Patents by Inventor Tetsuya KAWAHITO

Tetsuya KAWAHITO has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 11264155
    Abstract: An object of the present invention is to provide a magnetic powder having a narrow particle size distribution of epsilon-type iron oxide particles, and another object is to provide magnetic powder suitable for magnetic recording medium by improving particle size distribution, and provide epsilon-type iron oxide magnetic particles and related technologies in which a number average particle diameter of major diameters (D50) is 10 to 20 nm, a 90% cumulative particle diameter (D90) is 30 nm or less, and a geometric standard deviation (?g) of major diameters is 1.45 or less, which are obtained by TEM observation.
    Type: Grant
    Filed: September 29, 2017
    Date of Patent: March 1, 2022
    Assignee: DOWA ELECTRONICS MATERIALS CO., LTD.
    Inventors: Kazuhiro Yamaga, Tetsuya Kawahito, Toshihiko Ueyama, Kenji Sakane
  • Publication number: 20210300779
    Abstract: [Problem] To provide a method for producing iron based oxide magnetic powder that has a narrow particle size distribution and a small content of fine particles that do not contribute to the magnetic recording characteristics, and consequently has a narrow coercive force distribution and is suitable for the enhancement of the recording density of the magnetic recording medium. [Solution] ?-Type iron based oxide magnetic powder is obtained by a wet method, then a tetraalkylammonium salt as a surface modifier is added to a slurry containing the magnetic powder to make a concentration of 0.009 mol/kg or more and 1.0 mol/kg or less, and simultaneously to make pH of 11 or more and 14 or less, and the slurry is subjected to a dispersion treatment and then classified, so as to provide iron based oxide magnetic powder having a narrow particle size distribution and a narrow coercive force distribution.
    Type: Application
    Filed: March 26, 2019
    Publication date: September 30, 2021
    Inventors: Shin-ichi OHKOSHI, Asuka NAMAI, Kenji SAKANE, Tetsuya KAWAHITO
  • Patent number: 11097956
    Abstract: A surface-modified iron-based oxide magnetic particle powder has good solid-liquid separation property in the production process, has good dispersibility in a coating material for forming a coating-type magnetic recording medium, has good orientation property, and has a small elution amount of a water-soluble alkali metal, and to provide a method for producing the surface-modified iron-based oxide magnetic particle powder. The surface-modified iron-based oxide magnetic particle powder can be obtained by neutralizing a solution containing dissolved therein a trivalent iron ion and an ion of the metal, by which the part of Fe sites is to be substituted, with an alkali aqueous solution, so as to provide a precursor, coating a silicon oxide on the precursor, heating the precursor to provide e-type iron-based oxide magnetic powder, and adhering a hydroxide or a hydrous oxide of one kind or two kinds of Al and Y thereto.
    Type: Grant
    Filed: March 11, 2016
    Date of Patent: August 24, 2021
    Assignee: DOWA ELECTRONICS MATERIALS CO., LTD.
    Inventors: Kenji Sakane, Tetsuya Kawahito
  • Patent number: 10919778
    Abstract: A method for making iron-based oxide magnetic particle powders having particular peak intensity and diffraction intensities, comprising neutralizing an aqueous solution containing a trivalent iron ion, alone or with a substituting metal (M), a step of adding hydroxycarboxylic acid to the neutralized solution to create a second solution including the hydroxycarboxylic acid D, another neutralizing step for the second solution, a coating step of silicon oxide coating iron oxyhydroxide with or without the substituted metal element found in the second neutralized solution, and heating the coated iron oxyhydroxide with or without the substituted metal element to form a silicon oxide coated iron oxide with or without the substituted metal element. After the second neutralization step, there is no water washing. As a result, the molar ratio D/(Fe+M) is between 0.125 and 1.0 and the silicon oxide coating can be uniform and the formation reaction of the hydroxide is not retarded.
    Type: Grant
    Filed: July 26, 2016
    Date of Patent: February 16, 2021
    Assignee: DOWA ELECTRONICS MATERIALS CO., LTD.
    Inventors: Kenji Sakane, Tetsuya Kawahito
  • Patent number: 10622127
    Abstract: An iron-based oxide magnetic particle powder has a narrow particle size distribution a small content of fine particles that do not contribute to magnetic recording characteristics, and a narrow coercive force distribution, to enhance magnetic recording medium density. Neutralizing an aqueous solution containing a trivalent iron ion and an ion of the metal substituting a part of the Fe sites by adding an alkali to make pH of 1.5 or more and 2.5 or less, adding a hydroxycarboxylic acid, and further neutralizing by adding an alkali to make pH of 8.0 or more and 9.0 or less are performed at 5° C. or more and 25° C. or less. A formed iron oxyhydroxide precipitate containing the substituting metal element is rinsed with water, then coated with silicon oxide, and then heated thereby providing e-type iron-based oxide magnetic particle powder. The rinsed precipitate may be subjected to a hydrothermal treatment.
    Type: Grant
    Filed: December 28, 2015
    Date of Patent: April 14, 2020
    Assignee: DOWA ELECTRONICS MATERIALS CO., LTD.
    Inventors: Kenji Sakane, Tetsuya Kawahito
  • Patent number: 10504548
    Abstract: An e-type iron-based oxide magnetic particle powder has narrow particle size distribution and has a low content of fine particles which do not contribute to magnetic recording characteristics. As a result, a narrow coercive force distribution is achieved and the powder is suitable for increasing recording density of a magnetic recording medium. The powder containing substituting metal elements can be obtained by: adding an alkali to an aqueous solution containing trivalent iron ions and ions of the metals for partially substituting Fe sites to neutralize the aqueous solution to a pH of 1.5 to 2.5; then adding a hydroxycarboxylic acid; further adding the alkali to neutralize the aqueous solution to a pH of 8.0 to 9.0; washing with water a precipitation of an iron oxyhydroxide containing the substituting metal elements produced; and coating the iron oxyhydroxide containing the substituting metal elements with a silicon oxide and heating the resultant.
