WO2024181140A1 - 磁気記録媒体 - Google Patents

磁気記録媒体 Download PDF

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Publication number
WO2024181140A1
WO2024181140A1 PCT/JP2024/005181 JP2024005181W WO2024181140A1 WO 2024181140 A1 WO2024181140 A1 WO 2024181140A1 JP 2024005181 W JP2024005181 W JP 2024005181W WO 2024181140 A1 WO2024181140 A1 WO 2024181140A1
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WO
WIPO (PCT)
Prior art keywords
magnetic
recording medium
magnetic recording
less
layer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/JP2024/005181
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English (en)
French (fr)
Japanese (ja)
Inventor
実 山鹿
貴広 高山
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Sony Group Corp
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Sony Group Corp
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Filing date
Publication date
Application filed by Sony Group Corp filed Critical Sony Group Corp
Priority to JP2025503757A priority Critical patent/JPWO2024181140A1/ja
Publication of WO2024181140A1 publication Critical patent/WO2024181140A1/ja
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B21/00—Head arrangements not specific to the method of recording or reproducing
    • G11B21/02—Driving or moving of heads
    • G11B21/10—Track finding or aligning by moving the head ; Provisions for maintaining alignment of the head relative to the track during transducing operation, i.e. track following
    • 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
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/02—Recording, reproducing, or erasing methods; Read, write or erase circuits therefor
    • G11B5/09—Digital recording
    • 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
    • G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
    • G11B5/58—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B5/584—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following on tapes
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
    • G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
    • G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
    • G11B5/706—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/73—Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/84—Processes or apparatus specially adapted for manufacturing record carriers

Definitions

  • This technology relates to magnetic recording media.
  • Magnetic recording media are often used as a medium for recording large amounts of data.
  • Patent Document 1 discloses a magnetic recording medium having a magnetic layer with a thickness of 0.3 ⁇ m or less that contains at least iron-atom-containing magnetic powder and a binder on one or both sides of a non-magnetic support, and that is characterized in that, when the average iron element content of the surface layer from the center of the magnetic layer is S(Fe) and the average iron element content of the layer deeper than the center of the magnetic layer is D(Fe), S(Fe)/D(Fe) ⁇ 1.1 is satisfied.
  • Patent Document 2 discloses a magnetic recording medium having a magnetic layer formed by applying a magnetic paint containing at least a magnetic powder and a binder on a non-magnetic support, the magnetic layer being configured so that the constituent elements change in the depth direction of the magnetic layer, the content ratio of carbon constituting the binder in the surface layer of the magnetic layer to the elements constituting the magnetic powder is 90 vol % or more, and the content ratio of carbon constituting the binder in the surface layer of the magnetic layer to the elements constituting the magnetic powder is 70 vol % or less at a depth of 50 ⁇ or more from the surface of the magnetic layer.
  • Patent Document 3 proposes positioning the data read head at an angle to the width direction of the tape-type magnetic recording medium, even if the width dimension of the tape-type magnetic recording medium changes due to environmental changes.
  • the aim of this technology is to provide a magnetic recording medium that has improved reliability during operation and that can correct changes in width of the magnetic recording medium by adjusting the inclination of the drive's recording/playback head, even when stored or operated in a high-temperature environment.
  • the magnetic layer includes a magnetic layer, an underlayer, and a base layer, in that order.
  • the undercoat layer comprises a chlorine-containing binder;
  • the thickness of a portion of the underlayer where the chlorine count is equal to or greater than the following threshold value is 130 nm or less,
  • the magnetic recording medium has an average width change of 170 ppm or less before and after being left for 40 hours in an environment of a temperature of 50° C. and a relative humidity of 40% RH with a tension of 0.55 N applied in the longitudinal direction.
  • [Threshold] [average chlorine count in the undercoat layer] + 6 ⁇ [standard deviation obtained when calculating the average chlorine count]
  • the portion having a value equal to or greater than the threshold value may be present on the base layer side of the undercoat layer.
  • the portion of the underlayer that is equal to or greater than the threshold value may be present within 200 nm of the interface between the underlayer and the base layer.
  • the portion of the underlayer that is equal to or greater than the threshold value may be present within 130 nm of the interface between the underlayer and the base layer.
  • the total thickness of the magnetic layer and the underlayer may be 1000 nm or less.
  • the magnetic layer may have a thickness of 80 nm or less.
  • the underlayer may contain non-magnetic powder.
  • the magnetic recording medium may have an average thickness tT of 5.5 ⁇ m or less.
  • the magnetic layer may include magnetic powder.
  • the magnetic powder may include hexagonal ferrite, ⁇ iron oxide, or Co-containing spinel ferrite.
  • the magnetic layer includes a magnetic layer, an underlayer, and a base layer, in that order.
  • the undercoat layer comprises a chlorine-containing binder; the thickness of a portion of the underlayer where the chlorine count is equal to or greater than the threshold value is 12% or less of the thickness of the underlayer,
  • the present invention also provides a magnetic recording medium in which the average width change before and after being left stationary for 40 hours in an environment of a temperature of 50° C. and a relative humidity of 40% RH with a tension of 0.55 N applied in the longitudinal direction is 170 ppm or less.
  • [Threshold] [average chlorine count in the undercoat layer] + 6 ⁇ [standard deviation obtained when calculating the average chlorine count]
  • the average width change may be 140 ppm or less.
  • the base layer may comprise polyesters.
  • the polyesters may include at least one selected from the group consisting of polyethylene terephthalate and polyethylene naphthalate.
  • the base layer may have an average thickness of 4.4 ⁇ m or less.
  • the squareness ratio of the magnetic layer in the longitudinal direction of the magnetic recording medium may be 35% or less.
  • the magnetic layer may have five or more servo bands.
  • the magnetic layer may be configured to allow the formation of a plurality of data tracks, and the width of the data tracks may be 1200 nm or less.
  • the present technology also provides a magnetic recording cartridge in which the magnetic recording medium is wound around a reel and housed in a case.
  • FIG. 1 is a cross-sectional view showing a configuration of a magnetic recording medium according to a first embodiment.
  • FIG. 2 is a diagram showing an example of the shape of a particle of a magnetic powder.
  • 1 is an example of a TEM photograph of a cross section of a sample.
  • 13 is another example of a TEM photograph of a cross section of a sample.
  • FIG. 13 shows an example of a HAADF STEM image. This is a diagram to explain the Cl K ⁇ line extraction region set for a HAADF STEM image.
  • FIG. 13 is a diagram showing an example of plot data in which net counts are plotted against pixel position in the thickness direction.
  • FIG. 1 is a diagram for explaining the net count number, in particular, a diagram for explaining an example of a line where K ⁇ rays are counted.
  • FIG. 13 is a diagram showing an example of plot data in which the chlorine count number after normalization is plotted against the position in the thickness direction.
  • 1 is a schematic diagram of a magnetic recording medium according to a first embodiment, viewed from above (magnetic layer side).
  • 2 is an enlarged view showing a recording track in a data band of the magnetic recording medium.
  • FIG. 2 is an enlarged view showing a part of a servo pattern written in a servo band of the magnetic recording medium.
  • FIG. FIG. 2 is a perspective view showing a configuration of a measuring device.
  • FIG. 1 is a schematic diagram illustrating an example of the configuration of a tape drive device.
  • 2 is a schematic diagram of the drive head in the tape drive device as viewed from below (the tape running surface).
  • FIG. 4 is a diagram showing a state when a first drive head portion of the drive head is recording/reproducing a data signal.
  • FIG. 1A is a schematic plan view showing an example of servo pattern arrangement
  • FIG. 1B is a diagram showing the reproduced waveform.
  • 1A is a schematic diagram showing an example of the configuration of a servo pattern in which first servo band identification information is embedded
  • FIG. 1B is a schematic diagram showing an example of the configuration of a servo pattern in which second servo band identification information is embedded.
  • FIG. 5A and 5B are diagrams showing a reproduced waveform of a first servo pattern and a reproduced waveform of a second servo pattern, respectively;
  • FIG. 2 is an explanatory diagram of a drive head tracking a data band.
  • 10A and 10B are diagrams for explaining a method of measuring a servo trace line.
  • 1 is a schematic front view showing a servo pattern recording device according to an embodiment of the present technology
  • FIG. 2 is a partially enlarged view showing a part of the servo pattern recording device.
  • FIG. 2 is an exploded perspective view showing an example of the configuration of a magnetic recording cartridge.
  • FIG. 13 is an exploded perspective view showing an example of the configuration of a modified example of the magnetic recording cartridge.
  • 11A and 11B are schematic diagrams for explaining a method of calculating the movement angle of a drive head that is disposed at an angle.
  • the measurements are performed in an environment of 25°C ⁇ 2°C and 50% RH ⁇ 5% RH.
  • a coating material for forming a primer layer is applied onto a base layer to form a primer layer, and then a coating material for forming a magnetic layer is applied onto the primer layer to form a magnetic layer. It has been found that application of the coating material for forming a magnetic layer results in uneven distribution of the binder contained in the primer layer in the thickness direction. It was also found that uneven distribution of the binder in the underlayer affects the reliability of the magnetic recording tape. Due to uneven distribution of the binder, the ratio of the inorganic material and the binder in the underlayer becomes non-uniform across the thickness direction.
  • the reliability of the magnetic recording tape decreases, and for example, the possibility of defects occurring that require rewriting during recording processing increases.
  • the inventors have discovered that by controlling the distribution of the binder in the underlayer, the reliability of the magnetic recording tape can be improved.
  • the magnetic recording medium of the present technology includes a magnetic layer, an underlayer, and a base layer in this order.
  • the underlayer includes a chlorine-containing binder
  • the underlayer includes a portion having a chlorine count equal to or greater than the following threshold value.
  • [Threshold] [average chlorine count in the undercoat layer] + 6 ⁇ [standard deviation obtained when calculating the average chlorine count]
  • the chlorine count corresponds to the amount of chlorine-containing binder.
  • the portion where the chlorine count is equal to or greater than the threshold value has a higher chlorine count than the other portions of the undercoat layer, and contains more chlorine-containing binder than the other portions.
  • the portion where the chlorine count is equal to or greater than the threshold value is a portion where the chlorine-containing binder is unevenly distributed.
  • the width in the thickness direction of the portion that is equal to or greater than the threshold i.e., the uneven distribution width
  • the width in the thickness direction of the portion that is equal to or greater than the threshold is controlled, thereby improving the reliability of the magnetic recording medium, for example, the reliability during running for performing recording processing.
  • the thickness of the portion of the underlayer where the chlorine count is equal to or greater than the following threshold value may be, for example, 130 nm or less, preferably 125 nm or less, more preferably 120 nm or less, 115 nm or less, 110 nm or less, 105 nm or less, 100 nm or less, 95 nm or less, or 90 nm or less.
  • the thickness of the portion where the thickness is equal to or greater than the threshold value means the length of the portion where the thickness is equal to or greater than the threshold value in the thickness direction of the magnetic recording medium.
  • the thickness of the portion may be, for example, 30 nm or more, 40 nm or more, or 50 nm or more.
  • the thickness of the portion that is equal to or greater than the threshold value fall within the above-mentioned numerical range, i.e., by having such a small uneven distribution width, the reliability of the magnetic recording medium can be improved, and for example, the occurrence of rewrite during recording processing can be prevented.
  • the thickness of the portion of the underlayer where the chlorine count is equal to or greater than the threshold value is, for example, 12% or less of the thickness of the underlayer, preferably 11% or less, or even 10% or less or 9% or less.
  • the thickness of the portion where the chlorine count is equal to or greater than the threshold value means the length of the portion where the chlorine count is equal to or greater than the threshold value in the thickness direction of the magnetic recording medium.
  • the thickness of the portion may be, for example, 4% or more or 5% or more.
  • the thickness of the portion that is equal to or greater than the threshold value fall within the above-mentioned numerical range, i.e., by having such a small uneven distribution width, the reliability of the magnetic recording medium can be improved, and for example, the occurrence of rewrite during recording processing can be prevented.
  • the portion having a magnetic field equal to or greater than the threshold value is present on the base layer side of the underlayer.
  • the portion having a magnetic field equal to or greater than the threshold value may be present in the base layer side region.
  • the portion of the underlayer that is equal to or greater than the threshold value may be present within 200 nm, preferably within 150 nm, and particularly preferably within 130 nm, 120 nm, 110 nm, or 100 nm of the interface between the underlayer and the base layer.
  • the portion that is equal to or greater than the threshold value may be present so as to be in contact with the interface between the underlayer and the base layer. Controlling the positions of the portions where the concentration is above the threshold, that is, the positions of the portions where the chlorine-containing binder is unevenly distributed, also contributes to improving the reliability of the magnetic recording medium.
  • Some of the chlorine-containing binder is adsorbed to the inorganic material contained in the underlayer, while some is present without being adsorbed to the inorganic material.
  • the uneven distribution of the chlorine-containing binder described above is believed to be mainly due to the chlorine-containing binder not being adsorbed to the inorganic material. It is believed that the reliability of the magnetic recording medium can be improved by controlling the uneven distribution of the chlorine-containing binder. This will be described in more detail below.
  • the solvent in the paint affects the distribution state of the binder contained in the already formed undercoat layer, and in particular affects the distribution state of the binder that is present without being adsorbed to the inorganic material.
  • the possibility of powder falling off may increase in the early stages of use of the magnetic recording medium, which may reduce the reliability of the magnetic recording medium. For example, when a large number of reels of magnetic recording tape are run in one round trip or when full-surface recording is performed on a large number of reels of magnetic recording tape, the reliability of the magnetic recording tape may be adversely affected.
  • the reliability of the magnetic recording medium can be improved. For example, the possibility of defects that require rewriting during recording processing can be reduced.
  • the reliability is improved because the lubricant contained in the underlayer is appropriately supplied to the surface of the magnetic recording medium by controlling the uneven distribution.
  • the uneven distribution is caused by the chlorine-containing binder that is not adsorbed to the inorganic material as described above.
  • the chlorine-containing binder that is not adsorbed to the inorganic material can block the pores that supply the lubricant to the surface, and prevent the lubricant from being supplied to the surface of the magnetic recording medium. It is believed that by reducing the width of the uneven distribution, the range in which the chlorine-containing binder that is not adsorbed to the inorganic material is present is narrowed, thereby making it possible to appropriately supply the lubricant to the surface of the magnetic recording medium.
  • the width of the uneven distribution smaller and having the uneven distribution exist in the base layer, it is possible to more effectively prevent the supply of lubricant from being hindered due to the chlorine-containing binder blocking pores.
  • the chlorine-containing binder that is not adsorbed to the inorganic material may be present in a certain amount on the interface side between the magnetic layer and the undercoat layer. In this case, the chlorine-containing binder that is not adsorbed to the inorganic material may be likely to block the pores. Therefore, the thickness of the above-mentioned part is preferably 1/25 or more of the thickness of the undercoat layer, more preferably 1/20 or more.
  • Reliability can be improved by controlling the uneven distribution of the chlorine-containing binder so that excess chlorine-containing binder does not remain on the magnetic layer side.
  • the inventors have found that when stored or run in a high-temperature environment, creep changes become too large, and the change in width of the magnetic recording medium exceeds the range that can be corrected by adjusting the inclination of the drive's recording/playback head, making it difficult to correct the width change and creating a new problem in that running reliability cannot be ensured. In order to solve this problem, it has been found that it is important to reduce creep deformation of the magnetic recording medium while adjusting the flow of the chlorine-containing binder.
  • the present inventor has investigated technology for reducing creep deformation of magnetic recording media. As a result, the present inventor has found that by adjusting the average width change of the magnetic recording medium to within a specific numerical range, it is possible to reduce creep deformation of the magnetic recording medium when the magnetic recording medium wound in a cartridge is stored in a high-temperature environment for a long period of time, and creep deformation of the magnetic recording medium when the magnetic recording medium is run in a high-temperature environment for a long period of time.
  • the magnetic recording medium according to this technology has an average width change of 170 ppm or less before and after being left for 40 hours in an environment with a temperature of 50°C and a relative humidity of 40% RH with a tension of 0.55 N applied in the longitudinal direction, preferably 140 ppm or less, more preferably 70 ppm or less, and even more preferably 30 ppm or less. If the average width change ⁇ A of the magnetic recording medium exceeds 170 ppm, the creep change of the magnetic recording medium when the magnetic recording medium wound in a cartridge is stored in a high-temperature environment for a long period of time and the creep change of the magnetic recording medium when the magnetic recording medium is run in a high-temperature environment for a long period of time becomes large.
  • a high-temperature environment refers to an environment of 35°C or higher and 50°C or lower.
  • the average width change ⁇ A of the magnetic recording medium is 170 ppm or less, so in addition to deformation of the magnetic recording medium caused by the environment, creep deformation in high-temperature environments can be reduced. Therefore, width changes in the magnetic recording medium can be corrected by adjusting the tilt of the drive's recording/reproducing head.
  • the average width change ⁇ A may be set to a desired value by selecting at least one of the base layer and the undercoat layer.
  • the average width change ⁇ A may be set to a desired value by selecting at least one of the thickness of the base layer and the material of the base layer.
  • the average width change ⁇ A may also be set to a desired value by adjusting the stretching strength in the width direction and the length direction of the base layer.
  • the average width change ⁇ A may also be set to a desired value by selecting the type of magnetic layer from among a coated film and a sputtered film.
  • the average width change amount ⁇ A may also be set to a desired value by providing a distortion relaxation process after the calendar process and before the cutting process, and adjusting the environmental temperature and storage time in the distortion relaxation process (e.g., storing in an environment at a temperature of 65°C for 48 hours).
