WO2021149716A1 - 磁気記録媒体 - Google Patents

磁気記録媒体 Download PDF

Info

Publication number
WO2021149716A1
WO2021149716A1 PCT/JP2021/001829 JP2021001829W WO2021149716A1 WO 2021149716 A1 WO2021149716 A1 WO 2021149716A1 JP 2021001829 W JP2021001829 W JP 2021001829W WO 2021149716 A1 WO2021149716 A1 WO 2021149716A1
Authority
WO
WIPO (PCT)
Prior art keywords
recording medium
magnetic
magnetic recording
layer
iron oxide
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/JP2021/001829
Other languages
English (en)
French (fr)
Japanese (ja)
Inventor
高橋　健
前嶋　克紀
山鹿　実
潤 寺川
奈津貴 市瀬
佐藤　友恵
嵩 潟口
篤哉 砥綿
尾崎　公洋
松本　章宏
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
National Institute of Advanced Industrial Science and Technology AIST
Sony Group Corp
Original Assignee
National Institute of Advanced Industrial Science and Technology AIST
Sony Group Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by National Institute of Advanced Industrial Science and Technology AIST, Sony Group Corp filed Critical National Institute of Advanced Industrial Science and Technology AIST
Priority to US17/789,685 priority Critical patent/US12614565B2/en
Priority to JP2021572760A priority patent/JP7590738B2/ja
Priority to DE112021000640.1T priority patent/DE112021000640T5/de
Publication of WO2021149716A1 publication Critical patent/WO2021149716A1/ja
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
    • G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
    • G11B5/706—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material
    • G11B5/70626—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material containing non-metallic substances
    • G11B5/70642—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material containing non-metallic substances iron oxides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/10—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials non-metallic substances, e.g. ferrites, e.g. [(Ba,Sr)O(Fe2O3)6] ferrites with hexagonal structure
    • H01F1/11—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials non-metallic substances, e.g. ferrites, e.g. [(Ba,Sr)O(Fe2O3)6] ferrites with hexagonal structure in the form of particles
    • H01F1/113—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials non-metallic substances, e.g. ferrites, e.g. [(Ba,Sr)O(Fe2O3)6] ferrites with hexagonal structure in the form of particles in a bonding agent
    • H01F1/117—Flexible bodies
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
    • G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
    • G11B5/706—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
    • G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
    • G11B5/714—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the dimension of the magnetic particles

