WO2022209935A1 - 磁気記録媒体 - Google Patents

磁気記録媒体 Download PDF

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Publication number
WO2022209935A1
WO2022209935A1 PCT/JP2022/012167 JP2022012167W WO2022209935A1 WO 2022209935 A1 WO2022209935 A1 WO 2022209935A1 JP 2022012167 W JP2022012167 W JP 2022012167W WO 2022209935 A1 WO2022209935 A1 WO 2022209935A1
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WO
WIPO (PCT)
Prior art keywords
magnetic
recording medium
less
magnetic recording
layer
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Ceased
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PCT/JP2022/012167
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English (en)
French (fr)
Japanese (ja)
Inventor
颯吾 及川
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Sony Group Corp
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Sony Group Corp
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Priority to US18/284,215 priority Critical patent/US12243571B2/en
Priority to JP2023510930A priority patent/JP7782549B2/ja
Publication of WO2022209935A1 publication Critical patent/WO2022209935A1/ja
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • 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
    • G11B5/74—Record carriers characterised by the form, e.g. sheet shaped to wrap around a drum
    • G11B5/78—Tape carriers
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B23/00—Record carriers not specific to the method of recording or reproducing; Accessories, e.g. containers, specially adapted for co-operation with the recording or reproducing apparatus ; Intermediate mediums; Apparatus or processes specially adapted for their manufacture
    • G11B23/02—Containers; Storing means both adapted to cooperate with the recording or reproducing means
    • G11B23/04—Magazines; Cassettes for webs or filaments
    • G11B23/08—Magazines; Cassettes for webs or filaments for housing webs or filaments having two distinct ends
    • G11B23/107—Magazines; Cassettes for webs or filaments for housing webs or filaments having two distinct ends using one reel or core, one end of the record carrier coming out of the magazine or cassette
    • 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
    • G11B5/008—Recording on, or reproducing or erasing from, magnetic tapes, sheets, e.g. cards, or wires
    • G11B5/00813—Recording on, or reproducing or erasing from, magnetic tapes, sheets, e.g. cards, or wires magnetic tapes
    • 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
    • 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
    • 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
    • G11B5/70678—Ferrites
    • 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
    • G11B5/73—Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer
    • 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
    • G11B5/84—Processes or apparatus specially adapted for manufacturing record carriers
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B2220/00—Record carriers by type
    • G11B2220/60—Solid state media
    • G11B2220/65—Solid state media wherein solid state memory is used for storing indexing information or metadata
    • G11B2220/652—Solid state media wherein solid state memory is used for storing indexing information or metadata said memory being attached to the recording medium
    • G11B2220/655—Memory in cassette [MIC]

Definitions

  • This technology relates to magnetic recording media.
  • Magnetic recording media are often used as media for recording large amounts of data.
  • Patent Document 1 a low coercive force layer containing magnetic powder and a binder and having a coercive force measured in the longitudinal direction of 15.9 kA/m (200 oersteds) or less on a nonmagnetic support, magnetic powder and A magnetic layer for signal recording containing a binder is formed in this order, and the magnetic layer contains iron or a transition element mainly composed of iron and nitrogen as essential constituent elements as magnetic powder.
  • essentially spherical or ellipsoidal iron nitride-based magnetic powder having an average particle size of ⁇ 50 nm and an average axial ratio of 1 to 2, substantially vertically oriented, and a magnetic layer thickness of 300 nm or less , a magnetic recording medium characterized in that the average surface roughness Ra of the magnetic layer is 1.0 to 3.2 nm.
  • the output of the magnetic recording medium decreases as the recording wavelength becomes shorter. However, even when the recording wavelength is short, it is desirable to obtain an output equivalent to that obtained when the recording wavelength is long. In order to increase the output during short-wavelength recording and approach the output during long-wavelength recording, it is desirable that the resolution of the magnetic recording medium is high. Therefore, the main object of the present technology is to provide a magnetic recording medium exhibiting high resolution.
  • This technology including a magnetic layer and an underlayer
  • a core level difference Rk is 5.5 nm or less
  • the average thickness of the underlayer is 1.50 ⁇ m or less
  • a tape-shaped magnetic recording medium is provided.
  • a height of the bearing curve at an area ratio of 10.00% may be 2.80 nm or less.
  • a height of the bearing curve at an area ratio of 20.00% may be 1.70 nm or less.
  • a height of the bearing curve at an area ratio of 30.00% may be 1.00 nm or less.
  • a height of the bearing curve at an area ratio of 40.00% may be 0.50 nm or less.
  • the core portion level difference Rk may be 5.0 nm or less.
  • the average thickness of the underlayer may be 1.35 ⁇ m or less.
  • the average thickness of the underlayer may be 0.80 ⁇ m or less.
  • the average thickness of the magnetic layer may be 90 nm or less.
  • the average thickness of the magnetic recording medium may be 5.90 ⁇ m or less.
  • the average thickness of the magnetic recording medium may be 5.30 ⁇ m or less.
  • a power spectral density of the magnetic layer up to a spatial wavelength of 5 ⁇ m may be 3.6 nm 3 or less.
  • the magnetic layer may contain magnetic powder, and the magnetic powder may contain hexagonal ferrite, ⁇ -iron oxide, or Co-containing spinel ferrite.
  • this technology the tape-shaped magnetic recording medium; a communication unit that communicates with the recording/reproducing device; a storage unit; A control unit that stores information received from the recording/reproducing device via the communication unit in the storage unit, reads information from the storage unit in response to a request from the recording/reproducing device, and transmits the information to the recording/reproducing device via the communication unit. and
  • the information includes adjustment information for adjusting the tension applied in the longitudinal direction of the magnetic recording medium, We also offer tape cartridges.
  • FIG. 1 is a schematic diagram showing a part of a cross section of a magnetic recording medium;
  • FIG. 2A is a schematic diagram of the layout of the data and servo bands.
  • FIG. 2B is a schematic diagram of an enlarged data band. It is an example of a TEM photograph of a magnetic layer.
  • FIG. 2 is a schematic diagram showing the configuration of a cross section of magnetic particles;
  • FIG. 3 is an exploded perspective view showing an example of the configuration of a cartridge
  • 4 is a block diagram showing an example of the configuration of a cartridge memory
  • FIG. 3 is a schematic diagram showing a part of a cross section of a magnetic recording medium of a modified example
  • the output of magnetic recording media decreases as the recording wavelength becomes shorter. However, even when the recording wavelength is short, it is desirable to obtain an output equivalent to that obtained when the recording wavelength is long. For this purpose, it is necessary to increase the output during short-wavelength recording so as to approach the output during long-wavelength recording. In order to increase the output during short-wavelength recording, it is considered effective to increase the resolution, which is one of the electromagnetic conversion characteristics of the magnetic recording medium.
  • the inventors have studied techniques for increasing the resolution of magnetic recording media. As a result, the inventor discovered that there is a high correlation between the resolution and the core level difference Rk, which will be described later. The inventors also discovered that thinning the underlayer contributes to the resolution improvement. As a result of further studies, the inventors of the present invention have found that a magnetic recording medium in which the core portion level difference Rk is a specific numerical value or less and the average thickness of the underlayer is a specific numerical value or less provides a high resolution. found to show. That is, the magnetic recording medium of the present technology includes a magnetic layer and an underlayer. The difference Rk is 5.5 nm or less, and the average thickness of the underlying layer is 1.50 ⁇ m or less.
  • the magnetic recording medium of the present technology has a core portion level difference Rk of 5.5 nm or less in a bearing curve created based on height data of the magnetic layer side surface obtained using an atomic force microscope, It is preferably 5.2 nm or less, more preferably 5.0 nm or less, and even more preferably 4.7 nm or less.
  • the resolution can be improved by keeping the core portion level difference Rk within this numerical range.
  • the magnetic recording media of this technology exhibit high resolution. This is probably because the core level difference Rk of the magnetic recording medium of the present technology is equal to or less than a specific numerical value, so that the smooth portion on the magnetic layer side surface can be increased.
  • the core portion level difference Rk is a value calculated using a bearing curve created based on height data of the magnetic layer side surface obtained using an atomic force microscope. It is considered that the property of the side surface is reflected. Specifically, it is considered that the larger the core level difference Rk, the more irregularities are present on the magnetic layer side surface, and the smaller the core level difference Rk, the greater the smoothness of the magnetic layer side surface.
  • the spacing (distance between the magnetic recording medium and the magnetic head) tends to decrease as the surface on the magnetic layer side becomes smoother. Therefore, it is considered that the magnetic recording medium of the present technology in which the core portion level difference Rk is equal to or less than a specific numerical value can increase the smooth portion on the surface on the magnetic layer side, thereby reducing the spacing. It is believed that this contributes to the improvement in resolution in the magnetic recording medium of the present technology.
  • the width of the magnetic recording medium of the present technology can be, for example, 5 mm to 30 mm, particularly 7 mm to 25 mm, more particularly 10 mm to 20 mm, still more particularly 11 mm to 19 mm.
  • the length of the tape-shaped magnetic recording medium of the present technology can be, for example, 500m to 1500m.
  • the tape width according to the LTO8 standard is 12.65 mm and the length is 960 m.
  • the magnetic recording medium of this technology is tape-shaped, and can be, for example, a long magnetic recording tape.
  • the tape-shaped magnetic recording medium of the present technology may be housed, for example, in a magnetic recording cartridge. More specifically, it may be accommodated in the cartridge while being wound around a reel in the magnetic recording cartridge.
  • the magnetic recording medium of the present technology may include a magnetic layer, an underlayer, a base layer, and a back layer. These four layers may be laminated in this order.
  • the magnetic recording medium of the present technology may contain other layers in addition to these layers.
  • the other layer may be appropriately selected according to the type of magnetic recording medium.
  • the magnetic recording medium of the present technology can be, for example, a coating type magnetic recording medium. Regarding the coating type magnetic recording medium, the following 2. will be described in more detail.
  • the magnetic recording medium 10 includes an elongated base layer 11, an underlayer 12 provided on one main surface of the base layer 11, a magnetic layer 13 provided on the underlayer 12, and the base layer 11. and a back layer 14 provided on the other main surface.
  • the back layer 14 is provided as necessary, and may be omitted.
  • the magnetic recording medium 10 has a long tape shape and runs in the longitudinal direction during recording and reproduction.
  • the surface of the magnetic layer 13 is the surface on which the magnetic head runs.
  • the magnetic recording medium 10 is preferably used in a recording/reproducing apparatus having a ring-shaped head as a recording head.