  • the average width change amount ⁇ A may also be set to a desired value by providing a distortion relaxation process after the demagnetization process and before the servo pattern writing process, and adjusting the environmental temperature and storage time in the distortion relaxation process (e.g., storing in an environment at a temperature of 55°C for 48 hours).
  • the average width change amount ⁇ A may be set to a desired value by selecting one of the above multiple selection examples, or by selecting two or more, the average width change amount ⁇ A may be set to a desired value.
  • the method for measuring the average width change amount ⁇ A is explained in 2. (3) below.
  • the magnetic recording medium according to the present technology may be compliant with the LTO standard, or may be compliant with a standard other than the LTO standard.
  • the width of the magnetic recording medium may be 1/2 inch, or may be wider than 1/2 inch. If the magnetic recording medium is compliant with the LTO standard, the width of the magnetic recording medium is 7 1/2 inches.
  • the magnetic recording medium may have a configuration that allows the width of the magnetic recording medium to be kept constant or nearly constant by adjusting the inclination of the recording/reproducing head of the drive during running.
  • the magnetic recording medium according to the present technology may preferably be a long magnetic recording medium, for example a magnetic recording tape (particularly a long magnetic recording tape).
  • the magnetic recording medium is preferably used in a recording and reproducing device equipped with a ring-type head as a recording head.
  • the magnetic recording medium is preferably used in a recording and reproducing device configured to be capable of recording data with a data track width of 1100 nm or less or 900 nm or less.
  • the magnetic recording medium according to the present technology may have a magnetic layer, a non-magnetic layer (underlayer), a base layer, and a back layer in this order, and may include other layers in addition to these layers.
  • the other layers may be appropriately selected depending on the type of magnetic recording medium.
  • the magnetic recording medium may be a coating-type magnetic recording medium, that is, a magnetic recording medium manufactured by coating a base layer with a material (particularly a paint) that forms other layers and then drying it.
  • the average thickness (average total thickness) tT of the magnetic recording medium according to the present technology may be, for example, preferably 5.5 ⁇ m or less, more preferably 5.4 ⁇ m or less, even more preferably 5.3 ⁇ m or less, 5.2 ⁇ m or less, 5.1 ⁇ m or less, 5.0 ⁇ m or less, 4.9 ⁇ m or less, or 4.8 ⁇ m or less, and even more preferably 4.6 ⁇ m or less or 4.4 ⁇ m or less. Since the magnetic recording medium is thus thin, for example, the tape length wound into one magnetic recording cartridge can be made longer, thereby increasing the recording capacity per one magnetic recording cartridge.
  • the lower limit of the average thickness (average total thickness) tT of the magnetic recording medium is not particularly limited, but is, for example, 3.5 ⁇ m ⁇ tT . The method for measuring the average thickness of the magnetic recording medium will be described in 2. (3) below.
  • the average thickness tm of the magnetic layer of the magnetic recording medium according to the present technology may be preferably 80 nm or less, more preferably 70 nm or less, even more preferably 60 nm or less, 50 nm or less, and even more preferably 40 nm or less.
  • the lower limit of the average thickness tm of the magnetic layer is not particularly limited, but is preferably 30 nm or more. The method for measuring the average thickness of the magnetic layer will be described in 2.(3) below.
  • the average thickness of the underlayer (also called the non-magnetic layer) of the magnetic recording medium according to the present technology can be preferably 1200 nm or less, preferably 1150 nm or less, 1120 nm or less, 1100 nm or less, more preferably 1000 nm or less, 900 nm or less, 800 nm or less, 700 nm or less, and even more preferably 600 nm or less.
  • the lower limit of the average thickness of the underlayer is not particularly limited, but can be preferably 200 nm or more, and more preferably 300 nm or more. The method for measuring the average thickness of the underlayer is explained in 2. (3) below.
  • the average thickness of the base layer (also referred to as the substrate layer) of the magnetic recording medium according to the present technology may be preferably 4.5 ⁇ m or less, more preferably 4.2 ⁇ m or less, 4.0 ⁇ m or less, 3.8 ⁇ m or less, or 3.6 ⁇ m or less, and even more preferably 3.4 ⁇ m or less, 3.2 ⁇ m or less, or 3.0 ⁇ m or less.
  • the lower limit of the average thickness of the base layer is not particularly limited, but may be, for example, preferably 2.0 ⁇ m or more, 2.2 ⁇ m or more, 2.4 ⁇ m or more, and more preferably 2.5 ⁇ m or more.
  • the method for measuring the average thickness of the base layer is described below in 2. (3).
  • the average thickness of the back layer of the magnetic recording medium according to the present technology may be preferably 0.6 ⁇ m or less, more preferably 0.5 ⁇ m or less, even more preferably 0.4 ⁇ m or less, 0.3 ⁇ m or less, 0.25 ⁇ m or less, or 0.2 ⁇ m or less.
  • the lower limit of the average thickness of the back layer is not particularly limited, but may be, for example, preferably 0.1 ⁇ m or more, more preferably 0.15 ⁇ m or more.
  • the method for measuring the average thickness of the back layer is described below in 2. (3).
  • the total thickness of the magnetic layer and the underlayer of the magnetic recording medium according to the present technology is preferably 1200 nm or less, and may be, for example, 1100 nm or less, 1000 nm or less, or 900 nm or less.
  • the total may be, for example, 300 nm or more, particularly 400 nm or more.
  • the magnetic recording medium 10 is, for example, a magnetic recording medium that has been subjected to a vertical orientation process.
  • the magnetic recording medium 10 includes a long base layer (also called a substrate) 11, an underlayer 12 provided on one main surface of the base layer 11, a magnetic layer (also called a recording layer) 13 provided on the underlayer 12, and a back layer 14 provided on the other main surface of the base layer 11.
  • the surface on which the magnetic layer 13 is provided is referred to as the magnetic surface
  • the surface opposite to the magnetic surface (the surface on which the back layer 14 is provided) is referred to as the back surface.
  • the magnetic recording medium 10 has an elongated shape and runs in the longitudinal direction during recording and playback.
  • the magnetic recording medium 10 may be configured to be capable of recording signals at a shortest recording wavelength of preferably 60 nm or less, more preferably 50 nm or less, even more preferably 45 nm or less, and particularly preferably 40 nm or less, and may be used, for example, in a recording and playback device whose shortest recording wavelength is within the above range.
  • the base layer 11 can function as a support for the magnetic recording medium 10 and can be, for example, a flexible, long, non-magnetic substrate, particularly a non-magnetic film.
  • the base layer 11 can contain, for example, at least one of polyester resins, polyolefin resins, cellulose derivatives, vinyl resins, aromatic polyether ketone resins, and other polymer resins. When the base layer 11 contains two or more of the above materials, the two or more materials can be mixed, copolymerized, or laminated.
  • the polyester-based resin may be, for example, one or a mixture of two or more of PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PBN (polybutylene naphthalate), PCT (polycyclohexylene dimethylene terephthalate), PEB (polyethylene-p-oxybenzoate), and polyethylene bisphenoxycarboxylate.
  • the base layer 11 may be formed from PET or PEN.
  • the polyolefin resin may be, for example, one or a mixture of two or more of PE (polyethylene) and PP (polypropylene).
  • the cellulose derivative may be, for example, one or a mixture of two or more of cellulose diacetate, cellulose triacetate, CAB (cellulose acetate butyrate), and CAP (cellulose acetate propionate).
  • the vinyl resin may be, for example, one or a mixture of two or more of PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride).
  • the aromatic polyetherketone resin may be, for example, one or a mixture of two or more of PEK (polyetherketone), PEEK (polyetheretherketone), PEKK (polyetherketoneketone), and PEEKK (polyetheretherketoneketone).
  • the base layer 11 may be formed from PEEK.
  • the other polymer resin may be, for example, one or a mixture of two or more of PA (polyamide, nylon), aromatic PA (aromatic polyamide, aramid), PI (polyimide), aromatic PI (aromatic polyimide), PAI (polyamideimide), aromatic PAI (aromatic polyamideimide), PBO (polybenzoxazole, e.g. Zylon (registered trademark), polyether, polyetherester, PES (polyethersulfone), PEI (polyetherimide), PSF (polysulfone), PPS (polyphenylene sulfide), PC (polycarbonate), PAR (polyarylate), and PU (polyurethane).
  • PA polyamide, nylon
  • aromatic PA aromatic polyamide, aramid
  • PI polyimide
  • PAI polyamideimide
  • PAI aromatic PAI
  • PBO polybenzoxazole, e.g. Zylon (registered trademark)
  • polyether polyetherester
  • the base layer may be formed from a resin that does not contain chlorine, and in particular from a polyester-based resin that does not contain chlorine.
  • the base layer may also be formed from a resin that contains chlorine.
  • the magnetic layer 13 may be, for example, a perpendicular recording layer.
  • the magnetic layer 13 includes magnetic powder.
  • the magnetic layer 13 may further include a binder.
  • the magnetic layer 13 may further include non-magnetic particles.
  • the magnetic layer 13 may further include additives such as a lubricant and an anti-rust agent, as necessary.
  • the magnetic layer 13 is preferably a magnetic layer that is vertically oriented.
  • vertical orientation means that the squareness ratio S1 measured in the longitudinal direction (travel direction) of the magnetic recording medium 10 is 35% or less.
  • the magnetic particles constituting the magnetic powder contained in the magnetic layer 13 may include, but are not limited to, hexagonal ferrite, epsilon iron oxide ( ⁇ iron oxide), Co-containing spinel ferrite, gamma hematite, magnetite, chromium dioxide, cobalt-coated iron oxide, and metal.
  • the magnetic powder may be one of these, or a combination of two or more.
  • the magnetic powder may include hexagonal ferrite, ⁇ iron oxide, or Co-containing spinel ferrite.
  • the magnetic powder is hexagonal ferrite.
  • the hexagonal ferrite may particularly preferably include at least one of Ba and Sr.
  • the ⁇ iron oxide may particularly preferably include 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.
  • Metal can be spindle-shaped.
  • the hexagonal ferrite particles contain Fe and a metal M1 other than Fe.
  • the metal M1 contains an alkaline earth metal.
  • the alkaline earth metal may contain at least one or more of Sr, Ba, and Ca, and among these metals, it is preferable to contain Sr.
  • the metal M1 may contain Pb in addition to the alkaline earth metal.
  • the hexagonal ferrite particles may further contain a metal M2 in addition to Fe and the metal M1.
  • the metal M2 includes, for example, one selected from the group consisting of rare earth elements, transition metal elements other than Fe, and metal elements of Group 13 of the periodic table, and among these, at least one selected from the group consisting of Ti, Al, and Nd is preferable.
  • the hexagonal ferrite particles may be barium ferrite particles or strontium ferrite particles.
  • the strontium ferrite particles refer to hexagonal ferrite particles in which the atomic ratio of Sr to metal M1 is 50 atomic % or more. Therefore, the hexagonal ferrite particles containing Sr and metal M1 other than Sr are included in the strontium ferrite particles when the atomic ratio of Sr to metal M1 is 50 atomic % or more.
  • metal M1 contains Sr and Ba
  • the hexagonal ferrite particles in which the atomic ratio of Sr to the total amount of Sr and Ba is 50 atomic % or more are called strontium ferrite particles.
  • the hexagonal ferrite may have an average composition represented by the following general formula (1): Sr (1-x) ⁇ x Fe (12-y) ⁇ y O 19 ...(1)
  • ⁇ represents at least one element selected from the group consisting of Ba, Ca, and Pb
  • ⁇ represents at least one element selected from the group consisting of rare earth elements, transition metal elements other than Fe, and metal elements of Group 13 of the periodic table
  • x is within the range of 0 ⁇ x ⁇ 0.9, preferably 0 ⁇ x ⁇ 0.7, and more preferably 0.3 ⁇ x ⁇ 0.7
  • y represents 0 ⁇ y ⁇ 0.80, preferably 0.22 ⁇ y ⁇ 0.80, and more preferably 0.26 ⁇ y ⁇ 0.80.
  • the average particle size of the magnetic powder may be preferably 30 nm or less, more preferably 25 nm or less, even more preferably 20 nm or less, 18 nm or less, 16 nm or less, 14 nm or less, or 12 nm or less.
  • the average particle size may be, for example, 8 nm or more, preferably 9 nm or more, more preferably 10 nm or more.
  • the average particle size of the magnetic powder may be 8 nm or more and 30 nm or less, 8 nm or more and 25 nm or less, 9 nm or more and 20 nm or less, 9 nm or more and 16 nm or less, or 9 nm or more and 14 nm or less.
  • the average particle size of the magnetic powder is equal to or less than the upper limit (for example, 30 nm or less, particularly 20 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 lower limit (for example, 8 nm or more, preferably 9 nm or more), the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (for example, SNR) can be obtained.
  • the lower limit for example, 8 nm or more, preferably 9 nm or more
  • the average aspect ratio of the magnetic powder may be preferably 1.0 or more and 3.0 or less, more preferably 1.0 or more and 2.8 or less, and even more preferably 1.5 or more and 2.5 or less.
  • the average particle size and average aspect ratio of the magnetic powder can be determined as follows.
  • the magnetic recording medium (hereinafter also referred to as "magnetic tape") contained in the magnetic recording cartridge is unwound, and the magnetic tape to be measured is cut out to about 50 mm.
  • the cut-out position may be 30 m in the longitudinal direction from the connection part 221 between the magnetic tape T and the leader tape LT.
  • the magnetic tape to be measured is processed by the FIB method or the like to be thinned.
  • a carbon layer and a tungsten layer are formed as protective films as a pretreatment for observing the TEM image of the F surface described later.
  • the carbon layer is formed on the surface of the magnetic layer side and the surface of the back layer side of the magnetic tape by a vapor deposition method, and the tungsten layer is further formed on the surface of the magnetic layer side by a vapor deposition method or a sputtering method.
  • the thinning is performed along the length direction (longitudinal direction) of the magnetic tape. In other words, this slicing creates a cross section that is parallel to both the length and thickness of the magnetic tape.
  • the cross section of the obtained thin sample is observed using a transmission electron microscope (Hitachi High-Technologies Corporation H-9500) at an acceleration voltage of 200 kV and a total magnification of 500,000 times to ensure that the entire magnetic layer is included in the thickness direction of the magnetic layer, and a TEM photograph is taken.
  • TEM photographs are prepared in sufficient numbers to extract 50 particles for which the plate diameter DB and plate thickness DA (see Figure 2A) shown below can be measured.
  • the size of the hexagonal ferrite particles (hereinafter referred to as "particle size") is defined as the plate diameter DB, which is the long diameter of the plate surface or base, when the shape of the particle observed in the above TEM photograph is plate-like or columnar (however, the thickness or height is smaller than the long diameter of the plate surface or base) as shown in Figure 2A.
  • the thickness or height of the particle observed in the above TEM photograph is defined as the plate thickness DA.
  • the long diameter means the longest diagonal distance.
  • the thickness or height of a particle is not constant within a single particle, the thickness or height of the maximum particle is defined as the plate thickness DA.
  • 50 particles are selected from the TEM photograph based on the following criteria. Particles with parts outside the field of view of the TEM photograph are not measured, and only particles with a clear outline and that exist in isolation are measured. If there are overlapping particles, those with a clear boundary between them and whose overall shape can be determined are measured as individual particles, but particles with unclear boundaries and whose overall shape cannot be determined are not measured as their shape cannot be determined.
  • 2B and 2C show examples of TEM photographs.
  • the particles indicated by the arrows a and d are selected because the plate thickness (thickness or height) DA of the particle can be clearly confirmed.
  • the plate thickness DA of each of the selected 50 particles is measured.
  • the plate thicknesses DA thus obtained are simply averaged (arithmetic average) to obtain the average plate thickness DA ave .
  • the average plate thickness DA ave is the average particle plate thickness.
  • the plate diameter DB of each magnetic powder is measured.
  • 50 particles whose plate diameter DB of the particle can be clearly confirmed are selected from the TEM photograph taken.
  • the particles indicated by the arrows b and c are selected because the plate diameter DB can be clearly confirmed.
  • the plate diameter DB of each of the selected 50 particles is measured.
  • the plate diameter DB thus obtained is simply averaged (arithmetic average) to obtain the average plate diameter DB ave .
  • the average plate diameter DB ave is the average particle size.
  • the average particle volume of the magnetic powder is preferably 1800 nm3 or less, more preferably 1600 nm3 or less, more preferably 1400 nm3 or less, even more preferably 1200 nm3 or less, 1000 nm3 or less, or even 900 nm3 or less.
  • the average particle volume of the magnetic powder may be preferably 500 nm3 or more, more preferably 700 nm3 or more.
  • the average particle volume of the magnetic powder is equal to or less than the upper limit (e.g., 2000 nm3 or less), good electromagnetic conversion characteristics (e.g., SNR) can be obtained in the high recording density magnetic recording medium 10.
  • the average particle volume of the magnetic powder is equal to or more than the lower limit (e.g., 500 nm3 or more), the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (e.g., SNR) can be obtained.
  • the average particle volume of the magnetic powder is calculated as follows. First, the average plate thickness DA ave and the average plate diameter DB ave are calculated as described above in relation to the method for calculating the average particle size of the magnetic powder. Next, the average particle volume V of the magnetic powder is calculated using the following formula.
  • the coercive force Hc1 measured in the thickness direction (perpendicular direction) of the magnetic recording medium 10 is preferably 2010 [Oe] or more and 3520 [Oe] or less, more preferably 2070 [Oe] or more and 3460 [Oe] or less, and even more preferably 2140 [Oe] or more and 3390 [Oe] or less.
  • the magnetic powder may preferably include a powder of nanoparticles containing ⁇ -iron oxide (hereinafter referred to as " ⁇ -iron oxide particles"). Even fine particles of ⁇ -iron oxide particles can achieve high coercivity. It is preferable that the ⁇ -iron oxide contained in the ⁇ -iron oxide particles has a preferential crystal orientation in the thickness direction (perpendicular direction) of the magnetic recording medium 10.
