WO2023002657A1 - 磁気記録媒体 - Google Patents

磁気記録媒体 Download PDF

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Publication number
WO2023002657A1
WO2023002657A1 PCT/JP2022/007137 JP2022007137W WO2023002657A1 WO 2023002657 A1 WO2023002657 A1 WO 2023002657A1 JP 2022007137 W JP2022007137 W JP 2022007137W WO 2023002657 A1 WO2023002657 A1 WO 2023002657A1
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WIPO (PCT)
Prior art keywords
magnetic
recording medium
particles
magnetic recording
fatty acid
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/JP2022/007137
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English (en)
French (fr)
Japanese (ja)
Inventor
泰啓 榎本
実 山鹿
太 佐々木
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Sony Group Corp
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Sony Group Corp
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Publication date
Application filed by Sony Group Corp filed Critical Sony Group Corp
Priority to JP2023536589A priority Critical patent/JP7823663B2/ja
Priority to US18/574,562 priority patent/US12597441B2/en
Publication of WO2023002657A1 publication Critical patent/WO2023002657A1/ja
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/74—Record carriers characterised by the form, e.g. sheet shaped to wrap around a drum
    • G11B5/78—Tape carriers
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B23/00—Record carriers not specific to the method of recording or reproducing; Accessories, e.g. containers, specially adapted for co-operation with the recording or reproducing apparatus ; Intermediate mediums; Apparatus or processes specially adapted for their manufacture
    • G11B23/02—Containers; Storing means both adapted to cooperate with the recording or reproducing means
    • G11B23/04—Magazines; Cassettes for webs or filaments
    • G11B23/08—Magazines; Cassettes for webs or filaments for housing webs or filaments having two distinct ends
    • G11B23/107—Magazines; Cassettes for webs or filaments for housing webs or filaments having two distinct ends using one reel or core, one end of the record carrier coming out of the magazine or cassette
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/41—Cleaning of heads
    • 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
    • G11B5/708—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 addition of non-magnetic particles to the 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
    • G11B5/71—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 lubricant
    • 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
    • G11B5/72—Protective coatings, e.g. anti-static or antifriction
    • G11B5/725—Protective coatings, e.g. anti-static or antifriction containing a lubricant, e.g. organic compounds
    • 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

Definitions

  • This technology relates to magnetic recording media.
  • Magnetic recording media are often used as media for recording large amounts of data.
  • Patent Document 1 discloses a tape having a multilayer structure including at least a magnetic layer, the total thickness of the tape being 5.6 ⁇ m or less, and the surface of the magnetic layer the depth D1 of the recesses divided by the thickness D2 of the magnetic layer is 15% or more; the magnetic layer is perpendicularly oriented; The magnetic layer has a degree of vertical orientation of 65% or more, and a plurality of recesses having a thickness of 20% or more of the thickness of the magnetic layer are formed in the magnetic layer, and the number of the recesses is 6,000 of the magnetic layer.
  • a magnetic recording tape is disclosed that has 55 or more per 400 ⁇ m 2 surface area.
  • magnetic tapes magnetic recording media
  • magnetic tapes magnetic recording media
  • the demand for the reliability of magnetic tapes is also increasing.
  • a solid lubricant component for example, carbon particles acting as the solid lubricant.
  • a component for example, particles with a high Mohs hardness, particularly alumina, etc.
  • abrasive effect for magnetic head cleaning.
  • Inclusion of a combination of these two components in the magnetic tape is conceivable to prevent frictional force increase and to clean the magnetic head.
  • the abrasive force is too high, the magnetic head itself may be damaged, or the amount of heat and electrification generated by friction may increase, thereby increasing the damage to the magnetic head.
  • the main purpose of this technology is to provide a magnetic recording medium with a high recording density that can prevent an increase in frictional force even when it is run many times. Furthermore, in addition to preventing the increase in frictional force, this technology can reduce damage to the magnetic head by efficiently exposing fatty acids and fatty acid esters to the surface while maintaining polishing force during multiple runs. It is a further object to provide a magnetic recording medium capable of
  • This technology has a magnetic layer containing magnetic powder,
  • the magnetic layer contains first particles having conductivity and second particles having a Mohs hardness of 7 or more, protrusions are formed on the surface of the magnetic layer by the first particles and the second particles;
  • a magnetic recording medium in which the average height (H2) of projections formed by the second particles is 7 nm or less, contains a fatty acid, and has an extraction rate of 45% or more for the fatty acid defined by the following formula.
  • Fatty acid extraction rate (%) [5-minute fatty acid extraction amount (mg/m 2 )/total fatty acid extraction amount (mg/m 2 )] ⁇ 100
  • the 5-minute extraction amount (mg/m 2 ) of fatty acids may be 3.0 mg/m 2 or more.
  • the total amount of fatty acid extracted (mg/m 2 ) may be 5.0 mg/m 2 or more.
  • the fatty acid may be stearic acid.
  • the magnetic recording medium may further include a fatty acid ester, and the extraction rate of the fatty acid ester defined by the following formula may be 60% or more.
  • Fatty acid ester extraction rate (%) [5-minute extraction amount of fatty acid ester (mg/m 2 )/total extraction amount of fatty acid ester (mg/m 2 )] ⁇ 100
  • the 5-minute extraction amount (mg/m 2 ) of the fatty acid ester may be 10.0 mg/m 2 or more.
  • the total amount of fatty acid ester extracted (mg/m 2 ) may be 12.0 mg/m 2 or more.
  • the fatty acid ester may be butyl stearate.
  • the average thickness of the magnetic layer may be 0.08 ⁇ m or less.
  • the magnetic recording medium may further have a non-magnetic layer.
  • the average thickness of the non-magnetic layer may be 1.2 ⁇ m or less.
  • the average thickness (average total thickness) can be 5.7 ⁇ m or less.
  • the surface of the magnetic powder may be coated with a coating agent.
  • the coating agent can be an organic acid.
  • the second particles may be inorganic particles.
  • the second particles may be alumina particles.
  • FIG. 1 is a cross-sectional view showing the configuration of a magnetic recording medium according to a first embodiment
  • FIG. 1 is a schematic diagram showing the configuration of a recording/reproducing device
  • FIG. 10 is a cross-sectional view showing the configuration of a magnetic recording medium in a modified example
  • 1 is an exploded perspective view showing an example of the configuration of a magnetic recording cartridge
  • FIG. 4 is a block diagram showing an example of the configuration of a cartridge memory
  • FIG. FIG. 11 is an exploded perspective view showing an example of the configuration of a modification of the magnetic recording cartridge; It is an image which shows an example of the surface shape imaged by AFM. It is a figure which shows an example of the projection analysis result by AFM.
  • FIG. 2 is a diagram showing an example of the shape of particles of magnetic powder; It is an example of a TEM photograph of a sample cross section. It is another example of a TEM photograph of a cross section of a sample.
  • FIG. 2 is a diagram showing an example of a sample mount used for measuring the extraction rate of fatty acid or fatty acid ester.
  • the measurement shall be performed in an environment of 25°C ⁇ 2°C and 50% RH ⁇ 5% RH.
  • the present inventors have found that by adjusting the extraction rate of the fatty acid or fatty acid ester contained in the magnetic recording medium as a lubricant described below and by adjusting the height of the projections formed by the second particles, It has been found that an increase in frictional force can be prevented.
  • a magnetic recording medium has a magnetic layer containing magnetic powder, and the magnetic layer contains first particles having conductivity and second particles having a Mohs hardness of 7 or more.
  • the first particles may have electrical conductivity and function as a solid lubricant.
  • the second particles have a Mohs hardness of 7 or more, preferably 9 or more, and can have a polishing effect and an anchoring effect.
  • the first particles and the second particles form projections on the magnetic layer side surface.
  • the method for measuring the average height (H 2 ) of the protrusions of the second particles is described in 2. below. (3) explains.
  • the average height (H 2 ) of protrusions formed by the second particles is 7 nm or less, preferably 6.5 nm or less, more preferably 6.0 nm or less, and even more preferably 5.5 nm. Below, and more preferably below 5.3 nm.
  • the lower limit of the average height (H 2 ) of the protrusions formed by the second particles is not particularly limited. Preferably, it may be 3.0 nm or more.
  • a magnetic recording medium according to this technology contains a fatty acid.
  • the magnetic recording medium according to the present technology may further include a fatty acid ester. Such fatty acid or fatty acid ester bleeds onto the surface of the magnetic recording medium and coats the surface of the second particles with the fatty acid or fatty acid ester, thereby reducing damage to the magnetic head.
  • the fatty acid or fatty acid ester is contained in the non-magnetic layer (underlayer) and magnetic layer.
  • Fatty acids are usually trapped in magnetic powder or non-magnetic powder and hardly seep out onto the surface of the magnetic recording medium.
  • the extraction rate of the fatty acid or fatty acid ester is used as an index of how easily the fatty acid or fatty acid ester oozes out from the surface of the magnetic recording medium. That is, a large extraction rate value means that the fatty acid or fatty acid ester is less likely to be captured by the magnetic powder or the like and is likely to exude, and a small extraction rate means that the fatty acid or fatty acid ester magnetic powder It means that the degree of capture by such as is large and it is difficult to seep out.
  • the following method may be adopted in order to improve the extraction rate of fatty acid or fatty acid ester.
  • a coating agent Organic acids having one or more polar groups such as carboxylic acid, phosphonic acid, and sulfonic acid, and metals thereof A method of coating the surface of a magnetic powder or a non-magnetic powder with a coating agent that functions as an acid group, such as a salt.
  • a coupling agent silane, aluminum, titanium, etc.
  • the fatty acid extraction rate defined by the following formula may be 45% or higher, preferably 50% or higher, more preferably 55% or higher, and even more preferably 60% or higher. If the fatty acid extraction rate is less than 45%, the friction increases, the magnetic head deteriorates due to frictional heat and electrification, the damage to the coating film increases, the powder falling off increases, and the durability deteriorates. do.
  • Fatty acid extraction rate (%) [5-minute fatty acid extraction amount (mg/m 2 )/total fatty acid extraction amount (mg/m 2 )] ⁇ 100
  • the upper limit of the extraction rate of the fatty acid is not particularly limited, but from the viewpoint of suppressing the plasticization of the coating film itself, increased powder falloff, and deterioration of durability, it is preferably 75%. or less, more preferably 73% or less, and even more preferably 70% or less.
  • the method for measuring the extraction rate of fatty acids is described in 2. below. (3) explains.
  • the 5-minute extraction amount (mg/m 2 ) of the fatty acid is preferably 3.0 mg/m 2 or more, more preferably 3.5 mg/m 2 or more, still more preferably 4.0 mg/m 2 or more, and still more preferably 4.0 mg/m 2 or more. Preferably, it may be 4.5 mg/m 2 or more.
  • the upper limit of the 5-minute extraction amount of the fatty acid is not particularly limited, but is preferably 14.0 mg/m 2 or less, more preferably 13.0 mg/m 2 or less, and still more preferably 12.0 mg/m 2 or less. m 2 or less, even more preferably 10.0 mg/m 2 or less.
  • the method for measuring the 5-minute extraction amount of fatty acids is described in 2. below. (3) explains.
  • the total extraction amount (mg/m 2 ) of the fatty acid is preferably 5.0 mg/m 2 or more, more preferably 7.0 mg/m 2 or more, still more preferably 9.0 mg/m 2 or more, and even more preferably can be greater than or equal to 10.0 mg/m 2 .
  • the upper limit of the total extraction amount of the fatty acid is not particularly limited, but is preferably 16.0 mg/m 2 or less, more preferably 15.0 mg/m 2 or less, still more preferably 14.0 mg/m 2 or less. 2 or less, and even more preferably 13.0 mg/m 2 or less.
  • the method for measuring the total amount of fatty acid extracted is described in 2. below. (3) explains.
  • the magnetic recording medium according to the present technology further contains a fatty acid ester, which increases friction, degrades the magnetic head due to frictional heat and electrification, increases damage to the coating film, increases powder falling off, and further improves durability.
  • the extraction rate of the fatty acid ester defined by the following formula is preferably 60% or more, more preferably 65% or more, still more preferably 70% or more, and still more preferably 75% or more.
  • Fatty acid ester extraction rate (%) [5-minute extraction amount of fatty acid ester (mg/m 2 )/total extraction amount of fatty acid ester (mg/m 2 )] ⁇ 100
  • the upper limit of the extraction rate of the fatty acid ester is not particularly limited, but from the viewpoint of suppressing the plasticization of the coating film itself, the increase in powder falling, and the deterioration in durability, it is preferably 90. % or less, more preferably 85% or less, and even more preferably 80% or less.
  • the method for measuring the extraction rate of fatty acid ester is described in 2. below. (3) explains.
  • the 5-minute extraction amount (mg/m 2 ) of the fatty acid ester is preferably 10.0 mg/m 2 or more, more preferably 12.0 mg/m 2 or more, still more preferably 14.0 mg/m 2 or more, and further preferably 14.0 mg/m 2 or more. More preferably, it may be 16.0 mg/m 2 or more.