Definitions

  • This disclosure relates to a magnetic recording medium.
  • Patent Document 1 proposes a magnetic recording medium having excellent electromagnetic conversion characteristics in a high temperature environment.
  • such a tape-shaped magnetic recording medium is expected to have high long-term reliability while improving electromagnetic conversion characteristics.
  • the magnetic recording medium as one embodiment of the present disclosure has a magnetic layer and a substrate.
  • the magnetic layer has a magnetic powder containing ⁇ iron oxide.
  • the ratio (Hrp / Hc) of the residual coercive force (Hrp) measured using the pulsed magnetic field to the vertical coercive force (Hc) of the magnetic recording medium is 2.0 or less, and the saturation per unit area of the magnetic recording medium.
  • the magnetization (Mst) is 4.5 mA or more.
  • the magnetic recording medium as one embodiment of the present disclosure has the above-described configuration, it is possible to achieve both improvement in electromagnetic conversion characteristics and improvement in thermal stability.
  • FIG. 1 It is sectional drawing of the magnetic recording medium which concerns on one Embodiment of this disclosure.
  • An example of a diffraction pattern measured by in-plane X-ray diffraction (Cu tube) in the magnetic layer shown in FIG. 1 is schematically shown.
  • An example of the magnetization curve (MH loop) in the magnetic layer shown in FIG. 1 is shown.
  • An example of the magnetization curve (MH loop) in the magnetic layer as a reference example is shown.
  • the present disclosure proposes a magnetic recording medium in which, for example, a magnetic layer containing ⁇ -iron oxide is used to achieve both improvement of electromagnetic conversion characteristics and thermal stability, that is, ensuring long-term reliability.
  • FIG. 1 shows a cross-sectional configuration example of the magnetic recording medium 10 according to the embodiment of the present disclosure.
  • the magnetic recording medium 10 has a laminated structure in which a plurality of layers are laminated.
  • the magnetic recording medium 10 includes a long tape-shaped substrate 11, a base layer 12 provided on one main surface 11A of the base 11, and a magnetic layer provided on the base layer 12. 13 and a back layer 14 provided on the other main surface 11B of the substrate 11.
  • the surface 13S of the magnetic layer 13 is a surface on which the magnetic head travels while being in contact with the magnetic head.
  • the base layer 12 and the back layer 14 are provided as needed, and may be omitted.
  • the average thickness of the magnetic recording medium 10 is preferably, for example, 5.6 ⁇ m or less.
  • the magnetic recording medium 10 has a long tape shape, and travels along its own longitudinal direction during the recording operation and the reproduction operation.
  • the magnetic recording medium 10 is preferably used in a recording / reproducing device including, for example, a ring-shaped head as a recording head.
  • the base 11 is a non-magnetic support that supports the base layer 12 and the magnetic layer 13.
  • the substrate 11 is in the form of a long film.
  • the upper limit of the average thickness of the substrate 11 is preferably 4.2 ⁇ m or less, more preferably 4.0 ⁇ m or less.
  • the upper limit of the average thickness of the substrate 11 is 4.2 ⁇
  • the lower limit of the average thickness of the substrate 11 is preferably 3 ⁇ m or more, more preferably 3.2 ⁇ m or more. When the lower limit of the average thickness of the substrate 11 is 3 ⁇ m or more, the decrease in strength of the substrate 11 can be suppressed.
  • the average thickness of the substrate 11 is obtained as follows. First, a magnetic recording medium 10 having a width of 1/2 inch is prepared, and the magnetic recording medium 10 is cut out to a length of 250 mm to prepare a sample. Subsequently, the layers other than the substrate 11 of the sample, that is, the base layer 12, the magnetic layer 13, and the back layer 14 are removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, using a laser holo gauge (LGH-110C) manufactured by Mitutoyo Co., Ltd. as a measuring device, the thickness of the sample substrate 11 is measured at positions of 5 points or more. Then, the measured values are simply averaged (arithmetic mean) to calculate the average thickness of the substrate 11. The measurement position shall be randomly selected from the sample.
  • a laser holo gauge LGH-110C
  • the substrate 11 contains, for example, polyesters as a main component.
  • the substrate 11 may contain PEEK (polyetheretherketone) as a main component.
  • the substrate 11 may contain at least one of polyolefins, cellulose derivatives, vinyl resins, and other polymer resins in addition to polyesters or PEEK.
  • the substrate 11 contains two or more of the above materials, the two or more materials may be mixed, copolymerized, or laminated.
  • the polyesters contained in the substrate 11 include, for example, PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PBN (polybutylene naphthalate), PCT (polycyclohexylene dimethylene terephthalate), PEB (Polyethylene-p-oxybenzoate) and at least one of polyethylene bisphenoxycarboxylate.
  • the polyolefins contained in the substrate 11 include, for example, at least one of PE (polyethylene) and PP (polypropylene).
  • Cellulose derivatives include, for example, at least one of cellulose diacetate, cellulose triacetate, CAB (cellulose acetate butyrate) and CAP (cellulose acetate propionate).
  • the vinyl resin contains, for example, at least one of PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride).
  • polymer resins contained in the substrate 11 include, for example, PA (polyamide, nylon), aromatic PA (aromatic polyamide, aramid), PI (polyimide), aromatic PI (aromatic polyimide), PAI (polyamideimide). ), Aromatic PAI (Aromatic Polyamideimide), PBO (Polybenzoxazole, eg Zyrone®), Polyether, PEK (Polyether Ketone), Polyether Ester, PES (Polyether Sulfone), PEI ( It contains at least one of polyetherimide), PSF (polysulphon), PPS (polyphenylene sulfide), PC (polyamide), PAR (polyamide) and PU (polyurethane).
  • PA polyamide, nylon
  • aromatic PA aromatic polyamide, aramid
  • PI polyimide
  • PAI polyamideimide
  • Aromatic PAI Aromatic PAI
  • PBO Polybenzoxazole, eg Zyrone®
  • Polyether Polyether
  • the magnetic layer 13 is a recording layer for recording a signal, and has, for example, iron oxide containing an ⁇ iron oxide phase.
  • the magnetic layer 13 contains, for example, a magnetic powder, a binder and a lubricant.
  • the magnetic layer 13 may further contain additives such as conductive particles, an abrasive, and a rust preventive, if necessary.
  • the magnetic recording medium 10 Since the magnetic layer 13 contains the ⁇ iron oxide phase, for example, as illustrated in FIG. 2, the magnetic recording medium 10 has a first peak of 32.9 ° in a diffraction pattern by in-plane X-ray diffraction (Cu tube). It expresses PK1 and a second peak PK2 at 36.6 °.
  • FIG. 2 schematically shows an example of a diffraction pattern of the magnetic recording medium 10 measured by in-plane X-ray diffraction (Cu tube).
  • the peak position of the diffraction pattern shown in FIG. 2 is determined by using any analysis software attached to the X-ray diffraction (XRD) apparatus. At this time, certain processing necessary for analysis, such as averaging the obtained diffraction patterns, may be performed.
  • XRD X-ray diffraction
  • the fact that the first peak PK1 at 32.9 ° and the second peak PK2 at 36.6 ° are detected in the diffraction pattern by in-plane X-ray diffraction (Cu tube) of the magnetic layer 13 means that It shows that the magnetic layer 13 contains the ⁇ iron oxide phase.
  • the magnetic layer 13 has a high vertical coercive force Hc.
  • the in-plane XRD is measured as follows. The measurement sample is prepared by cutting out from an arbitrary data area of the magnetic tape wound in the cartridge. The size to be cut out is, for example, 12.65 mm ⁇ 60 mm.
  • the cut-out sample is attached to an amorphous glass substrate, the glass substrate is fixed to the XRD measurement stage using grease, and the necessary work such as alignment adjustment is performed to measure in-plane XRD.
  • the measurement conditions are shown below.
  • the saturation magnetization Mst per unit area of the magnetic recording medium 10 is preferably 4.5 mA or more.
  • the saturation magnetization Mst per unit area of the magnetic recording medium 10 is 4.5 mA or more, the output of the magnetic recording medium 10 can be further improved, and as a result, a good SNR (Signal-to-Noise Ratio) can be obtained. realizable. This is because the larger the saturation magnetization Mst per unit area of the magnetic layer 13, the higher the output as the magnetic recording medium 10, and the smaller the influence of the system noise of the magnetic head itself. Further, the saturation magnetization Mst per unit area of the magnetic layer 13 can be adjusted by adjusting the filling amount and composition of the magnetic powder contained in the magnetic layer 13.
  • the saturation magnetization Mst per unit area of the magnetic layer 13 can be increased.
  • the composition of the magnetic powder is adjusted by substituting a part of iron (Fe) of the ⁇ -iron oxide particles with an additive element such as cobalt (Co), and the synthesis conditions (magnetization temperature, etc.) of the magnetic powder are adjusted. By doing so, the mass magnetization of the magnetic powder can be increased, and the saturation magnetization Mst per unit area of the magnetic layer 13 can be increased.
  • the saturation magnetization Mst per unit area of the magnetic layer 13 is obtained as follows. First, three magnetic recording media 10 are laminated with a double-sided tape, and then punched out with a punch having a diameter of 6.39 mm to prepare a measurement sample. At this time, marking is performed with an arbitrary non-magnetic ink so that the longitudinal direction (traveling direction) of the magnetic recording medium 10 can be recognized. Then, the MH loop of the measurement sample (the entire magnetic recording medium 10) corresponding to the vertical direction (thickness direction) of the magnetic recording medium 10 is measured using a vibrating sample magnetometer (VSM).
  • VSM vibrating sample magnetometer
  • the coating film that is, the base layer 12, the magnetic layer 13, the back layer 14, and the like is wiped off with acetone, ethanol, or the like so that only the base 11 remains.
  • three of the obtained substrates 11 are laminated with a double-sided tape, and then punched out with a punch having a diameter of 6.39 mm to obtain a sample for background correction (hereinafter, simply a sample for correction).
  • the MH loop of the correction sample (base 11) corresponding to the vertical direction of the base 11 (vertical direction of the magnetic recording medium 10) is measured using the VSM.
  • the measurement conditions are: measurement mode: full loop, maximum magnetic field: 15 kOe, magnetic field step: 40 bits, Time constant of Locking amp: 0.3 sec, Waiting time: 1 sec, MH average number: 20.
  • background correction is performed by subtracting the MH loop of the correction sample (base 11) from the MH loop of the measurement sample (entire magnetic recording medium 10).
  • the MH loop after background correction is obtained.
  • the measurement / analysis program attached to the "VSMP7-15 type" is used for the calculation of this background correction.
