Patents by Inventor Nobusuke Takumi

Nobusuke Takumi 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: 5609789
    Abstract: Cobalt-containing magnetic iron oxide particles extremely suitable for magnetic recording mediums, especially for image recording mediums and a process for producing the same from the precursor, .gamma.-FeOOH which is advantageous in industry are disclosed. Cobalt-containing magnetic iron oxide particles satisfying the following equations (1), (2) and (3):20.ltoreq.SSA.ltoreq.50 (1)-16.70.ltoreq.log [V].ltoreq.-3.05 log [SSA]-11.35 (2)0.10.ltoreq.Fe.sup.2+ /total Fe.ltoreq.0.30 (3)where SSA is a BET specific surface area (m.sup.2 /g), and V is a magnetic switching unit (cm.sup.3), can be produced by producing iron oxide particles having a concentration of Fe.sup.2+ of 0.10 to 0.36 as expressed by Fe.sup.2+ /total Fe from the precursor, .gamma.-FeOOH, and coating a cobalt compound or a combination of a cobalt compound and other metal compounds on the surfaces of the iron oxide particles.
    Type: Grant
    Filed: April 22, 1996
    Date of Patent: March 11, 1997
    Assignee: Ishihara Sangyo Kaisha, Ltd.
    Inventors: Kiyoshi Asano, Arata Koyama, Nobusuke Takumi, Shigeru Takatori, Kouichi Tamura, Tokuo Suita
  • Patent number: 5585032
    Abstract: Ferromagnetic fine powder for magnetic recording, characterized by comprising platelet like ferrite crystal particles which have such a metallic element composition that the Ba/Fe molar ratio is 1/50 to 1/8 and that the total amount of Ni and Zn is less than 0.5 mole and not less than 0.07 mole per mole of Fe, a crystal phase of magnetoplumbite phase, spinel phase or composite phase thereof and a saturation magnetization of 60 emu/g or more; and a process for producing said ferromagnetic fine powder for magnetic record.
    Type: Grant
    Filed: May 9, 1995
    Date of Patent: December 17, 1996
    Assignee: Ishihara Sangyo Kaisha, Ltd.
    Inventors: Kazuo Nakata, Masaharu Hirai, Nobusuke Takumi, Saburo Kato
  • Patent number: 5246609
    Abstract: A process for producing ferromagnetic fine particles for magnetic recording which comprises preparing a starting material solution containing Ba, Fe and Me (Me representing at least one element selected from the group consisting of Co, Ti, Ni, Mn, Zr, Zn, Ge, Nb and V, the amount of which is 0.2 mol or less per mol of Fe) selected such that the molar ratio of Ba/(Fe+Me) is (1+m)/12 (m being a number of 0.1 to 2), mixing this starting material solution with an alkaline solution to form a coprecipitate-containing alkaline suspension, collecting and using the coprecipitate as precursor, or subjecting the coprecipitate-containing alkaline suspension to a heat treatment at a temperature below 250.degree. C. to form a precursor, and calcining such precursor at 650.degree.-950.degree. C. to produce the hexagonal platelet Ba-ferrite particles. The process is further characterized in that a boron compound is contained in the precursor in an amount of (0.01 to 1) mmol (calculated as B.sub.2 O.sub.
    Type: Grant
    Filed: August 20, 1992
    Date of Patent: September 21, 1993
    Assignee: Ishihara Sangyo Kaisha, Ltd.
    Inventors: Kazuo Nakata, Masaharu Hirai, Nobusuke Takumi, Saburo Kato
  • Patent number: 4594267
    Abstract: A cobalt-containing magnetic iron oxide powder is provided by first coating a magnetic iron oxide base powder with a ferrous compound and then coating it with a cobalt compound. The cobalt-containing magnetic iron oxide powder provided is improved in stability of coercivity under aging and various other magnetic properties, and the magnetic tape produced by using the powder is also appreciably improved in stability of coercivity under aging as well as in various magnetic properties such as squareness, orientability and switching field distribution.
    Type: Grant
    Filed: March 25, 1985
    Date of Patent: June 10, 1986
    Assignee: Ishihara Sangyo Kaisha, Ltd.
    Inventors: Ichiro Honma, Masaharu Hirai, Masatoshi Amano, Nobusuke Takumi
  • Patent number: 4551327
    Abstract: An aqueous slurry of a magnetic iron oxide powder is mixed with a suspension prepared by neutralizing an aqueous ferrous salt solution with an alkali to form ferrous hydroxide and then adding an aqueous cobalt salt solution thereto, and the excess OH concentration of the mixed slurry is adjusted to 0.05 to 3 mol/l, thereby obtaining a cobalt-and ferrous iron-containing ferromagnetic iron oxide. The cobalt-and ferrous iron-containing ferromagnetic iron oxide is excellent in coercivity, distribution of coercivity and other magnetic properties, and the magnetic tape produced by using such iron oxide is also excellent in coercivity and switching field distribution.
    Type: Grant
    Filed: July 12, 1983
    Date of Patent: November 5, 1985
    Assignee: Ishihara Sangyo Kaishi, Limited
    Inventors: Ichiro Honma, Arata Koyama, Masatoshi Amano, Nobusuke Takumi