WO2024162173A1 - 磁気記録媒体およびカートリッジ - Google Patents

磁気記録媒体およびカートリッジ Download PDF

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Publication number
WO2024162173A1
WO2024162173A1 PCT/JP2024/002222 JP2024002222W WO2024162173A1 WO 2024162173 A1 WO2024162173 A1 WO 2024162173A1 JP 2024002222 W JP2024002222 W JP 2024002222W WO 2024162173 A1 WO2024162173 A1 WO 2024162173A1
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WO
WIPO (PCT)
Prior art keywords
magnetic
less
recording medium
magnetic tape
magnetic recording
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/JP2024/002222
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English (en)
French (fr)
Japanese (ja)
Inventor
大貴 川口
潤 寺川
嵩 潟口
美穂 森脇
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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 JP2024574838A priority Critical patent/JPWO2024162173A1/ja
Publication of WO2024162173A1 publication Critical patent/WO2024162173A1/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
    • G11B5/48—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
    • G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
    • G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
    • G11B5/714—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the dimension of the magnetic particles
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/73—Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/74—Record carriers characterised by the form, e.g. sheet shaped to wrap around a drum
    • G11B5/78—Tape carriers
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/84—Processes or apparatus specially adapted for manufacturing record carriers

Definitions

  • This disclosure relates to a magnetic recording medium and a cartridge equipped with the same.
  • Patent Document 1 describes that a good SNR (signal-to-noise ratio) can be achieved by including ferromagnetic hexagonal ferrite powder with a crystallite volume in the range of 1000 to 2400 nm3 in the magnetic layer.
  • the electromagnetic conversion characteristics may deteriorate.
  • the particle volume of the magnetic powder is 1,300 nm3 or less, the magnetic powder tends to contain a large number of extremely small magnetic particles, and deterioration of the electromagnetic conversion characteristics is particularly likely to occur.
  • An object of the present disclosure is to provide a magnetic recording medium and a cartridge including the same that can improve the electromagnetic conversion characteristics even when the particle volume of the magnetic powder is 1300 nm3 or less.
  • the magnetic recording medium comprises: A tape-shaped magnetic recording medium, A substrate; A magnetic layer containing magnetic powder, The particle volume of the magnetic powder determined by X-ray diffraction is 1,300 nm3 or less; The ratio Hc/Hr of the coercive force Hc of the magnetic layer in the perpendicular direction of the magnetic recording medium to the residual coercive force Hr of the magnetic layer measured by applying a pulse magnetic field in the perpendicular direction of the magnetic recording medium is 0.45 or less.
  • the cartridge according to the present disclosure includes the magnetic recording medium according to the present disclosure.
  • FIG. 1 is an exploded perspective view illustrating an example of a configuration of a cartridge according to an embodiment of the present disclosure.
  • FIG. 2 is a block diagram showing an example of the configuration of the cartridge memory.
  • FIG. 3 is a cross-sectional view showing an example of the structure of a magnetic tape.
  • FIG. 4 is a schematic diagram showing an example of a layout of a data band and a servo band.
  • FIG. 5 is an enlarged view showing an example of the configuration of a data band.
  • FIG. 6 is an enlarged view showing an example of the configuration of a servo band.
  • FIG. 7 is a schematic diagram of an apparatus used for peeling off the magnetic layer.
  • 8A and 8B are graphs that typically show the relationship between the particle size distribution of magnetic powder and the magnetic properties measured by VSM.
  • FIGS. 9A and 9B are graphs that typically show the relationship between the particle size distribution of magnetic powder and the magnetic properties measured by a pulsed magnetic field VSM.
  • FIG. 10 is a graph for explaining a method for measuring the remanence Hr of the magnetic layer.
  • FIG. 11 is an exploded perspective view showing an example of a configuration of a cartridge according to a modified example of an embodiment of the present disclosure.
  • FIG. 12 is a graph showing the relationship between the particle volume of the magnetic powder and the ratio Hc/Hr.
  • the measurements are performed in an environment of 25°C ⁇ 2°C and 50% RH ⁇ 5% RH.
  • the particle size distribution of the magnetic powder can also be a factor in improving the electromagnetic conversion characteristics. If the particle size distribution of the magnetic powder is wide, the magnetic powder will contain a large number of magnetic particles that deviate significantly from the average particle size. Of the magnetic particles that deviate significantly from the average particle size, extremely small magnetic particles do not contribute to the electromagnetic conversion characteristics and tend to behave as non-magnetic materials. On the other hand, among the magnetic particles that deviate significantly from the average particle size, coarse magnetic particles can cause noise in the playback signal.
  • a method for determining the particle size of magnetic powder using an observation image by STEM is conventionally known.
  • STEM Sccanning Transmission Electron Microscope
  • the measurement results of the particle size of the magnetic powder are likely to vary when using the particle size measurement method by STEM, making it difficult to quantify the particle size of the magnetic powder. Therefore, it is difficult to evaluate the sharpness of the particle size distribution of the magnetic powder using the particle size measurement results by STEM.
  • the present inventors conducted extensive research into a technique capable of evaluating the sharpness of the particle size distribution of magnetic powder even when the particle volume of the magnetic powder is 1300 nm3 or less. As a result, they discovered that the sharpness of the particle size distribution of magnetic powder can be evaluated by the ratio Hc/Hr of the coercive force Hc of the magnetic layer in the perpendicular direction of the magnetic recording medium to the remanent coercive force Hr of the magnetic layer measured by applying a pulse magnetic field in the perpendicular direction of the magnetic recording medium.
  • the present disclosure has been discovered as a result of the above investigation.
  • FIG. 1 is an exploded perspective view showing an example of the configuration of a cartridge 10 according to an embodiment.
  • the cartridge 10 is a one-reel type cartridge, and includes a cartridge case 12 consisting of a lower shell 12A and an upper shell 12B, a reel 13 around which a tape-like magnetic recording medium (hereinafter referred to as "magnetic tape") MT is wound, a reel lock 14 and a reel spring 15 for locking the rotation of the reel 13, a spider 16 for unlocking the locked state of the reel 13, a slide door 17 for opening and closing a tape outlet 12C provided in the cartridge case 12 across the lower shell 12A and the upper shell 12B, a door spring 18 for biasing the slide door 17 to a closed position of the tape outlet 12C, a write protect 19 for preventing erroneous erasure, and a cartridge memory 11.
  • a cartridge case 12 consisting of a lower shell 12A and an upper shell 12B
  • the reel 13 for winding the magnetic tape MT is substantially disk-shaped with an opening in the center, and is composed of a reel hub 13A and a flange 13B made of a hard material such as plastic.
  • a leader tape LT is connected to the outer peripheral end of the magnetic tape MT, and a leader pin 20 is provided at the tip of the leader tape LT.
  • the cartridge 10 may be a magnetic tape cartridge that conforms to the LTO (Linear Tape-Open) standard, or it may be a magnetic tape cartridge that conforms to a standard other than the LTO standard.
  • LTO Linear Tape-Open
  • the cartridge memory 11 is provided near one corner of the cartridge 10. When the cartridge 10 is loaded into the recording and playback device, the cartridge memory 11 faces the reader/writer of the recording and playback device.
  • the cartridge memory 11 communicates with the recording and playback device, specifically the reader/writer, using a wireless communication standard that complies with the LTO standard.
  • the cartridge memory 11 includes an antenna coil (communication unit) 31 that communicates with a reader/writer using a prescribed communication standard, a rectification/power circuit 32 that generates power from radio waves received by the antenna coil 31 using induced electromotive force and rectifies the power to generate power, a clock circuit 33 that generates a clock from the radio waves received by the antenna coil 31 using induced electromotive force, a detection/modulation circuit 34 that detects the radio waves received by the antenna coil 31 and modulates the signal to be transmitted by the antenna coil 31, a controller (control unit) 35 consisting of a logic circuit for determining commands and data from the digital signal extracted from the detection/modulation circuit 34 and processing the commands and data, and a memory (storage unit) 36 that stores information.
  • the cartridge memory 11 also includes a capacitor 37 connected in parallel to the antenna coil 31, and the antenna coil 31 and the capacitor 37 form a resonant circuit.
  • Memory 36 stores information related to cartridge 10.
  • Memory 36 is non-volatile memory (NVM).
  • the storage capacity of memory 36 is preferably approximately 32 KB or more.
  • the memory 36 may have a first memory area 36A and a second memory area 36B.
  • the first memory area 36A corresponds to the memory area of a cartridge memory of a magnetic tape standard prior to the specified generation (e.g., an LTO standard prior to LTO8), for example, and is an area for storing information conforming to the magnetic tape standard prior to the specified generation.
  • Information conforming to the magnetic tape standard prior to the specified generation is, for example, manufacturing information (e.g., a unique number for the cartridge 10), usage history (e.g., the number of times the tape has been pulled out (Thread Count)), etc.
  • the second memory area 36B corresponds to an extended memory area for the memory area of the cartridge memory of the magnetic tape standard before the specified generation (for example, the LTO standard before LTO8).
  • the second memory area 36B is an area for storing additional information.
  • the additional information means, for example, information related to the cartridge 10 that is not specified in the magnetic tape standard before the specified generation (for example, the LTO standard before LTO8).
  • the additional information includes, for example, at least one type of information selected from the group consisting of tension adjustment information, management ledger data, index information, and thumbnail information, but is not limited to these data.
  • the tension adjustment information is information for adjusting the tension applied in the longitudinal direction of the magnetic tape MT.
  • the tension adjustment information includes, for example, at least one type of information selected from the group consisting of information obtained by intermittently measuring the width between the servo bands in the longitudinal direction of the magnetic tape MT, tension information of the drive, and information on the temperature and humidity of the drive. These pieces of information may be managed in conjunction with information on the usage status of the cartridge 10. It is preferable that the tension adjustment information is obtained when data is recorded on the magnetic tape MT or before data is recorded.
  • Drive tension information refers to information about the tension applied to the magnetic tape MT in the longitudinal direction.
  • the management ledger data includes at least one type of data selected from the group consisting of the capacity, creation date, editing date, and storage location of the data file recorded on the magnetic tape MT.
  • the index information is metadata for searching the contents of the data file.
  • the thumbnail information is a thumbnail of the video or still image stored on the magnetic tape MT.
  • Memory 36 may have multiple banks. In this case, some of the multiple banks may form a first memory area 36A, and the remaining banks may form a second memory area 36B.
  • the antenna coil 31 induces an induced voltage by electromagnetic induction.
  • the controller 35 communicates with the recording and playback device via the antenna coil 31 using a specified communication standard. Specifically, for example, it performs mutual authentication, sending and receiving commands, and exchanging data.
  • the controller 35 stores information received from the recording and playback device via the antenna coil 31 in the memory 36.
  • the controller 35 stores tension adjustment information received from the recording and playback device via the antenna coil 31 in the second memory area 36B of the memory 36.
  • the controller 35 reads information from the memory 36 and transmits it to the recording and playback device via the antenna coil 31.
  • the controller 35 reads tension adjustment information from the second memory area 36B of the memory 36 and transmits it to the recording and playback device via the antenna coil 31.
  • the magnetic tape MT includes a long substrate 41, an underlayer 42 provided on one main surface (first main surface) of the substrate 41, a magnetic layer 43 provided on the underlayer 42, and a back layer 44 provided on the other main surface (second main surface) of the substrate 41.
  • the underlayer 42 and the back layer 44 are provided as necessary and may not be required.
  • the magnetic tape MT may be a perpendicular recording type magnetic recording medium or a longitudinal recording type magnetic recording medium. From the viewpoint of improving running performance, the magnetic tape MT preferably contains a lubricant.
  • the lubricant may be included in at least one layer of the underlayer 42 and the magnetic layer 43.
  • the magnetic tape MT may be one that complies with the LTO standard, or one that complies with a standard other than the LTO standard.
  • the width of the magnetic tape MT may be 1/2 inch, or may be wider than 1/2 inch. If the magnetic tape MT complies with the LTO standard, the width of the magnetic tape MT is 1/2 inch.
  • the magnetic tape MT may have a configuration that allows the width of the magnetic tape MT to be kept constant or nearly constant by adjusting the tension applied to the magnetic tape MT in the longitudinal direction during running using a recording/playback device (drive).
  • the magnetic tape MT is long and runs in the longitudinal direction during recording and playback.
  • the magnetic tape MT is preferably used in a recording and playback device equipped with a ring-type head as a recording head.
  • the magnetic tape MT is preferably used in a recording and playback device configured to be able to record data with a data track width of 1200 nm or less or 1000 nm or less.
  • the magnetic tape MT is preferably reproduced by a reproduction head using a TMR element.
  • the signal reproduced by the reproduction head using TMR may be data recorded in the data band DB (see FIG. 4) or a servo pattern (servo signal) recorded in the servo band SB (see FIG. 4).
  • the substrate 41 is a non-magnetic support that supports the underlayer 42 and the magnetic layer 43.
  • the substrate 41 has a long film shape.
  • the upper limit of the average thickness of the substrate 41 is preferably 4.40 ⁇ m or less, more preferably 4.20 ⁇ m or less, even more preferably 4.00 ⁇ m or less, 3.80 ⁇ m or less, or 3.40 ⁇ m or less.
