Patents Assigned to Hoya Magnetics Singapore Pte. Ltd.
  • Publication number: 20040157006
    Abstract: After at least a magnetic layer is formed on a disk substrate, a carbon-based protection layer is formed by plasma CVD using a mixed gas of a hydrocarbon-based gas and a nitrogen gas under the condition that the temperature of the disk substrate with the magnetic layer formed thereon is higher than 200° C.
    Type: Application
    Filed: February 11, 2004
    Publication date: August 12, 2004
    Applicants: HOYA CORPORATION, HOYA MAGNETICS SINGAPORE PTE. LTD.
    Inventors: Takashi Sato, Kenji Ayama, Masafumi Ishiyama
  • Patent number: 6759138
    Abstract: In a magnetic recording medium which includes a base body (1-4), first and second magnetic layers (5 and 7), each being of a ferromagnetic material, and a spacer layer (6) formed between the first and the second magnetic layers for inducing antiferromagnetic exchange interaction between the first and the second magnetic layers, the second magnetic layer located farther from the base body than the first magnetic layer includes a primary layer (72) and a secondary layer (71) located nearer to the base body than the primary layer. The primary layer has a primary anisotropic magnetic field while the secondary layer has a secondary anisotropic magnetic field which is smaller than the primary anisotropic magnetic field. The first magnetic layer is for controlling the antiferromagnetic exchange interaction.
    Type: Grant
    Filed: July 2, 2002
    Date of Patent: July 6, 2004
    Assignees: Hoya Corporation, Hoya Magnetics Singapore PTE, Ltd.
    Inventors: Hiroshi Tomiyasu, Keiji Moroishi, Teiichiro Umezawa, Kenji Ayama
  • Publication number: 20030203244
    Abstract: In a magnetic recording medium (10) including a glass substrate (1) which has a principal surface and which includes a compressive stress layer (1aa) as a surface layer having the principal surface, and a magnetic layer (4) formed on the principal surface of the glass substrate, compressive stress produced on the principal surface of the glass substrate is equal to 3 kg/mm2 or more. The glass substrate has the principal surface provided with a texture (100) for inducing magnetic anisotropy in the magnetic layer. A distance from the principal surface of the glass substrate to the magnetic layer is equal to 1200 angstroms or less.
    Type: Application
    Filed: April 25, 2003
    Publication date: October 30, 2003
    Applicants: HOYA CORPORATION, HOYA MAGNETICS SINGAPORE PTE. LTD.
    Inventors: Hideki Isono, Hirotaka Tanaka, Teiichiro Umezawa, Tomotaka Yokoyama, Kenji Ayama
  • Publication number: 20030152810
    Abstract: In a magnetic recording medium including a glass substrate (1) having a principal surface on which at least a magnetic layer (4) is formed, the magnetic recording medium has a coercive force of 2500 oersted or more in a circumferential direction thereof. The principal surface of the glass substrate is provided with a texture having a predetermined surface roughness so that the magnetic layer is given circumferential magnetic anisotropy. The magnetic recording medium further includes a magnetic anisotropy inducing layer (2) formed between the glass substrate and the magnetic layer so that the magnetic recording medium has an oriented ratio (OR) of 1.1 or more. The oriented ratio (OR) is defined as a ratio of a magnetic characteristic in circumferential direction to another magnetic characteristic in the radial direction.
    Type: Application
    Filed: December 16, 2002
    Publication date: August 14, 2003
    Applicant: HOYA CORPORATION, HOYA MAGNETICS SINGAPORE PTE. LTD.
    Inventors: Hisao Kawai, Teiichiro Umezawa, Hirotaka Tanaka, Masaki Uemura
  • Publication number: 20030108774
    Abstract: In a magnetic recording medium including a substrate (1) having a principal surface on which first and second magnetic layers (5 and 7) and a spacer layer (6) are at least formed, each of the first and the second magnetic layers being of a ferromagnetic material, the spacer layer being formed between the first and the second magnetic layers for inducing antiferromagnetic exchange interaction between the first and the second magnetic layers, the principal surface of the substrate is provided with concentric textures to have a predetermined surface roughness so that the spacer layer has a uniform thickness. The first magnetic layer is for controlling the antiferromagnetic exchange interaction.
    Type: Application
    Filed: September 26, 2002
    Publication date: June 12, 2003
    Applicants: HOYA CORPORATION, HOYA MAGNETICS SINGAPORE PTE. LTD.
    Inventors: Hisao Kawai, Teiichiro Umezawa, Hirotaka Tanaka, Masaki Uemura
  • Publication number: 20030104248
    Abstract: In a magnetic recording medium which includes a base body (1-4), first and second magnetic layers (5 and 7), each being of a ferromagnetic material, and a spacer layer (6) formed between the first and the second magnetic layers for inducing antiferromagnetic exchange interaction between the first and the second magnetic layers, the second magnetic layer located farther from the base body than the first magnetic layer includes a primary layer (72) and a secondary layer (71) located nearer to the base body than the primary layer. The primary layer has a primary anisotropic magnetic field while the secondary layer has a secondary anisotropic magnetic field which is smaller than the primary anisotropic magnetic field. The first magnetic layer is for controlling the antiferromagnetic exchange interaction.
    Type: Application
    Filed: July 2, 2002
    Publication date: June 5, 2003
    Applicant: HOYA CORPORATION AND HOYA MAGNETICS SINGAPORE PTE. LTD.
    Inventors: Hiroshi Tomiyasu, Keiji Moroishi, Teiichiro Umezawa, Kenji Ayama