Hitachi Metals, Ltd.

Fuji Xerox Co., Ltd.

Hitachi Metals Kiko, Ltd.

Masahisa Ochiai

Masumi Asanae

Tsutomu Saitoh

Toshihiko Noshiro

Koji Noguchi

Akihiko Funakawa

Keitaro Yamashita

Yoshimichi Katagiri

Fumio Kimura

Sadaaki Yoshida

Seijirou Ishimaru

Takashi Hayano

Toshihiro Noshiro

A magnetic black toner for electrophotography comprising a binding resin, a magnetic substance, and a pigment, wherein the pigment is at least one of phthalocyanine pigment and Mn containing hematite, and the content ratio of the magnetic substance and the pigment in the toner satisfy the following formulae: 10&#x2266;A&#x2266;30, 0.1&#x2266;B&#x2266;3, 5&#x2266;C&#x2266;40, wherein A denotes the content ratio (mass %) of the magnetic substance in the toner, B denotes the content ratio (mass %) of the phthalocyanine pigment in the toner, and C denotes the content ratio (mass %) of the Mn containing hematite in the toner.

Magnetic black toner for electrophotography having Mn-containing hematite compound and magnetic two-component developer for electrophotography containing the same

An image forming method for developing an electrostatic latent image on a moving image-bearing member with a magnetic developer and for removing the residual toner after transfer of a developed toner image onto a transfer member is described. The method includes providing a rotatable, cylindrical permanent magnet having a plurality of magnetic poles on the surface for supporting and conveying the magnetic developer directly on the magnet surface; forming an electrostatic latent image into a toner image by attracting and conveying a magnetic developer including a nonspherical magnetic toner obtained by a polymerization or a nonspherical magnetic or non-magnetic toner obtained by a polymerization and magnetic carriers; and removing the residual toner remaining on the image-bearing member after transferring this toner image by a cleaning blade. The method also includes a surface magnetic flux density ranging from 50 to 1200 G, and a value of h, defined as .pi.D.multidot.Vp/(M.multidot.Vm), of 2 or less wherein Vp (mm/s) is the moving speed of the image-bearer, and D (mm), M, and Vm (mm/s) are the outer diameter, the number of magnetic poles, and the peripheral speed of the permanent magnet, respectively.

Image forming developing method

An image forming method for operating a moving image-bearing member bearing an electrostatic latent image and a plurality of developing units disposed near the image-bearing member and being selectively operable is described. The color image forming method develops the electrostatic latent image by using a magnetic developer brush formed on the surface of a developer support and conveyance means, and includes the steps of: providing a rotating cylinder for supporting and conveying the magnetic developer, the cylinder including a permanent magnet with a plurality of magnetic poles on the cylinder surface; supplying a magnetic developer containing non-magnetic color toner for color image formation; attracting and conveying a layer of magnetic developer having a smaller thickness than the gap between the image-bearing member and the developer support and conveyance cylinder on the cylinder surface; and applying in the developing region an alternate electric field with an AC bias superimposed on a DC bias between the image-bearing member and the magnetic developer for the developing of an electrostatic latent image on the image-bearing member. The method also includes a surface magnetic flux density ranging from 50 to 1200 G, and a value of h, defined as .pi.D.multidot.V.sub.p /(M.multidot.V.sub.m), of 2 or less wherein V.sub.p (mm/s) is the moving speed of the image-bearer, and D (mm), M, and V.sub.m (mm/s) are the outer diameter, the number of magnetic poles, and the peripheral speed of the permanent magnet, respectively.

An image forming method for developing an electrostatic latent image on an image-bearing member that moves bearing electrostatic latent images formed of a two-component magnetic developer is described. The method includes the steps of providing a rotatable cylinder for supporting and conveying said magnetic developer, the cylinder including a permanent magnet with a plurality of magnetic poles provided on the surface. Magnetic carriers in the magnetic developer are attracted and conveyed on the surface of the permanent magnet, the magnetic carriers having an average particle size of 5 to 20 .mu.m and opposite to toner in polarity of charge. A carrier particle magnetization .sigma..sub.1000 in a magnetic field of 1000 Oe so as to amount to 50 emu/g or less is also used. The method also includes a surface magnetic flux density ranging from 50 to 1200 G, and a value of h, defined as .pi.D.multidot.Vp/(M.multidot.Vm), of 2 or less wherein Vp (mm/s) is the moving speed of the image-bearer, and D (mm), M, and Vm (mm/s) are the outer diameter, the number of magnetic poles, and peripheral speed of the permanent magnet, respectively.

An Li--Mn type ferrite carrier for use in electrophotographic development comprising ferrite particles having a chemical composition of 3 to 15% of Li.sub.2 O, 5 to 35% of MnO and 60 to 90% of Fe.sub.2 O.sub.3, each in terms of percent by mole. The ferrite particles consisting essentially of crystal grains having an average grain size of 1 to 50 .mu.m. The surface of the crystal grains is provided with a minute roughness or unevenness during the production of the ferrite carrier. The minute roughness on the grain surface enhances the ability of the ferrite carrier to triboelectrically charge the toner and the bonding strength of the resin coating to the carrier surface.

