WO2022025154A1 - Magnetic recording medium, magnetic tape cartridge, and magnetic recording playback device - Google Patents

Magnetic recording medium, magnetic tape cartridge, and magnetic recording playback device Download PDF

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Publication number
WO2022025154A1
WO2022025154A1 PCT/JP2021/028012 JP2021028012W WO2022025154A1 WO 2022025154 A1 WO2022025154 A1 WO 2022025154A1 JP 2021028012 W JP2021028012 W JP 2021028012W WO 2022025154 A1 WO2022025154 A1 WO 2022025154A1
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magnetic
powder
recording medium
magnetic layer
layer
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PCT/JP2021/028012
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French (fr)
Japanese (ja)
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典子 小柳
佑介 和多田
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富士フイルム株式会社
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Publication of WO2022025154A1 publication Critical patent/WO2022025154A1/en

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    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/48Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
    • G11B5/58Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B5/584Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following on tapes
    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62Record carriers characterised by the selection of the material
    • G11B5/68Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
    • G11B5/70Record 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
    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62Record carriers characterised by the selection of the material
    • G11B5/73Base 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
    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62Record carriers characterised by the selection of the material
    • G11B5/73Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer
    • G11B5/735Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer characterised by the back layer
    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/74Record carriers characterised by the form, e.g. sheet shaped to wrap around a drum
    • G11B5/78Tape carriers

Definitions

  • the present invention relates to a magnetic recording medium, a magnetic tape cartridge, and a magnetic recording / playback device.
  • a magnetic recording medium is widely used as a recording medium for recording various data (see, for example, Patent Document 1).
  • the magnetic recording medium is required to exhibit excellent electromagnetic conversion characteristics, and further improvement of the electromagnetic conversion characteristics is desired.
  • the magnetic recording medium usually has a magnetic layer containing a ferromagnetic powder on a non-magnetic support, and the surface shape of the magnetic layer may affect the performance of the magnetic recording medium.
  • Patent Document 1 Japanese Unexamined Patent Publication No. 2004-103137
  • Patent Document 1 Japanese Unexamined Patent Publication No. 2004-103137 proposes to control the surface shape of the magnetic layer based on the power spectrum density.
  • the present inventor has aimed to provide a magnetic recording medium having further excellent electromagnetic conversion characteristics than the electromagnetic conversion characteristics that can be achieved by controlling the surface shape of the magnetic layer, which has been conventionally proposed.
  • one aspect of the present invention is to provide a magnetic recording medium capable of exhibiting excellent electromagnetic conversion characteristics.
  • a magnetic recording medium having a non-magnetic support and a magnetic layer containing a ferromagnetic powder.
  • the above-mentioned Half-Rq is the root mean square roughness obtained only for the positive part of the surface profile data obtained by inverse Fourier transforming the components having a frequency of 25 Hz (hertz) or less with respect to the power spectrum density of the surface of the magnetic layer. That's right.
  • the Half-Rq can be 0.5 nm or more and 3.0 nm or less.
  • the Half-Rq can be 2.0 nm or less.
  • the Half-Rq can be 0.5 nm or more and 2.0 nm or less.
  • the magnetic recording medium can have at least one non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer.
  • the magnetic recording medium can have two non-magnetic layers.
  • the magnetic recording medium can contain non-magnetic iron oxide powder in the non-magnetic layer on the magnetic layer side of the two non-magnetic layers, and carbon black in the non-magnetic layer on the non-magnetic support side. Can be included.
  • the non-magnetic iron oxide powder can be ⁇ -iron oxide powder.
  • the magnetic recording medium can further have a backcoat layer containing non-magnetic powder on the surface side of the non-magnetic support opposite to the surface side having the magnetic layer.
  • the magnetic recording medium can be a magnetic tape.
  • One aspect of the present invention relates to a magnetic tape cartridge containing the above magnetic tape.
  • One aspect of the present invention relates to a magnetic recording / reproducing device including the above magnetic recording medium and a magnetic head.
  • a magnetic recording medium capable of exhibiting excellent electromagnetic conversion characteristics. Further, according to one aspect of the present invention, it is possible to provide a magnetic tape cartridge and a magnetic recording / reproducing device including the magnetic recording medium.
  • An example of arranging the data band and the servo band is shown.
  • An example of arranging the servo pattern of the LTO (Linear Tape-Open) Ultrium format tape is shown.
  • Magnetic recording medium One aspect of the present invention relates to a magnetic recording medium having a non-magnetic support and a magnetic layer containing a ferromagnetic powder.
  • Half-Rq required on the surface of the magnetic layer is 3.0 nm or less.
  • the Half-Rq is the root mean square roughness obtained only for the positive part of the surface profile data obtained by inverse Fourier transforming the components having a frequency of 25 Hz or less with respect to the power spectrum density of the surface of the magnetic layer. ..
  • AFM measurement On the surface of the magnetic layer of the magnetic recording medium to be measured, an atomic force microscope (AFM) is used for measurement, and an AFM image is acquired.
  • the "surface of the magnetic layer” is synonymous with the surface of the magnetic recording medium on the magnetic layer side.
  • the following measurement conditions can be mentioned as an example of the AFM measurement conditions.
  • AFM Nanoscope 4 manufactured by Veeco
  • RTESS-300 manufactured by BRUKER the resolution is 512pixel ⁇ 512pixel
  • the scanning speed is the speed at which one screen (512pixel ⁇ 512pixel) is measured in 341 seconds.
  • PSD Power Spectrum Density
  • AFM image acquired by AFM measurement one side of the measurement area of 40 ⁇ m ⁇ 40 ⁇ m is divided into 512, the sampling ratio is set to 40/512 ⁇ m in profiling, two-dimensional Fourier transform is performed on the surface roughness curved surface, and the maximum wavelength is 40 ⁇ m.
  • a total of 256 wavelength component PSDs up to the shortest wavelength of 0.15625 ⁇ m are obtained.
  • the above-mentioned sampling ratio means the frequency of setting the sample points.
  • Half-Rq (Calculation of Half-Rq) With respect to the PSD obtained above, in the surface profile data obtained by inverse Fourier transforming the components having a frequency of 25 Hz or less, only the positive part is calculated by the following formula to obtain Half-Rq.
  • the positive portion corresponds to the height value of the portion (convex portion) having a convex shape with respect to the reference plane.
  • the reference plane is a plane (height zero) in which the volumes of the convex portion and the concave portion are equal to each other.
  • Half-Rq includes the data of the positive part (positive value data) corresponding to the height value of the convex portion and the data of the negative part (negative value data) corresponding to the depth value of the concave portion.
  • Half-Rq the "average height” is the arithmetic mean of the height values
  • sample point height the height value at the sample points.
  • the arithmetic mean of the values calculated for each of the three different measurement points is defined as Half-Rq obtained on the surface of the magnetic layer of the magnetic recording medium to be measured.
  • An AFM image (512pixel ⁇ 512pixel) is acquired, and the surface roughness curve of this AFM image is Fourier transformed to obtain a frequency component image (512pixel ⁇ 512pixel).
  • a shift operation is performed so that the central part is a low frequency component and the peripheral part is a high frequency component. ..
  • a sigmoid function may be used in order to make the boundary between the inside and the outside of the circle smooth.
  • the shift operation is performed again. In this way, a low frequency image having a frequency of 25 Hz or less is obtained.
  • Half-Rq is obtained as described above.
  • the fact that Half-Rq obtained by the method described above is 3.0 nm or less can contribute to the improvement of electromagnetic conversion characteristics.
  • the surface shape of the magnetic layer it is considered that the shape of the waviness existing on the surface of the magnetic layer may affect the electromagnetic conversion characteristics.
  • the present inventor can obtain a value that can be an index of a swell having a longer wavelength than the swell conventionally evaluated by the PSD by performing an inverse Fourier transform on a component having a frequency of 25 Hz or less in the PSD as described above. I think I can do it.
  • the period of such long-wavelength swell is the period of unevenness that may exist on the sliding surface of the magnetic head that is normally used for recording data on the magnetic layer and / or reproducing the data recorded on the magnetic layer.
  • the present inventor speculates that the cycle is close to that of. The present inventor thinks that this is the reason why controlling Half-Rq obtained by the method described above may contribute to the improvement of electromagnetic conversion characteristics.
  • the Half-Rq is a value obtained only for the positive part of the surface profile data, that is, only for the convex part of the surface of the magnetic layer.
  • the spacing between the magnetic layer surface and the magnetic head if the spacing is wide, the electromagnetic conversion characteristics tend to deteriorate due to the spacing loss.
  • Half-Rq which is obtained only for the positive portion as described above, is a value that can be well correlated with the electromagnetic conversion characteristics.
  • the present inventor believes that setting this value to 3.0 nm or less leads to improvement in electromagnetic conversion characteristics.
  • the above includes speculation.
  • the inferences described herein are not limited to the present invention.
  • the Half-Rq required on the surface of the magnetic layer of the magnetic recording medium is 3.0 nm or less, preferably 2.8 nm or less, and more preferably 2.6 nm or less. It is preferably 2.4 nm or less, more preferably 2.2 nm or less, further preferably 2.0 nm or less, still more preferably 1.8 nm or less.
  • the Half-Rq required on the surface of the magnetic layer of the magnetic recording medium can be, for example, 0.5 nm or more, 0.7 nm or more, or 1.0 nm or more, and can be lower than the values exemplified here. It is preferable that the value of Half-Rq is small from the viewpoint of improving the electromagnetic conversion characteristics.
  • ferromagnetic powder As the ferromagnetic powder contained in the magnetic layer, one or a combination of two or more kinds of ferromagnetic powder known as the ferromagnetic powder used in the magnetic layer of various magnetic recording media can be used. It is preferable to use a ferromagnetic powder having a small average particle size from the viewpoint of improving the recording density. From this point, the average particle size of the ferromagnetic powder is preferably 50 nm or less, more preferably 45 nm or less, further preferably 40 nm or less, further preferably 35 nm or less, and more preferably 30 nm or less. It is even more preferably 25 nm or less, and even more preferably 20 nm or less.
  • the average particle size of the ferromagnetic powder is preferably 5 nm or more, more preferably 8 nm or more, further preferably 10 nm or more, and further preferably 15 nm or more. Is more preferable, and 20 nm or more is even more preferable.
  • the average particle volume of the ferromagnetic powder can also be mentioned as an index of the particle size.
  • the average particle volume is preferably 2500 nm 3 or less, more preferably 2300 nm 3 or less, further preferably 2000 nm 3 or less, and even more preferably 1500 nm 3 or less. ..
  • the average particle volume of the ferromagnetic powder is preferably 500 nm 3 or more, more preferably 600 nm 3 or more, further preferably 650 nm 3 or more, and 700 nm 3 or more. Is more preferable.
  • the above average particle volume is a value obtained as a sphere-equivalent volume from the average particle size obtained by the method described later.
  • Hexagonal ferrite powder As a preferable specific example of the ferromagnetic powder, hexagonal ferrite powder can be mentioned.
  • hexagonal ferrite powder for details of the hexagonal ferrite powder, for example, paragraphs 0012 to 0030 of JP 2011-225417, paragraphs 0134 to 0136 of JP 2011-216149, paragraphs 0013 to 0030 of JP 2012-204726 and References can be made to paragraphs 0029 to 0084 of JP-A-2015-127985.
  • the "hexagonal ferrite powder” refers to a ferromagnetic powder in which a hexagonal ferrite type crystal structure is detected as the main phase by X-ray diffraction analysis.
  • the main phase refers to a structure to which the highest intensity diffraction peak belongs in the X-ray diffraction spectrum obtained by X-ray diffraction analysis. For example, when the highest intensity diffraction peak is attributed to the hexagonal ferrite type crystal structure in the X-ray diffraction spectrum obtained by X-ray diffraction analysis, it is determined that the hexagonal ferrite type crystal structure is detected as the main phase. It shall be.
  • the hexagonal ferrite type crystal structure contains at least iron atoms, divalent metal atoms and oxygen atoms as constituent atoms.
  • the divalent metal atom is a metal atom that can be a divalent cation as an ion, and examples thereof include an alkaline earth metal atom such as a strontium atom, a barium atom, and a calcium atom, and a lead atom.
  • the hexagonal strontium ferrite powder means that the main divalent metal atom contained in this powder is a strontium atom, and the hexagonal barium ferrite powder is the main contained in this powder.
  • a divalent metal atom is a barium atom.
  • the main divalent metal atom is a divalent metal atom that occupies the largest amount on an atomic% basis among the divalent metal atoms contained in this powder.
  • rare earth atoms are not included in the above divalent metal atoms.
  • the "rare earth atom" in the present invention and the present specification is selected from the group consisting of a scandium atom (Sc), a yttrium atom (Y), and a lanthanoid atom.
  • the lanthanoid atoms are lanthanum atom (La), cerium atom (Ce), placeodium atom (Pr), neodymium atom (Nd), promethium atom (Pm), samarium atom (Sm), uropyum atom (Eu), gadrinium atom (Gd). ), Terbium atom (Tb), dysprosium atom (Dy), formium atom (Ho), erbium atom (Er), thulium atom (Tm), ytterbium atom (Yb), and lutetium atom (Lu).
  • La lanthanum atom
  • Ce cerium atom
  • Pr placeodium atom
  • Nd neodymium atom
  • Pm promethium atom
  • Sm samarium atom
  • Eu gadrinium atom
  • Tb Terbium atom
  • Dy dysprosium atom
  • Ho formium atom
  • Er er
  • the hexagonal strontium ferrite powder which is a form of hexagonal ferrite powder, will be described in more detail below.
  • the activated volume of the hexagonal strontium ferrite powder is preferably in the range of 800 to 1600 nm 3 .
  • the finely divided hexagonal strontium ferrite powder exhibiting the activated volume in the above range is suitable for producing a magnetic recording medium exhibiting excellent electromagnetic conversion characteristics.
  • the activated volume of the hexagonal strontium ferrite powder is preferably 800 nm 3 or more, and can be, for example, 850 nm 3 or more. Further, from the viewpoint of further improving the electromagnetic conversion characteristics, the activated volume of the hexagonal strontium ferrite powder is more preferably 1500 nm 3 or less, further preferably 1400 nm 3 or less, and 1300 nm 3 or less. Is even more preferable, and it is even more preferably 1200 nm 3 or less, and even more preferably 1100 nm 3 or less. The same applies to the activated volume of the hexagonal barium ferrite powder.
  • the "activated volume” is a unit of magnetization reversal and is an index showing the magnetic size of a particle.
  • the activated volume described in the present invention and the present specification and the anisotropic constant Ku described later are measured using a vibrating sample magnetometer at magnetic field sweep speeds of 3 minutes and 30 minutes in the coercive force Hc measuring unit (measurement). Temperature: 23 ° C ⁇ 1 ° C), which is a value obtained from the following relational expression between Hc and activated volume V.
  • 1 erg / cc 1.0 ⁇ 10 -1 J / m 3 .
  • Hc 2Ku / Ms ⁇ 1-[(kT / KuV) ln (At / 0.693)] 1/2 ⁇
  • Ku anisotropic constant (unit: J / m 3 )
  • Ms saturation magnetization (unit: kA / m)
  • k Boltzmann constant
  • T absolute temperature (unit: K)
  • V activity. Volume (Unit: cm 3 )
  • A Spin old frequency (Unit: s -1 )
  • t Magnetic field reversal time (Unit: s)]
  • Anisotropy constant Ku can be mentioned as an index for reducing thermal fluctuation, in other words, improving thermal stability.
  • the hexagonal strontium ferrite powder can preferably have a Ku of 1.8 ⁇ 10 5 J / m 3 or more, and more preferably 2.0 ⁇ 105 J / m 3 or more. Further, the Ku of the hexagonal strontium ferrite powder can be, for example, 2.5 ⁇ 105 J / m 3 or less. However, the higher the Ku, the higher the thermal stability, which is preferable, and therefore, the value is not limited to the above-exemplified values.
  • the hexagonal strontium ferrite powder may or may not contain rare earth atoms.
  • the hexagonal strontium ferrite powder contains rare earth atoms, it is preferable that the hexagonal strontium ferrite powder contains rare earth atoms at a content of 0.5 to 5.0 atomic% (bulk content) with respect to 100 atomic% of iron atoms.
  • the hexagonal strontium ferrite powder containing a rare earth atom can have uneven distribution on the surface layer of the rare earth atom.
  • rare earth atom content refers to the rare earth atom content with respect to 100 atomic% of iron atoms in the solution obtained by partially dissolving hexagonal strontium ferrite powder with an acid (hereinafter referred to as "rare earth atom content”).
  • “Rare earth atom surface layer content” or simply “surface layer content” for rare earth atoms) is 100 atomic% of iron atoms in the solution obtained by completely dissolving hexagonal strontium ferrite powder with an acid.
  • Rare earth atom content hereinafter referred to as "rare earth atom bulk content” or simply referred to as “bulk content” for rare earth atoms).
  • the rare earth atom content of the hexagonal strontium ferrite powder described later is synonymous with the rare earth atom bulk content.
  • partial dissolution using an acid dissolves the surface layer of the particles constituting the hexagonal strontium ferrite powder, so the rare earth atom content in the solution obtained by partial dissolution is the composition of the hexagonal strontium ferrite powder. It is the rare earth atom content in the surface layer of the particles.
  • the fact that the rare earth atom surface layer content satisfies the ratio of "rare earth atom surface layer content / rare earth atom bulk content>1.0" means that the rare earth atom is on the surface layer in the particles constituting the hexagonal strontium ferrite powder. It means that they are unevenly distributed (that is, they exist more than inside).
  • the surface layer portion in the present invention and the present specification means a partial region from the surface of the particles constituting the hexagonal strontium ferrite powder toward the inside.
  • the rare earth atom content is preferably in the range of 0.5 to 5.0 atomic% with respect to 100 atomic% of iron atoms.
  • the fact that the rare earth atoms are contained in the bulk content in the above range and the rare earth atoms are unevenly distributed on the surface layer of the particles constituting the hexagonal strontium ferrite powder contributes to suppressing the decrease in the regeneration output in the repeated regeneration. Conceivable. This is because the hexagonal strontium ferrite powder contains rare earth atoms at a bulk content in the above range, and the rare earth atoms are unevenly distributed on the surface layer of the particles constituting the hexagonal strontium ferrite powder.
  • hexagonal strontium ferrite powder which has uneven distribution on the surface of rare earth atoms, as a ferromagnetic powder for the magnetic layer also contributes to suppressing the surface of the magnetic layer from being scraped by sliding with the magnetic head.
  • Ru that is, it is presumed that the hexagonal strontium ferrite powder having uneven distribution of the rare earth atomic surface layer can also contribute to the improvement of the running durability of the magnetic recording medium. This is because the uneven distribution of rare earth atoms on the surface of the particles constituting the hexagonal strontium ferrite powder improves the interaction between the particle surface and the organic substances (for example, binder and / or additive) contained in the magnetic layer.
  • the rare earth atom content is in the range of 0.5 to 4.5 atomic% from the viewpoint of further suppressing the decrease in the reproduction output in the repeated reproduction and / or further improving the running durability. It is more preferably in the range of 1.0 to 4.5 atomic%, further preferably in the range of 1.5 to 4.5 atomic%.
  • the bulk content is the content obtained by completely dissolving the hexagonal strontium ferrite powder.
  • the content of atoms means the bulk content obtained by completely dissolving hexagonal strontium ferrite powder.
  • the hexagonal strontium ferrite powder containing a rare earth atom may contain only one kind of rare earth atom as a rare earth atom, or may contain two or more kinds of rare earth atoms.
  • the bulk content when two or more rare earth atoms are contained is determined for the total of two or more rare earth atoms. This point is the same for the present invention and other components in the present specification. That is, unless otherwise specified, a certain component may be used alone or in combination of two or more.
  • the content or content rate when two or more types are used shall mean the total of two or more types.
  • the rare earth atom contained may be any one or more of the rare earth atoms.
  • Preferred rare earth atoms from the viewpoint of further suppressing the decrease in regeneration output in repeated regeneration include neodymium atom, samarium atom, yttrium atom and dysprosium atom, and neodymium atom, samarium atom and yttrium atom are more preferable, and neodymium atom is more preferable. Atoms are more preferred.
  • the rare earth atoms may be unevenly distributed on the surface layer of the particles constituting the hexagonal strontium ferrite powder, and the degree of uneven distribution is not limited.
  • a hexagonal strontium ferrite powder having uneven distribution on the surface layer of a rare earth atom is partially dissolved under the dissolution conditions described later and the content of the surface layer of the rare earth atom and the rare earths obtained by completely dissolving under the dissolution conditions described later.
  • the ratio of the atom to the bulk content, "surface layer content / bulk content" is more than 1.0, and can be 1.5 or more.
  • the "surface layer content / bulk content” is larger than 1.0, it means that the rare earth atoms are unevenly distributed (that is, more present than the inside) in the particles constituting the hexagonal strontium ferrite powder. do. Further, the ratio of the surface layer content of the rare earth atom obtained by partial melting under the dissolution conditions described later and the bulk content of the rare earth atom obtained by total dissolution under the dissolution conditions described later, "surface layer content / The “bulk content” can be, for example, 10.0 or less, 9.0 or less, 8.0 or less, 7.0 or less, 6.0 or less, 5.0 or less, or 4.0 or less.
  • the rare earth atoms may be unevenly distributed on the surface layer of the particles constituting the hexagonal strontium ferrite powder.
  • the "rate" is not limited to the upper and lower limits exemplified.
  • the hexagonal strontium ferrite powder can be taken out from the magnetic layer by, for example, the method described in paragraph 0032 of Japanese Patent Application Laid-Open No. 2015-91747.
  • the above partial dissolution means that the hexagonal strontium ferrite powder is dissolved in the liquid to the extent that the residue of the hexagonal strontium ferrite powder can be visually confirmed at the end of the dissolution.
  • a region of 10 to 20% by mass can be dissolved with respect to the particles constituting the hexagonal strontium ferrite powder, with the entire particles as 100% by mass.
  • the above-mentioned total dissolution means that the hexagonal strontium ferrite powder is dissolved in the liquid until the residue is not visually confirmed at the end of the dissolution.
  • the above partial melting and measurement of the surface layer content are carried out by, for example, the following methods.
  • dissolution conditions such as the amount of sample powder are examples, and dissolution conditions capable of partial dissolution and total dissolution can be arbitrarily adopted.
  • a container for example, a beaker
  • 10 mL of 1 mol / L hydrochloric acid is held on a hot plate at a set temperature of 70 ° C. for 1 hour.
  • the obtained solution is filtered through a 0.1 ⁇ m membrane filter. Elemental analysis of the filtrate thus obtained is performed by an inductively coupled plasma (ICP) analyzer. In this way, the content of the rare earth atom in the surface layer with respect to 100 atom% of the iron atom can be obtained.
  • ICP inductively coupled plasma
  • the total content of all rare earth atoms is defined as the surface layer content. This point is the same in the measurement of bulk content.
  • the total dissolution and the measurement of the bulk content are carried out by, for example, the following methods.
  • a container for example, a beaker
  • sample powder containing 12 mg of sample powder and 10 mL of 4 mol / L hydrochloric acid is held on a hot plate at a set temperature of 80 ° C. for 3 hours. After that, the same procedure as the above-mentioned partial melting and measurement of the surface layer content can be performed to determine the bulk content with respect to 100 atomic% of iron atoms.
  • the mass magnetization ⁇ s of the ferromagnetic powder contained in the magnetic recording medium is high.
  • the hexagonal strontium ferrite powder containing rare earth atoms but not having uneven distribution on the surface layer of rare earth atoms tended to have a significantly lower ⁇ s than the hexagonal strontium ferrite powder containing no rare earth atoms.
  • hexagonal strontium ferrite powder having uneven distribution on the surface layer of rare earth atoms is considered to be preferable in order to suppress such a large decrease in ⁇ s.
  • the ⁇ s of the hexagonal strontium ferrite powder can be 45 A ⁇ m 2 / kg or more, and can also be 47 A ⁇ m 2 / kg or more.
  • ⁇ s is preferably 80 A ⁇ m 2 / kg or less, and more preferably 60 A ⁇ m 2 / kg or less, from the viewpoint of noise reduction.
  • ⁇ s can be measured using a known measuring device capable of measuring magnetic characteristics such as a vibration sample magnetometer.
  • the strontium atom content can be in the range of, for example, 2.0 to 15.0 atom% with respect to 100 atom% of iron atoms. ..
  • the hexagonal strontium ferrite powder can contain only strontium atoms as divalent metal atoms contained in the powder.
  • the hexagonal strontium ferrite powder may contain one or more other divalent metal atoms in addition to the strontium atom. For example, it can contain barium and / or calcium atoms.
  • the barium atom content and the calcium atom content in the hexagonal strontium ferrite powder are, for example, 0.05 to 5 with respect to 100 atomic% of the iron atom, respectively. It can be in the range of 0.0 atomic%.
  • hexagonal strontium ferrite As the crystal structure of hexagonal ferrite, a magnetoplumbite type (also referred to as "M type"), a W type, a Y type, and a Z type are known.
  • the hexagonal strontium ferrite powder may have any crystal structure. The crystal structure can be confirmed by X-ray diffraction analysis. Hexagonal strontium ferrite powder can be one in which a single crystal structure or two or more kinds of crystal structures are detected by X-ray diffraction analysis. For example, in one form, the hexagonal strontium ferrite powder can be such that only the M-type crystal structure is detected by X-ray diffraction analysis.
  • M-type hexagonal ferrite is represented by the composition formula of AFe 12 O 19 .
  • A represents a divalent metal atom
  • the strontium atom (Sr) occupies the largest amount on the basis of atomic%.
  • the divalent metal atom content of the hexagonal strontium ferrite powder is usually determined by the type of the crystal structure of the hexagonal ferrite, and is not particularly limited. The same applies to the iron atom content and the oxygen atom content.
  • the hexagonal strontium ferrite powder contains at least an iron atom, a strontium atom and an oxygen atom, and may further contain a rare earth atom. Further, the hexagonal strontium ferrite powder may or may not contain atoms other than these atoms. As an example, the hexagonal strontium ferrite powder may contain an aluminum atom (Al). The content of aluminum atoms can be, for example, 0.5 to 10.0 atomic% with respect to 100 atomic% of iron atoms.
  • the hexagonal strontium ferrite powder contains iron atoms, strontium atoms, oxygen atoms and rare earth atoms, and the content of atoms other than these atoms is 100 iron atoms.
  • the content expressed in atomic% above is the content of each atom (unit: mass%) obtained by completely dissolving the hexagonal strontium ferrite powder, and is expressed in atomic% using the atomic weight of each atom. Calculated by conversion.
  • "not contained" with respect to a certain atom means that the content is completely dissolved and the content measured by the ICP analyzer is 0% by mass.
  • the detection limit of an ICP analyzer is usually 0.01 ppm (parts per million) or less on a mass basis. The above-mentioned "not included” is used in the sense of including the inclusion in an amount less than the detection limit of the ICP analyzer.
  • the hexagonal strontium ferrite powder can, in one form, be free of bismuth atoms (Bi).
  • Metallic powder Ferromagnetic metal powder can also be mentioned as a preferable specific example of the ferromagnetic powder.
  • paragraphs 0137 to 0141 of JP2011-216149A and paragraphs 0009 to 0023 of JP2005-251351 can be referred to.
  • ⁇ -Iron oxide powder As a preferable specific example of the ferromagnetic powder, ⁇ -iron oxide powder can also be mentioned.
  • ⁇ -iron oxide powder refers to a ferromagnetic powder in which an ⁇ -iron oxide type crystal structure is detected as a main phase by X-ray diffraction analysis. For example, when the highest intensity diffraction peak is attributed to the ⁇ -iron oxide type crystal structure in the X-ray diffraction spectrum obtained by X-ray diffraction analysis, the ⁇ -iron oxide type crystal structure is detected as the main phase. It shall be judged.
  • a method for producing ⁇ -iron oxide powder As a method for producing ⁇ -iron oxide powder, a method for producing goethite, a reverse micelle method, and the like are known. All of the above manufacturing methods are known. Further, regarding a method for producing an ⁇ -iron oxide powder in which a part of Fe is substituted with a substituted atom such as Ga, Co, Ti, Al, Rh, for example, J. Jpn. Soc. Powder Metallurgy Vol. 61 Supplement, No. S1, pp. S280-S284, J. Mol. Mater. Chem. C, 2013, 1, pp. 5200-5206 and the like can be referred to. However, the method for producing ⁇ -iron oxide powder that can be used as the ferromagnetic powder in the magnetic layer of the magnetic recording medium is not limited to the method described here.
  • the activated volume of the ⁇ -iron oxide powder is preferably in the range of 300 to 1500 nm 3 .
  • the finely divided ⁇ -iron oxide powder exhibiting an activated volume in the above range is suitable for producing a magnetic recording medium exhibiting excellent electromagnetic conversion characteristics.
  • the activated volume of the ⁇ -iron oxide powder is preferably 300 nm 3 or more, and can be, for example, 500 nm 3 or more. Further, from the viewpoint of further improving the electromagnetic conversion characteristics, the activated volume of the ⁇ -iron oxide powder is more preferably 1400 nm 3 or less, further preferably 1300 nm 3 or less, and 1200 nm 3 or less. Is more preferable, and 1100 nm 3 or less is even more preferable.
  • Anisotropy constant Ku can be mentioned as an index for reducing thermal fluctuation, in other words, improving thermal stability.
  • the ⁇ -iron oxide powder can preferably have a Ku of 3.0 ⁇ 10 4 J / m 3 or more, and more preferably 8.0 ⁇ 10 4 J / m 3 or more. Further, the Ku of the ⁇ -iron oxide powder can be, for example, 3.0 ⁇ 105 J / m 3 or less. However, the higher the Ku, the higher the thermal stability, which is preferable, and therefore, the value is not limited to the above-exemplified values.
  • the mass magnetization ⁇ s of the ferromagnetic powder contained in the magnetic recording medium is high.
  • the ⁇ s of the ⁇ -iron oxide powder can be 8 A ⁇ m 2 / kg or more, and can also be 12 A ⁇ m 2 / kg or more.
  • the ⁇ s of the ⁇ -iron oxide powder is preferably 40 A ⁇ m 2 / kg or less, and more preferably 35 A ⁇ m 2 / kg or less, from the viewpoint of noise reduction.
  • the average particle size of various powders such as ferromagnetic powders is a value measured by the following method using a transmission electron microscope.
  • the powder is photographed using a transmission electron microscope at an imaging magnification of 100,000 times, and printed on photographic paper so as to have a total magnification of 500,000 times to obtain a photograph of the particles constituting the powder.
  • Select the target particle from the obtained photograph of the particle trace the outline of the particle with a digitizer, and measure the size of the particle (primary particle).
  • Primary particles are independent particles without agglomeration.
  • the above measurements are performed on 500 randomly sampled particles. The arithmetic mean of the particle sizes of the 500 particles thus obtained is taken as the average particle size of the powder.
  • the transmission electron microscope for example, a transmission electron microscope H-9000 manufactured by Hitachi can be used.
  • the particle size can be measured by using a known image analysis software, for example, an image analysis software KS-400 manufactured by Carl Zeiss. Unless otherwise specified, the average particle size shown in the examples described later was measured using a transmission electron microscope H-9000 manufactured by Hitachi as a transmission electron microscope and a Carl Zeiss image analysis software KS-400 as an image analysis software. The value.
  • the powder means an aggregate of a plurality of particles.
  • a ferromagnetic powder means a collection of a plurality of ferromagnetic particles.
  • the set of a plurality of particles is not limited to a form in which the particles constituting the set are in direct contact with each other, and also includes a form in which a binder, an additive, etc., which will be described later, are interposed between the particles.
  • a binder, an additive, etc. which will be described later, are interposed between the particles.
  • particle is sometimes used to describe powder.
  • the size (particle size) of the particles constituting the powder is the shape of the particles observed in the above particle photograph.
  • the particle is spherical, polyhedral, amorphous, etc., and the long axis constituting the particle cannot be specified from the shape, it is represented by the diameter equivalent to a circle.
  • the diameter equivalent to a circle is what is obtained by the circular projection method.
  • the needle-like ratio of the powder is shorter than the arithmetic average (average major axis length) of the major axis length obtained for the above 500 particles by measuring the minor axis length of the particles in the above measurement, that is, the minor axis length. It is obtained as "average major axis length / average minor axis length" from the arithmetic average (average minor axis length) of the axis length.
  • the minor axis length is the length of the minor axis constituting the particle in the case of (1) in the above definition of the particle size, and the thickness or height in the case of the same (2).
  • the average particle size is the average major axis length
  • the average particle size is The average plate diameter.
  • the average particle size is an average diameter (also referred to as an average particle size and an average particle size).
  • the content (filling rate) of the ferromagnetic powder in the magnetic layer is preferably in the range of 50 to 90% by mass, and more preferably in the range of 60 to 90% by mass.
  • a high filling rate of the ferromagnetic powder in the magnetic layer is preferable from the viewpoint of improving the recording density.
  • the magnetic recording medium can be a coating type magnetic recording medium, and the magnetic layer can contain a binder.
  • a binder is one or more resins.
  • various resins usually used as a binder for a coated magnetic recording medium can be used.
