Hitachi Metals, Ltd.

Toshio Kumakura

Akio Mukoh

Keitaro Yamashita

Masumi Asanae

Koji Noguchi

Hirosada Morishita

Yasuki Mori

Kazunori Tabaru

Takafumi Aoyama

A reversal development method comprising the steps of forming a latent electrostatic image on the surface of an image-carrying member having predetermined charging characteristics; supplying a developer to a non-magnetic, conductive sleeve containing a magnetic field-generating means and positioned opposite to the image-carrying member, the developer comprising a magnetic toner consisting essentially of a resin and magnetic powder and adapted to be charged with the opposite polarity to that of the latent electrostatic image; conveying the developer onto the image-carrying member surface by relative rotation of the sleeve to the magnetic field-generating means; and applying DC voltage of the same polarity as that of the latent electrostatic image to the sleeve so that the magnetic toner is attracted to the nonimage areas of the latent electrostatic image. The present invention can provide high-quality images with high optical density and resolution substantially without suffering from dispersed toner dust adhesion.

Electrophotographic reversal development method using magnetic field and

The invention involves a method for making one component or single component toner compositions for developing electrophotographic images. A binding component is mixed with magnetic particles, pulverized, then carbon black is mixed with the powder and fixed to the surface of the particles. Compositions having a measured resistivity of 4.3.times.10.sup.3 to 4.3.times.10.sup.6 ohm-cm at a D.C. field of below 20 volts/cm under substantially no-load conditions are selected for use.

Preparation method of magnetic toner

A toner cartridge suitable for use with a developing device of the magnetic brush type using a magnetic toner for an electrostatic recording apparatus including a hollow, cylindrical container closed at opposite ends and formed with a longitudinally extending toner supply opening. The container has a knob at one end and a projection on the outer circumferential surface of the other end. When the cartridge is fitted in a hopper, the projection is inserted in a guide groove formed in an upper portion of the hopper and the cartridge is moved deep into the hopper. Upon completion of fitting, the projection is released from engagement with the guide groove, to allow the container to rotate to feed a charge of magnetic toner from the vessel to the hopper.

Toner cartridge

A one-component magnetic developer powder for developing an electrostatic latent image formed according to an electrophotographic process comprising non-agglomerative essentially spherical members consisting essentially of plastics binder, magnetic particles and first electric conductive particles dispersed therein, and second electric conductive particles embedded on a spherical surface of the member, the resistivity of the surface layer of the powder being less than that of the inner portion. The developer powder according to the present invention has a good electrical uniformity and the flowability of the developer powder is very good. Productivity of the same is also very good.

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Omiya, Japan

Toshio Kumakura