    Type: Grant
    Filed: September 17, 2015
    Date of Patent: December 10, 2019
    Assignee: DOWA ELECTRONICS MATERIALS CO., LTD.
    Inventors: Kenji Sakane, Tetsuya Kawahito
  • Publication number: 20190228889
    Abstract: An object of the present invention is to provide a magnetic powder having a narrow particle size distribution of epsilon-type iron oxide particles, and another object is to provide magnetic powder suitable for magnetic recording medium by improving particle size distribution, and provide epsilon-type iron oxide magnetic particles and related technologies in which a number average particle diameter of major diameters (D50) is 10 to 20 nm, a 90% cumulative particle diameter (D90) is 30 nm or less, and a geometric standard deviation (?g) of major diameters is 1.45 or less, which are obtained by TEM observation.
    Type: Application
    Filed: September 29, 2017
    Publication date: July 25, 2019
    Applicant: DOWA ELECTRONICS MATERIALS CO., LTD.
    Inventors: Kazuhiro YAMAGA, Tetsuya KAWAHITO, Toshihiko UEYAMA, Kenji SAKANE
  • Publication number: 20180208479
    Abstract: To provide iron-based oxide magnetic particle powder that has a narrow particle size distribution and a small content of fine particles that do not contribute to the magnetic recording characteristics, which result in a narrow coercive force distribution, and is suitable for the enhancement of the recording density of the magnetic recording medium, and a method for producing the same. An alkali is added to an aqueous solution containing a trivalent iron ion and an ion of the metal substituting a part of Fe sites to neutralize the aqueous solution to pH of 1.0 or more and 3.0 or less; a hydroxycarboxylic acid D is added in an amount providing a molar ratio D/Fe with respect to the amount of the trivalent iron ion or a molar ratio (D/(Fe+M)) with respect to the total amount of the trivalent iron ion and the ion of the metal M in the case where the substituting metal ion is contained of 0.125 or more and 1.0 or less; an alkali is further added to neutralize to pH of 7.0 or more and 10.
    Type: Application
    Filed: July 26, 2016
    Publication date: July 26, 2018
    Inventors: Kenji SAKANE, Tetsuya KAWAHITO
  • Publication number: 20180033528
    Abstract: A surface-modified iron-based oxide magnetic particle powder has good solid-liquid separation property in the production process, has good dispersibility in a coating material for forming a coating-type magnetic recording medium, has good orientation property, and has a small elution amount of a water-soluble alkali metal, and to provide a method for producing the surface-modified iron-based oxide magnetic particle powder. The surface-modified iron-based oxide magnetic particle powder can be obtained by neutralizing a solution containing dissolved therein a trivalent iron ion and an ion of the metal, by which the part of Fe sites is to be substituted, with an alkali aqueous solution, so as to provide a precursor, coating a silicon oxide on the precursor, heating the precursor to provide e-type iron-based oxide magnetic powder, and adhering a hydroxide or a hydrous oxide of one kind or two kinds of Al and Y thereto.
    Type: Application
    Filed: March 11, 2016
    Publication date: February 1, 2018
    Inventors: Kenji SAKANE, Tetsuya KAWAHITO
  • Publication number: 20180005737
    Abstract: An iron-based oxide magnetic particle powder has a narrow particle size distribution a small content of fine particles that do not contribute to magnetic recording characteristics, and a narrow coercive force distribution, to enhance magnetic recording medium density. Neutralizing an aqueous solution containing a trivalent iron ion and an ion of the metal substituting a part of the Fe sites by adding an alkali to make pH of 1.5 or more and 2.5 or less, adding a hydroxycarboxylic acid, and further neutralizing by adding an alkali to make pH of 8.0 or more and 9.0 or less are performed at 5° C. or more and 25° C. or less. A formed iron oxyhydroxide precipitate containing the substituting metal element is rinsed with water, then coated with silicon oxide, and then heated thereby providing e-type iron-based oxide magnetic particle powder. The rinsed precipitate may be subjected to a hydrothermal treatment.
    Type: Application
    Filed: December 28, 2015
    Publication date: January 4, 2018
    Inventors: Kenji SAKANE, Tetsuya KAWAHITO
  • Publication number: 20170287516
    Abstract: An e-type iron-based oxide magnetic particle powder has narrow particle size distribution and has a low content of fine particles which do not contribute to magnetic recording characteristics. As a result, a narrow coercive force distribution is achieved and the powder is suitable for increasing recording density of a magnetic recording medium. The powder containing substituting metal elements can be obtained by: adding an alkali to an aqueous solution containing trivalent iron ions and ions of the metals for partially substituting Fe sites to neutralize the aqueous solution to a pH of 1.5 to 2.5; then adding a hydroxycarboxylic acid; further adding the alkali to neutralize the aqueous solution to a pH of 8.0 to 9.0; washing with water a precipitation of an iron oxyhydroxide containing the substituting metal elements produced; and coating the iron oxyhydroxide containing the substituting metal elements with a silicon oxide and heating the resultant.
    Type: Application
    Filed: September 17, 2015
    Publication date: October 5, 2017
    Inventors: Kenji SAKANE, Tetsuya KAWAHITO