  • the upper limit of the 5-minute extraction amount of the fatty acid ester is not particularly limited, but if it exceeds 25.0 mg/m 2 , the plasticization of the coating progresses, and there is a possibility that powder falling off will worsen. , preferably 20.0 mg/m 2 or less, more preferably 19.0 mg/m 2 or less, still more preferably 18.0 mg/m 2 or less, and even more preferably 17.0 mg/m 2 or less.
  • the method for measuring the amount of fatty acid ester extracted for 5 minutes is described in 2 below. (3) explains.
  • the total extraction amount (mg/m 2 ) of the fatty acid ester is preferably 12.0 mg/m 2 or more, more preferably 14.0 mg/m 2 or more, still more preferably 16.0 mg/m 2 or more, and still more preferably 16.0 mg/m 2 or more. Preferably, it may be 19.0 mg/m 2 or more.
  • the upper limit of the total extraction amount of the fatty acid ester is not particularly limited, but is preferably 25.0 mg/m 2 or less, more preferably 24.0 mg/m 2 or less, and still more preferably 23.0 mg/m 2 or less. m 2 or less, even more preferably 22.0 mg/m 2 or less.
  • the method for measuring the total extraction amount of fatty acid ester is described in 2. below. (3) explains.
  • a magnetic recording medium according to the present technology is preferably a long magnetic recording medium, and can be, for example, a magnetic recording tape (particularly a long magnetic recording tape).
  • a magnetic recording medium may include a magnetic layer, a nonmagnetic layer (underlayer), a base layer, and a back layer in this order, and may include other layers in addition to these layers.
  • the other layer may be appropriately selected according to the type of magnetic recording medium.
  • the magnetic recording medium is a coating type magnetic recording medium. For layers included in the magnetic recording medium other than the above four layers, refer to these descriptions.
  • the average thickness (average total thickness) tT of the magnetic recording medium according to the present technology is, for example, preferably 5.7 ⁇ m or less, 5.6 ⁇ m or less, 5.5 ⁇ m or less, 5.4 ⁇ m or less, 5.3 ⁇ m or less, more preferably It may be 5.2 ⁇ m or less, 5.0 ⁇ m or less, more preferably 4.6 ⁇ m or less, still more preferably 4.4 ⁇ m or less. Since the magnetic recording medium is so thin, it is possible, for example, to increase the tape length wound up in one magnetic recording cartridge, thereby increasing the recording capacity per magnetic recording cartridge. can be done.
  • the lower limit of the average thickness (average total thickness) tT of the magnetic recording medium is not particularly limited, it is, for example, 3.5 ⁇ m ⁇ tT .
  • the average thickness tm of the magnetic layer of the magnetic recording medium according to the present technology is preferably 0.08 ⁇ m or less, more preferably 0.07 ⁇ m or less, even more preferably 0.06 ⁇ m or less, 0.05 ⁇ m or less, and even more preferably 0.05 ⁇ m or less. 04 ⁇ m or less.
  • the lower limit of the average thickness tm of the magnetic layer is not particularly limited, it may preferably be 0.03 ⁇ m or more.
  • the method for measuring the average thickness of the magnetic layer is described in 2. below. (3) explains.
  • the average thickness of the non-magnetic layer (average thickness of the underlayer) of the magnetic recording medium according to the present technology is preferably 1.2 ⁇ m or less, more preferably 1.0 ⁇ m or less, 0.9 ⁇ m or less, or 0.8 ⁇ m or less, or 0 0.7 ⁇ m or less, more preferably 0.6 ⁇ m or less.
  • the lower limit of the average thickness of the non-magnetic layer is not particularly limited, but is preferably 0.2 ⁇ m or more, more preferably 0.3 ⁇ m or more.
  • the method for measuring the average thickness of the non-magnetic layer is described in 2. below. (3) explains.
  • the average thickness of the base layer of the magnetic recording medium according to the present technology can be preferably 4.5 ⁇ m or less, more preferably 4.2 ⁇ m or less, 4.0 ⁇ m or less, 3.6 ⁇ m or less, and even more preferably 3.0 ⁇ m or less.
  • the method for measuring the average thickness of the base layer is described in 2. below. (3) explains.
  • the average thickness of the back layer of the magnetic recording medium according to the present technology can be preferably 0.6 ⁇ m or less, more preferably 0.5 ⁇ m or less, even more preferably 0.4 ⁇ m or less, 0.3 ⁇ m or less, or 0.25 ⁇ m or less. .
  • the method for measuring the average thickness of the back layer is described in 2. below. (3) explains.
  • the average particle volume of the magnetic powder contained in the magnetic recording medium of the present technology may be 2600 nm 3 or less, preferably 2000 nm 3 or less, and more preferably 1600 nm 3 or less. By having the average particle volume within the above numerical range, the electromagnetic conversion characteristics are improved. Although the magnetic powder contained in the magnetic recording medium of the present technology has such a very small average particle volume, the magnetic recording medium of the present technology has excellent thermal stability as described above. Although it is difficult to achieve both electromagnetic conversion characteristics and thermal stability, the present technology can improve both electromagnetic conversion characteristics and thermal stability.
  • the average particle volume of the magnetic powder may be, for example, 500 nm 3 or more, especially 700 nm 3 or more. The method for measuring the average particle volume of the magnetic powder is described in 2. below. (3) explains.
  • the squareness ratio in the vertical direction is preferably 65% or more, more preferably 67% or more, and even more preferably 70% or more.
  • the perpendicular orientation of the magnetic powder is sufficiently high, so that a better cNR can be obtained. Therefore, better electromagnetic conversion characteristics can be obtained.
  • the method for measuring the squareness ratio in the vertical direction is described in 2 below. (3) explains.
  • a magnetic recording medium consistent with the present technology may have, for example, at least one data band and at least two servo bands.
  • the number of data bands can be, for example, 2-10, especially 3-6, more especially 4 or 5.
  • the number of servo bands can be, for example, 3-11, especially 4-7, more especially 5 or 6.
  • These servo bands and data bands may be arranged, for example, so as to extend in the longitudinal direction of an elongated magnetic recording medium (particularly a magnetic recording tape), in particular substantially parallel.
  • the data band and the servo band may be provided on the magnetic layer.
  • a magnetic recording medium having data bands and servo bands in this way a magnetic recording tape conforming to the LTO (Linear Tape-Open) standard can be mentioned.
  • a magnetic recording medium according to the present technology may be a magnetic recording tape according to the LTO standard.
  • a magnetic recording medium consistent with the present technology may be a magnetic recording tape conforming to LTO8 or later standards (eg, LTO9, LTO10, LTO11, LTO12, etc.).
  • the width of the elongated magnetic recording medium (especially magnetic recording tape) according to the present technology is, for example, 5 mm to 30 mm, particularly 7 mm to 25 mm, more particularly 10 mm to 20 mm, and even more particularly 11 mm to It can be 19 mm.
  • the length of the elongated magnetic recording medium (especially magnetic recording tape) can be, for example, 500m to 1500m.
  • the tape width according to the LTO8 standard is 12.65 mm and the length is 960 m.
  • the magnetic recording medium 10 is, for example, a perpendicularly oriented magnetic recording medium, and as shown in FIG.
  • the surface on which the magnetic layer 13 is provided is referred to as the magnetic surface
  • the surface opposite to the magnetic surface (the surface on which the back layer 14 is provided) is referred to as the magnetic surface. ) is called the back surface.
  • the magnetic recording medium 10 has a long shape, and runs in the longitudinal direction during recording and reproduction.
  • the magnetic recording medium 10 may be configured to record signals at the shortest recording wavelength of preferably 100 nm or less, more preferably 75 nm or less, even more preferably 60 nm or less, and particularly preferably 50 nm or less. It can be used in a recording/reproducing device whose wavelength is within the above range.
  • This recording/reproducing apparatus may have a ring-type head as a recording head.
  • the recording track width is, for example, 2 ⁇ m or less.
  • the base layer 11 can function as a support for the magnetic recording medium 10, and can be, for example, a flexible elongated non-magnetic substrate, particularly a non-magnetic film.
  • the average thickness of the base layer 11 is, for example, preferably 4.5 ⁇ m or less, more preferably 4.2 ⁇ m or less, and can be 4.0 ⁇ m or less, 3.6 ⁇ m or less, further preferably 3.0 ⁇ m or less.
  • the lower limit of the average thickness of the base layer 11 may be determined, for example, from the viewpoint of the film production limit of the film or the function of the base layer 11 .
  • the base layer 11 may include, for example, at least one of polyester-based resin, polyolefin-based resin, cellulose derivative, vinyl-based resin, aromatic polyetherketone resin, and other polymer resins.
  • the base layer 11 contains two or more of the above materials, the two or more materials may be mixed, copolymerized, or laminated.
  • the polyester resin for example, PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PBN (polybutylene naphthalate), PCT (polycyclohexylene dimethylene terephthalate), PEB (polyethylene- p-oxybenzoate), and polyethylene bisphenoxycarboxylate, or a mixture of two or more.
  • the base layer 11 may be formed from PET or PEN.
  • the polyolefin resin may be, for example, one or a mixture of two or more of PE (polyethylene) and PP (polypropylene).
  • the cellulose derivative may be, for example, one or a mixture of two or more of cellulose diacetate, cellulose triacetate, CAB (cellulose acetate butyrate), and CAP (cellulose acetate propionate).
  • the vinyl resin may be, for example, one or a mixture of two or more of PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride).
  • the aromatic polyether ketone resin is, for example, one or two of PEK (polyether ketone), PEEK (polyether ether ketone), PEKK (polyether ketone ketone), and PEEKK (polyether ether ketone ketone) It may be a mixture of more than one species.
  • base layer 11 may be formed from PEEK.
  • PA polyamide, nylon
  • aromatic PA aromatic polyamide, aramid
  • PI polyimide
  • aromatic PI aromatic polyimide
  • PAI polyamideimide
  • aromatic PAI aromatic polyamideimide
  • PBO polybenzoxazole, e.g. Zylon®, polyether, polyetherester, PES (polyethersulfone), PEI (polyetherimide), PSF (polysulfone), PPS (polyphenylene sulfide), PC (polycarbonate), PAR (polyarylate), and PU (polyurethane), or a mixture of two or more thereof.
  • the magnetic layer 13 can be, for example, a perpendicular recording layer.
  • the magnetic layer 13 contains magnetic powder.
  • the magnetic layer 13 contains, in addition to magnetic powder, conductive first particles and second particles having a Mohs hardness of 7 or more.
  • the magnetic layer 13 may further contain, for example, a binder.
  • the magnetic layer 13 may further contain additives such as lubricants and antirust agents, if necessary.
  • the average thickness t m of the magnetic layer 13 is preferably 0.08 ⁇ m or less, more preferably 0.07 ⁇ m or less, and even more preferably 0.06 ⁇ m or less, 0.05 ⁇ m or less, or 0.04 ⁇ m or less.
  • the lower limit of the average thickness t m of the magnetic layer 13 is not particularly limited, it may preferably be 0.03 ⁇ m or more. The fact that the average thickness tm of the magnetic layer 13 is within the above numerical range contributes to the improvement of the electromagnetic conversion characteristics.
  • the magnetic layer 13 is preferably a vertically oriented magnetic layer.
  • perpendicular orientation means that the squareness ratio S1 measured in the longitudinal direction (running direction) of the magnetic recording medium 10 is 35% or less.
  • the magnetic layer 13 may be an in-plane oriented (longitudinal) magnetic layer. That is, the magnetic recording medium 10 may be a horizontal recording type magnetic recording medium. However, vertical orientation is more preferable in terms of high recording density.
  • Examples of magnetic particles forming the magnetic powder contained in the magnetic layer 13 include epsilon-type iron oxide ( ⁇ iron oxide), gamma hematite, magnetite, chromium dioxide, cobalt-coated iron oxide, hexagonal ferrite, barium ferrite (BaFe), Co ferrite, strontium ferrite, and metals may include, but are not limited to.
  • the magnetic powder may be one of these, or may be a combination of two or more.
  • the magnetic powder may include ⁇ -iron oxide magnetic powder, barium ferrite magnetic powder, cobalt ferrite magnetic powder, or strontium ferrite magnetic powder.
  • the ⁇ -iron oxide may contain Ga and/or Al.
  • the average particle size (average maximum particle size) D of the magnetic powder is preferably 22 nm or less, more preferably 8 nm or more and 22 nm or less, and even more preferably 10 nm or more and 20 nm or less.
  • the average particle size D of the magnetic powder is determined as follows. First, the magnetic recording medium 10 to be measured is processed by FIB (Focused Ion Beam) method or the like to prepare a thin piece, and the cross section of the thin piece is observed by TEM. Next, 500 ⁇ -iron oxide particles are randomly selected from the TEM photograph taken, and the maximum particle size d max of each particle is measured to determine the particle size distribution of the maximum particle size d max of the magnetic powder.