  • the ⁇ -iron oxide particles may have a composite particle structure. More specifically, the ⁇ -iron oxide particles include an ⁇ -iron oxide portion and a portion having soft magnetism or a portion having a higher saturation magnetization ⁇ s and a smaller coercive force Hc than ⁇ -iron oxide (hereinafter referred to as the "soft magnetic portion, etc.”).
  • the ⁇ -iron oxide portion contains ⁇ -iron oxide.
  • the ⁇ -iron oxide contained in the ⁇ -iron oxide portion preferably has ⁇ -Fe 2 O 3 crystals as a main phase, and more preferably is made of single-phase ⁇ -Fe 2 O 3 .
  • the soft magnetic portion is in contact with at least a portion of the ⁇ -iron oxide portion. Specifically, the soft magnetic portion may partially cover the ⁇ -iron oxide portion, or may cover the entire periphery of the ⁇ -iron oxide portion.
  • the soft magnetic portion (the magnetic portion having a higher saturation magnetization ⁇ s and a smaller coercive force Hc than ⁇ -iron oxide) includes, for example, a soft magnetic material such as ⁇ -Fe, a Ni-Fe alloy, or an Fe-Si-Al alloy.
  • ⁇ -Fe may be obtained by reducing the ⁇ -iron oxide contained in the ⁇ -iron oxide portion.
  • the portion having soft magnetic properties may contain, for example, Fe 3 O 4 , ⁇ -Fe 2 O 3 , or spinel ferrite.
  • the coercive force Hc of the ⁇ -iron oxide portion alone can be kept high to ensure thermal stability, while the coercive force Hc of the ⁇ -iron oxide particle (composite particle) as a whole can be adjusted to a coercive force Hc suitable for recording.
  • the ⁇ iron oxide particles may contain an additive instead of the structure of the composite particles, or may have the structure of the composite particles and contain an additive. In this case, part of the Fe in the ⁇ iron oxide particles is replaced with the additive.
  • the additive is a metal element other than iron, preferably a trivalent metal element, more preferably at least one selected from the group consisting of Al, Ga and In, and even more preferably at least one selected from the group consisting of Al and Ga.
  • the ⁇ -iron oxide containing the additive is an ⁇ -Fe2 - xMxO3 crystal (wherein M is a metal element other than iron, preferably a trivalent metal element, more preferably one or more selected from the group consisting of Al, Ga, and In; x is, for example, 0 ⁇ x ⁇ 1).
  • the average particle size (average maximum particle size) of the magnetic powder is preferably 22 nm or less, more preferably 8 nm to 22 nm, and even more preferably 12 nm to 22 nm.
  • the area with a size of 1/2 the recording wavelength becomes the actual magnetization area. Therefore, by setting the average particle size of the magnetic powder to less than half the shortest recording wavelength, a good SNR can be obtained. Therefore, when the average particle size of the magnetic powder is 22 nm or less, good electromagnetic conversion characteristics (e.g., SNR) can be obtained in a high recording density magnetic recording medium 10 (e.g., a magnetic recording medium 10 configured to be able to record signals at the shortest recording wavelength of 44 nm or less).
  • the average particle size of the magnetic powder is 8 nm or more, the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (e.g., SNR) can be obtained.
  • the average aspect ratio of the magnetic powder is preferably 1.0 or more and 3.0 or less, more preferably 1.0 or more and 2.9 or less, and even more preferably 1.0 or more and 2.5 or less.
  • the average aspect ratio of the magnetic powder is within the above numerical range, aggregation of the magnetic powder can be suppressed, and the resistance applied to the magnetic powder when the magnetic powder is vertically oriented in the process of forming the magnetic layer 13 can be suppressed. 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. First, the magnetic recording medium to be measured is cut out as described above for the case where the magnetic powder contains hexagonal ferrite particles. The magnetic recording medium to be measured is processed and sliced by FIB (Focused Ion Beam) method or the like. When the FIB method is used, a carbon film and a tungsten thin film are formed as protective films as a pretreatment for observing the cross-sectional TEM image described below.
  • FIB Flucused Ion Beam
  • the carbon film is formed on the magnetic layer side surface and back layer side surface of the magnetic recording medium 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 slicing is performed along the length direction (longitudinal direction) of the magnetic recording medium. In other words, the slicing forms a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic recording medium.
  • the cross section of the obtained thin sample is observed using a transmission electron microscope (Hitachi High-Technologies Corporation H-9500) at an acceleration voltage of 200 kV and a total magnification of 500,000 times, so that the entire magnetic layer 13 is included in the thickness direction of the magnetic layer 13, and a TEM photograph is taken.
  • a transmission electron microscope Hagachi High-Technologies Corporation H-9500
  • the long axis length DL refers to the maximum distance between two parallel lines drawn from any angle so as to be tangent to the contour of each particle (the so-called maximum Feret diameter).
  • the short axis length DS refers to the maximum length of the particle in the direction perpendicular to the long axis (DL) of the particle.
  • the long axis lengths DL of the 50 measured particles are simply averaged (arithmetic mean) to determine the average long axis length DL ave .
  • the average long axis length DL ave thus determined is the average particle size of the magnetic powder.
  • the short axis lengths DS of the 50 measured particles are also simply averaged (arithmetic mean) to determine the average short axis length DS ave .
  • the average aspect ratio of the particles (DL ave /DS ave ) is then calculated from the average long axis length DL ave and the average short axis length DS ave .
  • the average particle volume of the magnetic powder is preferably 1800 nm3 or less, more preferably 1600 nm3 or less, more preferably 1400 nm3 or less, even more preferably 1200 nm3 or less, 1100 nm3 or less, or even 1000 nm3 or less.
  • the average particle volume of the magnetic powder may be preferably 500 nm3 or more, more preferably 700 nm3 or more.
  • the average particle volume of the magnetic powder is equal to or less than the upper limit (e.g., 2000 nm3 or less), good electromagnetic conversion characteristics (e.g., SNR) can be obtained in the high recording density magnetic recording medium 10.
  • the average particle volume of the magnetic powder is equal to or more than the lower limit (e.g., 500 nm3 or more), the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (e.g., SNR) can be obtained.
  • the average particle volume of the magnetic powder can be found as follows.
  • the magnetic recording medium 10 is processed and sliced by FIB (Focused Ion Beam) method or the like.
  • FIB Flucused Ion Beam
  • a carbon film and a tungsten thin film are formed as protective films as a pretreatment for observing the cross-sectional TEM image described below.
  • the carbon film is formed on the magnetic layer side surface and 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 slices are formed along the length direction (longitudinal direction) of the magnetic recording medium 10. In other words, the slices form a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic recording medium 10.
  • the obtained thin-section sample is observed using a transmission electron microscope (Hitachi High-Technologies Corporation H-9500) at an acceleration voltage of 200 kV and a total magnification of 500,000 times to observe the cross section of the magnetic layer 13 in the thickness direction so as to include the entire magnetic layer 13, and a TEM photograph is obtained.
  • a transmission electron microscope Hagachi High-Technologies Corporation H-9500
  • the magnification and acceleration voltage may be adjusted as appropriate depending on the type of device.
  • V ave particle volume
  • the coercive force Hc of the ⁇ iron oxide particles is preferably 2500 Oe or more, and more preferably 2800 Oe or more and 4200 Oe or less.
  • the magnetic powder may include a powder of nanoparticles (hereinafter also referred to as "cobalt ferrite particles") containing Co-containing spinel ferrite. That is, the magnetic powder may be cobalt ferrite magnetic powder.
  • the cobalt ferrite particles preferably have uniaxial crystal anisotropy.
  • the cobalt ferrite magnetic particles have, for example, a cubic or nearly cubic shape.
  • the Co-containing spinel ferrite may further include 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: C x M y Fe 2 O z
  • M is, for example, one or more metals selected from the group consisting of Ni, Mn, Al, Cu, and Zn.
  • x is a value within the range of 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 a value within the range of 3 ⁇ z ⁇ 4.
  • a part of Fe may be substituted with another metal element.
  • the average particle size of the cobalt ferrite magnetic powder is preferably 21 nm or less, more preferably 19 nm or less.
  • the coercive force Hc of the cobalt ferrite magnetic powder is preferably 2500 Oe or more, more preferably 2600 Oe or more and 3500 Oe or less.
  • the average particle size of the magnetic powder is preferably 25 nm or less, more preferably 10 nm or more and 19 nm or less. Such a small average particle size of the magnetic powder makes it possible to obtain good electromagnetic conversion characteristics (e.g., SNR) in a high recording density magnetic recording medium 10. On the other hand, when the average particle size of the magnetic powder is 10 nm or more, the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (e.g., SNR) can be obtained.
  • the average aspect ratio and average particle size of the magnetic powder are determined in the same manner as when the magnetic powder contains ⁇ iron oxide particles.
  • the average particle volume of the magnetic powder is preferably 2000 nm3 or less, more preferably 1900 nm3 or less, more preferably 1800 nm3 or less, even more preferably 1700 nm3 or less, 1600 nm3 or less, or even 1500 nm3 or less.
  • the average particle volume of the magnetic powder may be preferably 500 nm3 or more, more preferably 700 nm3 or more.
  • the average particle volume of the magnetic powder is equal to or less than the upper limit (e.g., 2000 nm3 or less), good electromagnetic conversion characteristics (e.g., SNR) can be obtained in the high recording density magnetic recording medium 10.
  • the average particle volume of the magnetic powder is equal to or more than the lower limit (e.g., 500 nm3 or more), the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (e.g., SNR) can be obtained.
  • a binder a resin having a structure in which a cross-linking reaction has been imparted to a polyurethane resin or a vinyl chloride resin is preferable.
  • the binder is not limited to these, and other resins may be appropriately blended depending on the physical properties required for the magnetic recording medium 10.
  • the resin to be blended so long as it is a resin that is generally used in coating-type magnetic recording media 10.
  • binder examples include polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylate-acrylonitrile copolymer, acrylate-vinyl chloride-vinylidene chloride copolymer, acrylate-vinylidene chloride copolymer, methacrylate-vinylidene chloride copolymer, methacrylate-vinyl chloride copolymer, methacrylate-ethylene copolymer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, acrylonitrile-butadiene copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose), styrene-butad
  • the binder may be a thermosetting resin or a reactive resin, examples of which include phenolic resin, epoxy resin, urea resin, melamine resin, alkyd resin, silicone resin, polyamine resin, and urea formaldehyde resin.
  • examples of polar functional groups include side chain type groups having terminal groups of -NR1R2, -NR1R2R3 + X- , and main chain type groups of >NR1R2 + X- .
  • R1, R2, and R3 in the formula are hydrogen atoms or hydrocarbon groups
  • X- is a halogen element ion such as fluorine, chlorine, bromine, or iodine, or an inorganic or organic ion.
  • examples of polar functional groups include -OH, -SH, -CN, and epoxy groups.
  • the magnetic layer includes a chlorine-containing binder.
  • the chlorine-containing binder may be a chlorine-containing resin.
  • the chlorine-containing resin is a resin that includes a chlorine atom as at least one of the elements constituting the resin.
  • the chlorine-containing binder is, for example, a vinyl chloride resin.
  • chlorine-containing binder examples include polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-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, vinylidene chloride-acrylonitrile copolymer, and synthetic rubber.
  • the content of the chlorine-containing binder in the magnetic layer may be, for example, preferably 30 parts by mass or more, more preferably 35 parts by mass or more, and even more preferably 40 parts by mass or more, per 100 parts by mass of magnetic powder. Also, the content may be, for example, preferably 70 parts by mass or less, more preferably 65 parts by mass or less, and even more preferably 60 parts by mass or less, per 100 parts by mass of magnetic powder.
  • the magnetic layer may further contain a chlorine-free binder in addition to the chlorine-containing binder.
  • the chlorine-free binder may be a chlorine-free resin.
  • the chlorine-free resin may contain, for example, a polyurethane-based resin.
  • the polyurethane-based resin may be, for example, a urethane-modified copolymer polyester.
  • the urethane-modified copolymer polyester may be a urethane-modified copolymer polyester having an aromatic polyester as a basic skeleton and a urethane component in the side chain, or a urethane-modified copolymer polyester containing an ester repeat unit and a urethane repeat unit in the basic skeleton.
  • the content of the chlorine-free binder in the magnetic layer may be, for example, preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, per 100 parts by mass of magnetic powder. Also, the content may be, for example, preferably 10 parts by mass or less, more preferably 9 parts by mass or less, and even more preferably 8 parts by mass or less, per 100 parts by mass of magnetic powder.
  • 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 may preferably be a compound represented by the following general chemical formula (1) or general chemical formula (2).
  • the fatty acid may contain one or both of the compound represented by the following general chemical formula (1) and the compound represented by the general chemical formula (2).
  • the fatty acid ester may preferably be a compound represented by the following general chemical formula (3), (4), or (5).
  • the fatty acid ester may contain any one of the compounds represented by the following general chemical formula (3), (4), and (5), or may contain two or more selected from these.
  • the lubricant contains either one or both of the compound represented by general chemical formula (1) and the compound represented by general chemical formula (2), and either one or more of the compound represented by general chemical formula (3), the compound represented by general chemical formula (4), and the compound represented by general chemical formula (5), so that an increase in the dynamic friction coefficient of the magnetic recording medium due to repeated recording or reproduction can be suppressed.
  • the lubricant may be, for example, an ester of a monobasic fatty acid having 10 to 24 carbon atoms with any one of monohydric to hexahydric alcohols having 2 to 12 carbon atoms, a mixed ester thereof, a difatty acid ester, a trifatty acid ester, etc.
  • 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, octyl stearate, isooctyl stearate, octyl myristate, etc.
  • the magnetic layer may contain any one or more of these.
  • the amount of the lubricant may be, for example, preferably 1 part by mass or more, and more preferably 2 parts by mass or more, per 100 parts by mass of the magnetic powder. Also, the amount of the lubricant may be, for example, preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 6 parts by mass or less, per 100 parts by mass of the magnetic powder.
  • the magnetic layer 13 may further contain non-magnetic reinforcing particles such as aluminum oxide ( ⁇ , ⁇ , or ⁇ alumina), chromium oxide, silicon oxide, diamond, garnet, emery, boron nitride, titanium carbide, silicon carbide, titanium carbide, titanium oxide (rutile or anatase titanium oxide), etc.
  • non-magnetic reinforcing particles such as aluminum oxide ( ⁇ , ⁇ , or ⁇ alumina), chromium oxide, silicon oxide, diamond, garnet, emery, boron nitride, titanium carbide, silicon carbide, titanium carbide, titanium oxide (rutile or anatase titanium oxide), etc.
  • the magnetic layer may contain first particles having electrical conductivity and second particles having a Mohs hardness of 7 or more.
  • the first particles and the second particles may form protrusions on the surface of the magnetic layer.
  • the first particles can prevent an increase in frictional force when the magnetic recording tape is running, and function as, for example, a solid lubricant component.
  • the second particles can also provide an abrasive effect (and an anchor effect) for magnetic head cleaning.
  • the first particles are conductive.
  • fine particles mainly composed of carbon can be used, and for example, preferably carbon particles, and an example of such carbon particles is carbon black.
  • carbon black for example, Asahi #15 and #15HS from Asahi Carbon Co., Ltd. and Seast TA from Tokai Carbon Co., Ltd. can be used.
  • hybrid carbon in which carbon is attached to the surface of silica particles can be used.
  • the average particle size (arithmetic mean value of particle diameter measured using an electron microscope) of the first particles (particularly carbon particles, for example carbon black) may be, for example, preferably 15 nm or more, more preferably 30 nm or more, and even more preferably 50 nm or more.
  • the average particle size may be, for example, preferably 200 nm or less, more preferably 180 nm or less, even more preferably 150 nm or less, 130 nm or less, or 120 nm or less.
  • the numerical range of the average particle size may be appropriately selected from these upper and lower limits, and may be, for example, preferably 50 nm to 200 nm, more preferably 50 nm to 180 nm, even more preferably 50 nm to 150 nm, and even more preferably 50 nm to 130 nm.
  • the second particles may have a Mohs hardness of preferably 7 or more, more preferably 7.5 or more, even more preferably 8 or more, and even more preferably 8.5 or more.
  • the Mohs hardness of the second particles may be, for example, preferably 10 or less, more preferably 9.5 or less. That is, the second particles may be formed from a material having such a Mohs hardness.
  • the second particles may preferably be inorganic particles.
  • the second particles may be, for example, ⁇ -alumina (the ⁇ -conversion rate may be, for example, 90% or more), ⁇ -alumina, ⁇ -alumina, silicon carbide, chromium oxide, cerium oxide, ⁇ -iron oxide, corundum, silicon nitride, titanium carbide, titanium oxide, silicon dioxide, tin oxide, magnesium oxide, tungsten oxide, zirconium oxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide, needle-shaped ⁇ -iron oxide obtained by dehydrating and annealing a raw material of magnetic iron oxide, or those surface-treated with aluminum and/or silica as necessary, or diamond powder, or a combination of two or more of these.
  • the second particles are preferably alumina particles such as ⁇ -alumina, ⁇ -alumina, and ⁇ -alumina, or silicon carbide. These second particles may be of any shape such as needle-shaped, spherical, or cubic, but those having corners in a part of the shape are preferable because they have high abrasiveness, for example.
  • the average particle size (e.g., arithmetic mean value of particle diameter measured using an electron microscope) of the second particles (particularly inorganic particles, for example, alumina) may be, for example, preferably 15 nm or more, more preferably 30 nm or more, and even more preferably 50 nm or more.
