公开(公告)号：US09711174B2

公开(公告)日：2017-07-18

申请号：US14757555

申请日：2015-12-24

Applicant: FUJIFILM CORPORATION

Inventor： Norihito Kasada ,  Masahito Oyanagi ,  Toshio Tada ,  Kazuyuki Kitada

IPC: G11B5/71 ,  G11B5/73 ,  G11B5/84 ,  G11B5/842 ,  G11B5/78

CPC classification number: G11B5/71 ,  G11B5/7305 ,  G11B5/78 ,  G11B5/8404 ,  G11B5/842

Abstract: Provided is a magnetic tape, which comprises, on a nonmagnetic support, a nonmagnetic layer comprising nonmagnetic powder and binder, and on the nonmagnetic layer, a magnetic layer comprising ferromagnetic powder and binder; wherein a total thickness of the magnetic tape is less than or equal to 4.80 μm; at least the magnetic layer comprises one or more components selected from the group consisting of a fatty acid and a fatty acid amide; and a C—H derived carbon, C, concentration calculated from a C—H peak area ratio in a C1s spectrum obtained by X-ray photoelectron spectroscopy conducted at a photoelectron take-off angle of 10 degrees on a surface on the magnetic layer side of the magnetic tape is greater than or equal to 45 atom %.

公开(公告)号：US11894171B2

公开(公告)日：2024-02-06

申请号：US16683301

申请日：2019-11-14

Applicant: DOWA ELECTRONICS MATERIALS CO., LTD. ,  FUJIFILM Corporation

Inventor： Hirohisa Omoto ,  Shuji Kaneda ,  Satoshi Shiki ,  Hiroyuki Suzuki ,  Toshio Tada

IPC: H01F1/34 ,  C09C1/24 ,  H01F1/11

CPC classification number: H01F1/348 ,  C09C1/24 ,  H01F1/11 ,  C01P2002/76 ,  C01P2004/51 ,  C01P2004/61 ,  C01P2004/84 ,  C01P2006/42

Abstract: Provided is an Al-containing hexagonal ferrite magnetic powder which produces an excellent durability-improving effect on a magnetic recording medium, wherein uniform pulverization of the magnetic powder can be easily achieved by dispersion treatment in preparation of a magnetic coating material even in cases where the magnetic powder has a small primary particle size or has a composition which is likely to produce hard secondary particles. The magnetic powder for a magnetic recording medium is an Al-containing hexagonal ferrite magnetic powder having an Al/Fe molar ratio of 0.030 to 0.200, and has a particle size distribution in which the volume ratio of particles having a particle size of 30 μm or more as measured by a laser diffraction particle size distribution analyzer with a dispersion pressure of 100 kPa is 5.0% or less, and an activation volume Vact of 1800 nm3 or less.

公开(公告)号：US20230317337A1

公开(公告)日：2023-10-05

申请号：US18127722

申请日：2023-03-29

Applicant: DOWA ELECTRONICS MATERIALS CO., LTD. ,  FUJIFILM CORPORATION

Inventor： Akifumi ONODERA ,  Yasuto Miyamoto ,  Masaki Koshiko ,  Toshio Tada ,  Takashi Fujimoto

IPC: H01F1/34

CPC classification number: H01F1/348

Abstract: [Problem] A hexagonal barium ferrite magnetic powder formed of fine particles, wherein the anisotropic magnetic field distribution of a magnetic recording medium can be made to fall within a range effective in both improving the recording density and improving the SNR is provided.
[Solution] A magnetic powder for a magnetic recording medium including magnetic particles in which Ba in hexagonal barium ferrite is partially substituted with Sr, wherein a Dx volume represented by the following formula (1) is 2,200 nm3 or less, an Sr/(Ba+Sr) molar ratio is 0.01 to 0.30, and an anisotropic magnetic field distribution is 1.00 or less.


Dx volume (nm3)=Dxc×Π×(Dxa/2)2  (1)

Here, Dxc is a crystallite diameter (nm) in a c-axis direction of a hexagonal ferrite crystal lattice, Dxa is a crystallite diameter (nm) in an a-axis direction of the same crystal lattice, and n is a circular constant.

公开(公告)号：US10854229B2

公开(公告)日：2020-12-01

申请号：US16038847

申请日：2018-07-18

Applicant: FUJIFILM Corporation

Inventor： Eiki Ozawa ,  Toshio Tada ,  Norihito Kasada ,  Takuto Kurokawa

IPC: G11B5/706 ,  G11B5/78 ,  G11B5/71 ,  G11B5/712 ,  G11B5/84 ,  G11B5/708 ,  G11B5/714

Abstract: Provided is a magnetic tape in which an Ra measured regarding a surface of a magnetic layer is equal to or smaller than 1.8 nm, Int(110)/Int(114) of a hexagonal ferrite crystal structure obtained by an XRD analysis of the magnetic layer by using an In-Plane method is 0.5 to 4.0, a vertical squareness ratio of the magnetic tape is 0.65 to 1.00, full widths at half maximum of spacing distribution measured by optical interferometry regarding the surface of the back coating layer before and after performing a vacuum heating with respect to the magnetic tape are greater than 0 nm and equal to or smaller than 10.0 nm, and a difference between the spacings measured by optical interferometry regarding the surface of the back coating layer before and after performing the vacuum heating is greater than 0 nm and equal to or smaller than 8.0 nm.

公开(公告)号：US10854228B2

公开(公告)日：2020-12-01

申请号：US16038771

申请日：2018-07-18

Applicant: FUJIFILM Corporation

Inventor： Takuto Kurokawa ,  Norihito Kasada ,  Toshio Tada ,  Eiki Ozawa

IPC: G11B5/706 ,  G11B5/708 ,  G11B5/71 ,  G11B5/714 ,  G11B5/84 ,  G11B5/78 ,  G11B5/735 ,  G11B5/712

Abstract: The magnetic tape includes a magnetic layer including ferromagnetic powder, non-magnetic powder, and a binding agent and a back coating layer including non-magnetic powder and a binding agent, in which the ferromagnetic powder is ferromagnetic hexagonal ferrite powder, a center line average surface roughness measured regarding a surface of the magnetic layer is equal to or smaller than 1.8 nm, an intensity ratio of a peak intensity of a diffraction peak of a (110) plane with respect to a peak intensity of a diffraction peak of a (114) plane of a hexagonal ferrite crystal structure obtained by an X-ray diffraction analysis of the magnetic layer by using an In-Plane method is 0.5 to 4.0, a vertical squareness ratio of the magnetic tape is 0.65 to 1.00, and a contact angle with respect to 1-bromonaphthalene measured regarding a surface of the back coating layer is 15.0° to 30.0°.