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公开(公告)号：US20200161035A1
公开(公告)日：2020-05-21
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
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.
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公开(公告)号：US20200185135A1
公开(公告)日：2020-06-11
申请号：US16702629
申请日：2019-12-04
Applicant: DOWA ELECTRONICS MATERIALS CO., LTD. , FUJIFILM Corporation
Inventor： Hirohisa OMOTO , Shuji KANEDA , Hiroyuki SUZUKI , Toshio TADA
Abstract: Provided is a hexagonal ferrite magnetic powder for a magnetic recording medium, containing hexagonal ferrite magnetic particles having aluminum hydroxide adhered on the surface thereof, the hexagonal ferrite magnetic powder having an Al/Fe molar ratio of 0.030 to 0.200, a Co/Fe molar ratio of 0.002 to 0.030, and a Nb/Fe molar ratio of 0.005 to 0.050, and having an Fe site valence AFe of 3.015 to 3.040 as calculated by AFe=(3+2×[Co/Fe]+5×[Nb/Fe])/(1+[Co/Fe]+[Nb/Fe]) wherein [Co/Fe] represents the Co/Fe molar ratio and [Nb/Fe] represents the Nb/Fe molar ratio, and preferably having an activation volume Vact of 1400 to 1800 nm3. This magnetic powder simultaneously achieves an increase in magnetic characteristics including SNR of a magnetic recording medium and a further increase in durability thereof.
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公开(公告)号：US20150123026A1
公开(公告)日：2015-05-07
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: H01F1/03
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.
Abstract translation: 提供了能够同时提高包括SNP的磁特性和磁记录介质的耐久性的磁粉。 用于磁记录介质的六方晶系铁氧体磁粉的Ba / Fe摩尔比为8.0％以上，Bi / Fe摩尔比为2.5％以上，Al / Fe摩尔比为3.0〜6.0％。 磁性粉末优选具有1400至1800nm 3的活化体积Vact。 磁性粉末特别优选具有159至279kA / m（约2,000至3,500Oe）的矫顽力Hc和0.3至1.0的矫顽力分布SFD。 作为代替六方晶系铁氧体的Fe部位的元素，可以含有选自二价过渡金属M1和四价过渡金属M2中的至少一种。
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公开(公告)号：US20230352224A1
公开(公告)日：2023-11-02
申请号：US18127707
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: A magnetic powder for a magnetic recording medium includes magnetic particles in which Ba in hexagonal barium ferrite is partially substituted with Sr, wherein a Dx volume represented by Dx volume (nm3) = Dxc × π × (Dxa/2)2 is 2,200 nm3 or less, and an Sr/(Ba+Sr) molar ratio is 0.01 to 0.15. One that satisfies Ku ≥ 0.1 × [Sr/(Ba+Sr) molar ratio] + 0.13 is more preferred. For the formulas, 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, π is a circular constant, and Ku is a magnetocrystalline anisotropy constant (MJ/m3). By providing the hexagonal ferrite magnetic powder formed of fine particles, an effect of improving the perpendicular squareness ratio SQ of a magnetic recording medium is large.
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公开(公告)号：US20160217817A1
公开(公告)日：2016-07-28
申请号：US15002599
申请日：2016-01-21
Applicant: DOWA ELECTRONICS MATERIALS CO., LTD. , FUJIFILM Corporation
Inventor： Kenji MASADA , Hirohisa OMOTO , Futoshi NAGASHIMA , Hiroyuki SUZUKI , Toshio TADA
IPC: G11B5/72
CPC classification number: G11B5/70678 , H01F1/11
Abstract: A hexagonal ferrite magnetic powder for a magnetic recording medium, containing magnetic powder contains hexagonal ferrite particles having coated on the surface thereof an aluminum hydroxide material, having a Ba/Fe molar ratio of 0.080 or more, a Bi/Fe molar ratio of 0.025 or more, and an Al/Fe molar ratio of from 0.030 to 0.200. The magnetic powder preferably has an activation volume Vact of from 1,300 to 2,000 nm3. The magnetic powder particularly preferably has a coercive force Hc of from 159 to 287 kA/m (approximately from 2,000 to 3,600 Oe) and a coercivity distribution SFD of from 0.3 to 1.0. The magnetic powder may contain one or two or more kinds of a divalent transition metal M1 and a tetravalent transition metal M2, as an element that replaces Fe of the hexagonal ferrite. The magnetic powder has improved magnetic characteristics including SNR and durability.