  • the “perpendicular direction” means a direction perpendicular to the surface of the magnetic recording medium 10 (thickness direction of the magnetic recording medium 10)
  • the “longitudinal direction” means the magnetic recording medium 10. means the longitudinal direction (running direction) of
  • the base layer 11 is a nonmagnetic support that supports the underlayer 12 and the magnetic layer 13 .
  • the base layer 11 has a long film shape.
  • the average thickness of the base layer 11 is preferably 4.2 ⁇ m or less, more preferably 3.8 ⁇ m or less, still more preferably 3.4 ⁇ m or less.
  • the recording capacity that can be recorded in one data cartridge can be made higher than that of a general magnetic recording medium.
  • the average thickness of the base layer 11 is preferably 3.0 ⁇ m or more, more preferably 3.2 ⁇ m or more. When the average thickness of the base layer 11 is 3.0 ⁇ m or more, a decrease in the strength of the base layer 11 can be suppressed.
  • the average thickness of the base layer 11 is obtained as follows. First, a magnetic recording medium 10 having a width of 1/2 inch is prepared and cut into a length of 250 mm to prepare a sample. Subsequently, the layers of the sample other than the base layer 11 (that is, the underlayer 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 Mitutoyo laser hologram (LGH-110C) as a measuring device, the thickness of the sample (base layer 11) is measured at five or more points, and the measured values are simply averaged (arithmetic average ) to calculate the average thickness of the base layer 11 . It is assumed that the measurement position is randomly selected from the sample.
  • a Mitutoyo laser hologram LGH-110C
  • the base layer 11 contains, for example, at least one of polyesters, polyolefins, cellulose derivatives, vinyl resins, and other polymer resins.
  • the base layer 11 contains two or more of the above materials, the two or more materials may be mixed, copolymerized, or laminated.
  • Polyesters 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.
  • Polyolefins 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).
  • Vinyl-based resins include, for example, at least one of PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride).
  • PA polyamide, nylon
  • aromatic PA aromatic polyamide, aramid
  • PI polyimide
  • aromatic PI aromatic polyimide
  • PAI polyamideimide
  • aromatic PAI aromatic polyamideimide
  • PBO polybenzoxazole, e.g. Zylon®
  • polyether PEK (polyetherketone), polyetherester
  • PES polyethersulfone
  • PEI polyetherimide
  • At least one of PSF polysulfone
  • PPS polyphenylene sulfide
  • PC polycarbonate
  • PAR polyarylate
  • PU polyurethane
  • the base layer 11 contains, for example, polyester as a main component.
  • the polyester is, for example, PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PBN (polybutylene naphthalate), PCT (polycyclohexylene dimethylene terephthalate), PEB (polyethylene-p- oxybenzoate), and polyethylene bisphenoxycarboxylate, or a mixture of two or more.
  • the term "main component” means a component with the highest content ratio among the components constituting the base layer.
  • the fact that the main component of the base layer 11 is polyester means that the content of the polyester in the base layer 11 is, for example, 50% by mass or more, 60% by mass or more, 70% by mass or more, or 80% by mass with respect to the mass of the base layer 11. % or more, 90 mass % or more, 95 mass % or more, or 98 mass % or more, or it may mean that the base layer 11 is composed only of polyester.
  • the base layer 11 may contain, in addition to polyester, resins other than polyester described below.
  • the base layer 11 may be formed from PET or PEN.
  • the magnetic layer 13 is a recording layer for recording signals.
  • the magnetic layer 13 contains, for example, magnetic powder and a binder.
  • the magnetic layer 13 may further contain at least one additive selected from lubricants, antistatic agents, abrasives, hardeners, rust inhibitors, non-magnetic reinforcing particles, and the like, if necessary.
  • the magnetic layer 13 preferably has a plurality of servo bands SB and a plurality of data bands DB in advance, as shown in FIG. 2A.
  • a plurality of servo bands SB are provided at regular intervals in the width direction of the magnetic recording medium 10 .
  • a data band DB is provided between adjacent servo bands SB.
  • a servo signal for tracking control of the magnetic head is written in advance in the servo band SB.
  • User data is recorded in the data band DB.
  • the ratio R S of the total area S SB of the servo bands SB to the surface area S of the magnetic layer 13 is preferably 0.8% or more from the viewpoint of ensuring five or more servo tracks.
  • the ratio R S of the total area S SB of the servo band SB to the area S of the entire surface of the magnetic layer 13 is obtained as follows.
  • the magnetic recording medium 10 is developed using a ferricolloid developer (manufactured by Sigma High Chemical Co., Ltd., Sigmamarker Q), and then the developed magnetic recording medium 10 is observed with an optical microscope. and the number of servo bands SB.
  • the number of servo bands SB is preferably 5 or more, more preferably 5+4n (where n is a positive integer) or more, and even more preferably 9+4n or more.
  • n is a positive integer
  • the number of servo bands SB is not particularly limited, but is, for example, 33 or less.
  • the number of servo bands SB can be confirmed as follows. First, the surface of the magnetic layer 13 is observed using a magnetic force microscope (MFM) to obtain an MFM image. Next, the MFM image is used to count the number of servo bands SB.
  • MFM magnetic force microscope
  • the servo bandwidth W SB is preferably 95 ⁇ m or less, more preferably 60 ⁇ m or less, and still more preferably 30 ⁇ m or less from the viewpoint of ensuring a high recording capacity.
  • the servo bandwidth W SB is preferably greater than or equal to 10 ⁇ m. Manufacturing a recording head capable of reading servo signals with a servo bandwidth W SB of less than 10 ⁇ m can be challenging.
  • the width of the servo bandwidth W SB is obtained as follows. First, the surface of the magnetic layer 13 is observed using a magnetic force microscope (MFM) to obtain an MFM image. Next, the width of the servo bandwidth W SB is measured using the MFM image.
  • MFM magnetic force microscope
  • the magnetic layer 13 is configured so that a plurality of data tracks Tk can be formed in the data band DB, as shown in FIG. 2B.
  • the data track width W is preferably 2.0 ⁇ m or less, more preferably 1.5 ⁇ m or less, and still more preferably 1.0 ⁇ m or less from the viewpoint of ensuring a high recording capacity.
  • the data track width W is preferably 0.02 ⁇ m or more.
  • the data track width W is obtained as follows.
  • the data recording pattern of the data band portion of the magnetic layer 13 on which data is recorded over the entire surface is observed using a magnetic force microscope (MFM) to obtain an MFM image.
  • MFM magnetic force microscope
  • Dimension3100 manufactured by Digital Instruments and its analysis software are used as MFM.
  • Measurements by MFM are performed on three 10 ⁇ m ⁇ 10 ⁇ m measurement areas at different locations, ie three MFM images are obtained.
  • the track width is measured at 10 points from the three obtained MFM images, and the average value (which is a simple average) is obtained.
  • the average value is the data track width W.
  • FIG. The measurement conditions for the above MFM are sweep speed: 1 Hz, chip used: MFMR-20, lift height: 20 nm, correction: Flatten order 3.
  • the minimum value L of the distance between magnetization reversals and the data track width W are preferably W/L ⁇ 200, more preferably W/L ⁇ 60, even more preferably W/L ⁇ 45, particularly preferably W Data can be recorded such that /L ⁇ 30. If the minimum value L of the distance between magnetization reversals is a constant value and the minimum value L of the distance between magnetization reversals and the track width W satisfy W/L>200 (that is, if the track width W is large), the track recording density increases. Therefore, there is a possibility that a sufficient recording capacity cannot be secured.
  • W/L is in the range of W/L ⁇ 60 as described above in order to suppress the deterioration of the SNR while securing the recording capacity.
  • W/L is not limited to the above range, and may be W/L ⁇ 23 or W/L ⁇ 13.
  • the lower limit of W/L is not particularly limited, it is, for example, 1 ⁇ W/L.
  • the minimum value L of the distance between magnetization reversals is preferably 55 nm or less, more preferably 53 nm or less, even more preferably 52 nm or less, 50 nm or less, 48 nm or less, or 44 nm or less, from the viewpoint of ensuring high recording capacity. , particularly preferably 40 nm or less, so that data can be recorded.
  • the lower limit of the minimum value L of the distance between magnetization reversals is preferably 20 nm or more. The minimum value L of the distance between magnetization reversals is taken into account by the magnetic grain size.
  • the minimum value L of the distance between magnetization reversals is obtained as follows.
  • the data recording pattern of the data band portion of the magnetic layer 13 on which data is recorded over the entire surface is observed using a magnetic force microscope (MFM) to obtain an MFM image.
  • MFM magnetic force microscope
  • Dimension3100 manufactured by Digital Instruments and its analysis software are used as MFM.
  • Measurements by MFM are performed on three 2 ⁇ m ⁇ 2 ⁇ m measurement areas at different locations, ie three MFM images are obtained. 50 bit distances are measured from the two-dimensional unevenness chart of the recording pattern of the obtained MFM image.
  • the bit-to-bit distance is measured using analysis software attached to Dimension3100.
  • the minimum value L of the distance between magnetization reversals is defined as the greatest common divisor of the 50 measured inter-bit distances.
  • the measurement conditions are sweep speed: 1 Hz, chip used: MFMR-20, lift height: 20 nm, correction: Flatten order 3.
  • the average thickness t m 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 60 nm or less.
  • the average thickness of the magnetic layer 13 is 90 nm or less, magnetization can be uniformly recorded in the thickness direction of the magnetic layer 13 when a ring-shaped head is used as a recording head, thereby improving electromagnetic conversion characteristics (for example, SNR). be able to.
  • the average thickness tm of the magnetic layer 13 is preferably 30 nm or more, more preferably 35 nm or more.
  • an output can be secured when an MR head is used as a reproducing head, so that the electromagnetic conversion characteristics (for example, SNR) can be improved.
  • the numerical range of the average thickness tm of the magnetic layer 13 may be defined by either the above upper limit value or any of the above lower limit values, preferably 30 nm ⁇ t m ⁇ 90 nm, and 35 nm ⁇ t m ⁇ 80 nm . , 35 nm ⁇ t m ⁇ 70 nm, or 35 nm ⁇ t m ⁇ 60 nm.
  • the average thickness tm of the magnetic layer 13 is obtained, for example, as follows.
  • the magnetic recording medium 10 is processed by an FIB (Focused Ion Beam) method or the like to be thinned.
  • FIB Flucused Ion Beam
  • a carbon film and a tungsten thin film are formed as protective films as a pretreatment for observing a cross-sectional TEM image, which will be 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 vapor deposition, and the tungsten thin film is further formed on the magnetic layer side surface by vapor deposition or sputtering.
  • the thinning is performed along the length direction (longitudinal direction) of the magnetic recording medium 10 . That is, the thinning of the magnetic recording medium 10 forms a cross section parallel to both the longitudinal direction and the thickness direction.