  • the magnetic layer 13 has, for example, a surface 13S provided with a large number of dents. Lubricant is stored in these many dents. It is preferable that a large number of dents extend in the direction perpendicular to the surface of the magnetic layer 13. This is because the supply of the lubricant to the surface 13S of the magnetic layer 13 can be improved. It should be noted that a part of a large number of dents may be extended in the vertical direction.
  • the upper limit of the average thickness of the magnetic layer 13 is preferably 90 nm or less, particularly preferably 80 nm or less, more preferably 70 nm or less, and even more preferably 50 nm or less.
  • the upper limit of the average thickness of the magnetic layer 13 is 90 nm or less, when a ring-shaped head is used as the recording head, the magnetization can be uniformly recorded in the thickness direction of the magnetic layer 13, so that the electromagnetic conversion characteristics are improved. be able to.
  • the lower limit of the average thickness of the magnetic layer 13 is preferably 35 nm or more.
  • the output can be secured when the MR type head is used as the reproduction head, so that the electromagnetic conversion characteristics can be improved.
  • the average thickness of the magnetic layer 13 is obtained as follows. First, a carbon film is formed on the surface 13S of the magnetic layer 13 of the magnetic recording medium 10 and the surface 14S of the back layer 14 by a vapor deposition method, and then a tungsten thin film is deposited on the carbon film covering the surface 13S of the magnetic layer 13 by a vapor deposition method. Further form. These carbon film and tungsten film protect the sample in the flaking treatment described later.
  • the magnetic recording medium 10 is processed by a FIB (Focused Ion Beam) method or the like to thin it.
  • a carbon film and a tungsten thin film are formed as a protective film as a pretreatment for observing a TEM image of a cross section described later.
  • the carbon film is formed on the magnetic layer side surface and the back layer side surface of the magnetic recording medium 10 by a vapor deposition method, and the tungsten thin film is further formed on the magnetic layer side surface by a vapor deposition method or a sputtering method.
  • the thinning is performed along the length direction (longitudinal direction) of the magnetic recording medium 10.
  • the thinning forms a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic recording medium 10.
  • the cross section of the obtained sliced sample is observed with a transmission electron microscope (TEM) under the following conditions to obtain a TEM image.
  • TEM transmission electron microscope
  • the magnification and the acceleration voltage may be appropriately adjusted according to the type of the device.
  • the thickness of the magnetic layer 13 is measured at at least 10 points or more in the longitudinal direction of the magnetic recording medium 10.
  • the average value obtained by simply averaging (arithmetic mean) the obtained measured values is defined as the average thickness of the magnetic layer 13.
  • the position where the measurement is performed shall be randomly selected from the test pieces.
  • the magnetization curve (MH loop) representing the relationship between the magnetization M and the magnetic field H in the magnetic layer 13 is closed in the range of the magnetic field H exceeding -15 kOe and less than + 15 kOe. good. This is because better electromagnetic conversion characteristics can be obtained.
  • the term "closed" in the MH loop here means that, as shown in FIG. 3A, there is a portion overlapping the MH loop in the magnetic field H in the range of -15 kOe or more and + 15 kOe or less. means. In the example of FIG.
  • FIG. 3B shows an example of a magnetization curve (MH loop) showing the relationship between the magnetization M and the magnetic field H in the magnetic layer as a reference example.
  • MH loop magnetization curve
  • the magnetic powder contained in the magnetic layer 13 may have, for example, a mass magnetization ⁇ s of 30 emu / g or more and 60 emu / g or less.
  • a mass magnetization ⁇ s of 30 emu / g or more and 60 emu / g or less When the mass magnetization ⁇ s of the magnetic powder is 30 emu / g or more, improvement of the output as the magnetic recording medium 10 can be expected.
  • the magnetic powder contains, for example, a plurality of magnetic particles having an average particle size of 20 nm or less.
  • the magnetic powder contains, for example, powder of nanoparticles containing ⁇ -iron oxide (hereinafter referred to as “ ⁇ -iron oxide particles”). High coercive force can be obtained even with fine particles of ⁇ iron oxide particles. It is preferable that the ⁇ -iron oxide contained in the magnetic layer 13 is preferentially crystal-oriented in the thickness direction (vertical direction) of the magnetic recording medium 10.
  • FIG. 4 is a cross-sectional view schematically showing an example of the cross-sectional structure of the ⁇ -iron oxide particles 20 contained in the magnetic layer 13.
  • the ⁇ -iron oxide particles 20 have a spherical or substantially spherical shape, or have a cubic shape or a substantially cubic shape. Since the ⁇ -iron oxide particles 20 have the above-mentioned shape, when the ⁇ -iron oxide particles 20 are used as the magnetic particles, or when hexagonal plate-shaped magnetic particles such as hexagonal ferrite are used as the magnetic particles, In comparison, the contact area between particles per unit volume in the thickness direction of the magnetic recording medium 10 can be reduced, and aggregation of particles can be suppressed. Therefore, the dispersibility of the magnetic powder can be improved and a better SNR can be obtained.
  • the ⁇ iron oxide particles 20 may have, for example, a core-shell type structure. Specifically, as shown in FIG. 4, the ⁇ -iron oxide particles 20 include a core portion 21 and a shell portion 22 having a two-layer structure provided around the core portion 21.
  • the shell portion 22 having a two-layer structure has a first shell portion 22a provided on the core portion 21 and a second shell portion 22b provided on the first shell portion 22a.
  • the ⁇ -iron oxide particles 20 preferably contain both cobalt (Co) and zirconium (Zr) as additive elements.
  • the ⁇ iron oxide particles 20 are formed as follows, for example. First, a silicon compound is added to a solution containing a first compound containing an iron element and a second compound containing the additive element to produce a silica xerogel containing the iron element and the additive element in silica. The resulting silica xerogel is then heat treated at a temperature of 850 to 1300 ° C. for 4 to 6 hours. By doing so, ⁇ -iron oxide particles 20 containing ⁇ -iron oxide and the above-mentioned additive elements are formed. The amount of the additive element in the ⁇ iron oxide particles 20 in the present disclosure is the abundance ratio (atomic%, at%) of the additive element when the atomic% of Fe and the additive element is 100. To say.
  • the content of the additive element in the ⁇ iron oxide particles 20 is measured as follows, for example. First, a carbon film is formed on the surface 13S of the magnetic layer 13 of the magnetic recording medium 10 and the surface 14S of the back layer 14 by a vapor deposition method, and then a tungsten thin film is deposited on the carbon film covering the surface 13S of the magnetic layer 13 by a vapor deposition method. Further form. These carbon film and tungsten film protect the sample in the flaking treatment described later. Next, the magnetic recording medium 10 is processed by a FIB (Focused Ion Beam) method or the like to thin it.
  • FIB Fluorused Ion Beam
  • a carbon film and a tungsten thin film are formed as a protective film as a pretreatment for observing a TEM image of a cross section described later.
  • the carbon film is formed on the magnetic layer side surface and the back layer side surface of the magnetic recording medium 10 by a vapor deposition method, and the tungsten thin film is further formed on the magnetic layer side surface by a vapor deposition method or a sputtering method.
  • the thinning is performed along the length direction (longitudinal direction) of the magnetic recording medium 10. That is, the thinning forms a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic recording medium 10.
  • the cross section of the obtained sliced sample is observed with a scanning electron microscope (SEM) under the following conditions to obtain an SEM image.
  • SEM scanning electron microscope
  • the magnification and the acceleration voltage may be appropriately adjusted according to the type of the device.
  • the recording layer is subjected to elemental analysis under the following conditions.
  • EDS Energy Dispersive X-ray Spectroscopy
  • the core portion 21 of the ⁇ -iron oxide particles 20 contains ⁇ -iron oxide.
  • the iron oxide contained in the core portion 21 preferably has ⁇ -Fe 2 O 3 crystals as the main phase, and more preferably composed of single-phase ⁇ -Fe 2 O 3.
  • the ⁇ -iron oxide contained in the core portion 21 is made into fine particles.
  • the finely divided ⁇ -iron oxide exhibits a high coercive force, its mass magnetization ⁇ s tends to be small.
  • a decrease in the mass magnetization ⁇ s of the magnetic powder may lead to a decrease in the output of the magnetic recording medium 10 and a decrease in thermal stability, which is not preferable. Therefore, Co (cobalt) is added to the core portion 21. This is because the mass magnetization ⁇ s of the ⁇ -iron oxide particles 20 can be expected to be improved by adding Co to the ⁇ -iron oxide.
  • the core portion 21 further contains Zr (zirconium) together with Co.
  • Zr zirconium
  • the average valence can be made trivalent, which may have the effect of facilitating the introduction of the Co element.
  • the divalent element Co can be more uniformly distributed to the ⁇ -iron oxide containing the trivalent element Fe, and the distortion of the MH loop can be eliminated or reduced.
  • the generation of sub-peaks in the SFD curve of the magnetic recording medium 10 is suppressed, and a wider region that can contribute to magnetic recording can be secured in the magnetic layer 13. Therefore, the magnetic recording medium 10 is advantageous for high-density recording.
  • the amount of Co added to the core portion 21 is preferably 3 atomic% or more and 20 atomic% or less, where 100 is the total atomic% of Fe and Co. Further, in that case, the amount of Zr added to the core portion 21 is preferably 1 atomic% or more and 8 atomic% or less, where 100 is the total atomic% of Fe, Co, and Zr.
  • the core portion 21 may contain a metal element such as Hf (hafnium) as a further additive element.
  • the first shell portion 22a covers at least a part of the periphery of the core portion 21. Specifically, the first shell portion 22a may partially cover the periphery of the core portion 21, or may cover the entire periphery of the core portion 21. From the viewpoint of making the exchange coupling between the core portion 21 and the first shell portion 22a sufficient and improving the magnetic characteristics, it is preferable to cover the entire surface of the core portion 21.
  • the first shell portion 22a is a so-called soft magnetic layer, and contains, for example, a soft magnetic material such as ⁇ -Fe, Ni—Fe alloy, CoOFe 2 O 3 or Fe—Si—Al alloy.
  • ⁇ -Fe may be obtained by reducing ⁇ -iron oxide contained in the core portion 21.
  • the second shell portion 22b is an oxide film as an antioxidant layer.
  • the second shell portion 22b contains ⁇ -iron oxide, aluminum oxide or silicon oxide.
  • the ⁇ -iron oxide contains, for example, at least one iron oxide of Fe 3 O 4 , Fe 2 O 3 and Fe O.
  • the ⁇ -iron oxide may be obtained by oxidizing ⁇ -Fe contained in the first shell portion 22a.
