Eastman-kodak Company

Bijay S Saha

Alec N Mutz

Robert E Zeman

Edward T Miskinis

Thomas K Hilbert

Thomas A Jadwin

James Hunter Anderson

James Raymond Flick

Orville C Rodenberg

Ashok K Agarwala

Carrier particles for an electrostatographic developer comprising a mixture of particles of a hard, magnetic ferrite material having a hexagonal crystalline structure of the general formula M0.6 Fe.sub.2 O.sub.3 in which M is strontium, barium or mixtures thereof exhibiting a coercivity of at least 300 Oersteds when magnetically saturated and an induced magnetic moment of at least 20 EMU/g when in an applied magnetic field of 1000 Oersteds in which from 1.0 to 10.0% by weight of the carrier particles in the mixture, based on the total weight of the mixture, have a number average particle diameter of from 1.0 to 10.0 micrometers and from 99.0 to 90.0% by weight of the carrier particles in the mixture, based on the total weight of the mixture, have a number average particle diameter of from 11.0 to 38.0 micrometers. The carrier particles provide developer compositions for magnetic brush development having high development speeds without the loss of copy image quality.

Developer compositions exhibiting high development speeds

Carrier particles for an electrostatographic developer comprising particles of a hard, magnetic ferrite material having a hexagonal crystalline structure of the general formula MO.6 Fe.sub.2 O.sub.3 in which M is strontium, barium or mixtures thereof exhibiting a coercivity of at least 300 Oersteds when magnetically saturated and an induced magnetic moment of at least 20 EMU/g when in an applied magnetic field of 1000 Oersteds and having a number average particle diameter of from 10.0 to 38.0 micrometers. The carrier particles provide developer compositions for magnetic brush development having high development speeds without the loss of copy image quality.

High speed developer compositions with ferrite carriers

The present invention relates to carrier particles which are used in image reproduction machines that include a magnetic brush for cleaning an imaging member. These carrier particles are utilized by the magnetic brush to clean the imaging member. The carrier particles include magnetic particles having a particle size distribution ranging from about 150 microns in diameter to about 1 micron in diameter. Preferably at least about 50% by weight of the magnetic particles have a diameter of less than about 45 microns. Preferably the carrier particles have an aspect ratio of about 8 and are made of stainless steel or iron.

Size distribution of carrier particles for use in a magnetic brush

A method of manufacturing improved strontium or barium ferrite carrier particles for use in two-component electrographic developer compositions for the development of electrostatic charge patterns is provided in which the tendency toward early life dusting of the strontium or barium ferrites is reduced. Such strontium or barium ferrite carrier particles are obtained by (i) mixing unreacted particles of iron oxide and barium or strontium oxide or, alternatively, a salt of barium or strontium convertible to the corresponding oxide by heat upon subsequent firing in a mole ratio of iron oxide to the metal oxide or salt of exactly 5.95 to 6.0:1 with an organic binder and a polar solvent, preferably water, to form a slurry, (ii) spray drying the slurry to obtain green beads of substantially uniform particle size and substantially spherical shape, and (iii) firing the beads at a temperature of from 1150.degree. to 1175.degree. C. for 10 hours to form magnetic strontium or barium ferrite carrier particles of substantially uniform particle size and substantially spherical shape having a reduced tendency towards early life dusting.

Low dusting carriers

A magnetic brush device for applying toner to an electrostatic image includes an applicator having a rotatable core. The sleeve for the core is made of an insulating material and preferably has a thin metallic coating on the outside of the sleeve defining the sleeve's outside surface.

Device for developing an electrostatic image on an image member

Carrier particles of substantially uniform particle size and substantially spherical shape comprising hard magnetic ferrite material having a single-phase hexagonal crystalline structure of the formula:

Method of preparing electrographic magnetic carrier particles

Carrier particles suitable for magnetic brush development comprising hard magnetic ferrite material having a single phase, W-type hexagonal crystalline structure represented by the formula MFe.sub.16 Me.sub.2 O.sub.27 where M is strontium or barium and Me is a divalent transition metal selected from the group consisting of nickel, cobalt, copper, zinc, manganese, magnesium, iron and mixtures thereof, exhibiting a coercivity of approximately 100 to 300 Oersteds when magnetically saturated and an induced magnetic moment of at least 60 EMU/g when in an applied magnetic field of 1000 Oersteds are disclosed. Also disclosed are electrostatic two-component dry developer compositions comprising charged toner particles mixed with oppositely charged carrier particles comprising the magnetically hard ferrite material described above and a method of developing an electrostatic charge pattern by contacting the charge pattern with a two-component dry developer composition described above. The carrier particles provide high development efficiencies and improved image density.

Magnetic carrier particles

Disclosed is an interdispersed two-phase ferrite composite which comprises, as a ferromagnetic phase, a magnetically hard ferrite material having a hexagonal crystalline structure of the general formula R.sub.x P.sub.(1-x) Fe.sub.12 O.sub.19 where R is selected from rare earth elements, P is selected from the group consisting of strontium, barium, lead, calcium and mixtures thereof and x has a value of from about 0.1 to about 0.4 exhibiting a coercivity of at least 300 Oersteds when magnetically saturated and an induced magnetic moment of at least 20 EMU/g when in an applied magnetic field of 1000 Oersteds and, as a ferroelectric phase, a ferroelectric material comprised of at least one of the double oxides of titanium, zirconium, tin, hafnium or germanium and either an alkaline earth or lead or cadmium, in which the mole ratio of the ferromagnetic phase to the ferroelectric phase is from about 1:1 to about 1:4. Also disclosed are carrier particles formed from magnetized particles of the composite which optionally can be polymerically coated, an electrostatic two-component dry developer composition comprising electrically insulative charged toner particles mixed with oppositely charged carrier particles formed from magnetized, and optionally polymerically coated, particles of the composite suitable for extremely high speed copying applications without the loss of copy image quality, and a method of developing an electrostatic image by contacting the image with a two-component dry developer composition described above.

