WO2021199453A1 - 磁気記録媒体 - Google Patents

磁気記録媒体 Download PDF

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Publication number
WO2021199453A1
WO2021199453A1 PCT/JP2020/028064 JP2020028064W WO2021199453A1 WO 2021199453 A1 WO2021199453 A1 WO 2021199453A1 JP 2020028064 W JP2020028064 W JP 2020028064W WO 2021199453 A1 WO2021199453 A1 WO 2021199453A1
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WIPO (PCT)
Prior art keywords
magnetic
recording medium
magnetic recording
layer
less
Prior art date
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Ceased
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PCT/JP2020/028064
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English (en)
French (fr)
Japanese (ja)
Inventor
泰啓 榎本
潤 寺川
山鹿　実
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sony Group Corp
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Sony Group Corp
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Application filed by Sony Group Corp filed Critical Sony Group Corp
Priority to US17/914,639 priority Critical patent/US20230119551A1/en
Priority to JP2020542169A priority patent/JP6819836B1/ja
Priority to DE112020007016.6T priority patent/DE112020007016T5/de
Publication of WO2021199453A1 publication Critical patent/WO2021199453A1/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
    • G11B15/00—Driving, starting or stopping record carriers of filamentary or web form; Driving both such record carriers and heads; Guiding such record carriers or containers therefor; Control thereof; Control of operating function
    • G11B15/18—Driving; Starting; Stopping; Arrangements for control or regulation thereof
    • G11B15/43—Control or regulation of mechanical tension of record carrier, e.g. tape tension
    • 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
    • G11B23/037—Single reels or spools
    • 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
    • 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
    • G11B23/30—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 with provision for auxiliary signals
    • 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
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
    • G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
    • G11B5/714—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the dimension of the magnetic particles
    • 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
    • G11B5/62—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
    • G11B5/735—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 characterised by the back 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
    • G11B5/74—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
    • 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
    • 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
    • G11B5/852—Orientation in a magnetic field
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector

Definitions

  • This technology relates to magnetic recording media.
  • a magnetic recording medium is often used as a medium for recording a large amount of data.
  • Patent Document 1 As a technique relating to magnetic powder contained in a magnetic recording medium, Patent Document 1 below is formed by applying at least a magnetic paint containing a ferromagnetic powder and a binder on a non-magnetic support.
  • a magnetic recording medium having a magnetic layer which has a carboxyl group and at least one or more hydroxyl groups in the molecule in the magnetic layer, and is a condensed ring when there are two or more aromatic rings.
  • a magnetic recording medium characterized in that the group compound is contained in an amount of 0.4 [parts by weight] to 10 [parts by weight] with respect to 100 [parts by weight] of the ferromagnetic powder is disclosed.
  • the main purpose of this technology is to provide a magnetic recording medium having excellent thermal stability and electromagnetic conversion characteristics.
  • This technology uses the base layer and A magnetic layer provided on the base layer and containing magnetic powder, It is a magnetic recording medium having a layered structure having The average thickness t T of the magnetic recording medium is 5.4 ⁇ m or less. The average particle volume of the magnetic powder is 2300 nm 3 or less.
  • a magnetic recording medium in which the magnetic interaction ⁇ M calculated by the following formula (1) of the magnetic layer is ⁇ 0.362 ⁇ ⁇ M ⁇ ⁇ 0.22.
  • ⁇ M ⁇ Id (H) + 2Ir (H) -Ir ( ⁇ ) ⁇ / Ir ( ⁇ ) ...
  • Id (H) is the remanent magnetization measured by direct current degaussing
  • Ir (H) is the remanent magnetization measured by alternating current degaussing
  • Ir ( ⁇ ) is the applied magnetic field of 6 kOe. Is the remanent magnetization measured as.
  • the magnetic powder can be vertically oriented.
  • the magnetic interaction ⁇ M calculated by the above formula (1) of the magnetic layer can be ⁇ 0.35 ⁇ ⁇ M.
  • the magnetic interaction ⁇ M calculated by the above formula (1) of the magnetic layer can be ⁇ 0.3 ⁇ ⁇ M.
  • the average particle volume of the magnetic powder can be 1600 nm 3 or less.
  • the average thickness t T of the magnetic recording medium can be 5.3 ⁇ m or less.
  • the average thickness t T of the magnetic recording medium can be 5.2 ⁇ m or less.
  • the average thickness t B of the base layer can be 4.8 ⁇ m or less.
  • the average thickness t B of the base layer can be 4.4 ⁇ m or less.
  • the base layer may be formed of PET (polyethylene terephthalate) or PEN (polyethylene naphthalate).
  • the saturation magnetization amount Ms in the longitudinal direction of the recording medium may satisfy the following relationship. 3.0 ⁇ 10 -3 emu ⁇ Ms
  • the average thickness of the magnetic layer can be 80 nm or less.
  • the average thickness of the magnetic layer can be 70 nm or less.
  • the average thickness of the magnetic layer can be 60 nm or less.
  • the vertical square ratio of the magnetic recording medium can be 65% or more.
  • the vertical square ratio of the magnetic recording medium can be 67% or more.
  • the vertical square ratio of the magnetic recording medium can be 70% or more.
  • the magnetic recording medium may have a layer structure having the magnetic layer, the base layer, and the base layer in this order.
  • the ratio of (average thickness of the magnetic layer + average thickness of the base layer) / (average thickness of the base layer) can be 0.16 or more.
  • the magnetic recording medium may have a layer structure having the magnetic layer, the base layer, the base layer, and the back layer in this order.
  • the ratio of (average thickness of the magnetic layer + average thickness of the base layer + average thickness of the back layer) / (average thickness of the magnetic recording medium) can be 0.19 or more.
  • Thermostable K u V act / k B T of the magnetic recording medium may be a 63 or higher.
  • the SNR of the magnetic recording medium can be 0.3 dB or more.
  • the magnetic powder may contain hexagonal ferrite.
  • the average particle volume of the magnetic powder can be 1500 nm 3 or less.
  • the average particle volume of the magnetic powder can be 1400 nm 3 or less.
  • the average thickness t B of the base layer can be 4.2 ⁇ m or less.
  • the average thickness of the magnetic layer can be 50 nm or less.
  • FIG. 8A is a schematic diagram of the layout of the data band and the servo band.
  • FIG. 8A is a schematic diagram of the layout of the data band and the servo band.
  • FIG. 8B is an enlarged view of the data band.
  • This is an example of a TEM photograph of a magnetic layer. It is sectional drawing which shows the structure of a magnetic particle. It is sectional drawing which shows the structure of the magnetic particle in the modification. It is the schematic of the recording / playback apparatus. It is an exploded perspective view which shows an example of the structure of a cartridge. It is a block diagram which shows an example of the structure of a cartridge memory. It is a schematic diagram of the cross section of the magnetic recording medium of the modification. It is a schematic diagram of the data band and the servo band formed in the magnetic layer. It is an exploded perspective view which shows an example of the structure of the modification of the cartridge.
  • the magnetic recording medium of the present technology has a magnetic layer containing magnetic powder having a specific particle volume, and the magnetic interaction ⁇ M in the magnetic layer is within a specific numerical range.
  • the magnetic recording medium of the present technology is excellent not only in thermal stability but also in electromagnetic conversion characteristics.
  • the particle volume of the magnetic powder becomes smaller, so that the magnetization recorded on the magnetic recording medium (specifically, the magnetic layer) is easily lost by the thermal energy. , Can result in attenuation of the data signal.
  • the stability of the magnetic recording medium with respect to heat also referred to as thermal stability
  • the storage stability of the magnetic recording medium decreases. sell. Therefore, from the viewpoint of thermal stability, it is considered necessary that the particles of the magnetic powder are appropriately agglomerated.
  • the decrease in the particle volume of the magnetic powder brings about the improvement of the recording density and the electromagnetic conversion characteristics, but may also bring about the decrease in the thermal stability.
  • the parameter relating to the agglutination state of the magnetic powder in the magnetic layer of the magnetic recording medium can be expressed by the magnetic interaction ⁇ M represented by the following formula (1).
  • ⁇ M ⁇ Id (H) + 2Ir (H) -Ir ( ⁇ ) ⁇ / Ir ( ⁇ ) ...
  • Id (H) is the remanent magnetization measured by direct current degaussing
  • Ir (H) is the remanent magnetization measured by alternating current degaussing
  • Ir ( ⁇ ) is the applied magnetic field of 6 kOe. Is the remanent magnetization measured as.
  • the magnetic recording medium of the present technology has a magnetic interaction ⁇ M of ⁇ 0.362 ⁇ ⁇ M ⁇ ⁇ 0.22.
  • the magnetic interaction ⁇ M is preferably ⁇ M ⁇ ⁇ 0.225, more preferably ⁇ M ⁇ ⁇ 0.23, still more preferably ⁇ M ⁇ ⁇ 0.235, still more preferably.
  • the magnetic interaction ⁇ M is preferably ⁇ 0.35 ⁇ ⁇ M, more preferably ⁇ 0.3 ⁇ ⁇ M, and further preferably ⁇ 0.28 ⁇ ⁇ M. It is possible.
  • the magnetic interaction ⁇ M is preferably ⁇ 0.35 ⁇ ⁇ M ⁇ ⁇ 0.225, more preferably ⁇ 0.3 ⁇ ⁇ M ⁇ ⁇ 0.23, and even more preferably ⁇ 0.28 ⁇ ⁇ M ⁇ ⁇ 0. It can be .235.
  • the magnetic recording medium of the present technology has good thermal stability and electromagnetic conversion characteristics when the magnetic interaction ⁇ M is within the above numerical range. If the magnetic interaction ⁇ M is too small (for example, less than ⁇ 0.362), the thermal stability can be improved, but the electromagnetic conversion characteristics can be deteriorated. If the magnetic interaction ⁇ M is too large (eg, greater than ⁇ 0.22), the electromagnetic conversion characteristics can be good, but the thermal stability can be poor.
  • the magnetic interaction ⁇ M is a parameter indicating the agglutination state of the magnetic powder particles.
  • the magnetic interaction ⁇ M will be described below with reference to the figures.
  • Id (H) saturates the magnetization of the sample in one direction with a sufficiently strong applied magnetic field, then returns the magnetic field to zero and is negative. It is measured as a residual magnetization curve (DCD curve: DC demagnetization remanence curve) obtained as a value of the residual magnetic field with respect to the applied magnetic field of. Further, as shown in FIG.
  • Ir (H) is demagnetized, the magnetization distribution of the sample is isotropic, and the remanent magnetization curve (IRM curve) obtained as the value of the remanent magnetization with respect to the positive applied magnetic field from that state. : Isothermal Remanent Magnetization).
  • the initial state is isotropically degaussed.
  • the amount of magnetization that is inverted by the application of a magnetic field is half the number of particles (magnetization amount) of the total magnetic powder.
  • the Ir (H) value gradually increases with the application of a positive magnetic field, and when Hr is reached, the Ir (H) value (IRM value) of the medium in which there is no interaction between magnetic powder particles becomes. It becomes half the value of Ir ( ⁇ ). Further, when a magnetic field is applied, it finally becomes an Ir ( ⁇ ) value.
  • Id (H) Ir ( ⁇ ) -2 Ir (H)
  • Id (H) Ir ( ⁇ ) -2 Ir (H)
  • 2Ir (H) Ir ( ⁇ ) -Id (H)
  • Md (H) 1-2 Mr (H) ...
  • Mr (H) ⁇ Ir (H) -Ir (0) ⁇ / ⁇ Ir ( ⁇ ) -Ir (0) ⁇ . do. This is because Ir ( ⁇ ) ⁇ Id (0) does not completely match. This is also because Ir (0) cannot be completely degaussed and does not become 0.
  • the above equation (2) is an equation applicable to an aggregate of uniaxial single magnetic domain fine particles in which there is no interaction between magnetic powder particles, and does not depend on the magnetization reversal mechanism inside the particles or the particle orientation. That is, when the interaction between the magnetic powder particles exists, the above equation (2) does not apply, and the equal sign between the right side and the left side does not hold. Therefore, it was examined to quantitatively handle the interaction between magnetic powder particles by ⁇ M (H) represented by the following formula (3).
