Kyocera Mita Corporation

Other

Kouzou Teramoto

Hiroshi Mizuhata

Yukinori Nakayama

Kousuke Satou

Norio Kubo

Naruo Yabe

Takashi Nagai

Seiji Kikushima

Takeo Mizobe

Toru Takatsuna

Hiroaki Moriyama

Hidekazu Tamura

Hiroko Higuchi

Noriya Okamoto

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

A two-component developing agent retained on the periphery surface of a magnetic rollerand a development rollerare brought in contact with each other, the nonmagnetic toner in the two-component developing agent is electrostatically adhered to the periphery surface of the development roller, and the nonmagnetic toner on the development rolleris sprayed on the periphery surface of a photosensitive drum, thereby causing an image of an electrostatic latent image to appear on the photosensitive drumas a toner image. The two-component developing agent for an image forming device thus configured comprises a nonmagnetic toner comprising color particles, and a magnetic carrier, wherein the magnetic carrier has a resin coating layer on the magnetic particle surface, and the critical surface tension of this resin coating layer is 25 dyn/cm or less.

Two component developing agent

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.

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

A developing apparatus has a developer supporting member with a surface roughness R in the range from 3.0 to 5.5 &mgr;m and a one-component developer T with a bulk density in the range from 0.35 to 0.55 g/ml, and an image is developed by forming a layer of the developer T on the developer supporting member . This makes it possible to form a thin toner layer stably despite changes in ambient conditions, and to prevent low image density and fogging. The absolute value of the amount of electric charge with which the developer T is charged is preferably in the range from 3.0 to 10.0 &mgr;C/g. The developer supporting member is made preferably of stainless steel.

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Osaka, Japan

Kouzou Teramoto