Toda Kogyo Corporation

Shinji Uemoto

Koso Aoki

Hiromitsu Misawa

Eiichi Kurita

Naoki Uchida

Ryo Iwai

Mamoru Kamigaki

Kaori Kinoshita

Nanao Horiishi

Seiichi Takahashi

Toshiyuki Hakata

Hirofumi Kawasaki

Hiromitsu Sakurai

Kazushi Takama

Nobuya Shimo

Shigenori Harada

Kazuya Fujita

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 relates to a magnetic carrier for an electrophotographic developer comprising spherical composite particles comprising spherical composite core particles comprising at least ferromagnetic iron oxide fine particles and a cured phenol resin and having an average particle diameter of 1 to 100 &#x3bc;m, and a melamine resin coating layer formed on the respective core particles, wherein a ratio of Rto R(R/R) in which Ris an electric resistance value as measured when applying a voltage of 100 V to the magnetic carrier; and Ris an electric resistance value as measured when applying a voltage of 300 V to the magnetic carrier, is controlled to lie within the range of 1 to 50. The magnetic carrier according to the present invention is capable of maintaining an adequate electric resistance value upon development, providing images having an excellent image quality, exhibiting a good durability, obtaining a good reproducibility of uniform solid image portions having a high image density, and keeping high quality images having an excellent gradation for a long period of time.

Magnetic carrier for electrophotographic developer and process for producing the same, and two-component system developer

There are provided black iron-based particles comprising iron/titanium composite oxide particles having a titanium element content (A) of 5 to 35% by atom based on an iron element content contained in the black iron-based particles, and a ratio of a titanium element content (B) (based on an iron element content contained in the portion dissolved) in a portion of the black iron-based particles, which is dissolved therefrom at an iron element dissolution percentage of 1% by weight, to the titanium content (A) of not less than 1.0. The black iron-based particles of the present invention are not only excellent in dispersibility, acid resistance, tinting strength and blackness, but also exhibit a less magnetization value. Also, the black paint and the rubber or resin composition of the present invention are excellent in acid resistance and blackness.

Black iron-based particles, and black paint and rubber or resin composition using the same

There are provided a pharmaceutical raw material capable of exhibiting a uniform functionality and producing magnetic particle-containing drugs for diagnosis and medical treatments with a high reproducibility. The pharmaceutical raw material comprises a monodisperse colloid sterile aqueous solution of magnetic iron oxide fine particles having an average particle diameter of 5 to 30 nm, a saturation magnetization of 50 to 90 Am/kg and a coercive force of 0.1 to 1.6 kA/m. The pharmaceutical raw material can be produced by forming magnetic iron oxide fine particles in the form of a colloid aqueous solution, purifying the resultant colloid aqueous solution of superparamagnetic iron oxide particles by water-washing and removing water-soluble salts by-produced upon the reaction from the reaction solution by an ordinary method, and replacing a dispersing medium of the purified colloid aqueous solution with ultrapure water.

Pharmaceutical raw material

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

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.

Growing community of inventors

Otake, Japan

Shinji Uemoto