  • the “maximum particle size d max ” means the so-called maximum Feret diameter, specifically, the distance between two parallel lines drawn from all angles so as to touch the contour of the ⁇ -iron oxide particle. means the largest of Thereafter, the median diameter (50% diameter, D50) of the maximum particle size d max is determined from the particle size distribution of the maximum particle size d max , and this is defined as the average particle size (average maximum particle size) D of the magnetic powder.
  • the shape of the magnetic powder is preferably plate-like, spherical, or rectangular.
  • the shape of the magnetic powder depends on the crystal structure of the magnetic particles.
  • Plate-shaped magnetic powders include, for example, BaFe and strontium ferrite having a hexagonal plate-like shape.
  • Magnetic powders having a spherical shape include, for example, ⁇ -iron oxide.
  • Magnetic powder having a rectangular shape includes, for example, cobalt ferrite having a cubic shape.
  • the magnetic powder may preferably contain a powder of nanoparticles containing ⁇ -iron oxide (hereinafter referred to as " ⁇ -iron oxide particles").
  • ⁇ -iron oxide particles can obtain a high coercive force even when they are fine particles.
  • the ⁇ -iron oxide contained in the ⁇ -iron oxide particles is preferably crystal-oriented preferentially in the thickness direction (perpendicular direction) of the magnetic recording medium 10 .
  • the ⁇ -iron oxide particles have a spherical or nearly spherical shape, or have a cubic or nearly cubic shape. Since the ⁇ -iron oxide particles have the above-described shape, the thickness of the medium using the ⁇ -iron oxide particles as the magnetic particles is reduced compared to the case where the hexagonal plate-shaped barium ferrite particles are used as the magnetic particles. It is possible to reduce the contact area between the particles in the direction and suppress the aggregation of the particles. Therefore, it is possible to improve the dispersibility of the magnetic powder and obtain a better SNR (Signal-to-Noise Ratio).
  • ⁇ -iron oxide particles have a core-shell structure or Janus structure.
  • the ⁇ -iron oxide particles are provided with a core portion and a two-layered shell portion provided around the core portion.
  • the shell portion having a two-layer structure includes a first shell portion provided on the core portion and a second shell portion provided on the first shell portion.
  • the capture of fatty acids may be suppressed by controlling the surface activity of the magnetic powder with the core-shell structure.
  • the core portion contains ⁇ -iron oxide.
  • the ⁇ -iron oxide contained in the core portion preferably has an ⁇ -Fe 2 O 3 crystal as a main phase, more preferably a single-phase ⁇ -Fe 2 O 3 .
  • the first shell part covers at least part of the periphery of the core part.
  • the first shell portion may partially cover the periphery of the core portion, or may cover the entire periphery of the core portion. From the viewpoint of ensuring sufficient exchange coupling between the core portion and the first shell portion and improving the magnetic properties, it is preferable that the entire surface of the core portion is covered.
  • the first shell part is a so-called soft magnetic layer, and may contain a soft magnetic material such as ⁇ -Fe, Ni-Fe alloy or Fe-Si-Al alloy.
  • ⁇ -Fe may be obtained by reducing ⁇ -iron oxide contained in the core.
  • the second shell portion is an oxide film as an antioxidant layer.
  • the second shell portion may comprise alpha iron oxide, aluminum oxide, or silicon oxide.
  • Alpha-iron oxide can include, for example, at least one iron oxide of Fe 3 O 4 , Fe 2 O 3 , and FeO.
  • the ⁇ -iron oxide may be obtained by oxidizing the ⁇ -Fe contained in the first shell.
  • the ⁇ -iron oxide particles have the first shell portion as described above, thermal stability can be ensured.
  • the coercive force Hc of the particles (core-shell type particles) as a whole can be adjusted to a coercive force Hc suitable for recording.
  • the ⁇ -iron oxide particles have the second shell portion as described above, the ⁇ -iron oxide particles are exposed to the air during and before the manufacturing process of the magnetic recording medium 10, and the particle surfaces are rusted. and the like can be suppressed from deteriorating the properties of the ⁇ -iron oxide particles. Therefore, deterioration of the characteristics of the magnetic recording medium 10 can be suppressed.
  • the ⁇ -iron oxide particles may have a shell portion with a single-layer structure.
  • the shell portion has the same configuration as the first shell portion.
  • the ⁇ -iron oxide particles may contain an additive instead of a core-shell structure, or may have a core-shell structure and contain an additive. In these cases, some of the Fe in the ⁇ -iron oxide particles is replaced by the additive. Since the ⁇ -iron oxide particles contain an additive, the coercive force Hc of the entire ⁇ -iron oxide particles can be adjusted to a coercive force Hc suitable for recording, so that the ease of recording can be improved.
  • the additive is a metal element other than iron, preferably a trivalent metal element, more preferably one or more selected from the group consisting of aluminum (Al), gallium (Ga), and indium (In).
  • the ⁇ -iron oxide containing the additive is an ⁇ -Fe 2-x M x O 3 crystal (here, M is a metal element other than iron, preferably a trivalent metal element, more preferably Al , Ga, and In, where x satisfies, for example, 0 ⁇ x ⁇ 1.
  • the magnetic powder may be barium ferrite (BaFe) magnetic powder.
  • the barium ferrite magnetic powder contains iron oxide magnetic particles having barium ferrite as the main phase (hereinafter referred to as "barium ferrite particles").
  • Barium ferrite magnetic powder has high data recording reliability, for example, its coercive force does not decrease even in a hot and humid environment. From this point of view, barium ferrite magnetic powder is preferable as the magnetic powder.
  • the average particle size of the barium ferrite magnetic powder can be 50 nm or less, more preferably 10 nm or more and 40 nm or less, and even more preferably 12 nm or more and 25 nm or less.
  • the average thickness t m [nm] of the magnetic layer 13 is preferably 0.08 ⁇ m or less, more preferably 0.07 ⁇ m or less, and even more preferably 0.06 ⁇ m or less.
  • the coercive force Hc measured in the thickness direction (perpendicular direction) of the magnetic recording medium 10 is preferably 160 kA/m or more and 280 kA/m or less, more preferably 165 kA/m or more and 275 kA/m or less, and even more preferably 170 kA/m. m or more and 270 kA/m or less.
  • the magnetic powder can be cobalt ferrite magnetic powder.
  • Cobalt ferrite magnetic powder contains iron oxide magnetic particles having cobalt ferrite as a main phase (hereinafter referred to as "cobalt ferrite magnetic particles").
  • Cobalt ferrite magnetic particles preferably have uniaxial anisotropy.
  • Cobalt ferrite magnetic particles for example, have a cubic or nearly cubic shape.
  • Cobalt ferrite is cobalt ferrite containing Co.
  • Cobalt ferrite may further contain, in addition to Co, one or more selected from the group consisting of Ni, Mn, Al, Cu, and Zn.
  • Cobalt ferrite has, for example, an average composition represented by the following formula (1).
  • CoxMyFe2Oz ( 1 ) M is, for example, one or more metals selected from the group consisting of Ni, Mn, Al, Cu, and Zn.
  • x is 0.4 ⁇ x ⁇ 1.0
  • y is a value within the range of 0 ⁇ y ⁇ 0.3, provided that x and y satisfy the relationship (x+y) ⁇ 1.0, z is 3 ⁇ z ⁇ It is a value within the range of 4.
  • a part of Fe may be substituted with other metal elements.
  • the average particle size of the cobalt ferrite magnetic powder is preferably 25 nm or less, more preferably 23 nm or less.
  • the coercive force Hc of the cobalt ferrite magnetic powder is preferably 2500 Oe or more, more preferably 2600 Oe or more and 3500 Oe or less.
  • the magnetic powder may include powder of nanoparticles containing hexagonal ferrite (hereinafter referred to as "hexagonal ferrite particles").
  • Hexagonal ferrite particles have, for example, a hexagonal plate shape or a substantially hexagonal plate shape.
  • the hexagonal ferrite may preferably contain at least one of Ba, Sr, Pb, and Ca, more preferably at least one of Ba and Sr.
  • the hexagonal ferrite may in particular be barium ferrite or strontium ferrite, for example.
  • Barium ferrite may further contain at least one of Sr, Pb, and Ca in addition to Ba.
  • the strontium ferrite may further contain at least one of Ba, Pb, and Ca in addition to Sr. More specifically, hexagonal ferrite can have an average composition represented by the general formula MFe 12 O 19 .
  • M is, for example, at least one of Ba, Sr, Pb and Ca, preferably at least one of Ba and Sr.
  • M may be a combination of Ba and one or more metals selected from the group consisting of Sr, Pb and Ca.
  • M may be a combination of Sr and one or more metals selected from the group consisting of Ba, Pb and Ca. Part of Fe in the above general formula may be substituted with another metal element.
  • the average particle size of the magnetic powder may be preferably 50 nm or less, more preferably 10 nm or more and 40 nm or less, and even more preferably 15 nm or more and 30 nm or less.
  • the first particles have conductivity.
  • fine particles containing carbon as a main component can be used, and for example, carbon particles can be preferably used, and examples of such carbon particles include carbon black.
  • carbon black for example, Asahi #15, #15HS manufactured by Asahi Carbon Co., Ltd. can be used.
  • hybrid carbon in which carbon is attached to the surface of silica particles may be used.
  • the second particles may have a Mohs hardness of 7 or more, preferably 7.5 or more, more preferably 8 or more, and even more preferably 8.5 or more, from the viewpoint of suppressing deformation due to contact with the magnetic head. From the viewpoint of suppressing head wear, the Mohs hardness of the second particles may preferably be 9.5 or less.
  • the second particles may preferably be inorganic particles, such as ⁇ -Al 2 O 3 ( ⁇ -alumina), ⁇ -Al 2 O 3 ( ⁇ -alumina), ⁇ -Al having an ⁇ conversion rate of 90% or more.
  • 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, and magnetic iron oxide raw materials are dehydrated and annealed to obtain acicular ⁇ -iron oxide, optionally surface-treated with aluminum and/or silica. , diamond powder, and the like.
  • the second particles are preferably alumina particles such as ⁇ -Al 2 O 3 ( ⁇ -alumina), ⁇ -Al 2 O 3 ( ⁇ -alumina), ⁇ -Al 2 O 3 ( ⁇ -alumina), and silicon carbide. be done. These second particles may have any shape such as acicular, spherical, or dice-like, but those having corners in a part of the shape are preferred because they have high abrilliance.
  • the second particles form protrusions on the magnetic layer side surface.
  • the average height (H 2 ) of protrusions formed by the second particles is 7 nm or less, preferably 6.5 nm or less, more preferably 6.0 nm or less, even more preferably 5.5 nm or less, and even more preferably 5. It can be 3 nm or less. Since the magnetic recording medium has an average height (H 2 ) of the protrusions formed by the second particles within the above numerical range, the spacing between the magnetic head and the magnetic recording medium can be reduced and It contributes to making it possible to maintain an appropriate polishing force for the magnetic head with little increase in friction due to running.
  • the lower limit of the average height (H 2 ) of the protrusions formed by the second particles is not particularly limited. Preferably, it may be 3.0 nm or more.
  • the magnetic layer 13 contains a lubricant.
  • the lubricant may be one or more selected from fatty acids and fatty acid esters, and preferably contains both fatty acids and fatty acid esters.
  • the fatty acid may preferably be a compound represented by the following general formula (1) or (2).
  • the fatty acid may contain one or both of a compound represented by the following general formula (1) and a compound represented by general formula (2).
  • the fatty acid ester may be preferably a compound represented by the following general formula (3) or (4).
  • the fatty acid ester may contain one or both of a compound represented by the following general formula (3) and a compound represented by general formula (4).
  • the lubricant is one or both of the compound represented by the general formula (1) and the compound represented by the general formula (2), and/or the compound represented by the general formula (3) and the compound represented by the general formula (4) By containing either one or both of the compounds shown, damage to the magnetic head can be prevented and reduction in output can be suppressed.
  • fatty acids and fatty acid esters are as follows.
  • Fatty acids include capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid and the like.
  • Fatty acid esters include butyl caprate, octyl caprylate, ethyl laurate, butyl laurate, octyl laurate, ethyl myristate, butyl myristate, octyl myristate, 2-ethylhexyl myristate, ethyl palmitate, and palmitic acid.
  • the binder it is preferable to use a resin having a structure obtained by imparting a cross-linking reaction to a polyurethane-based resin or a vinyl chloride-based resin.
  • the binder is not limited to these, and other resins may be blended as appropriate depending on the physical properties required for the magnetic recording medium 10 .
  • the resin to be blended is not particularly limited as long as it is a resin commonly used in the coating type magnetic recording medium 10 .
  • binder examples include polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic acid ester-acrylonitrile copolymer.
  • acrylate-vinyl chloride-vinylidene chloride copolymer acrylate-vinylidene chloride copolymer, methacrylate-vinylidene chloride copolymer, methacrylate-vinyl chloride copolymer, methacrylate-ethylene copolymer
  • Polymer polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, acrylonitrile-butadiene copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitro cellulose), styrene-butadiene copolymers, polyester resins, amino resins, and synthetic rubbers.