  • the binder polyurethane resin, polyester resin, polyamide resin, vinyl chloride resin, styrene, acrylonitrile, acrylic resin obtained by copolymerizing methyl methacrylate and the like, cellulose resin such as nitrocellulose, epoxy resin, phenoxy resin, polyvinyl acetal, etc.
  • a resin selected from a polyvinyl alkyral resin such as polyvinyl butyral can be used alone, or a plurality of resins can be mixed and used.
  • polyurethane resin, acrylic resin, cellulose resin, and vinyl chloride resin are preferable. These resins may be homopolymers or copolymers.
  • These resins can also be used as a binder in the non-magnetic layer and / or the backcoat layer described later.
  • paragraphs 0028 to 0031 of JP-A-2010-24113 can be referred to.
  • the average molecular weight of the resin used as a binder can be, for example, 10,000 or more and 200,000 or less as a weight average molecular weight.
  • the weight average molecular weight in the present invention and the present specification is a value obtained by converting a value measured under the following measurement conditions by gel permeation chromatography (GPC) into polystyrene.
  • the weight average molecular weight of the binder shown in Examples described later is a value obtained by converting a value measured under the following measurement conditions into polystyrene.
  • the binder can be used in an amount of, for example, 1.0 to 30.0 parts by mass with respect to 100.0 parts by mass of the ferromagnetic powder.
  • GPC device HLC-8120 (manufactured by Tosoh) Column: TSK gel Multipore HXL-M (manufactured by Tosoh Corporation, 7.8 mm ID (Inner Diameter) x 30.0 cm) Eluent: Tetrahydrofuran (THF)
  • a curing agent can also be used with a resin that can be used as a binder.
  • the curing agent can be a thermosetting compound which is a compound in which a curing reaction (crosslinking reaction) proceeds by heating in one embodiment, and in another embodiment, a photocuring compound in which a curing reaction (crosslinking reaction) proceeds by light irradiation. It can be a sex compound.
  • the curing agent can be contained in the magnetic layer in a state of reacting (crosslinking) with other components such as a binder, at least in part, as the curing reaction proceeds in the process of forming the magnetic layer. This point is the same for the layer formed by using this composition when the composition used for forming another layer contains a curing agent.
  • the preferred curing agent is a thermosetting compound, and polyisocyanate is preferable.
  • polyisocyanate is preferable.
  • the curing agent is, for example, 0 to 80.0 parts by mass with respect to 100.0 parts by mass of the binder in the composition for forming the magnetic layer, preferably 50.0 to 80.0 from the viewpoint of improving the strength of the magnetic layer. It can be used in the amount of parts by mass.
  • the magnetic layer may contain one or more additives, if necessary.
  • the additive can be used in any amount by appropriately selecting a commercially available product according to desired properties or by producing it by a known method.
  • Examples of the additive include the above-mentioned curing agent.
  • Examples of the additive contained in the magnetic layer include non-magnetic powders, lubricants, dispersants, dispersion aids, fungicides, antistatic agents, antioxidants and the like.
  • paragraphs 0030 to 0033, 0035 and 0036 of JP-A-2016-126817 can be referred to.
  • a lubricant may be contained in the non-magnetic layer described later.
  • paragraphs 0030, 0031, 0034 to 0036 of JP-A-2016-126817 For the dispersant, paragraphs 0061 and 0071 of JP2012-133387A can be referred to.
  • a dispersant may be added to the composition for forming a non-magnetic layer.
  • paragraph 0061 of Japanese Patent Application Laid-Open No. 2012-1333837 can be referred to.
  • non-magnetic powder that can be contained in the magnetic layer examples include non-magnetic powder that can function as an abrasive.
  • the additive that can be used to improve the dispersibility of the abrasive in the magnetic layer containing the abrasive the dispersant described in paragraphs 0012 to 0022 of JP2013-131285A can be mentioned.
  • non-magnetic powder examples include non-magnetic powder (for example, non-magnetic colloid particles, carbon black, etc.) that can function as a protrusion forming agent that forms protrusions that appropriately project on the surface of the magnetic layer. Be done.
  • the protrusion forming agent for example, one having an average particle size of 5 to 300 nm can be used.
  • the average particle size of colloidal silica (silica colloidal particles) shown in Examples described later is a value obtained by the method described in paragraph 0015 of JP-A-2011-048878 as a method for measuring the average particle size. be.
  • the content of the protrusion-forming agent in the magnetic layer is preferably 0.1 to 3.5 parts by mass, more preferably 0.1 to 3.0 parts by mass, for example, per 100.0 parts by mass of the ferromagnetic powder. preferable.
  • the amount of the protrusion forming agent in the magnetic layer is reduced, the value of Half-Rq tends to decrease.
  • the magnetic layer described above can be provided directly on the surface of the non-magnetic support or indirectly via the non-magnetic layer.
  • the magnetic recording medium may have a magnetic layer directly on the surface of the non-magnetic support, and the magnetic layer is formed on the surface of the non-magnetic support via one layer or a plurality of non-magnetic layers containing the non-magnetic powder. You may have.
  • the surface smoothness of the non-magnetic layer which is the surface on which the magnetic layer is formed. From this point of view, it is preferable to use a non-magnetic powder having a small average particle size as the non-magnetic powder contained in the non-magnetic layer.
  • the average particle size of the non-magnetic powder is preferably in the range of 500 nm or less, more preferably 200 nm or less, further preferably 100 nm or less, still more preferably 50 nm or less.
  • the average particle size of the non-magnetic powder is preferably 5 nm or more, more preferably 7 nm or more, and further preferably 10 nm or more. preferable.
  • the non-magnetic powder used for the non-magnetic layer may be an inorganic powder or an organic powder.
  • carbon black or the like can also be used.
  • Non-magnetic layer For carbon black that can be used for the non-magnetic layer, for example, paragraphs 0040 to 0041 of JP2010-24113A can be referred to. Carbon black generally tends to have a large particle size distribution and tends to have poor dispersibility. Therefore, the non-magnetic layer containing carbon black tends to have low surface smoothness. From this point of view, in one embodiment, it is preferable to provide a non-magnetic layer containing a non-magnetic powder other than carbon black as the non-magnetic layer adjacent to the magnetic layer.
  • non-magnetic layer located closest to the magnetic layer as a non-magnetic layer containing non-magnetic powder other than carbon black.
  • two non-magnetic layers are provided between the non-magnetic support and the magnetic layer, and the non-magnetic layer on the non-magnetic support side (also referred to as “lower non-magnetic layer”) is a non-magnetic layer containing carbon black.
  • the non-magnetic layer on the magnetic layer side also referred to as "upper non-magnetic layer
  • the dispersibility of the non-magnetic powder tends to be lower than that in the composition for forming a non-magnetic layer containing one kind of non-magnetic powder. From this point of view, it is preferable to provide a plurality of non-magnetic layers and reduce the types of non-magnetic powder contained in each non-magnetic layer. Further, in one form, it is preferable to use a dispersant in order to enhance the dispersibility of the non-magnetic powder in the composition for forming a non-magnetic layer containing a plurality of types of non-magnetic powder. The dispersant will be described later.
  • the inorganic powder examples include powders of metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, metal sulfides and the like. These non-magnetic powders are commercially available and can also be produced by known methods. For details thereof, refer to paragraphs 0146 to 0150 of JP2011-216149A.
  • non-magnetic iron oxide powder can be mentioned. From the viewpoint of reducing the value of Half-Rq on the surface of the magnetic layer by increasing the surface smoothness of the non-magnetic layer on which the magnetic layer is formed, a non-magnetic iron oxide powder having a small particle size is used. That is preferable. From this point, it is preferable to use a non-magnetic iron oxide powder having an average particle size in the range described above, and it is more preferable to use a non-magnetic iron oxide powder having an average particle size of 50 nm or less. When the non-magnetic iron oxide powder has the particle shape of (1) described above, the average particle size is the average major axis length.
  • the needle-like ratio (average major axis length / average minor axis length) of the non-magnetic iron oxide powder can be more than 1.0. It is preferable to use a non-magnetic iron oxide powder having a small needle-like ratio from the viewpoint of improving the surface smoothness of the non-magnetic layer. From this point, the needle-like ratio (average major axis length / average minor axis length) of the non-magnetic iron oxide powder is preferably 3.0 or less, and more preferably 1.5 or less.
  • ⁇ -iron oxide powder is preferable in one form.
  • the ⁇ -iron oxide is iron oxide whose main phase is the ⁇ phase.
  • the content (filling rate) of the non-magnetic powder in the non-magnetic layer is preferably in the range of 50 to 90% by mass, and more preferably in the range of 60 to 90% by mass.
  • the content of the non-magnetic powder in at least one non-magnetic layer is preferably in the above range, and the content of the non-magnetic powder in more non-magnetic layers is described above. It is more preferably in the range.
  • the non-magnetic layer contains a non-magnetic powder, and can also contain a binder together with the non-magnetic powder.
  • a binder together with the non-magnetic powder.
  • known techniques relating to the non-magnetic layer can be applied.
  • known techniques relating to the magnetic layer can also be applied.
  • Examples of the additive that can be contained in the non-magnetic layer include a dispersant that can contribute to improving the dispersibility of the non-magnetic powder.
  • examples of such dispersants include fatty acids represented by RCOOH (where R is an alkyl group or an alkenyl group) (eg, capric acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, and eridine).
  • the content of the dispersant is preferably 0.2 to 5.0 parts by mass with respect to 100.0 parts by mass of the non-magnetic powder.
  • an organic tertiary amine can be mentioned.
  • paragraphs 0011 to 0018 and 0021 of JP2013-049832A can be referred to.
  • Organic tertiary amines can contribute to improving the dispersibility of carbon black.
  • paragraphs 0022 to 0024 and 0027 of the same publication refer to paragraphs 0022 to 0024 and 0027 of the same publication.
  • the amine is more preferably a trialkylamine.
  • the alkyl group contained in the trialkylamine is preferably an alkyl group having 1 to 18 carbon atoms.
  • the three alkyl groups of the trialkylamine may be the same or different. For details of the alkyl group, refer to paragraphs 0015 to 0016 of JP2013-049832A.
  • As the trialkylamine trioctylamine is particularly preferable.
  • the non-magnetic layer includes not only the non-magnetic powder but also a substantially non-magnetic layer containing a small amount of ferromagnetic powder, for example, as an impurity or intentionally.
  • the substantially non-magnetic layer means that the residual magnetic flux density of this layer is 10 mT or less, the coercive force is 7.96 kA / m (100 Oe) or less, or the residual magnetic flux density is 10 mT or less. It refers to a layer having a coercive force of 7.96 kA / m (100 Oe) or less.
  • the non-magnetic layer preferably has no residual magnetic flux density and coercive force.
  • Non-magnetic support examples include known biaxially stretched polyethylene terephthalates, polyethylene naphthalates, polyamides, polyamideimides, aromatic polyamides and the like. Among these, polyethylene terephthalate, polyethylene naphthalate and polyamide are preferable. These supports may be subjected to corona discharge, plasma treatment, easy adhesion treatment, heat treatment and the like in advance.
  • the magnetic recording medium may or may not have a backcoat layer containing non-magnetic powder on the surface side opposite to the surface side having the magnetic layer of the non-magnetic support.
  • the backcoat layer preferably contains one or both of carbon black and inorganic powder.
  • the backcoat layer can contain binders and can also contain additives.
  • known techniques relating to the backcoat layer can be applied, and known techniques relating to the formulation of the magnetic layer and / or the non-magnetic layer can also be applied.
  • paragraphs 0018 to 0020 of JP-A-2006-331625 and the description of US Pat. No. 7,029,774, column 4, lines 65 to 5, line 38 can be referred to for the backcoat layer. ..
  • the thickness (total thickness) of the magnetic recording medium With regard to the thickness (total thickness) of the magnetic recording medium, with the enormous increase in the amount of information in recent years, the magnetic recording medium is required to have an increased recording capacity (higher capacity). As a means for increasing the capacity, the thickness of the magnetic recording medium may be reduced (hereinafter, also referred to as “thinning”), and the length of the magnetic tape accommodated in one magnetic tape cartridge may be increased. .. From this point, the thickness (total thickness) of the magnetic recording medium is preferably 5.6 ⁇ m or less, more preferably 5.5 ⁇ m or less, and even more preferably 5.4 ⁇ m or less. It is more preferably 3 ⁇ m or less, and even more preferably 5.2 ⁇ m or less. Further, from the viewpoint of ease of handling, the thickness of the magnetic recording medium is preferably 3.0 ⁇ m or more, and more preferably 3.5 ⁇ m or more.
  • the thickness (total thickness) of the magnetic tape can be measured by the following method. Ten tape samples (for example, 5 to 10 cm in length) are cut out from an arbitrary part of the magnetic tape, and these tape samples are stacked and the thickness is measured. The value obtained by dividing the measured thickness by 1/10 (thickness per tape sample) is defined as the tape thickness. The thickness measurement can be performed using a known measuring instrument capable of measuring the thickness on the order of 0.1 ⁇ m.
  • the thickness of the non-magnetic support is preferably 3.0 to 5.0 ⁇ m.
  • the thickness of the magnetic layer can be optimized by the saturation magnetization amount of the magnetic head used, the head gap length, the band of the recording signal, etc., and is generally 0.01 ⁇ m to 0.15 ⁇ m, from the viewpoint of high-density recording. It is preferably 0.02 ⁇ m to 0.12 ⁇ m, and more preferably 0.03 ⁇ m to 0.1 ⁇ m.
  • the magnetic layer may be at least one layer, and the magnetic layer may be separated into two or more layers having different magnetic properties, and a known configuration relating to a multi-layer magnetic layer can be applied. The thickness of the magnetic layer when separated into two or more layers is the total thickness of these layers. This point also applies to the thickness of the non-magnetic layer in the magnetic recording medium having the plurality of non-magnetic layers.
  • the difference in thickness tends to increase and the surface of the non-magnetic layer tends to become rough.
  • the surface smoothness of the non-magnetic layer is high, and from this viewpoint, the thickness of the non-magnetic layer is 1.5 ⁇ m or less.
  • the thickness of the non-magnetic layer is preferably 0.05 ⁇ m or more, more preferably 0.1 ⁇ m or more, from the viewpoint of improving the uniformity of coating of the composition for forming the non-magnetic layer.
  • the thickness of the backcoat layer is preferably 0.9 ⁇ m or less, more preferably 0.1 to 0.7 ⁇ m.
  • Various thicknesses such as the thickness of the magnetic layer can be obtained by the following methods. After exposing the cross section of the magnetic recording medium in the thickness direction with an ion beam, the cross section of the exposed cross section is observed with a scanning electron microscope. Various thicknesses can be obtained as the arithmetic mean of the thicknesses obtained at any two points in the cross-sectional observation. Alternatively, various thicknesses can be obtained as design thicknesses calculated from manufacturing conditions and the like.
  • the step of preparing the composition for forming the magnetic layer, the non-magnetic layer or the backcoat layer usually includes at least a kneading step, a dispersion step, and a mixing step provided before and after these steps as necessary. Can be done. Each process may be divided into two or more stages. The components used in the preparation of each layer-forming composition may be added at the beginning or in the middle of any step.
  • the solvent one kind or two or more kinds of various solvents usually used for producing a coating type magnetic recording medium can be used.
  • paragraph 0153 of JP-A-2011-216149 can be referred to.
  • the individual components may be added separately in two or more steps.
  • the binder may be divided and added in a kneading step, a dispersion step and a mixing step for adjusting the viscosity after dispersion.
  • known manufacturing techniques can be used in various steps.
  • the kneading step it is preferable to use an open kneader, a continuous kneader, a pressurized kneader, an extruder or the like having a strong kneading force.
  • a known disperser can be used.
  • Filtration may be performed by a known method at any stage of preparing each layer-forming composition. Filtration can be performed, for example, by filter filtration.
  • a filter having a pore size of 0.01 to 3 ⁇ m for example, a glass fiber filter, a polypropylene filter, etc.
  • a filter having a pore size of 0.01 to 3 ⁇ m for example, a glass fiber filter, a polypropylene filter, etc.
  • the magnetic layer can be formed by directly applying the composition for forming a magnetic layer on the surface of a non-magnetic support, or by applying multiple layers sequentially or simultaneously with the composition for forming a non-magnetic layer.
  • the composition for forming the backcoat layer is placed on the opposite side of the surface having the non-magnetic layer and / or the magnetic layer of the non-magnetic support (or the non-magnetic layer and / or the magnetic layer is additionally provided). It can be formed by applying it to the surface.
  • the coating for forming each layer refer to paragraph 0066 of Japanese Patent Application Laid-Open No. 2010-231843.
  • various treatments such as a drying treatment, a magnetic layer orientation treatment, and a surface smoothing treatment (calendar treatment) can be performed.
  • known techniques such as paragraphs 0052 to 0057 of JP-A-2010-24113 can be referred to.
  • the coating layer of the composition for forming a magnetic layer can be subjected to an orientation treatment while the coating layer is in a wet state.
  • Various known techniques such as the description in paragraph 0067 of JP-A-2010-231843 can be applied to the alignment treatment.
  • the vertical alignment treatment can be performed by a known method such as a method using a magnet opposite to the opposite pole.
  • the drying rate of the coating layer can be controlled by the temperature and air volume of the drying air and / or the transport speed of the non-magnetic support forming the coating layer in the alignment zone.
  • the coating layer may be pre-dried before being transported to the alignment zone.
  • the calendar treatment when the calendar conditions are strengthened, the value of Half-Rq on the surface of the magnetic layer tends to decrease. Examples of the calendar conditions include the number of times the calendar treatment is performed (hereinafter, also referred to as “number of calendars”), the calendar pressure, the calendar temperature (surface temperature of the calendar roll), the calendar speed, the hardness of the calendar roll, and the like. The more calendars you have, the stronger the calendaring process.
  • the calendar pressure (linear pressure) can be 200 to 500 kg / cm, preferably 250 to 350 kg / cm.
  • the calendar temperature surface temperature of the calendar roll
  • the calendar speed can be, for example, 50-300 m / min, 50-. It is preferably 200 m / min.
  • the obtained magnetic recording medium raw material is cut (slit) by a known cutting machine to, for example, the width of the magnetic tape to be wound around the magnetic tape cartridge.
  • a servo pattern is usually formed on the magnetic recording medium obtained by slitting. The details of the servo pattern will be described later.
  • the magnetic recording medium can be a magnetic tape manufactured through the following heat treatment. Further, in another embodiment, the magnetic recording medium can be a magnetic tape manufactured without undergoing the following heat treatment.
  • a magnetic tape that has been slit and cut to a width determined according to the standard can be wound around a core-shaped member, and the heat treatment can be performed in the wound state.
  • the heat treatment is performed with the magnetic tape wound around a core-shaped member for heat treatment (hereinafter referred to as “heat treatment winding core”), and the heat-treated magnetic tape is wound around a reel of a magnetic tape cartridge.
  • heat treatment winding core a core-shaped member for heat treatment
  • a magnetic tape cartridge in which a magnetic tape is wound on a reel can be manufactured.
  • the heat treatment core can be made of metal, resin, paper, or the like.
  • the material of the core for heat treatment is preferably a material having high rigidity from the viewpoint of suppressing the occurrence of winding failure such as spoking. From this point, the heat treatment core is preferably made of metal or resin.
  • the flexural modulus of the material of the heat treatment core is preferably 0.2 GPa (gigapascal) or more, and more preferably 0.3 GPa or more.
  • the flexural modulus of the material of the heat treatment core is preferably 250 GPa or less.
  • the flexural modulus is a value measured according to ISO (International Organization for Standardization) 178, and the flexural modulus of various materials is known.
  • the heat treatment winding core can be a solid or hollow core-shaped member.
  • the wall thickness is preferably 2 mm or more from the viewpoint of maintaining rigidity.
  • the heat treatment core may or may not have a flange.
  • the length of the magnetic tape wound around the heat treatment core is longer than the final product length, and from the viewpoint of ease of winding around the heat treatment core or the like, it is preferably "final product length + ⁇ ". This ⁇ is preferably 5 m or more from the viewpoint of ease of winding.
  • the tension at the time of winding to the heat treatment core is preferably 0.1 N (Newton) or more. Further, from the viewpoint of suppressing the occurrence of excessive deformation, the tension at the time of winding to the heat treatment winding core is preferably 1.5 N or less, more preferably 1.0 N or less.
  • the outer diameter of the heat treatment core is preferably 20 mm or more, more preferably 40 mm or more, from the viewpoint of ease of winding and suppression of coiling (curl in the longitudinal direction).
  • the outer diameter of the heat treatment core is preferably 100 mm or less, more preferably 90 mm or less.
  • the width of the heat treatment core may be equal to or larger than the width of the magnetic tape wound around the core.
  • the magnetic tape can be wound around the reel of the magnetic tape cartridge while maintaining the relationship between the inside and the outside of the magnetic tape with respect to the heat treatment core during the heat treatment.
  • the length of "+ ⁇ " may be cut off at an arbitrary stage.
  • the magnetic tape for the final product length may be wound from the temporary winding core to the reel of the magnetic tape cartridge, and the remaining “+ ⁇ ” length may be cut off.
  • the ⁇ is preferably 20 m or less.
  • the atmospheric temperature at which the heat treatment is performed (hereinafter, referred to as “heat treatment temperature”) is preferably 40 ° C. or higher, more preferably 50 ° C. or higher.
  • the heat treatment temperature is preferably 75 ° C. or lower, more preferably 70 ° C. or lower, and even more preferably 65 ° C. or lower.
  • the weight absolute humidity of the atmosphere in which the heat treatment is performed is preferably 0.1 g / kg Dry air or more, and more preferably 1 g / kg Dry air or more.
  • Atmospheres with a weight absolute humidity in the above range are preferable because they can be prepared without using a special device for reducing moisture.
  • the weight absolute humidity is preferably 70 g / kg Dry air or less, and more preferably 66 g / kg Dry air or less, from the viewpoint of suppressing the occurrence of dew condensation and deterioration of workability.
  • the heat treatment time is preferably 0.3 hours or more, more preferably 0.5 hours or more.
  • the heat treatment time is preferably 48 hours or less from the viewpoint of production efficiency.
  • the magnetic recording medium can be a tape-shaped magnetic recording medium (that is, a magnetic tape) or a disk-shaped magnetic recording medium (that is, a magnetic disk).
  • the magnetic layer can have a servo pattern.
  • "Formation of servo pattern” can also be referred to as "recording of servo signal”.
  • the formation of the servo pattern will be described using a magnetic tape as an example.
  • the servo pattern is usually formed along the longitudinal direction of the magnetic tape.
  • Examples of the control (servo control) method using a servo signal include timing-based servo (TBS), amplified servo, frequency servo, and the like.
  • the timing-based servo method is adopted in the magnetic tape (generally called "LTO tape") compliant with the LTO (Linear Tape-Open) standard. ing.
  • the servo pattern is composed of a pair of magnetic stripes (also referred to as “servo stripes”) that are non-parallel to each other and are continuously arranged in a plurality in the longitudinal direction of the magnetic tape.
  • the "timing-based servo pattern” refers to a servo pattern that enables head tracking in a timing-based servo system servo system.
  • the reason why the servo pattern is composed of a pair of magnetic stripes that are non-parallel to each other is to teach the passing position to the servo signal reading element passing on the servo pattern.
  • the pair of magnetic stripes described above are formed so that their spacing changes continuously along the width direction of the magnetic tape, and the servo signal reading element reads the spacing to obtain a servo pattern.
  • the relative position of the servo signal reading element can be known. This relative position information allows tracking of the data track. Therefore, a plurality of servo tracks are usually set on the servo pattern along the width direction of the magnetic tape.
  • the servo band is composed of a servo pattern that is continuous in the longitudinal direction of the magnetic tape.
  • a plurality of these servo bands are usually provided on the magnetic tape. For example, in LTO tape, the number is five.
  • the area sandwiched between two adjacent servo bands is the data band.
  • the data band is composed of a plurality of data tracks, and each data track corresponds to each servo track.
  • each servo band has information indicating a servo band number (“servo band ID (identification)” or “UDIM (Unique DataBand Identification)”. It is also called "Servo) information”.) Is embedded.
  • the servo band ID is recorded by shifting a specific pair of servo stripes in the servo band so that their positions are relatively displaced in the longitudinal direction of the magnetic tape. Specifically, the method of shifting a specific pair of servo stripes is changed for each servo band. As a result, the recorded servo band ID becomes unique for each servo band, so that the servo band can be uniquely identified by simply reading one servo band with the servo signal reading element.
  • a method for uniquely specifying the servo band there is also a method using a staggered method as shown in ECMA-319 (June 2001).
  • a staggered method a group of a pair of magnetic stripes (servo stripes) that are continuously arranged in the longitudinal direction of the magnetic tape and are non-parallel to each other are recorded so as to be shifted in the longitudinal direction of the magnetic tape for each servo band. do. Since this combination of shifting methods between adjacent servo bands is unique in the entire magnetic tape, it is possible to uniquely identify the servo band when reading the servo pattern by the two servo signal reading elements. It is possible.
  • LPOS Longitorial Position
  • the embedded information may be different for each servo band such as UDIM information, or may be common to all servo bands such as LPOS information.
  • a method of embedding information in the servo band a method other than the above can be adopted. For example, a predetermined code may be recorded by thinning out a predetermined pair from a group of a pair of servo stripes.
  • the servo pattern forming head is called a servo light head.
  • the servo light head usually has a pair of gaps corresponding to the pair of magnetic stripes as many as the number of servo bands.
  • a core and a coil are connected to each pair of gaps, and by supplying a current pulse to the coil, a magnetic field generated in the core can generate a leakage magnetic field in the pair of gaps.
  • the magnetic pattern corresponding to a pair of gaps is transferred to the magnetic tape by inputting a current pulse while running the magnetic tape on the servo light head to form the servo pattern. Can be done.
  • the width of each gap can be appropriately set according to the density of the formed servo pattern.
  • the width of each gap can be set to, for example, 1 ⁇ m or less, 1 to 10 ⁇ m, 10 ⁇ m or more, and the like.
  • the magnetic tape is usually demagnetized (erase).
  • This erasing process can be performed by applying a uniform magnetic field to the magnetic tape using a DC magnet or an AC magnet.
  • the erase processing includes DC (Direct Current) erase and AC (Alternating Current) erase.
  • AC erase is performed by gradually reducing the strength of the magnetic field while reversing the direction of the magnetic field applied to the magnetic tape.
  • DC erase is performed by applying a unidirectional magnetic field to the magnetic tape.
  • the first method is horizontal DC erase, which applies a unidirectional magnetic field along the longitudinal direction of the magnetic tape.
  • the second method is vertical DC erase, which applies a unidirectional magnetic field along the thickness direction of the magnetic tape.
  • the erasing process may be performed on the entire magnetic tape or may be performed on each servo band of the magnetic tape.
  • the direction of the magnetic field of the formed servo pattern is determined by the direction of erase. For example, when the magnetic tape is subjected to horizontal DC erase, the servo pattern is formed so that the direction of the magnetic field is opposite to the direction of the erase. As a result, the output of the servo signal obtained by reading the servo pattern can be increased. As shown in Japanese Patent Application Laid-Open No. 2012-53940, when a magnetic pattern using the above gap is transferred to a vertically DC-erased magnetic tape, the formed servo pattern is read and obtained. The servo signal has a unipolar pulse shape. On the other hand, when the magnetic pattern is transferred to the horizontally DC-erased magnetic tape using the gap, the servo signal obtained by reading the formed servo pattern has a bipolar pulse shape.
  • dimensional information in the width direction of the traveling magnetic tape is acquired by using a servo signal, and the tension applied in the longitudinal direction of the magnetic tape is adjusted and changed according to the acquired dimensional information. Allows you to control the widthwise dimensions of the magnetic tape. Performing such tension adjustment prevents the magnetic head for recording or reproducing data from being displaced from the target track position during recording or reproduction due to the width deformation of the magnetic tape, and recording or reproducing the data. Can contribute to suppression.
  • the magnetic recording medium can be a magnetic tape.
  • One aspect of the present invention relates to a magnetic tape cartridge containing the magnetic tape.
  • the magnetic tape In a magnetic tape cartridge, the magnetic tape is generally housed inside the cartridge body in a state of being wound on a reel.
  • the reel is rotatably provided inside the cartridge body.
  • a single reel type magnetic tape cartridge having one reel inside the cartridge main body and a twin reel type magnetic tape cartridge having two reels inside the cartridge main body are widely used.
  • the magnetic tape is pulled out from the magnetic tape cartridge and wound on the reel on the magnetic tape device side. Taken.
  • a magnetic head is arranged in the magnetic tape transport path from the magnetic tape cartridge to the take-up reel.
  • the magnetic tape is sent out and wound between the reel (supply reel) on the magnetic tape cartridge side and the reel (winding reel) on the magnetic tape device side. During this time, the magnetic head and the surface of the magnetic layer of the magnetic tape come into contact with each other and slide, so that data can be recorded and / or reproduced.
  • both the supply reel and the take-up reel are provided inside the magnetic tape cartridge.
  • Magnetic recording / playback device One aspect of the present invention relates to a magnetic recording / reproducing device including a magnetic recording medium.
  • the recording of data on the magnetic recording medium and / or the reproduction of the data recorded on the magnetic recording medium are performed by bringing the surface of the magnetic layer of the magnetic recording medium into contact with the magnetic head. It can be done by moving it.
  • Such a form of magnetic recording / reproduction device is generally called a sliding drive or a contact sliding drive.
  • the magnetic head records data on a magnetic recording medium and / or data recorded on a magnetic recording medium in a non-contact state, except in the case of random contact with the surface of the magnetic layer. Play back.
  • Such a form of magnetic recording / reproduction device is generally called a levitation type drive.
  • the magnetic recording / reproducing device can be a sliding drive in one form and a floating drive in another form.
  • the "magnetic recording / reproduction device” means an apparatus capable of recording data on a magnetic recording medium and reproducing data recorded on the magnetic recording medium. do. Such a device is commonly referred to as a drive.
  • the magnetic head included in the magnetic recording / reproducing device can be a recording head capable of recording data on a magnetic recording medium, and can reproduce data recorded on the magnetic recording medium. Can also be.
  • the magnetic recording / reproducing device may include both a recording head and a reproducing head as separate magnetic heads.
  • the magnetic head included in the magnetic tape device may have a configuration in which both a recording element and a reproducing element are provided in one magnetic head.
  • a magnetic head including a magnetoresistive (MR; Magnetoresistive) element capable of reading information recorded on a magnetic recording medium with high sensitivity
  • MR head various known MR heads (for example, GMR (Giant Magnetoresistive) head, TMR (Tunnel Magnetorestive) head, etc.) can be used.
  • the magnetic head that records data and / or reproduces data may include a servo signal reading element.
  • the magnetic tape device may include a magnetic head (servohead) provided with a servo signal reading element as a head separate from the magnetic head that records and / or reproduces data.
  • a magnetic head that records data and / or reproduces recorded data can include two servo signal reading elements, and two servo signal reading elements. Each of the two servo bands adjacent to each other with the data band in between can be read at the same time. One or more data elements can be arranged between the two servo signal reading elements. Elements for recording data (recording elements) and elements for reproducing data (reproduction elements) are collectively referred to as "data elements”.
  • tracking using a servo signal can be performed first. That is, by making the servo signal reading element follow a predetermined servo track, the data element can be controlled to pass on the target data track. The movement of the data track is performed by changing the servo track read by the servo signal reading element in the tape width direction.
  • the recording / playback head can also record and / or play back to other data bands. In that case, the servo signal reading element may be moved to a predetermined servo band by using the UDIM information described above, and tracking for the servo band may be started.
  • FIG. 1 shows an example of arrangement of a data band and a servo band.
  • a plurality of servo bands 1 are arranged on the magnetic layer of the magnetic tape MT so as to be sandwiched between the guide bands 3.
  • a plurality of regions 2 sandwiched between the two servo bands are data bands.
  • the servo pattern is a magnetization region, which is formed by magnetizing a specific region of the magnetic layer with a servo light head. The region magnetized by the servo light head (the position where the servo pattern is formed) is defined by the standard.
  • the servo frame SF on the servo band 1 is composed of the servo subframe 1 (SSF1) and the servo subframe 2 (SSF2).
  • the servo subframe 1 is composed of an A burst (reference numeral A in FIG. 2) and a B burst (reference numeral B in FIG. 2).
  • the A burst is composed of servo patterns A1 to A5, and the B burst is composed of servo patterns B1 to B5.
  • the servo subframe 2 is composed of a C burst (reference numeral C in FIG. 2) and a D burst (reference numeral D in FIG. 2).
  • the C burst is composed of servo patterns C1 to C4, and the D burst is composed of servo patterns D1 to D4.
  • Such 18 servo patterns are arranged in a set of 5 and 4 in a subframe arranged in an array of 5, 5, 4, 4, and used to identify the servo frame.
  • FIG. 2 shows one servo frame for illustration. However, in reality, a plurality of servo frames are arranged in the traveling direction in each servo band on the magnetic layer of the magnetic tape on which the head tracking of the timing-based servo method is performed. In FIG. 2, the arrow indicates the traveling direction.
  • an LTO Ultra format tape usually has a servo frame of 5000 or more per 1 m of tape length in each servo band of the magnetic layer.