  • ⁇ M (H) Md (H)- ⁇ 1-2 Mr (H) ⁇ ... (3)
  • Md (H) Id (H) / Id (0)
  • Mr (H) ⁇ Ir (H) -Ir (0) ⁇ / ⁇ Ir ( ⁇ ) -Ir (0) ⁇ .
  • Ir (H) in the above formula (3) is measured every 200 Oe in H in the range of 0 to 6 kOe.
  • Id (H) is measured every 200 Oe in H in the range of 0 to -6 kOe.
  • the minimum value of ⁇ M (H) calculated from each measured Ir (H) value and each Id (H) value is an index ⁇ M indicating the strength of interaction between magnetic powder particles. And said.
  • the thermal stability of the magnetic recording medium can be improved, and the electromagnetic conversion characteristics can be further improved.
  • the saturation magnetization amount Ms of the magnetic recording medium in the longitudinal direction is preferably 3.0 ⁇ 10 -3 emu ⁇ . It is Ms, more preferably 3.2 ⁇ 10 -3 emu ⁇ Ms, and even more preferably 3.4 ⁇ 10 -3 emu ⁇ Ms.
  • the saturation magnetization amount Ms can be obtained as follows. First, a VSM is used to obtain an MH hysteresis loop of a magnetic recording medium. Next, the saturation magnetization amount Ms is obtained from the obtained MH hysteresis loop.
  • thermostable K u V act / k B T the size of magnetic powder, i.e. reducing the particle volume of the magnetic powder results in a decrease in thermal stability.
  • the decrease in thermal stability results in a decrease in the storage stability of the magnetic recording medium, which is particularly problematic when the magnetic recording medium is stored for a long period of time.
  • thermostable K u V act / k B T is preferably 63 or more, more preferably 65 or more, more preferably 70 or more, even more preferably may be 80 or more.
  • the magnetic recording medium of the present technology, by its thermal stability K u V act / k B T is within the above range is excellent in thermal stability, thereby has excellent storage stability, long-term storage It is also excellent in stability. Further, the magnetic recording medium is also excellent from the viewpoint of the output signal.
  • the magnetic recording medium of the present technology may have an SNR of preferably 0.3 dB or more, more preferably 0.5 dB or more.
  • the magnetic recording medium of the present technology has good electromagnetic conversion characteristics when its SNR is within the above numerical range.
  • the average particle volume of the magnetic powder contained in the magnetic recording medium of the present technique is 2300 nm 3 or less, preferably 2000 nm 3 or less, more preferably 1600 nm 3 or less, more preferably 1500 nm 3 or less, more preferably It can be 1400 nm 3 or less, and even more preferably 1300 m 3 or less.
  • the electromagnetic conversion characteristics are improved.
  • the magnetic recording medium of the present technology is very small as described above, the magnetic recording medium of the present technology is excellent in thermal stability as described above. Where it is difficult to achieve both electromagnetic conversion characteristics and thermal stability, this technology can improve both electromagnetic conversion characteristics and thermal stability.
  • the average particle volume of the magnetic powder may be, for example, 500 nm 3 or more, particularly 700 nm 3 or more.
  • the square ratio in the vertical direction can be preferably 65% or more, more preferably 67% or more, still more preferably 70% or more.
  • the vertical orientation of the magnetic powder is sufficiently high, so that a more excellent cNR can be obtained. Therefore, better electromagnetic conversion characteristics can be obtained.
  • the square ratio in the longitudinal direction can be preferably 35% or less, more preferably 27% or less, still more preferably 20% or less.
  • the vertical orientation of the magnetic powder is sufficiently high, so that a more excellent SNR can be obtained. Therefore, better electromagnetic conversion characteristics can be obtained.
  • the average thickness t T of the magnetic recording medium of the present technology is preferably 5.8 ⁇ m or less, more preferably 5.6 ⁇ m or less, more preferably 5.5 ⁇ m or less, still more preferably 5.4 ⁇ m or less, still more preferably 5. It can be 3 ⁇ m or less, more preferably 5.2 ⁇ m or less, still more preferably 5.1 ⁇ m or less, still more preferably 5.0 ⁇ m or less.
  • the magnetic recording medium of the present technology may have such a thin overall thickness.
  • the present technology makes it possible to improve the recording capacity in addition to improving the electromagnetic conversion characteristics and the thermal stability.
  • the lower limit of the average thickness t T of the magnetic recording medium 10 is not particularly limited, but is, for example, 3.5 ⁇ m ⁇ t T.
  • the width of the magnetic recording medium according to the present technology may be, for example, 5 mm to 30 mm, particularly 7 mm to 26 mm, more particularly 10 mm to 20 mm, and even more particularly 11 mm to 19 mm.
  • the length of the tape-shaped magnetic recording medium according to the present technology can be, for example, 500 m to 1500 m.
  • the tape width according to the LTO8 standard is 12.65 mm and the length is 960 m.
  • the magnetic recording medium according to the present technology is in the form of a tape, and may be, for example, a long magnetic recording tape.
  • the tape-shaped magnetic recording medium according to the present technology may be housed in, for example, a magnetic recording cartridge. More specifically, it may be housed in the cartridge in a state of being wound around a reel in the magnetic recording cartridge.
  • the magnetic recording medium of the present technology may include a magnetic layer, a base layer, a base layer (also referred to as a substrate), and a back layer. These four layers may be laminated in this order.
  • the magnetic recording medium according to the present technology may include other layers in addition to these layers. The other layer may be appropriately selected depending on the type of magnetic recording medium.
  • the magnetic recording medium according to 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 in.
  • the magnetic recording medium 10 includes a long base layer 11, a base layer 12 provided on one main surface of the base layer 11, a magnetic layer 13 provided on the base layer 12, and a base layer 11.
  • a back layer 14 provided on the other main surface is provided.
  • the base layer 12 and the back layer 14 are provided as needed and may be omitted.
  • the magnetic recording medium 10 has a long tape shape and travels in the longitudinal direction during recording and reproduction.
  • the surface of the magnetic layer 13 is the surface on which the magnetic head travels.
  • the magnetic recording medium 10 is preferably used in a recording / reproducing device including a ring-shaped head as a recording head.
  • the "vertical direction” means a direction perpendicular to the surface of the magnetic recording medium 10 (thickness direction of the magnetic recording medium 10), and the "longitudinal direction” means the magnetic recording medium 10.
  • the base layer 11 is a non-magnetic support that supports the base layer 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 4.8 ⁇ m or less, more preferably 4.6 ⁇ m or less, more preferably 4.5 ⁇ m or less, more preferably 4.4 ⁇ m or less, still more preferably 4.2 ⁇ m or less, and even more. It can preferably be 4.0 ⁇ m or less.
  • the average thickness of the base layer 11 is 4.8 ⁇ m or less, the recording capacity that can be recorded in one data cartridge can be increased as compared with a general magnetic recording medium.
  • the average thickness of the base layer 11 can be preferably 3 ⁇ m or more, more preferably 3.3 ⁇ m or more, and even more preferably 3.5 ⁇ m or more. When the average thickness of the base layer 11 is 3 ⁇ m or more, it is possible to suppress a decrease in the strength of the base layer 11.
  • 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 the magnetic recording medium 10 is cut out to a length of 250 mm to prepare a sample. Subsequently, the layers other than the base layer 11 of the sample (that is, the base layer 12, the magnetic layer 13 and the back layer 14) are removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, using a laser holo gauge (LGH-110C) manufactured by Mitutoyo as a measuring device, the thickness of the sample (base layer 11) is measured at 5 or more points, and the measured values are simply averaged (arithmetic mean). ), And the average thickness of the base layer 11 is calculated. The measurement position shall be randomly selected from the sample.
  • a laser holo gauge 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 examples include PET (polyethylene terephthalate), PEN (polyethylene terephthalate), PBT (polybutylene terephthalate), PBN (polybutylene terephthalate), PCT (polycyclohexylene dimethylene terephthalate), and 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).
  • the vinyl resin contains, for example, at least one of PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride).
  • polymer resins include, for example, PA (polyamide, nylon), aromatic PA (aromatic polyamide, aramid), PI (polyimide), aromatic PI (aromatic polyimide), PAI (polyamideimide), aromatic PAI.
  • PA Polyamide, nylon
  • aromatic PA aromatic polyamide, aramid
  • PI polyimide
  • aromatic PI aromatic polyimide
  • PAI polyamideimide
  • Aroma PAI aromatic PAI.
  • PBO Polybenzoxazole, eg Zylon®
  • Polyether Polyetherketone
  • PEEK Polyetheretherketone
  • Polyetherester PolyES (Polyethersulfone)
  • PEI polyetherimide
  • PSF polysulphon
  • PPS polyphenylene sulfide
  • PC polyamide
  • PAR polyaraylate
  • PU polyethane
  • the base layer 11 contains, for example, polyester as a main component.
  • the polyester may be, for example, PET (polyethylene terephthalate), PEN (polyethylene terephthalate), PBT (polybutylene terephthalate), PBN (polybutylene terephthalate), PCT (polycyclohexylene dimethylene terephthalate), PEB (polyethylene-p-).
  • Oxybenzoate) and polyethylene bisphenoxycarboxylate may be one or a mixture of two or more.
  • the "main component” means the component having 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 ratio of polyester in the base layer 11 is, for example, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80 with respect to the mass of the base layer 11. It may mean that it is mass% or more, 90% by mass or more, 95% by mass or more, or 98% by mass or more, or it may mean that the base layer 11 is composed of polyester only.
  • the base layer 11 may be preferably formed of PET (polyethylene terephthalate) or PEN (polyethylene naphthalate).
  • the base layer 11 may contain a resin other than the polyester described below in addition to the polyester.
  • the base layer 11 may be formed from PET or PEN.
  • the magnetic layer 13 is a recording layer for recording a signal.
  • the magnetic layer 13 contains, for example, a magnetic powder and a binder.
  • the magnetic layer 13 may further contain at least one additive such as a lubricant, an antistatic agent, an abrasive, a curing agent, a rust preventive, and non-magnetic reinforcing particles, if necessary.
  • the magnetic layer 13 preferably has a plurality of servo band SBs and a plurality of data band DBs in advance.
  • the plurality of servo bands SB are provided at equal 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 controlling the tracking 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 band SB to the surface area S of the magnetic layer 13 can be preferably 0.8% or more from the viewpoint of securing a servo track of 5 or more.
  • 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 (Sigma High Chemical Co., Ltd., Sigmar Q), and then the developed magnetic recording medium 10 is observed with an optical microscope, and the servo bandwidth W SB And measure the number of servo bands SB.
  • the ratio R S is calculated from the following formula.
  • Ratio RS [%] (((servo band width W SB ) x (number of servo bands)) / (width of magnetic recording medium 10)) x 100
  • the number of servo bands SB may be preferably 5 or more, more preferably 5 + 4n (where n is a positive integer) or more, and even more preferably 9 + 4n or more.
  • the number of servo bands SB is not particularly limited, but is, for example, 33 or less.
  • the number of servo band SBs can be confirmed as follows. First, the surface of the magnetic layer 13 is observed with a magnetic force microscope (MFM) to obtain an MFM image. Next, the number of servo band SBs is counted using the MFM image.
  • MFM magnetic force microscope
  • the servo bandwidth W SB can be preferably 95 ⁇ m or less, more preferably 60 ⁇ m or less, and even more preferably 30 ⁇ m or less from the viewpoint of ensuring a high recording capacity.
  • the servo bandwidth W SB can preferably be 10 ⁇ m or more. Manufacture of a recording head capable of reading a servo signal with a servo bandwidth W SB of less than 10 ⁇ m can be difficult.