  • TEM transmission electron microscope
  • the thickness of the magnetic layer 13 is measured at at least 10 positions 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 t m [nm] of the magnetic layer 13 .
  • the position where the above measurement is performed shall be randomly selected from the test piece.
  • Examples of magnetic particles forming the magnetic powder contained in the magnetic layer 13 include hexagonal ferrite, epsilon-type iron oxide ( ⁇ -iron oxide), Co-containing spinel ferrite, gamma hematite, magnetite, chromium dioxide, cobalt-coated iron oxide, and metal oxide. (metal), etc., but are not limited to these.
  • the magnetic powder may be one of these, or may be a combination of two or more.
  • the magnetic powder may comprise hexagonal ferrite, ⁇ -iron oxide, or Co-containing spinel ferrite.
  • the magnetic powder is hexagonal ferrite.
  • the hexagonal ferrite can particularly preferably contain at least one of Ba and Sr.
  • the ⁇ -iron oxide may particularly preferably contain at least one of Al and Ga.
  • the shape of the magnetic particles depends on the crystal structure of the magnetic particles.
  • barium ferrite (BaFe) and strontium ferrite can be hexagonal tabular.
  • ⁇ -iron oxide can be spherical.
  • Cobalt ferrite can be cubic.
  • the metal can be spindle-shaped.
  • the average particle size of the magnetic powder can be preferably 50 nm or less, more preferably 40 nm or less, even more preferably 30 nm or less, 25 nm or less, 22 nm or less, 21 nm or less, or 20 nm or less.
  • the average particle size may be, for example, 10 nm or more, preferably 12 nm or more.
  • the average aspect ratio of the magnetic powder may be, for example, 1.0 or more and 3.0 or less, or may be 1.0 or more and 2.9 or less.
  • the magnetic powder may contain hexagonal ferrite, and more particularly powder of nanoparticles containing hexagonal ferrite (hereinafter referred to as "hexagonal ferrite particles").
  • the hexagonal ferrite is preferably a hexagonal ferrite having an M-type structure.
  • Hexagonal ferrites for example, have a hexagonal plate shape or nearly a hexagonal plate shape.
  • the hexagonal ferrite may preferably contain at least one of Ba, Sr, Pb and Ca, more preferably at least one of Ba, Sr and Ca.
  • the hexagonal ferrite may be one or a combination of two or more selected from barium ferrite, strontium ferrite, and calcium ferrite, and particularly preferably barium ferrite or strontium ferrite.
  • Barium ferrite may further contain at least one of Sr, Pb, and Ca in addition to Ba.
  • the strontium ferrite may further contain at least one of Ba, Pb, and Ca in addition to Sr.
  • hexagonal ferrite can have an average composition represented by the general formula MFe 12 O 19 .
  • M is, for example, at least one of Ba, Sr, Pb and Ca, preferably at least one of Ba and Sr.
  • M may be a combination of Ba and one or more metals selected from the group consisting of Sr, Pb and Ca.
  • M may be a combination of Sr and one or more metals selected from the group consisting of Ba, Pb and Ca.
  • Part of Fe in the above general formula may be substituted with another metal element.
  • the average particle size of the magnetic powder is preferably 50 nm or less, more preferably 40 nm or less, even more preferably 30 nm or less, 25 nm or less, 22 nm or less, 21 nm or less, or 20 nm.
  • the average particle size may be, for example, 10 nm or more, preferably 12 nm or more, more preferably 15 nm or more.
  • the magnetic powder may have an average particle size of 10 nm to 50 nm, 10 nm to 40 nm, 12 nm to 30 nm, 12 nm to 25 nm, or 15 nm to 22 nm.
  • the average particle size of the magnetic powder is equal to or less than the above upper limit (e.g., 50 nm or less, particularly 30 nm or less), good electromagnetic conversion characteristics (e.g., SNR) can be obtained in the magnetic recording medium 10 with high recording density. can be done.
  • the average particle size of the magnetic powder is at least the above lower limit (e.g., 10 nm or more, preferably 12 nm or more), the dispersibility of the magnetic powder is further improved, resulting in better electromagnetic conversion characteristics (e.g., SNR). be able to.
  • the average aspect ratio of the magnetic powder is preferably 1.0 or more and 3.0 or less, more preferably 1.0 or more and 2.9 or less, and even more preferably 2.0. It can be 0 or more and 2.9 or less.
  • the average aspect ratio of the magnetic powder is within the above numerical range, the aggregation of the magnetic powder can be suppressed. can be suppressed. This can result in improved vertical orientation of the magnetic powder.
  • the average particle size and average aspect ratio of the 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 be thinned.
  • FIB Flucused Ion Beam
  • a carbon film and a tungsten thin film are formed as protective films as a pretreatment for observing a cross-sectional TEM image, which will be 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 vapor deposition, and the tungsten thin film is further formed on the magnetic layer side surface by vapor deposition or sputtering.
  • the thinning is performed along the length direction (longitudinal direction) of the magnetic recording medium 10 . That is, the thinning of the magnetic recording medium 10 forms a cross section parallel to both the longitudinal direction and the thickness direction.
  • FIG. 3 shows an example of a TEM photograph.
  • the particles labeled a and d are selected because their thickness can be clearly seen.
  • the average maximum plate thickness DA ave is obtained by simply averaging (arithmetic mean) the maximum plate thicknesses DA thus obtained.
  • the plate diameter DB of each magnetic powder is measured.
  • 50 particles whose plate diameters can be clearly confirmed are selected from the taken TEM photographs.
  • the particles labeled b and c, for example are selected because their plate diameters can be clearly identified.
  • the plate diameter DB of each of the 50 selected particles is measured.
  • a simple average (arithmetic mean) of the plate diameters DB obtained in this way is obtained to obtain an average plate diameter DB ave .
  • the average platelet diameter DB ave is the average particle size.
  • the average aspect ratio (DB ave /DA ave ) of the particles is obtained from the average maximum plate thickness DA ave and the average plate diameter DB ave .
  • the average particle volume of the magnetic powder is preferably 2500 nm 3 or less, preferably 2000 nm 3 or less, more preferably 1800 nm 3 or less, and even more preferably It may be 1700 nm 3 or less, 1600 nm 3 or less, or 1500 nm 3 or less.
  • the average particle volume of the magnetic powder can be preferably 500 nm 3 or more, more preferably 700 nm 3 or more.
  • the average particle volume of the magnetic powder is equal to or less than the above upper limit (for example, 2500 nm 3 or less), good electromagnetic conversion characteristics (eg, SNR) can be obtained in the magnetic recording medium 10 with high recording density.
  • the average particle volume of the magnetic powder is at least the above lower limit (for example, at least 500 nm 3 ), the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (for example, SNR) can be obtained.
  • the average particle volume of magnetic powder is determined as follows. First, the average maximum plate thickness DA ave and the average plate diameter DB ave are obtained as described in relation to the method for calculating the average particle size of the magnetic powder. Next, the average particle volume V of the magnetic powder is obtained from the following formula.
  • the magnetic powder may be barium ferrite magnetic powder or strontium ferrite magnetic powder, more preferably barium ferrite magnetic powder.
  • the barium ferrite magnetic powder contains iron oxide magnetic particles having barium ferrite as the main phase (hereinafter referred to as "barium ferrite particles").
  • Barium ferrite magnetic powder has high reliability in data recording, for example, its coercive force does not decrease even in a hot and humid environment. From this point of view, barium ferrite magnetic powder is preferable as the magnetic powder.
  • the average particle size of the barium ferrite magnetic powder is 50 nm or less, more preferably 10 nm or more and 40 nm or less, and even more preferably 12 nm or more and 25 nm or less.
  • the average thickness t m [nm] of the magnetic layer 13 is preferably 90 nm or less, more preferably 80 nm or less.
  • the average thickness t m of the magnetic layer 13 may be 35 nm ⁇ t m ⁇ 90 nm or 35 nm ⁇ t m ⁇ 80 nm.
  • the coercive force Hc1 measured in the thickness direction (perpendicular direction) of the magnetic recording medium 10 is preferably 2010 [Oe] or more and 3520 [Oe] or less, more preferably 2070 [Oe] or more and 3460 [Oe] or less, and even more It is preferably 2140 [Oe] or more and 3390 [Oe] or less.
  • the magnetic powder preferably contains a powder of nanoparticles containing ⁇ -iron oxide (hereinafter referred to as " ⁇ -iron oxide particles").
  • ⁇ -iron oxide particles can obtain a high coercive force even when they are fine particles.
  • the ⁇ -iron oxide contained in the ⁇ -iron oxide particles is preferably crystalline preferentially in the thickness direction of the magnetic recording medium 10 (BR>I perpendicular direction).
  • the ⁇ -iron oxide particles have a spherical or nearly spherical shape, or have a cubic or nearly cubic shape. Since the ⁇ -iron oxide particles have the above-described shape, the thickness of the medium using the ⁇ -iron oxide particles as the magnetic particles is reduced compared to the case where the hexagonal plate-shaped barium ferrite particles are used as the magnetic particles. It is possible to reduce the contact area between the particles in the direction and suppress the aggregation of the particles. Therefore, it is possible to improve the dispersibility of the magnetic powder and obtain a better SNR.
  • the ⁇ -iron oxide particles may have a core-shell structure.
  • the ⁇ -iron oxide particles include a core portion 21 and a two-layered shell portion 22 provided around the core portion 21 .
  • the shell portion 22 having a two-layer structure includes 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 core portion 21 contains ⁇ -iron oxide.
  • the ⁇ -iron oxide contained in the core portion 21 preferably has an ⁇ -Fe 2 O 3 crystal as a main phase, more preferably a single-phase ⁇ -Fe 2 O 3 .
  • the first shell portion 22a covers at least part of the periphery of the core portion 21. Specifically, the first shell portion 22 a 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 ensuring sufficient exchange coupling between the core portion 21 and the first shell portion 22a and improving the magnetic properties, it is preferable that the entire surface of the core portion 21 is covered.
  • the first shell portion 22a is a so-called soft magnetic layer, and may contain a soft magnetic material such as ⁇ -Fe, Ni-Fe alloy, 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 may include alpha iron oxide, aluminum oxide, or silicon oxide.
  • the ⁇ -iron oxide can include, for example, at least one iron oxide of Fe 3 O 4 , Fe 2 O 3 , and FeO.
  • the ⁇ -iron oxide may be obtained by oxidizing the ⁇ -Fe contained in the first shell portion 22a.
  • the ⁇ -iron oxide particles have the first shell portion 22a as described above, thermal stability can be ensured.
  • the coercive force Hc of the iron oxide particles (core-shell particles) as a whole can be adjusted to a coercive force Hc suitable for recording.