  • the lower limit of the average thickness of the substrate 41 is preferably 3.00 ⁇ m or more, more preferably 3.20 ⁇ m or more.
  • the lower limit of the average thickness of the substrate 41 is 3.00 ⁇ m or more, the strength reduction of the substrate 41 can be suppressed.
  • the average thickness of the substrate 41 is determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and a sample is prepared by cutting the magnetic tape MT to a length of 250 mm at a position 30 to 40 m in the longitudinal direction from one end of the outer periphery of the magnetic tape MT.
  • longitudinal direction when referring to "the longitudinal direction from one end of the outer periphery of the magnetic tape MT” means the direction from one end of the outer periphery of the magnetic tape MT toward the other end of the inner periphery.
  • the layers of the sample other than the substrate 41 i.e., the underlayer 42, the magnetic layer 43, and the back layer 44
  • a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid.
  • the thickness of the sample (substrate 41) is measured at five positions using a Mitutoyo Laser Hologram (LGH-110C) as a measuring device, and the average thickness of the substrate 41 is calculated by simply averaging (arithmetic mean) these measurements. 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 MT.
  • the base 41 contains, for example, a polyester-based resin as a main component.
  • the polyester-based resin contains, for example, at least one selected from the group consisting of PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PBN (polybutylene naphthalate), PCT (polycyclohexylene dimethylene terephthalate), PEB (polyethylene-p(oxybenzoate), and polyethylene bisphenoxycarboxylate).
  • PET polyethylene terephthalate
  • PEN polyethylene naphthalate
  • PBT polybutylene terephthalate
  • PBN polybutylene naphthalate
  • PCT polycyclohexylene dimethylene terephthalate
  • PEB polyethylene-p(oxybenzoate
  • polyethylene bisphenoxycarboxylate polyethylene bisphenoxycarboxylate
  • the term "main component” means the component that is contained in the highest proportion among the components that constitute the base 41.
  • the content of the polyester-based resin in the base 41 may be, for example, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 98% by mass or more relative to the mass of the base 41, or the base 41 may be composed only of a polyester-based resin.
  • the substrate 41 contains polyester-based resin can be confirmed, for example, as follows. First, similar to the method for measuring the average thickness of the substrate 41, a magnetic tape MT is prepared and cut to a length of 250 mm to prepare a sample, and then the layers of the sample other than the substrate 41 are removed. Next, an IR spectrum of the sample (substrate 41) is obtained by infrared absorption spectrometry (IR). Based on this IR spectrum, it can be confirmed that the substrate 41 contains polyester-based resin.
  • IR infrared absorption spectrometry
  • the substrate 41 preferably contains a polyester-based resin.
  • the Young's modulus in the longitudinal direction of the substrate 41 can be reduced to preferably 2.5 GPa or more and 7.8 GPa or less, more preferably 3.0 GPa or more and 7.0 GPa or less. Therefore, by adjusting the tension in the longitudinal direction of the magnetic tape MT during running using a recording/playback device, the width of the magnetic tape MT can be kept constant or nearly constant. A method for measuring the Young's modulus in the longitudinal direction of the substrate 41 will be described later.
  • the base 41 may contain a resin other than polyester-based resin.
  • the resin other than polyester-based resin may be the main component of the constituent material of the base 41.
  • the content ratio of the resin other than polyester-based resin in the base 41 may be, for example, 50 mass% or more, 60 mass% or more, 70 mass% or more, 80 mass% or more, 90 mass% or more, 95 mass% or more, or 98 mass% or more relative to the mass of the base 41, or the base 41 may be composed only of a resin other than polyester-based resin.
  • the resin other than polyester-based resin includes, for example, at least one selected from the group consisting of polyolefin-based resins, cellulose derivatives, vinyl-based resins, and other polymer resins.
  • the base 41 contains two or more of these resins, the two or more materials may be mixed, copolymerized, or laminated.
  • the polyolefin resin includes, for example, at least one selected from the group consisting of PE (polyethylene) and PP (polypropylene).
  • the cellulose derivative includes, for example, at least one selected from the group consisting of cellulose diacetate, cellulose triacetate, CAB (cellulose acetate butyrate), and CAP (cellulose acetate propionate).
  • the vinyl resin includes, for example, at least one selected from the group consisting of PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride).
  • polymer resins include, for example, at least one selected from the group consisting of PEEK (polyetheretherketone), 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, PEK (polyetherketone), polyetherester, PES (polyethersulfone), PEI (polyetherimide), PSF (polysulfone), PPS (polyphenylene sulfide), PC (polycarbonate), PAR (polyarylate), and PU (polyurethane).
  • the base 41 may contain PEEK (polyetheretherketone), PA (polyamide, nylon), aromatic PA (aromatic polyamide, aramid), PI (polyimide), aromatic PI (aromatic polyimide), PAI (polyamideimide), aromatic PAI (aromatic polyamideimide), PBO (polybenzoxazole, for example Zylon (registered trademark)), polyether, PEK (polyetherketone), polyetherester, PES (polyethersulfone), PEI (polyetherimide), PSF (polysulfone), PPS (polyphenylene sulfide), PC (polycarbonate), PAR (polyarylate), or PU (polyurethane) as a main component.
  • PEEK polyetheretherketone
  • PA polyamide, nylon
  • aromatic PA aromatic polyamide, aramid
  • PI polyimide
  • PAI polyamideimide
  • PAI aromatic PAI (aromatic polyamideimide)
  • PBO poly
  • the substrate 41 may be biaxially stretched in the longitudinal and width directions.
  • the polymer resin contained in the substrate 41 is preferably oriented in a direction oblique to the width direction of the substrate 41.
  • the magnetic layer 43 is configured to be capable of recording signals by a magnetization pattern.
  • the magnetic layer 43 may be a perpendicular recording type recording layer or a longitudinal recording type recording layer.
  • the magnetic layer 43 includes, for example, a magnetic powder and a binder.
  • the magnetic layer 43 may further include at least one additive selected from the group consisting of conductive particles, lubricants, abrasive particles, hardeners, rust inhibitors, and non-magnetic reinforcing particles, as necessary.
  • the magnetic layer 43 may have a plurality of protrusions on the surface (magnetic surface) on the magnetic layer 43 side. The plurality of protrusions are formed, for example, by conductive particles and abrasive particles protruding from the magnetic surface.
  • the magnetic layer 43 may already have a plurality of servo bands SB and a plurality of data bands DB, as shown in FIG. 4.
  • the plurality of servo bands SB are arranged at equal intervals in the width direction of the magnetic tape MT.
  • a data band DB is provided between adjacent servo bands SB.
  • the servo bands SB are for guiding the head unit (magnetic head) 56 (specifically, servo read heads 56A, 56B) when recording or reproducing data.
  • a servo pattern (servo signal) for tracking control of the head unit 56 is written in advance in the servo bands SB. User data is recorded in the data bands DB.
  • the head unit 56 may be configured to be able to maintain an angle with respect to an axis Ax parallel to the width direction of the magnetic tape MT when recording and reproducing data, as shown in FIG. 4.
  • the head unit 56 may be configured to follow the meandering or deformation of the magnetic tape MT and become angled with respect to the axis Ax when recording and reproducing data.
  • the inclination angle of the head unit 56 with respect to the axis Ax parallel to the width direction of the magnetic tape MT is preferably 3° to 18°, more preferably 5° to 15°.
  • the lower limit of the ratio R S of the total area S SB of the multiple servo bands SB to the area S of the magnetic surface is preferably 1.0% or more, from the viewpoint of ensuring 5 or more servo bands SB.
  • the ratio R S of the total area S SB of the servo bands SB to the area S of the entire magnetic surface is calculated as follows.
  • the magnetic tape MT is developed using a ferricolloid developer (Sigma Marker Q, manufactured by Sigma High Chemical Co., Ltd.), and the developed magnetic tape MT is then observed under an optical microscope to measure the servo band width W SB and the number of servo bands SB.
  • the ratio R S is calculated from the following formula.
  • Ratio R S [%] (((servo band width W SB ) ⁇ (number of servo bands SB))/(width of magnetic tape MT)) ⁇ 100
  • the number of servo bands SB is, for example, 5+4n or more (where n is an integer equal to or greater than 0).
  • the number of servo bands SB is preferably 5 or more, and more preferably 9 or more. If the number of servo bands SB is 5 or more, the effect of dimensional changes in the width direction of the magnetic tape MT on the servo signal can be suppressed, ensuring stable recording and playback characteristics with less off-track.
  • the upper limit of the number of servo bands SB is not particularly limited, but is, for example, 33 or less.
  • the number of servo bands SB is calculated in the same manner as the ratio RS described above.
  • the upper limit of the servo band width WSB is preferably 95 ⁇ m or less, more preferably 65 ⁇ m or less, and even more preferably 50 ⁇ m or less.
  • the lower limit of the servo band width WSB is preferably 10 ⁇ m or more. It is difficult to manufacture a magnetic head capable of reading a servo signal with a servo band width WSB of less than 10 ⁇ m.
  • the width of the servo band width WSB is calculated in the same manner as the ratio RS described above.
  • the magnetic layer 43 is configured to allow multiple data tracks Tk to be formed in the data band DB.
  • the upper limit of the data track width W is preferably 1200 nm or less, more preferably 1000 nm or less, and even more preferably 850 nm or less, 800 nm or less, or 600 nm or less.
  • the lower limit of the data track width W is preferably 20 nm or more.
  • the data track width W is obtained as follows. First, a cartridge 10 with data recorded on the entire surface of the magnetic tape MT is prepared, the magnetic tape MT is unwound from the cartridge 10, and the magnetic tape MT is cut into a length of 250 mm at a position 30 to 40 m in the longitudinal direction from one end of the outer periphery of the magnetic tape MT to prepare a sample. Next, the data recording pattern of the data band DB part of the magnetic layer 43 of the sample is observed using a magnetic force microscope (MFM) to obtain an MFM image. As the MFM, Dimension3100 manufactured by Digital Instruments and its analysis software are used.
  • MFM Magnetic force microscope
  • the analysis software provided with the Dimension3100 is used to measure the track width.
  • the measurement conditions for the above MFM are sweep speed: 1 Hz, chip used: MFMR-20, lift height: 20 nm, correction: Flatten order 3.
  • the magnetic layer 43 is configured to be capable of recording data such that the minimum distance Lmin between magnetization reversals is preferably 47 nm or less, more preferably 44 nm or less, even more preferably 42 nm or less, and particularly preferably 40 nm or less.
  • the lower limit of the minimum distance Lmin between magnetization reversals is preferably 20 nm or more.
  • MFM magnetic force microscope
  • bit distances are measured from a two-dimensional concave-convex chart of the recording pattern of the obtained MFM image.
  • the measurement of the bit distance is performed using analysis software attached to Dimension3100.
  • the minimum distance between magnetization reversals Lmin is determined as the approximate greatest common divisor of the 50 measured distances between bits.
  • the measurement conditions are sweep speed: 1 Hz, chip used: MFMR-20, lift height: 20 nm, and correction: Flatten order 3.
  • the bit length L bit of the signal recorded in the data band DB is preferably 47 nm or less or 46 nm or less, more preferably 44 nm or less, even more preferably 42 nm or less, and particularly preferably 40 nm or less.
  • the bit length L bit of the signal recorded in the data band DB is determined in the same manner as the method for measuring the minimum value L min of the distance between magnetic reversals.
  • the bit area of the signal recorded in the data band DB is preferably 53,000 nm2 or less, more preferably 45,000 nm2 or less, even more preferably 37,000 nm2 or less, and particularly preferably 30,000 nm2 or less.
  • the bit area of the signal recorded in the data band DB is calculated as follows. First, three MFM images are obtained in the same manner as in the method for measuring the data track width W. Next, the data track width W and the bit length L bit are calculated in the same manner as in the method for measuring the data track width W and the bit length L bit . Next, the bit area (W ⁇ L bit ) of the signal recorded in the data band DB is calculated using the data track width W and the bit length L bit .
  • the servo pattern is a magnetized region, and is formed by magnetizing a specific region of the magnetic layer 43 in a specific direction with a servo write head during magnetic tape manufacturing.
  • the region of the servo band SB where the servo pattern is not formed (hereinafter referred to as the "non-pattern region") may be a magnetized region where the magnetic layer 43 is magnetized, or a non-magnetized region where the magnetic layer 43 is not magnetized.
  • the non-pattern region is a magnetized region
  • the servo pattern forming region and the non-pattern region are magnetized in different directions (e.g., opposite directions).
  • the servo band SB has a servo pattern formed thereon consisting of multiple servo stripes (linear magnetized regions) 113 inclined with respect to an axis Ax parallel to the width direction of the magnetic tape MT, as shown in FIG. 6.
  • the servo band SB includes multiple servo frames 110.
  • Each servo frame 110 is made up of 18 servo stripes 113.
  • each servo frame 110 is made up of a servo subframe 1 (111) and a servo subframe 2 (112).
  • Servo subframe 1 is composed of an A burst 111A and a B burst 111B.
  • the B burst 111B is disposed adjacent to the A burst 111A.