  • FIG. 16A is a schematic view of a data band and a servo band formed on the magnetic layer of the magnetic recording tape. As shown in FIG. 16A, the magnetic layer has four data bands d0 to d3. The magnetic layer has a total of five servo bands S0 to S4 so that each data band is sandwiched between two servo bands. As shown in FIG. 16A
  • each servo band has five servo signals S5a inclined at a predetermined angle ⁇ 1 and five servo signals S5b inclined at the same angle in the direction opposite to the signal, and a predetermined angle. It repeatedly has a frame unit composed of four servo signals S4a inclined at ⁇ 1 and four servo signals S4b inclined at the same angle in the direction opposite to the signal.
  • the angle ⁇ 1 can be, for example, 5 ° to 25 °, particularly 11 ° to 20 °.
  • the magnetic layer 13 is configured so that a plurality of data tracks Tk can be formed in the data band DB.
  • the data track width W can be preferably 2.0 ⁇ m or less, more preferably 1.5 ⁇ m or less, and even more preferably 1.0 ⁇ m or less from the viewpoint of ensuring a high recording capacity.
  • the data track width W can preferably be 0.02 ⁇ m or more.
  • the data track width W is calculated as follows.
  • the data recording pattern of the data band portion of the magnetic layer 13 on which the data is recorded on the entire surface is observed using a magnetic force microscope (MFM) to obtain an MFM image.
  • MFM Magnetic force microscope
  • the track width is measured at 10 points using the analysis software attached to the Dimension 3100, and the average value (simple average) is taken.
  • the average value is the data track width W.
  • the measurement conditions of the MFM are a sweep speed: 1 Hz, a chip used: MFMR-20, a lift height: 20 nm, and a correction: Flatten order 3.
  • the magnetic layer 13 preferably has a minimum value L of the distance between magnetization reversals and a data track width W of W / L ⁇ 200, more preferably W / L ⁇ 60, even more preferably W / L ⁇ 45, and particularly preferably W. Data can be recorded so that / L ⁇ 30.
  • the minimum value L of the magnetization reversal distance is a constant value and the minimum value L of the magnetization reversal distance and the track width W are W / L> 200 (that is, when the track width W is large)
  • the track recording density increases. Therefore, there is a risk that sufficient recording capacity cannot be secured.
  • W / L is in the range of W / L ⁇ 60 as described above.
  • 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, but is, for example, 1 ⁇ W / L.
  • the magnetic layer 13 has a minimum value L of the magnetization reversal distance of preferably 55 nm or less, more preferably 53 nm or less, still more preferably 52 nm or less, 50 nm or less, 48 nm or less, or 44 nm or less.
  • the data can be recorded so as to be 40 nm or less, particularly preferably 40 nm or less.
  • the lower limit of the minimum value L of the magnetization reversal distance can be preferably 20 nm or more in consideration of the magnetic particle size.
  • the minimum value L of the magnetization reversal distance is considered by the magnetic particle size.
  • the minimum value L of the magnetization reversal distance is obtained as follows.
  • the data recording pattern of the data band portion of the magnetic layer 13 on which the data is recorded on the entire surface is observed using a magnetic force microscope (MFM) to obtain an MFM image.
  • MFM Magnetic force microscope
  • 50 bit-to-bit distances are measured from the two-dimensional unevenness chart of the obtained MFM image recording pattern.
  • the measurement of the bit-to-bit distance is performed using the analysis software attached to the Dimension 3100.
  • the value that is approximately the greatest common divisor of the measured 50-bit distances is defined as the minimum value L of the magnetization reversal 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 80nm or less, more preferably 70nm or less, more preferably 60nm or less, still more preferably be a 50nm or less.
  • the average thickness of the magnetic layer 13 is 80 nm or less, when a ring-shaped head is used as the recording head, the magnetization can be uniformly recorded in the thickness direction of the magnetic layer 13, so that the electromagnetic conversion characteristics (for example, SNR) are improved. can do.
  • the average thickness t m of the magnetic layer 13 is preferably 30nm or more, more preferably 35nm or more, more preferably be a 40nm or more.
  • the output can be secured when an MR type head is used as the reproduction head, so that the electromagnetic conversion characteristics (for example, SNR) can be improved.
  • Numerical range of the average thickness of the magnetic layer 13 may be defined by either of the above upper limit with any of the above lower limit, preferably 30nm ⁇ t m ⁇ 80nm, more preferably 35nm ⁇ t m ⁇ 70nm, more preferably It can be a 40nm ⁇ t m ⁇ 60nm.
  • the average thickness of the magnetic layer 13 is obtained, for example, as follows.
  • the magnetic recording medium 10 is processed into flakes by a FIB (Focused Ion Beam) method or the like.
  • a carbon film and a tungsten thin film are formed as a protective film as a pretreatment for observing a TEM image of a cross section described later.
  • the carbon film is formed on the magnetic layer side surface and the back layer side surface of the magnetic recording medium 10 by a vapor deposition method, and the tungsten thin film is further formed on the magnetic layer side surface by a vapor deposition method or a sputtering method.
  • the thinning is performed along the length direction (longitudinal direction) of the magnetic recording medium 10.
  • the thinning forms a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic recording medium 10.
  • the cross section of the obtained sliced sample is observed with a transmission electron microscope (TEM) under the following conditions to obtain a TEM image.
  • the magnification and the acceleration voltage may be appropriately adjusted according to the type of the device.
  • the thickness of the magnetic layer 13 is measured at at least 10 points or more in the longitudinal direction of the magnetic recording medium 10.
  • the average value obtained by simply averaging the obtained measured values (arithmetic mean) is defined as the average thickness [nm] of the magnetic layer 13.
  • the position where the measurement is performed shall be randomly selected from the test pieces.
  • Examples of the 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 the like. Metal (metal) and the like can be mentioned, but the present invention is 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 contain hexagonal ferrite, epsilon iron oxide, or Co-containing spinel ferrite.
  • the magnetic powder is hexagonal ferrite.
  • the hexagonal ferrite may 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 plate-shaped.
  • ⁇ 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 can be, for example, 10 nm or more, preferably 12 nm or more.
  • the average aspect ratio of the magnetic powder can be preferably 1.0 or more and 3.0 or less, more preferably 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 ferrite has, for example, a hexagonal plate shape or a substantially hexagonal plate shape.
  • Hexagonal ferrites 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, for example, one or a combination of two or more selected from barium ferrite, strontium ferrite, and calcium ferrite, and barium ferrite or strontium ferrite is particularly preferable.
  • barium ferrite may further contain at least one of Sr, Pb, and Ca.
  • the strontium ferrite may further contain at least one of Ba, Pb, and Ca in addition to Sr.
  • the hexagonal ferrite can have an average composition represented by the general formula MFe 12 O 19.
  • M is, for example, at least one metal among Ba, Sr, Pb, and Ca, preferably at least one metal among 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.
  • a part of Fe may be replaced 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. It can be: The average particle size can be, for example, 10 nm or more, preferably 12 nm or more, and more preferably 15 nm or more.
  • the average particle size of the magnetic powder may be 10 nm or more and 50 nm or less, 10 nm or more and 40 nm or less, 12 nm or more and 30 nm or less, 12 nm or more and 25 nm or less, or 15 nm or more and 22 nm or less.
  • the average particle size of the magnetic powder is not more than the above upper limit value (for example, 50 nm or less, particularly 30 nm or less)
  • good electromagnetic conversion characteristics for example, SNR
  • the average particle size of the magnetic powder is equal to or more than the above lower limit value (for example, when it is 10 nm or more, preferably 12 nm or more), the dispersibility of the magnetic powder is further improved and the electromagnetic conversion characteristics (for example, SNR) are improved. 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 2. 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, aggregation of the magnetic powder can be suppressed, and further, resistance applied to the magnetic powder when the magnetic powder is vertically aligned in the process of forming the magnetic layer 13. 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 can be determined as follows.
  • the magnetic recording medium 10 to be measured is processed by a FIB (Focused Ion Beam) method or the like to be thinned.
  • a carbon film and a tungsten thin film are formed as a protective film as a pretreatment for observing a TEM image of a cross section described later.
  • the carbon film is formed on the magnetic layer side surface and the back layer side surface of the magnetic recording medium 10 by a vapor deposition method, and the tungsten thin film is further formed on the magnetic layer side surface by a vapor deposition method or a sputtering method.
  • the thinning is performed along the length direction (longitudinal direction) of the magnetic recording medium 10. That is, the thinning forms a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic recording medium 10.
  • a transmission electron microscope H-9500 manufactured by Hitachi High-Technologies Corporation
  • the cross section of the obtained flaky sample was subjected to a magnetic layer with respect to the thickness direction of the magnetic layer 13 at an acceleration voltage of 200 kV and a total magnification of 500,000 times.
  • a cross-sectional observation is performed so that the entire 13 is included, and a TEM photograph is taken.
  • 50 particles whose side surfaces are oriented toward the observation surface and whose thickness can be clearly confirmed are selected from the photographed TEM photographs. For example, FIG.
  • FIG. 9 shows an example of a TEM photograph.
  • the particles represented by a and d are selected because their thickness can be clearly confirmed.
  • the maximum plate thickness DA of each of the 50 selected particles is measured.
  • the maximum plate thickness DA obtained in this way is simply averaged (arithmetic mean) to obtain the average maximum plate thickness DA ave .
  • the plate diameter DB of each magnetic powder is measured.
  • 50 particles whose plate diameter can be clearly confirmed are selected from the TEM photographs taken.
  • the particles represented by, for example, b and c are selected because their plate diameters can be clearly confirmed.
  • the plate diameter DB of each of the 50 selected particles is measured.
  • the plate diameter DB obtained in this way is simply averaged (arithmetic mean) to obtain the average plate diameter DB ave .
  • the average plate 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.
  • average particle volume of the magnetic powder is at 2300 nm 3 or less, preferably 2000 nm 3 or less, more preferably 1600 nm 3 or less, even more preferably at 1300 nm 3 or less It is possible.
  • the average particle volume of the magnetic powder can be preferably 500 nm 3 or more, more preferably 700 nm 3 or more.
  • good electromagnetic conversion characteristics for example, SNR
  • the average particle volume of the magnetic powder is equal to or more than the above lower limit value (for example, when it is 500 nm 3 or more), the dispersibility of the magnetic powder is further improved and better electromagnetic conversion characteristics (for example, SNR) can be obtained. can.
  • the average particle volume of the magnetic powder is obtained as follows. First, as described above for the method of calculating the average particle size of the magnetic powder, the average maximum plate thickness DA ave and the average plate diameter DB ave are obtained. Next, the average particle volume V of the magnetic powder is obtained by the following formula.
  • the magnetic powder may be barium ferrite magnetic powder or strontium ferrite magnetic powder, and more preferably barium ferrite magnetic powder.
  • the barium ferrite magnetic powder contains magnetic particles of iron oxide having barium ferrite as the main phase (hereinafter referred to as "barium ferrite particles").
  • the barium ferrite magnetic powder has high reliability of data recording, for example, the coercive force does not decrease even in a high temperature and high humidity environment. From such a viewpoint, the barium ferrite magnetic powder is preferable as the magnetic powder.
  • the average particle size of the barium ferrite magnetic powder can be 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 of the magnetic layer 13 is preferably 80nm or less, more preferably 70nm or less, more preferably 60nm or less, even more preferably be 50nm or less sell.
  • the average thickness of the magnetic layer 13 is 80 nm or less, when a ring-shaped head is used as the recording head, the magnetization can be uniformly recorded in the thickness direction of the magnetic layer 13, so that the electromagnetic conversion characteristics (for example, SNR) are improved. can do.
  • the average thickness t m of the magnetic layer 13 is preferably 30nm or more, more preferably 35nm or more, more preferably be a 40nm or more.
  • the output can be secured when an MR type head is used as the reproduction head, so that the electromagnetic conversion characteristics (for example, SNR) can be improved.
  • Numerical range of the average thickness of the magnetic layer 13 may be defined by either of the above upper limit with any of the above lower limit, preferably 30nm ⁇ t m ⁇ 80nm, more preferably 35nm ⁇ t m ⁇ 70nm, more preferably It can be a 40nm ⁇ t m ⁇ 60nm.