  • the magnetic recording medium is treated as a removable medium (so-called replaceable medium), and for example, a magnetic tape cartridge containing a magnetic tape is inserted into the magnetic recording / playback device and taken out. ..
  • the magnetic recording medium is not treated as a convertible medium, for example, the magnetic tape is wound around a reel of a magnetic recording / playback device provided with a magnetic head, and the magnetic tape is housed in the magnetic recording / playback device. ..
  • the ferromagnetic powder described as "metal” in Table 1 described later is similar to the ferromagnetic powder used in Example 1 of Patent Document 1 (Japanese Unexamined Patent Publication No. 2004-103137) shown above. As a material, an iron-cobalt alloy-based ferromagnetic powder was used.
  • BaFe indicates a hexagonal barium ferrite powder having an average particle size (average plate diameter) of 21 nm.
  • the average particle volume of the various ferromagnetic powders described below is a value obtained by the method described above.
  • the various values related to the particle size of the various powders described below are also the values obtained by the method described above.
  • the anisotropy constant Ku is a value obtained for each ferromagnetic powder by the method described above using a vibration sample magnetometer (manufactured by Toei Kogyo Co., Ltd.).
  • the mass magnetization ⁇ s is a value measured at a magnetic field strength of 15 kOe using a vibration sample magnetometer (manufactured by Toei Kogyo Co., Ltd.).
  • Method for producing ferromagnetic powder ⁇ Method for producing hexagonal strontium ferrite powder> Weigh 1707 g of SrCO 3 , 687 g of H 3 BO 3 , 1120 g of Fe 2 O 3 , 45 g of Al (OH) 3 , 24 g of BaCO 3 , 13 g of CaCO 3 , and 235 g of Nd 2 O 3 with a mixer. The mixture was mixed to obtain a raw material mixture.
  • the obtained raw material mixture was melted in a platinum crucible at a melting temperature of 1390 ° C., and the hot water outlet provided at the bottom of the platinum crucible was heated while stirring the melt, so that the melt was discharged into a rod shape at about 6 g / sec. ..
  • the hot water was rolled and rapidly cooled with a water-cooled twin roller to prepare an amorphous body. 280 g of the prepared amorphous body was charged into an electric furnace, the temperature was raised to 635 ° C (crystallization temperature) at a heating rate of 3.5 ° C / min, and the temperature was maintained at the same temperature for 5 hours to obtain hexagonal strontium ferrite particles. It was precipitated (crystallized).
  • the crystallized product obtained above containing hexagonal strontium ferrite particles was coarsely pulverized in a mortar, 1000 g of zirconia beads having a particle size of 1 mm and 800 ml of an aqueous acetic acid solution having a concentration of 1% were added to a glass bottle, and dispersion treatment was performed for 3 hours with a paint shaker. Was done. Then, the obtained dispersion was separated from the beads and placed in a stainless steel beaker. The dispersion is allowed to stand at a liquid temperature of 100 ° C. for 3 hours to dissolve the glass components, then settled in a centrifuge and decanted repeatedly for cleaning. It was dried for a time to obtain a hexagonal strontium ferrite powder.
  • the hexagonal strontium ferrite powder (“SrFe” in Table 1 below) obtained above has an average particle volume of 900 nm 3 , anisotropy constant Ku of 2.2 ⁇ 105 J / m 3 , and mass magnetization ⁇ s. It was 49 A ⁇ m 2 / kg. 12 mg of a sample powder was collected from the hexagonal strontium ferrite powder obtained above, and the sample powder was partially dissolved under the dissolution conditions exemplified above to perform elemental analysis of the filtrate obtained by using an ICP analyzer. The content of the surface layer was determined.
  • ⁇ Method of producing ⁇ -iron oxide powder In 90 g of pure water, 8.3 g of iron (III) nitrate 9 hydrate, 1.3 g of gallium nitrate (III) octahydrate, 190 mg of cobalt (II) nitrate hexahydrate, 150 mg of titanium (IV) sulfate, and While stirring 1.5 g of polyvinylpyrrolidone (PVP) dissolved in it using a magnetic stirrer, 4.0 g of an aqueous ammonia solution having a concentration of 25% was added in an atmospheric atmosphere under the condition of an atmospheric temperature of 25 ° C. The mixture was stirred for 2 hours under the temperature condition of 25 ° C.
  • PVP polyvinylpyrrolidone
  • a citric acid solution obtained by dissolving 1 g of citric acid in 9 g of pure water was added, and the mixture was stirred for 1 hour.
  • the powder precipitated after stirring was collected by centrifugation, washed with pure water, and dried in a heating furnace having a furnace temperature of 80 ° C. 800 g of pure water was added to the dried powder, and the powder was dispersed in water again to obtain a dispersion liquid.
  • the temperature of the obtained dispersion was raised to 50 ° C., and 40 g of a 25% aqueous ammonia solution was added dropwise with stirring.
  • TEOS tetraethoxysilane
  • the precursor of the heat-treated ferromagnetic powder was put into a 4 mol / L aqueous solution of sodium hydroxide (NaOH), and the liquid temperature was maintained at 70 ° C. and stirred for 24 hours to prepare the precursor of the heat-treated ferromagnetic powder.
  • the caustic compound which is an impurity, was removed from the material. Then, the ferromagnetic powder from which the silicic acid compound was removed was collected by centrifugation and washed with pure water to obtain a ferromagnetic powder.
  • the composition of the obtained ferromagnetic powder was confirmed by high frequency inductively coupled plasma emission spectroscopy (ICP-OES; Inductively Coupled Plasma-Optical Operation Spectroscopy) and found to be Ga, Co and Ti substituted ⁇ -iron oxide ( ⁇ -Ga 0 ). It was .28 Co 0.05 Ti 0.05 Fe 1.62 O 3 ). Further, X-ray diffraction analysis was performed under the same conditions as those described above for the method for producing hexagonal strontium ferrite powder, and the ferromagnetic powder obtained from the peak of the X-ray diffraction pattern was of ⁇ phase and ⁇ phase.
  • ICP-OES Inductively Coupled Plasma-Optical Operation Spectroscopy
  • the average particle volume of the obtained ⁇ -iron oxide powder (“ ⁇ -iron oxide” in Table 1 below) is 750 nm 3
  • the anisotropic constant Ku is 1.2 ⁇ 105 J / m 3
  • the mass magnetization ⁇ s. was 16 A ⁇ m 2 / kg.
  • Example 1 (1) Preparation of alumina dispersion 3.
  • alumina powder HIT-80 manufactured by Sumitomo Chemical Co., Ltd.
  • BET Brunauer-Emmett-Teller
  • STY-80 manufactured by Sumitomo Chemical Co., Ltd.
  • BET Brunauer-Emmett-Teller
  • composition for forming a magnetic layer Ferromagnetic powder (type: see Table 1) 100.0 parts SO 3 Na group-containing polyurethane resin 14.0 parts Weight average molecular weight: 70,000, SO 3 Na group: 0.2 meq / g Cyclohexanone 150.0 parts Methyl ethyl ketone 150.0 parts (abrasive solution) 6.0 parts of alumina dispersion prepared in (1) above (projection forming agent solution) Protrusion forming agent See Table 1 Type: Colloidal silica (average particle size 120 nm) Methyl ethyl ketone 1.4 parts (other ingredients) Stearic acid 2.0 parts Stearic acid amide 0.2 parts Butyl stearate 2.0 parts Polyisocyanate (Tosoh Coronate (registered trademark) L) 2.5 parts (finishing additive solvent) Cyclohexanone 200.0 parts Methyl ethyl ketone 200.0 parts
  • Non-magnetic inorganic powder ⁇ -iron oxide 100.0 parts Average particle size (average major axis length): 0.15 ⁇ m Needle ratio: 7 BET specific surface area: 52m 2 / g Carbon black 20.0 parts Average particle size: 20nm SO 3 Na group-containing polyurethane resin 18.0 parts Weight average molecular weight: 70,000, SO 3 Na group: 0.2 meq / g Stearic acid 2.0 parts Stearic acid amide 0.2 parts Butyl stearate 2.0 parts Cyclohexanone 300.0 parts Methyl ethyl ketone 300.0 parts
  • composition for forming a magnetic layer was prepared by the following method.
  • the above magnetic liquid was prepared by dispersing each component for 24 hours (bead dispersion) using a batch type vertical sand mill.
  • the dispersed beads zirconia beads having a bead diameter of 0.5 mm were used.
  • the prepared magnetic solution, the above abrasive solution and other components are mixed and bead-dispersed for 5 minutes, and then a batch type ultrasonic device (20 kHz, 300 W). The treatment (ultrasonic dispersion) was carried out for 0.5 minutes.
  • a composition for forming a non-magnetic layer was prepared by the following method.
  • the above components excluding the lubricants (stearic acid, stearic acid amide and butyl stearate) were kneaded and diluted with an open kneader, and then dispersed with a horizontal bead mill disperser.
  • a lubricant stearic acid, stearic acid amide and butyl stearate
  • the composition for forming the back coat layer was prepared by the following method.
  • the above components excluding polyisocyanate were introduced into a dissolver stirrer, stirred at a peripheral speed of 10 m / sec for 30 minutes, and then dispersed by a horizontal bead mill disperser. Then, polyisocyanate was added, and the mixture was stirred and mixed with a dissolver stirrer to prepare a composition for forming a backcoat layer.
  • a magnetic field having a magnetic field strength of 0.3 T is applied in the direction perpendicular to the surface of the coated layer to perform a vertical alignment treatment, and then drying. And formed a magnetic layer.
  • the composition for forming the back coat layer prepared in (5) above so that the thickness after drying is 0.3 ⁇ m is applied. It was applied and dried to form a backcoat layer.
  • a surface smoothing treatment (calender treatment) is performed at a speed of 100 m / min, a linear pressure of 300 kg / cm, and a calendar temperature of 90 ° C. (the surface temperature of the calendar roll).
  • a calendar temperature 90 ° C. (the surface temperature of the calendar roll).
  • the raw magnetic tape was stored in a heat treatment furnace having an atmospheric temperature of 70 ° C. for heat treatment (heat treatment time: 36 hours). After the heat treatment, slits were made to a width of 1/2 inch to obtain a magnetic tape.
  • a servo signal on the magnetic layer of the obtained magnetic tape By recording a servo signal on the magnetic layer of the obtained magnetic tape with a commercially available servo writer, it has a data band, a servo band, and a guide band in an arrangement according to the LTO (Linear Tape-Open) Ultra format, and has a servo.
  • a magnetic tape having a servo pattern (timing-based servo pattern) arranged and shaped according to the LTO Ultra format on the band was obtained.
  • the servo pattern thus formed is a servo pattern according to JIS (Japanese Industrial Standards) X6175: 2006 and Standard ECMA-319 (June 2001).
  • the total number of servo bands is 5, and the total number of data bands is 4.
  • the magnetic tape (length 970 m) after forming the servo pattern was wound around a core for heat treatment, and the heat treatment was performed in a state of being wound around the core.
  • a core for heat treatment a resin-made solid core member (outer diameter: 50 mm) having a flexural modulus of 0.8 GPa was used, and the tension at the time of winding was 0.6 N.
  • the heat treatment was performed at a heat treatment temperature of 50 ° C. for 5 hours.
  • the weight absolute humidity of the heat-treated atmosphere was 10 g / kg Dry air.
  • the magnetic tape is removed from the heat treatment core, wound around the temporary winding core, and then the magnetic tape cartridge (from the temporary winding core).
  • a solid core-shaped member made of the same material as the winding core for heat treatment and having the same outer diameter was used, and the tension at the time of winding was 0.6N.
  • a single reel type magnetic tape cartridge of Example 1 in which a magnetic tape having a length of 960 m was wound on a reel was produced.
  • Example 2 A magnetic tape and a magnetic tape cartridge were produced in the same manner as in Example 1 except that the calendar temperature was set to the temperature shown in Table 1.
  • Example 3 A magnetic tape and a magnetic tape cartridge were produced in the same manner as in Example 1 except that the amount of carbon black (average particle size: 20 nm) shown in Table 1 was used as the protrusion forming agent.
  • Example 4 Two non-magnetic layers are formed as shown below, and the magnetic layer forming composition is applied onto the formed upper non-magnetic layer in the same manner as in Example 1 to form the magnetic layer and the number of calendars is once.
  • a magnetic tape and a magnetic tape cartridge were produced in the same manner as in Example 1.
  • composition for forming lower non-magnetic layer Carbon black (average particle size: 20 nm) 100.0 parts Trioctylamine 4.0 parts Vinyl chloride resin 12.0 parts Stearic acid 1.5 parts Stearic acid amide 0.3 parts Butyl stearate 1.5 parts Cyclohexanone 200. 0 parts Methyl ethyl ketone 510.0 parts
  • Non-magnetic inorganic powder ⁇ -iron oxide 100.0 parts Average particle size (average major axis length): 30 nm Average minor axis length: 15 nm Needle ratio: 2.0 SO 3 Na group-containing polyurethane resin 18.0 parts Weight average molecular weight: 70,000, SO 3 Na group: 0.2 meq / g Stearic acid 1.0 part Cyclohexanone 300.0 part Methyl ethyl ketone 300.0 part
  • each component was kneaded with an open kneader for 240 minutes and then dispersed with a sand mill.
  • the dispersion time was 24 hours, and zirconia beads having a bead diameter of 0.1 mm were used as the dispersed beads.
  • polyisocyanate (Coronate 3041 manufactured by Tosoh Corporation) was added to the dispersion obtained in this manner, and the mixture was further stirred and mixed for 20 minutes, and then filtered using a filter having a pore size of 0.5 ⁇ m.
  • a composition for forming a lower non-magnetic layer and a composition for forming an upper non-magnetic layer were prepared.
  • the composition for forming the lower non-magnetic layer was applied onto one surface of the same support as in Example 1 so that the thickness after drying was 0.25 ⁇ m, and dried in an environment with an ambient temperature of 100 ° C.
  • a lower non-magnetic layer was formed.
  • a composition for forming an upper non-magnetic layer was applied onto the lower non-magnetic layer so that the thickness after drying was 0.25 ⁇ m, and the composition was dried in an environment with an atmospheric temperature of 100 ° C. to form an upper non-magnetic layer.
  • Example 5 A magnetic tape and a magnetic tape cartridge were produced in the same manner as in Example 4, except that the calendar temperature was set to the temperature shown in Table 1.
  • Example 6 As the ferromagnetic powder, a hexagonal strontium ferrite powder (“SrFe” in Table 1) prepared by the method described above was used, and two non-magnetic layers were formed by the same method as in Example 4. A magnetic tape and a magnetic tape cartridge were produced in the same manner as in Example 3, except that the points and the number of calendars were set to 1.
  • Example 7 As the ferromagnetic powder, ⁇ -iron oxide powder (“ ⁇ -iron oxide” in Table 1) produced by the method described above was used, and two non-magnetic layers were used in the same manner as in Example 4. The magnetic tape and the magnetic tape cartridge were produced in the same manner as in Example 3 except that the points where the above was formed and the number of times of calendering was set to 1.
  • Example 1 A magnetic tape and a magnetic tape cartridge were produced in the same manner as in Example 1 except that the amount of colloidal silica added as a component of the composition for forming a magnetic layer was set to the amount shown in Table 1 and the number of calendars was set to 1.
  • Example 3 In order to prepare a magnetic tape similar to Example 1 of Patent Document 1 (Japanese Unexamined Patent Publication No. 2004-103137) shown above, the magnetic tape shown in Table 1 was used as the ferromagnetic powder, and no protrusion forming agent was added. The same as in Example 1 except that a magnetic layer is formed on the surface, a composition for forming a non-magnetic layer is applied so that the thickness of the non-magnetic layer after drying is 1.3 ⁇ m, and the number of calenders is one. A magnetic tape and a magnetic tape cartridge were manufactured in.
  • AFM Anascope 4 manufactured by Veeco
  • RTESS-300 manufactured by BRUKER
  • the resolution is 512pixel ⁇ 512pixel
  • the scanning speed is the speed at which one screen (512pixel ⁇ 512pixel) is measured in 341 seconds.
  • Each of the magnetic tape cartridges of Examples and Comparative Examples is attached to a magnetic recording / playback device, the magnetic tape is run under the following running conditions, and a magnetic signal is recorded in the longitudinal direction of the magnetic tape under the following recording / playback conditions and played back. It was reproduced by a head (MR head).
  • the reproduced signal was frequency-analyzed using a spectrum analyzer manufactured by Shibasoku, and the ratio of the output of 300 kfci to the noise integrated in the range of 0 kfci to 600 kfci was defined as SNR (Signal-to-Noise-ratio).
  • the unit kfci is a unit of line recording density (cannot be converted into the SI unit system).
  • the magnetic tape of the example is superior in electromagnetic conversion characteristics to the magnetic tape of the comparative example.
  • the root mean square roughness Rq which is a value calculated including the negative part in addition to the positive part, was obtained according to JIS B 0601: 2013.
  • Rq was obtained in Example 1: 2. It is 0.7 nm, Comparative Example 2: 2.5 nm, and the evaluation result of the electromagnetic conversion characteristics shown in Table 1 is inferior to that of Example 1.
  • the Rq of Comparative Example 2 is smaller than the Rq of Example 1. there were. From the comparison between this result and the result shown in Table 1, it can be confirmed that controlling the value of Half-Rq obtained only from the positive part leads to improvement of the electromagnetic conversion characteristic.
  • One aspect of the present invention is useful in the technical field of magnetic recording media for data storage.

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  • Magnetic Record Carriers (AREA)

Abstract

Provided are a magnetic recording medium having a non-magnetic support and a magnetic layer that includes a ferromagnetic powder, and a magnetic tape cartridge and magnetic recording playback device that include said magnetic recording medium. Half-Rq derived in the surface of the magnetic layer is 3.0 nm or less. The Half-Rq is the root mean square roughness derived for only the positive section of surface profile data obtained by inverse Fourier transformation of components having a frequency of 25 Hz or less in a power spectrum density on the surface of the magnetic layer.

Description

磁気記録媒体、磁気テープカートリッジおよび磁気記録再生装置Magnetic recording medium, magnetic tape cartridge and magnetic recording / playback device
 本発明は、磁気記録媒体、磁気テープカートリッジおよび磁気記録再生装置に関する。 The present invention relates to a magnetic recording medium, a magnetic tape cartridge, and a magnetic recording / playback device.
 各種データを記録するための記録媒体として、磁気記録媒体が広く用いられている(例えば特許文献1参照)。 A magnetic recording medium is widely used as a recording medium for recording various data (see, for example, Patent Document 1).
特開2004-103137号公報Japanese Unexamined Patent Publication No. 2004-103137
 磁気記録媒体には、優れた電磁変換特性を発揮することが求められ、電磁変換特性のより一層の向上が望まれている。 The magnetic recording medium is required to exhibit excellent electromagnetic conversion characteristics, and further improvement of the electromagnetic conversion characteristics is desired.
 磁気記録媒体は、通常、非磁性支持体上に強磁性粉末を含む磁性層を有し、磁気記録媒体の性能には、磁性層の表面形状が影響し得る。磁性層の表面形状に関して、先に示した特許文献1(特開2004-103137号公報)には、パワースペクトラムデンシティーに基づき磁性層の表面形状を制御することが提案されている。これに対し本発明者は、従来提案されていた磁性層の表面形状の制御によって達成され得る電磁変換特性より更に電磁変換特性に優れる磁気記録媒体を提供することを目指した。 The magnetic recording medium usually has a magnetic layer containing a ferromagnetic powder on a non-magnetic support, and the surface shape of the magnetic layer may affect the performance of the magnetic recording medium. Regarding the surface shape of the magnetic layer, Patent Document 1 (Japanese Unexamined Patent Publication No. 2004-103137) described above proposes to control the surface shape of the magnetic layer based on the power spectrum density. On the other hand, the present inventor has aimed to provide a magnetic recording medium having further excellent electromagnetic conversion characteristics than the electromagnetic conversion characteristics that can be achieved by controlling the surface shape of the magnetic layer, which has been conventionally proposed.
 即ち、本発明の一態様は、優れた電磁変換特性を発揮することができる磁気記録媒体を提供することを目的とする。 That is, one aspect of the present invention is to provide a magnetic recording medium capable of exhibiting excellent electromagnetic conversion characteristics.
 本発明の一態様は、
 非磁性支持体と、強磁性粉末を含む磁性層と、を有する磁気記録媒体であって、
 上記磁性層の表面において求められるHalf-Rqは3.0nm以下である磁気記録媒体、
 に関する。上記Half-Rqは、上記磁性層の表面のパワースペクトラムデンシティーについて、周波数25Hz(ヘルツ)以下の成分を逆フーリエ変換して得られた表面プロファイルデータの正の部分のみについて求められた二乗平均粗さである。
One aspect of the present invention is
A magnetic recording medium having a non-magnetic support and a magnetic layer containing a ferromagnetic powder.
A magnetic recording medium having a Half-Rq of 3.0 nm or less required on the surface of the magnetic layer.
Regarding. The above-mentioned Half-Rq is the root mean square roughness obtained only for the positive part of the surface profile data obtained by inverse Fourier transforming the components having a frequency of 25 Hz (hertz) or less with respect to the power spectrum density of the surface of the magnetic layer. That's right.
 一形態では、上記Half-Rqは、0.5nm以上3.0nm以下であることができる。 In one form, the Half-Rq can be 0.5 nm or more and 3.0 nm or less.
 一形態では、上記Half-Rqは、2.0nm以下であることができる。 In one form, the Half-Rq can be 2.0 nm or less.
 一形態では、上記Half-Rqは、0.5nm以上2.0nm以下であることができる。 In one form, the Half-Rq can be 0.5 nm or more and 2.0 nm or less.
 一形態では、上記磁気記録媒体は、上記非磁性支持体と上記磁性層との間に、非磁性粉末を含む非磁性層を少なくとも1層有することができる。 In one form, the magnetic recording medium can have at least one non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer.
 一形態では、上記磁気記録媒体は、上記非磁性層を2層有することができる。 In one form, the magnetic recording medium can have two non-magnetic layers.
 一形態では、上記磁気記録媒体は、上記2層の非磁性層のうちの磁性層側の非磁性層に非磁性酸化鉄粉末を含むことができ、非磁性支持体側の非磁性層にカーボンブラックを含むことができる。 In one form, the magnetic recording medium can contain non-magnetic iron oxide powder in the non-magnetic layer on the magnetic layer side of the two non-magnetic layers, and carbon black in the non-magnetic layer on the non-magnetic support side. Can be included.
 一形態では、上記非磁性酸化鉄粉末は、α-酸化鉄粉末であることができる。 In one form, the non-magnetic iron oxide powder can be α-iron oxide powder.
 一形態では、上記磁気記録媒体は、上記非磁性支持体の上記磁性層を有する表面側とは反対の表面側に、非磁性粉末を含むバックコート層を更に有することができる。 In one embodiment, the magnetic recording medium can further have a backcoat layer containing non-magnetic powder on the surface side of the non-magnetic support opposite to the surface side having the magnetic layer.
 一形態では、上記磁気記録媒体は、磁気テープであることができる。 In one form, the magnetic recording medium can be a magnetic tape.
 本発明の一態様は、上記磁気テープを含む磁気テープカートリッジに関する。 One aspect of the present invention relates to a magnetic tape cartridge containing the above magnetic tape.
 本発明の一態様は、上記磁気記録媒体と、磁気ヘッドと、を含む磁気記録再生装置に関する。 One aspect of the present invention relates to a magnetic recording / reproducing device including the above magnetic recording medium and a magnetic head.
 本発明の一態様によれば、優れた電磁変換特性を発揮することができる磁気記録媒体を提供することができる。また、本発明の一態様によれば、上記磁気記録媒体を含む磁気テープカートリッジおよび磁気記録再生装置を提供することができる。 According to one aspect of the present invention, it is possible to provide a magnetic recording medium capable of exhibiting excellent electromagnetic conversion characteristics. Further, according to one aspect of the present invention, it is possible to provide a magnetic tape cartridge and a magnetic recording / reproducing device including the magnetic recording medium.
データバンドおよびサーボバンドの配置例を示す。An example of arranging the data band and the servo band is shown. LTO(Linear Tape-Open)Ultriumフォーマットテープのサーボパターン配置例を示す。An example of arranging the servo pattern of the LTO (Linear Tape-Open) Ultrium format tape is shown.
[磁気記録媒体]
 本発明の一態様は、非磁性支持体と強磁性粉末を含む磁性層とを有する磁気記録媒体に関する。上記磁気記録媒体において、上記磁性層の表面において求められるHalf-Rqは、3.0nm以下である。上記Half-Rqは、上記磁性層の表面のパワースペクトラムデンシティーについて、周波数25Hz以下の成分を逆フーリエ変換して得られた表面プロファイルデータの正の部分のみについて求められた二乗平均粗さである。
[Magnetic recording medium]
One aspect of the present invention relates to a magnetic recording medium having a non-magnetic support and a magnetic layer containing a ferromagnetic powder. In the magnetic recording medium, Half-Rq required on the surface of the magnetic layer is 3.0 nm or less. The Half-Rq is the root mean square roughness obtained only for the positive part of the surface profile data obtained by inverse Fourier transforming the components having a frequency of 25 Hz or less with respect to the power spectrum density of the surface of the magnetic layer. ..
<Half-Rq>
 本発明および本明細書における上記「Half-Rq」は、詳しくは、以下の方法によって求められる値である。
<Half-Rq>
The above-mentioned "Half-Rq" in the present invention and the present specification is, in detail, a value obtained by the following method.
(AFM測定)
 測定対象の磁気記録媒体の磁性層の表面において、原子間力顕微鏡(AFM;Atomic Force Microscope)により測定を行い、AFM画像を取得する。本発明および本明細書において、「磁性層(の)表面」とは、磁気記録媒体の磁性層側表面と同義である。AFM測定において、測定領域は、40μm角(40μm×40μm)の領域とする。測定は、磁性層表面の無作為に選択した3箇所の異なる測定箇所において行う(n=3)。分解能は512pixel×512pixelとする。AFMの測定条件の一例としては、下記の測定条件を挙げることができる。
 AFM(Veeco社製Nanoscope4)をタッピングモードで用いて磁気記録媒体の磁性層の表面の面積40μm×40μmの領域を測定する。探針としてはBRUKER社製RTESP-300を使用し、分解能は512pixel×512pixelとし、スキャン速度は1画面(512pixel×512pixel)を341秒で測定する速度とする。
(AFM measurement)
On the surface of the magnetic layer of the magnetic recording medium to be measured, an atomic force microscope (AFM) is used for measurement, and an AFM image is acquired. In the present invention and the present specification, the "surface of the magnetic layer" is synonymous with the surface of the magnetic recording medium on the magnetic layer side. In the AFM measurement, the measurement area is a 40 μm square (40 μm × 40 μm) area. Measurements are made at three randomly selected different measurement points on the surface of the magnetic layer (n = 3). The resolution is 512pixel × 512pixel. The following measurement conditions can be mentioned as an example of the AFM measurement conditions.
AFM (Nanoscope 4 manufactured by Veeco) is used in a tapping mode to measure a region having an area of 40 μm × 40 μm on the surface of the magnetic layer of the magnetic recording medium. As the probe, RTESS-300 manufactured by BRUKER is used, the resolution is 512pixel × 512pixel, and the scanning speed is the speed at which one screen (512pixel × 512pixel) is measured in 341 seconds.
(PSDの取得)
 「PSD」は、パワースペクトラムデンシティー(Power Spectrum Density)の略称として用いられる。AFM測定によって取得されたAFM画像において、40μm×40μmの測定領域の一辺を512分割して、プロファイリングにおいてsampling ratioを40/512μmとし、表面粗さ曲面に対する2次元フーリエ変換を行い、最長波長40μmから最短波長0.15625μmまでの、合計256個の波長成分のPSDを得る。上記のsampling ratioとは、サンプル点を設定する頻度を意味する。
(Acquisition of PSD)
"PSD" is used as an abbreviation for Power Spectrum Density. In the AFM image acquired by AFM measurement, one side of the measurement area of 40 μm × 40 μm is divided into 512, the sampling ratio is set to 40/512 μm in profiling, two-dimensional Fourier transform is performed on the surface roughness curved surface, and the maximum wavelength is 40 μm. A total of 256 wavelength component PSDs up to the shortest wavelength of 0.15625 μm are obtained. The above-mentioned sampling ratio means the frequency of setting the sample points.
(Half-Rqの算出)
 上記で得られたPSDについて、周波数25Hz以下の成分を逆フーリエ変換して得られた表面プロファイルデータにおいて、正の部分のみについて、下記式により算出を行い、Half-Rqを求める。正の部分とは、基準面に対して凸形状を有する部分(凸部)の高さ値に相当する。基準面とは、凸部と凹部の体積が等しくなる面(高さゼロ)である。Half-Rqは、凸部の高さ値に相当する正の部分のデータ(プラスの値のデータ)も凹部の深さ値に相当する負の部分のデータ(マイナスの値のデータ)も含めてそれらの絶対値から算出される値とは異なり、正の部分のみについて算出を行い求められる値である。そのため、「Half」を付して、Half-Rqと表記することとする。下記式中、「平均高さ」は、高さ値の算術平均であり、「サンプル点高さ」は、サンプル点における高さ値である。こうして3箇所の異なる測定箇所についてそれぞれ算出された値の算術平均を、測定対象の磁気記録媒体の磁性層の表面において求められるHalf-Rqとする。
(Calculation of Half-Rq)
With respect to the PSD obtained above, in the surface profile data obtained by inverse Fourier transforming the components having a frequency of 25 Hz or less, only the positive part is calculated by the following formula to obtain Half-Rq. The positive portion corresponds to the height value of the portion (convex portion) having a convex shape with respect to the reference plane. The reference plane is a plane (height zero) in which the volumes of the convex portion and the concave portion are equal to each other. Half-Rq includes the data of the positive part (positive value data) corresponding to the height value of the convex portion and the data of the negative part (negative value data) corresponding to the depth value of the concave portion. Unlike the value calculated from those absolute values, it is a value obtained by calculating only the positive part. Therefore, "Half" is added and it is expressed as Half-Rq. In the following formula, the "average height" is the arithmetic mean of the height values, and the "sample point height" is the height value at the sample points. The arithmetic mean of the values calculated for each of the three different measurement points is defined as Half-Rq obtained on the surface of the magnetic layer of the magnetic recording medium to be measured.
Figure JPOXMLDOC01-appb-M000001
Figure JPOXMLDOC01-appb-M000001
 具体的なフロー例としては、以下の例を挙げることができる。
 AFM画像(512pixel×512pixel)を取得し、このAFM画像について表面粗さ曲線をフーリエ変換し、周波数成分画像(512pixel×512pixel)を得る。得られた周波数成分画像において、中心部が低周波数成分、周囲が高周波数成分となっていない場合には、シフト演算を行い、中心部が低周波数成分、周囲が高周波数成分となるようにする。中心部の半径25pixel相当の円内の成分に0(ゼロ)を代入する。この際、円内と円外との境界をスムーズ(smooth)にするために、シグモイド関数を用いてもよい。その後、上記でシフト演算を行っていた場合には、再度シフト演算を行う。こうして、周波数25Hz以下の低周波像を得る。得られた低周波像について、上記のようにHalf-Rqを求める。
The following examples can be given as specific flow examples.
An AFM image (512pixel × 512pixel) is acquired, and the surface roughness curve of this AFM image is Fourier transformed to obtain a frequency component image (512pixel × 512pixel). In the obtained frequency component image, if the central part is not a low frequency component and the peripheral part is not a high frequency component, a shift operation is performed so that the central part is a low frequency component and the peripheral part is a high frequency component. .. Substitute 0 (zero) for the component in the circle corresponding to the radius of 25pixel at the center. At this time, a sigmoid function may be used in order to make the boundary between the inside and the outside of the circle smooth. After that, if the shift operation has been performed in the above, the shift operation is performed again. In this way, a low frequency image having a frequency of 25 Hz or less is obtained. For the obtained low frequency image, Half-Rq is obtained as described above.
 上記磁気記録媒体において、先に記載の方法によって求められるHalf-Rqが3.0nm以下であることが、電磁変換特性向上に寄与し得る。以下、この点について更に説明する。
 磁性層の表面形状に関して、磁性層の表面に存在するうねりの形状が電磁変換特性に影響し得ると考えられる。本発明者は、上記のようにPSDにおいて周波数25Hz以下の成分を逆フーリエ変換することによって、PSDによって従来評価されていたうねりと比べて、より長波長のうねりの指標となり得る値を得ることができると考えている。かかる長波長のうねりの周期は、磁性層へのデータの記録および/または磁性層に記録されたデータの再生に通常用いられる磁気ヘッドの磁性層表面との摺動面に存在し得る凹凸の周期と近い周期なのではないかと本発明者は推察している。このことが、先に記載した方法によって求められるHalf-Rqを制御することが、電磁変換特性向上に寄与し得る理由ではないかと本発明者は考えている。加えて、上記Half-Rqは、表面プロファイルデータの正の部分についてのみ、即ち磁性層表面の凸部分に関してのみ、求められる値である。磁性層表面と磁気ヘッドとのスペーシングについては、スペーシングが広いとスペーシングロスによって電磁変換特性は低下する傾向がある。このスペーシングには、磁性層表面の凹凸の中の凸部分が影響するため、上記のように正の部分についてのみ求められるHalf-Rqは、電磁変換特性と良好に相関し得る値であり、この値を3.0nm以下とすることが電磁変換特性の向上につながると本発明者は考えている。
 ただし、上記には推察が含まれる。本明細書に記載の推察に、本発明が限定されない。
In the magnetic recording medium, the fact that Half-Rq obtained by the method described above is 3.0 nm or less can contribute to the improvement of electromagnetic conversion characteristics. Hereinafter, this point will be further described.