  • the average particle size may be, for example, preferably 200 nm or less, more preferably 180 nm or less, even more preferably 150 nm or less, 130 nm or less, or 120 nm or less.
  • the numerical range of the average particle size may be appropriately selected from these upper and lower limits, and may be, for example, preferably 50 nm to 180 nm, more preferably 60 nm to 150 nm, and even more preferably 60 nm to 120 nm.
  • the second particles (particularly inorganic particles, such as alumina) may not be electrically conductive, i.e., the second particles may not be electrically conductive like the first particles.
  • the magnetic layer 13 has multiple data bands d (data bands d0 to d3) that are long in the longitudinal direction (X-axis direction) in which data is written, and multiple servo bands s (servo bands s0 to s4) that are long in the longitudinal direction in which servo patterns 6 are written.
  • the servo bands s are arranged at positions that sandwich each data band d in the width direction (Y-axis direction). It is preferable that the magnetic layer 13 has five or more servo bands s.
  • the ratio of the area of the servo band s to the total surface area of the magnetic layer 13 is typically 4.0% or less.
  • the width of the servo band s is, for example, 98 ⁇ m or less for a 1/2 inch tape width.
  • the ratio of the area of the servo band s to the total surface area of the magnetic layer 13 can be measured, for example, by developing the magnetic recording medium using a developer such as a ferricolloid developer, and then observing the developed magnetic recording medium with an optical microscope.
  • the number of data bands d is four, and the number of servo bands s is five. Note that the number of data bands d and the number of servo bands s can be changed as appropriate.
  • the data band d includes a plurality of recording tracks 5 that are long in the longitudinal direction and aligned in the width direction.
  • the number of recording tracks 5 included in one data band d is, for example, about 1000 to 2500.
  • Data is recorded along and within the recording tracks 5.
  • the length of one bit in the longitudinal direction of the data recorded in the data band d is, for example, 48 nm or less.
  • the servo band s includes a servo pattern 6 of a predetermined shape that is recorded by a servo pattern recording device described below.
  • the number of recording tracks 5 increases with each generation of LTO-standard magnetic recording media, dramatically improving recording capacity.
  • the original LTO-1 had 384 recording tracks 5, but the numbers of recording tracks 5 in LTO-2 to LTO-8 are 512, 704, 896, 1280, 2176, 3584, and 6656, respectively.
  • data recording capacity was 100GB (gigabytes) in LTO-1, but is 200GB, 400GB, 800GB, 1.5TB (terabytes), 2.5TB, 6.0TB, and 12TB, respectively, in LTO-2 to LTO-8.
  • the number of recording tracks 5 and the recording capacity are not particularly limited and can be changed as appropriate. However, it is advantageous to apply this to magnetic recording media that have a large number of recording tracks 5 and a large recording capacity (for example, 6656 tracks or more, 12 TB or more: LTO8 and later) and are susceptible to variations in the width of the magnetic recording medium.
  • a magnetic tape with an overall Young's modulus of the tape (Young's modulus in the longitudinal direction of the tape) of 8 GPa or less is applied as the magnetic tape recording medium.
  • FIG. 5 is an enlarged view showing an example of a recording track (data track) 5 in a data band d of a magnetic recording medium conforming to the LTO standard up to the LT09 standard.
  • the recording tracks 5 are long in the longitudinal direction, aligned in the width direction, and each track has a predetermined recording track width (data track width) Wd in the width direction.
  • This recording track width Wd is set to 2.0 ⁇ m or less in LTO-8.
  • the upper limit of the average value of the recording track width (data track width) Wd is preferably 1200 nm or less, more preferably 1000 nm or less, even more preferably 800 nm or less, and particularly preferably 600 nm or less.
  • the lower limit of the average value of the recording track width (data track width) Wd is preferably 20 nm or more, taking into account the magnetic particle size.
  • the recording track width Wd can be measured, for example, by developing the magnetic layer 13 of the magnetic recording medium 10 using a developer such as a ferric colloid developer, and then observing the developed magnetic layer 13 of the magnetic recording medium 10 with an optical microscope.
  • the drive head can be set in a Read While Write state to ignore fluctuations during tape running, and the recording track width Wd can be measured from the change in output when the azimuth of the drive head is changed.
  • FIG. 6 is an enlarged view showing a part of an example of a servo pattern 6 written in a servo band s of a magnetic recording medium conforming to the LTO standard up to the LT09 standard.
  • the servo pattern 6 includes a plurality of stripes inclined at a predetermined azimuth angle ⁇ with respect to the width direction (Y-axis direction), the details of which will be described later.
  • the plurality of stripes are classified into a first stripe group 61 and a second stripe group 62 inclined clockwise with respect to the width direction (Y-axis direction) and a second stripe group 62 inclined counterclockwise with respect to the width direction.
  • the first stripe group 61 and the second stripe group 62 typically include four or five stripes.
  • the shape of the servo pattern 6 can be measured, for example, by developing the magnetic layer 13 of the magnetic recording medium 10 using a developer such as a ferricolloid developer, and then observing the developed magnetic layer 13 of the magnetic recording medium 10 with an optical microscope.
  • the servo band s may be a servo band for tilting the recording and reproducing head of the drive.
  • the servo trace lines TL which are lines traced on the servo pattern 6 by the servo read head 132 described later, are shown by dashed lines.
  • the servo trace lines TL are set along the longitudinal direction (X-axis direction) and are also set at a predetermined interval Ps in the width direction.
  • the number of servo trace lines TL per servo band s is, for example, about 30 to 60.
  • the spacing Ps between two adjacent servo trace lines TL is the same as the recording track width Wd, and is, for example, 2.0 ⁇ m or less.
  • the spacing Ps between two adjacent servo trace lines TL is a value that determines the recording track width Wd. In other words, when the spacing Ps between the servo trace lines TL is narrowed, the recording track width Wd becomes smaller and the number of recording tracks 5 included in one data band d increases. As a result, the data recording capacity increases.
  • the undercoat layer 12 is a non-magnetic layer containing non-magnetic powder and a binder as the main components. If necessary, the undercoat layer 12 may further contain at least one additive selected from the group consisting of other particles, lubricants, hardeners, and rust inhibitors.
  • the non-magnetic powder contained in the undercoat layer 12 includes, for example, at least one type selected from inorganic particles and organic particles, and particularly includes at least one type selected from inorganic particles.
  • One type of non-magnetic powder may be used alone, or two or more types of non-magnetic powder may be used in combination.
  • the non-magnetic inorganic particles may be, for example, one or a combination of two or more types selected from metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides.
  • the inorganic particles may be, for example, one or two or more types selected from iron oxide, aluminum oxide, carbon black, iron oxyhydroxide, hematite, titanium oxide, silicon oxide, titanium carbide, silicon carbide, diamond, and calcium carbonate.
  • the shape of the non-magnetic powder may be, for example, various shapes such as needle-like, spherical, cubic, and plate-like, but is not particularly limited to these.
  • the non-magnetic powder contains at least iron oxide, in particular acicular iron oxide.
  • the non-magnetic powder may further contain carbon black and/or aluminum oxide.
  • the average major axis length of the iron oxide may be, for example, preferably 0.01 ⁇ m or more, more preferably 0.04 ⁇ m or more, and even more preferably 0.07 ⁇ m or more.
  • the average major axis length may be, for example, preferably 0.5 ⁇ m or less, more preferably 0.4 ⁇ m or less, and even more preferably 0.3 ⁇ m or less.
  • the average particle size of the carbon black may be, for example, preferably 10 nm or more, more preferably 12 nm or more, and even more preferably 15 nm or more.
  • the average particle size of the carbon black may be, for example, preferably 250 nm or less, more preferably 150 nm or less, and even more preferably 100 nm or less.
  • the carbon black content may be, for example, preferably 15 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 25 parts by mass or more, per 100 parts by mass of the iron oxide.
  • the carbon black content may be, for example, preferably 45 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 35 parts by mass or less, per 100 parts by mass of the iron oxide.
  • the average particle size of the aluminum oxide may be, for example, preferably 30 nm or more, more preferably 40 nm or more, and even more preferably 60 nm or more.
  • the average particle size of the aluminum oxide may be, for example, preferably 180 nm or less, more preferably 150 nm or less, and even more preferably 120 nm or less.
  • the content of aluminum oxide may be, for example, preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, per 100 parts by mass of the iron oxide.
  • the content of aluminum oxide may be, for example, preferably 10 parts by mass or less, more preferably 9 parts by mass or less, and even more preferably 8 parts by mass or less, per 100 parts by mass of the iron oxide.
  • the underlayer contains a binder.
  • the above description of the binder contained in the magnetic layer 13 also applies to the binder contained in the underlayer 12.
  • the undercoat layer includes at least a chlorine-containing binder.
  • the chlorine-containing binder may be a chlorine-containing resin.
  • the chlorine-containing resin is a resin that includes a chlorine atom as at least one of the elements constituting the resin.
  • the chlorine-containing binder is, for example, a vinyl chloride resin.
  • chlorine-containing binder examples include polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-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, vinylidene chloride-acrylonitrile copolymer, and synthetic rubber.
  • the underlayer contains a chlorine-containing binder adsorbed to the non-magnetic powder and a chlorine-containing binder not adsorbed to the non-magnetic powder.
  • the distribution state of the chlorine-containing binder not adsorbed to the non-magnetic powder in the underlayer is affected by the solvent contained in the paint for forming the magnetic layer and the paint drying process during the magnetic layer formation process in the manufacturing process of the magnetic recording medium. By controlling the distribution state according to this technology, the reliability of the magnetic recording medium can be improved.
  • the content by volume of the chlorine-containing binder in the undercoat layer may be, for example, an amount equivalent to 20% by volume or more of the non-magnetic powder volume (particularly the total volume of the non-magnetic powder), preferably 30% by volume or more, more preferably 40% by volume or more.
  • the content by volume may be, for example, an amount equivalent to 180% by volume or less of the non-magnetic powder volume (particularly the total volume of the non-magnetic powder), preferably 170% by volume or less, more preferably 160% by volume or less.
  • the volume of the chlorine-containing binder in the underlayer may be, for example, preferably 20 to 180, more preferably 30 to 170, and even more preferably 40 to 160.
  • the undercoat layer contains iron oxide as a non-magnetic powder.
  • the content of the chlorine-containing binder in the undercoat layer may be, for example, preferably 20 parts by mass or more, more preferably 25 parts by mass or more, and even more preferably 30 parts by mass or more, per 100 parts by mass of the iron oxide.
  • the content may be, for example, preferably 70 parts by mass or less, more preferably 65 parts by mass or less, and even more preferably 60 parts by mass or less, per 100 parts by mass of the iron oxide.
  • the undercoat layer may further contain a chlorine-free binder in addition to the chlorine-containing binder.
  • the chlorine-free binder may be a chlorine-free resin.
  • the chlorine-free resin may contain, for example, a polyurethane-based resin.
  • the polyurethane-based resin may be, for example, a urethane-modified copolymer polyester.
  • the urethane-modified copolymer polyester may be a urethane-modified copolymer polyester having an aromatic polyester as a basic skeleton and a urethane component in the side chain, or a urethane-modified copolymer polyester containing an ester repeat unit and a urethane repeat unit in the basic skeleton.
  • the content by volume of the chlorine-free binder in the undercoat layer may be, for example, an amount equivalent to 0% or more of the volume of the non-magnetic powder (particularly the total volume of the non-magnetic powder), preferably 10% or more, more preferably 20% or more.
  • the content by volume may be, for example, an amount equivalent to 150% or less of the volume of the non-magnetic powder (particularly the total volume of the non-magnetic powder), preferably 140% or less, more preferably 130% or less.
  • the undercoat layer may not contain the chlorine-free binder.
  • the volume of the chlorine-containing binder in the underlayer may be, for example, preferably 0 to 150, more preferably 10 to 140, and even more preferably 200 to 130.
  • the undercoat layer contains iron oxide as a non-magnetic powder.
  • the content of the chlorine-free binder in the undercoat layer may be, for example, preferably 0 parts by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of the iron oxide.
  • the content may be, for example, preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and even more preferably 20 parts by mass or less, per 100 parts by mass of the iron oxide.
  • the underlayer may contain a lubricant.
  • the lubricant may be, for example, one or more selected from fatty acids and/or fatty acid esters, and the lubricant may preferably be a compound represented by general chemical formula (1) or general chemical formula (2), or general chemical formula (3) or general chemical formula (4) or general chemical formula (5) described above with respect to the magnetic layer. One or more of these compounds may be included.
  • the lubricant may be, for example, an ester of a monobasic fatty acid having 10 to 24 carbon atoms with any one of monohydric to hexahydric alcohols having 2 to 12 carbon atoms, a mixed ester thereof, a difatty acid ester, a trifatty acid ester, etc.
  • 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, octyl stearate, isooctyl stearate, octyl myristate, etc.
  • the magnetic layer may contain any one or more of these.
  • the content of the lubricant in the undercoat layer may be, for example, preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2 parts by mass or more, per 100 parts by mass of non-magnetic powder (100 parts by mass of total amount of non-magnetic powder).
  • the content may be, for example, preferably 12 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less, per 100 parts by mass of non-magnetic powder (100 parts by mass of total amount of non-magnetic powder).
  • the above numerical range may be applied, for example, when the non-magnetic powder contains iron oxide.
  • the undercoat layer contains iron oxide as a non-magnetic powder.
  • the content of the lubricant in the undercoat layer may be, for example, preferably 2 parts by mass or more, more preferably 2.5 parts by mass or more, and even more preferably 3 parts by mass or more, per 100 parts by mass of the iron oxide.
  • the content may be, for example, preferably 8 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 6 parts by mass or less, per 100 parts by mass of the iron oxide.
  • the back layer 14 may contain a binder and a non-magnetic powder.
  • the back layer 14 may contain various additives such as a lubricant, a hardener, and an antistatic agent as necessary.
  • a lubricant such as a lubricant, a hardener, and an antistatic agent as necessary.
  • the above description of the binder and non-magnetic powder contained in the non-magnetic layer 12 also applies to the binder and non-magnetic powder contained in the back layer 14.
  • the average particle size of the inorganic particles contained in the back layer 14 is preferably 10 nm or more and 150 nm or less, more preferably 15 nm or more and 110 nm or less.
  • the average particle size of the inorganic particles is determined in the same manner as the average particle size D of the magnetic powder described above.
  • the thickness of the portion of the underlayer 12 of the magnetic recording medium 10 where the chlorine count is equal to or greater than the threshold value described below is, for example, 130 nm or less, as described above.
  • [Threshold] [average chlorine count in the undercoat layer] + 6 ⁇ [standard deviation obtained when calculating the average chlorine count]
  • the thickness of this portion is the thickness of a region where the chlorine count is equal to or greater than the threshold value, as determined by measuring the chlorine count across the thickness direction of the underlayer using a STEM (scanning transmission electron microscope).
  • the method for measuring the thickness of the portion is as follows.
  • a portion of the tape-shaped magnetic recording medium housed in a magnetic recording cartridge which is about 20 m from the outermost portion in the tape longitudinal direction, is used.
  • the magnetic tape T housed in a cartridge such as the cartridge 10A described later is unwound, and a portion about 20 m from the connection portion 221 between the magnetic tape T and the leader tape LT in the longitudinal direction is used to prepare a sample.
  • a substantially central portion in the width direction of the magnetic tape T is cut out to a size appropriate for preparing a sample for STEM observation (e.g., a rectangle of about 1 mm x about 1 mm).
  • a carbon deposition process is applied to the surface of the cut sample, and a carbon deposition film is formed on the magnetic surface.
  • the sample that has been subjected to this process is introduced into a focused ion beam (FIB) processing device equipped with a scanning electron microscope (SEM). From the sample that has been subjected to this process, the processing device microsamples minute pieces having a size appropriate for STEM observation (e.g., a rectangle of 10 ⁇ m to 50 ⁇ m on a side). The minute piece is fixed to the sample stage of the processing device and thinned. The thinning is performed so that the thickness of the minute piece in the direction parallel to the magnetic surface is a thickness that allows the electron beam used in STEM observation to pass through.
  • FIB focused ion beam
  • SEM scanning electron microscope
  • STEM device FEI Talos F200X (Schottky-FEG)
  • EDX system FEI Super-X EDX detector: 4 windowless SDD detectors (30 mm 2 , objective lens built-in) manufactured by Bruker
  • Acceleration voltage 200 kV
  • Acquired image BF STEM image (Bright Field: BF)
  • HAADF STEM image High Angle Annular Dark Field:HAADF
  • Camera length 98mm
  • Display magnification 57,000x
  • Acceleration voltage 200 kV
  • Display magnification 57,000x
  • Surface analysis resolution 800 pixels x 700 pixels (1 pixel is equivalent to approximately 2.1 nm.)
  • Moving average filter 3 pixels
  • Data type Net count Cl K ⁇ ray extraction integrated width x thickness length: 700 pixels x 650 pixels
  • the "length in the thickness direction" is the length of the side of a rectangle that defines the region in which Cl K ⁇ rays are extracted, the side being approximately parallel to the thickness direction of the magnetic recording medium.
  • the K ⁇ net count of Cl at a certain position in the thickness direction of the magnetic recording medium corresponds to the amount of Cl at that position. Therefore, the distribution state of the chlorine content can be grasped based on the K ⁇ net count of Cl. Note that the energy of the K ⁇ ray of the characteristic X-ray generated when Cl is irradiated with an electron beam is 2.62 keV.
  • a HAADF STEM image of the STEM observation sample is obtained in a direction parallel to the magnetic surface.
  • An example of the obtained HAADF STEM image is shown in FIG. 3A.
  • the magnetic layer M and the underlayer U can be confirmed from the image.
  • the STEM cross-sectional photograph is checked to confirm that there are no parts in the cross section of the underlayer that are clearly different from the normal state of the underlayer.