  • the square ratio of the magnetic recording medium 10 in the thickness direction (vertical direction) can be preferably 65% or more, more preferably 67% or more, still more preferably 70% or more.
  • the magnetic powder may preferably contain a powder of nanoparticles containing ⁇ -iron oxide (hereinafter referred to as “ ⁇ -iron oxide particles”). High coercive force can be obtained even with fine particles of ⁇ iron oxide particles. It is preferable that the ⁇ -iron oxide contained in the ⁇ -iron oxide particles is preferentially crystal-oriented in the thickness direction (vertical direction) of the magnetic recording medium 10.
  • the ⁇ iron oxide particles have a spherical shape or a substantially spherical shape, or have a cubic shape or a nearly cubic shape. Since the ⁇ -iron oxide particles have the above-mentioned shape, the thickness of the medium is different when the ⁇ -iron oxide particles are used as the magnetic particles than when the hexagonal plate-shaped barium ferrite particles are used as the magnetic particles. The contact area between particles in the direction can be reduced, and aggregation of particles can be suppressed. Therefore, the dispersibility of the magnetic powder can be improved and a better SNR can be obtained.
  • the ⁇ iron oxide particles may have a core-shell type structure.
  • the ⁇ -iron oxide particles include a core portion 21 and a shell portion 22 having a two-layer structure provided around the core portion 21.
  • the shell portion 22 having a two-layer structure 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 is preferably one having ⁇ -Fe 2 O 3 crystals as the main phase, and more preferably one composed of single-phase ⁇ -Fe 2 O 3.
  • the first shell portion 22a covers at least a part of the periphery of the core portion 21. Specifically, the first shell portion 22a may partially cover the periphery of the core portion 21, or may cover the entire periphery of the core portion 21. From the viewpoint of making the exchange coupling between the core portion 21 and the first shell portion 22a sufficient and improving the magnetic characteristics, it is preferable to cover the entire surface of the core portion 21.
  • the first shell portion 22a is a so-called soft magnetic layer, and 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 contain ⁇ -iron oxide, aluminum oxide, or silicon oxide.
  • the ⁇ -iron oxide may contain, for example, at least one iron oxide of Fe 3 O 4 , Fe 2 O 3, and Fe O.
  • the ⁇ -iron oxide may be obtained by oxidizing ⁇ -Fe contained in the first shell portion 22a.
  • the ⁇ iron oxide particles have the first shell portion 22a as described above, thermal stability can be ensured. Further, since the ⁇ -iron oxide particles have the second shell portion 22b as described above, the ⁇ -iron oxide particles are exposed to the air in the manufacturing process of the magnetic recording medium 10 and before the process, and are exposed to the surface of the particles. It is possible to suppress the deterioration of the characteristics of the ⁇ iron oxide particles due to the occurrence 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 having a single-layer structure.
  • 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 having a two-layer structure.
  • the ⁇ -iron oxide particles may contain an additive instead of the core-shell structure, or may have a core-shell structure and contain an additive. In these cases, a part of Fe of the ⁇ iron oxide particles is replaced with an additive.
  • the additive is one or more selected from the group consisting of metal elements other than iron, preferably trivalent metal elements, more preferably aluminum (Al), gallium (Ga), and indium (In).
  • the ⁇ -iron oxide containing the additive is an ⁇ -Fe 2-x M x O 3 crystal (where M is a metal element other than iron, preferably a trivalent metal element, more preferably Al. , Ga, and one or more selected from the group consisting of In. X is, for example, 0 ⁇ x ⁇ 1).
  • the average particle size (average maximum particle size) of the magnetic powder can be 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 magnetization region. Therefore, a good SNR can be obtained by setting the average particle size of the magnetic powder to half or less of the shortest recording wavelength. Therefore, when the average particle size of the magnetic powder is 22 nm or less, it is good in a magnetic recording medium 10 having a high recording density (for example, a magnetic recording medium 10 configured to be able to record a signal at the shortest recording wavelength of 44 nm or less).
  • Electromagnetic conversion characteristics for example, SNR
  • the average particle size of the magnetic powder is 8 nm or more
  • the dispersibility of the magnetic powder is further improved, and more excellent electromagnetic conversion characteristics (for example, SNR) can be obtained.
  • the average aspect ratio of the magnetic powder can be 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 aligned in the process of forming the magnetic layer 13 is suppressed. be able to. Therefore, the vertical orientation of the magnetic powder can be improved.
  • the average particle size and average aspect ratio of the magnetic powder can be determined as follows.
  • the magnetic recording medium 10 to be measured is processed by a FIB (Focused Ion Beam) method or the like to be thinned.
  • a carbon film and a tungsten thin film are formed as a protective film as a pretreatment for observing a TEM image of a cross section described later.
  • the carbon film is formed on the magnetic layer side surface and the back layer side surface of the magnetic recording medium 10 by a vapor deposition method, and the tungsten thin film is further formed on the magnetic layer side surface by a vapor deposition method or a sputtering method.
  • the flaking is performed along the length direction (longitudinal direction) of the magnetic recording medium 10. That is, the thinning forms a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic recording medium 10.
  • a transmission electron microscope H-9500 manufactured by Hitachi High-Technologies Corporation
  • the cross section of the obtained flaky sample was subjected to a magnetic layer with respect to the thickness direction of the magnetic layer 13 at an acceleration voltage of 200 kV and a total magnification of 500,000 times.
  • a cross-sectional observation is performed so that the entire 13 is included, and a TEM photograph is taken.
  • 50 particles whose shape can be clearly confirmed are selected from the photographed TEM photographs, and the major axis length DL and minor axis length DS of each particle are measured.
  • the major axis length DL means the maximum distance (so-called maximum ferret diameter) between two parallel lines drawn from all angles so as to be in contact with the contour of each particle.
  • the minor axis length DS means the maximum length of the particles in the direction orthogonal to the major axis (DL) of the particles.
  • the major axis length DLs of the measured 50 particles are simply averaged (arithmetic mean) to obtain the average major axis length DL ave .
  • the average major axis length DL ave thus obtained is defined as the average particle size of the magnetic powder.
  • the average minor axis length DS ave of the measured 50 particles is simply averaged (arithmetic mean) to obtain the average minor axis length DS ave. Then, the average aspect ratio (DL ave / DS ave ) of the particles is obtained from the average major axis length DL ave and the average minor axis length DS ave.
  • the average particle volume of the magnetic powder is at 2300 nm 3 or less, preferably 1600 nm 3 or less, more preferably be a 1300 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.
  • good electromagnetic conversion characteristics for example, SNR
  • the average particle volume of the magnetic powder is equal to or more than the above lower limit value (for example, when it is 500 nm 3 or more), the dispersibility of the magnetic powder is further improved and better electromagnetic conversion characteristics (for example, SNR) can be obtained. can.
  • the average particle volume of the magnetic powder can be obtained as follows.
  • the magnetic recording medium 10 is processed into flakes by a FIB (Focused Ion Beam) method or the like.
  • a carbon film and a tungsten thin film are formed as a protective film as a pretreatment for observing a TEM image of a cross section described later.
  • the carbon film is formed on the magnetic layer side surface and the back layer side surface of the magnetic recording medium 10 by a vapor deposition method, and the tungsten thin film is further formed on the magnetic layer side surface by a vapor deposition method or a sputtering method.
  • the thinning is performed along the length direction (longitudinal direction) of the magnetic recording medium 10. That is, the thinning forms a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic recording medium 10.
  • the obtained flaky sample contains the entire magnetic layer 13 with respect to the thickness direction of the magnetic layer 13 at an acceleration voltage of 200 kV and a total magnification of 500,000 times.
  • a cross-sectional observation is performed so as to obtain a TEM photograph.
  • the magnification and the acceleration voltage may be appropriately adjusted according to the type of the device.
  • 50 particles whose shape is clear are selected from the photographed TEM photograph, and the side length DC of each particle is measured.
  • the side length DCs of the 50 measured particles are simply averaged (arithmetic mean) to obtain the average side length DC ave .
  • the average particle volume V ave (particle volume) of the magnetic powder is obtained from the following formula using the average side length DC ave.
  • V ave DC ave 3
  • the average thickness t m of the magnetic layer 13 is preferably 80nm or less, more preferably 70nm or less, more preferably 60nm or less, still more preferably be a 50nm or less .
  • the average thickness of the magnetic layer 13 is 80 nm or less, when a ring-shaped head is used as the recording head, the magnetization can be uniformly recorded in the thickness direction of the magnetic layer 13, so that the electromagnetic conversion characteristics (for example, SNR) are improved. can do.
  • the average thickness t m of the magnetic layer 13 is preferably 30nm or more, more preferably 35nm or more, more preferably be a 40nm or more.
  • the output can be secured when an MR type head is used as the reproduction head, so that the electromagnetic conversion characteristics (for example, SNR) can be improved.
  • Numerical range of the average thickness of the magnetic layer 13 may be defined by either of the above upper limit with any of the above lower limit, preferably 30nm ⁇ t m ⁇ 80nm, more preferably 35nm ⁇ t m ⁇ 70nm, more preferably It can be a 40nm ⁇ t m ⁇ 60nm.
  • the square ratio of the magnetic recording medium 10 in the thickness direction (vertical direction) can be preferably 65% or more, more preferably 67% or more, still more preferably 70% or more.
  • the magnetic powder may include powders of nanoparticles containing Co-containing spinel ferrite (hereinafter also referred to as "cobalt ferrite particles"). That is, the magnetic powder can be a cobalt ferrite magnetic powder.
  • the cobalt ferrite particles preferably have uniaxial crystal anisotropy.
  • the cobalt ferrite magnetic particles have, for example, a cubic shape or a substantially cubic shape.
  • the Co-containing spinel ferrite may further contain one or more selected from the group consisting of Ni, Mn, Al, Cu, and Zn in addition to Co.
  • Cobalt ferrite has, for example, an average composition represented by the following formula (1).
  • Co x M y Fe 2 O z ⁇ (1) M is one or more metals selected from the group consisting of, for example, Ni, Mn, Al, Cu, and Zn.
  • X is 0.4 ⁇ x ⁇ 1.0.
  • Y is a value within the range of 0 ⁇ y ⁇ 0.3.
  • x and y satisfy the relationship of (x + y) ⁇ 1.0.
  • Z is 3 ⁇ z ⁇ . It is a value in the range of 4.
  • a part of Fe may be replaced with another metal element.
  • the average particle size of the cobalt ferrite magnetic powder can be preferably 25 nm or less, more preferably 23 nm or less.
  • the average particle size of the magnetic powder can be 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 having a 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 more excellent electromagnetic conversion characteristics (for example, SNR) can be obtained.
  • the average aspect ratio and the average particle size of the magnetic powder are determined by the same method as when the magnetic powder contains ⁇ -iron oxide particles.
  • the average particle volume of the magnetic powder is at 2300 nm 3 or less, preferably 1600 nm 3 or less, more preferably be a 1300 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.
  • good electromagnetic conversion characteristics for example, SNR
  • the average particle volume of the magnetic powder is equal to or more than the above lower limit value (for example, when it is 500 nm 3 or more), the dispersibility of the magnetic powder is further improved and better electromagnetic conversion characteristics (for example, SNR) can be obtained. can.
  • the average thickness t m of the magnetic layer 13 is preferably 80nm or less, more preferably 70nm or less, more preferably 60nm or less, even more preferably be 50nm or less sell.
  • the average thickness of the magnetic layer 13 is 80 nm or less, when a ring-shaped head is used as the recording head, the magnetization can be uniformly recorded in the thickness direction of the magnetic layer 13, so that the electromagnetic conversion characteristics (for example, SNR) are improved. can do.
  • the average thickness t m of the magnetic layer 13 is preferably 30nm or more, more preferably 35nm or more, more preferably be a 40nm or more.
  • the output can be secured when an MR type head is used as the reproduction head, so that the electromagnetic conversion characteristics (for example, SNR) can be improved.