  • the ⁇ iron oxide particles 20 have the first shell portion 22a as described above, the ⁇ iron oxide particles (core shell) keep the coercive force Hc of the core portion 21 alone at a large value in order to ensure thermal stability.
  • the coercive force Hc of the particle) 20 as a whole can be adjusted to a coercive force Hc suitable for recording.
  • the ⁇ -iron oxide particles 20 have the second shell portion 22b as described above, the ⁇ -iron oxide particles 20 are exposed to the air in the manufacturing process of the magnetic recording medium 10 and before the process, and the particle surface. It is possible to suppress deterioration of the characteristics of the ⁇ iron oxide particles 20 due to the occurrence of rust or the like. Therefore, by covering the first shell portion 22a with the second shell portion 22b, deterioration of the characteristics of the magnetic recording medium 10 can be suppressed.
  • the average particle size (average maximum particle size) of the magnetic powder is preferably 20 nm or less, more preferably 8 nm or more and 16 nm or less, and even more preferably 8 nm or more and 13 nm or less.
  • a region having a size of 1/2 of the recording wavelength is the actual magnetization region. Therefore, a good SNR can be obtained by setting the average particle size of the magnetic powder to half or less of the shortest recording wavelength. Therefore, when the average particle size of the magnetic powder is 20 nm or less, good electromagnetic waves are obtained in a magnetic recording medium 10 having a high recording density (for example, a magnetic recording medium 10 configured to be able to record a signal at the shortest recording wavelength of 50 nm or less).
  • Conversion characteristics eg SNR
  • the average particle size of the magnetic powder is 8 nm or more, the dispersibility of the magnetic powder is further improved, and more excellent electromagnetic conversion characteristics (for example, SNR) can be obtained.
  • the average aspect ratio of the magnetic powder is preferably 1 or more and 3.0 or less, more preferably 1 or more and 2.8 or less, and even more preferably 1 or more and 1.8 or less.
  • the average aspect ratio of the magnetic powder is in the range of 1 or more and 3.0 or less, aggregation of the magnetic powder can be suppressed, and when the magnetic powder is vertically aligned in the process of forming the magnetic layer 13, the magnetic powder can be vertically oriented. It is possible to suppress the resistance applied to. Therefore, the vertical orientation of the magnetic powder can be improved.
  • the average particle size and average aspect ratio of the above magnetic powder are obtained as follows.
  • the magnetic recording medium 10 to be measured is processed by the FIB (Focused Ion Beam) method or the like to thin it. Slicing is performed along the length direction (longitudinal direction) of the magnetic tape. That is, this thinning forms a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic recording medium 10.
  • the obtained flaky sample contains the entire magnetic layer 13 with respect to the thickness direction of the magnetic layer 13 at an acceleration voltage of 200 kV and a total magnification of 500,000 times using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies). Observe the cross section and take a TEM photograph.
  • the major axis length DL means the maximum distance (so-called maximum ferret diameter) between two parallel lines drawn from all angles so as to be in contact with the contour of each particle.
  • the minor axis length DS means the maximum length of the particles in the direction orthogonal to the major axis length DL of the particles.
  • the major axis length DLs of the measured 50 particles are simply averaged (arithmetic mean) to obtain the average major axis length DLave.
  • the average major axis length DLave thus obtained is taken as the average particle size of the magnetic powder.
  • the average minor axis length DSave of the measured 50 particles is simply averaged (arithmetic mean) to obtain the average minor axis length DSave.
  • the average aspect ratio (DLave / DSave) of the particles is obtained from the average major axis length DLave and the average minor axis length DSave.
  • the average particle volume of the magnetic powder is preferably 5500Nm 3 or less, more preferably 270 nm 3 or more 5500Nm 3 or less, still more preferably 900 nm 3 or more 5500Nm 3 or less.
  • the average particle volume of the magnetic powder is 5500 nm 3 or less, the same effect as when the average particle size of the magnetic powder is 22 nm or less can be obtained.
  • the average particle volume of the magnetic powder is 270 nm 3 or more, the same effect as when the average particle size of the magnetic powder is 8 nm or more can be obtained.
  • Binder a resin having a structure in which a cross-linking reaction is applied to a polyurethane resin, a vinyl chloride resin, or the like is preferable.
  • the binder is not limited to these, and other resins may be appropriately blended depending on the physical characteristics required for the magnetic recording medium 10.
  • the resin to be blended is not particularly limited as long as it is a resin generally used in the coating type magnetic recording medium 10.
  • polyvinyl chloride polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic acid ester-acrylonitrile copolymer, acrylic acid ester-chloride.
  • thermosetting resins or reactive resins examples include phenol resins, epoxy resins, urea resins, melamine resins, alkyd resins, silicone resins, polyamine resins, urea formaldehyde resins and the like.
  • M in the above chemical formula is a hydrogen atom or an alkali metal such as lithium, potassium, or sodium.
  • polar functional group -NR1R2, -NR1R2R3 + X - as the side chain type having an end group of,> NR1R2 + X - include those of the main chain type.
  • R1, R2, and R3 in the above formula are hydrogen atoms or hydrocarbon groups
  • X - is a halogen element ion such as fluorine, chlorine, bromine, or iodine, or an inorganic or organic ion.
  • polar functional group -OH, -SH, -CN, an epoxy group and the like can also be mentioned.
  • the lubricant contained in the magnetic layer 13 contains, for example, a fatty acid and a fatty acid ester.
  • the fatty acid contained in the lubricant preferably contains, for example, at least one of a compound represented by the following general formula ⁇ 1> and a compound represented by the general formula ⁇ 2>.
  • the fatty acid ester contained in the lubricant preferably contains at least one of the compound represented by the following general formula ⁇ 3> and the compound represented by the general formula ⁇ 4>.
  • the compound represented by the general formula ⁇ 2> and the compound represented by the general formula ⁇ 3> By including two kinds of the compound represented by the general formula ⁇ 1> and the compound represented by the general formula ⁇ 4>, the compound represented by the general formula ⁇ 2> and the compound represented by the general formula ⁇ 4> By including two kinds of the compounds represented by, the compound represented by the general formula ⁇ 1>, the compound represented by the general formula ⁇ 2>, and the compound represented by the general formula ⁇ 3> are generally included.
  • the compound represented by the general formula ⁇ 4> By containing three kinds of the compounds, or represented by the compound represented by the general formula ⁇ 1>, the compound represented by the general formula ⁇ 2>, the compound represented by the general formula ⁇ 3>, and the compound represented by the general formula ⁇ 4>.
  • CH 3 (CH 2 ) k COOH ⁇ ⁇ ⁇ ⁇ 1> (However, in the general formula ⁇ 1>, k is an integer selected from the range of 14 or more and 22 or less, more preferably 14 or more and 18 or less.)
  • CH 3 (CH 2 ) n CH CH (CH 2 ) m COOH ⁇ ⁇ ⁇ ⁇ 2> (However, in the general formula ⁇ 2>, the sum of n and m is an integer selected from the range of 12 or more and 20 or less, more preferably 14 or more and 18 or less.)
  • p is an integer selected from the range of 14 or more and 22 or less, more preferably 14 or more and 18 or less, and q is a range of 2 or more and 5 or less, more preferably 2 or more and 4 It is an integer selected from the following range.) CH 3 (CH 2 ) p COO- (CH 2 ) q CH (CH 3 ) 2 ... ⁇ 4> (However, in the general formula ⁇ 4>, p is an integer selected from the range of 14 or more and 22 or less, and q is an integer selected from the range of 1 or more and 3 or less.)
  • the magnetic layer 13 includes aluminum oxide ( ⁇ , ⁇ or ⁇ alumina), chromium oxide, silicon oxide, diamond, garnet, emery, boron nitride, titanium carbide, silicon carbide, titanium carbide, and titanium oxide (titanium carbide). It may further contain rutile-type or anatase-type titanium oxide) and the like.
  • the base layer 12 is a non-magnetic layer containing a non-magnetic powder and a binder.
  • the base layer 12 may further contain at least one additive such as a lubricant, conductive particles, a curing agent, and a rust preventive, if necessary.
  • the base layer 12 may have a multi-layer structure in which a plurality of layers are laminated.
  • the average thickness of the base layer 12 is preferably 0.5 ⁇ m or more and 0.9 ⁇ m or less, and more preferably 0.6 ⁇ m or more and 0.7 ⁇ m or less.
  • the Young's modulus of the entire magnetic recording medium 10 is effectively reduced as compared with the case where the thickness of the substrate 11 is reduced. Therefore, tension control for the magnetic recording medium 10 becomes easy. Further, by setting the average thickness of the base layer 12 to 0.5 ⁇ m or more, the adhesive force between the base 11 and the base layer 12 is ensured. Moreover, the variation in the thickness of the base layer 12 can be suppressed, and the roughness of the surface 13S of the magnetic layer 13 can be prevented from becoming large.
  • the average thickness of the base layer 12 is calculated as follows, for example. First, a magnetic recording medium 10 having a width of 1/2 inch is prepared, and the magnetic recording medium 10 is cut out to a length of 250 mm to prepare a sample. Subsequently, with respect to the magnetic recording medium 10 of the sample, the base layer 12 and the magnetic layer 13 are peeled off from the substrate 11. Next, using a laser holo gauge (LGH-110C) manufactured by Mitutoyo Co., Ltd. as a measuring device, the thickness of the laminate of the base layer 12 and the magnetic layer 13 peeled off from the base 11 is measured at five or more points. do.
  • LGH-110C laser holo gauge
  • the measured values are simply averaged (arithmetic mean) to calculate the average thickness of the laminate of the base layer 12 and the magnetic layer 13.
  • the measurement position shall be randomly selected from the sample.
  • the average thickness of the base layer 12 is obtained by subtracting the average thickness of the magnetic layer 13 measured by using TEM as described above from the average thickness of the laminated body.
  • the base layer 12 may have pores, that is, the base layer 12 may be provided with a large number of pores.
  • the pores of the base layer 12 may be formed, for example, by forming pores (recesses) in the magnetic layer 13, and in particular, a large number of protrusions provided on the surface 14S of the back layer 14 of the magnetic recording medium 10. It can be formed by pressing the portion against the surface on the magnetic layer side. That is, by forming a recess corresponding to the shape of the protrusion on the surface 13S of the magnetic layer 13, pores can be formed in the magnetic layer 13 and the base layer 12, respectively. Further, pores may be formed as the solvent volatilizes in the drying step of the paint for forming the magnetic layer.