Regarding the surface shape of the magnetic layer, it is considered that the shape of the waviness existing on the surface of the magnetic layer may affect the electromagnetic conversion characteristics. The present inventor can obtain a value that can be an index of a swell having a longer wavelength than the swell conventionally evaluated by the PSD by performing an inverse Fourier transform on a component having a frequency of 25 Hz or less in the PSD as described above. I think I can do it. The period of such long-wavelength swell is the period of unevenness that may exist on the sliding surface of the magnetic head that is normally used for recording data on the magnetic layer and / or reproducing the data recorded on the magnetic layer. The present inventor speculates that the cycle is close to that of. The present inventor thinks that this is the reason why controlling Half-Rq obtained by the method described above may contribute to the improvement of electromagnetic conversion characteristics. In addition, the Half-Rq is a value obtained only for the positive part of the surface profile data, that is, only for the convex part of the surface of the magnetic layer. Regarding the spacing between the magnetic layer surface and the magnetic head, if the spacing is wide, the electromagnetic conversion characteristics tend to deteriorate due to the spacing loss. Since the convex portion in the unevenness of the magnetic layer surface affects this spacing, Half-Rq, which is obtained only for the positive portion as described above, is a value that can be well correlated with the electromagnetic conversion characteristics. The present inventor believes that setting this value to 3.0 nm or less leads to improvement in electromagnetic conversion characteristics.
However, the above includes speculation. The inferences described herein are not limited to the present invention.
 電磁変換特性向上の観点から、上記磁気記録媒体の磁性層の表面において求められるHalf-Rqは3.0nm以下であり、2.8nm以下であることが好ましく、2.6nm以下であることがより好ましく、2.4nm以下であることが更に好ましく、2.2nm以下であることが一層好ましく、2.0nm以下であることがより一層好ましく、1.8nm以下であることが更に好ましい。上記磁気記録媒体の磁性層の表面において求められるHalf-Rqは、例えば0.5nm以上、0.7nm以上または1.0nm以上であることができ、ここに例示した値を下回ることもできる。Half-Rqの値が小さいことは、電磁変換特性向上の観点から好ましい。 From the viewpoint of improving the electromagnetic conversion characteristics, the Half-Rq required on the surface of the magnetic layer of the magnetic recording medium is 3.0 nm or less, preferably 2.8 nm or less, and more preferably 2.6 nm or less. It is preferably 2.4 nm or less, more preferably 2.2 nm or less, further preferably 2.0 nm or less, still more preferably 1.8 nm or less. The Half-Rq required on the surface of the magnetic layer of the magnetic recording medium can be, for example, 0.5 nm or more, 0.7 nm or more, or 1.0 nm or more, and can be lower than the values exemplified here. It is preferable that the value of Half-Rq is small from the viewpoint of improving the electromagnetic conversion characteristics.
 磁気記録媒体の磁性層の表面において求められるHalf-Rqの制御については、後述する。 The control of Half-Rq required on the surface of the magnetic layer of the magnetic recording medium will be described later.
 以下、上記磁気記録媒体について、更に詳細に説明する。 Hereinafter, the above magnetic recording medium will be described in more detail.
<磁性層>
(強磁性粉末)
 磁性層に含まれる強磁性粉末としては、各種磁気記録媒体の磁性層において用いられる強磁性粉末として公知の強磁性粉末を一種または二種以上組み合わせて使用することができる。強磁性粉末として平均粒子サイズの小さいものを使用することは記録密度向上の観点から好ましい。この点から、強磁性粉末の平均粒子サイズは50nm以下であることが好ましく、45nm以下であることがより好ましく、40nm以下であることが更に好ましく、35nm以下であることが一層好ましく、30nm以下であることがより一層好ましく、25nm以下であることが更に一層好ましく、20nm以下であることがなお一層好ましい。一方、磁化の安定性の観点からは、強磁性粉末の平均粒子サイズは5nm以上であることが好ましく、8nm以上であることがより好ましく、10nm以上であることが更に好ましく、15nm以上であることが一層好ましく、20nm以上であることがより一層好ましい。
<Magnetic layer>
(Ferromagnetic powder)
As the ferromagnetic powder contained in the magnetic layer, one or a combination of two or more kinds of ferromagnetic powder known as the ferromagnetic powder used in the magnetic layer of various magnetic recording media can be used. It is preferable to use a ferromagnetic powder having a small average particle size from the viewpoint of improving the recording density. From this point, the average particle size of the ferromagnetic powder is preferably 50 nm or less, more preferably 45 nm or less, further preferably 40 nm or less, further preferably 35 nm or less, and more preferably 30 nm or less. It is even more preferably 25 nm or less, and even more preferably 20 nm or less. On the other hand, from the viewpoint of the stability of magnetization, the average particle size of the ferromagnetic powder is preferably 5 nm or more, more preferably 8 nm or more, further preferably 10 nm or more, and further preferably 15 nm or more. Is more preferable, and 20 nm or more is even more preferable.
 強磁性粉末の粒子サイズに関して、粒子サイズの指標としては、平均粒子体積を挙げることもできる。平均粒子体積は、記録密度向上の観点から、2500nm以下であることが好ましく、2300nm以下であることがより好ましく、2000nm以下であることが更に好ましく、1500nm以下であることが一層好ましい。磁化の安定性の観点からは、強磁性粉末の平均粒子体積は、500nm以上であることが好ましく、600nm以上であることがより好ましく、650nm以上であることが更に好ましく、700nm以上であることが一層好ましい。上記の平均粒子体積は、後述する方法によって求められる平均粒子サイズから、球相当体積として求められる値である。 Regarding the particle size of the ferromagnetic powder, the average particle volume can also be mentioned as an index of the particle size. From the viewpoint of improving the recording density, the average particle volume is preferably 2500 nm 3 or less, more preferably 2300 nm 3 or less, further preferably 2000 nm 3 or less, and even more preferably 1500 nm 3 or less. .. From the viewpoint of magnetization stability, the average particle volume of the ferromagnetic powder is preferably 500 nm 3 or more, more preferably 600 nm 3 or more, further preferably 650 nm 3 or more, and 700 nm 3 or more. Is more preferable. The above average particle volume is a value obtained as a sphere-equivalent volume from the average particle size obtained by the method described later.
六方晶フェライト粉末
 強磁性粉末の好ましい具体例としては、六方晶フェライト粉末を挙げることができる。六方晶フェライト粉末の詳細については、例えば、特開2011-225417号公報の段落0012~0030、特開2011-216149号公報の段落0134~0136、特開2012-204726号公報の段落0013~0030および特開2015-127985号公報の段落0029~0084を参照できる。
Hexagonal ferrite powder As a preferable specific example of the ferromagnetic powder, hexagonal ferrite powder can be mentioned. For details of the hexagonal ferrite powder, for example, paragraphs 0012 to 0030 of JP 2011-225417, paragraphs 0134 to 0136 of JP 2011-216149, paragraphs 0013 to 0030 of JP 2012-204726 and References can be made to paragraphs 0029 to 0084 of JP-A-2015-127985.
 本発明および本明細書において、「六方晶フェライト粉末」とは、X線回折分析によって、主相として六方晶フェライト型の結晶構造が検出される強磁性粉末をいうものとする。主相とは、X線回折分析によって得られるX線回折スペクトルにおいて最も高強度の回折ピークが帰属する構造をいう。例えば、X線回折分析によって得られるX線回折スペクトルにおいて最も高強度の回折ピークが六方晶フェライト型の結晶構造に帰属される場合、六方晶フェライト型の結晶構造が主相として検出されたと判断するものとする。X線回折分析によって単一の構造のみが検出された場合には、この検出された構造を主相とする。六方晶フェライト型の結晶構造は、構成原子として、少なくとも鉄原子、二価金属原子および酸素原子を含む。二価金属原子とは、イオンとして二価のカチオンになり得る金属原子であり、ストロンチウム原子、バリウム原子、カルシウム原子等のアルカリ土類金属原子、鉛原子等を挙げることができる。本発明および本明細書において、六方晶ストロンチウムフェライト粉末とは、この粉末に含まれる主な二価金属原子がストロンチウム原子であるものをいい、六方晶バリウムフェライト粉末とは、この粉末に含まれる主な二価金属原子がバリウム原子であるものをいう。主な二価金属原子とは、この粉末に含まれる二価金属原子の中で、原子%基準で最も多くを占める二価金属原子をいうものとする。ただし、上記の二価金属原子には、希土類原子は包含されないものとする。本発明および本明細書における「希土類原子」は、スカンジウム原子(Sc)、イットリウム原子(Y)、およびランタノイド原子からなる群から選択される。ランタノイド原子は、ランタン原子(La)、セリウム原子(Ce)、プラセオジム原子(Pr)、ネオジム原子(Nd)、プロメチウム原子(Pm)、サマリウム原子(Sm)、ユウロピウム原子(Eu)、ガドリニウム原子(Gd)、テルビウム原子(Tb)、ジスプロシウム原子(Dy)、ホルミウム原子(Ho)、エルビウム原子(Er)、ツリウム原子(Tm)、イッテルビウム原子(Yb)、およびルテチウム原子(Lu)からなる群から選択される。 In the present invention and the present specification, the "hexagonal ferrite powder" refers to a ferromagnetic powder in which a hexagonal ferrite type crystal structure is detected as the main phase by X-ray diffraction analysis. The main phase refers to a structure to which the highest intensity diffraction peak belongs in the X-ray diffraction spectrum obtained by X-ray diffraction analysis. For example, when the highest intensity diffraction peak is attributed to the hexagonal ferrite type crystal structure in the X-ray diffraction spectrum obtained by X-ray diffraction analysis, it is determined that the hexagonal ferrite type crystal structure is detected as the main phase. It shall be. When only a single structure is detected by X-ray diffraction analysis, this detected structure is used as the main phase. The hexagonal ferrite type crystal structure contains at least iron atoms, divalent metal atoms and oxygen atoms as constituent atoms. The divalent metal atom is a metal atom that can be a divalent cation as an ion, and examples thereof include an alkaline earth metal atom such as a strontium atom, a barium atom, and a calcium atom, and a lead atom. In the present invention and the present specification, the hexagonal strontium ferrite powder means that the main divalent metal atom contained in this powder is a strontium atom, and the hexagonal barium ferrite powder is the main contained in this powder. A divalent metal atom is a barium atom. The main divalent metal atom is a divalent metal atom that occupies the largest amount on an atomic% basis among the divalent metal atoms contained in this powder. However, rare earth atoms are not included in the above divalent metal atoms. The "rare earth atom" in the present invention and the present specification is selected from the group consisting of a scandium atom (Sc), a yttrium atom (Y), and a lanthanoid atom. The lanthanoid atoms are lanthanum atom (La), cerium atom (Ce), placeodium atom (Pr), neodymium atom (Nd), promethium atom (Pm), samarium atom (Sm), uropyum atom (Eu), gadrinium atom (Gd). ), Terbium atom (Tb), dysprosium atom (Dy), formium atom (Ho), erbium atom (Er), thulium atom (Tm), ytterbium atom (Yb), and lutetium atom (Lu). To.
 以下に、六方晶フェライト粉末の一形態である六方晶ストロンチウムフェライト粉末について、更に詳細に説明する。 The hexagonal strontium ferrite powder, which is a form of hexagonal ferrite powder, will be described in more detail below.
 六方晶ストロンチウムフェライト粉末の活性化体積は、好ましくは800~1600nmの範囲である。上記範囲の活性化体積を示す微粒子化された六方晶ストロンチウムフェライト粉末は、優れた電磁変換特性を発揮する磁気記録媒体の作製のために好適である。六方晶ストロンチウムフェライト粉末の活性化体積は、好ましくは800nm以上であり、例えば850nm以上であることもできる。また、電磁変換特性の更なる向上の観点から、六方晶ストロンチウムフェライト粉末の活性化体積は、1500nm以下であることがより好ましく、1400nm以下であることが更に好ましく、1300nm以下であることが一層好ましく、1200nm以下であることがより一層好ましく、1100nm以下であることが更により一層好ましい。六方晶バリウムフェライト粉末の活性化体積についても、同様である。 The activated volume of the hexagonal strontium ferrite powder is preferably in the range of 800 to 1600 nm 3 . The finely divided hexagonal strontium ferrite powder exhibiting the activated volume in the above range is suitable for producing a magnetic recording medium exhibiting excellent electromagnetic conversion characteristics. The activated volume of the hexagonal strontium ferrite powder is preferably 800 nm 3 or more, and can be, for example, 850 nm 3 or more. Further, from the viewpoint of further improving the electromagnetic conversion characteristics, the activated volume of the hexagonal strontium ferrite powder is more preferably 1500 nm 3 or less, further preferably 1400 nm 3 or less, and 1300 nm 3 or less. Is even more preferable, and it is even more preferably 1200 nm 3 or less, and even more preferably 1100 nm 3 or less. The same applies to the activated volume of the hexagonal barium ferrite powder.
 「活性化体積」とは、磁化反転の単位であって、粒子の磁気的な大きさを示す指標である。本発明および本明細書に記載の活性化体積および後述の異方性定数Kuは、振動試料型磁力計を用いて保磁力Hc測定部の磁場スイープ速度3分と30分とで測定し(測定温度:23℃±1℃)、以下のHcと活性化体積Vとの関係式から求められる値である。異方性定数Kuの単位に関して、1erg/cc=1.0×10-1J/mである。
 Hc=2Ku/Ms{1-[(kT/KuV)ln(At/0.693)]1/2
[上記式中、Ku:異方性定数(単位:J/m)、Ms:飽和磁化(単位:kA/m)、k:ボルツマン定数、T:絶対温度(単位:K)、V:活性化体積(単位:cm)、A:スピン歳差周波数(単位:s-1)、t:磁界反転時間(単位:s)]
The "activated volume" is a unit of magnetization reversal and is an index showing the magnetic size of a particle. The activated volume described in the present invention and the present specification and the anisotropic constant Ku described later are measured using a vibrating sample magnetometer at magnetic field sweep speeds of 3 minutes and 30 minutes in the coercive force Hc measuring unit (measurement). Temperature: 23 ° C ± 1 ° C), which is a value obtained from the following relational expression between Hc and activated volume V. With respect to the unit of the anisotropy constant Ku, 1 erg / cc = 1.0 × 10 -1 J / m 3 .
Hc = 2Ku / Ms {1-[(kT / KuV) ln (At / 0.693)] 1/2 }
[In the above formula, Ku: anisotropic constant (unit: J / m 3 ), Ms: saturation magnetization (unit: kA / m), k: Boltzmann constant, T: absolute temperature (unit: K), V: activity. Volume (Unit: cm 3 ), A: Spin old frequency (Unit: s -1 ), t: Magnetic field reversal time (Unit: s)]
 熱揺らぎの低減、換言すれば熱的安定性の向上の指標としては、異方性定数Kuを挙げることができる。六方晶ストロンチウムフェライト粉末は、好ましくは1.8×10J/m以上のKuを有することができ、より好ましくは2.0×10J/m以上のKuを有することができる。また、六方晶ストロンチウムフェライト粉末のKuは、例えば2.5×10J/m以下であることができる。ただしKuが高いほど熱的安定性が高いことを意味し好ましいため、上記例示した値に限定されるものではない。 Anisotropy constant Ku can be mentioned as an index for reducing thermal fluctuation, in other words, improving thermal stability. The hexagonal strontium ferrite powder can preferably have a Ku of 1.8 × 10 5 J / m 3 or more, and more preferably 2.0 × 105 J / m 3 or more. Further, the Ku of the hexagonal strontium ferrite powder can be, for example, 2.5 × 105 J / m 3 or less. However, the higher the Ku, the higher the thermal stability, which is preferable, and therefore, the value is not limited to the above-exemplified values.
 六方晶ストロンチウムフェライト粉末は、希土類原子を含んでいてもよく、含まなくてもよい。六方晶ストロンチウムフェライト粉末が希土類原子を含む場合、鉄原子100原子%に対して、0.5~5.0原子%の含有率(バルク含有率)で希土類原子を含むことが好ましい。希土類原子を含む六方晶ストロンチウムフェライト粉末は、一形態では、希土類原子表層部偏在性を有することができる。本発明および本明細書における「希土類原子表層部偏在性」とは、六方晶ストロンチウムフェライト粉末を酸により部分溶解して得られた溶解液中の鉄原子100原子%に対する希土類原子含有率(以下、「希土類原子表層部含有率」または希土類原子に関して単に「表層部含有率」と記載する。)が、六方晶ストロンチウムフェライト粉末を酸により全溶解して得られた溶解液中の鉄原子100原子%に対する希土類原子含有率(以下、「希土類原子バルク含有率」または希土類原子に関して単に「バルク含有率」と記載する。)と、
 希土類原子表層部含有率/希土類原子バルク含有率>1.0
の比率を満たすことを意味する。後述の六方晶ストロンチウムフェライト粉末の希土類原子含有率とは、希土類原子バルク含有率と同義である。これに対し、酸を用いる部分溶解は六方晶ストロンチウムフェライト粉末を構成する粒子の表層部を溶解するため、部分溶解により得られる溶解液中の希土類原子含有率とは、六方晶ストロンチウムフェライト粉末を構成する粒子の表層部における希土類原子含有率である。希土類原子表層部含有率が、「希土類原子表層部含有率/希土類原子バルク含有率>1.0」の比率を満たすことは、六方晶ストロンチウムフェライト粉末を構成する粒子において、希土類原子が表層部に偏在(即ち内部より多く存在)していることを意味する。本発明および本明細書における表層部とは、六方晶ストロンチウムフェライト粉末を構成する粒子の表面から内部に向かう一部領域を意味する。
The hexagonal strontium ferrite powder may or may not contain rare earth atoms. When the hexagonal strontium ferrite powder contains rare earth atoms, it is preferable that the hexagonal strontium ferrite powder contains rare earth atoms at a content of 0.5 to 5.0 atomic% (bulk content) with respect to 100 atomic% of iron atoms. In one form, the hexagonal strontium ferrite powder containing a rare earth atom can have uneven distribution on the surface layer of the rare earth atom. The term "unevenly distributed on the surface of rare earth atoms" as used in the present invention and the present specification refers to the rare earth atom content with respect to 100 atomic% of iron atoms in the solution obtained by partially dissolving hexagonal strontium ferrite powder with an acid (hereinafter referred to as "rare earth atom content"). “Rare earth atom surface layer content” or simply “surface layer content” for rare earth atoms) is 100 atomic% of iron atoms in the solution obtained by completely dissolving hexagonal strontium ferrite powder with an acid. Rare earth atom content (hereinafter referred to as "rare earth atom bulk content" or simply referred to as "bulk content" for rare earth atoms).
Rare earth atom surface layer content / Rare earth atom bulk content> 1.0
Means to meet the ratio of. The rare earth atom content of the hexagonal strontium ferrite powder described later is synonymous with the rare earth atom bulk content. On the other hand, partial dissolution using an acid dissolves the surface layer of the particles constituting the hexagonal strontium ferrite powder, so the rare earth atom content in the solution obtained by partial dissolution is the composition of the hexagonal strontium ferrite powder. It is the rare earth atom content in the surface layer of the particles. The fact that the rare earth atom surface layer content satisfies the ratio of "rare earth atom surface layer content / rare earth atom bulk content>1.0" means that the rare earth atom is on the surface layer in the particles constituting the hexagonal strontium ferrite powder. It means that they are unevenly distributed (that is, they exist more than inside). The surface layer portion in the present invention and the present specification means a partial region from the surface of the particles constituting the hexagonal strontium ferrite powder toward the inside.
 六方晶ストロンチウムフェライト粉末が希土類原子を含む場合、希土類原子含有率(バルク含有率)は、鉄原子100原子%に対して0.5~5.0原子%の範囲であることが好ましい。上記範囲のバルク含有率で希土類原子を含み、かつ六方晶ストロンチウムフェライト粉末を構成する粒子の表層部に希土類原子が偏在していることは、繰り返し再生における再生出力の低下を抑制することに寄与すると考えられる。これは、六方晶ストロンチウムフェライト粉末が上記範囲のバルク含有率で希土類原子を含み、かつ六方晶ストロンチウムフェライト粉末を構成する粒子の表層部に希土類原子が偏在していることにより、異方性定数Kuを高めることができるためと推察される。異方性定数Kuは、この値が高いほど、いわゆる熱揺らぎと呼ばれる現象の発生を抑制すること(換言すれば熱的安定性を向上させること)ができる。熱揺らぎの発生が抑制されることにより、繰り返し再生における再生出力の低下を抑制することができる。六方晶ストロンチウムフェライト粉末の粒子表層部に希土類原子が偏在することが、表層部の結晶格子内の鉄(Fe)のサイトのスピンを安定化することに寄与し、これにより異方性定数Kuが高まるのではないかと推察される。
 また、希土類原子表層部偏在性を有する六方晶ストロンチウムフェライト粉末を磁性層の強磁性粉末として用いることは、磁気ヘッドとの摺動によって磁性層表面が削れることを抑制することにも寄与すると推察される。即ち、磁気記録媒体の走行耐久性の向上にも、希土類原子表層部偏在性を有する六方晶ストロンチウムフェライト粉末が寄与し得ると推察される。これは、六方晶ストロンチウムフェライト粉末を構成する粒子の表面に希土類原子が偏在することが、粒子表面と磁性層に含まれる有機物質(例えば、結合剤および/または添加剤)との相互作用の向上に寄与し、その結果、磁性層の強度が向上するためではないかと推察される。
 繰り返し再生における再生出力の低下をより一層抑制する観点および/または走行耐久性の更なる向上の観点からは、希土類原子含有率(バルク含有率)は、0.5~4.5原子%の範囲であることがより好ましく、1.0~4.5原子%の範囲であることが更に好ましく、1.5~4.5原子%の範囲であることが一層好ましい。
When the hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atom content (bulk content) is preferably in the range of 0.5 to 5.0 atomic% with respect to 100 atomic% of iron atoms. The fact that the rare earth atoms are contained in the bulk content in the above range and the rare earth atoms are unevenly distributed on the surface layer of the particles constituting the hexagonal strontium ferrite powder contributes to suppressing the decrease in the regeneration output in the repeated regeneration. Conceivable. This is because the hexagonal strontium ferrite powder contains rare earth atoms at a bulk content in the above range, and the rare earth atoms are unevenly distributed on the surface layer of the particles constituting the hexagonal strontium ferrite powder. It is presumed that it is possible to increase. The higher the value of the anisotropy constant Ku, the more the occurrence of the so-called thermal fluctuation phenomenon can be suppressed (in other words, the thermal stability can be improved). By suppressing the occurrence of thermal fluctuation, it is possible to suppress a decrease in the reproduction output in repeated reproduction. The uneven distribution of rare earth atoms on the surface layer of the hexagonal strontium ferrite powder contributes to stabilizing the spin of iron (Fe) sites in the crystal lattice of the surface layer, which results in anisotropy constant Ku. It is speculated that it may increase.
In addition, it is speculated that the use of hexagonal strontium ferrite powder, which has uneven distribution on the surface of rare earth atoms, as a ferromagnetic powder for the magnetic layer also contributes to suppressing the surface of the magnetic layer from being scraped by sliding with the magnetic head. Ru. That is, it is presumed that the hexagonal strontium ferrite powder having uneven distribution of the rare earth atomic surface layer can also contribute to the improvement of the running durability of the magnetic recording medium. This is because the uneven distribution of rare earth atoms on the surface of the particles constituting the hexagonal strontium ferrite powder improves the interaction between the particle surface and the organic substances (for example, binder and / or additive) contained in the magnetic layer. As a result, it is presumed that the strength of the magnetic layer is improved.
The rare earth atom content (bulk content) is in the range of 0.5 to 4.5 atomic% from the viewpoint of further suppressing the decrease in the reproduction output in the repeated reproduction and / or further improving the running durability. It is more preferably in the range of 1.0 to 4.5 atomic%, further preferably in the range of 1.5 to 4.5 atomic%.
 上記バルク含有率は、六方晶ストロンチウムフェライト粉末を全溶解して求められる含有率である。本発明および本明細書において、特記しない限り、原子について含有率とは、六方晶ストロンチウムフェライト粉末を全溶解して求められるバルク含有率をいうものとする。希土類原子を含む六方晶ストロンチウムフェライト粉末は、希土類原子として一種の希土類原子のみ含んでもよく、二種以上の希土類原子を含んでもよい。二種以上の希土類原子を含む場合の上記バルク含有率は、二種以上の希土類原子の合計について求められる。この点は、本発明および本明細書における他の成分についても同様である。即ち、特記しない限り、ある成分は、一種のみ用いてもよく、二種以上用いてもよい。二種以上用いられる場合の含有量または含有率とは、二種以上の合計についていうものとする。 The bulk content is the content obtained by completely dissolving the hexagonal strontium ferrite powder. Unless otherwise specified in the present invention and the present specification, the content of atoms means the bulk content obtained by completely dissolving hexagonal strontium ferrite powder. The hexagonal strontium ferrite powder containing a rare earth atom may contain only one kind of rare earth atom as a rare earth atom, or may contain two or more kinds of rare earth atoms. The bulk content when two or more rare earth atoms are contained is determined for the total of two or more rare earth atoms. This point is the same for the present invention and other components in the present specification. That is, unless otherwise specified, a certain component may be used alone or in combination of two or more. The content or content rate when two or more types are used shall mean the total of two or more types.
 六方晶ストロンチウムフェライト粉末が希土類原子を含む場合、含まれる希土類原子は、希土類原子のいずれか一種以上であればよい。繰り返し再生における再生出力の低下をより一層抑制する観点から好ましい希土類原子としては、ネオジム原子、サマリウム原子、イットリウム原子およびジスプロシウム原子を挙げることができ、ネオジム原子、サマリウム原子およびイットリウム原子がより好ましく、ネオジム原子が更に好ましい。 When the hexagonal strontium ferrite powder contains a rare earth atom, the rare earth atom contained may be any one or more of the rare earth atoms. Preferred rare earth atoms from the viewpoint of further suppressing the decrease in regeneration output in repeated regeneration include neodymium atom, samarium atom, yttrium atom and dysprosium atom, and neodymium atom, samarium atom and yttrium atom are more preferable, and neodymium atom is more preferable. Atoms are more preferred.
 希土類原子表層部偏在性を有する六方晶ストロンチウムフェライト粉末において、希土類原子は六方晶ストロンチウムフェライト粉末を構成する粒子の表層部に偏在していればよく、偏在の程度は限定されるものではない。例えば、希土類原子表層部偏在性を有する六方晶ストロンチウムフェライト粉末について、後述する溶解条件で部分溶解して求められた希土類原子の表層部含有率と後述する溶解条件で全溶解して求められた希土類原子のバルク含有率との比率、「表層部含有率/バルク含有率」は1.0超であり、1.5以上であることができる。「表層部含有率/バルク含有率」が1.0より大きいことは、六方晶ストロンチウムフェライト粉末を構成する粒子において、希土類原子が表層部に偏在(即ち内部より多く存在)していることを意味する。また、後述する溶解条件で部分溶解して求められた希土類原子の表層部含有率と後述する溶解条件で全溶解して求められた希土類原子のバルク含有率との比率、「表層部含有率/バルク含有率」は、例えば、10.0以下、9.0以下、8.0以下、7.0以下、6.0以下、5.0以下、または4.0以下であることができる。ただし、希土類原子表層部偏在性を有する六方晶ストロンチウムフェライト粉末において、希土類原子は六方晶ストロンチウムフェライト粉末を構成する粒子の表層部に偏在していればよく、上記の「表層部含有率/バルク含有率」は、例示した上限または下限に限定されるものではない。 In the hexagonal strontium ferrite powder having uneven distribution on the surface layer of rare earth atoms, the rare earth atoms may be unevenly distributed on the surface layer of the particles constituting the hexagonal strontium ferrite powder, and the degree of uneven distribution is not limited. For example, a hexagonal strontium ferrite powder having uneven distribution on the surface layer of a rare earth atom is partially dissolved under the dissolution conditions described later and the content of the surface layer of the rare earth atom and the rare earths obtained by completely dissolving under the dissolution conditions described later. The ratio of the atom to the bulk content, "surface layer content / bulk content" is more than 1.0, and can be 1.5 or more. When the "surface layer content / bulk content" is larger than 1.0, it means that the rare earth atoms are unevenly distributed (that is, more present than the inside) in the particles constituting the hexagonal strontium ferrite powder. do. Further, the ratio of the surface layer content of the rare earth atom obtained by partial melting under the dissolution conditions described later and the bulk content of the rare earth atom obtained by total dissolution under the dissolution conditions described later, "surface layer content / The "bulk content" can be, for example, 10.0 or less, 9.0 or less, 8.0 or less, 7.0 or less, 6.0 or less, 5.0 or less, or 4.0 or less. However, in the hexagonal strontium ferrite powder having uneven distribution on the surface layer of rare earth atoms, the rare earth atoms may be unevenly distributed on the surface layer of the particles constituting the hexagonal strontium ferrite powder. The "rate" is not limited to the upper and lower limits exemplified.
 六方晶ストロンチウムフェライト粉末の部分溶解および全溶解について、以下に説明する。粉末として存在している六方晶ストロンチウムフェライト粉末については、部分溶解および全溶解する試料粉末は、同一ロットの粉末から採取する。一方、磁気記録媒体の磁性層に含まれている六方晶ストロンチウムフェライト粉末については、磁性層から取り出した六方晶ストロンチウムフェライト粉末の一部を部分溶解に付し、他の一部を全溶解に付す。磁性層からの六方晶ストロンチウムフェライト粉末の取り出しは、例えば、特開2015-91747号公報の段落0032に記載の方法によって行うことができる。
 上記部分溶解とは、溶解終了時に液中に六方晶ストロンチウムフェライト粉末の残留が目視で確認できる程度に溶解することをいう。例えば、部分溶解により、六方晶ストロンチウムフェライト粉末を構成する粒子について、粒子全体を100質量%として10~20質量%の領域を溶解することができる。一方、上記全溶解とは、溶解終了時に液中に六方晶ストロンチウムフェライト粉末の残留が目視で確認されない状態まで溶解することをいう。
 上記部分溶解および表層部含有率の測定は、例えば、以下の方法により行われる。ただし、下記の試料粉末量等の溶解条件は例示であって、部分溶解および全溶解が可能な溶解条件を任意に採用できる。
 試料粉末12mgおよび1mol/L塩酸10mLを入れた容器(例えばビーカー)を、設定温度70℃のホットプレート上で1時間保持する。得られた溶解液を0.1μmのメンブレンフィルタでろ過する。こうして得られたろ液の元素分析を誘導結合プラズマ(ICP;Inductively Coupled Plasma)分析装置によって行う。こうして、鉄原子100原子%に対する希土類原子の表層部含有率を求めることができる。元素分析により複数種の希土類原子が検出された場合には、全希土類原子の合計含有率を、表層部含有率とする。この点は、バルク含有率の測定においても、同様である。
 一方、上記全溶解およびバルク含有率の測定は、例えば、以下の方法により行われる。
 試料粉末12mgおよび4mol/L塩酸10mLを入れた容器(例えばビーカー)を、設定温度80℃のホットプレート上で3時間保持する。その後は上記の部分溶解および表層部含有率の測定と同様に行い、鉄原子100原子%に対するバルク含有率を求めることができる。
Partial and total melting of hexagonal strontium ferrite powder will be described below. For the hexagonal strontium ferrite powder that exists as a powder, the sample powder that is partially or completely dissolved is collected from the same lot of powder. On the other hand, regarding the hexagonal strontium ferrite powder contained in the magnetic layer of the magnetic recording medium, a part of the hexagonal strontium ferrite powder taken out from the magnetic layer is subjected to partial dissolution, and the other part is subjected to total dissolution. .. The hexagonal strontium ferrite powder can be taken out from the magnetic layer by, for example, the method described in paragraph 0032 of Japanese Patent Application Laid-Open No. 2015-91747.
The above partial dissolution means that the hexagonal strontium ferrite powder is dissolved in the liquid to the extent that the residue of the hexagonal strontium ferrite powder can be visually confirmed at the end of the dissolution. For example, by partial dissolution, a region of 10 to 20% by mass can be dissolved with respect to the particles constituting the hexagonal strontium ferrite powder, with the entire particles as 100% by mass. On the other hand, the above-mentioned total dissolution means that the hexagonal strontium ferrite powder is dissolved in the liquid until the residue is not visually confirmed at the end of the dissolution.
The above partial melting and measurement of the surface layer content are carried out by, for example, the following methods. However, the following dissolution conditions such as the amount of sample powder are examples, and dissolution conditions capable of partial dissolution and total dissolution can be arbitrarily adopted.