  • Thermosetting resins or reactive resins may be used as the binder, and examples thereof include phenol resins, epoxy resins, urea resins, melamine resins, alkyd resins, silicone resins, polyamine resins, and urea formaldehyde resin.
  • polar functional groups such as —SO 3 M, —OSO 3 M, —COOM, and P ⁇ O(OM) 2 are introduced into each of the binders described above for the purpose of improving the dispersibility of the magnetic powder.
  • M is a hydrogen atom or an alkali metal such as lithium, potassium, and sodium.
  • the polar functional groups include side chain types having terminal groups of -NR1R2, -NR1R2R3 + X - , and main chain types of >NR1R2 + X - .
  • R1, R2 and R3 are hydrogen atoms or hydrocarbon groups
  • X- is a halogen element ion such as fluorine, chlorine, bromine or iodine, or an inorganic or organic ion.
  • Polar functional groups also include -OH, -SH, -CN, and epoxy groups.
  • the magnetic layer 13 contains nonmagnetic reinforcing particles such as aluminum oxide ( ⁇ , ⁇ , or ⁇ alumina), chromium oxide, silicon oxide, diamond, garnet, emery, boron nitride, titanium carbide, silicon carbide, titanium carbide, and titanium oxide. (rutile-type or anatase-type titanium oxide) and the like may be further contained.
  • nonmagnetic reinforcing particles such as aluminum oxide ( ⁇ , ⁇ , or ⁇ alumina), chromium oxide, silicon oxide, diamond, garnet, emery, boron nitride, titanium carbide, silicon carbide, titanium carbide, and titanium oxide. (rutile-type or anatase-type titanium oxide) and the like may be further contained.
  • the magnetic layer 13 may contain a coating agent to cover the surface of the magnetic powder.
  • coating agents include organic acids having one or more polar groups such as carboxylic acid, phosphonic acid, and sulfonic acid, those that function as acid groups such as metal salts thereof, and coupling agents (silane, aluminum, titanium, etc.). ), carbon, metal oxides, hydroxides (aluminum, yttrium, etc.).
  • Organic acids include acetic acid, oxalic acid, citric acid, malonic acid, succinic acid, glutaric acid, adipic acid, phthalic acid, isophthalic acid, terephthalic acid, benzoic acid, toluic acid, p-hydroxybenzoic acid, naphthoic acid, and naphthalene dicarboxylic acid.
  • the non-magnetic layer (underlayer) 12 is a non-magnetic layer containing non-magnetic powder and a binder as main components.
  • the above description of the binder contained in the magnetic layer 13 also applies to the binder contained in the non-magnetic layer 12 .
  • the non-magnetic layer 12 may further contain at least one additive selected from first particles, lubricants, hardeners, rust inhibitors, and the like, if necessary.
  • the average thickness of the nonmagnetic layer 12 is preferably 1.2 ⁇ m or less, more preferably 1.0 ⁇ m or less, 0.9 ⁇ m or less, or 0.8 ⁇ m or less, or 0.7 ⁇ m or less, and even more preferably 0.6 ⁇ m or less. sell.
  • the lower limit of the average thickness of the non-magnetic layer 12 is not particularly limited, it is preferably 0.2 ⁇ m or more, more preferably 0.3 ⁇ m or more.
  • the non-magnetic powder contained in the non-magnetic layer 12 can contain, for example, at least one selected from inorganic particles and organic particles.
  • One type of non-magnetic powder may be used alone, or two or more types of non-magnetic powder may be used in combination.
  • Inorganic particles include, for example, one or a combination of two or more selected from metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. More specifically, the inorganic particles can be, for example, one or more selected from iron oxyhydroxide, hematite, titanium oxide, and carbon black.
  • Examples of the shape of the non-magnetic powder include various shapes such as acicular, spherical, cubic, and plate-like, but are not particularly limited to these.
  • the non-magnetic layer 12 may contain a coating agent to cover the surface of the non-magnetic powder.
  • Such coating agents may be the same as those contained in the magnetic layer 13 . Therefore, description of the coating is omitted.
  • the back layer 14 may contain a binder and non-magnetic powder.
  • the back layer 14 may contain various additives such as lubricants, curing agents, antistatic agents and organic acids, if necessary.
  • lubricants such as lubricants, curing agents, antistatic agents and organic acids, if necessary.
  • the average particle size of the inorganic particles contained in the back layer 14 is preferably 10 nm or more and 150 nm or less, more preferably 15 nm or more and 110 nm or less.
  • the average particle size of the inorganic particles is determined in the same manner as the average particle size D of the magnetic powder.
  • the average thickness tb of the back layer 14 is preferably 0.6 ⁇ m or less, more preferably 0.5 ⁇ m or less, and still more preferably 0.4 ⁇ m or less, 0.3 ⁇ m or less, 0.25 ⁇ m or less, or 0.2 ⁇ m or less. sell. Since the average thickness t b of the back layer 14 is within the above range, even when the average thickness (average total thickness) t T of the magnetic recording medium 10 is t T ⁇ 5.7 ⁇ m, the non-magnetic layer 12 and the base layer The average thickness of the magnetic recording medium 11 can be kept thick, so that the running stability of the magnetic recording medium 10 in the recording/reproducing apparatus can be maintained.
  • FIG. 18 is a diagram showing an example of a sample mount used for extraction rate measurement. An inverted triangle mark is marked 50 cm in the middle of the graph paper as shown in FIG. Place the graph paper parallel to the desk and fix both ends of the graph paper with double-sided tape. Attach double-sided tape so that it covers the two 1m mark lines and set the sample mount.
  • Standard Reagent The type of standard reagent varies depending on the fatty acid or fatty acid ester used. Also, the concentration is arbitrary. As an example, the case of using stearic acid as the fatty acid and butyl stearate as the fatty acid ester is shown.
  • a standard reagent for butyl stearate is prepared as follows.
  • a stearic acid standard reagent (manufactured by Junsei Chemical, purity 95.0%) is prepared.
  • a standard reagent of butyl stearate (manufactured by Junsei Chemical, purity 95.0%) is prepared.
  • ⁇ Standard reagent preparation> Place the prepared standard reagent in an ultrasonic cleaner for 15 minutes. After the sonication is completed, insert the filter-set syringe into the vial and pour the standard reagent directly into the syringe. Fill standard reagents into vials. Push the center shaft to push the liquid into the vial bottle. Once the vial is about the shoulder level, close the aluminum lid. The standard reagent remaining in the syringe is passed through the filter and returned to the screw vial.
  • the magnetic tape T accommodated in the cartridge 10A is unwound, and the magnetic tape T is cut into a length of about 5 m at a position 20 m in the longitudinal direction from the joint of the magnetic tape T and the leader tape LT.
  • the magnetic tape is stuck to the double-sided tape of the sample mount while alternately stacking Mag/Back in parallel. Be careful not to apply too much tension when attaching the magnetic tape.
  • the P/C surface layer is discarded, and five 1 m x 5 magnetic tapes are collected. Place a ruler along the 1m mark on the sample mount, and cut 1m of the magnetic tape with a cutter.
  • A. 5 minute extraction Weigh 60 ml hexane into a 100 ml graduated cylinder. Set the stopwatch for 5 minutes. A 120 ml screw tube containing a sample is placed in an automatic shaker set at 25° C., and the aluminum lid is left open. Put 60 ml of weighed hexane into a 120 ml round-bottomed flask, cover with an aluminum lid, turn on the power of the stopwatch and the automatic shaker at the same time to start shaking (set the rotation speed of the automatic shaker to 300 rpm). ). After 5 minutes from the start of shaking, 50 ml of the sample is weighed and transferred to a 100 ml graduated cylinder. Transfer the sample in the graduated cylinder to the eggplant flask.
  • hexane is removed from the sample in the 110 ml screw tube using an evaporator in the same manner as the 5 minute extraction. After that, add 5 ml of a mixed solvent of acetonitrile and ultrapure water (if the concentration is too high and the HPLC peak area is shaken off, use 10 ml) to the sample in the eggplant flask. Make a substitution and take a measurement.
  • the height of the projection formed by the second particles was determined by shape analysis using an atomic force microscope (hereinafter referred to as AFM) and field emission scanning electron microscope (hereinafter FE) for the same portion of the measurement sample.
  • AFM atomic force microscope
  • FE field emission scanning electron microscope
  • -SEM from the FE-SEM image captured by image analysis using the brightness difference due to the difference in the secondary electron emission amount of each of the first particle and the second particle. be done.
  • the AFM makes it possible to measure the height of the protrusions
  • the FE-SEM makes it possible to identify whether each protrusion is formed by the first particle or the second particle.
  • the image obtained by the AFM for the same location and the image obtained by the FE-SEM for the certain region are superimposed to obtain a composite image, and from the obtained composite image, the particles forming each protrusion (whether it is a first particle or a second particle) can be associated with the height of each protrusion.
  • a method for measuring the height of protrusions using AFM, a method for identifying the type of particles forming protrusions using FE-SEM, and a method for associating the height of protrusions with the types of particles forming protrusions are described below.
  • the height of the projections formed by the second particles is obtained as follows. First, from the magnetic recording medium 10 in the user data area (24 m or more from the leader pin) in the LTO cartridge, a size that fits on the sample table for SEM observation is cut out to prepare a measurement sample. Next, the surface of the measurement sample is marked, avoiding the central portion of the measurement sample. Examples of the marking method include a method of forming linear or point-like depressions on the magnetic recording medium 10 with a manipulator, a nine-denter, or the like, and a method of forming protrusions on the magnetic recording medium 10 with silver paste or the like. .
  • the tip of the probe may become dirty and an accurate shape image may not be obtained. is preferred.
  • the shape of the marking portion on the surface of the measurement sample is analyzed by AFM. Since the marked portion is recessed, the measurement is performed with an AFM at a viewing angle of 5 ⁇ m ⁇ 5 ⁇ m so that the marked portion is positioned as close to the edge of the field of view as possible. Protrusions around the marking portion shall not be measured. Next, measurement is performed at a viewing angle of 10 ⁇ m ⁇ 10 ⁇ m to determine a mark portion, and a portion without marking is measured at a viewing angle of 5 ⁇ m ⁇ 5 ⁇ m in alignment with the mark portion.
  • the measurement conditions for the shape analysis are as described below.
  • the second particles if 20 or more particles can be identified from one measurement sample in one field of view of AFM, one field of view is measured by AFM.
  • the second particles if less than 20 particles can be identified in one field of view of the AFM, multiple (eg, 3-5) fields of view are measured from one measurement sample.
  • 20 points identified as particles are secured by binarization processing, the 20 measured values by AFM are averaged, and the obtained average value is used as the height of the projection.
  • FIG. 7 is an example of an image showing an example of a surface shape captured by AFM.
  • FIG. 8 is a diagram showing an example of a projection analysis result by AFM.
  • FIG. 9 is a diagram showing an example of height distribution of protrusions. Data such as the number of protrusions formed and the height of protrusions formed by the particles can be obtained from the obtained information.
  • FIG. 10A is an example of an FE-SEM image. From the obtained FE-SEM image, it is possible to identify the type of particles forming the protrusions by using the luminance difference due to the difference in the amount of secondary electron emission between the first particles and the second particles. Image processing for the identification will be described later. Also, the position of the protrusion formed by each of the first particles and the second particles in the FE-SEM image is identified.
  • the obtained FE-SEM image (Fig. A in Fig. 10) is binarized using the image processing software Image J under each of the two processing conditions described below.
  • Information on the number of projections formed by each of the first particles and the second particles, the average area per projection, the total area of the projections, and the diameter of the projections (Feret diameter) from the image obtained by the binarization process. is obtained.
  • the second particles with high brightness (white areas in Figure A in FIG. 10) and the first particles with low brightness (black areas in Figure A in FIG. 10) are subjected to the following conditions. to change
  • B diagram in FIG. 10 is a second particle (alumina particle) formed by binarizing the FE-SEM image of A diagram in FIG. 10 under the binarization processing conditions of the second particle (alumina particle). It is an image showing the positional distribution of protrusions. The following information about the second particles was obtained from the obtained image.
  • C diagram in FIG. 10 is formed by the first particles (carbon black particles) obtained by binarizing the FE-SEM image of A diagram in FIG. 10 under the binarization processing conditions of the first particles (carbon black particles).
  • 10 is an image showing the positional distribution of the projections formed. The following information regarding the first particles was obtained from the obtained image.
  • FIG. 11 is a composite image in which the AFM image ( Figure B) and the FE-SEM image ( Figure A) are superimposed so that the positions of the corresponding protrusions match.
  • FIG. 11 the positions of the protrusions formed by the first particles P1 and the protrusions formed by the second particles P2, which are present in the FE-SEM image (Fig.
  • each position is marked differently so that the positions of the protrusions can be distinguished from each other.