  • the solvent in the paint for forming the magnetic layer forms the base layer 12 when the lower layer is applied and dried. It can penetrate through the pores and into the underlying layer 12.
  • the solvent permeating into the base layer 12 volatilizes in the drying step of the magnetic layer 13
  • the solvent permeating into the base layer 12 moves from the base layer 12 to the surface 13S of the magnetic layer 13 to be finely divided. Holes may be formed.
  • the pores formed in this way may be, for example, one in which the magnetic layer 13 and the base layer 12 communicate with each other.
  • the average diameter of the pores can be adjusted by changing the type of solid content or solvent of the paint for forming a magnetic layer and / or the drying conditions of the paint for forming a magnetic layer.
  • an amount of a lubricant particularly suitable for good running stability appears on the magnetic layer side surface, and dynamic friction due to repeated recording or reproduction occurs.
  • the increase in the coefficient can be further suppressed.
  • the pores of the base layer 12 and the dents of the magnetic layer 13 are connected.
  • the fact that the pores of the base layer 12 and the dents of the magnetic layer 13 are connected means that some of the many pores of the base layer 12 and the many dents of the magnetic layer 13 are connected. It shall include the state where some things are connected.
  • the lubricant to the surface 13S of the magnetic layer 13 it is preferable that a large number of dents extend in the direction perpendicular to the surface 13S of the magnetic layer 13. Further, from the viewpoint of improving the supply of the lubricant to the surface 13S of the magnetic layer 13, the pores of the base layer 12 extending in the direction perpendicular to the surface 13S of the magnetic layer 13 and the surface of the magnetic layer 13 It is preferable that the recess of the magnetic layer 13 extending in the direction perpendicular to the 13S is connected.
  • the non-magnetic powder includes, for example, at least one of inorganic particle powder and organic particle powder. Further, the non-magnetic powder may contain carbon powder such as carbon black. In addition, one kind of non-magnetic powder may be used alone, or two or more kinds of non-magnetic powder may be used in combination.
  • Inorganic particles include, for example, metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, metal sulfides and the like.
  • Examples of the shape of the non-magnetic powder include, but are not limited to, various shapes such as a needle shape, a spherical shape, a cube shape, and a plate shape.
  • the binder in the base layer 12 is the same as that in the magnetic layer 13 described above.
  • the back layer 14 contains, for example, a binder and a non-magnetic powder.
  • the back layer 14 may further contain at least one additive such as a lubricant, a curing agent and an antistatic agent, if necessary.
  • the binder and non-magnetic powder in the back layer 14 are the same as the binder and non-magnetic powder in the base layer 12 described above.
  • the average particle size of the non-magnetic powder in the back layer 14 is preferably 10 nm or more and 150 nm or less, and more preferably 15 nm or more and 110 nm or less.
  • the average particle size of the non-magnetic powder in the back layer 14 is obtained in the same manner as the average particle size of the magnetic powder in the magnetic layer 13 described above.
  • the non-magnetic powder may include those having a particle size distribution of 2 or more.
  • the upper limit of the average thickness of the back layer 14 is preferably 0.6 ⁇ m or less, and particularly preferably 0.5 ⁇ m or less.
  • the thickness of the base layer 12 and the base 11 can be kept thick even when the average thickness of the magnetic recording medium 10 is 5.6 ⁇ m or less. , The running stability of the magnetic recording medium 10 in the recording / reproducing device can be maintained.
  • the lower limit of the average thickness of the back layer 14 is not particularly limited, but is, for example, 0.2 ⁇ m or more, and particularly preferably 0.3 ⁇ m or more.
  • the average thickness of the back layer 14 is obtained as follows. First, a magnetic recording medium 10 having a width of 1/2 inch is prepared, and the magnetic recording medium 10 is cut out to a length of 250 mm to prepare a sample. Next, using a laser holo gauge (LGH-110C) manufactured by Mitutoyo Co., Ltd. as a measuring device, the thickness of the magnetic recording medium 10 as a sample is measured at 5 points or more, and the measured values are simply averaged ( (Arithmetic mean) to calculate the average thickness t T [ ⁇ m] of the magnetic recording medium 10. The measurement position shall be randomly selected from the sample.
  • LGH-110C laser holo gauge
  • the measurement position shall be randomly selected from the sample.
  • the back layer 14 is removed from the magnetic recording medium 10 of the sample with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid.
  • a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid.
  • the thickness of the sample from which the back layer 14 is removed from the magnetic recording medium 10 is measured at 5 points or more, and the measured values are simply averaged (arithmetic mean) to back layer.
  • the average thickness t B [ ⁇ m] of the magnetic recording medium 10 from which 14 has been removed is calculated.
  • the measurement position shall be randomly selected from the sample.
  • the average thickness t b [ ⁇ m] of the back layer 14 is obtained from the following formula.
  • t b [ ⁇ m] t T [ ⁇ m] -t B [ ⁇ m]
  • the upper limit of the average thickness (average total thickness) of the magnetic recording medium 10 is preferably 5.6 ⁇ m or less, more preferably 5.0 ⁇ m or less, particularly preferably 4.6 ⁇ m or less, and even more preferably 4.4 ⁇ m or less. ..
  • the lower limit of the average thickness of the magnetic recording medium 10 is not particularly limited, but is, for example, 3.5 ⁇ m or more.
  • the average thickness tT of the magnetic recording medium 10 is obtained as follows. First, a magnetic recording medium 10 having a width of 1/2 inch is prepared, and the magnetic recording medium 10 is cut out to a length of 250 mm to prepare a sample. Next, using a laser holo gauge (LGH-110C) manufactured by Mitutoyo as a measuring device, the thickness of the sample is measured at 5 or more points, and the measured values are simply averaged (arithmetic mean) and averaged. The value tT [ ⁇ m] is calculated. The measurement position shall be randomly selected from the sample.
  • LGH-110C laser holo gauge manufactured by Mitutoyo
  • the residual coercive force Hrp measured in the direction perpendicular to the film surface of the magnetic recording medium 10 using a pulsed magnetic field.
  • the ratio Hrp / Hc is preferably 2.0 or less.
  • the difference between the residual coercive force Hrp and the vertical coercive force Hc is small, and the thermal stability of the magnetic recording medium 10 showing a value in which the ratio Hrp / Hc is close to 1 is high.
  • the difference between the residual coercive force Hrp and the vertical coercive force Hc is large, and the thermal stability in the magnetic recording medium 10 in which the value of the ratio Hrp / Hc is significantly larger than 1 (for example, exceeding 2) is low. ..
  • the ratio Hrp / Hc By setting the ratio Hrp / Hc to 2.0 or less, it is possible to avoid a decrease in thermal stability and to ensure the ease of writing the magnetization signal.
  • the magnetic recording medium 10 By avoiding a decrease in thermal stability, it is possible to prevent the magnetic recording medium 10 from becoming unstable, which is easily affected by the ambient temperature, and improve data storage stability (long-term reliability of the magnetic recording medium 10). Can be improved.
  • the ⁇ -iron oxide of the present disclosure has a high mass magnetization ⁇ s and a high vertical coercive force Hc, which is an original feature of ⁇ -iron oxide, and therefore has high thermal stability even in fine particles. It becomes possible.
  • the vertical coercive force Hc is preferably 2000 Oe or more and 6000 Oe or less, and more preferably 2500 Oe or more and 4500 Oe or less.
  • the mass magnetization ⁇ of the magnetic layer 13 fluctuates due to the influence of ambient heat even during the measurement.
  • the residual coercive force Hrp is measured in an instant by applying a pulsed magnetic field. Therefore, it is considered that the influence of heat from the surroundings is reduced and the residual coercive force Hrp is increased. If the magnetic recording medium has high thermal stability, the decrease in the vertical coercive force Hc due to heat is small, so that the ratio Hrp / Hc is considered to be small. On the other hand, in the case of a magnetic recording medium having low thermal stability, it is considered that the opposite phenomenon occurs, the decrease in the vertical coercive force Hc due to heat becomes large, and the ratio Hrp / Hc becomes large.
  • the vertical coercive force Hc is obtained as follows. First, three magnetic recording media 10 are laminated with double-sided tape, and then punched out with a punch having a diameter of 6.39 mm to prepare a measurement sample. At this time, marking is performed with an arbitrary non-magnetic ink so that the longitudinal direction (traveling direction) of the magnetic recording medium 10 can be recognized. Then, the MH loop of the measurement sample (the entire magnetic recording medium 10) corresponding to the vertical direction (thickness direction) of the magnetic recording medium 10 is measured using the VSM.
  • the coating film that is, the base layer 12, the magnetic layer 13, the back layer 14, and the like is wiped off with acetone, ethanol, or the like so that only the base 11 remains.
  • three of the obtained substrates 11 are laminated with a double-sided tape, and then punched out with a punch having a diameter of 6.39 mm to obtain a sample for background correction (hereinafter, simply a sample for correction).
  • the MH loop of the correction sample (base 11) corresponding to the vertical direction of the base 11 (vertical direction of the magnetic recording medium 10) is measured using the VSM.
  • the measurement conditions are: measurement mode: full loop, maximum magnetic field: 15 kOe, magnetic field step: 40 bits, Time constant of Locking amp: 0.3 sec, Waiting time: 1 sec, MH average number: 20.
  • background correction is performed by subtracting the MH loop of the correction sample (base 11) from the MH loop of the measurement sample (entire magnetic recording medium 10).
  • the MH loop after background correction is obtained.
  • the measurement / analysis program attached to the "VSMP7-15 type" is used for the calculation of this background correction.
  • the vertical coercive force Hc can be obtained from the obtained MH loop after background correction. It is assumed that all the above-mentioned measurements of the MH loop are performed at 25 ° C. Further, it is assumed that "demagnetic field correction" is not performed when the MH loop is measured in the vertical direction of the magnetic recording medium 10. The measurement / analysis program attached to the "VSM-P7-15 type" is used for this calculation.
  • the residual coercive force Hrp is calculated as follows. As the measurement sample, the residual magnetization curve is measured in the direction perpendicular to the film surface using the high-speed response characteristic evaluation device HR-PVSM20 manufactured by Hayama Co., Ltd. for the same sample as the sample used for calculating the vertical coercive force Hc described above. ..
  • a vertical magnetic field of about -3980 kA / m (about -15 kOe) is applied to the entire sample, and the magnetic field is returned to zero to bring it into a residual magnetization state.