A container (for example, a beaker) containing 12 mg of sample powder and 10 mL of 1 mol / L hydrochloric acid is held on a hot plate at a set temperature of 70 ° C. for 1 hour. The obtained solution is filtered through a 0.1 μm membrane filter. Elemental analysis of the filtrate thus obtained is performed by an inductively coupled plasma (ICP) analyzer. In this way, the content of the rare earth atom in the surface layer with respect to 100 atom% of the iron atom can be obtained. When a plurality of rare earth atoms are detected by elemental analysis, the total content of all rare earth atoms is defined as the surface layer content. This point is the same in the measurement of bulk content.
On the other hand, the total dissolution and the measurement of the bulk content are carried out by, for example, the following methods.
A container (for example, a beaker) containing 12 mg of sample powder and 10 mL of 4 mol / L hydrochloric acid is held on a hot plate at a set temperature of 80 ° C. for 3 hours. After that, the same procedure as the above-mentioned partial melting and measurement of the surface layer content can be performed to determine the bulk content with respect to 100 atomic% of iron atoms.
 磁気記録媒体に記録されたデータを再生する際の再生出力を高める観点から、磁気記録媒体に含まれる強磁性粉末の質量磁化σsが高いことは望ましい。この点に関して、希土類原子を含むものの希土類原子表層部偏在性を持たない六方晶ストロンチウムフェライト粉末は、希土類原子を含まない六方晶ストロンチウムフェライト粉末と比べてσsが大きく低下する傾向が見られた。これに対し、そのようなσsの大きな低下を抑制するうえでも、希土類原子表層部偏在性を有する六方晶ストロンチウムフェライト粉末は好ましいと考えられる。一形態では、六方晶ストロンチウムフェライト粉末のσsは、45A・m/kg以上であることができ、47A・m/kg以上であることもできる。一方、σsは、ノイズ低減の観点からは、80A・m/kg以下であることが好ましく、60A・m/kg以下であることがより好ましい。σsは、振動試料型磁力計等の磁気特性を測定可能な公知の測定装置を用いて測定することができる。本発明および本明細書において、特記しない限り、質量磁化σsは、磁場強度15kOeで測定される値とする。1[kOe]=10/4π[A/m]である。 From the viewpoint of increasing the reproduction output when reproducing the data recorded on the magnetic recording medium, it is desirable that the mass magnetization σs of the ferromagnetic powder contained in the magnetic recording medium is high. In this regard, the hexagonal strontium ferrite powder containing rare earth atoms but not having uneven distribution on the surface layer of rare earth atoms tended to have a significantly lower σs than the hexagonal strontium ferrite powder containing no rare earth atoms. On the other hand, hexagonal strontium ferrite powder having uneven distribution on the surface layer of rare earth atoms is considered to be preferable in order to suppress such a large decrease in σs. In one embodiment, the σs of the hexagonal strontium ferrite powder can be 45 A · m 2 / kg or more, and can also be 47 A · m 2 / kg or more. On the other hand, σs is preferably 80 A · m 2 / kg or less, and more preferably 60 A · m 2 / kg or less, from the viewpoint of noise reduction. σs can be measured using a known measuring device capable of measuring magnetic characteristics such as a vibration sample magnetometer. Unless otherwise specified in the present invention and the present specification, the mass magnetization σs is a value measured at a magnetic field strength of 15 kOe. 1 [koe] = 10 6 / 4π [A / m].
 六方晶ストロンチウムフェライト粉末の構成原子の含有率(バルク含有率)に関して、ストロンチウム原子含有率は、鉄原子100原子%に対して、例えば2.0~15.0原子%の範囲であることができる。一形態では、六方晶ストロンチウムフェライト粉末は、この粉末に含まれる二価金属原子がストロンチウム原子のみであることができる。また他の一形態では、六方晶ストロンチウムフェライト粉末は、ストロンチウム原子に加えて一種以上の他の二価金属原子を含むこともできる。例えば、バリウム原子および/またはカルシウム原子を含むことができる。ストロンチウム原子以外の他の二価金属原子が含まれる場合、六方晶ストロンチウムフェライト粉末におけるバリウム原子含有率およびカルシウム原子含有率は、それぞれ、例えば、鉄原子100原子%に対して、0.05~5.0原子%の範囲であることができる。 Regarding the content (bulk content) of the constituent atoms of the hexagonal strontium ferrite powder, the strontium atom content can be in the range of, for example, 2.0 to 15.0 atom% with respect to 100 atom% of iron atoms. .. In one form, the hexagonal strontium ferrite powder can contain only strontium atoms as divalent metal atoms contained in the powder. In another embodiment, the hexagonal strontium ferrite powder may contain one or more other divalent metal atoms in addition to the strontium atom. For example, it can contain barium and / or calcium atoms. When a divalent metal atom other than the strontium atom is contained, the barium atom content and the calcium atom content in the hexagonal strontium ferrite powder are, for example, 0.05 to 5 with respect to 100 atomic% of the iron atom, respectively. It can be in the range of 0.0 atomic%.
 六方晶フェライトの結晶構造としては、マグネトプランバイト型(「M型」とも呼ばれる。)、W型、Y型およびZ型が知られている。六方晶ストロンチウムフェライト粉末は、いずれの結晶構造を取るものであってもよい。結晶構造は、X線回折分析によって確認することができる。六方晶ストロンチウムフェライト粉末は、X線回折分析によって、単一の結晶構造または二種以上の結晶構造が検出されるものであることができる。例えば一形態では、六方晶ストロンチウムフェライト粉末は、X線回折分析によってM型の結晶構造のみが検出されるものであることができる。例えば、M型の六方晶フェライトは、AFe1219の組成式で表される。ここでAは二価金属原子を表し、六方晶ストロンチウムフェライト粉末がM型である場合、Aはストロンチウム原子(Sr)のみであるか、またはAとして複数の二価金属原子が含まれる場合には、上記の通り原子%基準で最も多くをストロンチウム原子(Sr)が占める。六方晶ストロンチウムフェライト粉末の二価金属原子含有率は、通常、六方晶フェライトの結晶構造の種類により定まるものであり、特に限定されるものではない。鉄原子含有率および酸素原子含有率についても、同様である。六方晶ストロンチウムフェライト粉末は、少なくとも、鉄原子、ストロンチウム原子および酸素原子を含み、更に希土類原子を含むこともできる。更に、六方晶ストロンチウムフェライト粉末は、これら原子以外の原子を含んでもよく、含まなくてもよい。一例として、六方晶ストロンチウムフェライト粉末は、アルミニウム原子(Al)を含むものであってもよい。アルミニウム原子の含有率は、鉄原子100原子%に対して、例えば0.5~10.0原子%であることができる。繰り返し再生における再生出力低下をより一層抑制する観点からは、六方晶ストロンチウムフェライト粉末は、鉄原子、ストロンチウム原子、酸素原子および希土類原子を含み、これら原子以外の原子の含有率が、鉄原子100原子%に対して、10.0原子%以下であることが好ましく、0~5.0原子%の範囲であることがより好ましく、0原子%であってもよい。即ち、一形態では、六方晶ストロンチウムフェライト粉末は、鉄原子、ストロンチウム原子、酸素原子および希土類原子以外の原子を含まなくてもよい。上記の原子%で表示される含有率は、六方晶ストロンチウムフェライト粉末を全溶解して求められる各原子の含有率(単位:質量%)を、各原子の原子量を用いて原子%表示の値に換算して求められる。また、本発明および本明細書において、ある原子について「含まない」とは、全溶解してICP分析装置により測定される含有率が0質量%であることをいう。ICP分析装置の検出限界は、通常、質量基準で0.01ppm(parts per million)以下である。上記の「含まない」とは、ICP分析装置の検出限界未満の量で含まれることを包含する意味で用いるものとする。六方晶ストロンチウムフェライト粉末は、一形態では、ビスマス原子(Bi)を含まないものであることができる。 As the crystal structure of hexagonal ferrite, a magnetoplumbite type (also referred to as "M type"), a W type, a Y type, and a Z type are known. The hexagonal strontium ferrite powder may have any crystal structure. The crystal structure can be confirmed by X-ray diffraction analysis. Hexagonal strontium ferrite powder can be one in which a single crystal structure or two or more kinds of crystal structures are detected by X-ray diffraction analysis. For example, in one form, the hexagonal strontium ferrite powder can be such that only the M-type crystal structure is detected by X-ray diffraction analysis. For example, M-type hexagonal ferrite is represented by the composition formula of AFe 12 O 19 . Here, A represents a divalent metal atom, and when the hexagonal strontium ferrite powder is M-type, A is only a strontium atom (Sr), or when A contains a plurality of divalent metal atoms. As mentioned above, the strontium atom (Sr) occupies the largest amount on the basis of atomic%. The divalent metal atom content of the hexagonal strontium ferrite powder is usually determined by the type of the crystal structure of the hexagonal ferrite, and is not particularly limited. The same applies to the iron atom content and the oxygen atom content. The hexagonal strontium ferrite powder contains at least an iron atom, a strontium atom and an oxygen atom, and may further contain a rare earth atom. Further, the hexagonal strontium ferrite powder may or may not contain atoms other than these atoms. As an example, the hexagonal strontium ferrite powder may contain an aluminum atom (Al). The content of aluminum atoms can be, for example, 0.5 to 10.0 atomic% with respect to 100 atomic% of iron atoms. From the viewpoint of further suppressing the decrease in regeneration output in repeated regeneration, the hexagonal strontium ferrite powder contains iron atoms, strontium atoms, oxygen atoms and rare earth atoms, and the content of atoms other than these atoms is 100 iron atoms. % Is preferably 10.0 atomic% or less, more preferably in the range of 0 to 5.0 atomic%, and may be 0 atomic%. That is, in one form, the hexagonal strontium ferrite powder does not have to contain atoms other than iron atoms, strontium atoms, oxygen atoms and rare earth atoms. The content expressed in atomic% above is the content of each atom (unit: mass%) obtained by completely dissolving the hexagonal strontium ferrite powder, and is expressed in atomic% using the atomic weight of each atom. Calculated by conversion. Further, in the present invention and the present specification, "not contained" with respect to a certain atom means that the content is completely dissolved and the content measured by the ICP analyzer is 0% by mass. The detection limit of an ICP analyzer is usually 0.01 ppm (parts per million) or less on a mass basis. The above-mentioned "not included" is used in the sense of including the inclusion in an amount less than the detection limit of the ICP analyzer. The hexagonal strontium ferrite powder can, in one form, be free of bismuth atoms (Bi).
金属粉末
 強磁性粉末の好ましい具体例としては、強磁性金属粉末を挙げることもできる。強磁性金属粉末の詳細については、例えば特開2011-216149号公報の段落0137~0141および特開2005-251351号公報の段落0009~0023を参照できる。
Metallic powder Ferromagnetic metal powder can also be mentioned as a preferable specific example of the ferromagnetic powder. For details of the ferromagnetic metal powder, for example, paragraphs 0137 to 0141 of JP2011-216149A and paragraphs 0009 to 0023 of JP2005-251351 can be referred to.
ε-酸化鉄粉末
 強磁性粉末の好ましい具体例としては、ε-酸化鉄粉末を挙げることもできる。本発明および本明細書において、「ε-酸化鉄粉末」とは、X線回折分析によって、主相としてε-酸化鉄型の結晶構造が検出される強磁性粉末をいうものとする。例えば、X線回折分析によって得られるX線回折スペクトルにおいて最も高強度の回折ピークがε-酸化鉄型の結晶構造に帰属される場合、ε-酸化鉄型の結晶構造が主相として検出されたと判断するものとする。ε-酸化鉄粉末の製造方法としては、ゲーサイトから作製する方法、逆ミセル法等が知られている。上記製造方法は、いずれも公知である。また、Feの一部がGa、Co、Ti、Al、Rh等の置換原子によって置換されたε-酸化鉄粉末を製造する方法については、例えば、J. Jpn. Soc. Powder Metallurgy Vol. 61 Supplement, No. S1, pp. S280-S284、J. Mater. Chem. C, 2013, 1, pp.5200-5206等を参照できる。ただし、上記磁気記録媒体の磁性層において強磁性粉末として使用可能なε-酸化鉄粉末の製造方法は、ここで挙げた方法に限定されない。
ε-Iron oxide powder As a preferable specific example of the ferromagnetic powder, ε-iron oxide powder can also be mentioned. In the present invention and the present specification, "ε-iron oxide powder" refers to a ferromagnetic powder in which an ε-iron oxide type crystal structure is detected as a main phase by X-ray diffraction analysis. For example, when the highest intensity diffraction peak is attributed to the ε-iron oxide type crystal structure in the X-ray diffraction spectrum obtained by X-ray diffraction analysis, the ε-iron oxide type crystal structure is detected as the main phase. It shall be judged. As a method for producing ε-iron oxide powder, a method for producing goethite, a reverse micelle method, and the like are known. All of the above manufacturing methods are known. Further, regarding a method for producing an ε-iron oxide powder in which a part of Fe is substituted with a substituted atom such as Ga, Co, Ti, Al, Rh, for example, J. Jpn. Soc. Powder Metallurgy Vol. 61 Supplement, No. S1, pp. S280-S284, J. Mol. Mater. Chem. C, 2013, 1, pp. 5200-5206 and the like can be referred to. However, the method for producing ε-iron oxide powder that can be used as the ferromagnetic powder in the magnetic layer of the magnetic recording medium is not limited to the method described here.
 ε-酸化鉄粉末の活性化体積は、好ましくは300~1500nmの範囲である。上記範囲の活性化体積を示す微粒子化されたε-酸化鉄粉末は、優れた電磁変換特性を発揮する磁気記録媒体の作製のために好適である。ε-酸化鉄粉末の活性化体積は、好ましくは300nm以上であり、例えば500nm以上であることもできる。また、電磁変換特性の更なる向上の観点から、ε-酸化鉄粉末の活性化体積は、1400nm以下であることがより好ましく、1300nm以下であることが更に好ましく、1200nm以下であることが一層好ましく、1100nm以下であることがより一層好ましい。 The activated volume of the ε-iron oxide powder is preferably in the range of 300 to 1500 nm 3 . The finely divided ε-iron oxide powder exhibiting an activated volume in the above range is suitable for producing a magnetic recording medium exhibiting excellent electromagnetic conversion characteristics. The activated volume of the ε-iron oxide powder is preferably 300 nm 3 or more, and can be, for example, 500 nm 3 or more. Further, from the viewpoint of further improving the electromagnetic conversion characteristics, the activated volume of the ε-iron oxide powder is more preferably 1400 nm 3 or less, further preferably 1300 nm 3 or less, and 1200 nm 3 or less. Is more preferable, and 1100 nm 3 or less is even more preferable.
 熱揺らぎの低減、換言すれば熱的安定性の向上の指標としては、異方性定数Kuを挙げることができる。ε-酸化鉄粉末は、好ましくは3.0×10J/m以上のKuを有することができ、より好ましくは8.0×10J/m以上のKuを有することができる。また、ε-酸化鉄粉末のKuは、例えば3.0×10J/m以下であることができる。ただしKuが高いほど熱的安定性が高いことを意味し、好ましいため、上記例示した値に限定されるものではない。 Anisotropy constant Ku can be mentioned as an index for reducing thermal fluctuation, in other words, improving thermal stability. The ε-iron oxide powder can preferably have a Ku of 3.0 × 10 4 J / m 3 or more, and more preferably 8.0 × 10 4 J / m 3 or more. Further, the Ku of the ε-iron oxide powder can be, for example, 3.0 × 105 J / m 3 or less. However, the higher the Ku, the higher the thermal stability, which is preferable, and therefore, the value is not limited to the above-exemplified values.
 磁気記録媒体に記録されたデータを再生する際の再生出力を高める観点から、磁気記録媒体に含まれる強磁性粉末の質量磁化σsが高いことは望ましい。この点に関して、一形態では、ε-酸化鉄粉末のσsは、8A・m/kg以上であることができ、12A・m/kg以上であることもできる。一方、ε-酸化鉄粉末のσsは、ノイズ低減の観点からは、40A・m/kg以下であることが好ましく、35A・m/kg以下であることがより好ましい。 From the viewpoint of increasing the reproduction output when reproducing the data recorded on the magnetic recording medium, it is desirable that the mass magnetization σs of the ferromagnetic powder contained in the magnetic recording medium is high. In this regard, in one embodiment, the σs of the ε-iron oxide powder can be 8 A · m 2 / kg or more, and can also be 12 A · m 2 / kg or more. On the other hand, the σs of the ε-iron oxide powder is preferably 40 A · m 2 / kg or less, and more preferably 35 A · m 2 / kg or less, from the viewpoint of noise reduction.
 本発明および本明細書において、特記しない限り、強磁性粉末等の各種粉末の平均粒子サイズは、透過型電子顕微鏡を用いて、以下の方法により測定される値とする。
 粉末を、透過型電子顕微鏡を用いて撮影倍率100000倍で撮影し、総倍率500000倍になるように印画紙にプリントして粉末を構成する粒子の写真を得る。得られた粒子の写真から目的の粒子を選びデジタイザーで粒子の輪郭をトレースし粒子(一次粒子)のサイズを測定する。一次粒子とは、凝集のない独立した粒子をいう。
 以上の測定を、無作為に抽出した500個の粒子について行う。こうして得られた500個の粒子の粒子サイズの算術平均を、粉末の平均粒子サイズとする。上記透過型電子顕微鏡としては、例えば日立製透過型電子顕微鏡H-9000型を用いることができる。また、粒子サイズの測定は、公知の画像解析ソフト、例えばカールツァイス製画像解析ソフトKS-400を用いて行うことができる。後述の実施例に示す平均粒子サイズは、特記しない限り、透過型電子顕微鏡として日立製透過型電子顕微鏡H-9000型、画像解析ソフトとしてカールツァイス製画像解析ソフトKS-400を用いて測定された値である。本発明および本明細書において、粉末とは、複数の粒子の集合を意味する。例えば、強磁性粉末とは、複数の強磁性粒子の集合を意味する。また、複数の粒子の集合とは、集合を構成する粒子が直接接触している形態に限定されず、後述する結合剤、添加剤等が、粒子同士の間に介在している形態も包含される。粒子との語が、粉末を表すために用いられることもある。
Unless otherwise specified in the present invention and the present specification, the average particle size of various powders such as ferromagnetic powders is a value measured by the following method using a transmission electron microscope.
The powder is photographed using a transmission electron microscope at an imaging magnification of 100,000 times, and printed on photographic paper so as to have a total magnification of 500,000 times to obtain a photograph of the particles constituting the powder. Select the target particle from the obtained photograph of the particle, trace the outline of the particle with a digitizer, and measure the size of the particle (primary particle). Primary particles are independent particles without agglomeration.
The above measurements are performed on 500 randomly sampled particles. The arithmetic mean of the particle sizes of the 500 particles thus obtained is taken as the average particle size of the powder. As the transmission electron microscope, for example, a transmission electron microscope H-9000 manufactured by Hitachi can be used. Further, the particle size can be measured by using a known image analysis software, for example, an image analysis software KS-400 manufactured by Carl Zeiss. Unless otherwise specified, the average particle size shown in the examples described later was measured using a transmission electron microscope H-9000 manufactured by Hitachi as a transmission electron microscope and a Carl Zeiss image analysis software KS-400 as an image analysis software. The value. In the present invention and the present specification, the powder means an aggregate of a plurality of particles. For example, a ferromagnetic powder means a collection of a plurality of ferromagnetic particles. Further, the set of a plurality of particles is not limited to a form in which the particles constituting the set are in direct contact with each other, and also includes a form in which a binder, an additive, etc., which will be described later, are interposed between the particles. To. The term particle is sometimes used to describe powder.
 粒子サイズ測定のために磁気記録媒体から試料粉末を採取する方法としては、例えば特開2011-048878号公報の段落0015に記載の方法を採用することができる。 As a method for collecting sample powder from a magnetic recording medium for particle size measurement, for example, the method described in paragraph 0015 of JP2011-048878 can be adopted.
 本発明および本明細書において、特記しない限り、粉末を構成する粒子のサイズ(粒子サイズ)は、上記の粒子写真において観察される粒子の形状が、
(1)針状、紡錘状、柱状(ただし、高さが底面の最大長径より大きい)等の場合は、粒子を構成する長軸の長さ、即ち長軸長で表され、
(2)板状または柱状(ただし、厚みまたは高さが板面または底面の最大長径より小さい)の場合は、その板面または底面の最大長径で表され、
(3)球形、多面体状、不定形等であって、かつ形状から粒子を構成する長軸を特定できない場合は、円相当径で表される。円相当径とは、円投影法で求められるものを言う。
Unless otherwise specified in the present invention and the present specification, the size (particle size) of the particles constituting the powder is the shape of the particles observed in the above particle photograph.
(1) In the case of needle-shaped, spindle-shaped, columnar (however, the height is larger than the maximum major axis of the bottom surface), it is represented by the length of the major axis constituting the particle, that is, the major axis length.
(2) If it is plate-shaped or columnar (however, the thickness or height is smaller than the maximum major axis of the plate surface or bottom surface), it is represented by the maximum major axis of the plate surface or bottom surface.
(3) If the particle is spherical, polyhedral, amorphous, etc., and the long axis constituting the particle cannot be specified from the shape, it is represented by the diameter equivalent to a circle. The diameter equivalent to a circle is what is obtained by the circular projection method.
 また、粉末の針状比は、上記測定において粒子の短軸の長さ、即ち短軸長を測定し、上記500個の粒子について得た長軸長の算術平均(平均長軸長)と短軸長の算術平均(平均短軸長)から、「平均長軸長/平均短軸長」として求められる。ここで、特記しない限り、短軸長とは、上記粒子サイズの定義で(1)の場合は、粒子を構成する短軸の長さを、同じく(2)の場合は、厚みまたは高さを各々指し、(3)の場合は、長軸と短軸の区別がないから、(平均長軸長/平均短軸長)は、便宜上1とみなす。
 そして、特記しない限り、粒子の形状が特定の場合、例えば、上記粒子サイズの定義(1)の場合、平均粒子サイズは平均長軸長であり、同定義(2)の場合、平均粒子サイズは平均板径である。同定義(3)の場合、平均粒子サイズは、平均直径(平均粒径、平均粒子径ともいう)である。
Further, the needle-like ratio of the powder is shorter than the arithmetic average (average major axis length) of the major axis length obtained for the above 500 particles by measuring the minor axis length of the particles in the above measurement, that is, the minor axis length. It is obtained as "average major axis length / average minor axis length" from the arithmetic average (average minor axis length) of the axis length. Here, unless otherwise specified, the minor axis length is the length of the minor axis constituting the particle in the case of (1) in the above definition of the particle size, and the thickness or height in the case of the same (2). In the case of (3), there is no distinction between the major axis and the minor axis, so (average major axis length / average minor axis length) is regarded as 1 for convenience.
Unless otherwise specified, when the shape of the particles is specific, for example, in the case of the above definition of particle size (1), the average particle size is the average major axis length, and in the case of the same definition (2), the average particle size is The average plate diameter. In the case of the same definition (3), the average particle size is an average diameter (also referred to as an average particle size and an average particle size).
 磁性層における強磁性粉末の含有量(充填率)は、好ましくは50~90質量%の範囲であり、より好ましくは60~90質量%の範囲である。磁性層において強磁性粉末の充填率が高いことは、記録密度向上の観点から好ましい。 The content (filling rate) of the ferromagnetic powder in the magnetic layer is preferably in the range of 50 to 90% by mass, and more preferably in the range of 60 to 90% by mass. A high filling rate of the ferromagnetic powder in the magnetic layer is preferable from the viewpoint of improving the recording density.
(結合剤)
 上記磁気記録媒体は塗布型の磁気記録媒体であることができ、磁性層に結合剤を含むことができる。結合剤とは、一種以上の樹脂である。結合剤としては、塗布型磁気記録媒体の結合剤として通常使用される各種樹脂を用いることができる。例えば、結合剤としては、ポリウレタン樹脂、ポリエステル樹脂、ポリアミド樹脂、塩化ビニル樹脂、スチレン、アクリロニトリル、メチルメタクリレート等を共重合したアクリル樹脂、ニトロセルロース等のセルロース樹脂、エポキシ樹脂、フェノキシ樹脂、ポリビニルアセタール、ポリビニルブチラール等のポリビニルアルキラール樹脂等から選ばれる樹脂を単独で用いるか、または複数の樹脂を混合して用いることができる。これらの中で好ましいものはポリウレタン樹脂、アクリル樹脂、セルロース樹脂、および塩化ビニル樹脂である。これらの樹脂は、ホモポリマーでもよく、コポリマー(共重合体)でもよい。これらの樹脂は、後述する非磁性層および/またはバックコート層においても結合剤として使用することができる。
 以上の結合剤については、特開2010-24113号公報の段落0028~0031を参照できる。結合剤として使用される樹脂の平均分子量は、重量平均分子量として、例えば10,000以上200,000以下であることができる。本発明および本明細書における重量平均分子量とは、ゲルパーミエーションクロマトグラフィー(GPC)によって、下記測定条件により測定された値をポリスチレン換算して求められる値である。後述の実施例に示す結合剤の重量平均分子量は、下記測定条件によって測定された値をポリスチレン換算して求めた値である。結合剤は、強磁性粉末100.0質量部に対して、例えば1.0~30.0質量部の量で使用することができる。
 GPC装置:HLC-8120(東ソー社製)
 カラム:TSK gel Multipore HXL-M(東ソー社製、7.8mmID(Inner Diameter)×30.0cm)
 溶離液:テトラヒドロフラン(THF)
(Binder)
The magnetic recording medium can be a coating type magnetic recording medium, and the magnetic layer can contain a binder. A binder is one or more resins. As the binder, various resins usually used as a binder for a coated magnetic recording medium can be used. For example, as the binder, polyurethane resin, polyester resin, polyamide resin, vinyl chloride resin, styrene, acrylonitrile, acrylic resin obtained by copolymerizing methyl methacrylate and the like, cellulose resin such as nitrocellulose, epoxy resin, phenoxy resin, polyvinyl acetal, etc. A resin selected from a polyvinyl alkyral resin such as polyvinyl butyral can be used alone, or a plurality of resins can be mixed and used. Of these, polyurethane resin, acrylic resin, cellulose resin, and vinyl chloride resin are preferable. These resins may be homopolymers or copolymers. These resins can also be used as a binder in the non-magnetic layer and / or the backcoat layer described later.
For the above binder, paragraphs 0028 to 0031 of JP-A-2010-24113 can be referred to. The average molecular weight of the resin used as a binder can be, for example, 10,000 or more and 200,000 or less as a weight average molecular weight. The weight average molecular weight in the present invention and the present specification is a value obtained by converting a value measured under the following measurement conditions by gel permeation chromatography (GPC) into polystyrene. The weight average molecular weight of the binder shown in Examples described later is a value obtained by converting a value measured under the following measurement conditions into polystyrene. The binder can be used in an amount of, for example, 1.0 to 30.0 parts by mass with respect to 100.0 parts by mass of the ferromagnetic powder.
GPC device: HLC-8120 (manufactured by Tosoh)
Column: TSK gel Multipore HXL-M (manufactured by Tosoh Corporation, 7.8 mm ID (Inner Diameter) x 30.0 cm)
Eluent: Tetrahydrofuran (THF)
(硬化剤)
 結合剤として使用可能な樹脂とともに硬化剤を使用することもできる。硬化剤は、一態様では加熱により硬化反応(架橋反応)が進行する化合物である熱硬化性化合物であることができ、他の一態様では光照射により硬化反応(架橋反応)が進行する光硬化性化合物であることができる。硬化剤は、磁性層形成工程の中で硬化反応が進行することにより、少なくとも一部は、結合剤等の他の成分と反応(架橋)した状態で磁性層に含まれ得る。この点は、他の層を形成するために用いられる組成物が硬化剤を含む場合に、この組成物を用いて形成される層についても同様である。好ましい硬化剤は、熱硬化性化合物であり、ポリイソシアネートが好適である。ポリイソシアネートの詳細については、特開2011-216149号公報の段落0124~0125を参照できる。硬化剤は、磁性層形成用組成物中に、結合剤100.0質量部に対して例えば0~80.0質量部、磁性層の強度向上の観点からは好ましくは50.0~80.0質量部の量で使用することができる。
(Hardener)
A curing agent can also be used with a resin that can be used as a binder. The curing agent can be a thermosetting compound which is a compound in which a curing reaction (crosslinking reaction) proceeds by heating in one embodiment, and in another embodiment, a photocuring compound in which a curing reaction (crosslinking reaction) proceeds by light irradiation. It can be a sex compound. The curing agent can be contained in the magnetic layer in a state of reacting (crosslinking) with other components such as a binder, at least in part, as the curing reaction proceeds in the process of forming the magnetic layer. This point is the same for the layer formed by using this composition when the composition used for forming another layer contains a curing agent. The preferred curing agent is a thermosetting compound, and polyisocyanate is preferable. For details of the polyisocyanate, refer to paragraphs 0124 to 0125 of JP2011-216149A. The curing agent is, for example, 0 to 80.0 parts by mass with respect to 100.0 parts by mass of the binder in the composition for forming the magnetic layer, preferably 50.0 to 80.0 from the viewpoint of improving the strength of the magnetic layer. It can be used in the amount of parts by mass.
(添加剤)
 磁性層には、必要に応じて一種以上の添加剤が含まれていてもよい。添加剤は、所望の性質に応じて市販品を適宜選択して、または公知の方法で製造して、任意の量で使用することができる。添加剤としては、一例として、上記の硬化剤が挙げられる。また、磁性層に含まれる添加剤としては、非磁性粉末、潤滑剤、分散剤、分散助剤、防黴剤、帯電防止剤、酸化防止剤等を挙げることができる。例えば、潤滑剤については、特開2016-126817号公報の段落0030~0033、0035および0036を参照できる。後述する非磁性層に潤滑剤が含まれていてもよい。非磁性層に含まれ得る潤滑剤については、特開2016-126817号公報の段落0030、0031、0034~0036を参照できる。分散剤については、特開2012-133837号公報の段落0061および0071を参照できる。分散剤を非磁性層形成用組成物に添加してもよい。非磁性層形成用組成物に添加し得る分散剤については、特開2012-133837号公報の段落0061を参照できる。
(Additive)
The magnetic layer may contain one or more additives, if necessary. The additive can be used in any amount by appropriately selecting a commercially available product according to desired properties or by producing it by a known method. Examples of the additive include the above-mentioned curing agent. Examples of the additive contained in the magnetic layer include non-magnetic powders, lubricants, dispersants, dispersion aids, fungicides, antistatic agents, antioxidants and the like. For example, for the lubricant, paragraphs 0030 to 0033, 0035 and 0036 of JP-A-2016-126817 can be referred to. A lubricant may be contained in the non-magnetic layer described later. For the lubricant that can be contained in the non-magnetic layer, reference can be made to paragraphs 0030, 0031, 0034 to 0036 of JP-A-2016-126817. For the dispersant, paragraphs 0061 and 0071 of JP2012-133387A can be referred to. A dispersant may be added to the composition for forming a non-magnetic layer. For the dispersant that can be added to the composition for forming a non-magnetic layer, paragraph 0061 of Japanese Patent Application Laid-Open No. 2012-1333837 can be referred to.
 磁性層に含まれ得る非磁性粉末としては、研磨剤として機能することができる非磁性粉末を挙げることができる。研磨剤を含む磁性層に研磨剤の分散性を向上するために使用され得る添加剤の一例としては、特開2013-131285号公報の段落0012~0022に記載の分散剤を挙げることができる。 Examples of the non-magnetic powder that can be contained in the magnetic layer include non-magnetic powder that can function as an abrasive. As an example of the additive that can be used to improve the dispersibility of the abrasive in the magnetic layer containing the abrasive, the dispersant described in paragraphs 0012 to 0022 of JP2013-131285A can be mentioned.
 磁性層に含まれ得る非磁性粉末としては、磁性層表面に適度に突出する突起を形成する突起形成剤として機能することができる非磁性粉末(例えば非磁性コロイド粒子、カーボンブラック等)等が挙げられる。突起形成剤としては、例えば、平均粒子サイズが5~300nmのものを使用することができる。尚、後述の実施例に示すコロイダルシリカ(シリカコロイド粒子)の平均粒子サイズは、特開2011-048878号公報の段落0015に平均粒径の測定方法として記載されている方法により求められた値である。磁性層の突起形成剤含有量は、例えば強磁性粉末100.0質量部あたり、0.1~3.5質量部であることが好ましく、0.1~3.0質量部であることがより好ましい。磁性層の突起形成剤量を減量すると、Half-Rqの値は小さくなる傾向がある。 Examples of the non-magnetic powder that can be contained in the magnetic layer include non-magnetic powder (for example, non-magnetic colloid particles, carbon black, etc.) that can function as a protrusion forming agent that forms protrusions that appropriately project on the surface of the magnetic layer. Be done. As the protrusion forming agent, for example, one having an average particle size of 5 to 300 nm can be used. The average particle size of colloidal silica (silica colloidal particles) shown in Examples described later is a value obtained by the method described in paragraph 0015 of JP-A-2011-048878 as a method for measuring the average particle size. be. The content of the protrusion-forming agent in the magnetic layer is preferably 0.1 to 3.5 parts by mass, more preferably 0.1 to 3.0 parts by mass, for example, per 100.0 parts by mass of the ferromagnetic powder. preferable. When the amount of the protrusion forming agent in the magnetic layer is reduced, the value of Half-Rq tends to decrease.