  • Numerical range of the average thickness of the magnetic layer 13 may be defined by either of the above upper limit with any of the above lower limit, preferably 30nm ⁇ t m ⁇ 80nm, more preferably 35nm ⁇ t m ⁇ 70nm, more preferably It can be a 40nm ⁇ t m ⁇ 60nm.
  • the square ratio of the magnetic recording medium 10 in the thickness direction (vertical direction) can be preferably 65% or more, more preferably 67% or more, still more preferably 70% or more.
  • the binder a resin having a structure in which a cross-linking reaction is performed on a polyurethane resin, a vinyl chloride resin, or the like is preferable.
  • the binder is not limited to these, and other resins may be appropriately blended depending on the physical characteristics required for the magnetic recording medium 10.
  • the resin to be blended is not particularly limited as long as it is a resin generally used in the coating type magnetic recording medium 10.
  • binder examples include polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, and acrylic acid ester-acrylonitrile copolymer.
  • Acrylic acid ester-vinyl chloride-vinylidene chloride copolymer acrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-vinyl chloride copolymer, methacrylic acid ester-ethylene Polymers, polyfluorinated vinyl, vinylidene chloride-acrylonitrile copolymers, acrylonitrile-butadiene copolymers, polyamide resins, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitro) One or a combination of two or more selected from cellulose), styrene-butadiene copolymers, polyester resins, amino resins, and synthetic rubbers can be used.
  • thermosetting resin or a reactive resin may be used as the binder.
  • thermosetting resins or reactive resins include phenol resins, epoxy resins, urea resins, melamine resins, alkyd resins, silicone resins, polyamine resins, urea formaldehyde resins and the like.
  • M in the formula is a hydrogen atom or an alkali metal such as lithium, potassium, and sodium.
  • polar functional group -NR1R2, -NR1R2R3 + X - as the side chain type having an end group, and,> NR1R2 + X - include those of the main chain type.
  • R1, R2, and R3 in the formula are hydrogen atoms or hydrocarbon groups independently of each other, and X ⁇ is, for example, a halogen element ion such as fluorine, chlorine, bromine, or iodine, or an inorganic or organic substance. It is an ion.
  • examples of the polar functional group include -OH, -SH, -CN, and an epoxy group. The amount of these polar functional groups introduced into the binder is preferably 10 -1 to 10 -8 mol / g, more preferably 10 2-1 to 10 -6 mol / g.
  • the magnetic layer may contain a lubricant.
  • the lubricant may be, for example, one or more selected from fatty acids and / or fatty acid esters, and may preferably contain both fatty acids and fatty acid esters.
  • the fatty acid is preferably a compound represented by the following general chemical formula (1) or general chemical formula (2).
  • the fatty acid ester is preferably a compound represented by the following general chemical formula (3) or general chemical formula (4).
  • the fatty acid ester may contain one or both of the compound represented by the following general chemical formula (3) and the compound represented by the general chemical formula (4).
  • the lubricant is represented by one or both of the compound represented by the general chemical formula (1) and the compound represented by the general chemical formula (2), the compound represented by the general chemical formula (3), and the compound represented by the general chemical formula (4).
  • the compound represented by the general chemical formula (1) 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.
  • 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. Examples thereof include octyl, isooctyl stearate, and octyl myristate.
  • antistatic agent examples include carbon black, natural surfactant, nonionic surfactant, cationic surfactant and the like.
  • polishing agent examples include ⁇ -alumina, ⁇ -alumina, ⁇ -alumina, silicon carbide, chromium oxide, cerium oxide, ⁇ -iron oxide, corundum, silicon nitride, titanium carbide, and oxidation having an pregelatinization rate of 90% or more.
  • Needle-shaped ⁇ obtained by dehydrating and annealing raw materials of 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 oxide, and if necessary, surface-treated them with aluminum and / or silica.
  • the curing agent examples include polyisocyanate and the like.
  • the polyisocyanate examples include aromatic polyisocyanates such as an adduct of tolylene diisocyanate (TDI) and an active hydrogen compound, and aliphatic polyisocyanates such as an adduct of hexamethylene diisocyanate (HMDI) and an active hydrogen compound. Can be mentioned.
  • the weight average molecular weight of these polyisocyanates is preferably in the range of 100 to 4500.
  • rust preventive agent examples include phenols, naphthols, quinones, heterocyclic compounds containing a nitrogen atom, heterocyclic compounds containing an oxygen atom, and heterocyclic compounds containing a sulfur atom.
  • non-magnetic reinforcing particles for example, aluminum oxide ( ⁇ , ⁇ or ⁇ alumina), chromium oxide, silicon oxide, diamond, garnet, emery, boron nitride, titanium carbide, silicon carbide, titanium carbide, titanium oxide (rutyl type or Anatase type titanium oxide) and the like.
  • the base layer 12 is a non-magnetic layer containing a non-magnetic powder and a binder.
  • the base layer 12 may further contain at least one additive such as a lubricant, an antistatic agent, a curing agent, and a rust preventive, if necessary.
  • the average thickness of the base layer 12 can be preferably 0.6 ⁇ m or more and 2.0 ⁇ m or less, and more preferably 0.6 ⁇ m or more and 1.4 ⁇ m or less. More preferably, it can be 0.6 ⁇ m or more and 1.0 ⁇ m or less.
  • the average thickness of the base layer 12 is obtained in the same manner as the average thickness of the magnetic layer 13. However, the magnification of the TEM image is appropriately adjusted according to the thickness of the base layer 12.
  • the base layer 12 is provided between the magnetic layer 13 and the base layer 11, and the average thickness of the base layer 12 may be 2.0 ⁇ m or less.
  • the non-magnetic powder contains, for example, at least one of inorganic particle powder and organic particle powder. Further, the non-magnetic powder may contain carbon powder such as carbon black. In addition, one kind of non-magnetic powder may be used alone, or two or more kinds of non-magnetic powder may be used in combination.
  • Inorganic particles include, for example, metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, metal sulfides and the like.
  • Examples of the shape of the non-magnetic powder include various shapes such as needle shape, spherical shape, cube shape, and plate shape, but the shape is not limited to these shapes.
  • the back layer 14 may contain a binder and a non-magnetic powder.
  • the back layer 14 may further contain at least one additive such as a lubricant, a curing agent and an antistatic agent, if necessary.
  • a lubricant such as a lubricant, a curing agent and an antistatic agent, if necessary.
  • the above description of the binder and the non-magnetic powder contained in the base layer 12 also applies to the binder and the non-magnetic powder contained in the back layer.
  • the average particle size of the non-magnetic powder can be 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 obtained in the same manner as the average particle size of the magnetic powder described above.
  • the non-magnetic powder may contain a non-magnetic powder having a particle size distribution of 2 or more.
  • the average thickness of the back layer 14 (also referred to as “average thickness t b ” or “t b ” in the present specification) is preferably 0.6 ⁇ m or less. It can be more preferably 0.4 ⁇ m or less, and even more preferably 0.3 ⁇ m or less.
  • the lower limit of the average thickness t b of the back layer 14 is not particularly limited, but 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, and the average of the back layers 14 is provided.
  • the thickness may be 0.6 ⁇ m or less.
  • the average thickness of the magnetic recording medium 10 (also referred to as "average thickness t T " or "t T " in the present specification is preferably 5.8 ⁇ m or less, more preferably 5.6 ⁇ m or less, more preferably 5.5 ⁇ m or less. More preferably 5.4 ⁇ m or less, preferably 5.3 ⁇ m or less, more preferably 5.2 ⁇ m or less, even more preferably 5.1 ⁇ m or less, 5.0 ⁇ m or less, 4.8 ⁇ m or less, or 4.6 ⁇ m or less. It is possible.
  • the recording capacity that can be recorded in one data cartridge is increased as compared with the conventional case.
  • the lower limit of the average thickness t T of the magnetic recording medium 10 is not particularly limited, but is, for example, 3.5 ⁇ m ⁇ t T.
  • the average thickness t T of the magnetic recording medium 10 is obtained as follows. First, a magnetic recording medium 10 having a width of 1/2 inch is prepared, and the magnetic recording medium 10 is cut out to a length of 250 mm to prepare a sample. Next, using a laser holo gauge (LGH-110C) manufactured by Mitutoyo as a measuring device, the thickness of the sample is measured at 5 or more points, and the measured values are simply averaged (arithmetic mean) and averaged. Calculate the value t T [ ⁇ m]. The measurement position shall be randomly selected from the sample.
  • LGH-110C laser holo gauge manufactured by Mitutoyo
  • a Young's modulus than the base layer 11 is more of a coating film for forming the magnetic layer 13 and the underlayer 12 (The average thickness of the magnetic layer 13 + the average thickness of the base layer 12) / ( The ratio of the average thickness of the base layer 11) can be preferably 0.15 or more, more preferably 0.16 or more. The ratio may be, for example, preferably 0.35 or less, more preferably 0.33 or less, still more preferably 0.30 or less.
  • the ratio of (average thickness of the magnetic layer 13 + average thickness of the base layer 12 + average thickness of the back layer 14) / (average thickness of the magnetic recording medium 10) is preferably 0.17. As mentioned above, it can be more preferably 0.18 or more, still more preferably 0.19 or more. The ratio may be, for example, preferably 0.30 or less, more preferably 0.28 or less, still more preferably 0.25 or less.
  • the magnetic interaction ⁇ M is obtained as follows. First, both sides of the magnetic recording medium 10 are reinforced with tape, and then punched out with a punch having a diameter of 6 mm to prepare a measurement sample. At this time, marking is performed with an arbitrary non-magnetic ink so that the longitudinal direction (traveling direction) of the magnetic recording medium can be recognized. When the sample was attached to the sample rod, it was attached so that the longitudinal direction of the magnetic recording medium (tape) was perpendicular to the sample rod. Then, the measurement sample is degaussed using a degausser.
  • the specific operation procedure is as follows. (1) Turn on the power (Model 642 Electromagnet Power Supply Lake Shore) of the Vibrating Sample Magnetometer (VSM) (VSM Vibrating Sample Magnetometer (VSM) 7400-S series manufactured by Lake Shore), and turn on the cooling water chiller (Chiller of cooling water (Model 642 Electromagnet Power Supply Lake Shore). Start the circulation device) to operate the device. (2) Turn on the power of the vibration sample magnetometer. (3) Launch the IDEAS-VSM version 4 software. (4) Wipe the sample holder with ethanol, attach double-sided tape to the sample holder, and attach a standard Ni sample (70.6 mg, 3.876 emu) on it. (5) Turn on the power of the ionizer and remove the static electricity from the sample holder.
  • the residual magnetization Ir (H) measured by AC demagnetization is measured by the following method.
  • AC degaussing is performed to set the external magnetic field to 0Oe.
  • Ir 200Oe
  • Ir 400Oe
  • Is performed every 200 Oe to increase the magnetic field to 6 kOe.
  • the remanent magnetization when the applied magnetic field was 6 kOe was defined as Ir ( ⁇ ).
  • the residual magnetization Id (H) measured by direct current demagnetization is measured by the following method.
  • DC demagnetization is performed by applying an external magnetic field of 10 kOe to set the external magnetic field to 0 Oe.
  • Id the residual magnetization when the magnetic field was applied in the direction opposite to the direction of the magnetic field where the DC demagnetization was performed and then returned to 0Oe was Id (200Oe).
  • the remanent magnetization when returned is set to Id (400 Oe), and these operations are performed every 200 Oe to increase the magnetic field to 6 kOe.
  • each ⁇ M (H) is calculated and calculated by the equation (1) using each of the obtained Id (H), each Ir (H), and Ir ( ⁇ ).
  • the minimum value of the obtained ⁇ M (H) is defined as the magnetic interaction ⁇ M of the measurement sample.
  • Md (H) Id (H) / Id (0)
  • Mr (H) ⁇ Ir (H) -Ir (0) ⁇ / ⁇ Ir ( ⁇ ) -Ir (0) ⁇ . do. This is because Ir ( ⁇ ) ⁇ Id (0) does not completely match. This is also because Ir (0) cannot be completely degaussed and does not become 0.