  • a magnetic field of about 40.2 kA / m (about 505 Oe) is applied in the opposite direction to return it to zero again, and the residual magnetization amount is measured.
  • the applied magnetic field at this time is a pulse magnetic field having a pulse width of 10 to 8 sec.
  • the measurement magnetic field is up to about 20 kOe.
  • background correction and demagnetic field correction are not particularly performed.
  • the magnitude of the magnetic field applied to the sample is changed by changing the applied voltage.
  • the step voltage is 17.5 V (about 505 Oe when converted to a magnetic field).
  • the main measurement conditions are shown below.
  • Step voltage 17.5V (equivalent to about 505Oe)
  • Maximum voltage 350V (equivalent to 20kOe)
  • Waiting time of lock-in amplifier 10 seconds
  • a residual magnetization curve can be obtained by performing phase correction from the data saved after measurement (Fig. 5). In FIG.
  • the phase information data is also output for each applied magnetic field together with the amount of magnetization (voltage V) at each applied magnetic field.
  • the phase information data of the amount of magnetization (voltage V) measured for a certain magnetic field is a negative value, it is necessary to multiply the measured amount of magnetization (voltage V) by "-1", and the measurement is performed.
  • the value obtained by multiplying the amount of magnetization (voltage V) by "-1” is used to obtain the residual magnetization curve.
  • the process of multiplying the "-1" is the above-mentioned phase correction.
  • phase information data of the amount of magnetization (voltage V) measured for a certain magnetic field is a positive value
  • the amount of magnetization (voltage V) obtained is used as it is to obtain a residual magnetization curve.
  • the amount of magnetization after phase correction (multiplied by "-1") and the measured amount of magnetization (not multiplied by "-1") obtained as described above are plotted against the magnetic field. By doing so, a remanent magnetization curve as shown in the figure is obtained.
  • a coating material for forming an underlayer is prepared by kneading and dispersing a non-magnetic powder, a binder, a lubricant and the like in a solvent.
  • a paint for forming a magnetic layer is prepared by kneading and dispersing a magnetic powder, a binder, a lubricant and the like in a solvent.
  • a coating material for forming a back layer is prepared by kneading and dispersing a binder, a non-magnetic powder and the like in a solvent.
  • the paint for forming the base layer, and the paint for forming the back layer for example, the following solvent, dispersion device, and kneading device can be used.
  • Examples of the solvent used for preparing the above-mentioned paint include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, alcohol solvents such as methanol, ethanol and propanol, methyl acetate, ethyl acetate, butyl acetate and propyl acetate.
  • ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone
  • alcohol solvents such as methanol, ethanol and propanol, methyl acetate, ethyl acetate, butyl acetate and propyl acetate.
  • Ester solvents such as ethyl lactate and ethylene glycol acetate, ether solvents such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran and dioxane, aromatic hydrocarbon solvents such as benzene, toluene and xylene, methylene chloride, ethylene chloride, Examples thereof include halogenated hydrocarbon solvents such as carbon tetrachloride, chloroform and chlorobenzene. These may be used alone or may be mixed appropriately.
  • a continuous twin-screw kneader for example, a continuous twin-screw kneader, a continuous twin-screw kneader that can be diluted in multiple stages, a kneader, a pressure kneader, a roll kneader, or the like can be used.
  • the device is not limited to these devices.
  • disperser used for the above-mentioned paint preparation for example, a roll mill, a ball mill, a horizontal sand mill, a vertical sand mill, a spike mill, a pin mill, a tower mill, a pearl mill (for example, "DCP mill” manufactured by Eirich), a homogenizer, and an ultrasonic mill.
  • Dispersing devices such as a sound wave disperser can be used, but the device is not particularly limited to these devices.
  • the base layer 12 is formed by applying the base layer forming paint to one main surface 11A of the base 11 and drying it.
  • the magnetic layer forming paint is applied onto the base layer 12 and dried to form the magnetic layer 13 on the base layer 12.
  • the magnetic powder is magnetically oriented in the thickness direction of the substrate 11 by, for example, a solenoid coil.
  • the magnetic powder may be magnetically oriented in the traveling direction (longitudinal direction) of the substrate 11 by, for example, a solenoid coil, and then magnetically oriented in the thickness direction of the substrate 11.
  • the degree of vertical orientation of the magnetic powder that is, the square ratio S1
  • the back layer forming paint is applied to the other main surface 11B of the substrate 11 and dried to form the back layer 14. As a result, the magnetic recording medium 10 is obtained.
  • the obtained magnetic recording medium 10 is subjected to calendar processing to smooth the surface 13S of the magnetic layer 13.
  • the magnetic recording medium 10 subjected to the calendar processing is wound into a roll shape, and then the magnetic recording medium 10 is heat-treated in this state to magnetically magnetize a large number of protrusions of the surface 14S of the back layer 14. Transfer to the surface 13S of layer 13. As a result, a large number of dents are formed on the surface 13S of the magnetic layer 13.
  • the temperature of the heat treatment is preferably 50 ° C. or higher and 80 ° C. or lower.
  • the heat treatment temperature is 50 ° C. or higher, good transferability can be obtained.
  • the heat treatment temperature is 80 ° C. or lower, the amount of pores may become too large, and the amount of lubricant on the surface 13S of the magnetic layer 13 may become excessive.
  • the temperature of the heat treatment is the temperature of the atmosphere that holds the magnetic recording medium 10.
  • the heat treatment time is preferably 15 hours or more and 40 hours or less.
  • the heat treatment time is 15 hours or more, good transferability can be obtained.
  • the heat treatment time is 40 hours or less, the decrease in productivity can be suppressed.
  • the range of pressure applied to the magnetic recording medium 10 during the heat treatment is preferably 150 kg / cm or more and 400 kg / cm or less.
  • the magnetic recording medium 10 is cut into a predetermined width (for example, 1/2 inch width). From the above, the target magnetic recording medium 10 can be obtained.
  • the magnetic recording medium 10 of the present embodiment is a tape-shaped member in which the substrate 11, the base layer 12, the magnetic layer 13, and the back layer 14 are laminated in this order, and the following ⁇ 1> to ⁇ 3. > Each configuration requirement is satisfied.
  • the magnetic layer 13 has a magnetic powder containing ⁇ iron oxide.
  • the ratio (Hrp / Hc) of the residual coercive force (Hrp) measured in the vertical direction of the magnetic recording medium 10 using the pulse magnetic field to the vertical coercive force (Hc) in the direction perpendicular to the film surface is 2. It is 0 or less.
  • It has a magnetic layer having a saturation magnetization (Mst) of 4.5 mA or more per unit area.
  • the magnetic recording medium 10 of the present embodiment can realize excellent electromagnetic conversion characteristics and high long-term reliability even when the recording density is increased.
  • the magnetic recording medium 10 satisfies the above-mentioned constitutional requirements, for example, when the magnetic layer 13 has a magnetic powder containing ⁇ -iron oxide to which Co and Zr are added, for example.
  • the magnetic powder containing ⁇ -iron oxide to which Co and Zr are added has a high vertical coercive force Hc and a mass magnetization ⁇ s. Therefore, the magnetic recording medium 10 using such magnetic powder can realize both excellent electromagnetic conversion characteristics and high long-term reliability.
  • Modification example 1 Modification example 1
  • the ⁇ -iron oxide particles 20 (FIG. 4) having the shell portion 22 having a two-layer structure have been illustrated and described, but the magnetic recording medium of the present technology is, for example, as shown in FIG. , ⁇ Iron oxide particles 20A having a shell portion 23 having a single layer structure may be included.
  • the shell portion 23 of the ⁇ iron oxide particles 20A has a structure similar to that of, for example, the first shell portion 22a.
  • the ⁇ -iron oxide particles 20 having the shell portion 22 having the two-layer structure described in the above embodiment are preferable to the ⁇ -iron oxide particles 20A of the first modification.
  • the magnetic recording medium 10 may further include a barrier layer 15 provided on at least one surface of the substrate 11, as shown in FIG. 7, for example.
  • the barrier layer 15 is a layer for suppressing the dimensional change of the substrate 11 according to the environment. For example, as an example of the cause of causing the dimensional change, there is hygroscopicity of the substrate 11, but by providing the barrier layer 15, the rate of moisture invasion into the substrate 11 can be reduced.
  • the barrier layer 15 contains, for example, a metal or a metal oxide. Examples of the metal referred to here include Al, Cu, Co, Mg, Si, Ti, V, Cr, Mn, Fe, Ni, Zn, Ga, Ge, Y, Zr, Mo, Ru, Pd, Ag, Ba.
  • the metal oxide for example, a metal oxide containing one or more of the above metals can be used. More specifically, for example, at least one of Al 2 O 3 , CuO, CoO, SiO 2 , Cr 2 O 3 , TiO 2 , Ta 2 O 5 and Zr O 2 can be used. Further, the barrier layer 15 may contain diamond-like carbon (DLC), diamond, or the like.
  • DLC diamond-like carbon
  • the average thickness of the barrier layer 15 is preferably 20 nm or more and 1000 nm or less, and more preferably 50 nm or more and 1000 nm or less.
  • the average thickness of the barrier layer 15 is obtained in the same manner as the average thickness of the magnetic layer 13. However, the magnification of the TEM image is appropriately adjusted according to the thickness of the barrier layer 15.
  • the saturation magnetization Mst per unit area of the magnetic layer 13, the MH loop, the vertical coercive force Hc, the mass magnetization ⁇ s of the magnetic layer 13, the average thickness of the magnetic layer 13, and the magnetic powder The average particle size, the residual coercive force Hrp, and the positions of the first peak and the second peak in the diffraction pattern measured by in-plane X-ray diffraction (Cu tube) on the magnetic layer 13 are described in the above embodiment. It is a value obtained by the measurement method described.
  • Example 1 The magnetic recording medium as Example 1 was obtained as follows.
  • the paint for forming the magnetic layer was prepared as follows. First, the first composition having the following composition was kneaded with an extruder. Next, the kneaded first composition and the second composition having the following composition were added to a stirring tank provided with a disper, and premixing was performed. Subsequently, sandmill mixing was further performed and filtering was performed to prepare a coating material for forming a magnetic layer.
  • Each component and weight in the first composition is as follows.
  • -Aluminum oxide powder 5 parts by mass ( ⁇ -Al 2 O 3 , average particle size 0.1 ⁇ m) -Carbon black (manufactured by Tokai Carbon Co.