 以上説明した磁性層は、非磁性支持体表面上に直接、または非磁性層を介して間接的に、設けることができる。 The magnetic layer described above can be provided directly on the surface of the non-magnetic support or indirectly via the non-magnetic layer.
<非磁性層>
 次に非磁性層について説明する。上記磁気記録媒体は、非磁性支持体表面上に直接磁性層を有していてもよく、非磁性支持体表面上に非磁性粉末を含む1層または複数の非磁性層を介して磁性層を有していてもよい。
<Non-magnetic layer>
Next, the non-magnetic layer will be described. The magnetic recording medium may have a magnetic layer directly on the surface of the non-magnetic support, and the magnetic layer is formed on the surface of the non-magnetic support via one layer or a plurality of non-magnetic layers containing the non-magnetic powder. You may have.
 磁性層の表面のHalf-Rqの値を小さくするためには、その上に磁性層が形成される面となる非磁性層の表面平滑性を高めることが好ましい。この点から、非磁性層に含まれる非磁性粉末として、平均粒子サイズが小さい非磁性粉末を使用することは好ましい。非磁性粉末の平均粒子サイズは、500nm以下の範囲であることが好ましく、200nm以下であることがより好ましく、100nm以下であることが更に好ましく、50nm以下であることが一層好ましい。また、非磁性粉末の分散性向上の容易性の観点からは、非磁性粉末の平均粒子サイズは、5nm以上であることが好ましく、7nm以上であることがより好ましく、10nm以上であることが更に好ましい。 In order to reduce the value of Half-Rq on the surface of the magnetic layer, it is preferable to increase the surface smoothness of the non-magnetic layer, which is the surface on which the magnetic layer is formed. From this point of view, it is preferable to use a non-magnetic powder having a small average particle size as the non-magnetic powder contained in the non-magnetic layer. The average particle size of the non-magnetic powder is preferably in the range of 500 nm or less, more preferably 200 nm or less, further preferably 100 nm or less, still more preferably 50 nm or less. Further, from the viewpoint of easiness of improving the dispersibility of the non-magnetic powder, the average particle size of the non-magnetic powder is preferably 5 nm or more, more preferably 7 nm or more, and further preferably 10 nm or more. preferable.
 非磁性層に使用される非磁性粉末は、無機粉末でも有機粉末でもよい。また、カーボンブラック等も使用できる。 The non-magnetic powder used for the non-magnetic layer may be an inorganic powder or an organic powder. In addition, carbon black or the like can also be used.
 非磁性層に使用可能なカーボンブラックについては、例えば特開2010-24113号公報の段落0040~0041を参照できる。カーボンブラックは一般に粒度分布が大きい傾向があり、分散性に乏しい傾向がある。そのため、カーボンブラックを含む非磁性層は表面平滑性が低い傾向がある。この点から、一形態では、磁性層と隣接する非磁性層としては、カーボンブラック以外の非磁性粉末を含む非磁性層を設けることが好ましい。また、非磁性層を複数設け、磁性層の最も近くに位置する非磁性層をカーボンブラック以外の非磁性粉末を含む非磁性層とすることは好ましい。例えば、非磁性支持体と磁性層との間に2層の非磁性層を設け、非磁性支持体側の非磁性層(「下層非磁性層」とも記載する。)をカーボンブラックを含む非磁性層とし、磁性層側の非磁性層(「上層非磁性層」とも記載する。)をカーボンブラック以外の非磁性粉末を含む非磁性層とすることは好ましい。また、複数種の非磁性粉末を含む非磁性層形成用組成物では、一種の非磁性粉末を含む非磁性層形成用組成物と比べて非磁性粉末の分散性は低下し易い傾向がある。この点から、複数の非磁性層を設け、各非磁性層に含まれる非磁性粉末の種類を少なくすることは好ましい。また、一形態では、複数種の非磁性粉末を含む非磁性層形成用組成物において非磁性粉末の分散性を高めるために分散剤を使用することが好ましい。かかる分散剤については後述する。 For carbon black that can be used for the non-magnetic layer, for example, paragraphs 0040 to 0041 of JP2010-24113A can be referred to. Carbon black generally tends to have a large particle size distribution and tends to have poor dispersibility. Therefore, the non-magnetic layer containing carbon black tends to have low surface smoothness. From this point of view, in one embodiment, it is preferable to provide a non-magnetic layer containing a non-magnetic powder other than carbon black as the non-magnetic layer adjacent to the magnetic layer. Further, it is preferable to provide a plurality of non-magnetic layers and to use the non-magnetic layer located closest to the magnetic layer as a non-magnetic layer containing non-magnetic powder other than carbon black. For example, two non-magnetic layers are provided between the non-magnetic support and the magnetic layer, and the non-magnetic layer on the non-magnetic support side (also referred to as “lower non-magnetic layer”) is a non-magnetic layer containing carbon black. It is preferable that the non-magnetic layer on the magnetic layer side (also referred to as "upper non-magnetic layer") is a non-magnetic layer containing a non-magnetic powder other than carbon black. Further, in the composition for forming a non-magnetic layer containing a plurality of types of non-magnetic powder, the dispersibility of the non-magnetic powder tends to be lower than that in the composition for forming a non-magnetic layer containing one kind of non-magnetic powder. From this point of view, it is preferable to provide a plurality of non-magnetic layers and reduce the types of non-magnetic powder contained in each non-magnetic layer. Further, in one form, it is preferable to use a dispersant in order to enhance the dispersibility of the non-magnetic powder in the composition for forming a non-magnetic layer containing a plurality of types of non-magnetic powder. The dispersant will be described later.
 無機粉末としては、例えば金属、金属酸化物、金属炭酸塩、金属硫酸塩、金属窒化物、金属炭化物、金属硫化物等の粉末が挙げられる。これらの非磁性粉末は、市販品として入手可能であり、公知の方法で製造することもできる。その詳細については、特開2011-216149号公報の段落0146~0150を参照できる。 Examples of the inorganic powder include powders of metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, metal sulfides and the like. These non-magnetic powders are commercially available and can also be produced by known methods. For details thereof, refer to paragraphs 0146 to 0150 of JP2011-216149A.
 非磁性粉末の一形態としては、非磁性酸化鉄粉末を挙げることができる。その上に磁性層が形成される非磁性層の表面平滑性を高めることによって磁性層の表面のHalf-Rqの値を小さくする観点から、非磁性酸化鉄粉末として粒子サイズが小さいものを使用することは好ましい。この点から、平均粒子サイズが先に記載した範囲の非磁性酸化鉄粉末を使用することが好ましく、平均粒子サイズが50nm以下の非磁性酸化鉄粉末を使用することがより好ましい。尚、非磁性酸化鉄粉末が先に記載の(1)の粒子形状を有する場合、平均粒子サイズとは、平均長軸長である。非磁性酸化鉄粉末の針状比(平均長軸長/平均短軸長)は、1.0超であることができる。非磁性酸化鉄粉末として、針状比の値が小さいものを使用することは、非磁性層の表面平滑性向上の観点から好ましい。この点から、非磁性酸化鉄粉末の針状比(平均長軸長/平均短軸長)は、3.0以下であることが好ましく、1.5以下であることがより好ましい。非磁性酸化鉄粉末としては、一形態では、α-酸化鉄粉末が好ましい。α-酸化鉄とは、主相がα相の酸化鉄である。 As one form of non-magnetic powder, non-magnetic iron oxide powder can be mentioned. From the viewpoint of reducing the value of Half-Rq on the surface of the magnetic layer by increasing the surface smoothness of the non-magnetic layer on which the magnetic layer is formed, a non-magnetic iron oxide powder having a small particle size is used. That is preferable. From this point, it is preferable to use a non-magnetic iron oxide powder having an average particle size in the range described above, and it is more preferable to use a non-magnetic iron oxide powder having an average particle size of 50 nm or less. When the non-magnetic iron oxide powder has the particle shape of (1) described above, the average particle size is the average major axis length. The needle-like ratio (average major axis length / average minor axis length) of the non-magnetic iron oxide powder can be more than 1.0. It is preferable to use a non-magnetic iron oxide powder having a small needle-like ratio from the viewpoint of improving the surface smoothness of the non-magnetic layer. From this point, the needle-like ratio (average major axis length / average minor axis length) of the non-magnetic iron oxide powder is preferably 3.0 or less, and more preferably 1.5 or less. As the non-magnetic iron oxide powder, α-iron oxide powder is preferable in one form. The α-iron oxide is iron oxide whose main phase is the α phase.
 非磁性層における非磁性粉末の含有量(充填率)は、好ましくは50~90質量%の範囲であり、より好ましくは60~90質量%の範囲である。複数の非磁性層が設けられている場合、少なくとも1層の非磁性層において非磁性粉末の含有量が上記範囲であることが好ましく、より多くの非磁性層において非磁性粉末の含有量が上記範囲であることがより好ましい。 The content (filling rate) of the non-magnetic powder in the non-magnetic layer is preferably in the range of 50 to 90% by mass, and more preferably in the range of 60 to 90% by mass. When a plurality of non-magnetic layers are provided, the content of the non-magnetic powder in at least one non-magnetic layer is preferably in the above range, and the content of the non-magnetic powder in more non-magnetic layers is described above. It is more preferably in the range.
 非磁性層は、非磁性粉末を含み、非磁性粉末とともに結合剤を含むこともできる。非磁性層の結合剤、添加剤等のその他詳細は、非磁性層に関する公知技術が適用できる。また、例えば、結合剤の種類および含有量、添加剤の種類および含有量等に関しては、磁性層に関する公知技術も適用できる。 The non-magnetic layer contains a non-magnetic powder, and can also contain a binder together with the non-magnetic powder. For other details such as the binder and additives of the non-magnetic layer, known techniques relating to the non-magnetic layer can be applied. Further, for example, with respect to the type and content of the binder, the type and content of the additive, and the like, known techniques relating to the magnetic layer can also be applied.
 非磁性層に含まれ得る添加剤としては、非磁性粉末の分散性向上に寄与し得る分散剤を挙げることができる。かかる分散剤としては、例えば、RCOOH(Rはアルキル基またはアルケニル基)で表される脂肪酸(例えばカプリル酸、カプリン酸、ラウリン酸、ミリスチン酸、パルミチン酸、ステアリン酸、ベヘン酸、オレイン酸、エライジン酸、リノール酸、リノレン酸等);上記脂肪酸のアルカリ金属塩またはアルカリ土類金属塩;上記脂肪酸のエステル;上記脂肪酸のエステルのフッ素を含有した化合物;上記脂肪酸のアミド;ポリアルキレンオキサイドアルキルリン酸エステル;レシチン;トリアルキルポリオレフィンオキシ第四級アンモニウム塩(含有されるアルキル基は炭素数1~5のアルキル基、含有されるオレフィンはエチレン、プロピレン等);フェニルフォスフォン酸;銅フタロシアニン等を使用することができる。これらは、一種のみ使用してもよく、二種以上を併用してもよい。分散剤の含有量は、非磁性粉末100.0質量部に対して、0.2~5.0質量部であることが好ましい。 Examples of the additive that can be contained in the non-magnetic layer include a dispersant that can contribute to improving the dispersibility of the non-magnetic powder. Examples of such dispersants include fatty acids represented by RCOOH (where R is an alkyl group or an alkenyl group) (eg, capric acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, and eridine). Acid, linoleic acid, linolenic acid, etc.); Alkali metal salt or alkaline earth metal salt of the above fatty acid; Ester of the above fatty acid; Fluorine-containing compound of the ester of the above fatty acid; Amid of the above fatty acid; Polyalkylene oxide alkyl phosphate Ester; Recitin; Trialkyl polyolefin oxyquaternary ammonium salt (alkyl group contained is an alkyl group having 1 to 5 carbon atoms, olefin contained is ethylene, propylene, etc.); phenylphosphonic acid; copper phthalocyanine, etc. is used. can do. These may be used alone or in combination of two or more. The content of the dispersant is preferably 0.2 to 5.0 parts by mass with respect to 100.0 parts by mass of the non-magnetic powder.
 また、添加剤の一例として、有機三級アミンを挙げることができる。有機三級アミンについては、特開2013-049832号公報の段落0011~0018および0021を参照できる。有機三級アミンは、カーボンブラックの分散性向上に寄与し得る。有機三級アミンによりカーボンブラックの分散性を高めるための組成物の処方等については、同公報の段落0022~0024、0027を参照できる。 Further, as an example of the additive, an organic tertiary amine can be mentioned. For the organic tertiary amine, paragraphs 0011 to 0018 and 0021 of JP2013-049832A can be referred to. Organic tertiary amines can contribute to improving the dispersibility of carbon black. For the formulation of a composition for enhancing the dispersibility of carbon black with an organic tertiary amine, refer to paragraphs 0022 to 0024 and 0027 of the same publication.
 上記アミンは、より好ましくはトリアルキルアミンである。トリアルキルアミンが有するアルキル基は、好ましくは炭素数1~18のアルキル基である。トリアルキルアミンが有する3つのアルキル基は、同一であっても異なっていてもよい。アルキル基の詳細については、特開2013-049832号公報の段落0015~0016を参照できる。トリアルキルアミンとしては、トリオクチルアミンが特に好ましい。 The amine is more preferably a trialkylamine. The alkyl group contained in the trialkylamine is preferably an alkyl group having 1 to 18 carbon atoms. The three alkyl groups of the trialkylamine may be the same or different. For details of the alkyl group, refer to paragraphs 0015 to 0016 of JP2013-049832A. As the trialkylamine, trioctylamine is particularly preferable.
 本発明および本明細書において、非磁性層には、非磁性粉末とともに、例えば不純物として、または意図的に、少量の強磁性粉末を含む実質的に非磁性な層も包含されるものとする。ここで実質的に非磁性な層とは、この層の残留磁束密度が10mT以下であるか、保磁力が7.96kA/m(100Oe)以下であるか、または、残留磁束密度が10mT以下であり、かつ保磁力が7.96kA/m(100Oe)以下である層をいうものとする。非磁性層は、残留磁束密度および保磁力を持たないことが好ましい。 In the present invention and the present specification, the non-magnetic layer includes not only the non-magnetic powder but also a substantially non-magnetic layer containing a small amount of ferromagnetic powder, for example, as an impurity or intentionally. Here, the substantially non-magnetic layer means that the residual magnetic flux density of this layer is 10 mT or less, the coercive force is 7.96 kA / m (100 Oe) or less, or the residual magnetic flux density is 10 mT or less. It refers to a layer having a coercive force of 7.96 kA / m (100 Oe) or less. The non-magnetic layer preferably has no residual magnetic flux density and coercive force.
<非磁性支持体>
 次に、非磁性支持体について説明する。非磁性支持体(以下、単に「支持体」とも記載する。)としては、二軸延伸を行ったポリエチレンテレフタレート、ポリエチレンナフタレート、ポリアミド、ポリアミドイミド、芳香族ポリアミド等の公知のものが挙げられる。これらの中でもポリエチレンテレフタレート、ポリエチレンナフタレートおよびポリアミドが好ましい。これらの支持体には、あらかじめコロナ放電、プラズマ処理、易接着処理、熱処理等を行ってもよい。
<Non-magnetic support>
Next, the non-magnetic support will be described. Examples of the non-magnetic support (hereinafter, also simply referred to as “support”) include known biaxially stretched polyethylene terephthalates, polyethylene naphthalates, polyamides, polyamideimides, aromatic polyamides and the like. Among these, polyethylene terephthalate, polyethylene naphthalate and polyamide are preferable. These supports may be subjected to corona discharge, plasma treatment, easy adhesion treatment, heat treatment and the like in advance.
<バックコート層>
 上記磁気記録媒体は、非磁性支持体の磁性層を有する表面側とは反対の表面側に、非磁性粉末を含むバックコート層を有することもでき、有さなくてもよい。バックコート層には、カーボンブラックおよび無機粉末のいずれか一方または両方が含有されていることが好ましい。バックコート層は、結合剤を含むことができ、添加剤を含むこともできる。バックコート層の結合剤および添加剤については、バックコート層に関する公知技術を適用することができ、磁性層および/または非磁性層の処方に関する公知技術を適用することもできる。例えば、特開2006-331625号公報の段落0018~0020および米国特許第7,029,774号明細書の第4欄65行目~第5欄38行目の記載を、バックコート層について参照できる。
<Back coat layer>
The magnetic recording medium may or may not have a backcoat layer containing non-magnetic powder on the surface side opposite to the surface side having the magnetic layer of the non-magnetic support. The backcoat layer preferably contains one or both of carbon black and inorganic powder. The backcoat layer can contain binders and can also contain additives. For the binder and additives of the backcoat layer, known techniques relating to the backcoat layer can be applied, and known techniques relating to the formulation of the magnetic layer and / or the non-magnetic layer can also be applied. For example, paragraphs 0018 to 0020 of JP-A-2006-331625 and the description of US Pat. No. 7,029,774, column 4, lines 65 to 5, line 38 can be referred to for the backcoat layer. ..
<各種厚み>
 磁気記録媒体の厚み(総厚)に関して、近年の情報量の莫大な増大に伴い、磁気記録媒体には記録容量を高めること(高容量化)が求められている。高容量化のための手段としては、磁気記録媒体の厚みを薄くし(以下、「薄型化」とも記載する。)、磁気テープカートリッジ1巻あたりに収容される磁気テープ長を増すことが挙げられる。この点から、上記磁気記録媒体の厚み(総厚)は、5.6μm以下であることが好ましく、5.5μm以下であることがより好ましく、5.4μm以下であることがより好ましく、5.3μm以下であることが更に好ましく、5.2μm以下であることが一層好ましい。また、ハンドリングの容易性の観点からは、磁気記録媒体の厚みは3.0μm以上であることが好ましく、3.5μm以上であることがより好ましい。
<Various thickness>
With regard to the thickness (total thickness) of the magnetic recording medium, with the enormous increase in the amount of information in recent years, the magnetic recording medium is required to have an increased recording capacity (higher capacity). As a means for increasing the capacity, the thickness of the magnetic recording medium may be reduced (hereinafter, also referred to as “thinning”), and the length of the magnetic tape accommodated in one magnetic tape cartridge may be increased. .. From this point, the thickness (total thickness) of the magnetic recording medium is preferably 5.6 μm or less, more preferably 5.5 μm or less, and even more preferably 5.4 μm or less. It is more preferably 3 μm or less, and even more preferably 5.2 μm or less. Further, from the viewpoint of ease of handling, the thickness of the magnetic recording medium is preferably 3.0 μm or more, and more preferably 3.5 μm or more.
 例えば、磁気テープの厚み(総厚)は、以下の方法によって測定することができる。
 磁気テープの任意の部分からテープサンプル(例えば長さ5~10cm)を10枚切り出し、これらテープサンプルを重ねて厚みを測定する。測定された厚みを10分の1して得られた値(テープサンプル1枚当たりの厚み)を、テープ厚みとする。上記厚み測定は、0.1μmオーダーでの厚み測定が可能な公知の測定器を用いて行うことができる。
For example, the thickness (total thickness) of the magnetic tape can be measured by the following method.
Ten tape samples (for example, 5 to 10 cm in length) are cut out from an arbitrary part of the magnetic tape, and these tape samples are stacked and the thickness is measured. The value obtained by dividing the measured thickness by 1/10 (thickness per tape sample) is defined as the tape thickness. The thickness measurement can be performed using a known measuring instrument capable of measuring the thickness on the order of 0.1 μm.
 非磁性支持体の厚みは、好ましくは3.0~5.0μmである。 The thickness of the non-magnetic support is preferably 3.0 to 5.0 μm.
 磁性層の厚みは、用いる磁気ヘッドの飽和磁化量、ヘッドギャップ長、記録信号の帯域等により最適化することができ、一般には0.01μm~0.15μmであり、高密度記録化の観点から、好ましくは0.02μm~0.12μmであり、更に好ましくは0.03μm~0.1μmである。磁性層は少なくとも一層あればよく、磁性層を異なる磁気特性を有する二層以上に分離してもかまわず、公知の重層磁性層に関する構成が適用できる。二層以上に分離する場合の磁性層の厚みとは、これらの層の合計厚みとする。この点は、複数の非磁性層を有する磁気記録媒体における非磁性層の厚みについても同様である。 The thickness of the magnetic layer can be optimized by the saturation magnetization amount of the magnetic head used, the head gap length, the band of the recording signal, etc., and is generally 0.01 μm to 0.15 μm, from the viewpoint of high-density recording. It is preferably 0.02 μm to 0.12 μm, and more preferably 0.03 μm to 0.1 μm. The magnetic layer may be at least one layer, and the magnetic layer may be separated into two or more layers having different magnetic properties, and a known configuration relating to a multi-layer magnetic layer can be applied. The thickness of the magnetic layer when separated into two or more layers is the total thickness of these layers. This point also applies to the thickness of the non-magnetic layer in the magnetic recording medium having the plurality of non-magnetic layers.
 非磁性層の厚みについては、厚い非磁性層を形成するほど、非磁性層形成用組成物の塗布工程および乾燥工程で非磁性粉末の粒子の存在状態が不均一になり易く、各位置での厚みの違いが大きくなって非磁性層の表面が粗くなる傾向がある。磁性層表面のHalf-Rqの値を小さくするためには非磁性層の表面平滑性が高いことが好ましい傾向があり、この観点からは、非磁性層の厚みは1.5μm以下であることが好ましく、1.0μm以下であることがより好ましい。また、非磁性層の厚みは、非磁性層形成用組成物の塗布の均一性向上の観点からは、0.05μm以上であることが好ましく、0.1μm以上であることがより好ましい。 Regarding the thickness of the non-magnetic layer, the thicker the non-magnetic layer is formed, the more likely the non-magnetic powder particles are present to be non-uniform in the coating step and the drying step of the composition for forming the non-magnetic layer, and the presence state of the particles of the non-magnetic powder tends to be non-uniform at each position. The difference in thickness tends to increase and the surface of the non-magnetic layer tends to become rough. In order to reduce the value of Half-Rq on the surface of the magnetic layer, it tends to be preferable that the surface smoothness of the non-magnetic layer is high, and from this viewpoint, the thickness of the non-magnetic layer is 1.5 μm or less. It is preferably 1.0 μm or less, and more preferably 1.0 μm or less. Further, the thickness of the non-magnetic layer is preferably 0.05 μm or more, more preferably 0.1 μm or more, from the viewpoint of improving the uniformity of coating of the composition for forming the non-magnetic layer.
 バックコート層の厚みは、0.9μm以下が好ましく、0.1~0.7μmが更に好ましい。
 磁性層の厚み等の各種厚みは、以下の方法により求めることができる。
 磁気記録媒体の厚み方向の断面を、イオンビームにより露出させた後、露出した断面において走査型電子顕微鏡による断面観察を行う。断面観察において任意の2箇所において求められた厚みの算術平均として、各種厚みを求めることができる。または、各種厚みは、製造条件等から算出される設計厚みとして求めることもできる。
The thickness of the backcoat layer is preferably 0.9 μm or less, more preferably 0.1 to 0.7 μm.
Various thicknesses such as the thickness of the magnetic layer can be obtained by the following methods.
After exposing the cross section of the magnetic recording medium in the thickness direction with an ion beam, the cross section of the exposed cross section is observed with a scanning electron microscope. Various thicknesses can be obtained as the arithmetic mean of the thicknesses obtained at any two points in the cross-sectional observation. Alternatively, various thicknesses can be obtained as design thicknesses calculated from manufacturing conditions and the like.
<製造工程>
(各層形成用組成物の調製)
 磁性層、非磁性層またはバックコート層を形成するための組成物を調製する工程は、通常、少なくとも混練工程、分散工程、およびこれらの工程の前後に必要に応じて設けた混合工程を含むことができる。個々の工程はそれぞれ二段階以上に分かれていてもかまわない。各層形成用組成物の調製に用いられる成分は、どの工程の最初または途中で添加してもかまわない。溶媒としては、塗布型磁気記録媒体の製造に通常用いられる各種溶媒の一種または二種以上を用いることができる。溶媒については、例えば特開2011-216149号公報の段落0153を参照できる。また、個々の成分を2つ以上の工程で分割して添加してもかまわない。例えば、結合剤を混練工程、分散工程および分散後の粘度調整のための混合工程で分割して投入してもよい。上記磁気記録媒体を製造するためには、公知の製造技術を各種工程において用いることができる。混練工程ではオープンニーダ、連続ニーダ、加圧ニーダ、エクストルーダ等の強い混練力をもつものを使用することが好ましい。混練処理の詳細については、特開平1-106338号公報および特開平1-79274号公報を参照できる。分散機は公知のものを使用することができる。各層形成用組成物を調製する任意の段階において、公知の方法によってろ過を行ってもよい。ろ過は、例えばフィルタろ過によって行うことができる。ろ過に用いるフィルタとしては、例えば孔径0.01~3μmのフィルタ(例えばガラス繊維製フィルタ、ポリプロピレン製フィルタ等)を用いることができる。
<Manufacturing process>
(Preparation of composition for forming each layer)
The step of preparing the composition for forming the magnetic layer, the non-magnetic layer or the backcoat layer usually includes at least a kneading step, a dispersion step, and a mixing step provided before and after these steps as necessary. Can be done. Each process may be divided into two or more stages. The components used in the preparation of each layer-forming composition may be added at the beginning or in the middle of any step. As the solvent, one kind or two or more kinds of various solvents usually used for producing a coating type magnetic recording medium can be used. For the solvent, for example, paragraph 0153 of JP-A-2011-216149 can be referred to. Further, the individual components may be added separately in two or more steps. For example, the binder may be divided and added in a kneading step, a dispersion step and a mixing step for adjusting the viscosity after dispersion. In order to manufacture the magnetic recording medium, known manufacturing techniques can be used in various steps. In the kneading step, it is preferable to use an open kneader, a continuous kneader, a pressurized kneader, an extruder or the like having a strong kneading force. For details of the kneading process, Japanese Patent Application Laid-Open No. 1-106338 and Japanese Patent Application Laid-Open No. 1-79274 can be referred to. A known disperser can be used. Filtration may be performed by a known method at any stage of preparing each layer-forming composition. Filtration can be performed, for example, by filter filtration. As the filter used for filtration, for example, a filter having a pore size of 0.01 to 3 μm (for example, a glass fiber filter, a polypropylene filter, etc.) can be used.
(塗布工程)
 磁性層は、磁性層形成用組成物を、非磁性支持体表面上に直接塗布するか、または非磁性層形成用組成物と逐次もしくは同時に重層塗布することにより形成することができる。バックコート層は、バックコート層形成用組成物を、非磁性支持体の非磁性層および/または磁性層を有する(または非磁性層および/または磁性層が追って設けられる)表面とは反対側の表面に塗布することにより形成することができる。各層形成のための塗布の詳細については、特開2010-231843号公報の段落0066を参照できる。
(Applying process)
The magnetic layer can be formed by directly applying the composition for forming a magnetic layer on the surface of a non-magnetic support, or by applying multiple layers sequentially or simultaneously with the composition for forming a non-magnetic layer. In the backcoat layer, the composition for forming the backcoat layer is placed on the opposite side of the surface having the non-magnetic layer and / or the magnetic layer of the non-magnetic support (or the non-magnetic layer and / or the magnetic layer is additionally provided). It can be formed by applying it to the surface. For details of the coating for forming each layer, refer to paragraph 0066 of Japanese Patent Application Laid-Open No. 2010-231843.
(その他の工程)
 塗布工程後には、乾燥処理、磁性層の配向処理、表面平滑化処理(カレンダ処理)等の各種処理を行うことができる。各種工程については、例えば特開2010-24113号公報の段落0052~0057等の公知技術を参照できる。例えば、磁性層形成用組成物の塗布層には、この塗布層が湿潤状態にあるうちに配向処理を施すことができる。配向処理については、特開2010-231843号公報の段落0067の記載をはじめとする各種公知技術を適用することができる。例えば、垂直配向処理は、異極対向磁石を用いる方法等の公知の方法によって行うことができる。配向ゾーンでは、乾燥風の温度、風量および/または配向ゾーンにおける上記塗布層を形成した非磁性支持体の搬送速度によって塗布層の乾燥速度を制御することができる。また、配向ゾーンに搬送する前に塗布層を予備乾燥させてもよい。また、カレンダ処理については、カレンダ条件を強化すると、磁性層の表面のHalf-Rqの値は小さくなる傾向がある。カレンダ条件としては、カレンダ処理を行う回数(以下、「カレンダ回数」とも記載する。)、カレンダ圧力、カレンダ温度(カレンダロールの表面温度)、カレンダ速度、カレンダロールの硬度等が挙げられる。カレンダ回数を増やすほど、カレンダ処理は強化される。カレンダ圧力、カレンダ温度およびカレンダロールの硬度は、これらの値を大きくするほどカレンダ処理は強化され、カレンダ速度は遅くするほどカレンダ処理は強化される。例えば、カレンダ圧力(線圧)は200~500kg/cmであることができ、250~350kg/cmであることが好ましい。カレンダ温度(カレンダロールの表面温度)は、例えば85~120℃であることができ、90~110℃であることが好ましく、カレンダ速度は、例えば50~300m/分であることができ、50~200m/分であることが好ましい。
 各種工程を経ることによって、長尺状の磁気記録媒体原反を得ることができる。得られた磁気記録媒体原反は、公知の裁断機によって、例えば、磁気テープカートリッジに巻装すべき磁気テープの幅に裁断(スリット)される。上記の幅は規格にしたがい決定され、通常、1/2インチである。1/2インチ=12.65mmである。
 スリットして得られた磁気記録媒体には、通常、サーボパターンが形成される。サーボパターンについて、詳細は後述する。
(Other processes)
After the coating step, various treatments such as a drying treatment, a magnetic layer orientation treatment, and a surface smoothing treatment (calendar treatment) can be performed. For various steps, for example, known techniques such as paragraphs 0052 to 0057 of JP-A-2010-24113 can be referred to. For example, the coating layer of the composition for forming a magnetic layer can be subjected to an orientation treatment while the coating layer is in a wet state. Various known techniques such as the description in paragraph 0067 of JP-A-2010-231843 can be applied to the alignment treatment. For example, the vertical alignment treatment can be performed by a known method such as a method using a magnet opposite to the opposite pole. In the alignment zone, the drying rate of the coating layer can be controlled by the temperature and air volume of the drying air and / or the transport speed of the non-magnetic support forming the coating layer in the alignment zone. In addition, the coating layer may be pre-dried before being transported to the alignment zone. Further, regarding the calendar treatment, when the calendar conditions are strengthened, the value of Half-Rq on the surface of the magnetic layer tends to decrease. Examples of the calendar conditions include the number of times the calendar treatment is performed (hereinafter, also referred to as “number of calendars”), the calendar pressure, the calendar temperature (surface temperature of the calendar roll), the calendar speed, the hardness of the calendar roll, and the like. The more calendars you have, the stronger the calendaring process. As for the calendar pressure, the calendar temperature, and the hardness of the calendar roll, the larger these values are, the stronger the calendar treatment is, and the slower the calendar speed is, the stronger the calendar treatment is. For example, the calendar pressure (linear pressure) can be 200 to 500 kg / cm, preferably 250 to 350 kg / cm. The calendar temperature (surface temperature of the calendar roll) can be, for example, 85-120 ° C, preferably 90-110 ° C, and the calendar speed can be, for example, 50-300 m / min, 50-. It is preferably 200 m / min.
By going through various steps, a long magnetic recording medium raw fabric can be obtained. The obtained magnetic recording medium raw material is cut (slit) by a known cutting machine to, for example, the width of the magnetic tape to be wound around the magnetic tape cartridge. The above width is determined according to the standard and is usually 1/2 inch. 1/2 inch = 12.65 mm.
A servo pattern is usually formed on the magnetic recording medium obtained by slitting. The details of the servo pattern will be described later.
(熱処理)
 一形態では、上記磁気記録媒体は、以下のような熱処理を経て製造された磁気テープであることができる。また、他の一形態では、上記磁気記録媒体は、以下のような熱処理を経ずに製造された磁気テープであることができる。
(Heat treatment)
In one form, the magnetic recording medium can be a magnetic tape manufactured through the following heat treatment. Further, in another embodiment, the magnetic recording medium can be a magnetic tape manufactured without undergoing the following heat treatment.
 熱処理としては、スリットして規格にしたがい決定された幅に裁断された磁気テープを、芯状部材に巻き付け、巻き付けた状態で行う熱処理を行うことができる。 As the heat treatment, a magnetic tape that has been slit and cut to a width determined according to the standard can be wound around a core-shaped member, and the heat treatment can be performed in the wound state.