  • the ⁇ -iron oxide particles have the second shell portion 22b as described above, the ⁇ -iron oxide particles are exposed to the air during and before the manufacturing process of the magnetic recording medium 10, and the particle surface is It is possible to suppress the deterioration of the properties of the ⁇ -iron oxide particles due to the generation of rust and the like. Therefore, deterioration of the characteristics of the magnetic recording medium 10 can be suppressed.
  • the ⁇ -iron oxide particles may have a shell portion 23 with a single-layer structure, as shown in FIG.
  • the shell portion 23 has the same configuration as the first shell portion 22a.
  • the ⁇ -iron oxide particles it is more preferable that the ⁇ -iron oxide particles have a shell portion 22 with a two-layer structure.
  • the ⁇ -iron oxide particles may contain additives in place of the core-shell structure, or may have a core-shell structure and contain additives. In these cases, some of the Fe in the ⁇ -iron oxide particles is replaced by the additive.
  • the coercive force Hc of the entire ⁇ -iron oxide particles can also be adjusted to a coercive force Hc suitable for recording, so that the ease of recording can be improved.
  • the additive is a metal element other than iron, preferably a trivalent metal element, more preferably one or more selected from the group consisting of aluminum (Al), gallium (Ga), and indium (In).
  • the ⁇ -iron oxide containing the additive is an ⁇ -Fe 2-x M x O 3 crystal (here, M is a metal element other than iron, preferably a trivalent metal element, more preferably Al , Ga, and In, where x satisfies, for example, 0 ⁇ x ⁇ 1.
  • the average particle size (average maximum particle size) of the magnetic powder is preferably 22 nm or less, more preferably 8 nm or more and 22 nm or less, and even more preferably 12 nm or more and 22 nm or less.
  • a region having a size of 1/2 of the recording wavelength is the actual magnetized region. Therefore, by setting the average particle size of the magnetic powder to half or less of the shortest recording wavelength, a good SNR can be obtained. Therefore, when the average particle size of the magnetic powder is 22 nm or less, the magnetic recording medium 10 having a high recording density (for example, the magnetic recording medium 10 configured so as to record signals at the shortest recording wavelength of 44 nm or less) has good electromagnetic properties.
  • a transfer characteristic (eg, SNR) can be obtained.
  • the average particle size of the magnetic powder is 8 nm or more, the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (for example, SNR) can be obtained.
  • the average aspect ratio of the magnetic powder is preferably 1.0 or more and 3.0 or less, more preferably 1.0 or more and 2.9 or less, and even more preferably 1.0 or more and 2.5 or less.
  • the average aspect ratio of the magnetic powder is within the above numerical range, the aggregation of the magnetic powder can be suppressed, and the resistance applied to the magnetic powder when the magnetic powder is vertically oriented in the step of forming the magnetic layer 13 can be suppressed. be able to. Therefore, the perpendicular orientation of the magnetic powder can be improved.
  • the average particle size and average aspect ratio of the 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 be thinned.
  • FIB Flucused Ion Beam
  • a carbon film and a tungsten thin film are formed as protective films as a pretreatment for observing a cross-sectional TEM image, which will be 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 vapor deposition, and the tungsten thin film is further formed on the magnetic layer side surface by vapor deposition or sputtering. Thinning is performed along the length direction (longitudinal direction) of the magnetic recording medium 10 . That is, the thinning of the magnetic recording medium 10 forms a cross section parallel to both the longitudinal direction and the thickness direction.
  • the major axis length DL means the maximum distance (so-called maximum Feret diameter) between two parallel lines drawn from all angles so as to touch the outline of each particle.
  • the minor axis length DS means the maximum particle length in the direction orthogonal to the major axis (DL) of the particle.
  • the average major axis length DL ave is obtained by simply averaging (arithmetic mean) the major axis lengths DL of the measured 50 particles.
  • the average major axis length DL ave obtained in this manner is taken as the average particle size of the magnetic powder.
  • the short axis length DS of the measured 50 particles is simply averaged (arithmetic mean) to obtain the average short axis length DS ave .
  • the average aspect ratio (DL ave /DS ave ) of the particles is obtained from the average long axis length DL ave and the average short axis length DS ave .
  • the average particle volume of the magnetic powder is preferably 2000 nm 3 or less, preferably 1900 nm 3 or less, more preferably 1800 nm 3 or less, still more preferably 1700 nm 3 or less, 1600 nm 3 or less, or 1500 nm 3 or less. There may be.
  • the average particle volume of the magnetic powder can be preferably 500 nm 3 or more, more preferably 700 nm 3 or more.
  • the average particle volume of the magnetic powder is equal to or less than the above upper limit (for example, 2000 nm 3 or less), good electromagnetic conversion characteristics (eg, SNR) can be obtained in the magnetic recording medium 10 with high recording density.
  • the average particle volume of the magnetic powder is at least the above lower limit (for example, at least 500 nm 3 ), the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (for example, SNR) can be obtained.
  • the average particle volume of the magnetic powder is obtained as follows.
  • the magnetic recording medium 10 is processed by an FIB (Focused Ion Beam) method or the like to be thinned.
  • FIB Flucused Ion Beam
  • a carbon film and a tungsten thin film are formed as protective films as a pretreatment for observing a cross-sectional TEM image, which will be 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 vapor deposition, and the tungsten thin film is further formed on the magnetic layer side surface by vapor deposition or sputtering.
  • the thinning is performed along the length direction (longitudinal direction) of the magnetic recording medium 10 . That is, the thinning of the magnetic recording medium 10 forms a cross section parallel to both the longitudinal direction and the thickness direction.
  • the obtained thin sample was examined at an acceleration voltage of 200 kV and a total magnification of 500,000 times so that the entire magnetic layer 13 was included in the thickness direction of the magnetic layer 13. Observation of the cross section is performed to obtain a TEM photograph. Note that the magnification and the acceleration voltage may be appropriately adjusted according to the type of apparatus.
  • V ave particle volume
  • the coercive force Hc of the ⁇ -iron oxide particles is preferably 2500 Oe or more, more preferably 2800 Oe or more and 4200 e or less.
  • the magnetic powder may contain a powder of nanoparticles containing Co-containing spinel ferrite (hereinafter also referred to as "cobalt ferrite particles"). That is, the magnetic powder can be cobalt ferrite magnetic powder.
  • the cobalt ferrite particles preferably have uniaxial crystal anisotropy. Cobalt ferrite magnetic particles, for example, have a cubic or nearly cubic shape.
  • the Co-containing spinel ferrite may further contain, in addition to Co, one or more selected from the group consisting of Ni, Mn, Al, Cu, and Zn.
  • Cobalt ferrite has, for example, an average composition represented by the following formula.
  • CoxMyFe2Oz _ _ _ _ (In the above formula, M is, for example, one or more metals selected from the group consisting of Ni, Mn, Al, Cu, and Zn.
  • x is in the range of 0.4 ⁇ x ⁇ 1.0
  • y is a value within the range of 0 ⁇ y ⁇ 0.3, provided that x and y satisfy the relationship of (x+y) ⁇ 1.0
  • z is a value of 3 ⁇ z ⁇ 4 It is a value within the range.A part of Fe may be substituted with other metal elements.
  • the average particle size of the cobalt ferrite magnetic powder is preferably 25 nm or less, more preferably 23 nm or less.
  • the coercive force Hc of the cobalt ferrite magnetic powder is preferably 2500 Oe or more, more preferably 2600 Oe or more and 3500 Oe or less.
  • the average particle size of the magnetic powder is preferably 25 nm or less, more preferably 10 nm or more and 23 nm or less.
  • the average particle size of the magnetic powder is 25 nm or less, good electromagnetic conversion characteristics (for example, SNR) can be obtained in the magnetic recording medium 10 with high recording density.
  • the average particle size of the magnetic powder is 10 nm or more, the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (for example, SNR) can be obtained.
  • the average aspect ratio and average particle size of the magnetic powder are determined in the same manner as when the magnetic powder contains ⁇ -iron oxide particles.
  • the average particle volume of the magnetic powder is preferably 2000 nm 3 or less, preferably 1900 nm 3 or less, more preferably 1800 nm 3 or less, still more preferably 1700 nm 3 or less, 1600 nm 3 or less, or 1500 nm 3 or less. There may be.
  • the average particle volume of the magnetic powder can be preferably 500 nm 3 or more, more preferably 700 nm 3 or more.
  • the average particle volume of the magnetic powder is equal to or less than the above upper limit (for example, 2000 nm 3 or less), good electromagnetic conversion characteristics (eg, SNR) can be obtained in the magnetic recording medium 10 with high recording density.
  • the average particle volume of the magnetic powder is at least the above lower limit (for example, at least 500 nm 3 ), the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (for example, SNR) can be obtained.
  • the binder it is preferable to use a resin having a structure in which a cross-linking reaction is performed on a polyurethane-based resin or a vinyl chloride-based resin.
  • the binder is not limited to these, and other resins may be blended as appropriate depending on the physical properties required for the magnetic recording medium 10 .
  • the resin to be blended is not particularly limited as long as it is a resin commonly used in the coating type magnetic recording medium 10 .
  • binder examples include polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic acid ester-acrylonitrile copolymer.
  • acrylate-vinyl chloride-vinylidene chloride copolymer acrylate-vinylidene chloride copolymer, methacrylate-vinylidene chloride copolymer, methacrylate-vinyl chloride copolymer, methacrylate-ethylene copolymer
  • Polymer polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, acrylonitrile-butadiene copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitro cellulose), styrene-butadiene copolymers, polyester resins, amino resins, and synthetic rubbers.
  • thermosetting resin or a reactive resin may be used as the binder.
  • thermosetting or reactive resins include phenolic resins, epoxy resins, urea resins, melamine resins, alkyd resins, silicone resins, polyamine resins, urea-formaldehyde resins, and the like.
  • polar functional groups such as —SO 3 M, —OSO 3 M, —COOM, and P ⁇ O(OM) 2 are introduced into each of the binders described above for the purpose of improving the dispersibility of the magnetic powder.
  • M is a hydrogen atom or an alkali metal such as lithium, potassium, and sodium.
  • the polar functional groups include those of the side chain type with end groups of -NR1R2, -NR1R2R3 + X- , and those of the main chain type of > NR1R2 + X-.
  • R1, R2 and R3 are each independently a hydrogen atom or a hydrocarbon group
  • X- is a halogen element ion such as fluorine, chlorine, bromine or iodine, or an inorganic or organic ion is.
  • Polar functional groups also include -OH, -SH, -CN, and epoxy groups. The amount of these polar functional groups introduced into the binder is preferably 10 -1 to 10 -8 mol/g, more preferably 10 -2 to 10 -6 mol/g.