  • -Vinyl chloride resin 3 parts by mass (including solution) (Resin solution: resin content 30% by mass, cyclohexanone 70% by mass)
  • Resin solution resin content 30% by mass, cyclohexanone 70% by mass
  • Polyisocyanate (trade name: Coronate L, manufactured by Tosoh Corporation): 4 parts by mass and stearic acid: 2 parts by mass as fatty acids were added to the paint for forming a magnetic layer prepared as described above.
  • the paint for forming the base layer was prepared as follows. First, the third composition having the following composition was kneaded with an extruder. Next, the kneaded third composition and the fourth composition having the following composition were added to a stirring tank equipped with a disper, and premixing was performed. Subsequently, sand mill mixing was further performed and filter treatment was performed to prepare a coating material for forming a base layer.
  • Each component and weight in the third composition is as follows.
  • -Needle iron oxide powder ⁇ -Fe 2 O 3 , average major axis length 0.15 ⁇ m
  • resin solution resin content 30% by mass, cyclohexanone 70% by mass
  • -Carbon black average particle size 20 nm
  • Each component and weight in the fourth composition is as follows.
  • -Polyurethane resin UR8200 manufactured by Toyo Spinning Co., Ltd.
  • 18.5 parts by mass-n-butyl stearate as fatty acid ester 2 parts by mass-Methyl ethyl ketone: 108.2 parts by mass-Toluene: 108.2 parts by mass-Cyclohexanone: 18. 5 parts by mass
  • Polyisocyanate (trade name: Coronate L, manufactured by Tosoh Corporation): 4 parts by mass and stearic acid: 2 parts by mass as fatty acids were added to the base layer forming paint prepared as described above.
  • the paint for forming the back layer was prepared as follows. The following raw materials were mixed in a stirring tank equipped with a disper and filtered to prepare a coating material for forming a back layer.
  • -Small particle size carbon black powder (average particle size (D50) 20 nm): 90 parts by mass-Large particle size carbon black powder (average particle size (D50) 270 nm): 10 parts by mass-Polyester polyurethane (Tosoh Co., Ltd.) Made by the company, trade name: N-2304): 100 parts by mass, methyl ethyl ketone: 500 parts by mass, toluene: 400 parts by mass, cyclohexanone: 100 parts by mass
  • the non-magnetic support was averaged on one main surface of a long polyester film having an average thickness of 4.0 ⁇ m after the calendar. It was formed as follows so as to form a base layer having a thickness of 0.6 ⁇ m and a magnetic layer having an average thickness of 80 nm.
  • a base layer forming paint was applied on one main surface of the polyester film and dried to form a base layer.
  • the magnetic layer was formed by applying a paint for forming a magnetic layer on the base layer and drying it. When the paint for forming the magnetic layer was dried, the magnetic powder was magnetically oriented in the thickness direction of the film by a solenoid coil.
  • drying conditions drying temperature and drying time
  • Hc in the thickness direction (vertical direction) of the magnetic recording medium was set to the value shown in Table 1.
  • a paint for forming a back layer was applied onto the other main surface of the polyester film and dried to form a back layer having an average thickness of 0.3 ⁇ m.
  • ⁇ Calendar process and transfer process> Subsequently, a calendar process was performed to smooth the surface of the magnetic layer. Next, a magnetic recording medium having a smoothed surface of the magnetic layer was wound into a roll, and then the magnetic recording medium was heat-treated at 60 ° C. for 10 hours in that state. Then, after rewinding the magnetic recording medium into a roll shape so that the end located on the inner peripheral side is located on the outer peripheral side, the magnetic recording medium is heated at 60 ° C. for 10 hours in that state. The process was performed again. As a result, many protrusions on the surface of the back layer were transferred to the surface of the magnetic layer, and many dents were formed on the surface of the magnetic layer.
  • ⁇ Cutting process> The magnetic recording medium obtained as described above was cut to a width of 1/2 inch (12.65 mm). As a result, the desired long magnetic recording medium (average thickness 5.6 ⁇ m) was obtained.
  • the saturation magnetization Mst per unit area in the magnetic layer was 6.1 mA, and the ratio Hrp / Hc was 1.67.
  • Example 4 In the step of preparing the paint for forming the magnetic layer, the average particle size of the ⁇ iron oxide particles was set to 15.5 nm. Further, in the coating step, the drying conditions were adjusted, and the coercive force Hc in the thickness direction (vertical direction) of the magnetic recording medium and the residual coercive force Hrp measured using the pulsed magnetic field were set to the values shown in Table 1, respectively. I set it. Further, in the coating step, the average thickness of the magnetic layer was set to 60 nm. Except for these, a magnetic recording medium as Example 4 was obtained in the same manner as in Example 1 above. In the magnetic recording medium as Example 4 thus obtained, the saturation magnetization Mst per unit area in the magnetic layer was 4.5 mA.
  • Example 11 In the step of preparing the paint for forming the magnetic layer, the average particle size of the ⁇ iron oxide particles was set to 16.2 nm. Further, in the coating step, the drying conditions were adjusted, and the coercive force Hc in the thickness direction (vertical direction) of the magnetic recording medium and the residual coercive force Hrp measured using the pulsed magnetic field were set to the values shown in Table 1, respectively. I set it. Except for these, a magnetic recording medium as Example 11 was obtained in the same manner as in Example 1 above. In the magnetic recording medium as Example 11 thus obtained, the saturation magnetization Mst per unit area in the magnetic layer was 6.1 mA.
  • SNR magnetic conversion characteristic
  • the SNR (electromagnetic conversion characteristic) of the magnetic recording medium in a 25 ° C environment was measured using a 1/2 inch tape traveling device (manufactured by Mountain Engineering II, MTS Transport) equipped with a recording / playback head and a recording / playback amplifier. ..
  • a ring head having a gap length of 0.2 ⁇ m was used as the recording head, and a GMR head having a distance between shields of 0.1 ⁇ m was used as the playback head.
  • the relative speed was 6 m / s
  • the recording clock frequency was 160 MHz
  • the recording track width was 2.0 ⁇ m.
  • the SNR was calculated based on the method described in the following document. The results are shown in Table 1 as relative values with the SNR of Comparative Example 3 as 0 dB. Y.Okazaki: “An Error Rate Emulation System.”, IEEE Trans. Man., 31, pp.3093-3095 (1995)
  • THT Tepe Head Tester
  • TS1140 IBM tape drive
  • a magnetic tape as a magnetic recording medium was cut to a length of 90 cm, formed into a ring shape so that the recording layer of the magnetic tape was on the back side, and then both ends of the magnetic tape were joined to each other with an adhesive tape on the back surface of the magnetic tape.
  • a silver tape for detecting the tape circulation position was attached adjacent to the joint. The ring-shaped magnetic tape was attached to the THT and then orbited at a speed of 2 m / sec.
  • the above-mentioned measurement flow was performed four times using the same magnetic tape, and the Y (t) values obtained by each measurement were averaged for the same elapsed time t to obtain a sequence of Yave (t).
  • the obtained Yave (t) was plotted on the Y-axis and the elapsed time t was plotted on the X-axis, and an approximate curve was created from this graph using logarithmic approximation.
  • the signal attenuation after 10 years was calculated using the obtained approximate curve.
  • Table 1 summarizes the configurations and evaluation results of the magnetic recording media in each Example and each Comparative Example.
  • the first peak at 32.9 ° and the second peak at 36.6 ° were expressed in the diffraction pattern by in-plane X-ray diffraction (Cu tube). It has a magnetic layer having a ratio of Hrp / Hc of 2.0 or less, containing iron oxide, and a saturation magnetization Mst of 4.5 mA or more per unit area. Therefore, in Examples 1 to 11, good results were obtained in both SNR and signal attenuation.
  • Example 9 extremely good results were obtained in both SNR and signal attenuation.
  • Example 9 in addition to having a high saturation magnetization Mst per unit area, the residual coercive force Hrp measured using a pulsed magnetic field is also suppressed to a low level. Therefore, it is considered that a good SNR is obtained because the recording magnetic field can be easily written to the magnetic layer 13 and a steep magnetization reversal can be formed in the magnetic layer 13.
  • Example 2 since the magnetic particles were made smaller, a better SNR was obtained. Further, in Example 3, since relatively large magnetic particles were used, good results were obtained in terms of signal attenuation.
  • the configurations, methods, processes, shapes, materials, numerical values, etc. given in the above-described embodiments and modifications thereof are merely examples, and different configurations, methods, processes, shapes, materials, and numerical values are required as necessary.
  • Etc. may be used.
  • the magnetic recording medium of the present disclosure may include components other than the substrate, the base layer, the magnetic layer, the back layer, and the barrier layer.
  • the chemical formulas of the compounds and the like are typical, and the general names of the same compounds are not limited to the stated valences and the like.
  • the upper limit value or the lower limit value of the numerical range of one step may be replaced with the upper limit value or the lower limit value of the numerical range of another step.
  • the materials exemplified in the present specification may be used alone or in combination of two or more.
  • a magnetic recording medium having a magnetic layer and a substrate The magnetic layer has a magnetic powder containing ⁇ iron oxide and has The ratio (Hrp / Hc) of the residual coercive force (Hrp) measured in the vertical direction of the magnetic recording medium to the vertical coercive force (Hc) of the magnetic recording medium is 2.0 or less.
  • Mst saturation magnetization
  • the vertical coercive force is 2000 Oe or more and 6000 Oe or less.
  • the magnetization curve (MH loop) representing the relationship between the magnetization and the magnetic field in the magnetic layer is closed in the range of ⁇ 15 kOe or more and + 15 kOe or less.
  • Magnetic recording medium (10) The magnetic recording medium according to (8) above, wherein the molar ratio of cobalt when the combined atomic% of iron (Fe) and cobalt in the ⁇ -iron oxide is 100 is 3 atomic% or more and 20 atomic% or less.
  • (11) The magnetic recording medium according to (8) above, wherein the molar ratio of zirconium when the combined atomic% of iron (Fe) and zirconium in the ⁇ -iron oxide is 100 is 1 atomic% or more and 8 atomic% or less.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Magnetic Record Carriers (AREA)
  • Manufacturing Of Magnetic Record Carriers (AREA)
PCT/JP2021/001829 2020-01-21 2021-01-20 磁気記録媒体 Ceased WO2021149716A1 (ja)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US17/789,685 US12614565B2 (en) 2020-01-21 2021-01-20 Magnetic recording medium
JP2021572760A JP7590738B2 (ja) 2020-01-21 2021-01-20 磁気記録媒体
DE112021000640.1T DE112021000640T5 (de) 2020-01-21 2021-01-20 Magnetisches aufzeichnungsmedium

