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

IPC: H01F1/34 ,  C09C1/24

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：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

IPC: H01F1/34 ,  G11B5/73

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.

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

IPC: G11B5/78 ,  G11B5/71 ,  G11B5/712 ,  G11B5/706 ,  G11B5/008

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：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°.

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

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

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.

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

IPC: G11B5/714 ,  G11B5/845 ,  G11B5/78 ,  G11B5/708 ,  G11B5/712

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.

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

IPC: G11B5/708 ,  G11B5/72 ,  G11B5/78

CPC classification number: G11B5/708 ,  G11B5/72 ,  G11B5/78

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.

公开(公告)号：US20180096700A1

公开(公告)日：2018-04-05

申请号：US15716622

申请日：2017-09-27

Applicant: FUJIFILM Corporation

Inventor： Atsushi MOROOKA ,  Toshio TADA

IPC: G11B5/008 ,  G11B5/706

CPC classification number: G11B5/00813 ,  G11B5/70 ,  G11B5/70678 ,  G11B5/78

Abstract: Provided is a magnetic tape in which a vertical direction squareness ratio and/or a longitudinal direction squareness ratio obtained by measurement performed by sweeping an external magnetic field in the magnetic tape in a predetermined range by a vibrating sample magnetometer is 0.70 to 1.00, and A calculated by Expression 1 is equal to or smaller than 5.0%. In Expression 1, n represents the number of measurement points measured at magnetic field strength of −40 kA/m to 40 kA/m during the sweeping and is 52, Mr(Hex) represents a magnetization quantity measured at magnetic field strength Hex, and μ represents an arithmetical mean of Mr(Hex) obtained by measurement performed in the range of the magnetic field strength during the sweeping. A = 100 × 1 n - 1  ∑ Hex = - 40  kA / m ∼ 40   kA / m   ( Mr  ( Hex ) - μ ) 2 / μ Expression   1

公开(公告)号：US20180082710A1

公开(公告)日：2018-03-22

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: G11B5/733 ,  G11B5/73

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：US20170053671A1

公开(公告)日：2017-02-23

申请号：US15241631

申请日：2016-08-19

Applicant: FUJIFILM Corporation

Inventor： Norihito KASADA ,  Masahito OYANAGI ,  Toshio TADA ,  Takuro SUGIYAMA

IPC: G11B5/78

CPC classification number: G11B5/78 ,  G11B5/70 ,  G11B5/735 ,  G11B5/842

Abstract: The magnetic tape has a magnetic layer containing ferromagnetic powder and binder on the surface on one side of a nonmagnetic support and has a backcoat layer containing nonmagnetic powder and binder on the surface on the other side of the nonmagnetic support, wherein the backcoat layer is less than or equal to 0.30 μm in thickness; and the logarithmic decrement as determined by a pendulum viscoelasticity test on the surface on the backcoat layer side of the magnetic tape is less than or equal to 0.060.

Abstract translation: 该磁带具有在非磁性载体一侧的表面上含有铁磁性粉末和粘合剂的磁性层，并且在非磁性载体的另一侧的表面上具有含有非磁性粉末和粘合剂的背涂层，其中背涂层较少 不大于或等于0.30μm厚度; 并且通过在磁带的背涂层侧的表面上的摆式粘弹性试验确定的对数减量小于或等于0.060。