  • the magnetic layer 13 may contain a lubricant.
  • the lubricant may be, for example, one or more selected from fatty acids and/or fatty acid esters, and preferably contains both fatty acids and fatty acid esters.
  • the above fatty acid may preferably be a compound represented by the following general formula (1) or (2).
  • the fatty acid may contain one or both of a compound represented by the following general formula (1) and a compound represented by general formula (2).
  • the fatty acid ester may preferably be a compound represented by the following general formula (3) or (4).
  • the fatty acid ester may contain one or both of a compound represented by the following general formula (3) and a compound represented by general formula (4).
  • the lubricant is one or both of the compound represented by the general formula (1) and the compound represented by the general formula (2), and the compound represented by the general formula (3) and the compound represented by the general formula (4) By including either one or both of the compounds, it is possible to suppress an increase in the dynamic friction coefficient due to repeated recording or reproduction of the magnetic recording medium.
  • 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.
  • CH3 ( CH2 ) pCOO ( CH2 ) qCH3 ( 3 ) (However, in the general formula (3), p is an integer selected from the range of 14 to 22, more preferably 14 to 18, and q is the range of 2 to 5, more preferably 2 or more. It is an integer selected from the range of 4 or less.)
  • the lubricant examples include esters of monobasic fatty acids with 10 to 24 carbon atoms and any of monohydric to hexahydric alcohols with 2 to 12 carbon atoms, mixed esters thereof, difatty acid esters, and trifatty acid esters. etc.
  • Specific examples of the lubricant include lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, linolenic acid, elaidic acid, butyl stearate, pentyl stearate, heptyl stearate, and stearic acid.
  • octyl isooctyl stearate, octyl myristate, and the like.
  • antistatic agents examples include carbon black, natural surfactants, nonionic surfactants, and cationic surfactants.
  • Abrasives include, for example, ⁇ -alumina, ⁇ -alumina, ⁇ -alumina, silicon carbide, chromium oxide, cerium oxide, ⁇ -iron oxide, corundum, silicon nitride, titanium carbide, and oxides with an ⁇ conversion rate of 90% or more. Titanium, silicon dioxide, tin oxide, magnesium oxide, tungsten oxide, zirconium oxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide, and magnetic iron oxide. Examples include iron oxides, and those surface-treated with aluminum and/or silica, if necessary.
  • curing agents include polyisocyanate.
  • polyisocyanates include aromatic polyisocyanates such as adducts of tolylene diisocyanate (TDI) and active hydrogen compounds, and aliphatic polyisocyanates such as adducts of hexamethylene diisocyanate (HMDI) and active hydrogen compounds. mentioned.
  • the weight average molecular weight of these polyisocyanates is desirably in the range of 100-4500.
  • rust preventives include phenols, naphthols, quinones, nitrogen atom-containing heterocyclic compounds, oxygen atom-containing heterocyclic compounds, and sulfur atom-containing heterocyclic compounds.
  • non-magnetic reinforcing particles examples include aluminum oxide ( ⁇ , ⁇ or ⁇ alumina), chromium oxide, silicon oxide, diamond, garnet, emery, boron nitride, titanium carbide, silicon carbide, titanium carbide, and titanium oxide (rutile type or anatase type titanium oxide).
  • the underlayer 12 is a nonmagnetic layer containing nonmagnetic powder and a binder.
  • the underlayer 12 may further contain at least one additive selected from lubricants, antistatic agents, curing agents, antirust agents, and the like, if necessary.
  • the average thickness of the underlayer 12 is 1.50 ⁇ m or less, preferably 1.35 ⁇ m or less, more preferably 1.30 ⁇ m or less, even more preferably 1.20 ⁇ m or less, particularly preferably 1.10 ⁇ m or less, and 0.80 ⁇ m. 0.70 ⁇ m or less, or 0.60 ⁇ m or less. Resolution can be improved by having the average thickness of the underlying layer within this numerical range.
  • the average thickness of the underlayer 12 is obtained in the same manner as the average thickness t m of the magnetic layer 13 . However, the magnification of the TEM image is appropriately adjusted according to the thickness of the underlying layer 12 .
  • the underlayer 12 is provided between the magnetic layer 13 and the base layer 11 .
  • the non-magnetic powder includes, for example, at least one of inorganic particle powder and organic particle powder.
  • the non-magnetic powder may contain carbon powder such as carbon black.
  • One type of non-magnetic powder may be used alone, or two or more types 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 or metal sulfides.
  • Examples of the shape of the non-magnetic powder include various shapes such as acicular, spherical, cubic, and plate-like shapes, but are not limited to these shapes.
  • binder contained in the magnetic layer 13 also applies to the binder contained in the underlayer 12 .
  • the back layer 14 may contain a binder and non-magnetic powder.
  • the back layer 14 may further contain at least one additive selected from lubricants, curing agents, antistatic agents, and the like, if necessary.
  • the above description of the binder and non-magnetic powder contained in the underlayer 12 also applies to the binder and non-magnetic powder contained in the back layer.
  • the average particle size of the non-magnetic powder is preferably 10 nm or more and 150 nm or less, more preferably 15 nm or more and 110 nm or less.
  • the average particle size of the non-magnetic powder is determined in the same manner as the average particle size of the magnetic powder.
  • the non-magnetic powder may contain non-magnetic powder having two or more particle size distributions.
  • the average thickness of the back layer 14 (also referred to as “average thickness t b ” or “t b ” in this specification) is preferably 0.6 ⁇ m or less. Since the average thickness tb of the back layer 14 is within the above range, the thicknesses of the underlayer 12 and the base layer 11 can be kept thick even if the average thickness of the magnetic recording medium 10 is, for example, 5.90 ⁇ m or less. Thus, the running stability of the magnetic recording medium 10 in the recording/reproducing apparatus can be maintained. Although the lower limit of the average thickness tb of the back layer 14 is not particularly limited, it is, for example, 0.2 ⁇ m or more.
  • the back layer 14 is provided on the surface opposite to the surface on which the magnetic layer 13 is provided, of the two surfaces of the base layer 11 .
  • the average thickness of the magnetic recording medium 10 (also referred to herein as “average thickness t T ” or “t T ”) is preferably 5.90 ⁇ m or less, more preferably 5.60 ⁇ m or less, and even more preferably 5.30 ⁇ m or less, particularly preferably 5.20 ⁇ m or less, or 5.10 ⁇ m or less.
  • the average thickness t T of the magnetic recording medium 10 is set within the above numerical range (for example, by setting t T ⁇ 5.90 ⁇ m), the recording capacity that can be recorded in one data cartridge can be increased.
  • the lower limit of the average thickness tT of the magnetic recording medium 10 is not particularly limited, it is, for example, 3.50 ⁇ m ⁇ tT .
  • 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 cut into a length of 250 mm to prepare a sample. Next, using a Mitutoyo laser hologram (LGH-110C) as a measuring device, the thickness of the sample is measured at 5 or more points, and the measured values are simply averaged (arithmetic average) to obtain an average Calculate the value t T [ ⁇ m]. It is assumed that the measurement position is randomly selected from the sample.
  • LGH-110C Mitutoyo laser hologram
  • the magnetic recording medium 10 has a core portion level difference Rk of 5.5 nm or less in a bearing curve created based on height data of the magnetic layer side surface obtained using an atomic force microscope, preferably It is 5.2 nm or less, more preferably 5.0 nm or less, still more preferably 4.7 nm or less.
  • the resolution can be improved by keeping the core portion level difference Rk within this numerical range.
  • the core portion level difference Rk may be, for example, 3.6 nm or more or 3.8 nm or more.
  • the core portion level difference Rk is obtained from a bearing curve created based on height data of the magnetic layer side surface of the magnetic recording medium 10 obtained using an atomic force microscope.
  • a method for creating a bearing curve will be described, and then a method for calculating the core portion level difference Rk will be described.
  • the above bearing curve is created as follows. First, the uneven shape of the magnetic layer side surface of the magnetic recording medium 10 is measured with an atomic force microscope (AFM). The measurement is performed at 256 ⁇ 256 (65,536) measurement points in the area of 40 ⁇ m ⁇ 40 ⁇ m. AFM suitable for measurement is shown below. AFM: Dimension 3100 manufactured by Digital Instruments Cantilever: NanoWorld NCH-10T AFM measurement conditions are shown below. Measurement area: 40 ⁇ m ⁇ 40 ⁇ m Resolution: 256 ⁇ 256 Scan direction of AFM probe: MD direction (longitudinal direction) of magnetic tape Measurement mode: tapping mode scan ratio: 1Hz
  • the data obtained by the measurement is displayed in a binary editor (Binary Editor Bz), and from the data, the values of Sens.Zscan [nm / V] and Z_Scale [V], and the measured values at each measurement point Extract pAFM a,b .
  • the obtained values of Sens.Zscan and Z_Scale are read into the program LabVIEW manufactured by National Instruments, the matrix is inverted, and 2-bit excess data is deleted. Read the values obtained from LabVIEW into the calculation program.
  • the calculation program provides coordinate values for drawing the bearing curve.
  • the calculation flow in the calculation program is as follows.
  • the height AFM a,b of each measurement point is obtained by the following formula.
  • AFM a, b is the height of each measurement point
  • pAFM a, b is the measurement value of each measurement point
  • a and b are each independently an integer selected from the range of 1 to 256 is.
  • the "height data of the magnetic layer side surface obtained using an atomic force microscope” (hereinafter also simply referred to as “height data of the magnetic layer side surface”) is obtained by the above formula means the height AFM a,b of each measurement point determined by
  • the height difference H d of each measurement point is arranged as a one-dimensional array.
  • the one-dimensional array is sorted in ascending order (descending order).
  • Hd of the rearranged one-dimensional array is the value of the Y coordinate of each point that draws the bearing curve. That is, the value of the Y coordinate of the bearing curve is the height difference Hd .
  • the height difference Hd is referred to as the height in the bearing curve.
  • X coordinate value [%] Data Number/total number of data x 100 (In the above formula, Data Number is the element number of the one-dimensional array after sorting in descending order, and the total number of data is the number of all measurement points.)
  • FIG. 6 shows an example of Data Number, X-coordinate value, and Y-coordinate value obtained by the calculation program.
  • the obtained X coordinate value and Y coordinate value are plotted on the XY coordinates to create a bearing curve.
  • the X axis indicates the area ratio
  • the Y axis indicates the height (specifically, the height difference H d ).
  • the area ratio is the cumulative ratio of height (height difference H d ). That is, the area ratio is expressed in percentage by accumulating frequencies in descending order of height (height difference H d ) and taking the total number of measurement points (65,536) measured by AFM as 100. .