  • the A burst 111A has five servo stripes 113 formed at regular intervals and inclined at a predetermined angle ⁇ 1 with respect to an axis Ax parallel to the width direction of the magnetic tape MT. In Fig. 6, these five servo stripes 113 are indicated by the symbols A1 , A2 , A3 , A4 , and A5 from the EOT (End Of Tape) to the BOT (Beginning Of Tape) of the magnetic tape MT.
  • the B burst 111B has five servo stripes 113 formed at regular intervals and inclined at a predetermined angle ⁇ 2 with respect to an axis Ax parallel to the width direction of the magnetic tape MT.
  • these five servo stripes 113 are indicated by the symbols B1 , B2 , B3 , B4 , and B5 from the EOT to the BOT of the magnetic tape MT.
  • the servo stripes 113 of B burst 111B are inclined in the opposite direction to the servo stripes 113 of A burst 111A.
  • the servo stripes 113 of A burst 111A and the servo stripes 113 of B burst 111B are asymmetric with respect to the axis Ax parallel to the width direction of the magnetic tape MT. In other words, the servo stripes 113 of A burst 111A and the servo stripes 113 of B burst 111B are arranged in a roughly V-shape.
  • the servo stripes 113 of A burst 111A and the servo stripes 113 of B burst 111B are asymmetric with respect to the axis Ax, when the head unit 56 is inclined obliquely with respect to the axis Ax, there exists a state in which the servo stripes 113 of A burst 111A and the servo stripes 113 of B burst 111B are roughly symmetric with respect to the central axis of the sliding surface of the head unit 56.
  • By changing the inclination of the head unit 56 based on this state it becomes possible to adjust the distance between the servo read heads 56A, 56B in the width direction of the magnetic tape MT.
  • the servo read heads 56A, 56B can be made to face the specified positions of the servo band SB.
  • the central axis of the sliding surface of the head unit 56 means the axis that passes through the centers of the multiple servo read heads 56A, 56B on the sliding surface of the head unit 56.
  • the predetermined angle ⁇ 1 which is the inclination angle of the servo stripes 113 of the A burst 111A is different from the predetermined angle ⁇ 2 which is the inclination angle of the servo stripes 113 of the B burst 111B. More specifically, the predetermined angle ⁇ 1 of the servo stripes 113 of the A burst 111A may be larger than the predetermined angle ⁇ 2 of the servo stripes 113 of the B burst 111B, or the predetermined angle ⁇ 2 of the servo stripes 113 of the B burst 111B may be larger than the predetermined angle ⁇ 1 of the servo stripes 113 of the A burst 111A.
  • the inclination of the servo stripes 113 of the A burst 111A may be larger than the inclination of the servo stripes 113 of the B burst 111B, or the inclination of the servo stripes 113 of the B burst 111B may be larger than the inclination of the servo stripes 113 of the A burst 111A.
  • 6 shows an example in which the predetermined angle ⁇ 1 of the servo stripe 113 of the A burst 111A is larger than the predetermined angle ⁇ 2 of the servo stripe 113 of the B burst 111B.
  • Servo subframe 2 (112) is composed of a C burst 112C and a D burst 112D.
  • the D burst 112D is disposed adjacent to the C burst 112C.
  • the C burst 112C has four servo stripes 113 formed at a specified interval and inclined at a specified angle ⁇ 1 with respect to an axis Ax parallel to the width direction of the magnetic tape MT. In Fig. 6, these four servo stripes 113 are indicated by the symbols C1 , C2 , C3 , and C4 from the EOT to the BOT of the magnetic tape MT.
  • the D burst 112D has four servo stripes 113 formed at regular intervals and inclined at a predetermined angle ⁇ 2 with respect to an axis Ax parallel to the width direction of the magnetic tape MT.
  • these four servo stripes 113 are indicated by the symbols D1 , D2 , D3 , and D4 from the EOT to the BOT of the magnetic tape MT.
  • the servo stripes 113 of the D burst 112D are inclined in the opposite direction to the servo stripes 113 of the C burst 112C.
  • the servo stripes 113 of the C burst 112C and the servo stripes 113 of the D burst 112D are asymmetric with respect to the axis Ax parallel to the width direction of the magnetic tape MT. That is, the servo stripes 113 of the C burst 112C and the servo stripes 113 of the D burst 112D are arranged in a substantially V-shape.
  • the servo stripes 113 of the C burst 112C and the servo stripes 113 of the D burst 112D are asymmetric with respect to the axis Ax, when the head unit 56 is inclined obliquely with respect to the axis Ax, there exists a state in which the servo stripes 113 of the C burst 112C and the servo stripes 113 of the D burst 112D are substantially symmetric with respect to the central axis of the head unit 56. By changing the inclination of the head unit 56 based on this state, it becomes possible to adjust the servo distance.
  • the predetermined angle ⁇ 1 which is the inclination angle of the servo stripes 113 of the C burst 112C is different from the predetermined angle ⁇ 2 which is the inclination angle of the servo stripes 113 of the D burst 112D. More specifically, the predetermined angle ⁇ 1 of the servo stripes 113 of the C burst 112C may be larger than the predetermined angle ⁇ 2 of the servo stripes 113 of the D burst 112D, or the predetermined angle ⁇ 2 of the servo stripes 113 of the D burst 112D may be larger than the predetermined angle ⁇ 1 of the servo stripes 113 of the C burst 112C.
  • the inclination of the servo stripes 113 of the C burst 112C may be larger than the inclination of the servo stripes 113 of the D burst 112D, or the inclination of the servo stripes 113 of the D burst 112D may be larger than the inclination of the servo stripes 113 of the C burst 112C.
  • 6 shows an example in which the predetermined angle ⁇ 1 of the servo stripe 113 of the C burst 112C is larger than the predetermined angle ⁇ 2 of the servo stripe 113 of the D burst 112D.
  • the predetermined angle ⁇ 1 of the servo stripes 113 in the A burst 111A and the C burst 112C is preferably 18° or more and 28° or less, more preferably 18° or more and 26° or less.
  • the predetermined angle ⁇ 2 of the servo stripes 113 in the B burst 111B and the D burst 112D is preferably -4° or more and 6° or less, more preferably -2° or more and 6° or less.
  • the servo stripes 113 in the A burst 111A and the C burst 112C are an example of a first magnetized region.
  • the servo stripes 113 in the B burst 111B and the D burst 112D are an example of a second magnetized region.
  • the servo band SB is read by the head unit 56 to obtain information for obtaining the tape speed and the vertical position of the head unit 56.
  • the tape speed is calculated from the time between four timing signals (A1-C1, A2-C2, A3-C3, A4-C4).
  • the head position is calculated from the time between the aforementioned four timing signals and the time between another four timing signals (A1-B1, A2-B2, A3-B3, A4-B4).
  • the servo pattern may be a shape that includes two parallel lines.
  • the servo pattern (i.e., the multiple servo stripes 113) is preferably arranged linearly in the longitudinal direction of the magnetic tape MT.
  • the servo band SB is preferably linear in the longitudinal direction of the magnetic tape MT.
  • the upper limit of the average thickness t1 of the magnetic layer 43 is preferably 80 nm or less, more preferably 70 nm or less, even more preferably 60 nm or less, and particularly preferably 50 nm or less.
  • the upper limit of the average thickness t1 of the magnetic layer 43 is 80 nm or less, the influence of the demagnetizing field can be reduced when a ring-type head is used as the recording head, and therefore, even more excellent electromagnetic conversion characteristics can be obtained.
  • the lower limit of the average thickness t1 of the magnetic layer 43 is preferably 35 nm or more. If the lower limit of the average thickness t1 of the magnetic layer 43 is 35 nm or more, output can be ensured when an MR head is used as the reproducing head, and therefore further excellent electromagnetic conversion characteristics can be obtained.
  • the average thickness t1 of the magnetic layer 43 is obtained as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut out to a length of 250 mm from each of the positions 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m from one end of the outer periphery of the magnetic tape MT in the longitudinal direction to prepare three samples. Then, each sample is processed by the 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 described later.
  • the carbon layer is formed on the surface of the magnetic tape MT on the magnetic layer 43 side and the surface on the back layer 44 side by a vapor deposition method, and the tungsten layer is further formed on the surface on the magnetic layer 43 side by a vapor deposition method or a sputtering method.
  • the thinning is performed along the longitudinal direction of the magnetic tape MT. That is, the thinning forms a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic tape MT.
  • the thickness of the magnetic layer 43 is measured at 10 positions of each of the thin samples.
  • the measurement positions of the 10 points of each of the thin samples are randomly selected from the sample so that they are different positions in the longitudinal direction of the magnetic tape MT.
  • the average value obtained by simply averaging (arithmetic mean) the measured values of each of the obtained thin samples (a total of 30 thicknesses of the magnetic layer 43) is set as the average thickness t 1 [nm] of the magnetic layer 43.
  • the magnetic powder contains, for example, hexagonal ferrite particles as magnetic particles. It is preferable that the magnetic powder has a crystal orientation preferentially in the perpendicular direction of the magnetic tape MT.
  • the perpendicular direction (thickness direction) of the magnetic tape MT refers to the thickness direction of the magnetic tape MT.
  • Hexagonal ferrite particles have, for example, a plate shape such as a hexagonal plate, or a column shape such as a hexagonal column (where the thickness or height is smaller than the major axis of the plate surface or bottom surface).
  • a hexagonal plate shape is intended to include an approximately hexagonal plate shape.
  • a hexagonal column shape is intended to include an approximately hexagonal column shape.
  • 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 contains at least Ba.
  • the alkaline earth metal may further contain at least one of Sr and Ca, and among these metals, it is preferable that the metal M1 contains Sr.
  • the metal M1 may contain Pb.
  • the hexagonal ferrite particles may further contain metal M2 in addition to Fe and metal M1.
  • Metal M2 can substitute for Fe sites in the crystal structure of hexagonal ferrite.
  • Metal M2 contains, for example, at least 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.
  • rare earth elements refer to Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.
  • Transition metal elements other than Fe refer to Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Hf, Ta, and W.
  • Metal elements of Group 13 of the periodic table refer to Al, Ga, In, and Tl.
  • the hexagonal ferrite particles may be, for example, barium ferrite particles or strontium ferrite particles.
  • strontium ferrite particles refer to hexagonal ferrite particles in which the atomic ratio of Sr to metal M1 is 50 atomic % or more. Therefore, hexagonal ferrite particles containing Sr and a metal M1 other than Sr are included in strontium ferrite particles when the atomic ratio of Sr to metal M1 is 50 atomic % or more.
  • metal M1 contains Sr and Ba
  • 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.
  • barium ferrite particles refer to hexagonal ferrite particles in which the atomic ratio of Ba to metal M1 is 50 atomic % or more. Therefore, hexagonal ferrite particles containing Ba and a metal M1 other than Ba are included in barium ferrite particles if the atomic ratio of Ba to metal M1 is 50 atomic % or more. For example, when metal M1 contains Sr and Ba, hexagonal ferrite particles in which the atomic ratio of Ba to the total amount of Sr and Ba is 50 atomic % or more are called barium ferrite particles.
  • the hexagonal ferrite may have an average composition represented by the following general formula (1): Ba (1-x) ⁇ x Fe (12-y) ⁇ y O 19 ...(1)
  • ⁇ represents at least one element selected from the group consisting of Sr, 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 is within the range of 0 ⁇ y ⁇ 0.80, preferably 0.22 ⁇ y ⁇ 0.80, and more preferably 0.26 ⁇ y ⁇ 0.80.
  • the upper limit of the particle volume V XRD of the magnetic powder is 1300 nm 3 or less, preferably 1200 nm 3 or less, more preferably 1139 nm 3 or less, 1068 nm 3 or less, or 942 nm 3 or less. If the particle volume V XRD of the magnetic powder exceeds 1300 nm 3 , the number of magnetic particles contained in a unit area decreases, and the electric characteristic conversion characteristics deteriorate.
  • the particle volume V XRD of the magnetic powder refers to the crystallite volume of the magnetic powder obtained by taking out the constituent material of the magnetic layer 43 of the magnetic tape MT and measuring the constituent material by XRD.
  • the lower limit of the particle volume V XRD of the magnetic powder determined by X-ray diffraction is preferably 800 nm 3 or more, more preferably 900 nm 3 or more.
  • the particle volume V XRD of the magnetic powder is 800 nm 3 or more, the deterioration of the reproduction signal due to thermal fluctuation can be suppressed. Therefore, the electromagnetic conversion characteristics can be improved.
  • the numerical range of the particle volume VXRD of the magnetic particles may be defined by any one of the upper limits and any one of the lower limits, and may be preferably 800 nm3 or more and 1300 nm3 or less, more preferably 800 nm3 or more and 1200 nm3 or less, even more preferably 800 nm3 or more and 1139 nm3 or less, 800 nm3 or more and 1068 nm3 or less, or 800 nm3 or more and 942 nm3 or less.
  • the crystallite volume VXRD of the magnetic powder is obtained as follows. First, a reel 211 on which the magnetic tape MT is wound is attached to a transport system (e.g., MTS Transport 2' x 3' deck manufactured by Mountain Engineering II) shown in Fig. 7. A support member 215 and a blade 213 that support a nonwoven fabric 214 are provided in the transport system. The support member 215 is provided upstream of the blade 213 in the transport path. The nonwoven fabric 214 is soaked in a solvent such as ethanol, methyl ethyl ketone, or acetone.