Ferrite carrier for electrophotographic development

An Li--Mn ferrite carrier comprising 2 to 15 mol % of Li.sub.2 O, 5 to 30 mol % of MnO and 60 to 90 mol % of Fe.sub.2 O.sub.3. The carrier may contain at least one sintering aid selected from the group consisting of CaO, Na.sub.2 O, SiO.sub.2, V.sub.2 O.sub.5, Al.sub.2 O.sub.3, As.sub.2 O.sub.3, Bi.sub.2 O.sub.3, Sb.sub.2 O.sub.3 and B.sub.2 O.sub.3 to improve the surface properties thereof. The carrier may be made sensitive to the intensity of electric field by regulating the specific volume resistivities at 200 V/cm and 10 kV/cm within the specific ranges. This carrier is particularly suitable in the reversal developing method, and in the developing method where an A.C. bias voltage is superimposed to a D.C. bias voltage.

Ferrite carrier, two-component developer and electrostatic imaging

A developer for electrostatic development, which is a mechanical mixture of a magnetic toner containing a binder resin and a magnetic powder as the essential component and a magnetic carrier having a specific volume resistance of 10.sup.9 .OMEGA..cndot. cm or more. The properties of the magnetic toner and the magnetic carrier are correlated to each other so that an average particle size of the magnetic carrier is 0.5 to 6 times an average particle size of the magnetic toner, a magnetization of the magnetic carrier is 0.5 to 4 times a magnetization of the magnetic toner, and a triboelectric charge w of the magnetic carrier (Qc) and a triboelectric charge of the magnetic toner (Qt) satisfy an equation: .vertline.Qt-Qc.vertline.=5 to 50 .mu.C/g.

Developer for electrostatic development and electrostatic developing

A ferrite carrier for use in electrophotographic development of electrostatic latent images, which comprises a ferrite particles having an average particle size of 10 to 100 .mu.m, a specific resistivity of 10.sup.6 .OMEGA..cm or more and a chemical composition represented by the following formula:

A two-component magnetic developer containing a magnetic iron carrier and a non-magnetic or magnetic toner. The magnetic iron carrier is non-spherical in its shape and has an average particle size of 5-100 .mu.m. The non-magnetic or magnetic toner has an average particle size of 2-9 .mu.m and is produced by polymerizing a monomer for a binder resin. The toner concentration in the developer is 2-70 weight % in case of containing the non-magnetic toner and 10-90 weight % for the developer containing the magnetic toner.

Two component developer

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

In an image forming method for developing an electrostatic latent image on an image bearing member by using a two-component magnetic developer includes the steps of supporting and conveying a magnetic developer directly on the surface of a permanent magnet with a plurality of magnetic poles provided on the surface and performing both the removal of the residual toner remaining on the surface of the image-bearing member and the development of the electrostatic latent image while rubbing said surface with said magnetic brush. The magnetic carriers in the magnetic developer have average particle sizes of 5 to 20 .mu.m and opposite to toner in polarity of charge, the magnetization .sigma..sub.1000 in a magnetic field of 1000 Oe is 50 emu/g or less. Nonspherical magnetic toner or non-magnetic toner made by a polymerization process and magnetic carriers may be used.

Simultaneous developing/cleaning method using magnetic support member

A method in which a photoconductive surface is charged to a uniform potential by a charging brush and a two-component magnetic developer is directly attracted on the surfaced of a sleeve-less developing roll formed from a permanent magnet member and transported by the rotation of the permanent magnet member. An electrostatic latent image is developed with the transported magnetic developer in a developing zone to form a visual toner image on the photoconductive drum. The toner image is transferred to a recording sheet by a transfer roll and permanently fixed thereon by a suitable fixing means. The specific volume resistance of the magnetic carrier is restricted to a particular range to prevent the magnetic carrier from adhering to the photoconductive surface.

Method of electrostatically forming visual image

A method for developing electrostatic latent image on a rotating photoconductive drum by a magnetic developer transported by a rotating developing roll disposed opposite to the photoconductive drum, the developing roll being made of a cylindrical permanent magnet having on circumferential surface thereof equispaced magnetic poles extending along the axial direction. In the method the magnetic poles are equispaced by an inter-pole pitch of 0.5-10 mm, the photoconductive drum and the developing roll are rotated so as to move in opposite directions in an developing zone, and the ratio of peripheral speeds of the developing roll and photoconductive drum are regulated within 1 to 5. By the above method, an electrophotographic imaging apparatus can be reduced in the size thereof while reproducing high-quality images.

Method of developing electrostatic latent image

A method of developing an electrostatic latent image on a rotating image-bearing member with a magnetic developer in which a developing roll consist of only a permanent magnet member and the peripheral speed of the developing roll is regulated to be nearly equal to the moving speed of an image-bearing member. With such a construction, an electrophotographic recording apparatus can be miniaturized while producing an image of high quality.

A sleeveless magnet roller is formed of at least magnetic powder and resin. It is so arranged that, letting a developing gap Ds be the gap between an image-bearing member for holding an electrostatic latent image and a developer conveying member and a doctor gap Dg be the gap between the developer conveying member and a developer's thickness regulating member, one obtains Ds-Dg=0.1 to 0.3 (mm) and Dg=0 to 0.4 (mm). For image formation, one- or two-component magnetic developer is used and a bias voltage, formed by superimposing AC bias voltage to DC bias voltage, is applied to the developing region.

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Fukaya, Japan

Masahisa Ochiai