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2020-007832 2020-01-21
JP2020007832 2020-01-21

Publications (1)

Publication Number Publication Date
WO2021149716A1 true WO2021149716A1 (ja) 2021-07-29

Family

ID=76991767

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2021/001829 Ceased WO2021149716A1 (ja) 2020-01-21 2021-01-20 磁気記録媒体

Country Status (4)

Country Link
US (1) US12614565B2 (https=)
JP (1) JP7590738B2 (https=)
DE (1) DE112021000640T5 (https=)
WO (1) WO2021149716A1 (https=)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN121247891B (zh) * 2025-12-03 2026-03-20 山西潞安太行润滑科技股份有限公司 一种用于联轴器润滑脂的Fe2O3抗磨减摩剂及其制备与应用

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008189996A (ja) * 2007-02-05 2008-08-21 Hitachi Metals Ltd Ｃｏ−Ｆｅ系合金スパッタリングターゲット材およびその製造方法
JP2019023950A (ja) * 2017-07-24 2019-02-14 マクセルホールディングス株式会社 磁気記録媒体
JP2019175532A (ja) * 2018-03-29 2019-10-10 富士フイルム株式会社 磁気記録媒体、イプシロン型酸化鉄系化合物の粒子の製造方法、及び磁気記録媒体の製造方法
JP6624332B1 (ja) * 2019-08-21 2019-12-25 ソニー株式会社 磁気記録媒体およびカートリッジ

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007114394A1 (ja) * 2006-03-30 2007-10-11 Fujifilm Corporation 磁気記録媒体、リニア磁気記録再生システムおよび磁気記録再生方法
JP6649234B2 (ja) * 2016-11-30 2020-02-19 富士フイルム株式会社 ε−酸化鉄型強磁性粉末および磁気記録媒体
WO2018203468A1 (ja) 2017-05-01 2018-11-08 ソニー株式会社 磁気記録媒体
US10854233B2 (en) * 2017-09-29 2020-12-01 Fujifilm Corporation Magnetic recording medium having characterized magnetic layer and magnetic recording and reproducing device
JP2020007832A (ja) 2018-07-11 2020-01-16 パナソニックＩｐマネジメント株式会社 衛生洗浄装置

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008189996A (ja) * 2007-02-05 2008-08-21 Hitachi Metals Ltd Ｃｏ−Ｆｅ系合金スパッタリングターゲット材およびその製造方法
JP2019023950A (ja) * 2017-07-24 2019-02-14 マクセルホールディングス株式会社 磁気記録媒体
JP2019175532A (ja) * 2018-03-29 2019-10-10 富士フイルム株式会社 磁気記録媒体、イプシロン型酸化鉄系化合物の粒子の製造方法、及び磁気記録媒体の製造方法
JP6624332B1 (ja) * 2019-08-21 2019-12-25 ソニー株式会社 磁気記録媒体およびカートリッジ

Also Published As

Publication number Publication date
US12614565B2 (en) 2026-04-28
DE112021000640T5 (de) 2022-11-17
JP7590738B2 (ja) 2024-11-27
JPWO2021149716A1 (https=) 2021-07-29
US20230075546A1 (en) 2023-03-09

Similar Documents

Publication Publication Date Title
JP6927405B2 (ja) 磁気記録媒体
JP7184065B2 (ja) 磁気記録テープとその製造方法、磁気記録テープカートリッジ
JP7147751B2 (ja) 磁気記録媒体
JP7200986B2 (ja) 磁気記録テープとその製造方法、磁気記録テープカートリッジ
US11527260B2 (en) Magnetic recording medium, magnetic recording/reproducing device, and magnetic recording medium cartridge
WO2021033331A1 (ja) 磁気記録媒体、磁気記録再生装置および磁気記録媒体カートリッジ
WO2021033330A1 (ja) 磁気記録媒体、磁気記録再生装置および磁気記録媒体カートリッジ
US11830532B2 (en) Magnetic recording medium including magnetic layer having magnetic powder, magnetic recording/reproducing device, and magnetic recording medium cartridge
JP7063411B2 (ja) 磁気記録媒体、磁気記録再生装置および磁気記録媒体カートリッジ
WO2021033333A1 (ja) 磁気記録媒体、磁気記録再生装置および磁気記録媒体カートリッジ
JP6838633B1 (ja) 磁気記録媒体、磁気記録再生装置および磁気記録媒体カートリッジ
JP7590738B2 (ja) 磁気記録媒体
JP2021034101A (ja) 磁気記録媒体、磁気記録再生装置および磁気記録媒体カートリッジ
JP7605353B2 (ja) 磁気記録媒体、磁気記録再生装置および磁気記録媒体カートリッジ
JP7359168B2 (ja) 磁気記録媒体、磁気記録再生装置および磁気記録媒体カートリッジ
JP6725051B1 (ja) 磁気記録媒体、磁気記録再生装置および磁気記録媒体カートリッジ
JP7563148B2 (ja) 磁気記録媒体、磁気記録再生装置および磁気記録媒体カートリッジ
JP6725053B1 (ja) 磁気記録媒体
JP2021034104A (ja) 磁気記録媒体、磁気記録再生装置および磁気記録媒体カートリッジ
JP2021034105A (ja) 磁気記録媒体、磁気記録再生装置および磁気記録媒体カートリッジ

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 21744529

Country of ref document: EP

Kind code of ref document: A1

ENP Entry into the national phase

Ref document number: 2021572760

Country of ref document: JP

Kind code of ref document: A

122 Ep: pct application non-entry in european phase

Ref document number: 21744529

Country of ref document: EP

Kind code of ref document: A1