  • a solvent such as ethanol, methyl ethyl ketone, or acetone.
  • one end of the magnetic tape MT on the outer periphery is unwound from reel 211, the magnetic tape MT is set on a predetermined running path provided with tape running guides 221, 222, 223, 224, 225, and 226, and one end of the magnetic tape MT is fixed to reel 212.
  • the traveling system is driven and the blade 213 and the nonwoven fabric 214 are slid on the surface of the magnetic layer 43.
  • the surface of the magnetic layer 43 is moistened by the nonwoven fabric 214, and then the surface of the magnetic layer 43 is thinly peeled off by the blade 213, and the exfoliated material (constituent material of the magnetic layer 43) 216 of the magnetic layer 43 is obtained.
  • the exfoliated material 216 is obtained until the amount of the exfoliated material 216 reaches the amount required for the XRD measurement described below.
  • the required amount of the exfoliated material 216 is obtained from the magnetic tape MT of two or more reels 211.
  • the required amount of the exfoliated material 216 is obtained by peeling off the magnetic layer 43 over a length of about 1000 m from the magnetic tape MT of one cartridge 10.
  • the peeled off material 216 is placed in a depression (square, 1.8 cm x 2.0 cm) of a non-reflective silicon sample plate for XRD, and a measurement sample is prepared by scraping it flat with a glass plate. The X-ray diffraction pattern of the measurement sample is then measured by the focusing method.
  • the crystallite size D1 obtained from the diffraction peak of the (0,0,6) plane is calculated, and for hexagonal ferrite containing Sr, the crystallite size D1 is calculated by multiplying the crystallite size obtained from the diffraction peak of the (1,1,4) plane by a correction coefficient of 0.5406 .
  • the crystallite size D1 is a value equivalent to the plate thickness of the particle.
  • the crystallite size D1 is calculated by multiplying the (1,1,4) plane, which has a relatively high strength, by a correction coefficient.
  • the crystallite size D2 is calculated from the diffraction peak of the (2,2,0) plane.
  • the crystallite size D2 is a value equivalent to the plate diameter of the particle. The following Scherrer formula is used to calculate the crystallite size D1 and the crystallite size D2 .
  • Dx K ⁇ /Bcos ⁇
  • Dx crystallite size (nm)
  • ⁇ wavelength of measured X-rays (nm)
  • B Broadening of the diffraction line due to the size of the crystallite (half-width of the diffraction peak)
  • ⁇ angle at which a diffraction peak appears
  • the crystallite volume V XRD of the magnetic powder is calculated using the following formula.
  • D1 is the crystallite size calculated from the diffraction peak of the ( 0,0,6 ) plane
  • D2 is the crystallite size calculated from the diffraction peak of the (2,2,0) plane.
  • the binder includes, for example, a thermoplastic resin.
  • the binder may further include a thermosetting resin or a reactive resin.
  • the thermoplastic resin includes a first thermoplastic resin (first binder) containing chlorine atoms and a second thermoplastic resin (second binder) containing nitrogen atoms. More specifically, the thermoplastic resin includes vinyl chloride resin and urethane resin.
  • vinyl chloride resin means a polymer containing a structural unit derived from vinyl chloride. More specifically, for example, vinyl chloride resin means a homopolymer of vinyl chloride, a polymer of vinyl chloride and a comonomer copolymerizable therewith, and a mixture of these polymers.
  • the vinyl chloride resin includes, for example, at least one selected from the group consisting of vinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylate-vinyl chloride-vinylidene chloride copolymer, and methacrylate-vinyl chloride copolymer.
  • a urethane-based resin means a resin that contains a urethane bond in at least a part of the molecular chain that constitutes the resin, and may be a urethane resin or a copolymer that contains a urethane bond in a part of the molecular chain.
  • the urethane-based resin may be, for example, one obtained by reacting a polyisocyanate with a polyol.
  • the urethane-based resin may be, for example, one obtained by reacting a polyester with a polyol.
  • the urethane-based resin also includes one obtained by reacting with a curing agent.
  • the polyisocyanate includes at least one selected from the group consisting of, for example, diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), 1,5-pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), and isophorone diisocyanate (IPDI).
  • MDI diphenylmethane diisocyanate
  • TDI tolylene diisocyanate
  • XDI xylylene diisocyanate
  • PDI 1,5-pentamethylene diisocyanate
  • HDI hexamethylene diisocyanate
  • IPDI isophorone diisocyanate
  • polyisocyanate means a compound having two or more isocyanate groups in the molecule.
  • the polyisocyanate may be the polyisocyanate contained in the curing agent.
  • the polyol includes at least one selected from the group consisting of, for example, polyols (diols) having two OH groups, polyols (triols) having three OH groups, polyols (tetraols) having four OH groups, polyols (pentaols) having five OH groups, and polyols (hexaols) having six OH groups.
  • the polyol includes at least one selected from the group consisting of, for example, polyester-based polyols, polyether-based polyols, polycarbonate-based polyols, polyesteramide-based polyols, and acrylate-based polyols.
  • the polyester includes, for example, at least one selected from the group consisting of phthalic acid-based polyesters and aliphatic polyesters.
  • the thermoplastic resin may further include a thermoplastic resin other than vinyl chloride resin and urethane resin.
  • a thermoplastic resin may include at least one selected from the group consisting of, for example, vinyl acetate, acrylic acid ester-acrylonitrile copolymer, acrylic acid ester-acrylonitrile copolymer, acrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-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 butadiene copolymer, polyester resin, amino resin, and synthetic rubber.
  • Thermosetting resin includes at least one selected from the group consisting of, for example, phenolic resin, epoxy resin, polyurethane curing resin, urea resin, melamine resin, alkyd resin, silicone resin, polyamine resin, and urea formaldehyde resin.
  • all of the above-mentioned binders may contain polar functional groups such as -SO 3 M, -OSO 3 M, -COOM, P ⁇ O(OM) 2 (wherein M represents a hydrogen atom or an alkali metal such as lithium, potassium or sodium), side chain amines having terminal groups represented by -NR1R2 or -NR1R2R3 + X- , main chain amines represented by >NR1R2 + X- (wherein R1, R2 and R3 represent a hydrogen atom or a hydrocarbon group, and X- represents a halogen element ion such as fluorine, chlorine, bromine or iodine, an inorganic ion or an organic ion), -OH, -SH, -CN and epoxy groups.
  • the amount of these polar functional groups introduced into the binder is preferably 10 -1 or more and 10 -8 mol/g or less, and more preferably 10 -2 or more and 10
  • Some of the conductive particles contained in the magnetic layer 43 may protrude from the magnetic surface to form multiple protrusions. By forming multiple protrusions from the conductive particles, the electrical resistance of the magnetic surface can be reduced, and charging of the magnetic surface can be suppressed. In addition, dynamic friction between the head unit 56 and the magnetic surface during running of the magnetic tape MT can be reduced.
  • the conductive particles are preferably an antistatic agent and a solid lubricant.
  • the conductive particles are preferably particles containing carbon.
  • As the carbon-containing particles for example, at least one type selected from the group consisting of carbon particles and hybrid particles can be used, and carbon particles are preferably used.
  • the average primary particle size of the conductive particles is preferably 100 nm or less. When the average primary particle size of the conductive particles is 100 nm or less, even when the conductive particles are particles with a large particle size distribution (e.g., carbon black, etc.), the inclusion of particles that are excessively large relative to the thickness of the magnetic layer 43 is suppressed.
  • carbon particles for example, one or more selected from the group consisting of carbon black, acetylene black, ketjen black, carbon nanotubes, and graphene can be used, and among these carbon particles, it is preferable to use carbon black.
  • carbon black for example, Seast TA manufactured by Tokai Carbon Co., Ltd., Asahi #15, #15HS, etc. manufactured by Asahi Carbon Co., Ltd. can be used.
  • the hybrid particles include carbon and a material other than carbon.
  • the material other than carbon is, for example, an organic material or an inorganic material.
  • the hybrid particles may be hybrid particles in which carbon is attached to the surface of an inorganic particle.
  • the hybrid particles may be hybrid carbon in which carbon is attached to the surface of a silica particle.
  • the lubricant may be a liquid lubricant.
  • the lubricant may be, for example, at least one selected from fatty acids and fatty acid esters, preferably both fatty acids and fatty acid esters.
  • the magnetic layer 43 containing a lubricant particularly the magnetic layer 43 containing both fatty acids and fatty acid esters, contributes to improving the running stability of the magnetic tape MT. More particularly, the magnetic layer 43 containing a lubricant and having pores achieves good running stability. The improvement in running stability is believed to be due to the lubricant adjusting the dynamic friction coefficient of the magnetic layer 43 side surface of the magnetic tape MT to a value suitable for running the magnetic tape MT.
  • the fatty acid may preferably be a compound represented by the following general formula (1) or (2).
  • the fatty acid may contain either a compound represented by the following general formula (1) or a compound represented by the following general formula (2), or may contain both.
  • the fatty acid ester may preferably be a compound represented by the following general formula (3), (4) or (5).
  • the fatty acid ester may contain one, two or three of the compounds represented by the following general formula (3), (4) and (5).
  • the lubricant contains either one or both of the compounds represented by general formula (1) and general formula (2), and one, two or three of the compounds represented by general formula (3), (4) and (5), thereby making it possible to suppress an increase in the dynamic friction coefficient due to repeated recording or playback of the magnetic tape MT.
  • k is an integer selected from the range of 14 or more and 22 or less, more preferably from the range of 14 or more and 18 or less.
  • Some of the abrasive particles contained in the magnetic layer 43 may protrude from the magnetic surface to form a plurality of protrusions. When the head unit 56 slides over the magnetic tape MT, the protrusions formed by the abrasive particles can come into contact with the head unit 56.
  • the lower limit of the Mohs hardness of the abrasive particles is preferably 7.0 or more, more preferably 7.5 or more, even more preferably 8.0 or more, and particularly preferably 8.5 or more, from the viewpoint of suppressing deformation due to contact with the head unit 56.
  • the upper limit of the Mohs hardness of the abrasive particles is preferably 9.5 or less, from the viewpoint of suppressing wear of the head unit 56.
  • the abrasive particles are preferably inorganic particles.
  • inorganic particles include ⁇ -alumina with an ⁇ conversion rate of 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, acicular ⁇ -iron oxide obtained by dehydrating and annealing magnetic iron oxide raw materials, and those surface-treated with aluminum and/or silica as necessary, diamond powder, etc.
  • alumina particles such as ⁇ -alumina, ⁇ -alumina, and ⁇ -alumina, and silicon carbide are preferably used.
  • the abrasive particles may be in any shape such as needle-shaped, spherical, or cube-shaped, but those with some corners in the shape are preferred because they have high abrasiveness.
  • the antistatic agent can reduce the electrical resistance of the magnetic surface and suppress charging of the magnetic surface.
  • the antistatic agent includes, for example, at least one selected from the group consisting of natural surfactants, nonionic surfactants, cationic surfactants, and the like.
  • the curing agent includes, for example, polyisocyanate.
  • the polyisocyanate may include, for example, diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), 1,5-pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), or the like as an isocyanate source.
  • the polyisocyanate may have a TMP adduct structure, an isocyanurate structure, a biuret structure, or an allophanate structure.
  • polyisocyanates include aromatic polyisocyanates such as an adduct of tolylene diisocyanate (TDI) and an active hydrogen compound, and aliphatic polyisocyanates such as an adduct of hexamethylene diisocyanate (HMDI) and an active hydrogen compound.
  • TDI tolylene diisocyanate
  • HMDI hexamethylene diisocyanate
  • the weight average molecular weight of these polyisocyanates is preferably in the range of 100 to 3,000.
  • rust inhibitor examples include phenols, naphthols, quinones, heterocyclic compounds containing a nitrogen atom, heterocyclic compounds containing an oxygen atom, and heterocyclic compounds containing a sulfur atom.
  • Non-magnetic reinforcing particles examples include aluminum oxide ( ⁇ , ⁇ or ⁇ alumina), chromium oxide, silicon oxide, diamond, garnet, emery, boron nitride, titanium carbide, silicon carbide, titanium carbide, titanium oxide (rutile or anatase type titanium oxide), and the like.
  • the underlayer 42 is intended to reduce the unevenness of the surface of the substrate 41 and adjust the unevenness of the magnetic surface.
  • the underlayer 42 is a non-magnetic layer containing non-magnetic particles, a binder, and a lubricant.
  • the underlayer 42 supplies the lubricant to the magnetic surface.
  • the underlayer 42 may further contain at least one additive selected from the group consisting of an antistatic agent, a hardener, an anti-rust agent, etc., as necessary.
  • the upper limit of the average thickness t2 of the underlayer 42 is preferably 0.90 ⁇ m or less, more preferably 0.80 ⁇ m or less, even more preferably 0.70 ⁇ m or less, and particularly preferably 0.60 ⁇ m or less. If the average thickness t2 of the underlayer 42 is 0.90 ⁇ m or less, the magnetic tape MT is more elastic due to an external force, so that the width of the magnetic tape MT can be more easily adjusted by adjusting the tension. From the viewpoint of mitigating the uneven shape on the surface of the base 41, the lower limit of the average thickness t2 of the underlayer 42 is preferably 0.30 ⁇ m or more.