  • thermal stability K u V act / k B T of the magnetic recording medium of the present technology is preferably 63 or more, more preferably 70 or more, more preferably 80 or more , Even more preferably 90 or more.
  • the magnetic recording medium of the present technology contains magnetic powder having a small average particle volume, it has such high thermal stability, and thus is excellent in storage stability.
  • Thermostable K u V act / k B T of the magnetic recording medium of the present technology preferably may be a 150 or less.
  • Thermostable K u V act / k B T of the magnetic recording medium for example, during the synthesis process of the magnetic powder can be achieved by stabilizing the state of the material after glass melting.
  • the melting temperature is arbitrarily set at the time of glass melting, and by raising the melting temperature at this time to a high temperature, the amorphous state of the material after glass melting can be made more uniform, and thus the material state can be stabilized. ..
  • the thermal stability K u V act / k B T is also by improving the vertical alignment degree can be adjusted.
  • H r (t ') H 0 [1- ⁇ k B T / (K u V act) ln (f 0 t' / 0.693) n ⁇ ] (However, H r : residual magnetic field, t': magnetization decay amount, H 0 : magnetic field change amount, k B : Boltzmann constant, T: absolute temperature, Ku : magnetocrystalline anisotrophic constant, V act : magnetic powder Activated volume, f 0 : frequency factor, n: coefficient)
  • the (a) residual magnetic field H r , (b) magnetization attenuation t', and (c) magnetic field change amount H 0 are obtained as follows. Further, the following numerical values are used for (d) frequency factor f 0 and (e) coefficient n.
  • the absolute temperature T is 25 ° C.
  • the residual magnetic field H r can be measured by Hayama's pulse VSM "HR-PVSM20". For the measurement, a sample obtained by stacking three magnetic recording media 10 with double-sided tape and then punching them with a ⁇ 6 mm punch is used. Before starting the measurement, a magnetic field of 6358 [Oe] is applied to the sample to magnetically orient the sample in one direction.
  • the amount of magnetization decay is measured by an applied vibration sample magnetometer (VSM). Then, the magnetization attenuation t'is calculated from the magnetization attenuation using the Flemish equation described in the following reference (Reference: IPJ Flanders and MP Sharrock, “An analysis of time-dependent magnetization and coercivity and of theirs). relationship to print-through in recording tapes, ”J. Appl. Phys., Vol. 62, pp. 2918-2928, 1987.).
  • the "coercive force Hc” means the coercive force Hc in the orientation direction of the magnetic powder.
  • the "coercive force Hc” means the coercive force Hc1 in the vertical direction.
  • the "coercive force Hc” means the coercive force Hc2 in the longitudinal direction.
  • the "external magnetic field under three conditions” is a magnetic field having a coercive force Hc or more (a magnetic field that can obtain positive magnetization), a magnetic field near the coercive force Hc (a magnetic field that can obtain a magnetization close to 0), and a magnetic field less than the coercive force Hc. It means the magnetic field of (the magnetic field where negative magnetization is obtained).
  • n 0.77.
  • the square ratio Rs2 in the vertical direction (thickness direction) of the magnetic recording medium of the present technology can be preferably 65% or more, more preferably 67% or more, and even more preferably 70% or more.
  • the vertical orientation of the magnetic powder becomes sufficiently high, so that a more excellent SNR can be obtained. Therefore, better electromagnetic conversion characteristics can be obtained.
  • the shape of the servo signal is improved, which makes it easier to control the drive side.
  • the vertical orientation of the magnetic recording medium may mean that the square ratio Rs2 of the magnetic recording medium is within the above numerical range (for example, 65% or more).
  • the square ratio Rs2 in the vertical direction is obtained as follows. First, the magnetic recording medium 10 is punched to a size of 6.25 mm ⁇ 64 mm and then folded in three to prepare a measurement sample of 6.25 mm ⁇ 8 mm. Then, the MH hysteresis loop of the measurement sample (the entire magnetic recording medium 10) corresponding to the vertical direction (thickness direction) of the magnetic recording medium 10 is measured using the VSM. Next, the coating film (base layer 12, magnetic layer 13, back layer 14, etc.) is wiped off with acetone, ethanol, or the like, leaving only the base layer 11.
  • the obtained base layer 11 is punched to 6.25 mm ⁇ 64 mm, and then folded in three to obtain a 6.25 mm ⁇ 8 mm sample for background correction (hereinafter, simply “correction sample”). Then, the MH hysteresis loop of the correction sample (base layer 11) corresponding to the vertical direction of the base layer 11 (vertical direction of the magnetic recording medium 10) is measured using VSM.
  • a high-sensitivity vibration sample magnetometer manufactured by Toei Kogyo Co., Ltd. "VSM-P7-15 type" is used.
  • the measurement conditions are: measurement mode: full loop, maximum magnetic field: 15 kOe, magnetic field step: 40 bits, Time constant of Locking amp: 0.3 sec, Waiting time: 1 sec, MH average number: 20.
  • the M-H of the measurement sample (whole magnetic recording medium 10)
  • background correction is performed, and the MH hysteresis loop after background correction is obtained.
  • the measurement / analysis program attached to the "VSM-P7-15 type" is used for the calculation of this background correction.
  • the square ratio Rs1 in the longitudinal direction (traveling direction) of the magnetic recording medium 10 can be preferably 35% or less, more preferably 27% or less, and even more preferably 20% or less.
  • the vertical orientation of the magnetic powder becomes sufficiently high, so that a more excellent SNR can be obtained. Therefore, better electromagnetic conversion characteristics can be obtained.
  • the shape of the servo signal is improved, making it easier to control the drive side.
  • the vertical orientation of the magnetic recording medium may mean that the square ratio Rs1 in the longitudinal direction of the magnetic recording medium is within the above numerical range (for example, 35% or less). ..
  • Magnetic recording media according to the present technology are preferably vertically oriented.
  • the square ratio Rs1 in the longitudinal direction is obtained in the same manner as the square ratio Rs2 in the vertical direction except that the MH hysteresis loop is measured in the longitudinal direction (traveling direction) of the magnetic recording medium 10 and the base layer 11.
  • the square ratio Rs2 in the vertical direction and the square ratio Rs1 in the longitudinal direction are, for example, the strength of the magnetic field applied to the magnetic layer forming paint, the application time of the magnetic field to the magnetic layer forming paint, and the magnetic powder in the magnetic layer forming paint.
  • the desired value is set by adjusting the dispersed state of the above or the concentration of the solid content in the coating material for forming the magnetic layer. Specifically, for example, as the strength of the magnetic field is increased, the square ratio Rs1 in the longitudinal direction becomes smaller, whereas the square ratio Rs2 in the vertical direction becomes larger. Further, as the application time of the magnetic field is lengthened, the square ratio Rs1 in the longitudinal direction becomes smaller, whereas the square ratio Rs2 in the vertical direction becomes larger.
  • the square ratio Rs1 in the longitudinal direction becomes smaller, while the square ratio Rs2 in the vertical direction becomes larger. Further, as the concentration of the solid content is lowered, the square ratio Rs1 in the longitudinal direction becomes smaller, whereas the square ratio Rs2 in the vertical direction becomes larger.
  • the above adjustment method may be used alone or in combination of two or more.
  • the saturation magnetization amount Ms of the magnetic recording medium in the longitudinal direction is preferably 3.0 ⁇ 10 -3 emu ⁇ Ms. More preferably, it may be 3.2 ⁇ 10 -3 emu ⁇ Ms, and even more preferably 3.4 ⁇ 10 -3 emu ⁇ Ms.
  • the saturation magnetization amount Ms is obtained in the same manner as the measurement of the square ratio Rs1 in the longitudinal direction described above.
  • the magnetic recording medium of the present technology may have an SNR of preferably 0.3 dB or more, more preferably 0.5 dB or more, from the viewpoint of obtaining good electromagnetic conversion characteristics.
  • a coating material for forming an underlayer is prepared by kneading and dispersing a non-magnetic powder, a binder and the like in a solvent.
  • a paint for forming a magnetic layer is prepared by kneading and dispersing a magnetic powder, a binder and the like in a solvent.
  • the following solvent, dispersion device and kneading device can be used.
  • Examples of the solvent used for preparing the above-mentioned paint include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, alcohol solvents such as methanol, ethanol and propanol, methyl acetate, ethyl acetate, butyl acetate and propyl acetate.
  • ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone
  • alcohol solvents such as methanol, ethanol and propanol, methyl acetate, ethyl acetate, butyl acetate and propyl acetate.
  • Ester solvents such as ethyl lactate and ethylene glycol acetate, ether solvents such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran and dioxane, aromatic hydrocarbon solvents such as benzene, toluene and xylene, methylene chloride, ethylene chloride, Examples thereof include halogenated hydrocarbon solvents such as carbon tetrachloride, chloroform and chlorobenzene. These may be used alone or may be mixed appropriately.
  • a continuous twin-screw kneader for example, a continuous twin-screw kneader, a continuous twin-screw kneader that can be diluted in multiple stages, a kneader, a pressure kneader, a roll kneader, or the like can be used.
  • the device is not limited to these devices.
  • disperser used for the above-mentioned paint preparation for example, a roll mill, a ball mill, a horizontal sand mill, a vertical sand mill, a spike mill, a pin mill, a tower mill, a pearl mill (for example, "DCP mill” manufactured by Eirich), a homogenizer, and an ultrasonic mill.
  • Dispersing devices such as a sound wave disperser can be used, but the device is not particularly limited to these devices. It should be noted that the extension of the dispersion time in the preparation of the paint for forming the magnetic layer tends to increase the magnetic interaction ⁇ M and improve the electromagnetic conversion characteristics.
  • the base layer 12 is formed by applying the base layer forming paint to one main surface of the base layer 11 and drying it. Subsequently, the magnetic layer forming paint is applied onto the base layer 12 and dried to form the magnetic layer 13 on the base layer 12.
  • the magnetic powder may be magnetically oriented in the thickness direction of the base layer 11 by a solenoid coil. Further, at the time of drying, for example, the magnetic powder may be magnetically oriented in the traveling direction (longitudinal direction) of the base layer 11 by a solenoid coil, and then the magnetic field may be oriented in the thickness direction of the base layer 11.
  • the magnetic interaction ⁇ M tends to be small (the absolute value is large), and the thermal stability tends to be better. There is. Moreover, the square ratio Rs can be improved by such vertical orientation. Therefore, the degree of vertical orientation of the magnetic powder can be improved.
  • the back layer 14 is formed on the other main surface of the base layer 11. As a result, the magnetic recording medium 10 is obtained.
  • Magnetic interaction ⁇ M indicates the degree of aggregation of magnetic powder particles in the magnetic layer.
  • Factors that affect the degree of aggregation include the average particle volume of magnetic powder particles in the magnetic layer, dispersion treatment, orientation treatment, and the like.
  • the magnetic interaction ⁇ M of the magnetic layer can be controlled within the above numerical range by setting the average particle volume to a specific value or less and vertically aligning the magnetic powder particles.
  • the square ratios Rs1 and Rs2 are, for example, the strength of the magnetic field applied to the coating film of the magnetic layer forming paint, the concentration of solid content in the magnetic layer forming paint, and the magnetic layer forming.
  • the desired value is set by adjusting the drying conditions (drying temperature and drying time) of the coating film of the paint.
  • the strength of the magnetic field applied to the coating film is preferably 2 times or more and 3 times or less the coercive force of the magnetic powder.
  • the square ratio Rs it is also effective to magnetize the magnetic powder before the paint for forming the magnetic layer enters the alignment device for magnetically aligning the magnetic powder.
  • the above-mentioned method for adjusting the square ratio Rs may be used alone or in combination of two or more.
  • the obtained magnetic recording medium 10 is rewound around the core and cured. Finally, after performing calendar processing on the magnetic recording medium 10, it is cut into a predetermined width (for example, 1/2 inch width). From the above, the target elongated magnetic recording medium 10 can be 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 / playback device 30 includes a plurality of magnetic recording cartridges. It may have a configuration capable of loading 10A.