  • the position of the protrusion formed by the first particle (carbon black particle) P1 and the second particle (alumina particle) determined by the binarization process, which are present in the AFM image (Fig. B) before image synthesis. ) are marked differently at each location so that they can be distinguished from the location of the protrusion formed by P2. From the composite image in which the AFM image (Fig. B) and the FE-SEM image (Fig. A) are superimposed so that the positions of the corresponding projections are aligned, each projection is the first particle P1 or the second particle P2. It is determined from which particles it is formed.
  • the marked portion was measured with an AFM at a viewing angle of 10 ⁇ m ⁇ 10 ⁇ m, and then the portion without markings was measured at a viewing angle of 5 ⁇ m ⁇ 5 ⁇ m. does not exist in
  • FIG. 12 is an enlarged view of a composite image obtained by superimposing an AFM image and an FE-SEM image.
  • FIG. 13 is a diagram showing the analysis results (projection height measurement results) by AFM for line 1 (Line 1) set at an arbitrary position in FIG. As shown in FIG. 13, the height of the protrusions formed by the second particles (alumina particles) present on line 1 can be identified. In this way, the height of the protrusion is specified from the combined image and the AFM analysis result.
  • the average height of the protrusions formed by the second particles is determined.
  • the average height of the protrusions can be obtained, for example, from the cumulative frequency distribution of protrusions formed by the second particles.
  • FIG. 14 is a diagram showing a cumulative frequency distribution of heights of protrusions formed by second particles (alumina particles).
  • A indicates frequency and B indicates cumulative %.
  • FIG. 14 shows that the average height of protrusions formed by the second particles (alumina particles) is 5.1 nm.
  • a so-called full-volume test (full-length full-surface running test) is performed by recording and reproducing data on the entire surface of the magnetic tape. After that, the magnetic head of the drive is observed with an optical microscope to confirm whether or not the constituent material of the magnetic layer adheres to the magnetic head. Next, the adherence of the constituent material of the magnetic layer to the magnetic head after running over the entire length is evaluated according to the following three-stage criteria.
  • [standard] Good Adhesion of the constituent material of the magnetic layer to the head is not observed.
  • ⁇ Adhesion of the constituent material of the magnetic layer was observed only on the end portion where the tape edge runs on the tape running surface of the head.
  • x Adhesion of the constituent material of the magnetic layer was observed anywhere on the tape running surface of the head. If the evaluation result is " ⁇ " or " ⁇ ”, there is no problem with the reliability of the magnetic tape. If the evaluation result is "x”, head clogging occurs for a short time, and the total capacity of the cartridge becomes insufficient.
  • Output degradation due to magnetic head damage is evaluated according to the following procedure. (1) Measure the drive output (2T, 8T) and head resistance before evaluation. (2) Start the test under the ambient environment. Full-length recording on the entire surface is performed with one roll, and when the recording is completed, the cartridge is replaced with a new one. (3) Measure the drive output and the head resistance every 25 windings to confirm the output change and the head resistance change. Based on the drive output before evaluation, the degree of deterioration (dB) is confirmed. (4) Repeat the above operation (3) up to 50 rolls. Next, drive output deterioration after running 50 rolls is evaluated according to the following four-stage criteria.
  • the upper limit of the average thickness (average total thickness) tT of the magnetic tape T is preferably 5.7 ⁇ m or less, 5.2 ⁇ m or less, more preferably 5.0 ⁇ m or less, even more preferably 4.6 ⁇ m or less, and particularly preferably It is 4.4 ⁇ m or less.
  • the average thickness t T of the magnetic tape T is 5.2 ⁇ m or less, the recording capacity that can be recorded in one data cartridge can be increased compared to general magnetic tapes.
  • the lower limit of the average thickness tT of the magnetic tape T is not particularly limited, it is, for example, 3.5 ⁇ m or more.
  • the average thickness tT of the magnetic tape T is obtained as follows. First, the magnetic tape T accommodated in the cartridge 10A is unwound, and a sample is prepared by cutting the magnetic tape T into a length of 250 mm at a position 30 m in the longitudinal direction from the joint between the magnetic tape T and the leader tape LT. Next, using a laser hologram (LGH-110C) manufactured by Mitutoyo as a measuring device, the thickness of the sample is measured at five positions, and the measured values are simply averaged (arithmetic average) to obtain an average thickness t T [ ⁇ m] is calculated. The five measurement positions are randomly selected from the samples so that they are different positions in the longitudinal direction of the magnetic tape T. As shown in FIG.
  • the average thickness of the non-magnetic layer 12 is obtained as follows. First, the magnetic tape T accommodated in the cartridge 10A is unwound, and the magnetic tape T is stretched to a length of 250 mm at three positions of 10 m, 30 m, and 50 m in the longitudinal direction from the joint of the magnetic tape T and the leader tape LT. 3 samples are prepared. Subsequently, 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 protective films as a pretreatment for observing a cross-sectional TEM image, which will be described later.
  • the carbon layer is formed on the magnetic layer 13 side surface and the back layer 14 side surface of the magnetic tape T by vapor deposition, and the tungsten layer is further formed on the magnetic layer 13 side surface by vapor deposition or sputtering. be.
  • the thinning is performed along the longitudinal direction of the magnetic tape T. As shown in FIG. That is, by the thinning, a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic tape T is formed.
  • TEM transmission electron microscope
  • Apparatus TEM (H9000NAR manufactured by Hitachi, Ltd.) Accelerating voltage: 300 kV Magnification: 100,000 times
  • the thickness of the non-magnetic layer 12 was measured at at least 10 positions in the longitudinal direction of the magnetic tape T, and the measured values were simply averaged ( Arithmetic mean) to obtain the average thickness ( ⁇ m) of the non-magnetic layer 12 .
  • the average thickness of the base layer 11 is obtained as follows. First, the magnetic tape T accommodated in the magnetic recording cartridge 10A is unwound, and the magnetic tape T is cut into a length of 250 mm at a position 30 m in the longitudinal direction from the connection portion between the magnetic tape T and the leader tape LT to prepare a sample. do.
  • the term “longitudinal direction” in the case of “longitudinal direction from the connection portion between the magnetic tape T and the leader tape LT” means the direction from one end on the side of the leader tape LT to the other end on the opposite side. do.
  • the layers of the sample other than the base layer 11 are removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid.
  • a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid.
  • the thickness of the sample (base layer 11) is measured at five positions, and the measured values are simply averaged (arithmetic average) Then, the average thickness of the base layer 11 is calculated.
  • the five measurement positions are randomly selected from the samples so that they are different positions in the longitudinal direction of the magnetic tape T. As shown in FIG.
  • the upper limit of the average thickness of the back layer 14 is preferably 0.6 ⁇ m or less. If the upper limit of the average thickness of the back layer 14 is 0.6 ⁇ m or less, the thickness of the nonmagnetic layer (underlayer) 12 and the base layer 11 can be increased even when the average thickness of the magnetic tape T is 5.6 ⁇ m or less. Therefore, the running stability of the magnetic tape T in the recording/reproducing apparatus can be maintained.
  • the lower limit of the average thickness of the back layer 14 is not particularly limited, it is, for example, 0.2 ⁇ m or more.
  • the average thickness tb of the back layer 14 is obtained as follows. First, the average thickness (average total thickness) tT of the magnetic tape T is measured. The method for measuring the average thickness t T (average total thickness) is as described in "Average Thickness of Magnetic Tape" below. Subsequently, the magnetic tape T accommodated in the cartridge 10A is unwound, and a sample is prepared by cutting the magnetic tape T into a length of 250 mm at a position 30 m in the longitudinal direction from the joint between the magnetic tape T and the leader tape LT. Next, the back layer 14 of the sample is removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. [ ⁇ m] is calculated.
  • MEK methyl ethyl ketone
  • the average thickness t b [ ⁇ m] of the back layer 14 is obtained from the following formula.
  • the average thickness tm of the magnetic layer 13 is obtained as follows. First, the magnetic tape T accommodated in the cartridge 10A is unwound, and the magnetic tape T is stretched to a length of 250 mm at three positions of 10 m, 30 m, and 50 m in the longitudinal direction from the joint of the magnetic tape T and the leader tape LT. 3 samples are prepared. Subsequently, 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 protective films as a pretreatment for observing a cross-sectional TEM image, which will be described later.
  • the carbon layer is formed on the magnetic layer 13 side surface and the back layer 14 side surface of the magnetic tape T by vapor deposition, and the tungsten layer is further formed on the magnetic layer 13 side surface by vapor deposition or sputtering. be.
  • the thinning is performed along the longitudinal direction of the magnetic tape T. As shown in FIG. That is, by the thinning, a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic tape T is formed.
  • the thickness of the magnetic layer 13 is measured at 10 points on each sliced sample.
  • the 10 measurement positions for each thinned sample are randomly selected from the sample so that they are different positions in the longitudinal direction of the magnetic tape T.
  • the average value obtained by simply averaging (arithmetic mean) the measured values of each obtained thinned sample is defined as the average thickness t m [nm] of the magnetic layer 13. do.
  • the average particle size and average aspect ratio of the magnetic powder are obtained as follows. First, the magnetic tape T accommodated in the cartridge 10A is unwound, and the magnetic tape T is cut out at a position 30 m in the longitudinal direction from the joint between the magnetic tape T and the leader tape LT. Subsequently, the magnetic tape T to be measured 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 protective films as a pretreatment for observing a cross-sectional TEM image, which will be described later.
  • the carbon layer is formed on the magnetic layer 13 side surface and the back layer 14 side surface of the magnetic tape T by vapor deposition, and the tungsten layer is further formed on the magnetic layer 13 side surface by vapor deposition or sputtering.
  • the thinning is performed along the length direction of the magnetic tape T (longitudinal direction). That is, by the thinning, a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic tape T is formed.
  • the above-mentioned cross section of the obtained thin sample was examined with an acceleration voltage of 200 kV and a total magnification of 500,000 times.
  • a cross-sectional observation is performed so as to include , and a TEM photograph is taken.
  • the number of TEM photographs is prepared so that 50 particles can be extracted from which the plate diameter DB and plate thickness DA (see FIG. 15) shown below can be measured.
  • the particle size of the hexagonal ferrite (hereinafter referred to as "particle size") is defined as the shape of the particles observed in the above TEM photograph, as shown in FIG. , the thickness or height is smaller than the major axis of the plate surface or bottom surface.), the major axis of the plate surface or bottom surface is taken as the value of the plate diameter DB. The thickness or height of the particles observed in the above TEM photograph is taken as the plate thickness DA value.
  • the major axis means the longest diagonal distance.
  • the thickness or height of the largest grain is defined as the plate thickness DA.
  • 50 particles to be extracted from the TEM photograph taken are selected based on the following criteria. Particles partly protruding outside the field of view of the TEM photograph are not measured, but particles with clear contours and present in isolation are measured. When particles overlap, if the boundary between the two particles is clear and the overall shape of the particle can be determined, each particle is measured as a single particle, but the boundary is not clear and the overall shape of the particle cannot be determined Particles that do not have a shape are not measured as the shape of the particles cannot be determined.
  • FIGS. 16 and 17 show examples of TEM photographs.
  • the particles indicated by arrows a and d are selected because the plate thickness (thickness or height of the particle) DA of the particle can be clearly identified.
  • the plate thickness DA of each of the 50 selected particles is measured.
  • the average plate thickness DA ave is obtained by simply averaging (arithmetic mean) the plate thicknesses DA thus obtained.
  • the average thickness DA ave is the average grain thickness.
  • the plate diameter DB of each magnetic powder is measured.
  • 50 particles whose tabular diameter DB of the particles can be clearly confirmed are selected from the photographed TEM photographs. For example, in FIGS.
  • the plate diameter DB of each of the 50 selected particles is measured.
  • a simple average (arithmetic mean) of the plate diameters DB obtained in this way is obtained to obtain an average plate diameter DB ave .
  • the average platelet diameter DB ave is the average particle size.
  • the average aspect ratio (DB ave /DA ave ) of the particles is obtained from the average plate thickness DA ave and the average plate diameter DB ave .
  • the average particle volume of magnetic powder is determined as follows. First, the average plate thickness DA ave and the average plate diameter DB ave are obtained as described in the method of calculating the average particle size of the magnetic powder. Next, the average particle volume V of the magnetic powder is obtained from the following formula.
  • the squareness ratio Rs2 in the perpendicular direction (thickness direction) of the magnetic recording medium of the present technology is preferably 65% or more, more preferably 67% or more, and even more preferably 70% or more.
  • the perpendicular orientation of the magnetic powder is sufficiently high, so that a better SNR can be obtained. Therefore, better electromagnetic conversion characteristics can be obtained. Also, the shape of the servo signal is improved, making it easier to control the drive.
  • the perpendicular orientation of the magnetic recording medium may mean that the squareness ratio Rs2 of the magnetic recording medium is within the above numerical range (for example, 65% or more).