  • the average thickness t2 of the underlayer 42 is determined in the same manner as the average thickness t1 of the magnetic layer 43. However, the magnification of the TEM image is appropriately adjusted according to the thickness of the underlayer 42.
  • the underlayer 42 preferably has a plurality of holes. By storing lubricant in these holes, it is possible to further suppress the decrease in the amount of lubricant supplied between the magnetic surface and the head unit 56 even after repeated recording or playback (i.e., even after the head unit 56 is in contact with the surface of the magnetic tape MT and the tape is repeatedly run). This makes it possible to further suppress the increase in the dynamic friction coefficient. In other words, it is possible to obtain even better running stability.
  • the non-magnetic particles include at least one of inorganic particles and organic particles.
  • the non-magnetic particles may be carbon particles such as carbon black.
  • One type of non-magnetic particles may be used alone, or two or more types of non-magnetic particles may be used in combination.
  • the inorganic particles include, for example, metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, or metal sulfides.
  • the shapes of the non-magnetic particles include, for example, various shapes such as needles, spheres, cubes, and plates, but are not limited to these shapes.
  • Binding agent, lubricant The binder and lubricant are the same as those in the magnetic layer 43 described above.
  • the antistatic agent, hardener and rust inhibitor are the same as those in the magnetic layer 43 described above.
  • the back layer 44 contains a binder and non-magnetic particles.
  • the back layer 44 may further contain at least one additive selected from the group consisting of a lubricant, a hardener, an antistatic agent, etc., as necessary.
  • the binder and non-magnetic particles are the same as those in the underlayer 42 described above.
  • the hardener and antistatic agent are the same as those in the magnetic layer 43 described above.
  • the average particle size of the non-magnetic particles is preferably 10 nm or more and 150 nm or less, more preferably 15 nm or more and 110 nm or less.
  • the average particle size of the non-magnetic particles is determined in the same manner as the average particle size of the magnetic particles described above.
  • the non-magnetic particles may include non-magnetic particles having two or more particle size distributions.
  • the upper limit of the average thickness of the back layer 44 is preferably 0.60 ⁇ m or less. If the upper limit of the average thickness of the back layer 44 is 0.60 ⁇ m or less, the thickness of the underlayer 42 and the base 41 can be kept thick even if the average thickness of the magnetic tape MT is 5.50 ⁇ m or less, so that the running stability of the magnetic tape MT within the recording and reproducing device can be maintained.
  • the lower limit of the average thickness of the back layer 44 is not particularly limited, but is, for example, 0.20 ⁇ m or more.
  • the average thickness t b of the back layer 44 is obtained as follows. First, the average thickness t T of the magnetic tape MT is measured. The method for measuring the average thickness t T is as described in the "Average Thickness of Magnetic Tape" below. Next, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut into a length of 250 mm at a position 30 to 40 m from one end of the outer periphery of the magnetic tape MT in the longitudinal direction to prepare a sample. Next, the back layer 44 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 44 is obtained from the following formula.
  • the above five measurement positions are randomly selected from the sample so that they are different positions in the longitudinal direction of the magnetic tape MT.
  • the upper limit of the average thickness (average total thickness) tT of the magnetic tape MT is preferably 5.50 ⁇ m or less, more preferably 5.30 ⁇ m or less, and even more preferably 5.10 ⁇ m or less, 4.90 ⁇ m or less, or 4.70 ⁇ m or less.
  • the lower limit of the average thickness tT of the magnetic tape MT is not particularly limited, but is, for example, 3.50 ⁇ m or more.
  • the average thickness tT of the magnetic tape MT is obtained as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut into a length of 250 mm at a position 30 to 40 m in the longitudinal direction from one end of the outer periphery of the magnetic tape MT 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 randomly selected from the sample so that they are different positions in the longitudinal direction of the magnetic tape MT.
  • LGH-110C Mitutoyo Laser Hologram
  • the ratio Hc/Hr of the coercive force Hc of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT to the residual coercive force Hr of the magnetic layer 43 measured by applying a pulse magnetic field in the perpendicular direction of the magnetic tape MT is 0.45 or less, preferably 0.44 or less, more preferably 0.43 or less, 0.42 or less, or 0.41 or less.
  • the ratio Hc/Hr is 0.45 or less, even when the particle volume V XRD of the magnetic powder is 1300 nm3 or less, the particle size distribution of the magnetic powder can be made sharp, so that the content of extremely small magnetic particles that may become non-magnetic bodies in the magnetic layer 43 can be suppressed. Therefore, even when the particle volume V XRD of the magnetic powder is 1300 nm3 or less, the electromagnetic conversion characteristics can be improved.
  • a pulsed magnetic field VSM refers to a VSM in which the pulse width of the applied magnetic field is very narrow compared to a general VSM, and the pulse width of the applied magnetic field is in the order of 10-8 sec.
  • magnetic powders with a high content of extremely small magnetic particles and a broad particle size distribution will have a large ratio Hc/Hr of Hc measured by VSM to Hr measured by a pulsed magnetic field VSM.
  • magnetic powders with a low content of extremely small magnetic particles and a sharp particle size distribution will have a small ratio Hc/Hr. Therefore, the sharpness of the particle size distribution of the magnetic powder can be evaluated based on the value of the ratio Hc/Hr.
  • the first particle size distribution shown in Figures 8A and 9A represents the particle size distribution of the same magnetic powder, and is an example where the ratio Hc/Hr is 0.45 or less.
  • the second particle size distribution shown in Figures 8B and 9B represents the particle size distribution of the same magnetic powder, and is an example where the ratio Hc/Hr exceeds 0.45.
  • the magnetic particles contained in region A1 exhibit the magnetic properties described below during VSM measurement.
  • Magnetic particles contained in region A1 Affected by thermal fluctuation, it is difficult to measure the coercive force Hc of the magnetic particles during VSM measurement.
  • Magnetic particles contained in region A2 The coercive force Hc is barely measurable by VSM measurement.
  • Magnetic particles contained in region A3 The coercive force Hc can be measured by VSM measurement.
  • the magnetic particles contained in region A1 are so small that they have no coercive force Hc, and therefore contribute very little to the coercive force Hc of the magnetic layer 43.
  • the second particle size distribution contains more coarse magnetic particles with a larger coercive force Hc than the first particle distribution. For this reason, even if the second particle size distribution contains a larger number of extremely small magnetic particles than the first particle distribution, the coercive force Hc of the magnetic layer 43 containing the magnetic powder of the second particle size distribution appears to be larger than the coercive force Hc of the magnetic layer 43 containing the magnetic powder of the first particle size distribution.
  • the magnetic particles contained in region B1, the magnetic particles contained in region B2, and the magnetic particles contained in region B3 exhibit the magnetic properties described below when measured with a pulsed magnetic field VSM.
  • Magnetic particles contained in region B1 These are magnetized by the pulsed magnetic field VSM and contribute to the residual coercivity Hr. However, the magnetization of the magnetic particles is easily lost after a signal is written, and there is a risk that they may become a noise component in the reproduced signal.
  • Magnetic particles contained in region B3 Since the coercive force Hc of the magnetic particles is large, it is difficult to write signals, and there is a risk that these particles will become noise components in the reproduced signal.
  • the obtained remanence Hr is less susceptible to thermal fluctuations and is therefore less susceptible to fluctuations due to the particle volume V of the magnetic powder.
  • the remanence Hr depends on the anisotropic magnetic field Hk and therefore varies depending on the shape and type of the magnetic powder, normalization by the remanence Hr makes it possible to discuss the particle size distribution regardless of the shape and type of the magnetic powder.
  • the ratio Hc/Hr is determined as follows.
  • the coercive force Hc of the magnetic layer 43 is obtained as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and six pieces of the magnetic tape MT are cut out at a position 30 m to 40 m from one end of the outer periphery of the magnetic tape MT in the longitudinal direction. At this time, marking is performed with any non-magnetic ink so that the longitudinal direction (running direction) of the magnetic tape MT can be recognized. Next, the three cut out magnetic tapes MT are stacked 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 MT) corresponding to the perpendicular direction of the magnetic tape MT (perpendicular direction of the magnetic tape MT) is measured using a vibrating sample magnetometer (VSM).
  • VSM vibrating sample magnetometer
  • the coatings (undercoat layer 42, magnetic layer 43, back layer 44, etc.) of the remaining three cut magnetic tapes MT are wiped off with acetone or ethanol, etc., leaving only the substrate 41.
  • the three obtained substrates 41 are then stacked with double-sided tape and punched out with a ⁇ 6.39 mm punch to prepare a sample for background correction (hereinafter simply referred to as a "correction sample").
  • the M-H loop of the correction sample (substrate 41) corresponding to the perpendicular direction of the substrate 41 (perpendicular direction of the magnetic tape MT) is measured using a VSM.
  • a high-sensitivity vibration sample magnetometer "VSM-P7-15 type" manufactured by Toei Industry Co., Ltd. is used.
  • 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.
  • background correction is performed by subtracting the M-H loop of the correction sample (substrate 41) from the M-H loop of the measurement sample (entire magnetic tape MT), and the M-H loop after background correction is obtained.
  • the measurement and analysis program included with the "VSM-P7-15" is used for this background correction calculation.
  • the coercive force Hc is obtained from the obtained M-H loop after background correction.
  • the measurement and analysis program included with the "VSM-P7-15” is used for this calculation. Note that all of the above M-H loop measurements are performed at 25°C ⁇ 2°C and 50% RH ⁇ 5% RH. Also, no "demagnetization field correction" is performed when measuring the M-H loop in the longitudinal direction of the magnetic tape MT.
  • the residual coercive force Hr of the magnetic layer 43 is obtained as follows.
  • a measurement sample a sample similar to the sample used to calculate the coercive force Hc is prepared, and a residual magnetization curve is obtained in the direction perpendicular to the film surface using a high-speed response characteristic evaluation device HR-PVSM20 (pulse magnetic field VSM) manufactured by Hayama Corporation as follows.
  • HR-PVSM20 pulse magnetic field VSM20 (pulse magnetic field VSM) manufactured by Hayama Corporation as follows.
  • a perpendicular magnetic field of about -3980 kA/m (-50 kOe) is applied to the measurement sample, and the magnetic field is returned to zero to create a residual magnetization state.
  • a magnetic field of about 40.2 kA/m (about 505 Oe) is applied in the opposite direction, and the magnetic field is returned to zero again to measure the residual magnetization amount.
  • the applied magnetic field at this time is a pulse magnetic field with a pulse width of 10 -8 sec.
  • measurements are repeated in which a magnetic field larger than the previous applied magnetic field of about 40.2 kA/m is applied and returned to zero, and the residual magnetization amount is plotted against the applied magnetic field to create a residual magnetization curve (DCD curve).
  • the measured magnetic field is up to about 20 kOe.
  • the measurement conditions are as follows: background correction and demagnetizing field correction are not performed.
  • a residual magnetization curve such as that shown in Figure 10 can be obtained.
  • phase correction is performed as necessary. The phase correction will be described later.
  • two points on either side of the X-axis are connected with a straight line, and the point where this line intersects with the X-axis is calculated as Hr.
  • phase correction will be described in more detail below.
  • the unit of magnetization is originally emu, but in the case of the high-speed response characteristic evaluation device, the magnetization amount in each applied magnetic field is output as a voltage V, and the magnetization amount (voltage V) in each applied magnetic field is output as a positive value regardless of whether it is positive or negative. Therefore, correction according to the phase in each applied magnetic field is necessary.
  • phase information data included in the output result by the high-speed response characteristic evaluation device is used.
  • the phase information data is also output for each applied magnetic field together with the magnetization amount (voltage V) in each applied magnetic field.
  • phase information data of the magnetization amount (voltage V) measured for a certain magnetic field is a negative value
  • the measured magnetization amount (voltage V) must be multiplied by "-1"
  • the value obtained by multiplying the measured magnetization amount (voltage V) by "-1” is used to obtain the residual magnetization curve.
  • the process of multiplying by "-1" is the phase correction described above.
  • phase information data of the magnetization amount (voltage V) measured for a certain magnetic field is a positive value, there is no need to multiply the measured magnetization amount (voltage V) by "-1", and the measured magnetization amount (voltage V) is used as is to obtain the remanent magnetization curve.
  • the ratio Hc/Hr is calculated using the coercive force Hc of the magnetic layer 43 and the residual coercive force Hr of the magnetic layer 43 calculated as described above.
  • the upper limit of the coercive force Hc of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT is preferably 3000 Oe or less, more preferably 2500 Oe or less. If the coercive force Hc is 3000 Oe or less, the increase in magnetic particles (e.g., coarse magnetic particles) having an excessively high coercive force Hc can be suppressed, and the increase in magnetic particles that make it difficult to record signals can be suppressed. Therefore, the noise of the reproduced signal can be reduced, and the electromagnetic conversion characteristics can be improved.