  • Such parts are, for example, coarse inorganic particles, voids, or undispersed binder, and the analysis is performed on a cross section that does not contain such parts.
  • a K ⁇ ray extraction region A ex region surrounded by a white rectangle
  • the K ⁇ ray extraction region is a rectangle, particularly a rectangle.
  • the length of one side of the rectangle in the horizontal direction is 700 pixels, which is the above-mentioned "Cl K ⁇ ray extraction integrated width", that is, the length of the rectangular area in which Cl K ⁇ ray extraction is performed in a direction approximately horizontal to the magnetic surface of the magnetic recording medium.
  • the width indicated by the double-headed arrow L a is the Cl K ⁇ ray extraction integrated width.
  • the length of one vertical side of the rectangle is 650 pixels, which is the above-mentioned “length in the thickness direction.”
  • the length indicated by the double-headed arrow Lb is the length in the thickness direction.
  • the magnetic layer and the underlayer can be identified by visual observation of the HAADF image.
  • the rectangle set as the Cl K ⁇ ray extraction region is set so that the side corresponding to the Cl K ⁇ ray extraction integrated width is approximately parallel to the visually identified magnetic layer surface, and the rectangle covers the carbon deposition film, the magnetic layer, the underlayer, and the base layer. In actual setting, it is not necessary to draw the white lines shown in the figure.
  • (iv) Identification of the Magnetic Layer Surface The fact that the carbon deposition film does not contain chlorine is utilized to identify the magnetic layer surface in the chlorine count extraction region. To identify the magnetic layer surface, first, the carbon deposition film portion is identified. The carbon deposition film portion can be roughly identified from the plot. For example, since the peak on the left side of the plot in FIG. 3C corresponds to the magnetic layer portion, the portion with a low net count number on the left side of the magnetic layer portion is the carbon deposition film portion. Then, the average value (simple average value) of the net count number of the first 6 nm portion starting from the net count number of 0 is identified as the background value.
  • the position (pixel position in the thickness direction) where the net count number exceeding the background value is recorded in the plot generated in (ii) above is determined as the position of the magnetic layer surface.
  • the position of the magnetic layer surface For example, in FIG. 3C, moving to the right from the 0 nm point on the extraction position axis, there is an extraction position data point where the background value is recorded.
  • the extraction position of the data point immediately to the right of the extraction position data point is the position of the magnetic layer surface.
  • the first position within the 6 nm where the moving average value is equal to or greater than the threshold value is determined as the "start point on the magnetic surface side of the portion where the chlorine count is equal to or greater than the threshold value."
  • An example of the start point is shown in FIG. 3E.
  • the interface between the undercoat layer and the base layer is identified. As the chlorine counts move further from the starting point toward the base layer, they begin to decrease.
  • the first position at which the chlorine counts become lower than the "average chlorine counts in the undercoat layer” is determined as the "interface between the undercoat layer and the base layer.”
  • An example of the position of the interface is also shown in FIG. 3E.
  • the position of the interface may be identified as the first position where the chlorine count becomes lower than the average chlorine count in the underlayer, as described above.
  • the base layer is made of a material that contains chlorine. In this case, when the chlorine count of the base layer is different from the net chlorine K ⁇ count of the average part of the underlayer, the position of the interface may be identified based on the difference.
  • the length from the "start point on the magnetic surface side of the portion where the chlorine count is equal to or greater than the threshold value" to the "interface between the underlayer and the base layer” specified as above is defined as the "thickness of the portion of the underlayer where the chlorine count is equal to or greater than the threshold value.”
  • An example of this portion is also shown in FIG. 3E.
  • a peak portion corresponding to the magnetic layer can be seen on the left side of the plot.
  • the maximum value of the chlorine count number in this peak portion is the "peak chlorine count number in the magnetic layer.”
  • the absolute value of the average width change ⁇ A of the magnetic recording medium before and after being left to stand for 40 hours in an environment of a temperature of 50°C and a relative humidity of 40% RH with a tension of 0.55 N applied in the longitudinal direction per 1/2 inch of width of the magnetic recording medium 10 is 170 ppm or less, preferably 140 ppm or less, more preferably 70 ppm or less, and even more preferably 40 ppm or less.
  • the absolute value of the average width change ⁇ A of the magnetic recording medium (hereinafter referred to as "magnetic tape") wound in a magnetic recording cartridge is found as follows. First, the 1/2 inch wide magnetic tape T housed in cartridge 10A is unwound, and the magnetic tape MT is cut to a length of 250 mm from each of the ranges of 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m in the longitudinal direction from the connection 221 between the magnetic tape T and the leader tape LT, to obtain three samples.
  • the absolute values of the width change amount ⁇ A of the above three samples are obtained as follows.
  • a measuring device shown in FIG. 7 is prepared, incorporating a Keyence digital dimension measuring device LS-7000 as the measuring device, and the sample 10S is set on this measuring device. Specifically, one end of the long sample (magnetic tape T) 10S is fixed by a fixing part 231.
  • the sample 10S is placed on five roughly cylindrical and rod-shaped support members 2321-2325.
  • the sample 10S is placed on these support members 2321-2325 so that its back surface is in contact with the five support members 2321-2325. All of the five support members 2321-2325 (particularly their surfaces) are made of stainless steel SUS304, and their surface roughness Rz (maximum height) is 0.15 ⁇ m to 0.3 ⁇ m.
  • the arrangement of the five rod-shaped support members 2321-2325 will be described with reference to FIG. 7. As shown in FIG. 7, the sample 10S is placed on the five support members 2321-2325.
  • the five support members 2321-2325 are hereinafter referred to as the "first support member 2321", “second support member 2322", “third support member 2323” (having slit 232A), "fourth support member 2324", and "fifth support member 2325" (closest to weight 233) from the one closest to the fixed portion 231.
  • the diameter of each of these five first to fifth support members 2321-2325 is 7 mm.
  • the distance d1 between the first support member 2321 and the second support member 2322 (particularly the distance between the central axes of these support members) is 20 mm.
  • the distance d2 between the second support member 2322 and the third support member 2323 is 30 mm.
  • the distance d3 between the third support member 2323 and the fourth support member 2324 is 30 mm.
  • the distance d4 between the fourth support member 2324 and the fifth support member 2325 is 20 mm.
  • the third support member 2323 is fixed so as not to rotate, but the other four first, second, fourth and fifth support members 2321, 2322, 2324 and 2325 are all rotatable.
  • the support member 2323 is fixed so as not to rotate, the contact angle between the support 2323 and the sample 10S is made shallow in consideration of reducing friction between the support 2323 and the sample 10S.
  • the sample 10S is held on the support members 2321-2325 so that it does not move in the width direction of the sample 10S.
  • the support member 2323 which is located between the light emitter 234 and the light receiver 235 and is located approximately in the center between the fixed part 231 and the part where the load is applied, has a slit 232A.
  • Light L is irradiated from the light emitter 234 to the light receiver 235 through the slit 232A.
  • the slit width of the slit 232A is 1 mm, and the light L can pass through the slit 232A without being blocked by the frame of the slit 232A.
  • a weight 233 is attached to the other end of the sample 10S to apply a load of 0.55N per 1/2 inch of the width of the sample 10S. That is, the load applied to the sample 10S is set to 0.55N when the width is 1/2 inch, and a load proportional to the width is set when the width is not 1/2 inch.
  • the sample 10S is left to stand for 30 minutes in the above room temperature environment. After leaving it to stand for 30 minutes, the temperature inside the chamber is raised, and measurement of the width of the sample 10S is started when the inside of the chamber reaches the specified environment (temperature 50°C, relative humidity 40% RH). While maintaining the inside of the chamber in the above specified environment (temperature 50°C, relative humidity 40% RH), measurement of the width of the sample 10S is continued until 40 hours have passed since the start of the measurement.
  • the measuring device irradiates light L from the light emitter 234 to the light receiver 235 with a load of 0.55 N applied in the specified environment, and measures the width of the sample 10S to which a load is applied in the longitudinal direction. The width is measured when the sample 10S is not curled.
  • the light emitter 234 and the light receiver 235 are provided in the digital dimension measuring instrument LS-7000.
  • the absolute value of the width change amount ⁇ A of the sample 10S after 40 hours from the start of the measurement is calculated based on the width of the sample 10S after 1 hour from the start of the measurement (i.e., after 1 hour from the time when the inside of the chamber becomes the specified environment). That is, the absolute value of the width change amount ⁇ A of the sample 10S is obtained by subtracting the width of the sample 10S after 1 hour from the width of the sample 10S after 40 hours.
  • the positive and negative values of the width change amount ⁇ A of the sample 10S indicate the direction of the width change.
  • the width change amount ⁇ A When the width change amount ⁇ A is positive, it indicates that the width of the sample 10S has changed in the direction of widening, and when it is negative, it indicates that the width of the sample 10S has changed in the direction of narrowing.
  • the absolute values of the width change amount ⁇ A of the three samples 10S calculated as described above are arithmetically averaged to obtain the absolute value of the average width change amount ⁇ A of the magnetic tape T.
  • the average thickness tT of the magnetic recording medium 10 (hereinafter also referred to as magnetic tape T) is obtained as follows. First, the magnetic tape T housed in a cartridge such as the cartridge 10A described below is unwound, and the magnetic tape T is cut into a length of 250 mm at a position 30 m in the longitudinal direction from the joint 221 between the magnetic tape T and the leader tape LT to prepare a sample. Next, the thickness of the sample is measured at five positions using a Mitutoyo Laser Hologram (LGH-110C) as a measuring device, and the measured values are simply averaged (arithmetic average) to calculate the average thickness tT [ ⁇ m]. The five measurement positions are selected randomly from the sample so that they are different positions in the longitudinal direction of the magnetic tape T.
  • LGH-110C Mitutoyo Laser Hologram
  • the average thickness of the underlayer 12 is obtained as follows. First, the magnetic tape T housed in a cartridge such as the cartridge 10A described below is unwound, and the magnetic tape T is cut into three samples of 250 mm length at three positions, 10 m, 30 m, and 50 m from the connection 221 between the magnetic tape T and the leader tape LT in the longitudinal direction. Then, each sample is processed by FIB method or the like to be thinned. When the FIB method is used, a carbon layer and a tungsten layer are formed as a protective film as a pretreatment for observing the TEM image of the cross section described below.
  • the carbon layer is formed by deposition on the surface of the magnetic tape T on the magnetic layer 13 side and the surface on the back layer 14 side, and the tungsten layer is further formed on the surface on the magnetic layer 13 side by deposition or sputtering.
  • the thinning is performed along the longitudinal direction of the magnetic tape T. That is, the thinning forms a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic tape T.
  • TEM transmission electron microscope
  • Equipment TEM (H9000NAR manufactured by Hitachi) Acceleration voltage: 300 kV
  • Magnification 100,000x
  • the thickness of the underlayer 12 is measured at at least 10 or more points in the longitudinal direction of the magnetic tape T, and then the measured values are simply averaged (arithmetic averaged) to obtain the average thickness (nm) of the underlayer 12.
  • the average thickness of the base layer 11 is determined as follows. First, the magnetic tape T housed in a cartridge, such as the magnetic recording cartridge 10A described below, is unwound, and a sample is prepared by cutting the magnetic tape T to a length of 250 mm at a position 30 m in the longitudinal direction from the connection 221 between the magnetic tape T and the leader tape LT.
  • the "longitudinal direction" in the “longitudinal direction from the connection between the magnetic tape T and the leader tape LT” refers to the direction from one end on the leader tape LT side to the other end on the opposite side.
  • the non-magnetic layer (underlayer) 12, the magnetic layer 13, and the back layer 14 are removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid.
  • a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid.
  • the thickness of the sample (base layer 11) is measured at five positions, and the measured values are simply averaged (arithmetic mean) to calculate the average thickness of the base layer 11. Note that the five measurement positions are selected randomly from the sample so that they are each different positions in the longitudinal direction of the magnetic tape T.
  • the average thickness t b of the back layer 14 is obtained as follows. First, the average thickness (average total thickness) t T of the magnetic tape T is measured. The method for measuring the average thickness t T (average total thickness) is as described above. Next, the magnetic tape T housed in the cartridge 10A is unwound, and the magnetic tape T is cut into a length of 250 mm at a position 30 m in the longitudinal direction from the joint 221 between the magnetic tape T and the leader tape LT to prepare a sample. Next, the back layer 14 of the sample is removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid.
  • MEK methyl ethyl ketone
  • the thickness of the sample is measured at five positions using a Mitutoyo laser hologram (LGH-110C), and the measured values are simply averaged (arithmetic average) to calculate the average value t B [ ⁇ m]. Then, the average thickness t b [ ⁇ m] of the back layer 14 is obtained from the following formula.
  • the average thickness t m of the magnetic layer 13 is obtained as follows. First, the magnetic tape T housed in the cartridge 10A is unwound, and the magnetic tape T is cut into three samples of 250 mm length at three positions, 10 m, 30 m, and 50 m from the connection 221 between the magnetic tape T and the leader tape LT in the longitudinal direction. Then, each sample is processed by FIB method or the like to be thinned. When the FIB method is used, a carbon layer and a tungsten layer are formed as a protective film as a pretreatment for observing a TEM image of a cross section, which will be described later.
  • the carbon layer is formed by a vapor deposition method on the surface of the magnetic tape T on the magnetic layer 13 side and the surface on the back layer 14 side, and the tungsten layer is further formed by a vapor deposition method or a sputtering method on the surface on the magnetic layer 13 side.
  • the thinning is performed along the longitudinal direction of the magnetic tape T. That is, the thinning forms a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic tape T.
  • the thickness of the magnetic layer 13 is measured at 10 positions of each sliced sample.
  • the 10 measurement positions of each sliced sample are randomly selected from the sample so that they are different positions in the longitudinal direction of the magnetic tape T.
  • the average value obtained by simply averaging (arithmetic mean) the measured values of each of the obtained sliced samples (a total of 30 thicknesses of the magnetic layer 13) is defined as the average thickness t m [nm] of the magnetic layer 13.
  • the squareness ratio Rs1 measured in the longitudinal direction of the magnetic tape T is preferably 35% or less, more preferably 30% or less, even more preferably 25% or less, particularly preferably 20% or less, and most preferably 15% or less.
  • the magnetic powder has a sufficiently high vertical orientation, so that a better SNR can be obtained. Therefore, better electromagnetic conversion characteristics can be obtained.
  • the servo signal shape is improved, making it easier to control on the drive side.
  • the squareness ratio Rs1 in the longitudinal direction of the magnetic tape is obtained as follows. First, the magnetic tape contained in the cartridge is unwound, and six magnetic tapes are cut out at a position 30 to 40 m in the longitudinal direction from one end of the outer periphery of the magnetic tape. At this time, marking is performed with any non-magnetic ink so that the longitudinal direction (running direction) of the magnetic tape can be recognized. Next, the three cut-out magnetic tapes are superimposed with double-sided tape so that the longitudinal directions of the three cut-out magnetic tapes are the same, and then punched out with a ⁇ 6.39 mm punch to prepare a measurement sample.
  • the M-H loop of the measurement sample (whole magnetic tape) corresponding to the longitudinal direction of the magnetic tape (longitudinal direction of the magnetic tape) is measured using a vibrating sample magnetometer (VSM).
  • VSM vibrating sample magnetometer
  • the coatings (undercoat layer, magnetic layer, back layer, etc.) of the remaining three cut-out magnetic tapes are wiped off with acetone or ethanol, etc., leaving only the base layer.
  • Three of the obtained base layers are laminated with double-sided tape, and then punched out with a ⁇ 6.39 mm punch to prepare a sample for background correction (hereinafter, simply "correction sample").
  • the M-H loop of the correction sample (base layer) corresponding to the longitudinal direction of the base layer (longitudinal direction of the magnetic tape) is measured using a VSM.
  • the MH loop of the measurement sample (entire magnetic tape) and the MH loop of the correction sample (base layer) are measured using a high-sensitivity vibration sample magnetometer "VSM-P7-15 type" manufactured by Toei Industry Co., Ltd.
  • the measurement conditions are as follows: 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, number of MH averages: 20.
  • the M-H loop of the measurement sample (whole magnetic tape) and the M-H loop of the correction sample (base layer) are obtained, the M-H loop of the correction sample (base layer) is subtracted from the M-H loop of the measurement sample (whole magnetic tape) to perform background correction and obtain the M-H loop after background correction.
  • the measurement and analysis program attached to the "VSM-P7-15 type" is used for the calculation of this background correction. Note that all of the above M-H loop measurements are performed at 25°C ⁇ 2°C and 50% RH ⁇ 5% RH. Also, when measuring the M-H loop in the longitudinal direction of the magnetic tape, "demagnetization field correction" is not performed.
  • the M-H loop may be measured by stacking multiple samples to be measured according to the sensitivity of the VSM used.
  • a method for manufacturing the magnetic recording medium 10 having the above-mentioned configuration will be described.
  • a paint for forming the base layer is prepared by kneading and/or dispersing non-magnetic powder, binder, etc. in a solvent.
  • a paint for forming the magnetic layer is prepared by kneading and/or dispersing magnetic powder, non-magnetic particles, binder, etc. in a solvent.
  • the following solvents, dispersing devices, and kneading devices can be used, for example, to prepare the paint for forming the magnetic layer and the paint for forming the base layer (non-magnetic layer).
  • Solvents used in the preparation of the above-mentioned paints include, for example, ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohol-based solvents such as methanol, ethanol, and propanol; ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, propyl acetate, ethyl lactate, and ethylene glycol acetate; ether-based solvents such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran, and dioxane; aromatic hydrocarbon-based solvents such as benzene, toluene, and xylene; and halogenated hydrocarbon-based solvents such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, and chlorobenzene.