  • the squareness ratio Rs2 in the vertical direction is obtained as follows. First, the magnetic tape T accommodated in the magnetic recording cartridge 10A is unwound, and the magnetic tape T is cut into a length of 250 mm at a position 30 m in the longitudinal direction from the connection portion between the magnetic tape T and the leader tape LT to prepare a sample. do. After punching out the sample to 6.25 mm ⁇ 64 mm, it is folded in three to prepare a measurement sample of 6.25 mm ⁇ 8 mm. Then, using the VSM, the MH hysteresis loop of the measurement sample (entire magnetic tape T) corresponding to the vertical direction (thickness direction) of the magnetic tape T is measured.
  • correction sample a 6.25 mm ⁇ 8 mm sample for background correction (hereinafter simply referred to as “correction sample”).
  • VSM the MH hysteresis loop of the correction sample (base layer 11) corresponding to the perpendicular direction of the base layer 11 (the perpendicular direction of the magnetic recording medium 10) is measured.
  • VSM -P7-15 type In the measurement of the MH hysteresis loop of the measurement sample (entire magnetic tape T) and the MH hysteresis loop of the correction sample (base layer 11), a high-sensitivity vibrating sample magnetometer "VSM -P7-15 type” is used. Measurement conditions are as follows: measurement mode: full loop, maximum magnetic field: 15 kOe, magnetic field step: 40 bits, Time constant of Lockingamp: 0.3 sec, Waiting time: 1 sec, MH average number: 20.
  • the MH hysteresis of the measurement sample was obtained.
  • Background correction is performed by subtracting the MH hysteresis loop of the correction sample (base layer 11) from the loop, and the MH hysteresis loop after background correction is obtained.
  • the measurement/analysis program attached to the "VSM-P7-15 type" is used for the calculation of this background correction.
  • a non-magnetic layer (underlayer) forming coating material is prepared by kneading and/or dispersing non-magnetic powder and a binder in a solvent.
  • magnetic powder, a binder, etc. are kneaded and/or dispersed in a solvent to prepare a coating material for forming a magnetic layer.
  • the following solvents, dispersing devices, and kneading devices can be used for example.
  • solvents used in the above paint preparation include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohol solvents such as methanol, ethanol, and propanol; , butyl acetate, propyl acetate, ethyl lactate, and ethylene glycol acetate; ether solvents such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran, and dioxane; aromatic hydrocarbons such as benzene, toluene, and xylene. and halogenated hydrocarbon solvents such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, and chlorobenzene. One of these may be used, or a mixture of two or more may be used.
  • ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl
  • a continuous twin-screw kneader for example, a continuous twin-screw kneader, a continuous twin-screw kneader capable of multistage dilution, a kneader, a pressure kneader, and a roll kneader can be used.
  • dispersing devices used for preparing the above paint include roll mills, ball mills, horizontal sand mills, vertical sand mills, spike mills, pin mills, tower mills, pearl mills (e.g. "DCP Mill” manufactured by Eirich), homogenizers, and A dispersion device such as an ultrasonic disperser can be used, but it is not particularly limited to these devices.
  • the non-magnetic layer 12 is formed by coating one main surface of the base layer 11 with a paint for forming a non-magnetic layer (underlayer) and drying it.
  • the magnetic layer 13 is formed on the non-magnetic layer 12 by coating the non-magnetic layer 12 with a coating material for forming the magnetic layer and drying it.
  • the magnetic powder is magnetically oriented in the thickness direction of the base layer 11 by, for example, a solenoid coil.
  • the magnetic powder may be magnetically oriented in the longitudinal direction (running direction) of the base layer 11 by, for example, a solenoid coil, and then magnetically oriented in the thickness direction of the base layer 11 .
  • the ratio Hc2/Hc1 between the holding force "Hc1" in the vertical direction and the holding force "Hc2" in the longitudinal direction can be reduced, and the degree of vertical orientation of the magnetic powder can be improved. be able to.
  • the back layer 14 is formed on the other main surface of the base layer 11 .
  • the magnetic recording medium 10 is obtained.
  • the ratio Hc2/Hc1 depends on, for example, the intensity of the magnetic field applied to the coating film of the magnetic layer-forming coating material, the concentration of solids in the magnetic layer-forming coating material, and the drying conditions (drying temperature and drying time) are set to desired values.
  • the strength of the magnetic field applied to the coating film is preferably two to three times the coercive force of the magnetic powder.
  • the methods for adjusting the ratio Hc2/Hc1 may be used singly or in combination of two or more.
  • the obtained magnetic recording medium 10 is rewound around the large-diameter core and hardened. Finally, after calendering the magnetic recording medium 10, it is cut into a predetermined width (for example, 1/2 inch width). As described above, the desired elongated long magnetic recording medium 10 is obtained.
  • the recording/reproducing device 30 has a configuration in which the tension applied in the longitudinal direction of the magnetic recording medium 10 can be adjusted. Further, the recording/reproducing device 30 has a configuration in which the magnetic recording cartridge 10A can be loaded. Here, for ease of explanation, the case where the recording/reproducing device 30 has a configuration in which one magnetic recording cartridge 10A can be loaded will be described. You may have the structure which can be loaded with 10A.
  • the recording/reproducing device 30 is preferably a timing servo type magnetic recording/reproducing device.
  • the magnetic recording medium of the present technology is suitable for use in a timing servo type magnetic recording/reproducing apparatus.
  • the recording/reproducing apparatus 30 is connected to information processing apparatuses such as a server 41 and a personal computer (hereinafter referred to as "PC") 42 via a network 43, and stores data supplied from these information processing apparatuses in a magnetic recording cartridge. 10A can be recorded.
  • the shortest recording wavelength of the recording/reproducing device 30 is preferably 100 nm or less, more preferably 75 nm or less, still more preferably 60 nm or less, and particularly preferably 50 nm or less.
  • the recording/reproducing device includes a spindle 31, a reel 32 on the side of the recording/reproducing device, a spindle driving device 33, a reel driving device 34, a plurality of guide rollers 35, a head unit 36, and a communication device. It has an interface (hereinafter referred to as I/F) 37 and a control device 38 .
  • I/F interface
  • the spindle 31 is configured to be mountable with the magnetic recording cartridge 10A.
  • the magnetic recording cartridge 10A complies with the LTO (Linear Tape Open) standard, and rotatably accommodates a single reel 10C around which the magnetic recording medium 10 is wound in a cartridge case 10B.
  • a V-shaped servo pattern is recorded in advance on the magnetic recording medium 10 as a servo signal.
  • the reel 32 is configured to be able to fix the leading end of the magnetic recording medium 10 pulled out from the magnetic recording cartridge 10A.
  • the present technology also provides a magnetic recording cartridge including a magnetic recording medium according to the present technology. Within the magnetic recording cartridge, the magnetic recording medium may be wound, for example, on a reel.
  • the spindle drive device 33 is a device that drives the spindle 31 to rotate.
  • the reel driving device 34 is a device that drives the reel 32 to rotate. When data is recorded or reproduced on the magnetic recording medium 10, the spindle driving device 33 and the reel driving device 34 rotate the spindle 31 and the reel 32 to drive the magnetic recording medium 10. .
  • the guide roller 35 is a roller for guiding the travel of the magnetic recording medium 10 .
  • the head unit 36 includes a plurality of recording heads for recording data signals on the magnetic recording medium 10, a plurality of reproducing heads for reproducing the data signals recorded on the magnetic recording medium 10, and a plurality of servo heads for reproducing recorded servo signals.
  • a ring-type head can be used as the recording head, but the type of recording head is not limited to this.
  • the communication I/F 37 is for communicating with information processing devices such as the server 41 and the PC 42 and is connected to the network 43 .
  • the control device 38 controls the recording/reproducing device 30 as a whole. For example, the control device 38 records a data signal supplied from the information processing device on the magnetic recording medium 10 by the head unit 36 in response to a request from the information processing device such as the server 41 and the PC 42 . Further, the control device 38 reproduces the data signal recorded on the magnetic recording medium 10 by the head unit 36 in response to a request from the information processing device such as the server 41 and the PC 42, and supplies the data signal to the information processing device.
  • the control device 38 also detects changes in the width of the magnetic recording medium 10 based on servo signals supplied from the head unit 36 . Specifically, a plurality of V-shaped servo patterns are recorded as servo signals on the magnetic recording medium 10, and the head unit 36 outputs two different servo patterns by two servo heads on the head unit 36. Simultaneously reproduced, each servo signal can be obtained. Using relative position information between the servo pattern and the head unit obtained from this servo signal, the position of the head unit 36 is controlled so as to follow the servo pattern. At the same time, distance information between the servo patterns can be obtained by comparing the two servo signal waveforms.
  • changes in the distance between the servo patterns at each measurement can be obtained.
  • changes in the width of the magnetic recording medium 10 can also be calculated.
  • the control device 38 controls the rotational driving of the spindle driving device 33 and the reel driving device 34 based on the change in the distance between the servo patterns obtained as described above or the calculated change in the width of the magnetic recording medium 10.
  • the tension in the longitudinal direction of the magnetic recording medium 10 is adjusted so that the width of the magnetic recording medium 10 becomes the prescribed width or approximately the prescribed width. Thereby, a change in the width of the magnetic recording medium 10 can be suppressed.
  • the magnetic recording cartridge 10A is mounted in the recording/reproducing device 30, the leading end of the magnetic recording medium 10 is pulled out, and the leading end of the magnetic recording medium 10 is transported to the reel 32 via a plurality of guide rollers 35 and the head unit 36. Attach to reel 32 .
  • the spindle driving device 33 and the reel driving device 34 are driven under the control of the control device 38 so that the magnetic recording medium 10 is driven from the reel 10C toward the reel 32.
  • Spindle 31 and reel 32 are rotated in the same direction.
  • the head unit 36 records information on the magnetic recording medium 10 or reproduces information recorded on the magnetic recording medium 10 .
  • the spindle 31 and the reel 32 are driven to rotate in the direction opposite to the above, so that the magnetic recording medium 10 travels from the reel 32 to the reel 10C. .
  • the head unit 36 also records information on the magnetic recording medium 10 or reproduces information recorded on the magnetic recording medium 10 .
  • the magnetic recording medium 10 may further include a barrier layer 15 provided on at least one surface of the base layer 11, as shown in FIG.
  • the barrier layer 15 is a layer for suppressing dimensional deformation of the base layer 11 according to the environment.
  • the hygroscopicity of the base layer 11 can be cited as one of the causes of the dimensional deformation, and the barrier layer 15 can reduce the rate at which moisture penetrates into the base layer 11 .
  • Barrier layer 15 comprises a metal or metal oxide. Examples of metals include Al, Cu, Co, Mg, Si, Ti, V, Cr, Mn, Fe, Ni, Zn, Ga, Ge, Y, Zr, Mo, Ru, Pd, Ag, Ba, Pt, At least one of Au and Ta can be used.
  • At least one of Al 2 O 3 , CuO, CoO, SiO 2 , Cr 2 O 3 , TiO 2 , Ta 2 O 5 and ZrO 2 can be used as the metal oxide. Any of the metal oxides can also be used. Diamond-Like Carbon (DLC) or diamond can also be used.
  • DLC Diamond-Like Carbon
  • the average thickness of the barrier layer 15 is preferably 20 nm or more and 1000 nm or less, more preferably 50 nm or more and 1000 nm or less.
  • the average thickness of the barrier layer 15 is obtained in the same manner as the average thickness tm of the magnetic layer 13 .
  • the magnification of the TEM image is appropriately adjusted according to the thickness of the barrier layer 15 .
  • the magnetic recording medium 10 may be incorporated into a library device. That is, the present technology also provides a library device including at least one magnetic recording medium 10 .
  • the library device has a configuration capable of adjusting the tension applied in the longitudinal direction of the magnetic recording medium 10, and may include a plurality of the recording/reproducing devices 30 described above.
  • the magnetic recording medium 10 may be subjected to servo signal writing processing by a servo writer.
  • the servo writer can keep the width of the magnetic recording medium 10 constant or substantially constant by adjusting the tension in the longitudinal direction of the magnetic recording medium 10 when recording servo signals.
  • the servo writer may comprise a detection device for detecting the width of the magnetic recording medium 10 .
  • the servo writer can adjust the tension in the longitudinal direction of the magnetic recording medium 10 based on the detection result of the detection device.
  • the present technology also provides a magnetic recording cartridge (also referred to as a tape cartridge) that includes a magnetic recording medium according to the present technology.
  • the magnetic recording medium may be wound, for example, on a reel.
  • the magnetic recording cartridge includes, for example, a communication unit that communicates with a recording/reproducing device, a storage unit, and information received from the recording/reproducing device via the communication unit. and a control unit that reads out information from the storage unit and transmits the information to the recording/reproducing device via the communication unit in response to a request.
  • the information may include adjustment information for adjusting the tension applied to the magnetic recording medium in the longitudinal direction.
  • FIG. 4 is an exploded perspective view showing an example of the configuration of the magnetic recording cartridge 10A.
