公开(公告)号：US09741479B2

公开(公告)日：2017-08-22

申请号：US14529544

申请日：2014-10-31

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

Inventor： Kenji Masada ,  Hirohisa Omoto ,  Futoshi Nagashima ,  Daisuke Abe ,  Toshio Tada ,  Norihito Kasada

IPC: H01F1/11 ,  H01F1/03 ,  G11B5/706 ,  C01G49/00

CPC classification number: H01F1/11 ,  C01G49/0036 ,  C01P2002/76 ,  C01P2006/42 ,  G11B5/70678

Abstract: Provided is magnetic powder capable of enhancing simultaneously both magnetic characteristics including SNP and durability of a magnetic recording medium. The hexagonal ferrite magnetic powder for a magnetic recording medium has a Ba/Fe molar ratio of 8.0% or more, a Bi/Fe molar ratio of 2.5% or more and an Al/Fe molar ratio of from 3.0 to 6.0%. The magnetic powder preferably has an activation volume Vact of from 1,400 to 1,800 nm3. The magnetic powder particularly preferably has a coercive force Hc of from 159 to 279 kA/m (which is approximately from 2,000 to 3,500 Oe) and a coercivity distribution SFD of from 0.3 to 1.0. The magnetic powder may contain, as an element that substitutes an Fe site of the hexagonal ferrite, at least one kind selected from divalent transition metals M1 and tetravalent transition metals M2.

公开(公告)号：US09721607B2

公开(公告)日：2017-08-01

申请号：US15197046

申请日：2016-06-29

Applicant: FUJIFILM Corporation

Inventor： Toshio Tada ,  Akinori Sugishima ,  Tatsuya Yamashita ,  Norihito Kasada ,  Masahito Oyanagi

IPC: G11B5/706 ,  G11B5/842 ,  G11B5/714

CPC classification number: G11B5/842 ,  G11B5/70678 ,  G11B5/714

Abstract: The magnetic recording medium has a magnetic layer comprising ferromagnetic powder and binder on a nonmagnetic support, wherein the ferromagnetic powder is ferromagnetic hexagonal ferrite powder, and the ferromagnetic hexagonal ferrite powder has a crystallite volume as determined by X-ray diffraction analysis ranges from 1,000 nm3 to 2,400 nm3, and a ratio of the crystallite size Dx(107) obtained from a diffraction peak of a (107) plane to a particle size in a direction of an easy axis of magnetization DTEM as determined by observation with a transmission electron microscope, Dx(107)/DTEM, is greater than or equal to 1.1.

公开(公告)号：US09721605B2

公开(公告)日：2017-08-01

申请号：US14978834

申请日：2015-12-22

Applicant: FUJIFILM Corporation

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

IPC: G11B5/71 ,  G11B5/73 ,  G11B5/84 ,  G11B5/842 ,  G11B5/70 ,  G11B5/78

CPC classification number: G11B5/71 ,  G11B5/70 ,  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 at least the magnetic layer comprises one or more components selected from the group consisting of a fatty acid and a fatty acid amide; a quantity of components selected from the group consisting of a fatty acid and a fatty acid amide per unit area of the magnetic tape among components that are extracted from a surface on the magnetic layer side of the magnetic tape is less than or equal to 15.0 mg/m2, and a concentration of carbon, C, that is obtained by X-ray photoelectron spectroscopy conducted at a photoelectron take-off angle of 10 degrees on the surface on the magnetic layer side of the magnetic tape is greater than or equal to 50 atom %.

公开(公告)号：US10910009B2

公开(公告)日：2021-02-02

申请号：US16012018

申请日：2018-06-19

Applicant: FUJIFILM Corporation

Inventor： Masahito Oyanagi ,  Norihito Kasada ,  Toshio Tada ,  Takuro Sugiyama

IPC: G11B5/78 ,  G11B5/708 ,  G11B5/842 ,  G11B5/71 ,  G11B5/714 ,  G11B5/712 ,  G11B5/706

Abstract: The magnetic tape has a magnetic layer containing ferromagnetic powder and binder on a nonmagnetic support, wherein the centerline average surface roughness Ra as measured on the surface on the magnetic layer side of the magnetic tape is less than or equal to 1.8 nm, and the logarithmic decrement as determined by a pendulum viscoelasticity test on the surface on the magnetic layer side of the magnetic tape is less than or equal to 0.050.

公开(公告)号：US10854232B2

公开(公告)日：2020-12-01

申请号：US16037681

申请日：2018-07-17

Applicant: FUJIFILM Corporation

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

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

Abstract: The magnetic recording medium includes a magnetic layer which contains ferromagnetic hexagonal ferrite powder and a binder, in which the magnetic layer contains an abrasive and a fatty acid ester, Int (110)/Int (114) of a crystal structure of the hexagonal ferrite, determined by performing XRD analysis on the magnetic layer by using an In-Plane method, is equal to or higher than 0.5 and equal to or lower than 4.0, a squareness ratio of the magnetic recording medium in a vertical direction is equal to or higher than 0.65 and equal to or lower than 1.00, FWHMbefore and FWHMafter is greater than 0 nm and equal to or smaller than 7.0 nm, and a difference between spacings measured within a surface of the magnetic layer by an optical interference method before and after the heating in a vacuum is greater than 0 nm and equal to or smaller than 8.0 nm.