  • the kneading device used in the above-mentioned paint preparation may be, for example, a continuous twin-screw kneader, a continuous twin-screw kneader capable of dilution in multiple stages, a kneader, a pressure kneader, a roll kneader, or the like, but is not limited to these devices.
  • the dispersing device used in the above-mentioned paint preparation may be, for example, a bead mill, 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 (such as the "DCP Mill” manufactured by Eirich), a homogenizer, or an ultrasonic dispersing machine, but is not limited to these devices.
  • a paint for forming the undercoat layer is applied to one main surface of the base layer 11 and dried to form the undercoat layer 12.
  • a paint for forming the magnetic layer is applied onto this undercoat layer 12 and dried to form the magnetic layer 13 on the non-magnetic layer 12.
  • the thickness and/or position of the portion where the chlorine count is equal to or greater than the threshold value described below can be adjusted by adjusting the method of forming the magnetic layer and/or the base layer and/or the composition of the paint for forming the magnetic layer and/or the paint for forming the base layer.
  • the thickness and/or the position of the portion where the chlorine count is equal to or greater than the threshold value can be adjusted, for example, by adjusting the drying temperature of the paint for forming the magnetic layer and/or the paint for forming the undercoat layer. For example, lowering the drying temperature makes the thickness wider, and conversely, increasing the drying temperature makes the thickness narrower on the base layer side.
  • the thickness and/or the position of the portion can be adjusted by modifying the non-magnetic powder contained in the base layer coating material with a surface modifier.
  • the amount of binder adsorbed to the non-magnetic powder can be adjusted by modifying the surface with a surface modifier.
  • An example of the modifier is a polycarboxylic acid.
  • the thickness and/or the position of the part can be adjusted. For example, if the time is longer, the binder is less likely to move in the undercoat layer when the magnetic layer paint is applied, and the thickness becomes wider.
  • the binder is more likely to move in the undercoat layer when the magnetic layer paint is applied, and the thickness can be made narrower by being present on the base layer side.
  • the thickness of the portion can also be adjusted by the solids concentration of the paint for forming the magnetic layer and/or the paint for forming the undercoat layer. For example, if the solids concentration of the paint for forming the magnetic layer is high, the amount of solvent that seeps into the undercoat layer when the paint for forming the magnetic layer is applied is reduced, and the thickness of the portion becomes wider. Conversely, if the solids concentration is low, the thickness of the portion becomes smaller.
  • the thickness of the portion can also be adjusted by changing the ratio of the non-magnetic powder to the binder in the coating material for forming the undercoat layer. For example, by increasing the amount of binder, the amount of binder that does not adhere to the non-magnetic powder increases, and the thickness of the portion becomes thicker. Conversely, by decreasing the amount of binder, the thickness of the portion can be made thinner.
  • the magnetic powder When drying, the magnetic powder is magnetically oriented in the thickness direction of the base layer 11, for example, by a solenoid coil. Also, when drying, the magnetic powder may be magnetically oriented in the longitudinal direction (running direction) of the base layer 11, for example, by a solenoid coil, and then magnetically oriented in the thickness direction of the base layer 11.
  • a solenoid coil By performing such a magnetic field orientation process, it is possible to reduce the ratio Hc2/Hc1 of the coercive force in the vertical direction "Hc1" to the coercive force in the longitudinal direction "Hc2", and to improve the degree of vertical orientation of the magnetic powder.
  • a back layer 14 is formed on the other main surface of the base layer 11. This results in a magnetic recording medium 10.
  • the ratio Hc2/Hc1 is set to a desired value by, for example, adjusting the strength of the magnetic field applied to the coating of the magnetic layer-forming paint, the concentration of the solids in the magnetic layer-forming paint, and the drying conditions (drying temperature and drying time) of the coating of the magnetic layer-forming paint.
  • the strength of the magnetic field applied to the coating is preferably between two and three times the holding power of the magnetic powder.
  • the methods for adjusting the ratio Hc2/Hc1 may be used alone or in combination of two or more.
  • the obtained magnetic recording medium 10 is rewound on a large diameter core and subjected to a hardening process. Finally, the magnetic recording medium 10 is subjected to a calendar process and then cut to a predetermined width (e.g., 1/2 inch width). In this manner, the desired long and thin magnetic recording medium 10 is obtained.
  • a predetermined width e.g., 1/2 inch width
  • the magnetic recording medium 10 may be demagnetized, and then multiple servo patterns adjacent to each other in the width direction of the magnetic recording medium 10 may be written in the magnetic layer 13 of the magnetic recording medium 10.
  • the magnetic recording medium 10 may be run, the temperatures of the multiple recording sections of the servo write head may be individually adjusted, and multiple servo patterns may be written in the magnetic layer 13 by the multiple recording sections.
  • FIG. 8 shows a tape drive device 30.
  • the tape drive device 30 is a data recording/playback device capable of recording data on a magnetic tape T or playing back data recorded on a magnetic tape T.
  • the tape drive device 30 is configured to be capable of loading a cartridge 10A.
  • the tape drive device 30 is configured to be capable of loading one cartridge 10A, but may be configured to be capable of loading multiple cartridges 10A simultaneously.
  • the tape drive device 30 includes a spindle 31, a take-up reel 32, a spindle drive device 33, a reel drive device 34, a plurality of guide rollers 35, a drive head 36, a reader/writer 37, and a control device 38.
  • the tape drive device 30 may further include a thermometer 39, a hygrometer 40, etc.
  • the spindle 31 has a head portion that engages with the chucking gear of the tape reel 13 through an opening 14 formed in the lower shell 11b of the cartridge 10A.
  • the spindle 31 lifts the tape reel 13 a predetermined distance against the biasing force of the reel spring 16, and releases the reel lock function of the reel lock member 17.
  • the tape reel 13 is rotatably supported inside the cartridge case 11 by the spindle 31.
  • the spindle drive unit 33 rotates the spindle 31 in response to commands from the control unit 38.
  • the take-up reel 32 is configured to be able to secure the tip (leader pin 220) of the magnetic tape T that is pulled out of the cartridge 10A via a tape loading mechanism (not shown).
  • the multiple guide rollers 35 guide the magnetic tape T so that the tape path formed between the cartridge 10A and the take-up reel 32 has a predetermined relative positional relationship with the drive head 36.
  • the reel drive unit 34 rotates the take-up reel 32 in response to commands from the control unit 38.
  • the spindle 31 and take-up reel 32 are rotated by the spindle drive device 33 and reel drive device 34, causing the magnetic tape T to run.
  • the magnetic tape T can run back and forth in the forward direction indicated by arrow A1 in FIG. 8 (the direction in which it unwinds from the tape reel 13 side to the take-up reel 32 side), and in the reverse direction indicated by arrow A2 (the direction in which it rewinds from the take-up reel 32 side to the tape reel 13 side).
  • the tension in the longitudinal direction (X-axis direction) of the magnetic tape T during data recording/playback can be adjusted by controlling the rotation of the spindle 31 by the spindle drive device 33 and the rotation of the take-up reel 32 by the reel drive device 34. Adjustment of the tension of the magnetic tape T may be performed by controlling the movement of the guide roller 35, a tension control unit including a dancer roller, etc., instead of (or in addition to) controlling the rotation of the spindle 31 and take-up reel 32.
  • the tape drive device 30 by configuring the tape drive device 30 to be tension adjustable, it is also possible to accommodate changes in the width dimension of the magnetic tape T caused by internal distortion of the magnetic tape T or changes over time. Specifically, if the width dimension of the magnetic tape T changes in the direction of widening, the tension is adjusted higher than the reference tension, and if the servo band pitch changes in the direction of narrowing, the tension is adjusted lower than the reference tension. Information regarding the reference tension when recording the servo pattern and the width dimension of the magnetic tape T at the reference tension is stored in the cartridge memory 211.
  • the reader/writer 37 is configured to be able to record management information in the cartridge memory 211 in response to a command from the control device 38.
  • the reader/writer 37 is also configured to be able to read management information from the cartridge memory 211 in response to a command from the control device 38.
  • the management information includes product information of the tape cartridge 10A and the magnetic tape T, usage history information, and an overview of the information recorded on the magnetic tape T.
  • the product information includes manufacturing information, the number of recording tracks 5 on the magnetic tape T, unique information such as an ID, etc.
  • the usage history information includes the access date and time, address information, communication history with the reader/writer 37, and the presence or absence of anomalies during loading/unloading into the tape drive device 30.
  • the ISO 14443 method is used as the communication method between the reader/writer 37 and the cartridge memory 211.
  • the control device 38 includes, for example, a control unit, a memory unit, a communication unit, etc.
  • the control unit is composed of, for example, a CPU (Central Processing Unit), etc., and performs overall control of each part of the tape drive device 30 according to a program stored in the memory unit.
  • CPU Central Processing Unit
  • the storage unit includes a non-volatile memory in which various data and programs are recorded, and a volatile memory used as a working area for the control unit.
  • the above-mentioned various programs may be read from a portable recording medium such as an optical disk or semiconductor memory, or may be downloaded from a server device on a network.
  • the storage unit temporarily or non-temporarily stores information from the cartridge memory 211 read from the reader/writer 37, the outputs of the thermometer 39 and the hygrometer 40, etc.
  • the communication unit is configured to be capable of communicating with other devices such as a PC (Personal Computer) and a server device.
  • the drive head 36 is configured to be capable of recording data onto the magnetic tape T in response to commands from the control device 38.
  • the drive head 36 is also configured to be capable of reproducing data written onto the magnetic tape T in response to commands from the control device 38.
  • the drive head 36 is composed of a head unit having, for example, two servo read heads, multiple data write/read heads, etc.
  • Figure 9 is a schematic diagram of the drive head 36 as seen from the bottom (tape running surface).
  • the drive head 36 includes a first drive head portion 36a and a second drive head portion 36b.
  • the first drive head portion 36a and the second drive head portion 36b are configured symmetrically in the X'-axis direction (the running direction of the magnetic tape MT (the X-axis direction in FIG. 4)).
  • the first drive head portion 36a and the second drive head portion 36b are configured to be movable in the Y'-axis direction (the width direction of the magnetic tape T (the Y-axis direction in FIG. 4)).
  • the first drive head unit 36a is a drive head used when the magnetic tape T is running in the forward direction (direction A1 in FIG. 8).
  • the second drive head unit 36b is a drive head used when the magnetic tape T is running in the reverse direction (direction A2 in FIG. 8).
  • the first drive head unit 36a and the second drive head unit 36b are basically of the same configuration, so the first drive head unit 36a will be described as a representative example.
  • the first drive head unit 36a has a head body 131, two servo read heads 132, and multiple data write/read heads 133.
  • the servo read head 132 is configured to be able to reproduce servo signals by reading the magnetic flux generated from the magnetic information recorded on the servo band s of the magnetic tape T using an MR element (MR: Magneto Resistive effect) or the like. In other words, the servo read head 132 reproduces the servo signal by reading the servo pattern 6 recorded on the servo band s.
  • MR Magneto Resistive effect
  • the servo read heads 132 are provided on both ends of the width direction (Y'-axis direction in FIG. 9) of the head body 131.
  • MR elements include anisotropic magnetoresistive effect elements (AMR: Anisotropic Magneto Resistive effect), giant magnetoresistive effect elements (GMR: Giant Magneto Resistive effect), tunnel magnetoresistive effect elements (TMR: Tunnel Magneto Resistive effect), etc.
  • the servo read head pitch P1 which is the distance in the width direction (Y'-axis direction) between the two servo read heads 132, is set to the center value (2858.8 ⁇ m) of the standard value of the distance (servo band pitch) between two adjacent servo bands s on the magnetic tape T.
  • the data write/read heads 133 are arranged at equal intervals along the width direction (Y'-axis direction).
  • the data write/read heads 133 are also arranged at a position sandwiched between two servo read heads 132.
  • the number of data write/read heads 133 is, for example, about 20 to 70, but this number is not particularly limited, and in this embodiment, there are 32 (32 channels).
  • the data write/read head 133 includes a data write head 134 and a data read head 135.
  • the data write head 134 is configured to be capable of recording a data signal on the data band d of the magnetic tape T by the magnetic field generated from the magnetic gap.
  • the data read head 135 is configured to be capable of reproducing the data signal by reading the magnetic field generated from the magnetic information recorded on the data band d of the magnetic tape T by an MR element or the like.
  • MR elements include an anisotropic magnetoresistance element (AMR), a giant magnetoresistance element (GMR), a tunnel magnetoresistance element (TMR), and the like.
  • the data write head 134 is positioned to the left of the data read head 135 (upstream when the magnetic tape T flows in the forward direction).
  • the data write head 134 is positioned to the right of the data read head 135 (upstream when the magnetic tape T flows in the reverse direction).
  • the data read head 135 is capable of reproducing a data signal immediately after the data write head 134 writes the data signal to the magnetic tape T.
  • the data signal written by the data write head 134 of the first drive head unit 36a may be reproduced by the data read head 135 of the second drive head unit 36b.
  • FIG. 10 is a diagram showing the state when the first drive head unit 36a is recording/playing back a data signal. Note that the example shown in FIG. 10 shows the state when the magnetic tape T is running in the forward direction (A1 direction).
  • one of the two servo read heads 132 is positioned on one of the two adjacent servo bands s and reads the servo pattern 6 on this servo band s.
  • the other of the two servo read heads 132 is positioned on the other of the two adjacent servo bands s and reads the servo pattern 6 on this servo band s.
  • the control device 38 determines whether the servo read head 132 is accurately tracing the desired servo trace line TL (see FIG. 6) based on the reproduced waveform of the servo pattern 6.
  • the first stripe group 61 and the second stripe group 62 in the servo pattern 6 are inclined in opposite directions with respect to the width direction (Y-axis direction). Therefore, on the upper servo trace line TL, the distance in the longitudinal direction (X-axis direction) between the first stripe group 61 and the second stripe group 62 is relatively narrow. On the other hand, on the lower servo trace line TL, the distance in the longitudinal direction (X-axis direction) between the first stripe group 61 and the second stripe group 62 is relatively wide.
  • the current position of the servo read head 132 in the width direction (Y-axis direction) with respect to the magnetic tape T can be found.
  • the control device 38 can therefore determine whether the servo read head 132 is accurately tracing the target servo trace line TL based on the reproduced waveform of the servo pattern 6. If the servo read head 132 is not accurately tracing the target servo trace line TL, the control device 38 moves the drive head 36 in the width direction (Y' axis direction) to adjust the position or tracking of the drive head 36. The method of measuring the servo trace line TL traced by the servo read head 132 will be described later.
  • the data write/read head 133 adjusts its position to align with the servo trace line TL and records a data signal in the recording track 5.
  • the magnetic tape T When the magnetic tape T has been completely pulled out of the tape cartridge 10A, the magnetic tape T now runs in the reverse direction (A2 direction).
  • the second drive head portion 36b is used as the drive head 36.
  • the servo trace line TL that is used is the servo trace line TL adjacent to the previous servo trace line TL.
  • a data signal is recorded by the data write head 134 of the second drive head portion 36b on the recording track 5 adjacent to the recording track 5 on which the data signal was previously recorded.
  • the magnetic tape T is made to travel back and forth many times, with the running direction changed between forward and reverse, while data signals are recorded on the recording tracks 5.
  • the first drive head unit 36a (or the second drive head unit 36b) contains 32 data write/read heads 133.
  • the servo pattern 6 has a data structure that complies with the "ECMA-319 standard."
  • Figure 11 (A) is a schematic plan view showing an example of the arrangement of the servo pattern 6, and
  • Figure 11 (B) is a diagram showing the reproduced waveform.
  • the servo pattern includes multiple azimuthal slope patterns of two or more different shapes.
  • the position of the servo read head 132 is recognized based on the time interval between reading two slope patterns of different shapes and the time interval between reading two slope patterns of the same shape. Based on the position of the servo read head 132 thus recognized, the position of the drive head 36 in the width direction (Y-axis direction) of the magnetic tape T is controlled (see Figures 9 and 10).
  • the servo pattern 6 forms a servo frame SF having a first servo subframe SSF1 and a second servo subframe SSF2.
  • the servo frames SF are arranged in the longitudinal direction of the magnetic tape T at predetermined intervals along the longitudinal direction of the tape.
  • Each servo frame SF encodes one bit, either "1" or "0.” In other words, one servo frame SF corresponds to one bit.
  • the first servo subframe SSF1 is composed of an A burst 6a and a B burst 6b.
  • the A burst 6a is composed of five straight line patterns (corresponding to the first stripe group 61 in FIG. 6) that are inclined in a first direction relative to the longitudinal direction of the tape
  • the B burst 6b is composed of five straight line patterns (corresponding to the second stripe group 62 in FIG. 6) that are inclined in a second direction opposite to the first direction relative to the longitudinal direction of the tape.
  • the second servo subframe SSF2 is composed of a C burst 6c and a D burst 6d.
  • the C burst 6c is composed of four straight line patterns inclined in the first direction (corresponding to the first stripe group 61 in FIG. 6)
  • the D burst 6d is composed of four straight line patterns inclined in the second direction (corresponding to the second stripe group 62 in FIG. 6).
  • the length of the servo frame SF and each servo subframe SSF1, SSF2, and the arrangement interval of the inclined portions that incline each burst 6a to 6d can be set arbitrarily according to the type and specifications of the magnetic tape, etc.
  • the reproduced waveform of the servo pattern 6 typically exhibits a burst waveform as shown in FIG. 11(B), where signal S6a corresponds to A burst 6a, signal S6b corresponds to B burst 6b, signal S6c corresponds to C burst 6c, and signal S6d corresponds to D burst 6d.