  • the magnetic recording cartridge 10A is a magnetic recording cartridge conforming to the LTO (Linear Tape-Open) standard, and a magnetic tape (tape-shaped magnetic recording A reel 10C on which a medium T is wound, a reel lock 214 and a reel spring 215 for locking the rotation of the reel 10C, a spider 216 for releasing the locked state of the reel 10C, a lower shell 212A and an upper shell 212B.
  • LTO Linear Tape-Open
  • the reel 10C has a substantially disc shape with an opening in the center, and is composed of a reel hub 213A and a flange 213B made of a hard material such as plastic.
  • One end of the magnetic tape T is connected to a leader tape LT.
  • a leader pin 220 is provided at the tip of the leader tape LT.
  • the cartridge memory 211 is provided near one corner of the magnetic recording cartridge 10A.
  • the cartridge memory 211 faces a reader/writer (not shown) of the recording/reproducing device 80 when the magnetic recording cartridge 10A is loaded into the recording/reproducing device 80 .
  • the cartridge memory 211 communicates with the recording/reproducing device 30, more specifically, a reader/writer (not shown) in accordance with the wireless communication standard conforming to the LTO standard.
  • FIG. 5 is a block diagram showing an example of the configuration of the cartridge memory 211.
  • the cartridge memory 211 has an antenna coil (communication unit) 331 that communicates with a reader/writer (not shown) according to a prescribed communication standard, and generates and rectifies electric waves received by the antenna coil 331 using induced electromotive force.
  • a rectification/power supply circuit 332 that generates power, a clock circuit 333 that generates a clock using the same induced electromotive force from radio waves received by the antenna coil 331, and detection of the radio waves received by the antenna coil 331 and the antenna coil 331
  • a controller (control unit) 335 and a memory (storage unit) 336 for storing information.
  • the cartridge memory 211 also includes a capacitor 337 connected in parallel with the antenna coil 331, and the antenna coil 331 and the capacitor 337 constitute a resonance circuit.
  • the memory 336 stores information related to the magnetic recording cartridge 10A.
  • the memory 336 is non-volatile memory (NVM).
  • the storage capacity of memory 336 is preferably about 32 KB or greater. For example, if the magnetic recording cartridge 10A conforms to the next-generation LTO format standard, the memory 336 has a storage capacity of approximately 32 KB.
  • the memory 336 has a first storage area 336A and a second storage area 336B.
  • the first storage area 336A corresponds to the storage area of an LTO standard cartridge memory prior to LTO8 (hereinafter referred to as "conventional cartridge memory"), and is used to store information conforming to the LTO standard prior to LTO8. area.
  • the information conforming to the LTO standard prior to LTO8 includes, for example, manufacturing information (for example, the unique number of the magnetic recording cartridge 10A, etc.), usage history (for example, the number of tape withdrawals (Thread Count), etc.), and the like.
  • the second storage area 336B corresponds to an extended storage area for the storage area of the conventional cartridge memory.
  • the second storage area 336B is an area for storing additional information.
  • the additional information means information related to the magnetic recording cartridge 10A, which is not defined in the LTO standard prior to LTO8.
  • Examples of the additional information include tension adjustment information, management ledger data, index information, thumbnail information of moving images stored on the magnetic tape T, and the like, but are not limited to these data.
  • the tension adjustment information includes the distance between adjacent servo bands (distance between servo patterns recorded on adjacent servo bands) during data recording on the magnetic tape T.
  • FIG. The distance between adjacent servo bands is an example of width-related information related to the width of the magnetic tape T.
  • FIG. The details of the distance between servo bands will be described later.
  • the information stored in the first storage area 336A may be called "first information”
  • the information stored in the second storage area 336B may be called "second information”.
  • the memory 336 may have multiple banks. In this case, part of the plurality of banks may constitute the first storage area 336A, and the remaining banks may constitute the second storage area 336B. Specifically, for example, if the magnetic recording cartridge 10A conforms to the next-generation LTO format standard, the memory 336 has two banks each having a storage capacity of approximately 16 KB. One of the banks may constitute the first memory area 336A, and the other bank may constitute the second memory area 336B.
  • the antenna coil 331 induces an induced voltage by electromagnetic induction.
  • the controller 335 communicates with the recording/reproducing device 80 via the antenna coil 331 according to a prescribed communication standard. Specifically, for example, mutual authentication, command transmission/reception, or data exchange is performed.
  • the controller 335 stores information received from the recording/reproducing device 80 via the antenna coil 331 in the memory 336 .
  • the controller 335 reads information from the memory 336 in response to a request from the recording/reproducing device 80 and transmits the information to the recording/reproducing device 80 via the antenna coil 331 .
  • the magnetic recording cartridge of the present technology may be a two-reel type cartridge. That is, the magnetic recording cartridge of the present technology may have one or more (eg, two) reels on which the magnetic tape is wound.
  • An example magnetic recording cartridge of the present technology having two reels is described below with reference to FIG.
  • FIG. 6 is an exploded perspective view showing an example of the configuration of a two-reel type cartridge 421.
  • the cartridge 421 includes an upper half 402 made of synthetic resin, a transparent window member 423 fitted and fixed in a window portion 402 a opened in the upper surface of the upper half 402 , and a reel 406 fixed inside the upper half 402 .
  • a wound magnetic tape MT1 a front lid 409 that closes a front opening formed by combining the upper half 402 and the lower half 405, and a back lid 409A that protects the magnetic tape MT1 exposed at the front opening.
  • the reel 406 has a lower flange 406b having a cylindrical hub portion 406a in the center on which the magnetic tape MT1 is wound, an upper flange 406c having approximately the same size as the lower flange 406b, and a flange between the hub portion 406a and the upper flange 406c. and a reel plate 411 sandwiched therebetween.
  • Reel 407 has the same configuration as reel 406 .
  • the window member 423 is provided with mounting holes 423a at positions corresponding to the reels 406 and 407 for mounting reel holders 422, which are reel holding means for preventing the reels from floating.
  • the magnetic tape MT1 is the same as the magnetic tape T in the first embodiment.
  • the present technology can also employ the following configuration.
  • the magnetic layer contains first particles having conductivity and second particles having a Mohs hardness of 7 or more, protrusions are formed on the surface of the magnetic layer by the first particles and the second particles;
  • Fatty acid extraction rate (%) [5-minute fatty acid extraction amount (mg/m 2 )/total fatty acid extraction amount (mg/m 2 )] ⁇ 100
  • the magnetic recording medium according to [10], wherein the non-magnetic layer has an average thickness of 1.2 ⁇ m or less.
  • the average height of protrusions formed by the second particles (referred to as AFM_protrusion average height in Table 1), the extraction rate of fatty acids, the amount of fatty acids extracted in 5 minutes, the total amount of fatty acids extracted, the fatty acids Ester extraction rate, 5-minute extraction amount of fatty acid ester, total extraction amount of fatty acid ester, average thickness (average total thickness) t T of magnetic tape, average thickness t m of magnetic layer, average thickness of non-magnetic layer (underlayer)
  • the thickness, the average thickness of the base layer, the average thickness of the back layer, the deposits, and the deterioration of the output were determined by the measuring method described in the above embodiment.
  • Example 1 (Preparation step of coating material for magnetic layer formation) A coating material for forming a magnetic layer was prepared as follows. First, a first composition having the following formulation was kneaded with an extruder. Next, the kneaded first composition and the second composition having the following composition were added to a stirring tank equipped with a disper and premixed. Subsequently, sand mill mixing was carried out and filter treatment was carried out to prepare a coating material for forming a magnetic layer.
  • Aluminum oxide powder 7.5 parts by mass ( ⁇ -Al 2 O 3 , average particle size 50 nm, manufactured by Sumitomo Chemical Co., Ltd., trade name: HIT100, Mohs hardness: 9)
  • Carbon black 2.0 parts by mass (average particle size 70 nm, manufactured by Tokai Carbon Co., Ltd., trade name: SEAST TA)
  • Vinyl chloride resin 1.6 parts by mass (as 30% by mass resin in cyclohexanone solution)
  • n-butyl stearate 2 parts by mass methyl ethyl ketone: 121.3 parts by mass toluene: 121.3 parts by mass cyclohexanone: 60.7 parts by mass
  • the magnetic layer P/B ratio means the magnetic powder/adhesive (binder) ratio and was 5.0.
  • the P/B ratio in each example is shown in Table 1 below.
  • a base layer-forming coating material was prepared as follows. First, a third composition having the following formulation was kneaded with an extruder. Next, the kneaded third composition and the fourth composition excluding stearic acid and butyl stearate having the following composition were added to a stirring tank equipped with a disper and premixed. Subsequently, sand mill mixing was further performed, stearic acid and butyl stearate were added, and filter treatment was performed to prepare a base layer forming coating material.
  • polyisocyanate (trade name: Coronate L, manufactured by Tosoh Corporation): 2 parts by mass and stearic acid: 2 parts by mass are added as curing agents to the base layer-forming coating material prepared as described above. bottom.
  • a coating material for forming a back layer was prepared as follows. The following raw materials were mixed in a stirring tank equipped with a disper and subjected to filter treatment to prepare a coating material for forming a back layer.
  • Carbon black (manufactured by Asahi Corporation, trade name: #80): 100 parts by mass Polyester polyurethane: 100 parts by mass (manufactured by Nippon Polyurethane Co., Ltd., trade name: N-2304) Methyl ethyl ketone: 500 parts by mass Toluene: 400 parts by mass Cyclohexanone: 100 parts by mass Polyisocyanate (trade name: Coronate L, manufactured by Tosoh Corporation): 10 parts by mass
  • a PEN film (base film) having an elongated shape and an average thickness of 4.0 ⁇ m was prepared as a base layer of the magnetic tape.
  • the paint for forming the base layer is applied on one main surface of the PEN film and dried, so that the average thickness of the final product becomes 1.05 ⁇ m on one main surface of the PEN film.
  • a base layer was formed as follows.
  • a magnetic layer-forming paint was applied onto the underlayer and dried to form a magnetic layer on the underlayer so that the average thickness of the finished product would be 0.08 ⁇ m.
  • the other main surface of the PEN film on which the underlayer and the magnetic layer are formed is coated with a paint for forming a back layer and dried so that the average thickness of the final product is 0.50 ⁇ m. to form a back layer.
  • the PEN film on which the underlayer, magnetic layer and back layer were formed was subjected to a curing treatment. After that, calendering was performed to smooth the surface of the magnetic layer.
  • a magnetic recording cartridge was obtained by winding the 1/2 inch wide magnetic tape around a reel provided in the cartridge case.
  • a servo signal was recorded on the magnetic tape by a servo track writer.
  • the servo signal is composed of a string of magnetic patterns in a V-shape, and the magnetic patterns are arranged in the longitudinal direction at known intervals (hereinafter referred to as "intervals between known magnetic pattern strings when pre-recorded"). Two or more parallel rows were pre-recorded.
  • the resulting magnetic tape had a stearic acid extraction rate of 53%, a stearic acid extraction amount of 4.81 mg/m 2 for 5 minutes, a total stearic acid extraction amount of 9.13 mg/m 2 , and butyl stearate. was 68%, the 5-minute extraction amount of butyl stearate was 13.30 mg/m 2 , and the total amount of butyl stearate extracted was 19.42 mg/m 2 .
  • the average height (H 2 ) of the protrusions formed by ⁇ -Al 2 O 3 was 5.3 nm
  • the average thickness (average total thickness) tT of the magnetic tape was 5.56 ⁇ m
  • the magnetic layer The average thickness tm was 0.07 ⁇ m
  • the average thickness of the nonmagnetic layer (underlayer) was 1.13 ⁇ m
  • the average thickness of the base layer was 4.0 ⁇ m
  • the average thickness of the back layer was 0.36 ⁇ m. there were.
  • Example 2 A magnetic tape was obtained in the same manner as in Example 1, except that phenylphosphonic acid was used as the organic acid.
  • the extraction rate of stearic acid is 45%
  • the 5-minute extraction amount of stearic acid is 4.47 mg/m 2
  • the total extraction amount of stearic acid is 9.93 mg/m 2
  • the extraction rate of butyl stearate is 61%
  • the 5-minute extraction amount of butyl stearate was 12.06 mg/m 2
  • the total extraction amount of butyl stearate was 19.80 mg/m 2 .
  • the average height (H 2 ) of the protrusions formed by ⁇ -Al 2 O 3 was 5.4 nm. In addition, there was little adhesion to the magnetic head, and no output deterioration occurred.
  • Example 3 A magnetic tape was obtained in the same manner as in Example 1, except that the amount of stearic acid added was increased.
  • the extraction rate of stearic acid is 50%
  • the 5-minute extraction amount of stearic acid is 6.15 mg/m 2
  • the total extraction amount of stearic acid is 12.32 mg/m 2
  • the extraction rate of butyl stearate is 67%
  • the 5-minute extraction amount of butyl stearate was 13.37 mg/m 2
  • the total extraction amount of butyl stearate was 19.84 mg/m 2 .