Abstract translation: 含有磁性粉末的磁记录介质的六方晶系铁氧体磁粉包含六方晶系铁氧体颗粒，其表面上涂有BaO / Fe摩尔比为0.080以上，Bi / Fe摩尔比为0.025或 更多，Al / Fe摩尔比为0.030〜0.200。 磁性粉末的活化体积V act优选为1300〜2000nm 3。 磁性粉末特别优选具有159至287kA / m（约2,000至3600Oe）的矫顽力Hc和0.3至1.0的矫顽力分布SFD。 磁性粉末可以含有一种或两种以上的二价过渡金属M1和四价过渡金属M2，作为取代六方晶系铁氧体的Fe的元素。 磁粉具有改善的磁特性，包括SNR和耐久性。
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Patent Agency Ranking
公开(公告)号：US20190027181A1
公开(公告)日：2019-01-24
申请号：US16038847
申请日：2018-07-18
Applicant: FUJIFILM Corporation
Inventor： Eiki OZAWA , Toshio TADA , Norihito KASADA , Takuto KUROKAWA
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.
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公开(公告)号：US20190027176A1
公开(公告)日：2019-01-24
申请号：US16037564
申请日：2018-07-17
Applicant: FUJIFILM Corporation
Inventor： Takuto KUROKAWA , Norihito KASADA , Toshio TADA , Eiki OZAWA
IPC: G11B5/706
CPC classification number: G11B5/70615 , G11B5/70 , G11B5/70678 , G11B5/7085
Abstract: The magnetic recording medium includes a non-magnetic support and a magnetic layer containing ferromagnetic powder and a binder, in which the ferromagnetic powder is ferromagnetic hexagonal ferrite powder, the magnetic layer contains an abrasive, an intensity ratio of a peak intensity 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 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 contact angle with 1-bromonaphthalene measured within a surface of the magnetic layer is in a range of 50.0° to 55.0°.
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公开(公告)号：US20180240493A1
公开(公告)日：2018-08-23
申请号：US15900230
申请日：2018-02-20
Applicant: FUJIFILM Corporation
Inventor： Toshio TADA , Norihito KASADA
CPC classification number: G11B5/712 , G11B5/00813 , G11B5/70 , G11B5/70615
Abstract: The magnetic tape includes a non-magnetic support; and a magnetic layer including ferromagnetic powder and a binding agent on the non-magnetic support, in which a center line average surface roughness Ra measured regarding a surface of the magnetic layer is equal to or smaller than 1.8 nm, a logarithmic decrement acquired by a pendulum viscoelasticity test performed regarding the surface of the magnetic layer is equal to or smaller than 0.050, and ΔSFD in a longitudinal direction of the magnetic tape calculated by Expression 1: ΔSFD=SFD25° C.−SFD−190° C. is equal to or greater than 0.35. In Expression 1, the SFD25° C. is a 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 a switching field distribution SFD measured in a longitudinal direction of the magnetic tape at a temperature of −190° C.
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公开(公告)号：US20170186456A1
公开(公告)日：2017-06-29
申请号：US15388911
申请日：2016-12-22
Applicant: FUJIFILM Corporation
Inventor： Toshio TADA , Norihito KASADA , Masahito OYANAGI
CPC classification number: G11B5/714 , G11B5/7013 , G11B5/70678 , G11B5/708 , G11B5/712 , G11B5/78 , G11B5/845
Abstract: The magnetic tape has a nonmagnetic layer containing nonmagnetic powder and binder on a nonmagnetic support and a magnetic layer containing ferromagnetic powder and binder on the nonmagnetic layer, wherein a fatty acid ester is contained in at least the magnetic layer, the ferromagnetic powder is ferromagnetic hexagonal ferrite powder, 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, and ΔSFD in a longitudinal direction of the magnetic tape as calculated with Equation 1: ΔSFD=SFD25° C.−SFD−190° C., ranges from 0.50 to 1.60.
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10.发明公开公开(公告)号：US20230306995A1
公开(公告)日：2023-09-28
申请号：US18187017
申请日：2023-03-21
Applicant: FUJIFILM Corporation
Inventor： Toshio TADA , Hiroyuki Suzuki , Megumi Nakano
Abstract: The magnetic recording medium is used in a magnetic recording and reproducing device in which a reproduction bit size S is 40,000 nm2 or less, and a numerical value of a residual magnetic flux density Brvertical, which is expressed in a unit G, in a vertical direction of the magnetic recording medium is X or more. The X is a value calculated as X = -0.01S + 1550.
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