  • the height (height difference H d ) of the measurement point having a height (height difference H d ) of 2.50 nm or more The number is 10% of the total number of measurement points.
  • FIG. 7 is a graph showing an example of bearing curves.
  • the straight line with the smallest slope is found.
  • point C is the intersection of the straight line with the smallest slope and the area ratio of 0%.
  • point D be the intersection of the straight line with the smallest slope and the area ratio of 100%.
  • the absolute value of the difference between the Y coordinate of point C and the Y coordinate of point D is calculated.
  • the absolute value of the difference is the core level difference Rk.
  • the height of the bearing curve of the magnetic recording medium 10 at an area ratio of 10.00% is preferably 2.80 nm or less, more preferably 2.50 nm or less, and even more preferably 2.30 nm or less.
  • the fact that the height at the area ratio of 10.00% is within this numerical range can contribute to the improvement of the resolution.
  • the height at the area ratio of 10.00% may be, for example, 1.50 nm or more or 1.80 nm or more.
  • the height H of the bearing curve of the magnetic recording medium 10 at an area ratio of 20.00% is preferably 1.70 nm or less, more preferably 1.60 nm or less, and even more preferably 1.50 nm or less.
  • the fact that the height at the area ratio of 20.00% is within this numerical range can contribute to an improvement in resolution.
  • the height at the area ratio of 20.00% may be, for example, 0.90 nm or more or 1.10 nm or more.
  • the height of the bearing curve of the magnetic recording medium 10 at an area ratio of 30.00% is preferably 1.00 nm or less, more preferably 0.90 nm or less.
  • the fact that the height at the area ratio of 30.00% is within this numerical range can contribute to an improvement in resolution.
  • the height at the area ratio of 30.00% may be, for example, 0.40 nm or more or 0.60 nm or more.
  • the height of the bearing curve of the magnetic recording medium 10 at an area ratio of 40.00% is preferably 0.50 nm or less, more preferably 0.40 nm or less.
  • the fact that the height at the area ratio of 40.00% is within this numerical range can contribute to an improvement in resolution.
  • the height at the area ratio of 40.00% may be, for example, 0.10 nm or more or 0.20 nm or more.
  • the inventors discovered that the height of the bearing curve at each area ratio of 10.00%, 20.00%, 30.00%, and 40.00% has a high correlation with the resolution.
  • the inventors of the present invention found that, as described above, a magnetic recording medium exhibiting higher resolution can be obtained by setting the height at a specific area ratio to a specific numerical value or less. rice field. It is presumed that this is because reducing the height value at a specific area ratio contributes to reducing the unevenness of the magnetic layer side surface of the magnetic recording medium.
  • the power spectrum density (PSD) of the magnetic layer up to a spatial wavelength of 5 ⁇ m can be used as an index of waviness of the surface of the magnetic layer.
  • the power spectral density of the magnetic layer 13 up to a spatial wavelength of 5 ⁇ m is preferably 3.6 nm 3 or less, more preferably 3.3 nm 3 or less, even more preferably 3.0 nm 3 or less, and especially It is preferably 2.6 nm 3 or less.
  • the fact that the power spectral density is within this numerical range can contribute to the improvement of resolution. This is thought to be because the spacing can be reduced by keeping the power spectral density within the numerical range (for example, 3.6 nm 3 or less).
  • the power spectral density of the magnetic layer 13 up to a spatial wavelength of 5 ⁇ m is measured as follows. First, a magnetic recording medium 10 having a width of 12.7 mm is cut into a length of 10 mm to prepare a rectangular sample of 12.7 mm ⁇ 10 mm. Furthermore, samples of the same shape are prepared at two locations every 10 m to obtain a total of three samples. Each sample is fixed on a glass slide using carbon tape or the like. The surface is observed with an atomic force microscope (AFM) to obtain two-dimensional (2D) surface profile data. AFM suitable for measurement is shown below. AFM: Dimension 3100 manufactured by Digital Instruments Cantilever: NanoWorld NCH-10T AFM measurement conditions are shown below. Measurement area: 40 ⁇ m ⁇ 40 ⁇ m Resolution: 256 ⁇ 256 Scan direction of AFM probe: MD direction (longitudinal direction) of magnetic tape Measurement mode: tapping mode scan ratio: 1Hz
  • PSD MD a Fast Fourier Transform
  • PSD power spectral density ( nm3 ) z(n): surface profile data at the n-th point (nm)
  • L Measurement range (40 ⁇ m) in the X-axis direction (or Y-axis direction)
  • N number of points in the X-axis direction (256 points)
  • i imaginary unit
  • e Napier's number average: averaging operation in the Y-axis direction (or X-axis direction)
  • n variable (from 0 to N-1)
  • k wave number (from 0 to N-1)
  • the X-axis direction corresponds to the MD direction (longitudinal direction).
  • the PSD values at each wavelength obtained so far are integrated.
  • a simple average (arithmetic average) of the integrated values of the three samples is adopted as the power spectral density of the magnetic layer 13 up to a spatial wavelength of 5 ⁇ m.
  • a method for manufacturing the magnetic recording medium 10 having the above configuration will be described.
  • a non-magnetic powder, a binder, etc. are kneaded and dispersed in a solvent to prepare a paint for forming an undercoat layer.
  • magnetic powder, a binder, etc. are kneaded and dispersed in a solvent to prepare a coating material for forming a magnetic layer.
  • the following solvents, dispersing devices and kneading devices can be used for the preparation of the magnetic layer-forming paint and the underlayer-forming paint.
  • Examples of the solvent used for preparing the above 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
  • halogenated hydrocarbon solvents such as carbon tetrachloride, chloroform, and chlorobenzene. These may be used alone, or may be used by mixing them as appropriate.
  • a continuous twin-screw kneader for example, a continuous twin-screw kneader, a continuous twin-screw kneader capable of multistage dilution, a kneader, a pressure kneader, a roll kneader, or the like can be used. , and are not particularly limited to these devices.
  • Dispersing devices used for the above coating preparation include, for example, roll mills, ball mills, horizontal sand mills, vertical sand mills, spike mills, pin mills, tower mills, pearl mills (e.g. "DCP Mill” manufactured by Eirich), homogenizers, ultra A dispersing device such as a sonic disperser can be used, but it is not particularly limited to these devices.
  • the base layer 12 is formed by applying a base layer forming coating material to one main surface of the base layer 11 and drying it.
  • the magnetic layer 13 is formed on the underlayer 12 by coating the underlayer 12 with a magnetic layer-forming paint and drying it.
  • the magnetic powder is magnetically oriented in the thickness direction of the base layer 11 by, for example, a solenoid coil.
  • the magnetic powder may be magnetically oriented in the running direction (longitudinal direction) of the base layer 11 by, for example, a solenoid coil, and then magnetically oriented in the thickness direction of the base layer 11 .
  • the back layer 14 is formed on the other main surface of the base layer 11 .
  • the magnetic recording medium 10 is obtained.
  • the obtained magnetic recording medium 10 is rewound around the large-diameter core and hardened. Finally, after calendering the magnetic recording medium 10, it is cut into a predetermined width (for example, 1/2 inch width). As described above, the desired elongated long magnetic recording medium 10 is obtained.
  • the recording/reproducing device 30 has a configuration in which the tension applied in the longitudinal direction of the magnetic recording medium 10 can be adjusted. Further, the recording/reproducing device 30 has a configuration in which the magnetic recording cartridge 10A can be loaded.
  • the recording/reproducing device 30 has a configuration in which one magnetic recording cartridge 10A can be loaded will be described. You may have the structure which can be loaded with 10A.
  • the recording/reproducing device 30 is connected to information processing devices such as a server 41 and a personal computer (hereinafter referred to as "PC") 42 via a network 43, and the data supplied from these information processing devices is transferred to the magnetic recording cartridge 10A. It is configured to be able to record to
  • the shortest recording wavelength of the recording/reproducing device 30 is preferably 100 nm or less, more preferably 75 nm or less, still more preferably 60 nm or less, and particularly preferably 50 nm or less.
  • the recording/reproducing device 30 includes a spindle 31, a reel 32 on the side of the recording/reproducing device, a spindle driving device 33, a reel driving device 34, a plurality of guide rollers 35, a head unit 36, A communication interface (I/F hereinafter) 37 and a control device 38 are provided.
  • the spindle 31 is configured to be mountable with the magnetic recording cartridge 10A.
  • the magnetic recording cartridge 10A complies with the LTO (Linear Tape Open) standard, and rotatably accommodates a single reel 10C around which the magnetic recording 10 is wound in a cartridge case 10B.
  • a V-shaped servo pattern is recorded in advance on the magnetic recording medium 10 as a servo signal.
  • the reel 32 is configured to be able to fix the leading end of the magnetic recording medium 10 pulled out from the magnetic recording cartridge 10A.
  • the spindle drive device 33 is a device that drives the spindle 31 to rotate.
  • the reel driving device 34 is a device that drives the reel 32 to rotate. When data is recorded or reproduced on the magnetic recording medium 10, the spindle driving device 33 and the reel driving device 34 rotate the spindle 31 and the reel 32 to drive the magnetic recording medium 10. .
  • the guide roller 35 is a roller for guiding the travel of the magnetic recording medium 10 .
  • the head unit 36 includes a plurality of recording heads for recording data signals on the magnetic recording medium 10, a plurality of reproducing heads for reproducing the data signals recorded on the magnetic recording medium 10, and a plurality of servo heads for reproducing recorded servo signals.
  • a ring-type head can be used as the recording head, but the type of recording head is not limited to this.
  • the communication I/F 37 is for communicating with information processing devices such as the server 41 and the PC 42 and is connected to the network 43 .
  • the control device 38 controls the recording/reproducing device 30 as a whole. For example, the control device 38 records a data signal supplied from the information processing device on the magnetic recording medium 10 by the head unit 36 in response to a request from the information processing device such as the server 41 and the PC 42 . Further, the control device 38 reproduces the data signal recorded on the magnetic recording medium 10 by the head unit 36 in response to a request from the information processing device such as the server 41 and the PC 42, and supplies the data signal to the information processing device.
  • the magnetic recording cartridge 10A is mounted in the recording/reproducing device 30, the leading end of the magnetic recording medium 10 is pulled out, and the leading end of the magnetic recording medium 10 is transported to the reel 32 via a plurality of guide rollers 35 and the head unit 36. Attach to reel 32 .
  • the spindle driving device 33 and the reel driving device 34 are driven under the control of the control device 38 so that the magnetic recording medium 10 is driven from the reel 10C toward the reel 32.
  • Spindle 31 and reel 32 are rotated in the same direction.
  • the head unit 36 records information on the magnetic recording medium 10 or reproduces information recorded on the magnetic recording medium 10 .