Two-phase ferroelectric-ferromagnetic composite and carrier therefrom

Disclosed is an interdispersed two-phase ferrite composite which comprises about 0.1 mole to about 1.0 mole of a spinel phase having the general formula MFe.sub.2 O.sub.4 where M is at least one element that forms a spinel ferrite and is selected from the group consisting of cobalt, manganese, iron and mixtures thereof, to about 2.5 moles of a magnetoplumbite phase having the general formula PO.6Fe.sub.2 O.sub.3, where P is selected from the group consisting of stontium, barium, calcium, lead and mixtures thereof. Also disclosed are carrier particles formed from magnetized particles of the composite which optionally can be polymerically coated, an electrostatic two-component dry developer composition comprising charged toner particles mixed with oppositely charged carrier particles formed from magnetized, and optionally polymerically coated, particles of the composite, and a method of developing an electrostastic image by contacting the image with a two-component dry developer composition described above.

Interdispersed two-phase ferrite composite and electrographic magnetic

Disclosed is an interdispersed three-phase ferrite composite which comprises from about 0.1 mole to about 1.0 mole of a spinel phase having the general formula MFe.sub.2 O.sub.4 where M is at least one element that forms a spinel ferrite and is selected from the group consisting of cobalt, manganese, iron and mixtures thereof, to about 2.5 moles of a magnetoplumbite phase having the general formula PO.6Fe.sub.2 O.sub.3 where P is selected from the group consisting of strontium, barium, calcium, lead and mixtures thereof and, as a third phase, from about 0.02 to about 2.0 percent by weight, based on the combined weight of the spinel phase and the magnetoplumbite phase, of TiO.sub.2 or SiO.sub.2. Also disclosed are carrier particles formed from magnetized particles of the composite which optionally can be polymerically coated, an electrostatic charged toner particles mixed with oppositely charged carrier particles formed from magnetized, and optionally polymerically coated, particles of the composite, and a method of developing an electrostatic image by contacting the image with a two-component dry developer composition described above.

Interdispersed three-phase ferrite composite and electrographic magnetic

Disclosed are two-phase glass composite carrier particles which comprise a composite of a magnetically hard ferrite material having a single phase hexagonal crystalline structure of the formula MO.6Fe.sub.2 O.sub.3 where M is barium, strontium or lead exhibiting a coercivity of at least 300 Oersteds when magnetically saturated and an induced magnetic moment of at least 20 EMU/gm when in an applied field of 1000 Oersteds which is dispersed in a glass matrix comprised of from about 10 to 20 molar percent CuO, from about 10 to 40 molar percent BaO and from about 10 to 40 molar percent B.sub.2 O.sub.3 ; or a glass matrix comprised of from about 10 to 20 molar percent of V.sub.2 O.sub.5, from about 10 to 40 molar percent BaO and from about 10 to 40 molar percent B.sub.2 O.sub.3. Also disclosed is an electrostatic two-phase dry developer composition comprising charged toner particles mixed with oppositely charged carrier particles as described above. A method of developing an electrostatic image by contacting the image with the two-phase dry developer composition also is disclosed. The developer compositions of the invention exhibit reduced toner throw-off and other disclosed advantages.

Glass composite magnetic carrier particles

A magnetic brush useful in an electrophotographic apparatus. An outer sleeve is made of non-magnetic metal. An inner core is disposed within the outer sleeve so as to permit relative rotation of the inner core and the outer sleeve. The inner core comprises a shaft, which is made of magnetic or non-magnetic metal, and a magnetic layer covering a generally cylindrical surface of the shaft. The magnetic layer consists essentially of a plasma-sprayed alloy of iron, a rare earth, and boron. The rare earth is selected from the group consisting of neodymium, praseodymium, and mixtures thereof. Neodymium is preferred. A bonding layer may be optionally provided, preferably an alloy of nickel, chromium, aluminum, and yttrium.

Magnetic brush, inner core therefor, and method for making such core

Disclosed is an interdispersed two-phase ferrite composite which comprises about 0.1 mole to about 1.0 mole of a spinel phase having the general formula MFe.sub.2 O.sub.4 where M is at least one element that forms a spinel ferrite, to about 2.5 moles of a magnetoplumbite phase having the general formula R.sub.x P.sub.1-x Fe.sub.12 O.sub.19 where R is selected from rare earth elements, P is selected from the group consisting of strontium, barium, calcium, lead, and mixtures thereof, and x has a value of from about 0.1 to about 0.4. Also disclosed is a carrier formed from magnetized and polymerically coated particles of the composite, a developer formed from a carrier and a toner, and a magnetic brush formed from a multiplicity of juxtaposed magnetically aligned hairs formed of the carrier.

Interdispersed two-phase ferrite composite and carrier therefrom

Disclosed are carrier particles which comprise magnetically hard ferrite material having a single phase hexagonal crystal structure, and which contain neodymium, praseodymium, samarium, europium, or a mixture thereof, or a mixture of one or more of those elements with lanthanum. Also disclosed in an electrostatic two-component dry developer composition comprising charged toner particles mixed with oppositely charged carrier particles which comprise this hard ferrite material. A method for developing an electrostatic image by contacting the image with a two-component dry developer composition is also disclosed.

Rare earth containing magnetic carrier particles

Hard ferrite magnetic carrier particles for use in two component developers together with toner particles for the development of electrostatic latent image patterns and containing from about 1 to about 5 percent by weight of lanthanum exhibit improved development efficiency.

Growing community of inventors

Rochester, NY, United States of America

Bijay S Saha