公开(公告)号：US10854227B2

公开(公告)日：2020-12-01

申请号：US16038687

申请日：2018-07-18

Applicant: FUJIFILM Corporation

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

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

Abstract: The magnetic recording medium includes a non-magnetic support and a magnetic layer which contains ferromagnetic powder and a binder, in which the ferromagnetic powder is ferromagnetic hexagonal ferrite powder, the magnetic layer contains an abrasive, Int (110)/Int (114) of a crystal structure of the hexagonal ferrite, determined by performing X-ray diffraction analysis on the magnetic layer by using an In-Plane method, to a peak intensity of a diffraction peak of (114) plane of the crystal structure is equal to or higher than 0.5 and equal to or lower than 4.0, a squareness ratio of the magnetic recording medium in a vertical direction is equal to or higher than 0.65 and equal to or lower than 1.00, and a logarithmic decrement obtained by performing a pendulum viscoelasticity test on a surface of the magnetic layer is equal to or lower than 0.050.

公开(公告)号：US10692522B2

公开(公告)日：2020-06-23

申请号：US15705531

申请日：2017-09-15

Applicant: FUJIFILM Corporation

Inventor： Toshio Tada ,  Norihito Kasada ,  Masahito Oyanagi ,  Akinori Sugishima ,  Kengo Saito

IPC: G11B5/706 ,  G11B5/842 ,  G11B5/70 ,  G11B5/845 ,  G11B5/708

Abstract: The magnetic recording medium has a non-magnetic support and a magnetic layer which is provided on the support and contains ferromagnetic powder and a binder, in which the ferromagnetic powder is ferromagnetic hexagonal ferrite powder, the magnetic layer contains an abrasive, an intensity ratio (Int (110)/Int (114)) of a peak intensity Int (110) of a diffraction peak of (110) plane of a crystal structure of the hexagonal ferrite, determined by performing X-ray diffraction analysis on the magnetic layer by using an In-Plane method, to a peak intensity Int (114) of a diffraction peak of (114) plane of the crystal structure is equal to or higher than 0.5 and equal to or lower than 4.0, and a squareness ratio in a vertical direction is equal to or higher than 0.65 and equal to or lower than 1.00. The present invention also provides a method for manufacturing the magnetic recording medium.

公开(公告)号：US10431250B2

公开(公告)日：2019-10-01

申请号：US15900230

申请日：2018-02-20

Applicant: FUJIFILM Corporation

Inventor： Toshio Tada ,  Norihito Kasada

IPC: G11B5/71 ,  G11B5/712 ,  G11B5/706 ,  G11B5/008 ,  G11B5/70

Abstract: A magnetic tape includes a non-magnetic support; and a magnetic layer including ferromagnetic powder and a binding agent on the non-magnetic support. The center line average surface roughness Ra measured regarding the surface of the magnetic layer is less than or equal to 1.8 nm. The logarithmic decrement acquired by a pendulum viscoelasticity test performed regarding the surface of the magnetic layer is less than or equal to 0.050, and ΔSFD in a longitudinal direction of the magnetic tape calculated by Expression 1: ΔSFD=SFD25° C.−SFD−190° C. is greater than or equal to 0.35. In Expression 1, the SFD25° C. is the switching field distribution SFD measured in a longitudinal direction of the magnetic tape at a temperature of 25° C., and the SFD−190° C. is the switching field distribution SFD measured in a longitudinal direction of the magnetic tape at a temperature of −190° C.

公开(公告)号：US10026430B2

公开(公告)日：2018-07-17

申请号：US14867752

申请日：2015-09-28

Applicant: FUJIFILM Corporation

Inventor： Norihito Kasada ,  Masahito Oyanagi ,  Toshio Tada ,  Yasuhiro Kawatani

IPC: G11B5/708 ,  G11B5/70

Abstract: The magnetic tape comprises, on a nonmagnetic support, a nonmagnetic layer comprising nonmagnetic powder and binder, and on the nonmagnetic layer, a magnetic layer comprising ferromagnetic powder, nonmagnetic powder, and binder, wherein a total thickness of the magnetic tape is less than or equal to 4.80 μm, and a coefficient of friction as measured on a base portion of a surface of the magnetic layer is less than or equal to 0.35.

公开(公告)号：US09818517B2

公开(公告)日：2017-11-14

申请号：US14224726

申请日：2014-03-25

Applicant: FUJIFILM Corporation

Inventor： Toshio Tada ,  Hiroyuki Suzuki ,  Osamu Shimizu

IPC: G11B5/708 ,  H01F1/11 ,  G11B5/706

CPC classification number: H01F1/11 ,  G11B5/70615 ,  G11B5/70678

Abstract: Hexagonal ferrite magnetic particles have an activation volume ranging from 1,000 nm3 to 1,500 nm3, and ΔE10%/kT, thermal stability at 10% magnetization reversal, is equal to or greater than 40.