  • the spindle 31 and the reel 32 are driven to rotate in the direction opposite to the above, so that the magnetic recording medium 10 travels from the reel 32 to the reel 10C. .
  • the head unit 36 also records information on the magnetic recording medium 10 or reproduces information recorded on the magnetic recording medium 10 .
  • the magnetic recording cartridge also called a tape cartridge
  • the magnetic recording medium may be wound, for example, on a reel.
  • the magnetic recording cartridge includes, for example, a communication unit that communicates with a recording/reproducing device, a storage unit, and a storage unit that stores information received from the recording/reproducing device via the communication unit. and a control unit that reads out information from the storage unit and transmits the information to the recording/reproducing device via the communication unit in response to the request.
  • the information may include adjustment information for adjusting the tension applied to the magnetic recording medium in the longitudinal direction.
  • the adjustment information may include, for example, dimension information in the width direction at multiple positions in the longitudinal direction of the magnetic recording medium.
  • the dimension information in the width direction is the dimension information at the time of manufacture (initial stage after manufacture) of the magnetic recording medium described below in [Construction of Cartridge Memory], and/or obtained during recording and/or reproduction processing of the magnetic recording medium. dimensional information to be used.
  • FIG. 9 is an exploded perspective view showing an example of the configuration of the cartridge 10A.
  • the cartridge 10A is a magnetic recording medium cartridge conforming to the LTO (Linear Tape-Open) standard, and a magnetic tape (tape-shaped magnetic recording medium ), reel lock 214 and reel spring 215 for locking rotation of reel 10C, spider 216 for unlocking reel 10C, lower shell 212A and upper shell 212B.
  • the reel 10C has a substantially disc shape with an opening in the center, and is composed of a reel hub 213A and a flange 213B made of a hard material such as plastic.
  • a leader pin 220 is provided at one end of the magnetic tape 10 .
  • the cartridge memory 211 is provided near one corner of the cartridge 10A.
  • the cartridge memory 211 faces a reader/writer (not shown) of the recording/reproducing device 30 when the cartridge 10A is loaded into the recording/reproducing device 30 .
  • the cartridge memory 211 communicates with the recording/reproducing device 30, more specifically, a reader/writer (not shown) in accordance with the wireless communication standard conforming to the LTO standard.
  • FIG. 10 is a block diagram showing an example of the configuration of the cartridge memory 211.
  • the cartridge memory 211 has an antenna coil (communication unit) 331 that communicates with a reader/writer (not shown) according to a prescribed communication standard, and generates and rectifies electric waves received by the antenna coil 331 using induced electromotive force.
  • a rectification/power supply circuit 332 that generates power, a clock circuit 333 that generates a clock using the same induced electromotive force from radio waves received by the antenna coil 331, a detection of the radio waves received by the antenna coil 331, and the antenna coil 331
  • a controller (control unit) 335 and a memory (storage unit) 336 for storing information.
  • the cartridge memory 211 also includes a capacitor 337 connected in parallel with the antenna coil 331, and the antenna coil 331 and the capacitor 337 constitute a resonance circuit.
  • the memory 336 stores information related to the cartridge 10A.
  • the memory 336 is non-volatile memory (NVM).
  • the storage capacity of memory 336 is preferably about 32 KB or greater. For example, if the cartridge 10A complies with the LTO-9 or LTO-10 standard, the memory 336 has a storage capacity of approximately 32 KB.
  • the memory 336 has a first storage area 336A and a second storage area 336B.
  • the first storage area 336A corresponds to the storage area of an LTO standard cartridge memory prior to LTO8 (hereinafter referred to as "conventional cartridge memory"), and is used to store information conforming to the LTO standard prior to LTO8. area.
  • the information conforming to the LTO standard prior to LTO8 includes, for example, manufacturing information (for example, the unique number of the cartridge 10A, etc.), usage history (for example, the number of tape withdrawals (Thread Count), etc.), and the like.
  • the second storage area 336B corresponds to an extended storage area for the storage area of the conventional cartridge memory.
  • the second storage area 336B is an area for storing additional information.
  • the additional information means information related to the cartridge 10A, which is not defined in the LTO standard prior to LTO8.
  • Examples of the additional information include tension adjustment information, management ledger data, index information, and thumbnail information of moving images stored on the magnetic tape 10, but are not limited to these data.
  • the tension adjustment information includes the distance between adjacent servo bands (distance between servo patterns recorded in adjacent servo bands) during data recording on the magnetic tape 10 .
  • the distance between adjacent servo bands is an example of width related information related to the width of the magnetic tape 10 . The details of the distance between servo bands will be described later.
  • the information stored in the first storage area 336A may be called “first information”
  • the information stored in the second storage area 336B may be called "second information”.
  • the memory 336 may have multiple banks. In this case, part of the plurality of banks may constitute the first storage area 336A, and the remaining banks may constitute the second storage area 336B. Specifically, for example, if the cartridge 10A complies with the LTO-9 standard or the LTO-10 standard, the memory 336 has two banks with a storage capacity of approximately 16 KB. One of the banks may constitute the first memory area 336A, and the other bank may constitute the second memory area 336B.
  • the antenna coil 331 induces an induced voltage by electromagnetic induction.
  • the controller 335 communicates with the recording/reproducing device 30 via the antenna coil 331 according to a prescribed communication standard. Specifically, for example, mutual authentication, command transmission/reception, or data exchange is performed.
  • the controller 335 stores information received from the recording/reproducing device 30 via the antenna coil 331 in the memory 336 .
  • the controller 335 reads information from the memory 336 in response to a request from the recording/reproducing device 30 and transmits the information to the recording/reproducing device 30 via the antenna coil 331 .
  • the magnetic recording medium 10 includes a magnetic layer and an underlayer, and in a bearing curve created based on height data of the magnetic layer side surface obtained using an atomic force microscope, the core portion level difference Rk is It is 5.5 nm or less, and the average thickness of the underlying layer is 1.50 ⁇ m or less. As a result, the magnetic recording medium 10 exhibits high resolution. Therefore, the magnetic recording medium 10 can increase the output during short-wavelength recording to approach the output during long-wavelength recording.
  • the resolution mentioned above means the reference tape ratio of the ratio of the output during short wavelength recording to the output during long wavelength recording. A method of calculating the resolution will be described below.
  • the following reference tape and the following device are used in addition to the magnetic recording medium (hereinafter also referred to as the sample tape) for evaluating the resolution.
  • Reference tape Master Standard Reference Tap (MSRT), or a tape whose resolution with MSRT is known (Secondary Standard Reference Tape, etc.)
  • Equipment LTO8 Full Height drive, or the following measurement conditions (head and tape speed below)
  • TRD1 (0.194 ⁇ m) ⁇ 14.4 [MHz]
  • TRD3 (0.774 ⁇ m) ⁇ 3.61 [MHz]
  • the recording current is the current value that maximizes the output.
  • an oscilloscope eg, Lecroy 9354
  • Lecroy 9354 an oscilloscope
  • a peak-to-peak value is output.
  • Each of the test tape and the reference tape is scanned 16 times or more, and the obtained outputs are averaged (arithmetic mean). Thereby, the respective outputs of the sample tape and the reference tape are calculated.
  • Resolution [%] (TRD1 output of test tape/TRD3 output of test tape)/(TRD1 output of reference tape/TRD3 output of reference tape) ⁇ 100
  • the resolution of the magnetic recording medium of the present technology is, for example, 90.0% or higher, preferably 92.0% or higher, more preferably 94.0% or higher, even more preferably 97.0% or higher, and particularly preferably is 100.0% or more.
  • the fact that the resolution is within this numerical range contributes to making the output during short-wavelength recording closer to the output during long-wavelength recording.
  • the magnetic recording medium 10 may further include a barrier layer 15 provided on at least one surface of the base layer 11, as shown in FIG.
  • the barrier layer 15 is a layer for suppressing dimensional changes of the base layer 11 depending on the environment. For example, one of the causes of the dimensional change is the hygroscopicity of the base layer 11. By providing the barrier layer 15, the penetration speed of moisture into the base layer 11 can be reduced.
  • Barrier layer 15 includes, for example, a metal or metal oxide. Examples of metals include Al, Cu, Co, Mg, Si, Ti, V, Cr, Mn, Fe, Ni, Zn, Ga, Ge, Y, Zr, Mo, Ru, Pd, Ag, Ba, Pt, At least one of Au and Ta can be used.
  • the metal oxide for example, a metal oxide containing one or more of the above metals can be used. More specifically, at least one of Al 2 O 3 , CuO, CoO, SiO 2 , Cr 2 O 3 , TiO 2 , Ta 2 O 5 and ZrO 2 can be used. Also, 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, 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 .
  • the magnification of the TEM image is appropriately adjusted according to the thickness of the barrier layer 15 .
  • the magnetic recording medium 10 may be incorporated into a library device. That is, the present technology also provides a library device including at least one magnetic recording medium 10 .
  • the library device has a configuration capable of adjusting the tension applied in the longitudinal direction of the magnetic recording medium 10, and may include a plurality of the recording/reproducing devices 30 described above.
  • Example 1 (Preparation step of coating material for magnetic layer formation) A coating material for forming a magnetic layer was prepared as follows. First, a first composition having the following formulation was kneaded with an extruder. Next, the kneaded first composition and the second composition having the following composition were added to a stirring tank equipped with a disper and premixed. Subsequently, sand mill mixing was carried out and filter treatment was carried out to prepare a coating material for forming a magnetic layer.
  • Aluminum oxide powder 5 parts by mass ( ⁇ -Al 2 O 3 , average particle size 90 nm)
  • Carbon black 1.5 parts by mass (trade name: Raven450)
  • Vinyl chloride resin 1.1 parts by mass (resin solution: resin content 30% by mass, cyclohexanone 70% by mass)
  • n-butyl stearate 2 parts by mass methyl ethyl ketone: 121.3 parts by mass toluene: 121.3 parts by mass cyclohexanone: 60.7 parts by mass
  • a base layer-forming coating material was prepared as follows. First, a third composition having the following formulation 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 premixed. Subsequently, sand mill mixing was carried out and filter treatment was carried out to prepare a base layer forming coating material.
  • stearic acid 2 parts by mass was added to the base layer forming paint prepared as described above.
  • a coating material for forming a back layer was prepared as follows. The following raw materials were mixed in a stirring tank equipped with a disper and subjected to filter treatment to prepare a backing layer forming coating material.
