Kyocera Mita Corporation

Kousuke Satou

Hiroshi Mizuhata

Yukinori Nakayama

Kouzou Teramoto

Magnetic toner involves magnetic powderhaving the particle shape of an octahedronthat is a convex polyhedron surrounded by eight triangles as a basis, each of the vertexes and edges of the octahedron being in a curved surface shape, and having a portionthat can be taken as a straight line on the outer periphery of its projected image. Therefore, the magnetic toner is superior in both two contradictory properties, that is the property of making it easy for a charging amount to quickly rise as well as improving the charging amount and the property of making it difficult for charge-up to occur, thereby making it possible to form a good image under a wide environment. In an image forming method, an electrostatic latent image is developed into a toner image by a magnetic one-component jumping developing method using the magnetic toner.

Magnetic toner and image forming method using the same

The object is to provide a magnetic toner with which toner scattering, toner spent to carrier, development of scratch streaks by the magnetic brush on the photoreceptor drum can be prevented for a prolonged period and a good image characteristic (in image density and background fogging) can be maintained for a prolonged period, and an image forming method using the magnetic toner. A two-component developer comprising carriers and toner which contains magnetic particle at least in a binder resin thereof, the magnetic particle being of basically polyhedral shaped shape, vertexes and edges of said polyhedral shape being curved surfaces, said shape having peripheral parts taken as straight lines in a projected image thereof, saturation magnetization of said toner in a magnetic field of 79.6 kA/m being 4.0 to 15.0 Am/kg, is prepared, and the toner retaining members (carriers) bearing at least said magnetic toner to which electric charge is injected are allowed to face a latent image retaining member and an electrostatic latent image on said latent image retaining member is developed with said magnetic toner.

Magnetic toner for two-component developer and image forming method using the developer

The toner of the present invention is characterized in that the charges rise up rapidly, the charge quantity is not insufficient nor excessive, the photoreceptor contamination is minimized and the toner is endurable under harsh conditions and against the high stress usage. The magnetic particle contained in the toner is of average particle size 0.01 &#x3bc;m through 0.50 &#x3bc;m, is of octahedron shape that is a convex polyhedron surrounded by eight triangles as a basis, each of vertexes and edges of the octahedron being in a curved surface shape and having a portion that can be taken as a straight line on the outer periphery of a projected image of said octahedron. The sphericity of the toner is 0.94 through 0.98. Here, the sphericity is defined by C2/C1, where C1 is a circumferential length of an image projected on a plane and C2 is a circumferential length of an assumed circle area as same as that of the projected image. Further, a number content of the toner of particle size 0.6 &#x3bc;m through 2.0 &#x3bc;m is smaller than 10%.

Toner for developing electrostatic latent image and image forming method using the same

The developer comprises magnetic toners and the magnetic carriers which forms magnetic ears on the surface of the developing roller. The magnetic toner is of an average particle size 0.01 &#x3bc;m through 0.50 &#x3bc;m and is of octahedron shape that is a convex polyhedron surrounded by eight triangles as a basis, each of the vertexes edges of the octahedron shape toner being in a curved surface shape and having a portion that can be taken as a straight line on the outer periphery of a projected image of the octahedron shape toner. The magnetic ears are electrically charged by the friction between the magnetic toner and the magnetic carriers and the magnetic ears on the developing roller are carried to the electrostatic latent image on the photoreceptor. The latent image is developed by the magnetic toners in the magnetic ears, in a small gap between the developing roller and the photoreceptor.

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Osaka, Japan

Kousuke Satou