  • a position error signal is generated by reading servo patterns 6 on two servo bands adjacent to one data band, and the recording/playback head is appropriately positioned relative to the recording track in that data band.
  • the servo patterns 6 are read from a magnetic tape T running at a predetermined speed, and the ratio of the distance (time interval) AC between A burst 6a and C burst 6c, which are arrays of inclined patterns of the same shape, to the distance (time interval) AB between A burst 6a and B burst 6b, which are arrays of inclined patterns of different shapes (or the ratio of the distance CA between C burst 6c and A burst 6a to the distance CD between C burst 6c and D burst 6d) is calculated, and the drive head 36 is moved in the tape width direction (Y' axis direction) so that this value becomes a set value determined for each recording track (see Figure 10).
  • a different combination of servo band identification information is written for each data band in each servo band s (s0 to s4).
  • the combination of servo band identification information obtained from the two servo bands s2, s3 adjacent to data band d0 is different from the combination of servo band identification information obtained from the servo bands s1, s2 adjacent to data band d1, the combination of servo band identification information obtained from the servo bands s3, s4 adjacent to data band d2, and the combination of servo band identification information obtained from the two servo bands s0, s1 adjacent to data band d3.
  • the combination of servo band identification information obtained from the two servo bands adjacent to one data band different from the servo band identification information obtained from the two servo bands adjacent to another data band, it becomes possible to identify each individual data band.
  • servo band identification information is embedded in the servo bands.
  • the servo band identification information is multiple-bit information, typically 4 bits, but may be 8 bits or multiple bits other than 4 bits and 8 bits.
  • the two types of servo bands include a first servo band in which first servo band identification information is recorded, and a second servo band in which second servo band identification information is recorded.
  • the first servo band identification information is 4-bit information (e.g., "1001")
  • the second servo band identification information is 4-bit information (e.g., "0111") that is different from the first servo band identification information.
  • the combination of the codes "0" and “1" constituting the first and second servo band identification information is identified from the reproduced waveform of the servo pattern 6.
  • the reproduced waveform of the servo pattern 6 corresponds to a modulated wave of the codes "0" and "1”
  • the first and second servo band identification information is read out by demodulating the reproduced waveform and combining, for example, four bits.
  • the first and second servo band identification information will be described below with reference to Figures 12 and 13.
  • both the first servo pattern 601 and the second servo pattern 602 are composed of a combination of two types of servo frames SF including a servo frame SF1 representing one code (e.g., "1") and a servo frame SF0 representing the other code (e.g., "0").
  • Each servo frame SF1, SF0 is common in that it has a servo frame SF consisting of a first servo subframe SSF1 and a second servo subframe SSF2 as a constituent unit, but the first servo subframe SSF1 (A burst 6a and B burst 6b) is different from each other.
  • the five slope patterns constituting A burst 6a and B burst 6b are arranged such that the second and fourth slope portions are arranged in positions biased towards the third slope portion, respectively. Therefore, for the A burst 6a and the B burst 6b in the servo frame SF0, the distance between the second and third slopes, and between the third and fourth slopes, is the smallest, and the distance between the first and second slopes, and between the fourth and fifth slopes, is the largest.
  • Figures 13(A) and (B) show the reproduced waveforms SP1 and SP2 of the first servo pattern 601 and the second servo pattern 602, respectively.
  • the reproduced waveform of each servo frame SF1, SF0 is composed of a burst signal having a peak at a position corresponding to the slope of each of the burst portions 6a to 6d.
  • the configuration of the A burst 6a and the B burst 6b is different from that of the A burst 6a and the B burst 6b of servo frame SF1, so that the peak positions of the burst signals S6a and S6b are shifted corresponding to the intervals between the different slopes.
  • the servo frame S ⁇ BR>E1 shown in Figure 13(A) represents one bit "1”
  • the servo frame SF0 shown in Figure 13(B) represents another bit "0”.
  • the servo band pitch is an index indicating the distance between two servo bands (servo bands s2, s3) adjacent to one data band (for example, data band d0). More specifically, the servo band pitch refers to the distance between the center of the servo pattern recorded in one of the two servo bands and the center of the servo pattern recorded in the other servo band. In the following description, the servo band pitch may also be used to mean the difference from the servo read head pitch P1 (see FIG. 9).
  • the average value of the difference between two adjacent servo band pitches in multiple servo bands over the entire length of the magnetic tape T is 100 nm or less, preferably 95 nm or less, more preferably 90 nm or less, and even more preferably 85 nm or less.
  • the servo band pitch is measured by the tape drive device 30.
  • the drive head 36 tracks the data band d0 sandwiched between the servo band s2 and the servo band s3, as shown in Figure 14.
  • the method of measuring the servo band pitch using the tape drive device 30 involves running the magnetic tape T using the tape drive device 30, measuring the servo trace lines TL on each servo band of the two servo read heads 132, and measuring the servo band pitch from the relative position of each measured servo trace line TL with respect to the servo pattern 6.
  • the spacing between the servo trace lines TL shown by solid lines in FIG. 14 indicates the servo band pitch (servo read head pitch P1, which is the spacing between the two servo read heads 132 of the drive head 36) when the width of the magnetic tape T does not change. Also, the spacing between the servo trace lines TL shown by dashed lines in FIG. 14 corresponds to the servo band pitch (P2) when the width of the magnetic tape T increases.
  • FIG. 15 is a diagram explaining a method for measuring the servo trace line TL.
  • the tape drive device 30 outputs a servo playback signal having a waveform according to the position of the servo trace line TL relative to the servo pattern 6 (see FIG. 13).
  • the distance AC between A burst and C burst, which are arrays of inclination patterns of the same shape, and the distance AB between A burst and B burst, which are arrays of inclination patterns of different shapes are calculated, and the position of the servo trace line TL of each servo read head 132 is measured using the following formula [Equation 2].
  • ⁇ is the azimuth angle of each of the inclination patterns, which corresponds to the angle ⁇ in FIG. 6, and is set to 12° in this example.
  • distance AC may be distance AC1 between the first slope portions of the A burst and C burst, distance AC2 between their second slope portions, distance AC3 between their third slope portions, or distance AC4 between their fourth slope portions.
  • distances AC AC1 to AC4 refer to the distances between positions (upper peak positions) that indicate the maximum positive amplitude in the servo playback waveform.
  • the distance AB may be the distance AB1 between the first inclined portions of the A burst and the B burst, the distance AB2 between their second inclined portions, the distance AB3 between their third inclined portions, or the distance AB4 between their fourth inclined portions.
  • distance AB1 when distance AC1 is adopted, distance AB1 is adopted, when distance AC2 is adopted, distance AB2 is adopted, when distance AC3 is adopted, distance AB3 is adopted, and when distance AC4 is adopted, distance AB4 is adopted.
  • the servo band pitch is calculated from the difference in the values representing the position of each servo trace line TL on the servo pattern, which is calculated from the ratio of distance AB and distance AC, calculated using the above formula [2].
  • the difference is taken between the measurement value of the servo band on the tape edge side (servo band s3) and the measurement value of the servo band on the tape center side (servo band s2).
  • the positive or negative value indicates the direction of change in the tape width, with a positive value corresponding to a narrowing of the servo band pitch and a negative value corresponding to a widening of the servo band pitch. If the difference is zero, it means that there is no change in the tape width.
  • the servo band pitch is preferably determined from the difference between many servo frames, and may be, for example, the average of measured values calculated from the difference between 100 and 100,000 servo frames.
  • the tape tension during measurement is the tension during recording of the servo pattern 6 (reference tension, for example, 0.55 N), and the measurement is performed at a constant tension over the entire length of the magnetic tape T.
  • the method of measuring the servo trace line TL is not limited to the above example.
  • the distance CA between the C burst and the A burst and the distance CD between the C burst and the D burst may be calculated, and the position of the servo trace line TL may be measured using the following formula [Equation 3].
  • the distance CA may be the distance CA1 between the first inclined portions of the C burst and the A burst, the distance CA2 between their second inclined portions, the distance CA3 between their third inclined portions, or the distance CA4 between their fourth inclined portions.
  • These distances CA (CA1 to CA4) refer to the distances between the positions that indicate the maximum positive amplitude values in the servo playback waveform.
  • the distance CD may be the distance CD1 between the first inclined portions of the C burst and the D burst, the distance CD2 between their second inclined portions, the distance CD3 between their third inclined portions, or the distance CD4 between their fourth inclined portions.
  • distance CD1 when distance CA1 is adopted, distance CD1 is adopted, when distance CA2 is adopted, distance CD2 is adopted, when distance CA3 is adopted, distance CD3 is adopted, and when distance CA4 is adopted, distance CD4 is adopted.
  • the servo band pitch may be measured by using the average value of the measurement value using the formula [2] and the measurement value using the formula [3].
  • the distance between the positions (lower peak positions) showing the maximum negative value of the amplitude in the servo reproduction waveform may be used as the distances AC and AB in the formula [2] and the distances CA and CD in the formula [3].
  • the average value of the distance between the positions (upper peak positions) showing the maximum positive value of the amplitude in the servo reproduction waveform and the distance between the positions (lower peak positions) showing the maximum negative value may be used as the distances AC and AB in the formula [2] and the distances CA and CD in the formula [3].
  • the distance AB is 38.5 ⁇ m and the distance AC is 76 ⁇ m in the servo band s2, and the distance AB is 37.5 ⁇ m and the distance AC is 76 ⁇ m in the servo band s3.
  • the servo band pitch P2 in this case is determined to be a value 2.3523 ⁇ m wider than the servo read head pitch P1.
  • the distance AB is 38 ⁇ m and the distance AC is 76 ⁇ m for both servo band s2 and servo band s3.
  • the distances are 89.3880 [ ⁇ m] for both servo band s2 and servo band s3, and the difference between them is 0 [ ⁇ m].
  • the servo band pitch in this case is the same as the servo read head pitch P1.
  • the longitudinal direction (Y'-axis direction) of the drive head 36 may be arranged to be inclined at a predetermined angle ⁇ (azimuth angle ⁇ ) with respect to the width direction (Y-axis direction) of the magnetic tape T.
  • the azimuth angle ⁇ of the drive head 36 is adjusted to accommodate variations in the width of the magnetic tape T.
  • the azimuth angle ⁇ of the drive head 36 is made smaller, and conversely, when the width of the magnetic tape T becomes relatively narrower, the azimuth angle ⁇ of the drive head 36 is made larger.
  • the control device 38 acquires information on the width of the magnetic tape T from a width measurement unit (not shown) (or predicts the width of the magnetic tape T from the servo signal), and adjusts the azimuth angle ⁇ of the drive head 36 by an angle adjustment unit (not shown) based on the information on the width of the magnetic tape T.
  • FIG. 16 is a schematic front view showing a servo pattern recording device 100 according to an embodiment of the present technology.
  • FIG. 17 is a partially enlarged view showing a part of the servo pattern recording device 100.
  • the servo pattern recording device 100 comprises, in order from the upstream side in the transport direction of the magnetic tape T, a feed roller 111, a pre-processing unit 112, a servo write head 113, a reproducing head unit 114, and a take-up roller 115.
  • the servo pattern recording device 100 further comprises a drive unit 120 and a controller 130.
  • the controller 130 has a control unit that comprehensively controls each unit of the servo pattern recording device 100, a memory unit that stores various programs and data required for processing by the control unit, a display unit that displays data, an input unit for inputting data, etc.
  • the feed roller 111 is capable of rotatably supporting a roll of magnetic tape T (before the servo pattern 6 is recorded).
  • the feed roller 111 is rotated in response to the drive of a driving source such as a motor, and feeds out the magnetic tape T downstream in response to the rotation.
  • the winding roller 115 is capable of rotatably supporting the rolled magnetic tape T (after the servo pattern 6 is recorded).
  • the winding roller 115 rotates in synchronization with the delivery roller 111 in response to the drive of a driving source such as a motor, and winds up the magnetic tape T on which the servo pattern 6 is recorded in response to the rotation.
  • the delivery roller 111 and the winding roller 115 are capable of moving the magnetic tape T at a constant speed on the transport path.
  • the servo write head 113 is arranged, for example, on the upper side (magnetic layer 13 side) of the magnetic tape T.
  • the servo write head 113 may also be arranged on the lower side (base layer 11 side) of the magnetic tape T.
  • the servo write head 113 generates a magnetic field at a predetermined timing in response to a square wave pulse signal, and applies the magnetic field to a part of the magnetic layer 13 (after pre-processing) of the magnetic tape T.
  • the servo write head 113 magnetizes a portion of the magnetic layer 13 in a first direction to record a servo pattern 6 on the magnetic layer 13 (see the black arrows in FIG. 17 for the magnetization direction).
  • the servo write head 113 is capable of recording the servo pattern 6 on each of the five servo bands s0 to s4 when the magnetic layer 13 passes below the servo write head 113.
  • the first direction which is the magnetization direction of the servo pattern 6, includes a vertical component perpendicular to the top surface of the magnetic layer 13. That is, in this embodiment, because the magnetic layer 13 contains vertically oriented or non-oriented magnetic powder, the servo pattern 6 recorded in the magnetic layer 13 includes a vertical magnetization component.
  • the pre-processing unit 112 is disposed, for example, upstream of the servo write head 113, below the magnetic tape T (on the base layer 11 side).
  • the pre-processing unit 112 may also be disposed above the magnetic tape T (on the magnetic layer 13 side).
  • the pre-processing unit 112 includes a permanent magnet 112a that can rotate around the Y'-axis direction (width direction of the magnetic tape T) in FIG. 13 as the central axis of rotation.
  • the shape of the permanent magnet 112a is, for example, a cylindrical shape or a polygonal prism shape, but is not limited to these.
  • the permanent magnet 112a Before the servo pattern 6 is recorded by the servo write head 113, the permanent magnet 112a applies a magnetic field to the entire magnetic layer 13 using a DC magnetic field, thereby demagnetizing the entire magnetic layer 13. This allows the permanent magnet 112a to magnetize the magnetic layer 13 in advance in a second direction opposite to the magnetization direction of the servo pattern 6 (see the white arrow in Figure 17). In this way, by making the two magnetization directions opposite each other, the reproduced waveform of the servo signal obtained by reading the servo pattern 6 can be made symmetrical in the up and down directions ( ⁇ ).
  • the rotation angle of the permanent magnet 112a may be set arbitrarily, the entire magnetic layer 13 may be demagnetized, and then the servo pattern 6 may be recorded on the magnetic layer 13, and the rotation angle of the permanent magnet 112a centered on the width direction of the magnetic tape T may be adjusted based on the inclination of the reproduced waveform.
  • the reproducing head unit 114 is disposed on the upper side (magnetic layer 13 side) of the magnetic tape T, downstream of the servo write head 113.
  • the reproducing head unit 114 reads the servo pattern 6 from the magnetic layer 13 of the magnetic tape T, which has been preprocessed by the preprocessing unit 112 and on which the servo pattern 6 has been recorded by the servo write head 113.
  • the reproduced waveform of the servo pattern 6 read by the reproducing head unit 114 is displayed on the screen of the display unit.
  • the reproducing head unit 114 detects magnetic flux generated from the surface of the servo band s when the magnetic layer 13 passes under the reproducing head unit 114. The magnetic flux detected at this time becomes the reproduced waveform of the servo pattern 6 as a servo signal.
  • the present technology also provides a magnetic recording cartridge (also called 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 may include, for example, a communication unit that communicates with a recording and playback device, a storage unit, and a control unit that stores information received from the recording and playback device via the communication unit in the storage unit, and reads information from the storage unit and transmits it to the recording and playback device via the communication unit in response to a request from the recording and playback device.
  • the information may include adjustment information for adjusting the tension applied to the magnetic recording medium in the longitudinal direction.
  • the magnetic recording cartridge 10A is a magnetic recording cartridge that conforms to the LTO (Linear Tape-Open) standard, and is equipped with a reel 10C on which a magnetic tape (tape-like magnetic recording medium) T is wound inside a cartridge case 10B consisting of a lower shell 212A and an upper shell 212B, a reel lock 214 and a reel spring 215 for locking the rotation of the reel 10C, a spider 216 for unlocking the reel 10C, a sliding door 217 that straddles the lower shell 212A and the upper shell 212B and opens and closes a tape outlet 212C provided in the cartridge case 10B, a door spring 218 that biases the sliding door 217 to a closed position of the tape outlet 212C, a write protect 219 for preventing accidental erasure, and a cartridge memory 211.
  • LTO Linear Tape-Open
  • the reel 10C is generally disk-shaped with an opening in the center, and is composed of a reel hub 213A and a flange 213B made of a hard material such as plastic.
  • a leader tape LT is connected to one end of the magnetic tape T.
  • a leader pin 220 is provided at the tip of the leader tape LT.
  • the cartridge memory 211 is provided near one corner of the magnetic recording cartridge 10A.
  • the cartridge memory 211 faces a reader/writer (not shown) of the recording and reproducing device 80.
  • the cartridge memory 211 communicates with the recording and reproducing device 30, specifically the reader/writer (not shown), using a wireless communication standard that complies with the LTO standard.
  • the magnetic tape cartridge is described as a one-reel type cartridge, but the magnetic recording cartridge of the present technology may be a two-reel type cartridge.
  • the magnetic recording cartridge of the present technology may have one or more (e.g., two) reels on which the magnetic tape is wound.
  • an example of a magnetic recording cartridge of the present technology having two reels will be described with reference to Figure 19.
  • FIG 19 is an exploded perspective view showing an example of the configuration of a two-reel type cartridge 421.