  • the lower limit of the coercive force Hc of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT is preferably 1500 Oe or more, and more preferably 1700 Oe or more. If the coercive force Hc is 1500 Oe or more, the increase in magnetic particles with excessively low coercive force Hc (e.g. extremely small magnetic particles) can be suppressed, and the increase in magnetic particles that have difficulty maintaining magnetization due to thermal fluctuation can be suppressed. This reduces noise in the playback signal and improves the electromagnetic conversion characteristics.
  • the numerical range of the coercive force Hc of the magnetic layer 43 may be defined by any of the upper limit values and any of the lower limit values, and is preferably 1500 Oe or more and 3000 Oe or less, and more preferably 1700 Oe or more and 2500 Oe or less.
  • the method for measuring the coercive force Hc of the magnetic layer 43 is as described above in the method for measuring the ratio Hc/Hr.
  • the upper limit of the residual coercivity Hr of the magnetic layer 43 measured by applying a pulse magnetic field in the perpendicular direction to the magnetic tape MT is preferably 5200 Oe or less, more preferably 5000 Oe or less, and even more preferably 4800 Oe or less. If the residual coercivity Hr is 5200 Oe or less, the increase of magnetic particles (e.g., coarse magnetic particles) having an excessively high residual coercivity Hr can be suppressed, and the increase of magnetic particles that make it difficult to record signals can be suppressed. Therefore, the noise of the reproduced signal can be reduced, and the electromagnetic conversion characteristics can be improved.
  • the lower limit of the remanent coercivity Hr of the magnetic layer 43 measured by applying a pulsed magnetic field perpendicular to the magnetic tape MT is preferably 3000 Oe or more. If the remanent coercivity Hr is 3000 Oe or more, the increase in magnetic particles with excessively low remanent coercivity Hr can be suppressed, and the increase in magnetic particles (e.g., extremely small magnetic particles) that have difficulty maintaining magnetization due to thermal fluctuation can be suppressed. This reduces noise in the playback signal and improves the electromagnetic conversion characteristics.
  • the numerical range of the remanence Hr of the magnetic layer 43 may be defined by any of the upper limit values and any of the lower limit values, and is preferably 3000 Oe or more and 5200 Oe or less, more preferably 3000 Oe or more and 5000 Oe or less, and even more preferably 3000 Oe or more and 4800 Oe or less.
  • the method for measuring the remanence Hr of the magnetic layer 43 is as described above in the method for measuring the ratio Hc/Hr.
  • the upper limit of the saturation magnetic field Hs of the magnetic layer 43 measured by applying a pulse magnetic field in the perpendicular direction of the magnetic tape MT is preferably 9200 Oe or less. If the saturation magnetic field Hs of the magnetic layer 43 is 9200 Oe or less, the increase of magnetic particles (e.g., coarse magnetic particles) having an excessively high saturation magnetic field Hs can be suppressed, and the increase of magnetic particles that make it difficult to record signals can be suppressed. Therefore, the noise of the reproduced signal can be reduced, and the electromagnetic conversion characteristics can be improved.
  • the lower limit of the saturation magnetic field Hs of the magnetic layer 43 measured by applying a pulse magnetic field in the perpendicular direction of the magnetic tape MT is, for example, 3000 Oe or more.
  • the saturation magnetic field Hs can be calculated as follows. First, the remanent magnetization curve of the magnetic layer 43 is calculated in the same manner as the above-mentioned method for measuring the ratio Hc/Hr. Next, the value of the magnetic field when the magnetization is saturated is calculated as the saturation magnetic field Hs.
  • the PSD Power Spectrum Density up to a spatial wavelength of 5 ⁇ m is preferably 1.33 nm2 or less, more preferably 1.25 nm2 or less, and even more preferably 1.15 nm2 or less. If the PSD up to a spatial wavelength of 5 ⁇ m is 1.33 nm2 or less, the magnetic surface becomes smooth, so that the spacing loss between the head unit 56 and the magnetic surface can be suppressed. Therefore, the electromagnetic conversion characteristics can be improved.
  • the PSD up to a spatial wavelength of 5 ⁇ m can be calculated as follows. First, the magnetic surface of the magnetic tape MT is observed with an atomic force microscope (AFM) to obtain two-dimensional (2D) surface profile data.
  • AFM atomic force microscope
  • the AFM used to measure the magnetic surface is shown below.
  • Equipment AFM Dimension 3100 microscope with NanoscopeIV controller (Digital Instruments, USA)
  • Cantilever NCH-10T (NanoWorld)
  • the AFM measurement conditions are as follows. Measurement area: 40 ⁇ m x 40 ⁇ m Resolution: 256x256 Scan direction of the AFM probe: MD direction (longitudinal direction) of the magnetic tape MT Measurement mode: tapping mode Scan ratio: 1Hz
  • PSD(k) MD power spectrum densities
  • the squareness ratio S1 of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT is preferably 62% or more, more preferably 65% or more, and even more preferably 68% or more, 72% or more, or 75% or more.
  • the squareness ratio S1 is 62% or more, the perpendicular orientation of the magnetic particles is sufficiently high, so that further excellent electromagnetic conversion characteristics can be obtained.
  • the squareness ratio S2 of the magnetic layer 43 in the longitudinal direction (running direction) of the magnetic tape MT is preferably 35% or less, more preferably 30% or less, and even more preferably 25% or less, 20% or less, or 15% or less. If the squareness ratio S2 is 35% or less, the vertical orientation of the magnetic particles is sufficiently high, and therefore even better electromagnetic conversion characteristics can be obtained. Note that one of the squareness ratio S1 of the magnetic layer 43 in the vertical direction of the magnetic tape MT and the squareness ratio S2 of the magnetic layer 43 in the longitudinal direction (running direction) of the magnetic tape MT may be within the above preferred range, and the other may be outside the above preferred range. Alternatively, both the squareness ratio S1 of the magnetic layer 43 in the vertical direction of the magnetic tape MT and the squareness ratio S2 of the magnetic layer 43 in the longitudinal direction (running direction) of the magnetic tape MT may be within the above preferred range.
  • the squareness ratio S2 in the longitudinal direction of the magnetic tape MT is determined in the same manner as the squareness ratio S1, except that the M-H loop is measured in the longitudinal direction (running direction) of the magnetic tape MT and the substrate 41.
  • ratio Hc2/Hc1 The ratio Hc2/Hc1 of the coercive force Hc1 of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT to the coercive force Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT is preferably Hc2/Hc1 ⁇ 0.8, more preferably The relationship of Hc2/Hc1 ⁇ 0.75 is satisfied, and more preferably, Hc2/Hc1 ⁇ 0.7, Hc2/Hc1 ⁇ 0.65 or Hc2/Hc1 ⁇ 0.6 is satisfied.
  • the degree of perpendicular orientation of the magnetic particles can be increased. This reduces the magnetization transition width and allows a high-output signal to be obtained during signal reproduction, resulting in even better electromagnetic conversion.
  • Hc2 when Hc2 is small, the magnetization reacts with good sensitivity to the magnetic field in the perpendicular direction from the recording head, so that a good recording pattern can be formed.
  • the ratio Hc2/Hc1 is Hc2/Hc1 ⁇ 0.8
  • it is particularly effective that the average thickness t1 of the magnetic layer 43 is 90 nm or less. If the average thickness t1 of the magnetic layer 43 exceeds 90 nm, when a ring-type head is used as a recording head, the lower region of the magnetic layer 43 (the region on the underlayer 42 side) is magnetized in the longitudinal direction of the magnetic tape MT, and the magnetic layer 43 may not be uniformly magnetized in the thickness direction. Therefore, even if the ratio Hc2/Hc1 is Hc2/Hc1 ⁇ 0.8 (i.e., even if the degree of perpendicular orientation of the magnetic particles is increased), there is a risk that further excellent electromagnetic conversion characteristics cannot be obtained.
  • Hc2/Hc1 is not particularly limited, but for example, 0.5 ⁇ Hc2/Hc1.
  • Hc2/Hc1 represents the degree of vertical orientation of the magnetic particles, and the smaller Hc2/Hc1 is, the higher the degree of vertical orientation of the magnetic particles.
  • the method for calculating the coercive force Hc1 of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT is as described above.
  • the coercive force Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT is calculated in the same manner as the coercive force Hc1 of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT, except that the M-H loop is measured in the longitudinal direction of the magnetic tape MT and the substrate 41.
  • the activation volume V act is preferably 8000 nm 3 or less, more preferably 6000 nm 3 or less, even more preferably 5000 nm 3 or less, 4000 nm 3 or less, or 3000 nm 3 or less.
  • the activation volume V act is 8000 nm 3 or less, Since the dispersion state of the magnetic particles is improved, the bit inversion region can be made steeper, and the deterioration of the magnetization signal recorded on the adjacent track due to the leakage magnetic field from the recording head can be suppressed. There is a risk that excellent electromagnetic conversion characteristics will not be obtained.
  • V act is calculated by the following formula derived by Street & Woolley.
  • V act (nm 3 ) k B ⁇ T ⁇ irr /( ⁇ 0 ⁇ Ms ⁇ S) (However, kB : Boltzmann constant (1.38 ⁇ 10 -23 J/K), T: temperature (K), ⁇ irr : irreversible magnetic susceptibility, ⁇ 0 : magnetic permeability of vacuum, S: magnetorheological coefficient, Ms: saturation magnetization (emu/cm 3 ))
  • the irreversible magnetic susceptibility X irr , saturation magnetization Ms, and magnetic viscosity coefficient S substituted into the above formula are determined using a VSM as follows.
  • the measurement direction using the VSM is the perpendicular direction (thickness direction) of the magnetic tape MT.
  • the measurement using the VSM is performed on a measurement sample cut out from a long magnetic tape MT at 25°C ⁇ 2°C and 50% RH ⁇ 5% RH.
  • no "demagnetization correction" is performed.
  • the irreversible magnetic susceptibility ⁇ irr is defined as the slope of the residual magnetization curve (DCD curve) near the residual coercivity Hr.
  • a magnetic field of -1193 kA/m (15 kOe) is applied to the entire magnetic tape MT. Then, the magnetic field is returned to zero to create a residual magnetization state. After that, a magnetic field of about 15.9 kA/m (200 Oe) is applied in the opposite direction, and the magnetic field is returned to zero again to measure the residual magnetization. A magnetic field 15.9 kA/m larger than the magnetic field is applied and then returned to zero.
  • the remanent magnetization is plotted against the applied magnetic field to measure the DCD curve.
  • the point where the remanence is reached is taken as Hr, and the DCD curve is differentiated to determine the slope of the DCD curve for each magnetic field.
  • the slope of this DCD curve near the remanence Hr is taken as ⁇ irr .
  • Magnetic viscosity coefficient S First, a magnetic field of -1193 kA/m (15 kOe) is applied to the entire magnetic tape MT (measurement sample), and the magnetic field is returned to zero to create a residual magnetization state. After that, a magnetic field equivalent to the value of the residual coercivity Hr obtained from the DCD curve is applied in the opposite direction. With the magnetic field applied, the amount of magnetization is continuously measured at regular time intervals for 1000 seconds. The magnetic viscosity coefficient S is calculated by referring to the relationship between time t and amount of magnetization M(t) obtained in this way in the following formula.
  • M(t) M0+S ⁇ ln(t) (where M(t) is the amount of magnetization at time t, M0 is the initial amount of magnetization, S is the magnetic viscosity coefficient, and ln(t) is the natural logarithm of time.)
  • the surface roughness Rb of the back surface (surface roughness of the back layer 44) satisfies Rb ⁇ 6.0 [nm].
  • Rb surface roughness of the back layer 44
  • the surface roughness Rb of the back surface is obtained as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut into a length of 100 mm at a position 30 to 40 m in the longitudinal direction from one end of the outer periphery of the magnetic tape MT to prepare a sample. Next, the sample is placed on a slide glass so that the surface to be measured (the surface on the magnetic layer 43 side) faces up, and the end of the sample is fixed with mending tape. The surface shape is measured using a VertScan (20x objective lens) as a measuring device, and the surface roughness Rb of the back surface is obtained from the following formula based on the ISO 25178 standard. The measurement conditions are as follows.
  • Non-contact roughness meter using optical interference (Ryoka Systems Co., Ltd. non-contact surface and layer cross-sectional shape measurement system VertScan R5500GL-M100-AC)
  • Objective lens 20x Measurement area: 640 x 480 pixels (field of view: approx.
  • Measurement mode phase Wavelength filter: 520 nm
  • CCD 1/3 inch
  • Noise reduction filter Smoothing 3x3
  • Surface correction Correction using quadratic polynomial approximation surface
  • Measurement software VS-Measure Version 5.5.2
  • Analysis software VS-viewer Version 5.5.5 After measuring the surface roughness at five points in the longitudinal direction of the magnetic tape MT as described above, the average value of the arithmetic mean roughness S a (nm) automatically calculated from the surface profile obtained at each position is defined as the surface roughness R b (nm) of the back surface.
  • the upper limit of the Young's modulus in the longitudinal direction of the magnetic tape MT is preferably 9.0 GPa or less, more preferably 8.0 GPa or less, even more preferably 7.5 GPa or less, and particularly preferably 7.1 GPa or less.