 一形態では、熱処理用の芯状部材(以下、「熱処理用巻芯」と呼ぶ。)に磁気テープを巻き付けた状態で上記熱処理を行い、熱処理後の磁気テープを磁気テープカートリッジのリールに巻き取り、磁気テープがリールに巻装された磁気テープカートリッジを作製することができる。
 熱処理用巻芯は、金属製、樹脂製、紙製等であることができる。熱処理用巻芯の材料は、スポーキング等の巻き故障の発生を抑制する観点から、剛性が高い材料であることが好ましい。この点から、熱処理用巻芯は、金属製または樹脂製であることが好ましい。また、剛性の指標として、熱処理用巻芯の材料の曲げ弾性率は0.2GPa(ギガパスカル)以上が好ましく、0.3GPa以上がより好ましい。他方、高剛性の材料は一般に高価であるため、巻き故障の発生を抑制できる剛性を超える剛性を有する材料の熱処理用巻芯を用いることはコスト増につながる。以上の点を考慮すると、熱処理用巻芯の材料の曲げ弾性率は250GPa以下が好ましい。曲げ弾性率は、ISO(International Organization for Standardization)178にしたがい測定される値であり、各種材料の曲げ弾性率は公知である。また、熱処理用巻芯は中実または中空の芯状部材であることができる。中空状の場合、剛性を維持する観点から、肉厚は2mm以上であることが好ましい。また、熱処理用巻芯は、フランジを有していてもよく、有さなくてもよい。
 熱処理用巻芯に巻き付ける磁気テープとして最終的に磁気テープカートリッジに収容する長さ(以下、「最終製品長」と呼ぶ。)以上の磁気テープを準備し、この磁気テープを熱処理用巻芯に巻き付けた状態で熱処理環境下に置くことにより熱処理を行うことが好ましい。熱処理用巻芯に巻き付ける磁気テープ長は最終製品長以上であり、熱処理用巻芯等への巻き取りの容易性の観点からは、「最終製品長+α」とすることが好ましい。このαは、上記の巻き取りの容易性の観点からは5m以上であることが好ましい。熱処理用巻芯への巻き取り時のテンションは、0.1N(ニュートン)以上が好ましい。また、過度な変形が発生することを抑制する観点から、熱処理用巻芯への巻き取り時のテンションは1.5N以下が好ましく、1.0N以下がより好ましい。熱処理用巻芯の外径は、巻き付けの容易性およびコイリング(長手方向のカール)の抑制の観点から、20mm以上が好ましく、40mm以上がより好ましい。また、熱処理用巻芯の外径は100mm以下が好ましく、90mm以下がより好ましい。熱処理用巻芯の幅は、この巻芯に巻き付ける磁気テープの幅以上であればよい。また、熱処理後、熱処理用巻芯から磁気テープを取り外す際には、取り外す操作中に意図しないテープ変形が生じることを抑制するために、磁気テープおよび熱処理用巻芯が十分冷却された後に磁気テープを熱処理用巻芯から取り外すことが好ましい。取り外した磁気テープは、一度別の巻芯(「一時巻き取り用巻芯」と呼ぶ。)に巻き取り、その後、一時巻き取り用巻芯から磁気テープカートリッジのリール(一般に外径は40~50mm程度)へ磁気テープを巻き取ることが好ましい。これにより、熱処理時の磁気テープの熱処理用巻芯に対する内側と外側との関係を維持して、磁気テープカートリッジのリールへ磁気テープを巻き取ることができる。一時巻き取り用巻芯の詳細およびこの巻芯へ磁気テープを巻き取る際のテンションについては、熱処理用巻芯に関する先の記載を参照できる。上記熱処理を「最終製品長+α」の長さの磁気テープに施す形態においては、任意の段階で、「+α」の長さ分を切り取ればよい。例えば、一形態では、一時巻き取り用巻芯から磁気テープカートリッジのリールへ最終製品長分の磁気テープを巻き取り、残りの「+α」の長さ分を切り取ればよい。切り取って廃棄される部分を少なくする観点からは、上記αは20m以下であることが好ましい。
In one form, the heat treatment is performed with the magnetic tape wound around a core-shaped member for heat treatment (hereinafter referred to as “heat treatment winding core”), and the heat-treated magnetic tape is wound around a reel of a magnetic tape cartridge. , A magnetic tape cartridge in which a magnetic tape is wound on a reel can be manufactured.
The heat treatment core can be made of metal, resin, paper, or the like. The material of the core for heat treatment is preferably a material having high rigidity from the viewpoint of suppressing the occurrence of winding failure such as spoking. From this point, the heat treatment core is preferably made of metal or resin. Further, as an index of rigidity, the flexural modulus of the material of the heat treatment core is preferably 0.2 GPa (gigapascal) or more, and more preferably 0.3 GPa or more. On the other hand, since a high-rigidity material is generally expensive, using a heat-treating winding core of a material having a rigidity exceeding the rigidity capable of suppressing the occurrence of winding failure leads to an increase in cost. Considering the above points, the flexural modulus of the material of the heat treatment core is preferably 250 GPa or less. The flexural modulus is a value measured according to ISO (International Organization for Standardization) 178, and the flexural modulus of various materials is known. Further, the heat treatment winding core can be a solid or hollow core-shaped member. In the case of a hollow shape, the wall thickness is preferably 2 mm or more from the viewpoint of maintaining rigidity. Further, the heat treatment core may or may not have a flange.
As a magnetic tape to be wound around the heat treatment core, prepare a magnetic tape having a length longer than the length finally accommodated in the magnetic tape cartridge (hereinafter referred to as "final product length"), and wind this magnetic tape around the heat treatment core. It is preferable to perform the heat treatment by placing the magnet in a heat treatment environment. The length of the magnetic tape wound around the heat treatment core is longer than the final product length, and from the viewpoint of ease of winding around the heat treatment core or the like, it is preferably "final product length + α". This α is preferably 5 m or more from the viewpoint of ease of winding. The tension at the time of winding to the heat treatment core is preferably 0.1 N (Newton) or more. Further, from the viewpoint of suppressing the occurrence of excessive deformation, the tension at the time of winding to the heat treatment winding core is preferably 1.5 N or less, more preferably 1.0 N or less. The outer diameter of the heat treatment core is preferably 20 mm or more, more preferably 40 mm or more, from the viewpoint of ease of winding and suppression of coiling (curl in the longitudinal direction). The outer diameter of the heat treatment core is preferably 100 mm or less, more preferably 90 mm or less. The width of the heat treatment core may be equal to or larger than the width of the magnetic tape wound around the core. Further, when the magnetic tape is removed from the heat treatment core after the heat treatment, the magnetic tape and the heat treatment core are sufficiently cooled before the magnetic tape is sufficiently cooled in order to prevent unintended tape deformation during the removal operation. Is preferably removed from the heat treatment core. The removed magnetic tape is once wound on another winding core (referred to as "temporary winding core"), and then from the temporary winding core to the reel of the magnetic tape cartridge (generally, the outer diameter is 40 to 50 mm). It is preferable to wind the magnetic tape around. As a result, the magnetic tape can be wound around the reel of the magnetic tape cartridge while maintaining the relationship between the inside and the outside of the magnetic tape with respect to the heat treatment core during the heat treatment. For details of the temporary winding core and the tension when winding the magnetic tape around this winding core, refer to the previous description regarding the heat treatment winding core. In the form in which the above heat treatment is applied to a magnetic tape having a length of "final product length + α", the length of "+ α" may be cut off at an arbitrary stage. For example, in one form, the magnetic tape for the final product length may be wound from the temporary winding core to the reel of the magnetic tape cartridge, and the remaining “+ α” length may be cut off. From the viewpoint of reducing the portion to be cut and discarded, the α is preferably 20 m or less.
 上記のように芯状部材に巻き付けた状態で行われる熱処理の具体的形態について、以下に説明する。
 熱処理を行う雰囲気温度(以下、「熱処理温度」と呼ぶ。)は、40℃以上が好ましく、50℃以上がより好ましい。一方、過度な変形を抑制する観点からは、熱処理温度は75℃以下が好ましく、70℃以下がより好ましく、65℃以下が更に好ましい。
 熱処理を行う雰囲気の重量絶対湿度は、0.1g/kg Dry air以上が好ましく、1g/kg Dry air以上がより好ましい。重量絶対湿度が上記範囲の雰囲気は、水分を低減するための特殊な装置を用いずに準備できるため好ましい。一方、重量絶対湿度は、結露が生じて作業性が低下することを抑制する観点からは、70g/kg Dry air以下が好ましく、66g/kg Dry air以下がより好ましい。熱処理時間は、0.3時間以上が好ましく、0.5時間以上がより好ましい。また、熱処理時間は、生産効率の観点からは、48時間以下が好ましい。
The specific form of the heat treatment performed in the state of being wound around the core-shaped member as described above will be described below.
The atmospheric temperature at which the heat treatment is performed (hereinafter, referred to as “heat treatment temperature”) is preferably 40 ° C. or higher, more preferably 50 ° C. or higher. On the other hand, from the viewpoint of suppressing excessive deformation, the heat treatment temperature is preferably 75 ° C. or lower, more preferably 70 ° C. or lower, and even more preferably 65 ° C. or lower.
The weight absolute humidity of the atmosphere in which the heat treatment is performed is preferably 0.1 g / kg Dry air or more, and more preferably 1 g / kg Dry air or more. Atmospheres with a weight absolute humidity in the above range are preferable because they can be prepared without using a special device for reducing moisture. On the other hand, the weight absolute humidity is preferably 70 g / kg Dry air or less, and more preferably 66 g / kg Dry air or less, from the viewpoint of suppressing the occurrence of dew condensation and deterioration of workability. The heat treatment time is preferably 0.3 hours or more, more preferably 0.5 hours or more. The heat treatment time is preferably 48 hours or less from the viewpoint of production efficiency.
(サーボパターンの形成)
 上記磁気記録媒体は、テープ状の磁気記録媒体(即ち磁気テープ)であることができ、またはディスク状の磁気記録媒体(即ち磁気ディスク)であることができる。いずれの形態においても、磁性層はサーボパターンを有することができる。「サーボパターンの形成」は、「サーボ信号の記録」ということもできる。以下に、磁気テープを例として、サーボパターンの形成について説明する。
(Formation of servo pattern)
The magnetic recording medium can be a tape-shaped magnetic recording medium (that is, a magnetic tape) or a disk-shaped magnetic recording medium (that is, a magnetic disk). In any form, the magnetic layer can have a servo pattern. "Formation of servo pattern" can also be referred to as "recording of servo signal". Hereinafter, the formation of the servo pattern will be described using a magnetic tape as an example.
 サーボパターンは、通常、磁気テープの長手方向に沿って形成される。サーボ信号を利用する制御(サーボ制御)の方式としては、タイミングベースサーボ(TBS)、アンプリチュードサーボ、周波数サーボ等が挙げられる。 The servo pattern is usually formed along the longitudinal direction of the magnetic tape. Examples of the control (servo control) method using a servo signal include timing-based servo (TBS), amplified servo, frequency servo, and the like.
 ECMA(European Computer Manufacturers Association)―319(June 2001)に示される通り、LTO(Linear Tape-Open)規格に準拠した磁気テープ(一般に「LTOテープ」と呼ばれる。)では、タイミングベースサーボ方式が採用されている。このタイミングベースサーボ方式において、サーボパターンは、互いに非平行な一対の磁気ストライプ(「サーボストライプ」とも呼ばれる。)が、磁気テープの長手方向に連続的に複数配置されることによって構成されている。本発明および本明細書において、「タイミングベースサーボパターン」とは、タイミングベースサーボ方式のサーボシステムにおけるヘッドトラッキングを可能とするサーボパターンをいう。上記のように、サーボパターンが互いに非平行な一対の磁気ストライプにより構成される理由は、サーボパターン上を通過するサーボ信号読み取り素子に、その通過位置を教えるためである。具体的には、上記の一対の磁気ストライプは、その間隔が磁気テープの幅方向に沿って連続的に変化するように形成されており、サーボ信号読み取り素子がその間隔を読み取ることによって、サーボパターンとサーボ信号読み取り素子との相対位置を知ることができる。この相対位置の情報が、データトラックのトラッキングを可能にする。そのために、サーボパターン上には、通常、磁気テープの幅方向に沿って、複数のサーボトラックが設定されている。 As shown in ECMA (European Computer Manufacturers Association) -319 (June 2001), the timing-based servo method is adopted in the magnetic tape (generally called "LTO tape") compliant with the LTO (Linear Tape-Open) standard. ing. In this timing-based servo system, the servo pattern is composed of a pair of magnetic stripes (also referred to as "servo stripes") that are non-parallel to each other and are continuously arranged in a plurality in the longitudinal direction of the magnetic tape. In the present invention and the present specification, the "timing-based servo pattern" refers to a servo pattern that enables head tracking in a timing-based servo system servo system. As described above, the reason why the servo pattern is composed of a pair of magnetic stripes that are non-parallel to each other is to teach the passing position to the servo signal reading element passing on the servo pattern. Specifically, the pair of magnetic stripes described above are formed so that their spacing changes continuously along the width direction of the magnetic tape, and the servo signal reading element reads the spacing to obtain a servo pattern. And the relative position of the servo signal reading element can be known. This relative position information allows tracking of the data track. Therefore, a plurality of servo tracks are usually set on the servo pattern along the width direction of the magnetic tape.
 サーボバンドは、磁気テープの長手方向に連続するサーボパターンにより構成される。このサーボバンドは、通常、磁気テープに複数本設けられる。例えば、LTOテープにおいて、その数は5本である。隣接する2本のサーボバンドに挟まれた領域が、データバンドである。データバンドは、複数のデータトラックで構成されており、各データトラックは、各サーボトラックに対応している。 The servo band is composed of a servo pattern that is continuous in the longitudinal direction of the magnetic tape. A plurality of these servo bands are usually provided on the magnetic tape. For example, in LTO tape, the number is five. The area sandwiched between two adjacent servo bands is the data band. The data band is composed of a plurality of data tracks, and each data track corresponds to each servo track.
 また、一形態では、特開2004-318983号公報に示されているように、各サーボバンドには、サーボバンドの番号を示す情報(「サーボバンドID(identification)」または「UDIM(Unique DataBand Identification Method)情報」とも呼ばれる。)が埋め込まれている。このサーボバンドIDは、サーボバンド中に複数ある一対のサーボストライプのうちの特定のものを、その位置が磁気テープの長手方向に相対的に変位するように、ずらすことによって記録されている。具体的には、複数ある一対のサーボストライプのうちの特定のもののずらし方を、サーボバンド毎に変えている。これにより、記録されたサーボバンドIDはサーボバンド毎にユニークなものとなるため、一つのサーボバンドをサーボ信号読み取り素子で読み取るだけで、そのサーボバンドを一意に(uniquely)特定することができる。 Further, in one form, as shown in Japanese Patent Application Laid-Open No. 2004-318983, each servo band has information indicating a servo band number (“servo band ID (identification)” or “UDIM (Unique DataBand Identification)”. It is also called "Servo) information".) Is embedded. The servo band ID is recorded by shifting a specific pair of servo stripes in the servo band so that their positions are relatively displaced in the longitudinal direction of the magnetic tape. Specifically, the method of shifting a specific pair of servo stripes is changed for each servo band. As a result, the recorded servo band ID becomes unique for each servo band, so that the servo band can be uniquely identified by simply reading one servo band with the servo signal reading element.
 尚、サーボバンドを一意に特定する方法には、ECMA―319(June 2001)に示されているようなスタッガード方式を用いたものもある。このスタッガード方式では、磁気テープの長手方向に連続的に複数配置された、互いに非平行な一対の磁気ストライプ(サーボストライプ)の群を、サーボバンド毎に磁気テープの長手方向にずらすように記録する。隣接するサーボバンド間における、このずらし方の組み合わせは、磁気テープ全体においてユニークなものとされているため、2つのサーボ信号読み取り素子によりサーボパターンを読み取る際に、サーボバンドを一意に特定することも可能となっている。 As a method for uniquely specifying the servo band, there is also a method using a staggered method as shown in ECMA-319 (June 2001). In this staggered method, a group of a pair of magnetic stripes (servo stripes) that are continuously arranged in the longitudinal direction of the magnetic tape and are non-parallel to each other are recorded so as to be shifted in the longitudinal direction of the magnetic tape for each servo band. do. Since this combination of shifting methods between adjacent servo bands is unique in the entire magnetic tape, it is possible to uniquely identify the servo band when reading the servo pattern by the two servo signal reading elements. It is possible.
 また、各サーボバンドには、ECMA―319(June 2001)に示されている通り、通常、磁気テープの長手方向の位置を示す情報(「LPOS(Longitudinal Position)情報」とも呼ばれる。)も埋め込まれている。このLPOS情報も、UDIM情報と同様に、一対のサーボストライプの位置を、磁気テープの長手方向にずらすことによって記録されている。ただし、UDIM情報とは異なり、このLPOS情報では、各サーボバンドに同じ信号が記録されている。 Further, as shown in ECMA-319 (June 2001), information indicating the position of the magnetic tape in the longitudinal direction (also referred to as "LPOS (Longitorial Position) information") is usually embedded in each servo band. ing. This LPOS information, like the UDIM information, is also recorded by shifting the position of the pair of servo stripes in the longitudinal direction of the magnetic tape. However, unlike the UDIM information, in this LPOS information, the same signal is recorded in each servo band.
 上記のUDIM情報およびLPOS情報とは異なる他の情報を、サーボバンドに埋め込むことも可能である。この場合、埋め込まれる情報は、UDIM情報のようにサーボバンド毎に異なるものであってもよいし、LPOS情報のようにすべてのサーボバンドに共通のものであってもよい。
 また、サーボバンドに情報を埋め込む方法としては、上記以外の方法を採用することも可能である。例えば、一対のサーボストライプの群の中から、所定の対を間引くことによって、所定のコードを記録するようにしてもよい。
It is also possible to embed other information different from the above UDIM information and LPOS information in the servo band. In this case, the embedded information may be different for each servo band such as UDIM information, or may be common to all servo bands such as LPOS information.
Further, as a method of embedding information in the servo band, a method other than the above can be adopted. For example, a predetermined code may be recorded by thinning out a predetermined pair from a group of a pair of servo stripes.
 サーボパターン形成用ヘッドは、サーボライトヘッドと呼ばれる。サーボライトヘッドは、通常、上記一対の磁気ストライプに対応した一対のギャップを、サーボバンドの数だけ有する。通常、各一対のギャップには、それぞれコアとコイルが接続されており、コイルに電流パルスを供給することによって、コアに発生した磁界が、一対のギャップに漏れ磁界を生じさせることができる。サーボパターンの形成の際には、サーボライトヘッド上に磁気テープを走行させながら電流パルスを入力することによって、一対のギャップに対応した磁気パターンを磁気テープに転写させて、サーボパターンを形成することができる。各ギャップの幅は、形成されるサーボパターンの密度に応じて適宜設定することができる。各ギャップの幅は、例えば、1μm以下、1~10μm、10μm以上等に設定可能である。 The servo pattern forming head is called a servo light head. The servo light head usually has a pair of gaps corresponding to the pair of magnetic stripes as many as the number of servo bands. Normally, a core and a coil are connected to each pair of gaps, and by supplying a current pulse to the coil, a magnetic field generated in the core can generate a leakage magnetic field in the pair of gaps. When forming a servo pattern, the magnetic pattern corresponding to a pair of gaps is transferred to the magnetic tape by inputting a current pulse while running the magnetic tape on the servo light head to form the servo pattern. Can be done. The width of each gap can be appropriately set according to the density of the formed servo pattern. The width of each gap can be set to, for example, 1 μm or less, 1 to 10 μm, 10 μm or more, and the like.
 磁気テープにサーボパターンを形成する前には、磁気テープに対して、通常、消磁(イレース)処理が施される。このイレース処理は、直流磁石または交流磁石を用いて、磁気テープに一様な磁界を加えることによって行うことができる。イレース処理には、DC(Direct Current)イレースとAC(Alternating Current)イレースとがある。ACイレースは、磁気テープに印加する磁界の方向を反転させながら、その磁界の強度を徐々に下げることによって行われる。一方、DCイレースは、磁気テープに一方向の磁界を加えることによって行われる。DCイレースには、更に2つの方法がある。第一の方法は、磁気テープの長手方向に沿って一方向の磁界を加える、水平DCイレースである。第二の方法は、磁気テープの厚み方向に沿って一方向の磁界を加える、垂直DCイレースである。イレース処理は、磁気テープ全体に対して行ってもよいし、磁気テープのサーボバンド毎に行ってもよい。 Before forming a servo pattern on a magnetic tape, the magnetic tape is usually demagnetized (erase). This erasing process can be performed by applying a uniform magnetic field to the magnetic tape using a DC magnet or an AC magnet. The erase processing includes DC (Direct Current) erase and AC (Alternating Current) erase. AC erase is performed by gradually reducing the strength of the magnetic field while reversing the direction of the magnetic field applied to the magnetic tape. On the other hand, DC erase is performed by applying a unidirectional magnetic field to the magnetic tape. There are two more methods for DC erase. The first method is horizontal DC erase, which applies a unidirectional magnetic field along the longitudinal direction of the magnetic tape. The second method is vertical DC erase, which applies a unidirectional magnetic field along the thickness direction of the magnetic tape. The erasing process may be performed on the entire magnetic tape or may be performed on each servo band of the magnetic tape.
 形成されるサーボパターンの磁界の向きは、イレースの向きに応じて決まる。例えば、磁気テープに水平DCイレースが施されている場合、サーボパターンの形成は、磁界の向きがイレースの向きと反対になるように行われる。これにより、サーボパターンが読み取られて得られるサーボ信号の出力を、大きくすることができる。尚、特開2012-53940号公報に示されている通り、垂直DCイレースされた磁気テープに、上記ギャップを用いた磁気パターンの転写を行った場合、形成されたサーボパターンが読み取られて得られるサーボ信号は、単極パルス形状となる。一方、水平DCイレースされた磁気テープに、上記ギャップを用いた磁気パターンの転写を行った場合、形成されたサーボパターンが読み取られて得られるサーボ信号は、双極パルス形状となる。 The direction of the magnetic field of the formed servo pattern is determined by the direction of erase. For example, when the magnetic tape is subjected to horizontal DC erase, the servo pattern is formed so that the direction of the magnetic field is opposite to the direction of the erase. As a result, the output of the servo signal obtained by reading the servo pattern can be increased. As shown in Japanese Patent Application Laid-Open No. 2012-53940, when a magnetic pattern using the above gap is transferred to a vertically DC-erased magnetic tape, the formed servo pattern is read and obtained. The servo signal has a unipolar pulse shape. On the other hand, when the magnetic pattern is transferred to the horizontally DC-erased magnetic tape using the gap, the servo signal obtained by reading the formed servo pattern has a bipolar pulse shape.
 また、一形態では、サーボ信号を利用して走行中の磁気テープの幅方向の寸法情報を取得し、取得された寸法情報に応じて磁気テープの長手方向にかかるテンションを調整して変化させることによって、磁気テープの幅方向の寸法を制御することができる。このようなテンション調整を行うことは、記録または再生時、磁気テープの幅変形によってデータを記録または再生するための磁気ヘッドが狙いのトラック位置からずれてデータの記録または再生を行ってしまうことを抑制することに寄与し得る。 Further, in one form, dimensional information in the width direction of the traveling magnetic tape is acquired by using a servo signal, and the tension applied in the longitudinal direction of the magnetic tape is adjusted and changed according to the acquired dimensional information. Allows you to control the widthwise dimensions of the magnetic tape. Performing such tension adjustment prevents the magnetic head for recording or reproducing data from being displaced from the target track position during recording or reproduction due to the width deformation of the magnetic tape, and recording or reproducing the data. Can contribute to suppression.
[磁気テープカートリッジ]
 上記磁気記録媒体は、一形態では、磁気テープであることができる。本発明の一態様は、上記磁気テープを含む磁気テープカートリッジに関する。
[Magnetic tape cartridge]
In one form, the magnetic recording medium can be a magnetic tape. One aspect of the present invention relates to a magnetic tape cartridge containing the magnetic tape.
 上記テープカートリッジに含まれる磁気テープの詳細は、先に記載した通りである。 The details of the magnetic tape included in the above tape cartridge are as described above.
 磁気テープカートリッジでは、一般に、カートリッジ本体内部に磁気テープがリールに巻き取られた状態で収容されている。リールは、カートリッジ本体内部に回転可能に備えられている。磁気テープカートリッジとしては、カートリッジ本体内部にリールを1つ具備する単リール型の磁気テープカートリッジおよびカートリッジ本体内部にリールを2つ具備する双リール型の磁気テープカートリッジが広く用いられている。単リール型の磁気テープカートリッジは、磁気テープへのデータの記録および/または再生のために磁気テープ装置に装着されると、磁気テープカートリッジから磁気テープが引き出されて磁気テープ装置側のリールに巻き取られる。磁気テープカートリッジから巻き取りリールまでの磁気テープ搬送経路には、磁気ヘッドが配置されている。磁気テープカートリッジ側のリール(供給リール)と磁気テープ装置側のリール(巻き取りリール)との間で、磁気テープの送り出しと巻き取りが行われる。この間、磁気ヘッドと磁気テープの磁性層表面とが接触し摺動することにより、データの記録および/または再生が行われる。これに対し、双リール型の磁気テープカートリッジは、供給リールと巻き取りリールの両リールが、磁気テープカートリッジ内部に具備されている。 In a magnetic tape cartridge, the magnetic tape is generally housed inside the cartridge body in a state of being wound on a reel. The reel is rotatably provided inside the cartridge body. As the magnetic tape cartridge, a single reel type magnetic tape cartridge having one reel inside the cartridge main body and a twin reel type magnetic tape cartridge having two reels inside the cartridge main body are widely used. When the single reel type magnetic tape cartridge is attached to the magnetic tape device for recording and / or playing back data on the magnetic tape, the magnetic tape is pulled out from the magnetic tape cartridge and wound on the reel on the magnetic tape device side. Taken. A magnetic head is arranged in the magnetic tape transport path from the magnetic tape cartridge to the take-up reel. The magnetic tape is sent out and wound between the reel (supply reel) on the magnetic tape cartridge side and the reel (winding reel) on the magnetic tape device side. During this time, the magnetic head and the surface of the magnetic layer of the magnetic tape come into contact with each other and slide, so that data can be recorded and / or reproduced. On the other hand, in the twin reel type magnetic tape cartridge, both the supply reel and the take-up reel are provided inside the magnetic tape cartridge.
[磁気記録再生装置]
 本発明の一態様は、磁気記録媒体を含む磁気記録再生装置に関する。一形態では、上記磁気記録再生装置において、磁気記録媒体へのデータの記録および/または磁気記録媒体に記録されたデータの再生は、磁気記録媒体の磁性層表面と磁気ヘッドとを接触させて摺動させることにより行うことができる。かかる形態の磁気記録再生装置は、一般に摺動型ドライブまたは接触摺動型ドライブと呼ばれる。他の一形態では、磁気ヘッドは、磁性層表面とは、不作為に接触する場合を除き、非接触の状態で、磁気記録媒体へのデータの記録および/または磁気記録媒体に記録されたデータの再生を行う。かかる形態の磁気記録再生装置は、一般に浮上型ドライブと呼ばれる。例えば、磁気記録媒体が磁気テープである形態において、上記磁気記録再生装置は、一形態では摺動型ドライブであることができ、他の一形態では浮上型ドライブであることができる。
[Magnetic recording / playback device]
One aspect of the present invention relates to a magnetic recording / reproducing device including a magnetic recording medium. In one embodiment, in the magnetic recording / reproducing device, the recording of data on the magnetic recording medium and / or the reproduction of the data recorded on the magnetic recording medium are performed by bringing the surface of the magnetic layer of the magnetic recording medium into contact with the magnetic head. It can be done by moving it. Such a form of magnetic recording / reproduction device is generally called a sliding drive or a contact sliding drive. In another embodiment, the magnetic head records data on a magnetic recording medium and / or data recorded on a magnetic recording medium in a non-contact state, except in the case of random contact with the surface of the magnetic layer. Play back. Such a form of magnetic recording / reproduction device is generally called a levitation type drive. For example, in a form in which the magnetic recording medium is a magnetic tape, the magnetic recording / reproducing device can be a sliding drive in one form and a floating drive in another form.
 本発明および本明細書において、「磁気記録再生装置」とは、磁気記録媒体へのデータの記録および磁気記録媒体に記録されたデータの再生の少なくとも一方を行うことができる装置を意味するものとする。かかる装置は、一般にドライブと呼ばれる。上記磁気記録再生装置に含まれる磁気ヘッドは、磁気記録媒体へのデータの記録を行うことができる記録ヘッドであることができ、磁気記録媒体に記録されたデータの再生を行うことができる再生ヘッドであることもできる。また、上記磁気記録再生装置は、一形態では、別々の磁気ヘッドとして、記録ヘッドと再生ヘッドの両方を含むことができる。他の一形態では、上記磁気テープ装置に含まれる磁気ヘッドは、記録素子と再生素子の両方を1つの磁気ヘッドに備えた構成を有することもできる。再生ヘッドとしては、磁気記録媒体に記録された情報を感度よく読み取ることができる磁気抵抗効果型(MR;Magnetoresistive)素子を再生素子として含む磁気ヘッド(MRヘッド)が好ましい。MRヘッドとしては、公知の各種MRヘッド(例えば、GMR(Giant Magnetoresistive)ヘッド、TMR(Tunnel Magnetoresistive)ヘッド等)を用いることができる。また、データの記録および/またはデータの再生を行う磁気ヘッドには、サーボ信号読み取り素子が含まれていてもよい。または、データの記録および/またはデータの再生を行う磁気ヘッドとは別のヘッドとして、サーボ信号読み取り素子を備えた磁気ヘッド(サーボヘッド)が上記磁気テープ装置に含まれていてもよい。例えば、データの記録および/または記録されたデータの再生を行う磁気ヘッド(以下、「記録再生ヘッド」とも呼ぶ。)は、サーボ信号読み取り素子を2つ含むことができ、2つのサーボ信号読み取り素子のそれぞれが、データバンドを挟んで隣り合う2本のサーボバンドを同時に読み取ることができる。2つのサーボ信号読み取り素子の間に、1つまたは複数のデータ用素子を配置することができる。データの記録のための素子(記録素子)とデータの再生のための素子(再生素子)を、「データ用素子」と総称する。 In the present invention and the present specification, the "magnetic recording / reproduction device" means an apparatus capable of recording data on a magnetic recording medium and reproducing data recorded on the magnetic recording medium. do. Such a device is commonly referred to as a drive. The magnetic head included in the magnetic recording / reproducing device can be a recording head capable of recording data on a magnetic recording medium, and can reproduce data recorded on the magnetic recording medium. Can also be. Further, in one form, the magnetic recording / reproducing device may include both a recording head and a reproducing head as separate magnetic heads. In another embodiment, the magnetic head included in the magnetic tape device may have a configuration in which both a recording element and a reproducing element are provided in one magnetic head. As the reproduction head, a magnetic head (MR head) including a magnetoresistive (MR; Magnetoresistive) element capable of reading information recorded on a magnetic recording medium with high sensitivity is preferable. As the MR head, various known MR heads (for example, GMR (Giant Magnetoresistive) head, TMR (Tunnel Magnetorestive) head, etc.) can be used. Further, the magnetic head that records data and / or reproduces data may include a servo signal reading element. Alternatively, the magnetic tape device may include a magnetic head (servohead) provided with a servo signal reading element as a head separate from the magnetic head that records and / or reproduces data. For example, a magnetic head that records data and / or reproduces recorded data (hereinafter, also referred to as “recording / reproducing head”) can include two servo signal reading elements, and two servo signal reading elements. Each of the two servo bands adjacent to each other with the data band in between can be read at the same time. One or more data elements can be arranged between the two servo signal reading elements. Elements for recording data (recording elements) and elements for reproducing data (reproduction elements) are collectively referred to as "data elements".
 データの記録および/または記録されたデータの再生の際には、まず、サーボ信号を用いたトラッキングを行うことができる。即ち、サーボ信号読み取り素子を所定のサーボトラックに追従させることによって、データ用素子が、目的とするデータトラック上を通過するように制御することができる。データトラックの移動は、サーボ信号読み取り素子が読み取るサーボトラックを、テープ幅方向に変更することにより行われる。
 また、記録再生ヘッドは、他のデータバンドに対する記録および/または再生を行うことも可能である。その際には、先に記載したUDIM情報を利用してサーボ信号読み取り素子を所定のサーボバンドに移動させ、そのサーボバンドに対するトラッキングを開始すればよい。
When recording data and / or reproducing recorded data, tracking using a servo signal can be performed first. That is, by making the servo signal reading element follow a predetermined servo track, the data element can be controlled to pass on the target data track. The movement of the data track is performed by changing the servo track read by the servo signal reading element in the tape width direction.
The recording / playback head can also record and / or play back to other data bands. In that case, the servo signal reading element may be moved to a predetermined servo band by using the UDIM information described above, and tracking for the servo band may be started.
