Toda Kogyo Corporation

Koso Aoki

Hiromitsu Misawa

Naoki Uchida

Kazuo Fujioka

Minoru Kozawa

Yoji Okano

Eiichi Kurita

Shinji Uemoto

Kazuyuki Hayashi

Ryo Iwai

Nanao Horiishi

Nobuya Shimo

Hiroko Morii

Tomoyuki Imai

Minoru Ohsugi

Mamoru Kamigaki

Masaaki Fukugauchi

Suehiko Miura

Sigenori Miyazaki

Yasuhiko Fujii

Hiroshi Sumita

Yusuke Shimohata

Kaori Kinoshita

Hiromitsu Sakurai

Kazushi Takama

Hiroshi Akai

Shigenori Harada

Minoru Kouzawa

Kazuya Fujita

Kohei Uehara

The present invention provides magnetic iron oxide particles having a high bonding property to a resin as well as a magnetic carrier for electrophotographic developers which is improved in durability by enhancing adhesion between a magnetic carrier core material and a coating resin. The magnetic iron oxide particles of the present invention are magnetic iron oxide particles having an average particle diameter of 0.5 to 30 &#x3bc;m onto which a plurality of granules are bonded, and the magnetic carrier for electrophotographic developers according to the present invention is a magnetic carrier for electrophotographic developers which comprises spherical magnetic composite particles produced by dispersing magnetic iron oxide particles in a binder resin in which the magnetic iron oxide particles comprise at least the above magnetic iron oxide particles having an average particle diameter of 0.5 to 30 &#x3bc;m onto which the plurality of granules are bonded.

Magnetic iron oxide particles, magnetic carrier for electrophotographic developers and process for producing the same, and two-component system developer

Black magnetic iron oxide particles having an average particle diameter of 0.05 to 2.0 &#x3bc;m and an electric resistance value at an applied voltage of 100 V of not less than 1&#xd7;10&#x3a9;&#xb7;cm. Also a magnetic carrier for electrophotographic developer having spherical magnetic composite particles obtained by dispersing black magnetic iron oxide particles in a binder resin. The magnetic carrier has an electric resistance value Rat an applied voltage of 100 V of 1&#xd7;10to 1&#xd7;10&#x3a9;&#xb7;cm, and an electric resistance value Rat an applied voltage of 300 V which satisfies the relationship represented by the formula:0.1&#x2266;300/100&#x2266;1.

Black magnetic iron oxide particles, magnetic carrier for electrophotographic developer and two-component developer

The present invention provides aniline black comprising no harmful substances such as chromium and copper in its products and having an excellent blackness and a high resistivity value, as well as provides a black resin composition, a water-based dispersion and a solvent-based dispersion which are colored with the aniline black and have an excellent dispersibility. The aniline black according to the present invention has a sulfur content of 0.2 to 6.0% by weight and comprises primary particles having an average major axis diameter of 0.05 to 0.80 &#x3bc;m.

Aniline black having specific sulfur content, and resin composition and water-based and solvent-based dispersions using the aniline black

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

There are provided magnetic iron oxide particles having an average particle diameter (Dp) of primary particles of 0.05 to 0.3 &#x3bc;m, an average particle diameter (Da) of secondary particles of 0.055 to 0.9 &#x3bc;m, and a ratio of the average particle diameter (Da) of the secondary particles to the average particle diameter (Dp) of the secondary particles (Da/Dp) of 1.1 to 3.0, as well as a magnetic toner containing the magnetic iron oxide particles. The magnetic iron oxide particles of the present invention are in the form of small agglomerated particles and exhibit an excellent dispersibility, and the magnetic toner using the magnetic iron oxide particles is excellent in electrification stability.

Magnetic iron oxide particles and magnetic toner using the same

Black iron-based particles comprise a FeTiO&#x2014;FeOsolid solution or a mixed composition of a FeTiO&#x2014;FeOsolid solution and an iron-based oxide having a spinel structure, and having a Ti content of from more than 10.0 atm % to 40.0 atm %, calculated as Ti, based on whole Fe, and a blackness (L* value) of 6 to 13.

Black iron-based particles and black toner containing the same

Black magnetic iron oxide particles and magnetic toner

Black magnetic iron oxide particles for magnetic toner and process for producing the same

Magnetite particles of the present invention have an average particle diameter of 0.05 to 0.50 .mu.m, each of the magnetite particles having a plurality of mountain-shaped protrusions with unsharpened crests on a surface of each magnetite particle, and the number of the mountain-shaped protrusions formed on the surface of each magnetite particle being in the range of 2 to 30 when viewed in projected plan; magnetic iron oxide particles for magnetic toner comprising not less than 60%, in particle number, of the said magnetite particles; and a magnetic toner comprising the said magnetic iron oxide particles and a binder resin. The magnetite particles of the present invention are free from the falling-off from toner particles. The toner particles of the present invention shows a good fluidity and produces visual images having a higher definition upon development of electrostatic latent images.

Magnetic toner particles comprising magnetite particles containing

Iron oxide particles

Magnetic particles for a magnetic toner comprise:

Magnetic particles for magnetic toner and process for producing the same

Magnetite particles of the present invention have an average particle diameter of 0.05 to 0.50 .mu.m, each of the magnetite particles having a plurality of mountain-shaped protrusions with unsharpened crests on a surface of each magnetite particle, and the number of the mountain-shaped protrusions formed on the surface of each magnetite particle being in the range of 2 to 30 when viewed in projected plan; magnetic iron oxide particles for magnetic toner comprising not less than 60%, in number, of the said magnetite particles; and a magnetic toner comprising the said magnetic iron oxide particles and a binder resin. The magnetite particles of the present invention are free from the falling-off from toner particles. The toner particles of the present invention shows a good fluidity and produces visual images having a higher definition upon development of electrostatic latent images.

Magnetite particles, magnetic iron oxide particles, process for the

A magnetic toner containing 100 parts by weight of magnetic Fe.sup.2+ -containing iron oxide particles having an average particle size of 0.05 to 0.30 .mu.m, containing not less than 0.9 atm % and less than 1.7 atm % of silicon, calculated as Si, based on Fe, having a substantially cubic shape each ridge of which has a curved surface, and having a ratio .phi. represented by the following formula of more than 1.0 and less than 1.4:

Magnetic particles for magentic toner and process for producing the same

Rubber or resin composition

Growing community of inventors

Hiroshima, Japan

Koso Aoki