  • Carbon black (manufactured by Asahi Corporation, trade name: #80): 100 parts by mass Polyester polyurethane: 100 parts by mass (manufactured by Nippon Polyurethane Co., Ltd., trade name: N-2304)
  • Methyl ethyl ketone 500 parts by mass Toluene: 400 parts by mass
  • Cyclohexanone 100 parts by mass Polyisocyanate (manufactured by Tosoh Corporation, trade name: Coronate L): 10 parts by mass
  • a PEN film (base layer) having an elongated shape and an average thickness of 4.0 ⁇ m was prepared as a support.
  • a base layer forming coating material was applied to one main surface of the PEN film and dried to form a base layer having an average thickness of 1.30 ⁇ m on one main surface of the PEN film.
  • a magnetic layer-forming paint was applied onto the underlayer and dried to form a magnetic layer having an average thickness of 80 nm on the underlayer.
  • the magnetic powder was magnetically oriented in the thickness direction of the PEN film by a solenoid coil.
  • a back layer forming coating material was applied to the other main surface of the PEN film on which the underlayer and magnetic layer were formed, and dried to form a back layer having an average thickness of 0.5 ⁇ m. Then, the PEN film on which the underlayer, magnetic layer and back layer were formed was subjected to a curing treatment. At this time, the temperature was 60° C. and the time was 20 hours. After that, calendering was performed to smooth the surface of the magnetic layer.
  • Servo signals and data signals were written in the following manner on the long magnetic tape obtained as described above.
  • five servo bands with a servo band width W SB of 96 ⁇ m were formed by writing servo signals on the magnetic tape using a servo writer.
  • each servo band was formed with a row of V-shaped magnetic patterns.
  • Example 2 The magnetic powder contained in the magnetic layer was changed from barium ferrite magnetic powder of 2500 nm3 to barium ferrite magnetic powder of 1600 nm3 , and the aluminum oxide powder contained in the magnetic layer was changed to one with a primary particle size of 50 nm.
  • a magnetic tape was obtained in the same manner as in Example 1, except that the contained polyurethane resin UR8200 was changed to one having a lower glass transition temperature Tg and the average thickness of the underlayer was changed to 0.90 ⁇ m.
  • Example 3 The magnetic powder contained in the magnetic layer was changed from barium ferrite magnetic powder of 2500 nm3 to barium ferrite magnetic powder of 1600 nm3 , and the aluminum oxide powder contained in the magnetic layer was changed to one with a primary particle size of 50 nm.
  • a magnetic tape was obtained in the same manner as in Example 1, except that the contained polyurethane resin UR8200 was changed to one having a lower glass transition temperature Tg and the average thickness of the underlayer was changed to 0.60 ⁇ m.
  • Example 4 The magnetic powder contained in the magnetic layer was changed from barium ferrite magnetic powder of 2500 nm3 to barium ferrite magnetic powder of 1600 nm3 , and the aluminum oxide powder contained in the magnetic layer was changed to one having a primary particle size of 50 nm. Except that carbon black was added after the non-magnetic powder (needle-shaped iron oxide powder) was dispersed (that is, after the sand mill mixing was performed), and the average thickness of the underlayer was changed to 1.09 ⁇ m. A magnetic tape was obtained in the same manner as in 1.
  • Example 5 The magnetic powder contained in the magnetic layer was changed from barium ferrite magnetic powder of 2500 nm 3 to barium ferrite magnetic powder of 1600 nm 3 , aluminum oxide powder contained in the magnetic layer was changed to one with a primary particle size of 50 nm, and in the lower layer powder Except for adding carbon black after dispersing the non-magnetic powder (needle-shaped iron oxide powder) (that is, after performing the sand mill mixing) and changing the average thickness of the underlayer to 0.57 ⁇ m, A magnetic tape was obtained in the same manner as in 1.
  • Example 6 The magnetic powder contained in the magnetic layer was changed from barium ferrite magnetic powder of 2500 nm3 to barium ferrite magnetic powder of 1600 nm3 , and the aluminum oxide powder contained in the magnetic layer was changed to one having a primary particle size of 50 nm.
  • a magnetic tape was obtained in the same manner as in Example 1, except that the dispersion time (that is, the sand mill mixing time) was changed to 0.8 times and the average thickness of the underlayer was changed to 1.16 ⁇ m.
  • Example 7 The magnetic powder contained in the magnetic layer was changed from barium ferrite magnetic powder of 2500 nm3 to barium ferrite magnetic powder of 1600 nm3 , and the aluminum oxide powder contained in the magnetic layer was changed to one having a primary particle size of 50 nm.
  • a magnetic tape was obtained in the same manner as in Example 1, except that the dispersion time (that is, the sand mill mixing time) was changed to 0.8 times and the average thickness of the underlayer was changed to 0.69 ⁇ m.
  • Example 8 The magnetic powder contained in the magnetic layer was changed from barium ferrite magnetic powder of 2,500 nm 3 to barium ferrite magnetic powder of 1,600 nm 3 , and the aluminum oxide powder contained in the magnetic layer was changed to one with a primary particle size of 50 nm.
  • the same method as in Example 1 was repeated except that the included non-magnetic powder (acicular iron oxide powder) had an average major axis length of 0.04 ⁇ m and the average thickness of the underlayer was changed to 0.96 ⁇ m. I got a magnetic tape.
  • Example 9 The magnetic powder contained in the magnetic layer was changed from barium ferrite magnetic powder of 2,500 nm 3 to barium ferrite magnetic powder of 1,600 nm 3 , and the aluminum oxide powder contained in the magnetic layer was changed to one with a primary particle size of 50 nm.
  • the included non-magnetic powder acicular iron oxide powder
  • the average thickness of the underlayer was changed to 0.47 ⁇ m. I got a magnetic tape.
  • Example 10 A magnetic tape was obtained in the same manner as in Example 1, except that the curing treatment timing was changed from before calendering to after calendering, and the average thickness of the underlayer was changed to 1.22 ⁇ m.
  • Example 11 A magnetic tape was obtained in the same manner as in Example 1, except that the curing treatment timing was changed from before calendering to after calendering, the curing temperature was changed to 80° C., and the average thickness of the underlayer was changed to 1.31 ⁇ m. .
  • Example 12 A magnetic tape was obtained in the same manner as in Example 1, except that the curing treatment timing was changed from before calendering to after calendering, the curing time was changed to 40 hours, and the average thickness of the underlayer was changed to 1.27 ⁇ m. .
  • Example 13 A magnetic tape was obtained in the same manner as in Example 1, except that the dispersion time (that is, the sand mill mixing time) in the underlayer was changed to 0.8 times, and the average thickness of the underlayer was changed to 1.23 ⁇ m. .
  • Example 14 The magnetic powder contained in the magnetic layer was changed from barium ferrite magnetic powder of 2500 nm3 to barium ferrite magnetic powder of 1600 nm3 , aluminum oxide powder contained in the magnetic layer was changed to one with a primary particle size of 50 nm, and hardening treatment was performed.
  • a magnetic tape was obtained in the same manner as in Example 1, except that the average thickness of the underlayer was changed to 1.21 .mu.m.
  • Example 15 The magnetic powder contained in the magnetic layer was changed from barium ferrite magnetic powder of 2500 nm3 to barium ferrite magnetic powder of 1600 nm3 , aluminum oxide powder contained in the magnetic layer was changed to one with a primary particle size of 50 nm, and hardening treatment was performed.
  • a magnetic tape was obtained in the same manner as in Example 1, except that the average thickness of the underlayer was changed to 1.25 ⁇ m by performing additional calendering.
  • Example 16 The magnetic powder contained in the magnetic layer was changed from barium ferrite magnetic powder of 2500 nm3 to barium ferrite magnetic powder of 1600 nm3 , and the aluminum oxide powder contained in the magnetic layer was changed to one having a primary particle size of 50 nm.
  • a magnetic tape was produced in the same manner as in Example 1, except that the average thickness was changed from 80 nm to 60 nm, the curing treatment was additionally performed after calendering, and the average thickness of the underlayer was changed to 1.18 ⁇ m. got
  • Example 1 A magnetic tape was obtained in the same manner as in Example 1, except that hardening treatment was additionally performed after calendering and the average thickness of the underlayer was changed to 1.25 ⁇ m.
  • Example 2 The aluminum oxide powder contained in the magnetic layer was changed to one having a primary particle size of 50 nm, magnetic field orientation was not performed during coating of the lower magnetic layer, and hardening treatment was additionally performed after calendering. A magnetic tape was obtained in the same manner as in Example 1, except that the thickness was changed to 17 ⁇ m.
  • Example 3 The magnetic powder contained in the magnetic layer was changed from 2500 nm3 barium ferrite magnetic powder to 1600 nm3 barium ferrite magnetic powder, and the aluminum oxide powder contained in the magnetic layer was changed to one with a primary particle size of 50 nm.
  • a magnetic tape was obtained in the same manner as in Example 1, except that the average thickness of the underlayer was changed to 1.27 ⁇ m without the magnetic field orientation.
  • Example 5 A magnetic tape was produced in the same manner as in Example 1, except that 2.5 parts by mass of citric acid was added to the underlayer, the curing treatment was additionally performed after calendering, and the average thickness of the underlayer was changed to 1.23 ⁇ m. Obtained.
  • Density Magnetic PSD ( ⁇ 5 ⁇ m)
  • the measurement results of the magnetic tapes of Examples 1 to 16 and Comparative Examples 1 to 5 are shown in Table 1 below.
  • the configurations, methods, steps, shapes, materials, numerical values, etc. given in the above-described embodiments and examples are merely examples, and different configurations, methods, steps, shapes, materials, and the like may be necessary.
  • a numerical value or the like may be used.
  • the chemical formulas of compounds and the like are representative ones, and the valence numbers and the like are not limited as long as they are common names of the same compound.
  • a numerical range indicated using “to” indicates a range that includes the numerical values before and after “to” as the minimum and maximum values, respectively.
  • the upper limit value or lower limit value of the numerical range at one step may be replaced with the upper limit value or lower limit value of the numerical range at another step.
  • the materials exemplified in this specification can be used singly or in combination of two or more unless otherwise specified.
  • this technique can also take the following structures.
  • [1] including a magnetic layer and an underlayer In a bearing curve created based on height data of the magnetic layer side surface obtained using an atomic force microscope, a core level difference Rk is 5.5 nm or less, The average thickness of the underlayer is 1.50 ⁇ m or less, Tape-shaped magnetic recording medium.
  • the magnetic layer contains magnetic powder, and the magnetic powder contains hexagonal ferrite, ⁇ -iron oxide, or Co-containing spinel ferrite.

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WO2024161957A1 (ja) * 2023-01-31 2024-08-08 ソニーグループ株式会社 磁気記録媒体
WO2025173638A1 (ja) * 2024-02-14 2025-08-21 ソニーグループ株式会社 磁気記録媒体およびカートリッジ

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