  • the Young's modulus in the longitudinal direction of the magnetic tape MT is 9.0 GPa or less, the elasticity of the magnetic tape MT due to external force is further increased, so that the adjustment of the width of the magnetic tape MT by tension adjustment becomes easier. Therefore, off-track can be further appropriately suppressed, and data recorded on the magnetic tape MT can be reproduced more accurately.
  • the lower limit of the Young's modulus in the longitudinal direction of the magnetic tape MT is preferably 3.0 GPa or more, more preferably 4.0 GPa or more.
  • the lower limit of the Young's modulus in the longitudinal direction of the magnetic tape MT is 3.0 GPa or more, the decrease in running stability can be suppressed.
  • the Young's modulus of the magnetic tape MT in the longitudinal direction is a value that indicates the resistance of the magnetic tape MT to expansion and contraction in the longitudinal direction due to external forces; the larger this value, the more difficult it is for the magnetic tape MT to expand and contract in the longitudinal direction due to external forces, and the smaller this value, the more easily the magnetic tape MT can expand and contract in the longitudinal direction due to external forces.
  • the Young's modulus in the longitudinal direction of the magnetic tape MT is a value related to the longitudinal direction of the magnetic tape MT, it also correlates with the difficulty of the magnetic tape MT to expand and contract in the width direction. In other words, the larger this value is, the more difficult it is for the magnetic tape MT to expand and contract in the width direction due to external forces, and the smaller this value is, the more easily the magnetic tape MT will expand and contract in the width direction due to external forces. Therefore, from the perspective of tension adjustment, it is advantageous for the Young's modulus in the longitudinal direction of the magnetic tape MT to be small as described above, 9.0 GPa or less.
  • a tensile tester (AG-100D, manufactured by Shimadzu Corporation) is used to measure the Young's modulus in the tape longitudinal direction.
  • the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut to a length of 180 mm at a position 30 to 40 m in the longitudinal direction from one end of the outer periphery of the magnetic tape MT to prepare a measurement sample.
  • a jig capable of fixing the tape width (1/2 inch) is attached to the tensile tester, and the top and bottom of the tape width are fixed. The distance (length of the tape between the chucks) is set to 100 mm.
  • the Young's modulus is calculated using the following formula.
  • E (N/m 2 ) (( ⁇ N/S)/( ⁇ x/L)) ⁇ 10 6 ⁇ N: Change in stress (N)
  • S Cross-sectional area of the test piece (mm 2 )
  • ⁇ x Elongation (mm)
  • L Distance between gripping jigs (mm)
  • the cross-sectional area S of the measurement sample 10S is the cross-sectional area before the tensile operation, and is calculated by multiplying the width (1/2 inch) of the measurement sample 10S by the thickness of the measurement sample 10S.
  • the range of tensile stress when performing the measurement is set to a linear region tensile stress range depending on the thickness of the magnetic tape MT, etc.
  • the stress range is set to 0.2 N to 0.7 N, and the stress change ( ⁇ N) and elongation ( ⁇ x) at this time are used for calculation.
  • the Young's modulus is measured at 25° C. ⁇ 2° C. and 50% RH ⁇ 5% RH.
  • the Young's modulus in the longitudinal direction of the substrate 41 is preferably 7.8 GPa or less, more preferably 7.0 GPa or less, even more preferably 6.6 GPa or less, and particularly preferably 6.4 GPa or less.
  • the Young's modulus in the longitudinal direction of the substrate 41 is 7.8 GPa or less, the elasticity of the magnetic tape MT due to external force is further increased, so that the adjustment of the width of the magnetic tape MT by tension adjustment becomes easier. Therefore, off-track can be further appropriately suppressed, and data recorded on the magnetic tape MT can be reproduced more accurately.
  • the lower limit of the Young's modulus in the longitudinal direction of the substrate 41 is preferably 2.5 GPa or more, more preferably 3.0 GPa or more.
  • the lower limit of the Young's modulus in the longitudinal direction of the substrate 41 is 2.5 GPa or more, the decrease in running stability can be suppressed.
  • the Young's modulus in the longitudinal direction of the substrate 41 is determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut out to a length of 180 mm at a position 30 to 40 m in the longitudinal direction from one end of the outer periphery of the magnetic tape MT. Next, the underlayer 42, magnetic layer 43, and back layer 44 are removed from the cut magnetic tape MT to obtain the substrate 41. Using this substrate 41, the Young's modulus in the longitudinal direction of the substrate 41 is determined in the same manner as for the Young's modulus in the longitudinal direction of the magnetic tape MT.
  • the thickness of the base 41 accounts for more than half of the total thickness of the magnetic tape MT. Therefore, the Young's modulus in the longitudinal direction of the base 41 correlates with the resistance of the magnetic tape MT to expansion and contraction due to external forces; the larger this value, the less likely the magnetic tape MT is to expand and contract in the width direction due to external forces, and the smaller this value, the more likely the magnetic tape MT is to expand and contract in the width direction due to external forces.
  • the Young's modulus in the longitudinal direction of the substrate 41 is a value related to the longitudinal direction of the magnetic tape MT, but it also correlates with the difficulty of the magnetic tape MT to expand and contract in the width direction. In other words, the larger this value is, the more difficult it is for the magnetic tape MT to expand and contract in the width direction due to external forces, and the smaller this value is, the more easily the magnetic tape MT will expand and contract in the width direction due to external forces. Therefore, from the perspective of tension adjustment, it is advantageous for the Young's modulus in the longitudinal direction of the substrate 41 to be small as described above, 7.8 GPa or less.
  • the hexagonal ferrite forming component (magnetic powder raw material) and the glass forming component (glass raw material) are mixed.
  • the hexagonal ferrite forming component and the magnetic raw material containing the glass forming component are placed in a container such as a plastic container, and then mixed for a predetermined time (for example, 60 minutes) using a powder mixer.
  • the glass-forming components are glass raw materials that exhibit a glass transition phenomenon and can be amorphized, i.e., glass raw materials that can be vitrified.
  • the glass-forming components include, for example, at least one of sodium tetraborate (Na 2 B 4 O 7 ) and boric acid (B 2 O 3 ).
  • the hexagonal ferrite forming component is a compound containing atoms that are constituent atoms of the crystal structure of hexagonal ferrite, and includes, for example, metal carbonate and iron oxide.
  • the metal carbonate includes at least barium carbonate (BaCO 3 ).
  • the metal carbonate may further include strontium carbonate (SrCO 3 ).
  • the iron oxide includes, for example, ferric oxide (Fe 2 O 3 ).
  • the content of SrCO 3 in the hexagonal ferrite forming component is preferably higher than the content of iron oxide in the hexagonal ferrite forming component.
  • the content of each component in the raw material mixture is determined according to the composition of the hexagonal ferrite particles to be obtained.
  • the content of glass-forming components in the raw material mixture is 30 mol% or less.
  • the raw material mixture can be prepared by weighing out the various components and then mixing them.
  • an oxide of the metal M2 may be further mixed in.
  • the oxide of the metal M2 includes at least one selected from the group consisting of, for example, titanium oxide (TiO 2 ), aluminum oxide (Al 2 O 3 ), and neodymium oxide (Nd 2 O 3 ).
  • the raw material mixture is melted to obtain a melt.
  • the raw material mixture can be melted, for example, by a glass melting furnace.
  • the raw material mixture is put into a crucible of a glass melting furnace and melted at a melting temperature of, for example, 1300°C to 1500°C.
  • the melting time may be appropriately set so that the raw material mixture is sufficiently melted.
  • the melting time may be, for example, 80 minutes. It is also preferable to melt the raw material mixture in the melting furnace while stirring it with a stirring device. This is to reduce the temperature unevenness in the melting furnace and promote the amorphization of the melt obtained by melting the raw material mixture.
  • the content of glass raw materials in the raw material mixture is reduced to, for example, 30 mol% or less, the content of components containing iron oxide (Fe 2 O 3 ) becomes relatively high. In that case, the melting point of the raw material mixture rises, so that a stirring operation is important to homogenize the temperature distribution in the furnace and eliminate uneven melting. In addition, stirring can prevent the melt from clogging the outlet when the melt is discharged from the melting furnace.
  • the stirring device may be configured to rotate at a speed of, for example, 30 rpm or more.
  • the melt obtained by dissolving the raw material mixture is quenched to generate an amorphous body containing an amorphous component.
  • the quenching can be carried out in the same manner as the quenching process usually performed to obtain an amorphous body by a glass crystallization method.
  • a method of quenching the melt while rolling it using a pair of cooling rolls rotated at high speed is suitable.
  • the pair of cooling rolls may be configured to maintain a constant surface temperature, for example, by circulating cooling water through an internal flow path. This is to stabilize the quenching efficiency and promote the amorphization of the melt.
  • the surface temperature of the cooling roll is set to, for example, 20°C.
  • the distance between the pair of cooling rolls is, for example, 1 mm or less
  • the discharge speed is, for example, 0.5 g/sec or more and 1.0 g/sec or less.
  • quenching means that the melted raw material mixture is rapidly cooled to near room temperature to put the melt into a disordered state (hereinafter referred to as an amorphous state). It is considered that one condition for making the melt into an amorphous state is that the cooling rate exceeds the crystal growth rate. By making the melt into an amorphous state, it is possible to control the growth of nanoparticles and the particle size of nanoparticles.
  • the particles will grow crystals before the material transitions to an amorphous state, and the amorphous and crystalline states will be mixed in the melt. Therefore, if the quenching is not successful and the melt of the raw material mixture does not become sufficiently amorphous, the amorphous and crystalline states will be mixed in the melt. Therefore, particles that grow from the amorphous state in the subsequent firing process and particles that grow from a crystalline state having a certain size in the firing process will be mixed in the magnetic powder (hexagonal ferrite magnetic powder). Therefore, it is thought that the particle size distribution and magnetic properties of the obtained magnetic powder (hexagonal ferrite magnetic powder) will vary.
  • the amorphous body containing the amorphous component is put into, for example, an electric furnace and fired. This results in a fired body in which hexagonal ferrite particles and crystallized glass components are precipitated.
  • the particle size of the precipitated hexagonal ferrite particles can be controlled by the firing conditions. Increasing the firing temperature (crystallization temperature) for crystallization leads to an increase in the particle size of the precipitated hexagonal ferrite particles. Therefore, it is preferable that the temperature is as low as possible and higher than the temperature at which crystallization of hexagonal ferrite occurs. Specifically, it is preferable to generate a crystallized product by firing the amorphous body at a firing temperature of 570°C to 630°C.
  • the firing time for crystallization (holding time at the above crystallization temperature) is, for example, 1 hour to 48 hours, and it is desirable to perform, for example, 8 hours or more.
  • the heating rate until the firing temperature is reached is 1.0°C/min to 10.0°C/min, for example, 5.0°C/min or less.
  • the firing process may be performed in one or two stages, or in three or more stages.
  • the sintered body is subjected to an acid treatment.
  • This dissolves the glass components surrounding the hexagonal ferrite particles, and the hexagonal ferrite particles are extracted.
  • the acid treatment may be performed, for example, by putting the sintered body into an acid such as acetic acid and washing it with a ball mill.
  • the sintered body after the acid treatment is centrifuged with a centrifuge and then decanted. This removes impurities such as glass components.
  • the pulverization treatment may be performed by either a dry method or a wet method.
  • At least one of Na 2 B 4 O 7 and B 2 O 3 is used as a glass raw material, and the content of at least one of Na 2 B 4 O 7 and B 2 O 3 as a glass raw material in the raw material mixture is 30 mol% or less.
  • the nucleation particles are, for example, Sr atoms contained in SrCO 3 and Fe atoms contained in Fe 2 O 3 as magnetic raw materials.
  • the content (molar ratio) of SrCO 3 in the magnetic raw material is set to be higher than the content (molar ratio) of Fe 2 O 3 in the magnetic raw material. That is, the content (molar ratio) of Sr is set to be higher than the content (molar ratio) of Fe. Therefore, a large number of hexagonal ferrite particles are generated. Therefore, it is considered that the coarsening of individual hexagonal ferrite particles is suppressed.
  • Strontium has a high tendency to be ionized, and dissolves in glass to a certain extent.
  • the paint for forming the undercoat layer is prepared by kneading and dispersing the non-magnetic particles and the binder in the solvent.
  • the paint for forming the magnetic layer is prepared by kneading and dispersing the magnetic particles and the binder in the solvent.
  • the following solvents, dispersing devices, and kneading devices can be used to prepare the paint for forming the magnetic layer and the paint for forming the undercoat layer.
  • Solvents used in preparing 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. These may be used alone or
  • 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, etc., but is not limited to these devices.
  • the dispersing device used in the above-mentioned paint preparation may be, for example, a roll mill, a ball mill, a horizontal sand mill, a vertical sand mill, a spike mill, a pin mill, a tower mill, a pearl mill (for example, the "DCP Mill” manufactured by Eirich), a homogenizer, an ultrasonic dispersing machine, etc., but is not limited to these devices.
  • a coating material for forming the underlayer is applied to one main surface of the substrate 41 and dried to form the underlayer 42.
  • a coating material for forming the magnetic layer is applied to the underlayer 42 and dried to form the magnetic layer 43 on the underlayer 42.
