Toda Kogyo Corporation

Mamoru Kamigaki

Hiroko Morii

Kazuyuki Hayashi

Keisuke Iwasaki

Yasuyuki Tanaka

Naoki Uchida

Ryo Iwai

Koso Aoki

Hiromitsu Misawa

Seiji Ishitani

Shinji Uemoto

Minoru Ohsugi

Mineko Ohsugi

Nobuya Shimo

Mineko Sakoda

Toru Iwaki

The present invention relates to black magnetic iron oxide particles comprising magnetite as a main component, wherein when the black magnetic iron oxide particles are molded into a tablet shape, an electric resistance value of the tablet in an alternating current electric field is controlled to produce an impedance of not less than 2&#xd7;10&#x3a9;cm as measured in a characteristic frequency range thereof. The black magnetic iron oxide particles according to the present invention can provide a toner capable of exhibiting a good charging performance and a uniform charging property under the high-temperature and high-humidity conditions, so that when developing an electrostatic latent image therewith, it is possible to obtain toner images having a high resolution or definition, and further the use of heavy metal elements in the black magnetic iron oxide particles can be minimized.

Black magnetic iron oxide particles

The present invention relates to a black magnetic iron oxide particles each having a polyhedral shape wherein when a percentage of dissolution of iron element based on a total amount of iron element contained in the black magnetic iron oxide particles is 50%, a percentage of dissolution of sulfur element based on a total amount of sulfur element contained in the black magnetic iron oxide particles is less than 40%.

Black magnetic iron oxide particles having a specific dissolution of sulfur element

The present invention relates to black magnetic iron oxide particles comprising core particles and a surface layer formed on a surface of the respective core particles which is made of a compound of at least one alkali earth metal element selected from the group consisting of Mg, Ca, Sr and Ba and an aluminum element, in which a content of the at least one alkali earth metal element present in the surface layer is from 100 ppm to 1000 ppm on the basis of a whole weight of the black magnetic iron oxide particles; a content of the aluminum element present in the surface layer is from 1000 ppm to 20000 ppm on the basis of a whole weight of the black magnetic iron oxide particles; a ratio [A/B] of the content [A (ppm)] of the aluminum element to the content [B (ppm)] of the at least one alkali earth metal element present in the surface layer is from 1 to 100; and a molded product comprising said black magnetic iron oxide particles has a breakdown voltage of not less than 400 V/cm.

Black magnetic iron oxide particles having high breakdown voltage

A functional material comprising fine coloring particles having an average primary particle diameter of 1 to 50 nm in a dried state, and having a BET specific surface area value of 30 to 500 m/g and a light transmittance of not less than 80%. The functional material composed of fine coloring particles, exhibits not only an excellent transparency but also a high tinting strength and a clear hue.

Functional material, dispersion containing the functional material, and process for producing the functional material

A magnetic recording medium comprises: Such a magnetic recording medium exhibits not only a smooth surface, a smaller light transmittance and a lower surface electrical resistivity value, but also a small friction coefficient and an excellent running durability.

Black magnetic acicular composite particles for magnetic recording medium and magnetic recording medium using the same

A magnetic recording medium using black magnetic acicular composite particles produced by forming a single carbon black coat between the surface of magnetic acicular cobalt-coated iron oxide particle or magnetic acicular metal particle and a coating comprising at least one organosilicon compound, in an amount of from more than 10 to 40 parts by weight based on 100 parts by weight of the magnetic acicular particles, exhibits not only a smooth surface, a smaller light transmittance and a lower surface electrical resistivity value, but also a small friction coefficient and an excellent running durability.

Black magnetic acicular containing composite particles magnetic recording medium

A magnetic recording medium including a non-magnetic base film; and a magnetic recording layer formed on the non-magnetic base film. The magnetic recording layer contains a filler, a binder resin and surface-modified magnetic particles having an average particle diameter of 0.01 to 0.7 &mgr;m and contains magnetic particles and a silane monomer coat formed on surface of the magnetic particle by a dry-mixing method.

Magnetic recording medium

Magnetic recording medium and magnetic composite particles or magnetic recording medium

Black plate-shaped ferrite composite particles with magnetoplumbite structure, particle size of 0.01 to 0.2 &mgr;m are surface coated with an organosilicon compound(s) and a carbon black coating is applied over the organosilicon coating layer. Optionally, a coating of silicon or aluminum oxide or hydroxide is provided on the surface of the black plate-shaped composite particles and below the organosilicon layer. The particles have a high blackness and when applied to a non-magnetic substrate with a binder resin to form a magnetic medium provide low light transmittance, low surface resistivity and a smooth surface.

Black plate-shaped ferrite composite particles with magnet oplumbite structure and magnetic recording medium using the same

Magnetic recording medium containing specific non-magnetic composite particles of coated hematite particles

A magnetic recording medium composed of a non-magnetic base film and a magnetic recording layer containing a binder resin, magnetic particles, and as a filler black composite hematite particles having an average diameter of 0.08 to 1.0 &mgr;m. The composite particles have cores of hematite particles which are surface coated with an organosilicon compound. A carbon black coating is formed on the organosilicon coating layer. In addition, the hematite core particles may have an oxide or hydroxide coating layer formed on the surface of the hematite core particle, between the organosilicon coating layer and the surface of the core particles. The magnetic recording medium has not only an excellent durability and a good electromagnetic performance, but also a low light transmittance, a small surface resistivity and an excellent surface smoothness.

A pigment of the present invention comprises:

Pigment, process for producing the same and paint using the same

The disclosure describes modified particles comprising inorganic particles as core particles, and at least one polysiloxane modified with at least one selected from the group consisting of polyethers, polyesters and aralkyls, which is coated on the surfaces of said core particles.

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Hatsukaichi, Japan

Mamoru Kamigaki