Magnetic carrier particles
First Claim
1. Carrier for use in the development of electrostatic latent images, the carrier comprising a core of a hard magnetic material having an outer surface with a conductive metal oxide composition disposed on the outer surface of the core, the metal oxide composition comprising an oxide of at least one metal.
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Accused Products
Abstract
Conductive hard magnetic carrier particles are disclosed which are useful for development of electrostatic latent images. The carrier particles comprise a core of a hard magnetic material, preferably a hard magnetic ferrite such as strontium ferrite, which has a metal oxide composition disposed on the outer surface of the core. The metal oxide composition comprises a layer of an oxide of at least one metal, and in some embodiments, the metal oxide composition may be represented by the formula MOn/2 where M is at least one multi-valent metal represented by Mn+ where n is an integer of at least 4. Also disclosed are carrier particles having the foregoing structure wherein the outer surface of the core further defines a transition zone which extends into the core of hard magnetic ferrite, wherein the ferrite crystal structure within the transition zone is doped with multi-valent metal ions of the formula Mn+, where n is an integer of at least 4. The carrier particles may be used in making single- and two-component developers for use development of electrostatic latent image patterns in an electrographic process. Also disclosed are methods for using such carrier particles in an electrographic process such that the speed and imaging of the process is improved.
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Citations
42 Claims
- 1. Carrier for use in the development of electrostatic latent images, the carrier comprising a core of a hard magnetic material having an outer surface with a conductive metal oxide composition disposed on the outer surface of the core, the metal oxide composition comprising an oxide of at least one metal.
- 20. Carrier for use in the development of electrostatic latent images, the carrier comprising a core of a hard magnetic ferrite material having a single-phase, hexagonal crystal structure, the core having an outer surface with a metal oxide composition disposed thereon represented by the formula MOn/2 wherein M is at least one multi-valent metal represented by Mn+ with n being an integer of at least 4, the outer surface further defining a transition zone which extends from the outer surface and into the core of the hard magnetic ferrite material where the single-phase hexagonal crystal structure within the transition zone is doped with ions of the at least one multi-valent metal ion of formula Mn+.
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42. A method for preparing carrier particles for use in the development of electrostatic latent images, the method comprising:
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providing a particulate core material comprised of particles of a hard magnetic material;
admixing the core particles with a solution comprising a solvent and at least one metal oxide precursor compound;
heating the core particles and the solution to remove solvent therefrom and coat the at least one metal oxide precursor compound onto the surface of the core particles; and
firing the so-coated core particles in an oxidizing atmosphere at a temperature sufficient to form a conductive metal oxide composition on the outer surface of the core particles, the conductive metal oxide composition comprising a layer of an oxide of at least one metal.
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Specification