  • the recording / playback 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 data supplied from these information processing devices is stored in a magnetic recording cartridge. It is configured to be recordable at 10A.
  • the shortest recording wavelength of the recording / reproducing device 30 can be 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 / playback device 30 includes a spindle 31, a reel 32 on the recording / playback device side, a spindle drive device 33, a reel drive device 34, a plurality of guide rollers 35, a head unit 36, and the like. It includes a communication interface (hereinafter, I / F) 37 and a control device 38.
  • I / F communication interface
  • the spindle 31 is configured so that the magnetic recording cartridge 10A can be mounted.
  • the magnetic recording cartridge 10A conforms to the LTO (Linear Tape Open) standard, and rotatably accommodates a single reel 10C in which the magnetic recording 10 is wound in a cartridge case 10B.
  • a V-shaped servo pattern is pre-recorded on the magnetic recording medium 10 as a servo signal.
  • the reel 32 is configured so that the tip of the magnetic recording medium 10 drawn from the magnetic recording cartridge 10A can be fixed.
  • the spindle drive device 33 is a device that rotationally drives the spindle 31.
  • the reel drive device 34 is a device that rotationally drives the reel 32.
  • the spindle drive device 33 and the reel drive device 34 rotate the spindle 31 and the reel 32 to drive the magnetic recording medium 10 to travel.
  • the guide roller 35 is a roller for guiding the traveling of the magnetic recording medium 10.
  • the head unit 36 includes a plurality of recording heads for recording a data signal on the magnetic recording medium 10, a plurality of reproduction heads for reproducing the data signal recorded on the magnetic recording medium 10, and the magnetic recording medium 10. It is provided with a plurality of servo heads for reproducing the recorded servo signal.
  • a ring type head can be used, but the type of the recording head is not limited to this.
  • the communication I / F 37 is for communicating with an information processing device such as a server 41 and a PC 42, and is connected to the network 43.
  • the control device 38 controls the entire recording / playback device 30.
  • the control device 38 records the data signal supplied from the information processing device on the magnetic recording medium 10 by the head unit 36 in response to the request of 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 and supplies the data signal to the information processing device in response to the request of the information processing device such as the server 41 and the PC 42.
  • the magnetic recording cartridge 10A is mounted on the recording / playback device 30, the tip of the magnetic recording medium 10 is pulled out, and the tip of the magnetic recording medium 10 is transferred to the reel 32 via a plurality of guide rollers 35 and the head unit 36. It is attached to the reel 32.
  • the spindle drive device 33 and the reel drive device 34 are driven by the control of the control device 38, and the magnetic recording medium 10 is driven from the reel 10C to the reel 32.
  • the spindle 31 and the reel 32 are rotated in the same direction.
  • the head unit 36 records the information on the magnetic recording medium 10 or reproduces the information recorded on the magnetic recording medium 10.
  • the head unit 36 When the magnetic recording medium 10 is rewound on the reel 10C, the spindle 31 and the reel 32 are rotationally driven in the opposite direction to the above, so that the magnetic recording medium 10 travels from the reel 32 to the reel 10C. .. At the time of this rewinding, the head unit 36 also records the information on the magnetic recording medium 10 or reproduces the information recorded on the magnetic recording medium 10.
  • the present technology also provides a magnetic recording cartridge (also referred to as a tape cartridge) including a magnetic recording medium according to the present technology.
  • the magnetic recording medium may be wound around a reel, for example.
  • the magnetic recording cartridge stores, for example, information received from a communication unit that communicates with a recording / playback device, a storage unit, and the recording / playback device via the communication unit in the storage unit, and the recording / playback device.
  • a control unit that reads information from the storage unit and transmits the information to the recording / playback device via the communication unit may be provided in response to the request.
  • the information may include adjustment information for adjusting the tension applied in the longitudinal direction of the magnetic recording medium.
  • the adjustment information may include, for example, dimensional information in the width direction at a plurality of positions in the longitudinal direction of the magnetic recording medium.
  • the dimensional information in the width direction is acquired in the dimensional information at the time of manufacturing (initial stage after manufacturing) of the magnetic recording medium described in the following [Cartridge memory configuration] and / or in the recording and / or reproduction processing of the magnetic recording medium. It may be the dimensional information to be obtained.
  • FIG. 13 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 is a magnetic tape (tape-shaped magnetic recording medium) inside a cartridge case 10B composed of a lower shell 212A and an upper shell 212B.
  • a slide door 217 that opens and closes the tape outlet 212C provided on the cartridge case 10B across the cartridge case, a door spring 218 that urges the slide door 217 to the closed position of the tape outlet 212C, and a light protector to prevent erroneous erasure. It includes 219 and a cartridge memory 211.
  • the reel 10C has a substantially disk shape having 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 in the vicinity of one corner of the cartridge 10A. In a state where the cartridge 10A is loaded in the recording / reproducing device 30, the cartridge memory 211 faces the reader / writer (not shown) of the recording / reproducing device 30.
  • the cartridge memory 211 communicates with the recording / reproducing device 30, specifically, a reader / writer (not shown) in a wireless communication standard compliant with the LTO standard.
  • FIG. 14 is a block diagram showing an example of the configuration of the cartridge memory 211.
  • the cartridge memory 211 generates and rectifies using an induced electromotive force from an antenna coil (communication unit) 331 that communicates with a reader / writer (not shown) and a radio wave received by the antenna coil 331 according to a specified communication standard.
  • the rectification / power supply circuit 332 that generates the power supply
  • the clock circuit 333 that also generates a clock from the radio waves received by the antenna coil 331 using the induced electromotive force, and the detection of the radio waves received by the antenna coil 331 and the antenna coil 331.
  • a controller composed of a detection / modulation circuit 334 that modulates the signal to be transmitted and a logic circuit or the like for discriminating commands and data from the digital signals extracted from the detection / modulation circuit 334 and processing them.
  • the cartridge memory 211 includes a capacitor 337 connected in parallel to the antenna coil 331, and a resonance circuit is formed by the antenna coil 331 and the capacitor 337.
  • the memory 336 stores information and the like related to the cartridge 10A.
  • the memory 336 is a non-volatile memory (NVM).
  • the storage capacity of the memory 336 is preferably about 32 KB or more. For example, if the cartridge 10A complies with the LTO-9 standard or the LTO-10 standard, the memory 336 has a storage capacity of about 32KB.
  • 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 the LTO standard cartridge memory before LTO 8 (hereinafter referred to as “conventional cartridge memory”), and is used for storing information conforming to the LTO standard before LTO 8.
  • the area Information conforming to the LTO standard before LTO8 is, for example, manufacturing information (for example, a unique number of the cartridge 10A, etc.), usage history (for example, the number of times the tape is pulled out (Thread Count), etc.).
  • the second storage area 336B corresponds to an extended storage area with respect to 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 by the LTO standard before LTO8.
  • Examples of the additional information include, but are not limited to, tension adjustment information, management ledger data, index information, thumbnail information of moving images stored on the magnetic tape 10, and the like.
  • the tension adjustment information includes the distance between adjacent servo bands (distance between servo patterns recorded in the adjacent servo bands) at the time of 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.
  • first information the information stored in the first storage area 336A
  • second information the information stored in the second storage area 336B
  • the memory 336 may have a plurality of banks. In this case, a part of the plurality of banks may form the first storage area 336A, and the remaining banks may form the second storage area 336B. Specifically, for example, when the cartridge 10A conforms to the LTO-9 standard or the LTO-10 standard, the memory 336 has two banks having a storage capacity of about 16 KB, and the two banks have two banks. One of the banks may form the first storage area 336A, and the other bank may form the second storage area 336B.
  • the antenna coil 331 induces an induced voltage by electromagnetic induction.
  • the controller 335 communicates with the recording / reproducing device 30 according to a specified communication standard via the antenna coil 331. Specifically, for example, mutual authentication, command transmission / reception, data exchange, etc. are performed.
  • the controller 335 stores the 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 and transmits the information to the recording / reproducing device 30 via the antenna coil 331 in response to the request of the recording / reproducing device 30.
  • the magnetic recording cartridge of the present technology may be a 2-reel type cartridge. That is, the magnetic recording cartridge of the present technology may have one or more reels (for example, two) on which the magnetic tape is wound.
  • reels for example, two
  • FIG. 17 is an exploded perspective view showing an example of the configuration of the 2-reel type cartridge 421.
  • the cartridge 421 is a synthetic resin upper half 402, a transparent window member 423 that is fitted and fixed to a window portion 402a opened on the upper surface of the upper half 402, and a reel 406 that is fixed to the inside of the upper half 402. , Reel holder 422 that prevents the floating of 407, lower half 405 that corresponds to the upper half 402, reels 406, 407, and reels 406, 407 that are stored in a space created by combining the upper half 402 and the lower half 405.
  • the reel 406 has a lower flange 406b having a cylindrical hub portion 406a around which the magnetic tape MT1 is wound in the center, an upper flange 406c having almost the same size as the lower flange 406b, and an upper flange 406c between the hub portion 406a and the upper flange 406c. It is provided with a sandwiched reel plate 411.
  • the reel 407 has the same configuration as the reel 406.
  • the window member 423 is provided with mounting holes 423a for assembling the reel holder 422, which is a reel holding means for preventing the reels from rising, at positions corresponding to the reels 406 and 407.
  • the magnetic tape MT1 is similar to the magnetic tape T in the first embodiment.
  • the average particle volume of the magnetic powder contained in the magnetic layer 13 is 2300 nm 3, or less, and the magnetic interaction ⁇ M of the magnetic layer 13 is ⁇ 0.362 ⁇ ⁇ M ⁇ ⁇ 0.22.
  • the magnetic recording medium 10 has good thermal stability and electromagnetic conversion characteristics.
  • the magnetic recording medium 10 may further include a barrier layer 15 provided on at least one surface of the base layer 11.
  • the barrier layer 15 is a layer for suppressing the dimensional change of the base layer 11 according to the environment. For example, as an example of the cause of causing the dimensional change, there is hygroscopicity of the base layer 11, but by providing the barrier layer 15, the rate of moisture invasion into the base layer 11 can be reduced.
  • the barrier layer 15 contains, for example, a metal or a metal oxide. Examples of the metal include Al, Cu, Co, Mg, Si, Ti, V, Cr, Mn, Fe, Ni, Zn, Ga, Ge, Y, Zr, Mo, Ru, Pd, Ag, Ba, Pt, etc.
  • 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, for example, at least one of Al 2 O 3 , CuO, CoO, SiO 2 , Cr 2 O 3 , TiO 2 , Ta 2 O 5 and Zr O 2 can be used.
  • the barrier layer 15 may contain diamond-like carbon (DLC), diamond, or the like.
  • the average thickness of the barrier layer 15 can be 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. However, 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 in the 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 in which the tension applied in the longitudinal direction of the magnetic recording medium 10 can be adjusted, and may include a plurality of the recording / playback devices 30 described above.
  • the SNR was measured as follows. (SNR in 25 ° C environment) The SNR (electromagnetic conversion characteristic) of the magnetic tape in a 25 ° C.
  • Example 1 (Preparation process of paint for forming magnetic layer)
  • the paint for forming the magnetic layer was prepared as follows. First, the first composition having the following composition was kneaded with an extruder. Next, the kneaded first composition and the second composition having the following composition were added to a stirring tank equipped with a disper and premixed. Subsequently, sand mill mixing was further performed and filtering was performed to prepare a coating material for forming a magnetic layer.
  • Aluminum oxide powder 5 parts by mass ( ⁇ -Al 2 O 3 , average particle size 0.2 ⁇ m)
  • Carbon black 2 parts by mass (manufactured by Tokai Carbon Co., Ltd., product name: Seast TA)
  • 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
  • the paint for forming the base layer was prepared as follows. First, the third composition having the following composition was kneaded with an extruder. Next, the kneaded third composition and the fourth composition having the following composition were added to a stirring tank provided with a disper, and premixing was performed. Subsequently, sand mill mixing was further performed and filter treatment was performed to prepare a coating material for forming a base layer.