  • the average height (H 2 ) of the protrusions formed by ⁇ -Al 2 O 3 was 5.3 nm. In addition, there was little adhesion to the magnetic head, and no output deterioration occurred.
  • Example 4 A magnetic tape was obtained in the same manner as in Example 1, except that the thickness of the magnetic layer was reduced.
  • the extraction rate of stearic acid is 59%
  • the 5-minute extraction amount of stearic acid is 5.05 mg/m 2
  • the total extraction amount of stearic acid is 8.61 mg/m 2
  • the extraction rate of butyl stearate is 69%
  • the 5-minute extraction amount of butyl stearate was 12.48 mg/m 2
  • the total extraction amount of butyl stearate was 17.96 mg/m 2 .
  • the average height (H 2 ) of the protrusions formed by ⁇ -Al 2 O 3 was 5.4 nm. In addition, there was little adhesion to the magnetic head, and no output deterioration occurred.
  • Example 5 A magnetic tape was obtained in the same manner as in Example 1, except that the amount of hardening agent in the magnetic layer was reduced.
  • the extraction rate of stearic acid is 49%
  • the 5-minute extraction amount of stearic acid is 4.54 mg/m 2
  • the total extraction amount of stearic acid is 9.29 mg/m 2
  • the extraction rate of butyl stearate is 65%
  • the 5-minute extraction amount of butyl stearate was 12.21 mg/m 2
  • the total extraction amount of butyl stearate was 18.86 mg/m 2 .
  • the average height (H 2 ) of the protrusions formed by ⁇ -Al 2 O 3 was 5.4 nm. In addition, there was little adhesion to the magnetic head, and no output deterioration occurred.
  • Example 6 A magnetic tape was obtained in the same manner as in Example 1, except that the amount of citric acid added to the base layer forming coating material was increased.
  • the extraction rate of stearic acid is 56%
  • the 5-minute extraction amount of stearic acid is 5.25 mg/m 2
  • the total extraction amount of stearic acid is 9.32 mg/m 2
  • the extraction rate of butyl stearate is 64%
  • the 5-minute extraction amount of butyl stearate was 12.41 mg/m 2
  • the total extraction amount of butyl stearate was 19.29 mg/m 2 .
  • the average height (H 2 ) of the protrusions formed by ⁇ -Al 2 O 3 was 4.8 nm. In addition, there was little adhesion to the magnetic head, and no output deterioration occurred.
  • Example 7 A magnetic tape was obtained in the same manner as in Example 1, except that the type of base film was changed to a PET film.
  • the extraction rate of stearic acid is 51%
  • the 5-minute extraction amount of stearic acid is 4.97 mg/m 2
  • the total extraction amount of stearic acid is 9.69 mg/m 2
  • the extraction rate of butyl stearate is 66%
  • the 5-minute extraction amount of butyl stearate was 13.47 mg/m 2
  • the total extraction amount of butyl stearate was 20.51 mg/m 2 .
  • the average height (H 2 ) of the protrusions formed by ⁇ -Al 2 O 3 was 4.6 nm. In addition, there was little adhesion to the magnetic head, and no output deterioration occurred.
  • Example 8 In Example 1, a magnetic tape was obtained in the same manner as in Example 1, except that the calendering temperature was lowered.
  • the extraction rate of stearic acid is 53%
  • the 5-minute extraction amount of stearic acid is 5.25 mg/m 2
  • the total extraction amount of stearic acid is 9.96 mg/m 2
  • the extraction rate of butyl stearate is 72%
  • the 5-minute extraction amount of butyl stearate was 14.72 mg/m 2
  • the total extraction amount of butyl stearate was 20.47 mg/m 2 .
  • the average height (H 2 ) of the protrusions formed by ⁇ -Al 2 O 3 was 6.0 nm. In addition, there was little adhesion to the magnetic head, and no output deterioration occurred.
  • Example 9 A magnetic tape was obtained in the same manner as in Example 1, except that the calendering temperature was increased.
  • the extraction rate of stearic acid is 51%
  • the 5-minute extraction amount of stearic acid is 4.72 mg/m 2
  • the total extraction amount of stearic acid is 9.19 mg/m 2
  • the extraction rate of butyl stearate is 71%
  • the 5-minute extraction amount of butyl stearate was 13.61 mg/m 2
  • the total extraction amount of butyl stearate was 19.29 mg/m 2 .
  • the average height (H 2 ) of the protrusions formed by ⁇ -Al 2 O 3 was 5.3 nm. In addition, there was little adhesion to the magnetic head, and no output deterioration occurred.
  • Example 10 A magnetic tape was obtained in the same manner as in Example 1, except that the magnetic powder volume was changed to 1200 nm3 .
  • the extraction rate of stearic acid is 48%
  • the 5-minute extraction amount of stearic acid is 4.70 mg/m 2
  • the total extraction amount of stearic acid is 9.75 mg/m 2
  • the extraction rate of butyl stearate is 64%
  • the 5-minute extraction amount of butyl stearate was 12.99 mg/m 2
  • the total extraction amount of butyl stearate was 20.29 mg/m 2 .
  • the average height (H 2 ) of the protrusions formed by ⁇ -Al 2 O 3 was 5.1 nm. In addition, there was little adhesion to the magnetic head, and no output deterioration occurred.
  • Example 11 A magnetic tape was obtained in the same manner as in Example 1, except that the magnetic powder volume was changed to 2500 nm3 .
  • the extraction rate of stearic acid is 54%
  • the 5-minute extraction amount of stearic acid is 4.85 mg/m 2
  • the total extraction amount of stearic acid is 9.06 mg/m 2
  • the extraction rate of butyl stearate is 67%
  • the 5-minute extraction amount of butyl stearate was 13.05 mg/m 2
  • the total extraction amount of butyl stearate was 19.55 mg/m 2 .
  • the average height (H 2 ) of the protrusions formed by ⁇ -Al 2 O 3 was 4.7 nm. In addition, there was little adhesion to the magnetic head, and no output deterioration occurred.
  • Example 12 A magnetic tape was obtained in the same manner as in Example 1, except that the P/B ratio of the underlayer was changed.
  • the extraction rate of stearic acid is 58%
  • the 5-minute extraction amount of stearic acid is 4.53 mg/m 2
  • the total extraction amount of stearic acid is 7.76 mg/m 2
  • the extraction rate of butyl stearate is 79%
  • the 5-minute extraction amount of butyl stearate was 10.81 mg/m 2
  • the total extraction amount of butyl stearate was 13.67 mg/m 2 .
  • the average height (H 2 ) of the protrusions formed by ⁇ -Al 2 O 3 was 5.8 nm. In addition, there was little adhesion to the magnetic head, and no output deterioration occurred.
  • Example 13 A magnetic tape was obtained in the same manner as in Example 1 except that the P/B ratio of the underlayer was changed and phenylphosphonic acid was used as the organic acid.
  • the extraction rate of stearic acid is 55%
  • the 5-minute extraction amount of stearic acid is 3.86 mg/m 2
  • the total extraction amount of stearic acid is 7.06 mg/m 2
  • the extraction rate of butyl stearate is 77%
  • the 5-minute extraction amount of butyl stearate was 11.18 mg/m 2
  • the total extraction amount of butyl stearate was 14.48 mg/m 2 .
  • the average height (H 2 ) of the protrusions formed by ⁇ -Al 2 O 3 was 5.8 nm. In addition, there was little adhesion to the magnetic head, and no output deterioration occurred.
  • Example 1 A magnetic tape was obtained in the same manner as in Example 1, except that the amount of organic acid added was small.
  • the extraction rate of stearic acid is 41%
  • the 5-minute extraction amount of stearic acid is 3.49 mg/m 2
  • the total extraction amount of stearic acid is 8.48 mg/m 2
  • the extraction rate of butyl stearate is 64%
  • the 5-minute extraction amount of butyl stearate was 12.55 mg/m 2
  • the total extraction amount of butyl stearate was 19.50 mg/m 2 .
  • the average height (H 2 ) of the protrusions formed by ⁇ -Al 2 O 3 was 5.3 nm. The output deterioration was remarkable, and the head was often damaged.
  • Comparative Example 2 A magnetic tape was obtained in the same manner as in Comparative Example 1, except that ⁇ -Al 2 O 3 with a particle size of 80 nm (HIT-82) was used and the amount of butyl stearate was reduced.
  • the extraction rate of stearic acid is 41%
  • the 5-minute extraction amount of stearic acid is 2.44 mg/m 2
  • the total extraction amount of stearic acid is 5.90 mg/m 2
  • the extraction rate of butyl stearate is 59%
  • the 5-minute extraction amount of butyl stearate was 6.74 mg/m 2
  • the total extraction amount of butyl stearate was 11.35 mg/m 2 .
  • the average height (H 2 ) of the protrusions formed by ⁇ -Al 2 O 3 was 5.2 nm. A large amount of deposits was found on the magnetic head.
  • a magnetic tape was obtained in the same manner as in Comparative Example 1, except that the volume of the magnetic powder was 2500 nm 3 .
  • the extraction rate of stearic acid is 38%
  • the 5-minute extraction amount of stearic acid is 2.72 mg/m 2
  • the total extraction amount of stearic acid is 7.17 mg/m 2
  • the extraction rate of butyl stearate is 51%
  • the 5-minute extraction amount of butyl stearate was 5.73 mg/m 2
  • the total extraction amount of butyl stearate was 11.20 mg/m 2 .
  • the average height (H 2 ) of the protrusions formed by ⁇ -Al 2 O 3 was 5.1 nm. The output deterioration was remarkable, and the head was often damaged.
  • Example 1 was carried out except that the average height (H 2 ) of the protrusions formed by ⁇ -Al 2 O 3 was greater than 7 nm, and the total extraction amount and 5-minute extraction amount of stearic acid were reduced.
  • a magnetic tape was obtained in the same manner as in Example 1.
  • the extraction rate of stearic acid is 51%
  • the 5-minute extraction amount of stearic acid is 1.51 mg/m 2
  • the total extraction amount of stearic acid is 2.97 mg/m 2
  • the extraction rate of butyl stearate is 91%
  • the 5-minute extraction amount of butyl stearate was 23.87 mg/m 2
  • the total extraction amount of butyl stearate was 26.29 mg/m 2 .
  • the average height (H 2 ) of the protrusions formed by ⁇ -Al 2 O 3 was 8.2 nm. The output deterioration was remarkable, and the head was often damaged.
  • Table 1 shows the configurations and evaluation results of the magnetic tapes of Examples 1-13 and Comparative Examples 1-4.
  • t T Average thickness of magnetic tape (average total thickness) (unit: ⁇ m)
  • t m average thickness of the magnetic layer (unit: nm)
  • t b Average thickness of the back layer (unit: ⁇ m)
  • the average height (H 2 ) of protrusions formed by the second particles was 7 nm or less, and the extraction rate of stearic acid, which is a fatty acid, was 45% or more. There was little adhesion to the head, and no deterioration in output occurred.
  • the magnetic tape of Comparative Example 2 had a butyl stearate extraction rate of less than 50% and a large amount of deposits on the magnetic head.
  • the magnetic tape of Comparative Example 3 has a butyl stearate extraction ratio of less than 60%, a large amount of deposits on the magnetic head, and a large degree of output deterioration. Met.
  • the magnetic tape of Comparative Example 4 had a stearic acid extraction rate of 45% or more, but the projections formed by alumina corresponding to the second particles The height exceeded 7 nm, and the degree of output deterioration was large.
  • the configurations, methods, steps, shapes, materials, numerical values, etc. given in the above-described embodiments and examples are merely examples, and different configurations, methods, steps, shapes, materials, and the like may be necessary.
  • a numerical value or the like may be used.
  • the chemical formulas of compounds and the like are representative ones, and the valence numbers and the like are not limited as long as they are common names of the same compound.
  • a numerical range indicated using “to” indicates a range that includes the numerical values before and after “to” as the minimum and maximum values, respectively.
  • the upper limit or lower limit of the numerical range in one step may be replaced with the upper limit or lower limit of the numerical range in another step.
  • the materials exemplified in this specification can be used singly or in combination of two or more unless otherwise specified.

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US6607806B2 (en) * 1999-12-09 2003-08-19 Fuji Photo Film Co., Ltd. Magnetic recording medium
JP2003132516A (ja) * 2001-10-25 2003-05-09 Fuji Photo Film Co Ltd 磁気記録媒体
JP2004005796A (ja) * 2002-05-30 2004-01-08 Fuji Photo Film Co Ltd 磁気記録テープ
JP2009054272A (ja) * 2007-07-27 2009-03-12 Fujifilm Corp 磁気信号再生システムおよび磁気信号再生方法
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WO2022209316A1 (ja) * 2021-03-31 2022-10-06 ソニーグループ株式会社 磁気記録媒体
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JP2001006148A (ja) * 1999-06-17 2001-01-12 Sony Corp 磁気記録媒体およびその製造方法
JP2016051492A (ja) * 2014-08-29 2016-04-11 富士フイルム株式会社 磁気テープ

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