公开(公告)号：US20190228889A1

公开(公告)日：2019-07-25

申请号：US16337195

申请日：2017-09-29

Applicant: DOWA ELECTRONICS MATERIALS CO., LTD.

Inventor： Kazuhiro YAMAGA ,  Tetsuya KAWAHITO ,  Toshihiko UEYAMA ,  Kenji SAKANE

IPC: H01F1/11 ,  C01G49/06

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 (σg) of major diameters is 1.45 or less, which are obtained by TEM observation.

公开(公告)号：US20180005737A1

公开(公告)日：2018-01-04

申请号：US15541505

申请日：2015-12-28

Applicant: DOWA ELECTRONICS MATERIALS CO., LTD.

Inventor： Kenji SAKANE ,  Tetsuya KAWAHITO

IPC: H01F1/03 ,  G11B5/842 ,  H01F1/00 ,  C01G49/06 ,  C01G51/00 ,  B82Y25/00 ,  H01F1/147 ,  G11B5/714 ,  B82Y40/00 ,  H01F1/153 ,  C01G53/00 ,  C01G23/00 ,  C01G45/00 ,  G01N23/20

CPC classification number: H01F1/0315 ,  B82Y25/00 ,  B82Y30/00 ,  B82Y40/00 ,  C01G23/003 ,  C01G45/006 ,  C01G49/0018 ,  C01G49/02 ,  C01G49/06 ,  C01G51/00 ,  C01G51/006 ,  C01G53/006 ,  C01P2002/52 ,  C01P2002/72 ,  C01P2004/04 ,  C01P2004/64 ,  C01P2006/42 ,  G01N23/20075 ,  G11B5/70642 ,  G11B5/712 ,  G11B5/714 ,  G11B5/842 ,  H01F1/0054 ,  H01F1/14725 ,  H01F1/15366

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.

公开(公告)号：US20210300779A1

公开(公告)日：2021-09-30

申请号：US16979241

申请日：2019-03-26

Applicant: DOWA ELECTRONICS MATERIALS CO., LTD. ,  THE UNIVERSITY OF TOKYO

Inventor： Shin-ichi OHKOSHI ,  Asuka NAMAI ,  Kenji SAKANE ,  Tetsuya KAWAHITO

IPC: C01G49/06 ,  H01F1/11

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] ε-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.

公开(公告)号：US20180033528A1

公开(公告)日：2018-02-01

申请号：US15552283

申请日：2016-03-11

Applicant: DOWA ELECTRONICS MATERIALS CO., LTD.

Inventor： Kenji SAKANE ,  Tetsuya KAWAHITO

IPC: H01F1/147 ,  C01F7/34 ,  C01F17/00 ,  C01G51/00

CPC classification number: H01F1/14733 ,  C01F7/34 ,  C01F17/0025 ,  C01F17/0043 ,  C01G49/06 ,  C01G51/40 ,  C01P2002/52 ,  C01P2004/64 ,  C01P2004/84 ,  C01P2006/11 ,  C01P2006/12 ,  C01P2006/42 ,  G11B5/70615 ,  G11B5/70621 ,  G11B5/70642 ,  G11B5/712 ,  G11B5/714 ,  G11B5/84 ,  H01F1/11

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.

公开(公告)号：US20180208479A1

公开(公告)日：2018-07-26

申请号：US15746459

申请日：2016-07-26

Applicant: DOWA ELECTRONICS MATERIALS CO., LTD.

Inventor： Kenji SAKANE ,  Tetsuya KAWAHITO

IPC: C01G51/00 ,  H01F1/11

CPC classification number: C01G51/40 ,  C01G49/00 ,  C01G49/06 ,  C01P2002/50 ,  C01P2002/52 ,  C01P2002/72 ,  C01P2004/04 ,  C01P2004/64 ,  C01P2006/42 ,  G11B5/70621 ,  G11B5/70642 ,  G11B5/714 ,  H01F1/11

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 10.0 or less; and then the iron oxyhydroxide containing the substituting metal element is coated with a silicon oxide and heated, so as to provide ε-type iron-based oxide magnetic particle powder containing the substituting metal element.

公开(公告)号：US20170287516A1

公开(公告)日：2017-10-05

申请号：US15511038

申请日：2015-09-17

Applicant: DOWA ELECTRONICS MATERIALS CO., LTD.

Inventor： Kenji SAKANE ,  Tetsuya KAWAHITO

IPC: G11B5/65 ,  C01G49/00 ,  H01F1/11 ,  C01G51/00

CPC classification number: G11B5/653 ,  B82Y25/00 ,  B82Y30/00 ,  B82Y40/00 ,  C01G49/0018 ,  C01G49/06 ,  C01G51/40 ,  C01P2002/50 ,  C01P2002/52 ,  C01P2002/72 ,  C01P2004/04 ,  C01P2004/51 ,  C01P2004/64 ,  C01P2006/42 ,  G11B5/70642 ,  G11B5/714 ,  H01F1/11 ,  Y10S977/773 ,  Y10S977/811 ,  Y10S977/896 ,  Y10S977/943

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.