  • the magnetic particles may be magnetically oriented in the thickness direction of the substrate 41, for example, by a solenoid coil.
  • a back layer 44 is formed on the other main surface of the substrate 41. This results in the magnetic tape MT.
  • the order of forming the underlayer 42, the magnetic layer 43, and the back layer 44 is not limited to the above example.
  • the back layer 44 may be formed on the other main surface of the substrate 41, and then the underlayer 42 and the magnetic layer 43 may be formed in sequence on one main surface of the substrate 41.
  • the squareness ratios S1 and S2 are set to the desired values by, for example, adjusting the strength of the magnetic field applied to the coating film 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 film of the magnetic layer-forming paint.
  • the strength of the magnetic field applied to the coating film is preferably two to three times the coercive force of the magnetic particles.
  • the magnetic tape MT is cut to a predetermined width (for example, 1/2 inch width). In this manner, the magnetic tape MT is obtained.
  • the magnetic tape MT may be demagnetized and then a servo pattern may be written onto the magnetic tape MT.
  • the ratio Hc/Hr can be adjusted to a desired value by, for example, adjusting the composition ratio of the raw materials (composition ratio of Sr and Ba) in the manufacturing process of the magnetic powder, the content of the glass-forming components in the raw material mixture, and the firing conditions.
  • the firing conditions include, for example, the firing temperature, firing speed, and firing time.
  • the preferred ranges of the composition ratio of Sr and Ba, the content of the glass-forming components in the raw material mixture, the firing temperature, the firing speed, and the firing time are as described above.
  • the ratio Hc/Hr of the coercive force Hc of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT to the residual coercive force Hr of the magnetic layer 43 measured by applying a pulse magnetic field in the perpendicular direction of the magnetic tape MT is 0.45 or less.
  • the magnetic tape cartridge 10 is a one-reel type cartridge, but it may be a two-reel type cartridge.
  • Fig. 11 is an exploded perspective view showing an example of the configuration of a two-reel type cartridge 321.
  • the cartridge 321 comprises an upper half 302 made of synthetic resin, a transparent window member 323 that fits into and is fixed to a window portion 302a opened on the upper surface of the upper half 302, a reel holder 322 that is fixed to the inside of the upper half 302 and prevents the reels 306 and 307 from floating up, a lower half 305 that corresponds to the upper half 302, the reels 306 and 307 that are stored in the space formed by combining the upper half 302 and the lower half 305, the magnetic tape MT wound on the reels 306 and 307, a front lid 309 that closes the front opening formed by combining the upper half 302 and the lower half 305, and a back lid 309A that protects the magnetic tape MT exposed at this front opening.
  • Reels 306 and 307 are used to wind magnetic tape MT.
  • Reel 306 comprises a lower flange 306b having a cylindrical hub portion 306a in the center around which magnetic tape MT is wound, an upper flange 306c of approximately the same size as lower flange 306b, and a reel plate 311 sandwiched between hub portion 306a and upper flange 306c.
  • Reel 307 has the same configuration as reel 306.
  • the window member 323 has mounting holes 323a at positions corresponding to the reels 306 and 307 for attaching reel holders 322, which are reel holding means for preventing the reels from floating up.
  • the magnetic tape MT is the same as the magnetic tape MT in the first embodiment.
  • the average thickness of the magnetic tape, the average thickness of the magnetic layer, the average thickness of the underlayer, the average thickness of the back layer, and the average thickness of the base film (substrate) shown in Table 2 are values determined by the measurement method described in the above embodiment.
  • the particle volume V XRD of the magnetic powder shown in Table 3 is a value determined by the measurement method described in the above embodiment.
  • Example 1 Magnetic powder manufacturing process> The magnetic powder was produced by the following process.
  • the melt was quenched while flowing out of the crucible to produce an amorphous body containing an amorphous component.
  • the melt was quenched while rolling using a pair of cooling rolls whose surface temperature was set to 20° C. At that time, the gap between the pair of cooling rolls was 1 mm or less, and the discharge speed was 0.5 g/sec or more and 1.0 g/sec or less.
  • the sintering process was carried out as follows.
  • the sintering temperature was set to 620°C, and the heating rate from room temperature to the sintering temperature was set to 5.0°C/min.
  • the sintering temperature was maintained at 620°C for 8 hours (sintering time) after the sintering temperature reached 620°C. As a result, a crystallized material containing barium ferrite particles was obtained.
  • the obtained sintered body was subjected to an acid treatment to remove glass components and extract strontium ferrite particles.
  • Acetic acid was used for the acid treatment, and ball mill washing was performed. After that, centrifugal separation was performed in a centrifuge, and decantation was performed to obtain barium ferrite magnetic powder.
  • the barium ferrite magnetic powder was placed in an electric furnace and dried in an environment of 120° C. until the moisture content of the magnetic powder reached 2.0 (wt%) or less. As a result, the desired barium ferrite magnetic powder (hexagonal ferrite magnetic powder) was obtained.
  • Magnetic tape manufacturing process The magnetic tape was produced by the following process.
  • the magnetic layer forming paint was prepared as follows. First, the first composition having the following composition was kneaded with an extruder. The barium ferrite magnetic powder in the first composition was the barium ferrite magnetic powder prepared as described above. Next, the kneaded first composition and the second composition having the following composition were added to a stirring tank equipped with a disperser and premixed. Next, further mixing was performed with a dyno mill and filtering, and the magnetic layer forming paint was prepared.
  • the paint for forming the undercoat layer was prepared as follows. First, the third composition having the following composition was mixed with an extruder. Next, the mixed third composition and the fourth composition having the following composition were added to a stirring tank equipped with a disperser and premixed. Then, further mixing was performed with a dyno mill and filtering was performed to prepare the paint for forming the undercoat layer.
  • 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 Corporation, product name: #80
  • Polyester polyurethane 100.00 parts by mass
  • Methyl ethyl ketone 500.00 parts by mass Toluene: 400.00 parts by mass
  • Cyclohexanone 100.00 parts by mass
  • Polyisocyanate product name: Coronate L, manufactured by Tosoh Corporation
  • a paint for forming a back layer was applied to the other main surface of the PEN film and dried to form a back layer with an average thickness of 0.50 ⁇ m after calendaring. This resulted in a magnetic tape.
  • the cured magnetic tape was subjected to a calendering process to smooth the surface of the magnetic layer, at a calendering temperature of 100° C. and a calendering pressure of 200 kg/cm.
  • the magnetic tape obtained as described above was cut into a width of 1/2 inch (12.65 mm), resulting in a magnetic tape with an average thickness of 5.44 ⁇ m.
  • ⁇ Magnetic tape manufacturing process> In the preparation process of the coating material for forming the magnetic layer, the barium ferrite magnetic powder obtained as described above was used. In the coating process, a PEN film (substrate) having an average thickness shown in Table 2 was used, and the coating conditions for each coating material were adjusted so that the average thickness of the magnetic layer, the average thickness of the undercoat layer, and the average thickness of the back layer after calendaring were the values shown in Table 2.
  • a magnetic tape was obtained in the same manner as in the magnetic tape production process of Example 1 except for the above.
  • ⁇ Magnetic tape manufacturing process> In the preparation process of the coating material for forming the magnetic layer, the barium ferrite magnetic powder obtained as described above was used. In the coating process, a PEN film (substrate) having an average thickness shown in Table 2 was used, and the coating conditions for each coating material were adjusted so that the average thickness of the magnetic layer, the average thickness of the undercoat layer, and the average thickness of the back layer after calendaring were the values shown in Table 2.
  • a magnetic tape was obtained in the same manner as in the magnetic tape production process of Example 1 except for the above.
  • ⁇ Magnetic tape manufacturing process> In the preparation process of the coating material for forming the magnetic layer, the strontium ferrite magnetic powder obtained as described above was used. In the coating process, a PEN film (substrate) having an average thickness shown in Table 2 was used, and the coating conditions for each coating material were adjusted so that the average thickness of the magnetic layer, the average thickness of the undercoat layer, and the average thickness of the back layer after calendaring were the values shown in Table 2.
  • a magnetic tape was obtained in the same manner as in the magnetic tape production process of Example 1 except for the above.
  • ⁇ Magnetic tape manufacturing process> In the preparation process of the coating material for forming the magnetic layer, the barium ferrite magnetic powder obtained as described above was used. In the coating process, a PEN film (substrate) having an average thickness shown in Table 2 was used, and the coating conditions for each coating material were adjusted so that the average thickness of the magnetic layer, the average thickness of the undercoat layer, and the average thickness of the back layer after calendaring were the values shown in Table 2.
  • a magnetic tape was obtained in the same manner as in the magnetic tape production process of Example 1 except for the above.
  • the arithmetic mean roughness Ra of the magnetic surface was calculated as follows. First, the magnetic surface was observed by AFM to obtain an AFM image of 40 ⁇ m x 40 ⁇ m.
  • the AFM used was a Digital Instruments Dimension ICON and its analysis software, the cantilever was made of single crystal silicon (Note 1), and the measurement was performed with a tapping frequency of 200 to 400 Hz.
  • the deviation Z"(i) (
  • PSD PSD
  • the PSD was obtained up to a spatial wavelength of 5 ⁇ m on the magnetic surface.
  • the peak of the captured spectrum was then taken as the signal amount S, and the floor noise excluding the peak was integrated from 3 MHz to 20 MHz to obtain the noise amount N.
  • the ratio S/N of the signal amount S to the noise amount N was calculated as the SNR (Signal-to-Noise Ratio).
  • the calculated SNR was then converted into a relative value (dB) based on the SNR of Comparative Example 5 as the reference media.
  • the above evaluation results reveal the following:
  • the SNR of the magnetic tapes (Examples 1 to 3) having a ratio Hc/Hr of 0.45 or less is higher than the SNR of the magnetic tapes (Comparative Examples 1 to 5) having a ratio Hc/Hr of more than 0.45. Therefore, even when the particle volume of the magnetic powder contained in the magnetic layer is 1300 nm3 or less, the SNR of the magnetic tape can be improved by setting the ratio Hc/Hr to 0.45 or less.
  • the present disclosure may also employ the following configuration.
  • a tape-shaped magnetic recording medium A substrate;
  • a magnetic layer containing magnetic powder The particle volume of the magnetic powder determined by X-ray diffraction is 1,300 nm3 or less;
  • a ratio Hc/Hr of a coercive force Hc of the magnetic layer in a perpendicular direction of the magnetic recording medium to a residual coercive force Hr of the magnetic layer measured by applying a pulse magnetic field in the perpendicular direction of the magnetic recording medium is 0.45 or less;
  • Magnetic recording media
  • the coercivity Hc of the magnetic layer in the perpendicular direction of the magnetic recording medium is 3000 Oe or less; 1.
  • the residual coercivity Hr of the magnetic layer measured by applying a pulse magnetic field in a perpendicular direction to the magnetic recording medium is 5000 Oe or less;
  • a saturation magnetic field Hs of the magnetic layer measured by applying a pulse magnetic field in a perpendicular direction to the magnetic recording medium is 9200 Oe or less;
  • the PSD (Power Spectrum Density) up to a spatial wavelength of 5 ⁇ m is 1.33 nm2 or less.
  • the magnetic powder includes hexagonal ferrite particles.
  • the average thickness of the magnetic layer is 60 nm or less.
  • the average thickness of the underlayer is 0.90 ⁇ m or less.
  • the average thickness of the magnetic recording medium is 5.50 ⁇ m or less.
  • the magnetic layer has a servo pattern; the servo pattern includes a plurality of first magnetized regions and a plurality of second magnetized regions; the plurality of first magnetized regions and the plurality of second magnetized regions are asymmetric with respect to an axis parallel to a width direction of the magnetic recording medium;
  • a tilt angle of the first magnetization region with respect to the axis and a tilt angle of the second magnetization region with respect to the axis are different, a larger one of the inclination angle of the first magnetization region and the inclination angle of the second magnetization region is 18° or more and 28° or less;
  • a cartridge comprising the magnetic recording medium according to any one of (1) to (11).

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005327386A (ja) * 2004-05-14 2005-11-24 Fuji Photo Film Co Ltd 磁気記録媒体、サーボ信号書込ヘッドユニット及びサーボライタ
JP2021061075A (ja) * 2019-10-02 2021-04-15 ソニー株式会社 磁気記録媒体
JP2021114350A (ja) * 2020-01-20 2021-08-05 ソニーグループ株式会社 磁気記録媒体
WO2022158314A1 (ja) * 2021-01-20 2022-07-28 ソニーグループ株式会社 磁気記録媒体、磁気記録再生装置および磁気記録媒体カートリッジ

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005327386A (ja) * 2004-05-14 2005-11-24 Fuji Photo Film Co Ltd 磁気記録媒体、サーボ信号書込ヘッドユニット及びサーボライタ
JP2021061075A (ja) * 2019-10-02 2021-04-15 ソニー株式会社 磁気記録媒体
JP2021114350A (ja) * 2020-01-20 2021-08-05 ソニーグループ株式会社 磁気記録媒体
WO2022158314A1 (ja) * 2021-01-20 2022-07-28 ソニーグループ株式会社 磁気記録媒体、磁気記録再生装置および磁気記録媒体カートリッジ

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