  • Needle-shaped iron oxide powder 100 parts by mass ( ⁇ -Fe 2 O 3 , average major axis length 0.15 ⁇ m)
  • Vinyl chloride resin 55.6 parts by mass (resin solution: resin content 30% by mass, cyclohexanone 70% by mass)
  • Carbon black 10 parts by mass (average particle size 20 nm)
  • polyisocyanate (trade name: Coronate L, manufactured by Tosoh Corporation): 2 parts by mass and myristic acid: 2 parts by mass were added as a curing agent. bottom.
  • the paint for forming the back layer was prepared as follows. The following raw materials were mixed in a stirring tank equipped with a disper and filtered to prepare a coating material for forming a back layer.
  • Carbon black manufactured by Asahiyashiro, product name: # 80
  • Polyester polyurethane 100 parts by mass (manufactured by Nippon Polyurethane Industry, product name: N-2304)
  • Methyl ethyl ketone 500 parts by mass Toluene: 400 parts by mass
  • Cyclohexanone 100 parts by mass Polyisocyanate (trade name: Coronate L, manufactured by Tosoh Corporation): 10 parts by mass
  • a long PEN film (base film) having an average thickness of 4.0 ⁇ m was prepared as a support to be a base layer of the magnetic tape.
  • the base layer forming paint on one main surface of the PEN film and drying it, the average thickness of the final product on one main surface of the PEN film becomes 1.1 ⁇ m.
  • the base layer was formed as described above.
  • a paint for forming a magnetic layer was applied onto the base layer and dried to form a magnetic layer on the base layer so that the average thickness of the final product was 80 nm.
  • a paint for forming a back layer is applied onto the other main surface of the PEN film on which the base layer and the magnetic layer are formed and dried so that the average thickness of the final product becomes 0.4 ⁇ m.
  • a back layer was formed in.
  • the PEN film on which the base layer, the magnetic layer, and the back layer were formed was cured.
  • a calendar process was performed to smooth the surface of the magnetic layer.
  • the magnetic tape obtained as described above was cut to a width of 1/2 inch (12.65 mm). As a result, a long magnetic tape having an average thickness of 5.6 ⁇ m was obtained.
  • the obtained magnetic tape was obtained from the average thickness of the base film (base layer), the average thickness of the magnetic layer, the average thickness of the base layer, the average thickness of the back layer, and the magnetic tape (magnetic recording medium) as shown in Table 1.
  • Example 2 It differs from Example 1 in that the average particle volume of the magnetic powder is further reduced to 1450 nm 3 and the dispersion time in the preparation of the coating material for forming the magnetic layer is extended, but other conditions and methods are described in Example 1.
  • the magnetic tape was obtained in the same manner as above.
  • the composition and physical properties of the obtained magnetic tape had the values as shown in Table 1.
  • Example 3 It differs from Example 1 in that the average particle volume of the magnetic powder is further reduced to 1450 nm 3 , but other conditions and methods are the same as in Example 1 to obtain a magnetic tape.
  • the composition and physical properties of the obtained magnetic tape had the values as shown in Table 1.
  • Example 4 Although it differs from Example 1 in that the dispersion time in the preparation of the coating material for forming a magnetic layer was shortened, other conditions and methods were the same as in Example 1 to obtain a magnetic tape.
  • the composition and physical properties of the obtained magnetic tape had the values as shown in Table 1.
  • Example 5 When the paint for forming the magnetic layer was dried, the magnetic powder was magnetically oriented in the thickness direction of the PEN film by a solenoid coil. Specifically, with the solenoid coil, the magnetic powder was once magnetically oriented in the traveling direction (longitudinal direction) of the PEN film, and then magnetically oriented (vertically oriented) in the thickness direction of the PEN film. However, other conditions and methods were the same as in Example 1 to obtain a magnetic tape. The composition and physical properties of the obtained magnetic tape had the values as shown in Table 1.
  • Example 6 It differs from Example 1 in that the average thickness of the magnetic layer in the final product is 90 nm, but other conditions and methods are the same as in Example 1 to obtain a magnetic tape.
  • the composition and physical properties of the obtained magnetic tape had the values as shown in Table 1.
  • Example 7 It differs from Example 1 in that when the paint for forming the magnetic layer is dried, the magnetic powder is magnetically oriented in the thickness direction of the PEN film to shorten the dispersion time in the preparation of the paint for forming the magnetic layer.
  • the conditions and methods of the above were the same as in Example 1 to obtain a magnetic tape.
  • the composition and physical properties of the obtained magnetic tape had the values as shown in Table 1.
  • Example 8 In Example 1, the average particle volume of the magnetic powder was increased to 2300 nm 3 , and when the paint for forming the magnetic layer was dried, the magnetic powder was magnetically oriented in the thickness direction of the PEN film to form the paint for forming the magnetic layer.
  • the magnetic tape was obtained in the same manner as in Example 1 except that the dispersion time in the preparation was extended and the dispersibility was improved.
  • the composition and physical properties of the obtained magnetic tape had the values as shown in Table 1.
  • Example 9 In Example 1, the average particle volume of the magnetic powder was increased to 2300 nm 3 , and the magnetic powder was magnetically oriented in the thickness direction of the PEN film when the paint for forming the magnetic layer was dried, and the dispersibility was improved.
  • the magnetic tape was obtained in the same manner as in Example 1 except that the conditions and methods were the same as those in Example 1.
  • the composition and physical properties of the obtained magnetic tape had the values as shown in Table 1.
  • Example 1 Although it differs from Example 1 in that the average particle volume of the magnetic powder was increased to 2500 nm 3 , the other conditions and methods were the same as in Example 1 to obtain a magnetic tape. The composition and physical properties of the obtained magnetic tape had the values as shown in Table 1.
  • Example 2 It differs from Example 1 in that the average particle volume of the magnetic powder is further reduced to 1260 nm 3 so that the average thickness of the magnetic layer in the final product is 60 nm, but other conditions and methods. Obtained a magnetic tape in the same manner as in Example 1. The obtained magnetic tape had the composition and physical properties as shown in Table 1.
  • Example 3 It differs from Example 1 in that the average particle volume of the magnetic powder is further reduced to 1260 nm 3 , but other conditions and methods are the same as in Example 1 to obtain a magnetic tape.
  • the obtained magnetic tape had the composition and physical properties as shown in Table 1.
  • the average particle volume of the magnetic powder was 2300 nm 3 or less, and the magnetic interaction ⁇ M satisfied the relationship of ⁇ 0.362 ⁇ ⁇ M ⁇ ⁇ 0.22. Therefore, any magnetic tapes of Examples 1-9, thermal stability K u V act / k B T indicates 63 or more, was favorable. Further, all of the magnetic tapes of Examples 1 to 9 showed an SNR of 0.3 dB or more and had good electromagnetic conversion characteristics. From these results, it can be seen that the magnetic recording medium of the present technology has excellent thermal stability and electromagnetic conversion characteristics. Examples 1 to 7 had better electromagnetic conversion characteristics than those of Examples 8 and 9.
  • the average particle volume of the magnetic powder is smaller than 2000 nm 3
  • the average particle volume of the magnetic powder is as large as 2300 nm 3
  • the average particle volume of the magnetic powder is large. It can be seen that the electromagnetic conversion characteristics are improved by reducing the value.
  • Comparative Examples 1 to 3 in which the average particle volume of the magnetic powder is 2300 nm 3 or less and the magnetic interaction ⁇ M does not satisfy the relationship of ⁇ 0.362 ⁇ ⁇ M ⁇ ⁇ 0.22 are thermal stability or electromagnetic conversion characteristics. It can be seen that one of the above is inferior.
  • the numerical range indicated by using "-" indicates a range including the numerical values before and after "-" as the minimum value and the maximum value, respectively.
  • the upper limit value or the lower limit value of the numerical range of one step may be replaced with the upper limit value or the lower limit value of the numerical range of another step.
  • the materials exemplified in the present specification may be used alone or in combination of two or more.
  • the present technology can also have the following configuration.
  • the base layer A magnetic layer provided on the base layer and containing magnetic powder, It is a magnetic recording medium having a layered structure having The average thickness t T of the magnetic recording medium is 5.4 ⁇ m or less. The average particle volume of the magnetic powder is 2300 nm 3 or less.
  • a magnetic recording medium in which the magnetic interaction ⁇ M calculated by the following formula (1) of the magnetic layer is ⁇ 0.362 ⁇ ⁇ M ⁇ ⁇ 0.22.
  • ⁇ M ⁇ Id (H) + 2Ir (H) -Ir ( ⁇ ) ⁇ / Ir ( ⁇ ) ...
  • Id (H) is the remanent magnetization measured by direct current degaussing
  • Ir (H) is the remanent magnetization measured by alternating current degaussing
  • Ir ( ⁇ ) is the applied magnetic field of 6 kOe. Is the remanent magnetization measured as.
  • [2] The magnetic recording medium according to [1], wherein the magnetic powder is vertically oriented.
  • [3] The magnetic recording medium according to [1] or [2], wherein the magnetic interaction ⁇ M of the magnetic layer calculated by the above formula (1) is ⁇ 0.35 ⁇ ⁇ M.
  • the magnetic thermostable K u V act / k B T of the recording medium is 63 or more, a magnetic recording medium according to any one of [1] to [21].
  • the information is a tape cartridge containing adjustment information for adjusting the tension applied in the longitudinal direction of the magnetic recording medium.
  • Magnetic recording medium 11 Base layer (base layer) 12 Underlayer 13 Magnetic layer 14 Back layer

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Magnetic Record Carriers (AREA)
  • Manufacturing Of Magnetic Record Carriers (AREA)
  • Optical Head (AREA)
PCT/JP2020/028064 2020-03-31 2020-07-20 磁気記録媒体 Ceased WO2021199453A1 (ja)

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JPH0744858A (ja) * 1993-07-30 1995-02-14 Victor Co Of Japan Ltd 記録再生用磁気記録媒体及び接触転写マザーテープ用磁気記録媒体
JP2002251710A (ja) * 2001-02-22 2002-09-06 Fuji Photo Film Co Ltd 磁気記録媒体及びその製造方法
JP2002342913A (ja) * 2001-05-17 2002-11-29 Sony Corp 磁気記録媒体
JP2012203955A (ja) * 2011-03-25 2012-10-22 Fujifilm Corp 磁気テープおよびその製造方法、ならびに磁気記録装置
JP2014235771A (ja) * 2013-06-05 2014-12-15 ソニー株式会社 磁気記録媒体
JP6610824B1 (ja) * 2019-04-05 2019-11-27 ソニー株式会社 カートリッジおよびカートリッジメモリ

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JP6819836B1 (ja) * 2020-03-31 2021-01-27 ソニー株式会社 磁気記録媒体
WO2021199453A1 (ja) * 2020-03-31 2021-10-07 ソニーグループ株式会社 磁気記録媒体

Patent Citations (6)

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Publication number Priority date Publication date Assignee Title
JPH0744858A (ja) * 1993-07-30 1995-02-14 Victor Co Of Japan Ltd 記録再生用磁気記録媒体及び接触転写マザーテープ用磁気記録媒体
JP2002251710A (ja) * 2001-02-22 2002-09-06 Fuji Photo Film Co Ltd 磁気記録媒体及びその製造方法
JP2002342913A (ja) * 2001-05-17 2002-11-29 Sony Corp 磁気記録媒体
JP2012203955A (ja) * 2011-03-25 2012-10-22 Fujifilm Corp 磁気テープおよびその製造方法、ならびに磁気記録装置
JP2014235771A (ja) * 2013-06-05 2014-12-15 ソニー株式会社 磁気記録媒体
JP6610824B1 (ja) * 2019-04-05 2019-11-27 ソニー株式会社 カートリッジおよびカートリッジメモリ

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