  • the cartridge 421 includes an upper half 402 made of synthetic resin, a transparent window member 423 that fits into and is fixed to a window portion 402a opened on the upper surface of the upper half 402, a reel holder 422 that is fixed to the inside of the upper half 402 and prevents the reels 406 and 407 from floating up, a lower half 405 that corresponds to the upper half 402, the reels 406 and 407 that are stored in the space formed by combining the upper half 402 and the lower half 405, the magnetic tape MT1 wound on the reels 406 and 407, a front lid 409 that closes the front opening formed by combining the upper half 402 and the lower half 405, and a back lid 409A that protects the magnetic tape MT1 exposed at this front opening.
  • the reel 406 comprises a lower flange 406b having a cylindrical hub portion 406a in the center around which the magnetic tape MT1 is wound, an upper flange 406c having approximately the same size as the lower flange 406b, and a reel plate 411 sandwiched between the hub portion 406a and the upper flange 406c.
  • the reel 407 has a similar configuration to the reel 406.
  • the window member 423 has mounting holes 423a at positions corresponding to the reels 406 and 407 for attaching reel holders 422, which are reel holding means for preventing the reels from floating up.
  • the magnetic tape MT1 is the same as the magnetic tape T in the first embodiment.
  • the present technology can also adopt the following configuration.
  • the magnetic layer includes a magnetic layer, an underlayer, and a base layer, in that order.
  • the undercoat layer comprises a chlorine-containing binder;
  • the thickness of a portion of the underlayer where the chlorine count is equal to or greater than the following threshold value is 130 nm or less, and the average width change of the magnetic recording medium before and after being left for 40 hours in an environment of a temperature of 50° C. and a relative humidity of 40% RH with a tension of 0.55 N applied in the longitudinal direction is 170 ppm or less.
  • [Threshold] [average chlorine count in the undercoat layer] + 6 ⁇ [standard deviation obtained when calculating the average chlorine count]
  • the magnetic recording medium includes a magnetic layer, an underlayer, and a base layer, in that order.
  • the undercoat layer comprises a chlorine-containing binder; the thickness of a portion of the underlayer where the chlorine count is equal to or greater than the threshold value is 12% or less of the thickness of the underlayer, and the average width change of the magnetic recording medium before and after being left for 40 hours in an environment of a temperature of 50° C. and a relative humidity of 40% RH with a tension of 0.55 N applied in the longitudinal direction is 170 ppm or less.
  • [Threshold] [average chlorine count in the undercoat layer] + 6 ⁇ [standard deviation obtained when calculating the average chlorine count]
  • [12] The magnetic recording medium according to any one of [1] to [11], wherein the average width change is 140 ppm or less.
  • the polyesters include at least one selected from the group consisting of polyethylene terephthalate and polyethylene naphthalate.
  • the average thickness of the base layer is 4.4 ⁇ m or less.
  • the magnetic layer-forming paint was prepared as follows. First, the first composition having the following composition was mixed with an extruder. Next, the mixed first composition and a solvent were placed in a stirring tank equipped with a disperser and premixed. Next, the second composition and the third composition having the following composition were added and mixed with a dyno mill, followed by filtering to prepare the magnetic layer-forming paint.
  • Carbon black 2.0 parts by mass (manufactured by Tokai Carbon Co., Ltd., product name: Seast S, arithmetic mean particle size 70 nm)
  • Cyclohexanone 18.5 parts by weight Mixed in a paint shaker for 10 hours
  • the fourth composition having the above composition was kneaded with an extruder.
  • the kneaded fourth composition and the fifth composition having the following composition were added to a stirring tank equipped with a disperser and premixed.
  • mixing was further performed using a bead mill ECM-PRO (Shinmaru Enterprises Co., Ltd.) at a circulation flow rate of 500 L/h to 2000 L/h for a processing time in the bead mill of 30 to 150 minutes, followed by filtering to prepare a coating material for forming an undercoat layer.
  • Carbon black 30 parts by mass (average particle size 20 nm)
  • Polyurethane resin (resin solution: polyurethane resin content 30% by mass, cyclohexanone content 70% by mass): 50 parts by mass n-Butyl stearate: 2.0 parts by mass Methyl ethyl ketone: 150.0 parts by mass Toluene: 150.0 parts by mass Cyclohexanone: 125.0 parts by mass
  • the coating material for forming the back layer was prepared as follows: The following raw materials were mixed in a stirring tank equipped with a disperser, and the mixture was filtered to prepare the coating material for forming the back layer.
  • Carbon black manufactured by Asahi Carbon Co., Ltd., product name: #80
  • Polyester polyurethane 150 parts by mass
  • refsin solution polyurethane resin blend amount 30% by mass, cyclohexanone blend amount 70% by mass
  • Methyl ethyl ketone 500 parts by weight
  • Toluene 300 parts by weight
  • Cyclohexanone 160 parts by weight
  • Polyisocyanate product name: Coronate L, manufactured by Tosoh Corporation
  • a reinforced PET film (base film) having an elongated shape, an average thickness of 4.00 ⁇ m, an average longitudinal storage modulus of 3.9 GPa at a temperature of 50 ° C., and an average longitudinal Young's modulus of 4.6 GPa was prepared as a support for the base layer of the magnetic tape.
  • the paint for forming the base layer, the paint for forming the magnetic layer, and the paint for forming the back layer were applied to one main surface of the reinforced PET film in this order to the finished thickness shown in Table 1, and then dried.
  • the reinforced PET film on which the base layer, the magnetic layer, and the back layer were formed was subjected to a curing treatment.
  • a calendar treatment was performed, and after the calendar treatment, a strain relaxation treatment was performed at 65 ° C. for 48 hours. The surface of the magnetic layer was smoothed.
  • the magnetic tape obtained as described above was cut into a width of 1/2 inch (12.65 mm), thereby obtaining a long magnetic tape.
  • the 1/2 inch wide magnetic tape was wound around a reel provided inside a cartridge case to obtain a multi-wrap magnetic recording cartridge.
  • a servo signal was recorded on the magnetic tape by a servo track writer.
  • the servo signal consisted of a series of V-shaped magnetic patterns, and the magnetic patterns were pre-recorded in two or more series parallel to the longitudinal direction at known intervals (hereinafter referred to as "the known intervals of the pre-recorded magnetic patterns").
  • the magnetic recording cartridge was measured for various values related to chlorine distribution, such as the chlorine count in the underlayer and the thickness of the portion where the chlorine count is equal to or greater than the threshold value.
  • Table 1 the average chlorine count C ave in the underlayer was 1.100.
  • the standard deviation ⁇ was 0.040. Therefore, the threshold value (C ave +6 ⁇ ) was 1.340.
  • the thickness of the portion of the underlayer that was equal to or greater than the threshold was 85 nm.
  • the portion that was equal to or greater than the threshold was in contact with the interface between the underlayer and the base layer, that is, was within 200 nm of the interface.
  • the ratio of the "thickness of the portion equal to or greater than the threshold value" to the "thickness of the underlayer” was 7.6%.
  • the peak chlorine count in the magnetic layer (maximum chlorine count in the magnetic layer) C mp was 6.506, and "peak chlorine count in the magnetic layer C mp "/"average chlorine count in the underlayer C ave " was 5.91.
  • Example 2 The same magnetic layer forming paint, undercoat layer forming paint and back layer forming paint as in Example 1 were used. The thicknesses of the magnetic layer and undercoat layer were reduced, and the drying temperature after the magnetic layer was applied was higher than in Example 1, thereby accelerating the volatilization rate of the solvent from the magnetic layer surface, and the binder that had once moved to the base layer side was moved to the magnetic layer surface side together with the volatilized solvent, reducing the amount of binder remaining on the base layer side.
  • a PEN film having an average thickness of 4.0 ⁇ m, an average longitudinal storage modulus of 5.5 GPa in an environment at a temperature of 50° C., and an average longitudinal Young's modulus of 6.3 GPa was used as the base layer, and a calendering process was performed, followed by a strain relaxation process at 70° C. for 48 hours.
  • a magnetic tape was obtained by the same method as in Example 1.
  • a magnetic recording cartridge containing the magnetic tape was obtained in the same manner as in Example 1.
  • various values relating to the chlorine distribution and the average width change were measured in the same manner as in Example 1. The measurement results are shown in Table 1, as in Example 1.
  • Example 1 In preparing the coating material for forming the undercoat layer, the processing time in the bead mill was shortened to 0.9 times that of Example 1, the amount of binder adsorbed was reduced by slightly worsening the dispersion, the amount of binder that migrated to the interface between the undercoat layer and the base layer due to the solvent that seeped in when the coating material for forming the magnetic layer was applied was increased, and the time for the strain relaxation treatment was set to 24 hours, but other than that, a magnetic tape was obtained in the same manner as in Example 1. Also, a magnetic recording cartridge containing the magnetic tape was obtained in the same manner as in Example 1. For the magnetic recording cartridge, various values relating to the chlorine distribution and the average width change were measured in the same manner as in Example 1. The measurement results are shown in Table 1, as in Example 1.
  • a magnetic tape was obtained in the same manner as in Example 2, except that the temperature of the strain relaxation treatment after the calendar treatment was 60° C. Further, in the same manner as in Example 1, a magnetic recording cartridge containing the magnetic tape was obtained. For the magnetic recording cartridge, various values relating to the chlorine distribution and the average width change were measured in the same manner as in Example 1. The measurement results are shown in Table 1, as in Example 1.
  • the processing time in the bead mill was shortened to 0.8 times that of Example 1, and the amount of binder adsorbed was reduced by slightly worsening the dispersion, thereby increasing the amount of binder that moves to the interface between the lower layer and the base by the solvent that seeps in when the coating material for forming the magnetic layer is applied, and a PEN film having an average thickness of 4.0 ⁇ m, an average longitudinal storage modulus of 5.5 GPa in an environment at a temperature of 50° C., and an average longitudinal Young's modulus of 6.3 GPa was used as the base layer, and a magnetic tape was obtained in the same manner as in Example 1, except that no strain relaxation treatment was performed.
  • Example 1 a magnetic recording cartridge containing the magnetic tape was obtained.
  • various values relating to the chlorine distribution and the average width change were measured in the same manner as in Example 1. The measurement results are shown in Table 1, as in Example 1.
  • a magnetic tape was obtained in the same manner as in Example 1, except that the same undercoat layer forming paint as in Comparative Example 1 was used, the thicknesses of the magnetic layer and undercoat layer were reduced, a reinforced PET film with an average thickness of 4.0 ⁇ m, an average longitudinal storage modulus of 3.9 GPa in an environment at a temperature of 50° C., and an average longitudinal Young's modulus of 4.6 GPa was used as the base layer, the average thickness of the magnetic layer after calendaring was set to 0.08 ⁇ m, the average thickness of the undercoat layer after calendaring was set to 0.8 ⁇ m, and a strain relaxation treatment was performed at 55° C. for 24 hours. Also, a magnetic recording cartridge containing the magnetic tape was obtained in the same manner as in Example 1. For the magnetic recording cartridge, various values relating to the chlorine distribution and the average width change were measured in the same manner as in Example 1. The measurement results are shown in Table 1, as in Example 1.
  • a magnetic tape was obtained in the same manner as in Example 1, except that the same undercoat layer forming paint as in Comparative Example 1 was used, the drying temperature after application of the undercoat layer forming paint was lower than that in Comparative Example 1, and a PET film having an average thickness of 4.0 ⁇ m, an average longitudinal storage modulus of 3.9 GPa in an environment at a temperature of 50° C., and an average longitudinal Young's modulus of 4.7 GPa was used as the base layer. Also, a magnetic recording cartridge containing the magnetic tape was obtained in the same manner as in Example 1. For the magnetic recording cartridge, various values relating to the chlorine distribution and the average width change were measured in the same manner as in Example 1. The measurement results are shown in Table 1, as in Example 1.
  • a magnetic tape was obtained in the same manner as in Example 2, except that a PET film was used that had an average thickness of 4.0 ⁇ m, an average longitudinal storage modulus of 3.9 GPa in an environment at a temperature of 50° C., and an average longitudinal Young's modulus of 4.7 GPa. Also, in the same manner as in Example 1, a magnetic recording cartridge containing the magnetic tape was obtained. For the magnetic recording cartridge, various values relating to the chlorine distribution and the average width change were measured in the same manner as in Example 1. The measurement results are shown in Table 1, as in Example 1.
  • the reliability of the magnetic tape contained in each of the magnetic recording cartridges manufactured in Examples 1 to 4 and Comparative Examples 1 to 4 was evaluated. The evaluation was performed as follows.
  • the magnetic recording cartridges of Examples 1 to 4 and Comparative Examples 1 to 4 were inserted into the LTO8 drive immediately after the cleaning tape had been run, and one round trip recording process was performed after the insertion. This operation was performed on the magnetic recording cartridges of Examples 1 to 4 and Comparative Examples 1 to 4, each having a large number of turns.
  • the above-mentioned recording process was carried out successively on 25 magnetic recording cartridges (25 round trips).
  • the reliability was judged to be "good.” If rewrites occurred twice at any point before the recording process for 25 volumes was completed, the reliability was determined to be “bad.” In addition, the number of volumes in which rewrites occurred twice was also recorded.
  • Table 1 The evaluation results for each magnetic tape are shown in Table 1 below.
  • the servo band pitch difference was measured using the measurement method described in 2. (5) above.
  • the width change over an estimated 10 years and the movement angle of the drive head placed at an angle were calculated. These calculation methods are described below.
  • the width change after 1 hour and 40 hours from the start of width measurement were measured for three samples obtained from the magnetic tape.
  • the width change after 1 hour for the three samples was arithmetically averaged to obtain the average width change after 1 hour from the start of measurement.
  • the width change after 40 hours for the three samples was arithmetically averaged to obtain the average width change after 40 hours from the start of measurement.
  • the time axis X is logarithmic, and the width change after 10 years was estimated by extrapolating the average width change after 1 hour from the start of measurement (initial value 0) and the average width change after 40 hours.
  • FIG. 20 is a schematic diagram for explaining a method for calculating the movement angle of the tilted drive head, which is the movement angle of the drive head required to deal with an assumed width change over 10 years.
  • the left side of Fig. 20 shows the distance (h) between the two servo read heads of the drive head, the servo band pitch (SP), and the tilt angle (10°) of the drive head for the initial (before width change) magnetic tape.
  • Cos10° SP/h.
  • the right side of Figure 20 shows the servo band pitch (SP- ⁇ SP), the drive head movement angle ( ⁇ ), and the tilt angle (10°+ ⁇ ) after the drive head moves on the magnetic tape after the servo band pitch has narrowed (after the width has changed).
  • Table 1 show that reliability during running is improved by making the thickness of the portion of the underlayer where the chlorine count is equal to or greater than the threshold smaller.
  • the results shown in the same table suggest that reliability during running of the magnetic tape is improved by making the thickness of the portion where the chlorine count is equal to or greater than the threshold, for example, 130 nm or less, 125 nm or less, or 123 nm or less, and more preferably 120 nm or less, 110 nm or less, 100 nm or less, or 90 nm or less.
  • Table 1 also show that reliability during running is improved by having a smaller proportion of the thickness of the underlayer where the chlorine count is equal to or greater than the threshold value.
  • the results shown in the same table suggest that reliability during running of the magnetic tape is improved by having the proportion of the thickness of the portion where the chlorine count is equal to or greater than the threshold value of, for example, 12% or less, 11.5% or less, or 11% or less, and more preferably 10% or less, 9.5% or less, or 9% or less.
  • the peak chlorine count C mp in the magnetic layer is preferably, for example, 6.4 or more, or 6.5 or more.
  • the ratio "peak chlorine count C mp in the magnetic layer"/"average chlorine count C ave in the underlayer” is preferably, for example, 5.5 or more, or 5.7 or more.
  • the average width change ⁇ A is 170 ppm or less, so the absolute value of the width change over 10 years is 500 ppm or less. Therefore, the movement angle of the tilted drive head can be kept to 0.15° or less, and it is believed that the expected width change after 10 years can be accommodated by adjusting the angle of the drive head.
  • the configurations, methods, steps, shapes, materials, and values given in the above-mentioned embodiments and examples are merely examples, and different configurations, methods, steps, shapes, materials, and values may be used as necessary.
  • the chemical formulas of compounds, etc. are representative, and are not limited to the valences, etc. given as long as they are general names of the same compounds.
  • a numerical range indicated using “ ⁇ ” indicates a range that includes the numerical values before and after " ⁇ " as the minimum and maximum values, respectively.
  • the upper or lower limit of a numerical range of a certain stage may be replaced with the upper or lower limit of a numerical range of another stage.
  • the materials exemplified in this specification may be used alone or in combination of two or more types.

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PCT/JP2024/005181 2023-03-02 2024-02-15 磁気記録媒体 Ceased WO2024181140A1 (ja)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000090431A (ja) * 1998-09-10 2000-03-31 Fuji Photo Film Co Ltd 磁気テープ及びその製造方法
JP2000155935A (ja) * 1998-11-20 2000-06-06 Sony Corp 磁気記録媒体
JP2001273623A (ja) * 2000-01-18 2001-10-05 Toray Ind Inc 磁気記録媒体
JP2007265547A (ja) * 2006-03-29 2007-10-11 Fujifilm Corp 磁気記録媒体
WO2022211020A1 (ja) * 2021-03-31 2022-10-06 ソニーグループ株式会社 磁気記録媒体およびカートリッジ

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000090431A (ja) * 1998-09-10 2000-03-31 Fuji Photo Film Co Ltd 磁気テープ及びその製造方法
JP2000155935A (ja) * 1998-11-20 2000-06-06 Sony Corp 磁気記録媒体
JP2001273623A (ja) * 2000-01-18 2001-10-05 Toray Ind Inc 磁気記録媒体
JP2007265547A (ja) * 2006-03-29 2007-10-11 Fujifilm Corp 磁気記録媒体
WO2022211020A1 (ja) * 2021-03-31 2022-10-06 ソニーグループ株式会社 磁気記録媒体およびカートリッジ

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