .mu.m. When the magnetic particles are ones for being charged into the same polarity as the toner, they have a smaller absolute value of triboelectric charge than the toner.

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Kumagaya, Japan

Akihiko Funakawa