 図1に、データバンドおよびサーボバンドの配置例を示す。図1中、磁気テープMTの磁性層には、複数のサーボバンド1が、ガイドバンド3に挟まれて配置されている。2本のサーボバンドに挟まれた複数の領域2が、データバンドである。サーボパターンは、磁化領域であって、サーボライトヘッドにより磁性層の特定の領域を磁化することによって形成される。サーボライトヘッドにより磁化する領域(サーボパターンを形成する位置)は規格により定められている。例えば業界標準規格であるLTO Ultriumフォーマットテープには、磁気テープ製造時に、図2に示すようにテープ幅方向に対して傾斜した複数のサーボパターンが、サーボバンド上に形成される。詳しくは、図2中、サーボバンド1上のサーボフレームSFは、サーボサブフレーム1(SSF1)およびサーボサブフレーム2(SSF2)から構成される。サーボサブフレーム1は、Aバースト(図2中、符号A)およびBバースト(図2中、符号B)から構成される。AバーストはサーボパターンA1~A5から構成され、BバーストはサーボパターンB1~B5から構成される。一方、サーボサブフレーム2は、Cバースト(図2中、符号C)およびDバースト(図2中、符号D)から構成される。CバーストはサーボパターンC1~C4から構成され、DバーストはサーボパターンD1~D4から構成される。このような18本のサーボパターンが5本と4本のセットで、5、5、4、4、の配列で並べられたサブフレームに配置され、サーボフレームを識別するために用いられる。図2には、説明のために1つのサーボフレームを示した。ただし、実際には、タイミングベースサーボ方式のヘッドトラッキングが行われる磁気テープの磁性層には、各サーボバンドに、複数のサーボフレームが走行方向に配置されている。図2中、矢印は走行方向を示している。例えば、LTO Ultriumフォーマットテープは、通常、磁性層の各サーボバンドに、テープ長1mあたり5000以上のサーボフレームを有する。 FIG. 1 shows an example of arrangement of a data band and a servo band. In FIG. 1, a plurality of servo bands 1 are arranged on the magnetic layer of the magnetic tape MT so as to be sandwiched between the guide bands 3. A plurality of regions 2 sandwiched between the two servo bands are data bands. The servo pattern is a magnetization region, which is formed by magnetizing a specific region of the magnetic layer with a servo light head. The region magnetized by the servo light head (the position where the servo pattern is formed) is defined by the standard. For example, in the LTO Ultra format tape, which is an industry standard, a plurality of servo patterns inclined with respect to the tape width direction are formed on the servo band at the time of manufacturing a magnetic tape. Specifically, in FIG. 2, the servo frame SF on the servo band 1 is composed of the servo subframe 1 (SSF1) and the servo subframe 2 (SSF2). The servo subframe 1 is composed of an A burst (reference numeral A in FIG. 2) and a B burst (reference numeral B in FIG. 2). The A burst is composed of servo patterns A1 to A5, and the B burst is composed of servo patterns B1 to B5. On the other hand, the servo subframe 2 is composed of a C burst (reference numeral C in FIG. 2) and a D burst (reference numeral D in FIG. 2). The C burst is composed of servo patterns C1 to C4, and the D burst is composed of servo patterns D1 to D4. Such 18 servo patterns are arranged in a set of 5 and 4 in a subframe arranged in an array of 5, 5, 4, 4, and used to identify the servo frame. FIG. 2 shows one servo frame for illustration. However, in reality, a plurality of servo frames are arranged in the traveling direction in each servo band on the magnetic layer of the magnetic tape on which the head tracking of the timing-based servo method is performed. In FIG. 2, the arrow indicates the traveling direction. For example, an LTO Ultra format tape usually has a servo frame of 5000 or more per 1 m of tape length in each servo band of the magnetic layer.
 上記磁気記録再生装置において、一形態では、磁気記録媒体は取り外し可能な媒体(いわゆる可換媒体)として扱われ、例えば、磁気テープを収容した磁気テープカートリッジが磁気記録再生装置に挿入され、取り出される。他の一形態では、磁気記録媒体は可換媒体として扱われず、例えば、磁気ヘッドを備えた磁気記録再生装置のリールに磁気テープが巻き取られ、磁気記録再生装置内に磁気テープが収容される。 In the above magnetic recording / playback device, in one form, the magnetic recording medium is treated as a removable medium (so-called replaceable medium), and for example, a magnetic tape cartridge containing a magnetic tape is inserted into the magnetic recording / playback device and taken out. .. In another embodiment, the magnetic recording medium is not treated as a convertible medium, for example, the magnetic tape is wound around a reel of a magnetic recording / playback device provided with a magnetic head, and the magnetic tape is housed in the magnetic recording / playback device. ..
 以下に、本発明の一態様を実施例に基づき説明する。但し、本発明は実施例に示す実施形態に限定されるものではない。以下に記載の「部」、「%」の表示は、特に断らない限り、「質量部」、「質量%」を示す。「eq」は、当量(equivalent)であり、SI単位に換算不可の単位である。
 また、以下の各種工程および操作は、特記しない限り、温度20~25℃および相対湿度40~60%の環境において行った。
Hereinafter, one aspect of the present invention will be described based on examples. However, the present invention is not limited to the embodiments shown in the examples. The indications of "part" and "%" described below indicate "parts by mass" and "% by mass" unless otherwise specified. “Eq” is an equivalent and is a unit that cannot be converted into SI units.
Unless otherwise specified, the following various steps and operations were performed in an environment with a temperature of 20 to 25 ° C. and a relative humidity of 40 to 60%.
 後述の表1中、「メタル」と記載されている強磁性粉末としては、先に示した特許文献1(特開2004-103137号公報)の実施例1で使用されている強磁性粉末に類するものとして、鉄-コバルト合金系強磁性粉末を使用した。 The ferromagnetic powder described as "metal" in Table 1 described later is similar to the ferromagnetic powder used in Example 1 of Patent Document 1 (Japanese Unexamined Patent Publication No. 2004-103137) shown above. As a material, an iron-cobalt alloy-based ferromagnetic powder was used.
 後述の表1中、「BaFe」は平均粒子サイズ(平均板径)21nmの六方晶バリウムフェライト粉末を示す。 In Table 1 below, "BaFe" indicates a hexagonal barium ferrite powder having an average particle size (average plate diameter) of 21 nm.
 後述の表1中、「SrFe」は以下に記載の方法によって作製された六方晶ストロンチウムフェライト粉末を示し、「ε-酸化鉄」は以下に記載の方法によって作製されたε-酸化鉄粉末を示す。
 以下に記載の各種強磁性粉末の平均粒子体積は、先に記載の方法により求められた値である。以下に記載の各種粉末の粒子のサイズに関する各種値も先に記載の方法により求められた値である。
 異方性定数Kuは、各強磁性粉末について振動試料型磁力計(東英工業社製)を用いて先に記載の方法により求められた値である。
 また、質量磁化σsは、振動試料型磁力計(東英工業社製)を用いて磁場強度15kOeで測定された値である。
In Table 1 below, "SrFe" indicates a hexagonal strontium ferrite powder prepared by the method described below, and "ε-iron oxide" indicates an ε-iron oxide powder prepared by the method described below. ..
The average particle volume of the various ferromagnetic powders described below is a value obtained by the method described above. The various values related to the particle size of the various powders described below are also the values obtained by the method described above.
The anisotropy constant Ku is a value obtained for each ferromagnetic powder by the method described above using a vibration sample magnetometer (manufactured by Toei Kogyo Co., Ltd.).
The mass magnetization σs is a value measured at a magnetic field strength of 15 kOe using a vibration sample magnetometer (manufactured by Toei Kogyo Co., Ltd.).
[強磁性粉末の作製方法]
<六方晶ストロンチウムフェライト粉末の作製方法>
 SrCOを1707g、HBOを687g、Feを1120g、Al(OH)を45g、BaCOを24g、CaCOを13g、およびNdを235g秤量し、ミキサーにて混合し原料混合物を得た。
 得られた原料混合物を、白金ルツボで溶融温度1390℃で溶融し、融液を撹拌しつつ白金ルツボの底に設けた出湯口を加熱し、融液を約6g/秒で棒状に出湯させた。出湯液を水冷双ローラーで圧延急冷して非晶質体を作製した。
 作製した非晶質体280gを電気炉に仕込み、昇温速度3.5℃/分にて635℃(結晶化温度)まで昇温し、同温度で5時間保持して六方晶ストロンチウムフェライト粒子を析出(結晶化)させた。
 次いで六方晶ストロンチウムフェライト粒子を含む上記で得られた結晶化物を乳鉢で粗粉砕し、ガラス瓶に粒径1mmのジルコニアビーズ1000gと濃度1%の酢酸水溶液を800ml加えてペイントシェーカーにて3時間分散処理を行った。その後、得られた分散液をビーズと分離させステンレスビーカーに入れた。分散液を液温100℃で3時間静置させてガラス成分の溶解処理を行った後、遠心分離器で沈澱させてデカンテーションを繰り返して洗浄し、炉内温度110℃の加熱炉内で6時間乾燥させて六方晶ストロンチウムフェライト粉末を得た。
 上記で得られた六方晶ストロンチウムフェライト粉末(後述の表1中、「SrFe」)の平均粒子体積は900nm、異方性定数Kuは2.2×10J/m、質量磁化σsは49A・m/kgであった。
 上記で得られた六方晶ストロンチウムフェライト粉末から試料粉末を12mg採取し、この試料粉末を先に例示した溶解条件によって部分溶解して得られたろ液の元素分析をICP分析装置によって行い、ネオジム原子の表層部含有率を求めた。
 別途、上記で得られた六方晶ストロンチウムフェライト粉末から試料粉末を12mg採取し、この試料粉末を先に例示した溶解条件によって全溶解して得られたろ液の元素分析をICP分析装置によって行い、ネオジム原子のバルク含有率を求めた。
 上記で得られた六方晶ストロンチウムフェライト粉末の鉄原子100原子%に対するネオジム原子の含有率(バルク含有率)は、2.9原子%であった。また、ネオジム原子の表層部含有率は8.0原子%であった。表層部含有率とバルク含有率との比率、「表層部含有率/バルク含有率」は2.8であり、ネオジム原子が粒子の表層に偏在していることが確認された。
[Method for producing ferromagnetic powder]
<Method for producing hexagonal strontium ferrite powder>
Weigh 1707 g of SrCO 3 , 687 g of H 3 BO 3 , 1120 g of Fe 2 O 3 , 45 g of Al (OH) 3 , 24 g of BaCO 3 , 13 g of CaCO 3 , and 235 g of Nd 2 O 3 with a mixer. The mixture was mixed to obtain a raw material mixture.
The obtained raw material mixture was melted in a platinum crucible at a melting temperature of 1390 ° C., and the hot water outlet provided at the bottom of the platinum crucible was heated while stirring the melt, so that the melt was discharged into a rod shape at about 6 g / sec. .. The hot water was rolled and rapidly cooled with a water-cooled twin roller to prepare an amorphous body.
280 g of the prepared amorphous body was charged into an electric furnace, the temperature was raised to 635 ° C (crystallization temperature) at a heating rate of 3.5 ° C / min, and the temperature was maintained at the same temperature for 5 hours to obtain hexagonal strontium ferrite particles. It was precipitated (crystallized).
Next, the crystallized product obtained above containing hexagonal strontium ferrite particles was coarsely pulverized in a mortar, 1000 g of zirconia beads having a particle size of 1 mm and 800 ml of an aqueous acetic acid solution having a concentration of 1% were added to a glass bottle, and dispersion treatment was performed for 3 hours with a paint shaker. Was done. Then, the obtained dispersion was separated from the beads and placed in a stainless steel beaker. The dispersion is allowed to stand at a liquid temperature of 100 ° C. for 3 hours to dissolve the glass components, then settled in a centrifuge and decanted repeatedly for cleaning. It was dried for a time to obtain a hexagonal strontium ferrite powder.
The hexagonal strontium ferrite powder (“SrFe” in Table 1 below) obtained above has an average particle volume of 900 nm 3 , anisotropy constant Ku of 2.2 × 105 J / m 3 , and mass magnetization σs. It was 49 A · m 2 / kg.
12 mg of a sample powder was collected from the hexagonal strontium ferrite powder obtained above, and the sample powder was partially dissolved under the dissolution conditions exemplified above to perform elemental analysis of the filtrate obtained by using an ICP analyzer. The content of the surface layer was determined.
Separately, 12 mg of a sample powder was collected from the hexagonal strontium ferrite powder obtained above, and the sample powder was completely dissolved under the dissolution conditions exemplified above to perform elemental analysis of the filtrate obtained by using an ICP analyzer. The bulk content of the atoms was determined.
The content of neodymium atom (bulk content) with respect to 100 atomic% of iron atom of the hexagonal strontium ferrite powder obtained above was 2.9 atomic%. The content of the neodymium atom in the surface layer was 8.0 atom%. The ratio of the surface layer content to the bulk content, "surface layer content / bulk content" was 2.8, and it was confirmed that the neodymium atoms were unevenly distributed on the surface layer of the particles.
 上記で得られた粉末が六方晶フェライトの結晶構造を示すことは、CuKα線を電圧45kVかつ強度40mAの条件で走査し、下記条件でX線回折パターンを測定すること(X線回折分析)により確認した。上記で得られた粉末は、マグネトプランバイト型(M型)の六方晶フェライトの結晶構造を示した。また、X線回折分析により検出された結晶相は、マグネトプランバイト型の単一相であった。
 PANalytical X’Pert Pro回折計、PIXcel検出器
 入射ビームおよび回折ビームのSollerスリット:0.017ラジアン
 分散スリットの固定角:1/4度
 マスク:10mm
 散乱防止スリット:1/4度
 測定モード:連続
 1段階あたりの測定時間:3秒
 測定速度:毎秒0.017度
 測定ステップ:0.05度
To show the crystal structure of hexagonal ferrite in the powder obtained above, CuKα rays are scanned under the conditions of a voltage of 45 kV and an intensity of 40 mA, and the X-ray diffraction pattern is measured under the following conditions (X-ray diffraction analysis). confirmed. The powder obtained above showed a crystal structure of a magnetoplumbite type (M type) hexagonal ferrite. Moreover, the crystal phase detected by the X-ray diffraction analysis was a single phase of the magnetoplumbite type.
PANalitic X'Pert Pro Diffractometer, PIXcel Detector Soller slit of incident beam and diffracted beam: 0.017 Fixed angle of radian dispersion slit: 1/4 degree Mask: 10 mm
Anti-scattering slit: 1/4 degree Measurement mode: Continuous Measurement time per step: 3 seconds Measurement speed: 0.017 degrees per second Measurement step: 0.05 degrees
<ε-酸化鉄粉末の作製方法>
 純水90gに、硝酸鉄(III)9水和物8.3g、硝酸ガリウム(III)8水和物1.3g、硝酸コバルト(II)6水和物190mg、硫酸チタン(IV)150mg、およびポリビニルピロリドン(PVP)1.5gを溶解させたものを、マグネチックスターラーを用いて撹拌しながら、大気雰囲気中、雰囲気温度25℃の条件下で、濃度25%のアンモニア水溶液4.0gを添加し、雰囲気温度25℃の温度条件のまま2時間撹拌した。得られた溶液に、クエン酸1gを純水9gに溶解させて得たクエン酸溶液を加え、1時間撹拌した。撹拌後に沈殿した粉末を遠心分離によって採集し、純水で洗浄し、炉内温度80℃の加熱炉内で乾燥させた。
 乾燥させた粉末に純水800gを加えて再度粉末を水に分散させて分散液を得た。得られた分散液を液温50℃に昇温し、撹拌しながら濃度25%アンモニア水溶液を40g滴下した。50℃の温度を保ったまま1時間撹拌した後、テトラエトキシシラン(TEOS)14mLを滴下し、24時間撹拌した。得られた反応溶液に、硫酸アンモニウム50gを加え、沈殿した粉末を遠心分離によって採集し、純水で洗浄し、炉内温度80℃の加熱炉内で24時間乾燥させ、強磁性粉末の前駆体を得た。
 得られた強磁性粉末の前駆体を、大気雰囲気下、炉内温度1000℃の加熱炉内に装填し、4時間の熱処理を施した。
 熱処理した強磁性粉末の前駆体を、4mol/Lの水酸化ナトリウム(NaOH)水溶液中に投入し、液温を70℃に維持して24時間撹拌することにより、熱処理した強磁性粉末の前駆体から不純物であるケイ酸化合物を除去した。
 その後、遠心分離処理により、ケイ酸化合物を除去した強磁性粉末を採集し、純水で洗浄を行い、強磁性粉末を得た。
 得られた強磁性粉末の組成を高周波誘導結合プラズマ発光分光分析(ICP-OES;Inductively Coupled Plasma-Optical Emission Spectrometry)により確認したところ、Ga、CoおよびTi置換型ε-酸化鉄(ε-Ga0.28Co0.05Ti0.05Fe1.62)であった。また、先に六方晶ストロンチウムフェライト粉末の作製方法について記載した条件と同様の条件でX線回折分析を行い、X線回折パターンのピークから、得られた強磁性粉末が、α相およびγ相の結晶構造を含まない、ε相の単相の結晶構造(ε-酸化鉄型の結晶構造)を有することを確認した。
 得られたε-酸化鉄粉末(後述の表1中、「ε-酸化鉄」)の平均粒子体積は750nm、異方性定数Kuは1.2×10J/m、質量磁化σsは16A・m/kgであった。
<Method of producing ε-iron oxide powder>
In 90 g of pure water, 8.3 g of iron (III) nitrate 9 hydrate, 1.3 g of gallium nitrate (III) octahydrate, 190 mg of cobalt (II) nitrate hexahydrate, 150 mg of titanium (IV) sulfate, and While stirring 1.5 g of polyvinylpyrrolidone (PVP) dissolved in it using a magnetic stirrer, 4.0 g of an aqueous ammonia solution having a concentration of 25% was added in an atmospheric atmosphere under the condition of an atmospheric temperature of 25 ° C. The mixture was stirred for 2 hours under the temperature condition of 25 ° C. To the obtained solution, a citric acid solution obtained by dissolving 1 g of citric acid in 9 g of pure water was added, and the mixture was stirred for 1 hour. The powder precipitated after stirring was collected by centrifugation, washed with pure water, and dried in a heating furnace having a furnace temperature of 80 ° C.
800 g of pure water was added to the dried powder, and the powder was dispersed in water again to obtain a dispersion liquid. The temperature of the obtained dispersion was raised to 50 ° C., and 40 g of a 25% aqueous ammonia solution was added dropwise with stirring. After stirring for 1 hour while maintaining the temperature of 50 ° C., 14 mL of tetraethoxysilane (TEOS) was added dropwise, and the mixture was stirred for 24 hours. 50 g of ammonium sulfate was added to the obtained reaction solution, and the precipitated powder was collected by centrifugation, washed with pure water, and dried in a heating furnace at a temperature of 80 ° C. for 24 hours to obtain a precursor of the ferromagnetic powder. Obtained.
The obtained precursor of the ferromagnetic powder was loaded into a heating furnace having a furnace temperature of 1000 ° C. under an atmospheric atmosphere, and heat-treated for 4 hours.
The precursor of the heat-treated ferromagnetic powder was put into a 4 mol / L aqueous solution of sodium hydroxide (NaOH), and the liquid temperature was maintained at 70 ° C. and stirred for 24 hours to prepare the precursor of the heat-treated ferromagnetic powder. The caustic compound, which is an impurity, was removed from the material.
Then, the ferromagnetic powder from which the silicic acid compound was removed was collected by centrifugation and washed with pure water to obtain a ferromagnetic powder.
The composition of the obtained ferromagnetic powder was confirmed by high frequency inductively coupled plasma emission spectroscopy (ICP-OES; Inductively Coupled Plasma-Optical Operation Spectroscopy) and found to be Ga, Co and Ti substituted ε-iron oxide (ε-Ga 0 ). It was .28 Co 0.05 Ti 0.05 Fe 1.62 O 3 ). Further, X-ray diffraction analysis was performed under the same conditions as those described above for the method for producing hexagonal strontium ferrite powder, and the ferromagnetic powder obtained from the peak of the X-ray diffraction pattern was of α phase and γ phase. It was confirmed that it had a ε-phase single-phase crystal structure (ε-iron oxide type crystal structure) that did not contain a crystal structure.
The average particle volume of the obtained ε-iron oxide powder (“ε-iron oxide” in Table 1 below) is 750 nm 3 , the anisotropic constant Ku is 1.2 × 105 J / m 3 , and the mass magnetization σs. Was 16 A · m 2 / kg.
[実施例1]
(1)アルミナ分散物の調製
 アルファ化率約65%、BET(Brunauer-Emmett-Teller)比表面積20m/gのアルミナ粉末(住友化学社製HIT-80)100.0部に対し、3.0部の2,3-ジヒドロキシナフタレン(東京化成社製)、極性基としてSONa基を有するポリエステルポリウレタン樹脂(東洋紡社製UR-4800(極性基量:80meq/kg))の32%溶液(溶媒はメチルエチルケトンとトルエンの混合溶媒)を31.3部、溶媒としてメチルエチルケトンとシクロヘキサノン1:1(質量比)の混合溶液570.0部を混合し、ジルコニアビーズ存在下で、ペイントシェーカーにより5時間分散させた。分散後、メッシュにより分散液とビーズとを分け、アルミナ分散物を得た。
[Example 1]
(1) Preparation of alumina dispersion 3. For 100.0 parts of alumina powder (HIT-80 manufactured by Sumitomo Chemical Co., Ltd.) having an pregelatinization rate of about 65% and a BET (Brunauer-Emmett-Teller) specific surface area of 20 m 2 / g. A 32% solution of 0 parts of 2,3-dihydroxynaphthalene (manufactured by Tokyo Kasei Co., Ltd.) and a polyester polyurethane resin having an SO 3 Na group as a polar group (UR-4800 manufactured by Toyo Boseki Co., Ltd. (polar group amount: 80 meq / kg)) ( 31.3 parts of a mixed solvent of methyl ethyl ketone and toluene) was mixed as a solvent, and 570.0 parts of a mixed solution of methyl ethyl ketone and cyclohexanone 1: 1 (mass ratio) was mixed as a solvent, and dispersed for 5 hours with a paint shaker in the presence of zirconia beads. I let you. After the dispersion, the dispersion liquid and the beads were separated by a mesh to obtain an alumina dispersion.
(2)磁性層形成用組成物処方
(磁性液)
強磁性粉末(種類:表1参照)              100.0部
SONa基含有ポリウレタン樹脂              14.0部
 重量平均分子量:70,000、SONa基:0.2meq/g
シクロヘキサノン                    150.0部
メチルエチルケトン                   150.0部
(研磨剤液)
上記(1)で調製したアルミナ分散物             6.0部
(突起形成剤液)
突起形成剤                         表1参照
 種類:コロイダルシリカ(平均粒子サイズ120nm)
メチルエチルケトン                     1.4部
(その他の成分)
ステアリン酸                        2.0部
ステアリン酸アミド                     0.2部
ブチルステアレート                     2.0部
ポリイソシアネート(東ソー社製コロネート(登録商標)L)  2.5部
(仕上げ添加溶媒)
シクロヘキサノン                    200.0部
メチルエチルケトン                   200.0部
(2) Formulation of composition for forming a magnetic layer (magnetic liquid)
Ferromagnetic powder (type: see Table 1) 100.0 parts SO 3 Na group-containing polyurethane resin 14.0 parts Weight average molecular weight: 70,000, SO 3 Na group: 0.2 meq / g
Cyclohexanone 150.0 parts Methyl ethyl ketone 150.0 parts (abrasive solution)
6.0 parts of alumina dispersion prepared in (1) above (projection forming agent solution)
Protrusion forming agent See Table 1 Type: Colloidal silica (average particle size 120 nm)
Methyl ethyl ketone 1.4 parts (other ingredients)
Stearic acid 2.0 parts Stearic acid amide 0.2 parts Butyl stearate 2.0 parts Polyisocyanate (Tosoh Coronate (registered trademark) L) 2.5 parts (finishing additive solvent)
Cyclohexanone 200.0 parts Methyl ethyl ketone 200.0 parts
(3)非磁性層形成用組成物処方
非磁性無機粉末:α-酸化鉄               100.0部
 平均粒子サイズ(平均長軸長):0.15μm
 針状比:7
 BET比表面積:52m/g
カーボンブラック                     20.0部
 平均粒子サイズ:20nm
SONa基含有ポリウレタン樹脂              18.0部
 重量平均分子量:70,000、SONa基:0.2meq/g
ステアリン酸                        2.0部
ステアリン酸アミド                     0.2部
ブチルステアレート                     2.0部
シクロヘキサノン                    300.0部
メチルエチルケトン                   300.0部
(3) Formulation of composition for forming a non-magnetic layer Non-magnetic inorganic powder: α-iron oxide 100.0 parts Average particle size (average major axis length): 0.15 μm
Needle ratio: 7
BET specific surface area: 52m 2 / g
Carbon black 20.0 parts Average particle size: 20nm
SO 3 Na group-containing polyurethane resin 18.0 parts Weight average molecular weight: 70,000, SO 3 Na group: 0.2 meq / g
Stearic acid 2.0 parts Stearic acid amide 0.2 parts Butyl stearate 2.0 parts Cyclohexanone 300.0 parts Methyl ethyl ketone 300.0 parts
(4)バックコート層形成用組成物処方
カーボンブラック                    100.0部
 DBP(Dibutyl phthalate)吸油量:74cm/100g
ニトロセルロース                     27.0部
スルホン酸基および/またはその塩を含有するポリエステルポリウレタン樹脂                            62.0部
ポリエステル樹脂                      4.0部
アルミナ粉末(BET比表面積:17m/g)         0.6部
メチルエチルケトン                   600.0部
トルエン                        600.0部
ポリイソシアネート(東ソー社製コロネート(登録商標)L) 15.0部
(4) Composition for backcoat layer formation Formulation Carbon black 100.0 parts DBP (Dibutyl phthalate) Oil absorption: 74 cm 3/100 g
27.0 parts of nitrocellulose Polyester polyurethane resin containing a sulfonic acid group and / or a salt thereof 62.0 parts Polyester resin 4.0 parts Alumina powder (BET specific surface area: 17 m 2 / g) 0.6 parts Methyl ethyl ketone 600.0 parts 600.0 parts Polyisocyanate (Coronate (registered trademark) L manufactured by Toso Co., Ltd.) 15.0 parts
(5)各層形成用組成物の調製
 磁性層形成用組成物を、以下の方法により調製した。上記磁性液を、各成分をバッチ式縦型サンドミルを用いて24時間分散(ビーズ分散)することにより調製した。分散ビーズとしては、ビーズ径0.5mmのジルコニアビーズを使用した。上記サンドミルを用いて、調製した磁性液および上記研磨剤液および他の成分(シリカゾル、その他の成分および仕上げ添加溶媒)と混合し5分間ビーズ分散した後、バッチ型超音波装置(20kHz、300W)で0.5分間処理(超音波分散)を行った。その後、0.5μmの孔径を有するフィルタを用いてろ過を行い磁性層形成用組成物を調製した。
 非磁性層形成用組成物を、以下の方法により調製した。潤滑剤(ステアリン酸、ステアリン酸アミドおよびブチルステアレート)を除く上記成分を、オープンニーダにより混練および希釈処理し、その後、横型ビーズミル分散機により分散処理を実施した。その後、潤滑剤(ステアリン酸、ステアリン酸アミドおよびブチルステアレート)を添加して、ディゾルバー撹拌機にて撹拌および混合処理を施して非磁性層形成用組成物を調製した。
 バックコート層形成用組成物を、以下の方法により調製した。ポリイソシアネートを除く上記成分を、ディゾルバー撹拌機に導入し、周速10m/秒で30分間撹拌した後、横型ビーズミル分散機により分散処理を実施した。その後、ポリイソシアネートを添加して、ディゾルバー撹拌機にて撹拌および混合処理を施し、バックコート層形成用組成物を調製した。
(5) Preparation of composition for forming each layer A composition for forming a magnetic layer was prepared by the following method. The above magnetic liquid was prepared by dispersing each component for 24 hours (bead dispersion) using a batch type vertical sand mill. As the dispersed beads, zirconia beads having a bead diameter of 0.5 mm were used. Using the above sand mill, the prepared magnetic solution, the above abrasive solution and other components (silica sol, other components and finish addition solvent) are mixed and bead-dispersed for 5 minutes, and then a batch type ultrasonic device (20 kHz, 300 W). The treatment (ultrasonic dispersion) was carried out for 0.5 minutes. Then, filtration was performed using a filter having a pore size of 0.5 μm to prepare a composition for forming a magnetic layer.
A composition for forming a non-magnetic layer was prepared by the following method. The above components excluding the lubricants (stearic acid, stearic acid amide and butyl stearate) were kneaded and diluted with an open kneader, and then dispersed with a horizontal bead mill disperser. Then, a lubricant (stearic acid, stearic acid amide and butyl stearate) was added, and the mixture was stirred and mixed with a dissolver stirrer to prepare a composition for forming a non-magnetic layer.
The composition for forming the back coat layer was prepared by the following method. The above components excluding polyisocyanate were introduced into a dissolver stirrer, stirred at a peripheral speed of 10 m / sec for 30 minutes, and then dispersed by a horizontal bead mill disperser. Then, polyisocyanate was added, and the mixture was stirred and mixed with a dissolver stirrer to prepare a composition for forming a backcoat layer.
(6)磁気テープおよび磁気テープカートリッジの作製
 厚み4.1μmの二軸延伸されたポリエチレンテレフタレート製支持体の表面上に、乾燥後の厚みが0.7μmとなるように上記(5)で調製した非磁性層形成用組成物を塗布および乾燥させて非磁性層を形成した。次いで、非磁性層上に乾燥後の厚みが0.1μmとなるように上記(5)で調製した磁性層形成用組成物を塗布して塗布層を形成した。その後に、磁性層形成用組成物の塗布層が未乾燥状態にあるうちに、磁場強度0.3Tの磁場を塗布層の表面に対し垂直方向に印加して垂直配向処理を行った後、乾燥させ、磁性層を形成した。その後、支持体の非磁性層および磁性層を形成した表面とは反対側の表面に、乾燥後の厚みが0.3μmとなるように上記(5)で調製したバックコート層形成用組成物を塗布および乾燥させてバックコート層を形成した。
 その後、金属ロールのみから構成されるカレンダロールを用いて、速度100m/分、線圧300kg/cm、および90℃のカレンダ温度(カレンダロールの表面温度)にて、表面平滑化処理(カレンダ処理)を行った(カレンダ回数:表1参照)。
 その後、長尺状の磁気テープ原反を雰囲気温度70℃の熱処理炉内に保管することにより熱処理を行った(熱処理時間:36時間)。熱処理後、1/2インチ幅にスリットして、磁気テープを得た。得られた磁気テープの磁性層に市販のサーボライターによってサーボ信号を記録することにより、LTO(Linear Tape-Open) Ultriumフォーマットにしたがう配置でデータバンド、サーボバンド、およびガイドバンドを有し、かつサーボバンド上にLTO Ultriumフォーマットにしたがう配置および形状のサーボパターン(タイミングベースサーボパターン)を有する磁気テープを得た。こうして形成されたサーボパターンは、JIS(Japanese Industrial Standards) X6175:2006およびStandard ECMA-319(June 2001)の記載にしたがうサーボパターンである。サーボバンドの合計本数は5、データバンドの合計本数は4である。
 上記サーボパターン形成後の磁気テープ(長さ970m)を熱処理用巻芯に巻き取り、この巻芯に巻き付けた状態で熱処理した。熱処理用巻芯としては、曲げ弾性率0.8GPaの樹脂製の中実状の芯状部材(外径:50mm)を使用し、巻き取り時のテンションは0.6Nとした。熱処理は、熱処理温度50℃で5時間行った。熱処理を行った雰囲気の重量絶対湿度は、10g/kg Dry airであった。
 上記熱処理後、磁気テープおよび熱処理用巻芯が十分冷却された後に磁気テープを熱処理用巻芯から取り外し、一時巻き取り用巻芯に巻き取り、その後、一時巻き取り用巻芯から磁気テープカートリッジ(LTO Ultrium7データカートリッジ)のリール(リール外径:44mm)へ最終製品長分(960m)の磁気テープを巻き取り、残り10m分は切り取り、切り取り側の末端に、市販のスプライシングテープによって、Standard ECMA(European Computer Manufacturers Association)-319(June 2001) Section 3の項目9にしたがうリーダーテープを接合させた。一時巻き取り用巻芯としては、熱処理用巻芯と同じ材料製で同じ外径を有する中実状の芯状部材を使用し、巻き取り時のテンションは0.6Nとした。
 以上により、長さ960mの磁気テープがリールに巻装された単リール型の実施例1の磁気テープカートリッジを作製した。
(6) Preparation of Magnetic Tape and Magnetic Tape Cartridge Prepared in (5) above on the surface of a biaxially stretched polyethylene terephthalate support having a thickness of 4.1 μm so that the thickness after drying is 0.7 μm. The non-magnetic layer forming composition was applied and dried to form a non-magnetic layer. Next, the composition for forming a magnetic layer prepared in (5) above was applied onto the non-magnetic layer so that the thickness after drying was 0.1 μm to form a coated layer. After that, while the coated layer of the composition for forming a magnetic layer is in an undried state, a magnetic field having a magnetic field strength of 0.3 T is applied in the direction perpendicular to the surface of the coated layer to perform a vertical alignment treatment, and then drying. And formed a magnetic layer. Then, on the surface of the support opposite to the surface on which the non-magnetic layer and the magnetic layer were formed, the composition for forming the back coat layer prepared in (5) above so that the thickness after drying is 0.3 μm is applied. It was applied and dried to form a backcoat layer.
Then, using a calendar roll composed of only metal rolls, a surface smoothing treatment (calender treatment) is performed at a speed of 100 m / min, a linear pressure of 300 kg / cm, and a calendar temperature of 90 ° C. (the surface temperature of the calendar roll). (Number of calendars: see Table 1).
Then, the raw magnetic tape was stored in a heat treatment furnace having an atmospheric temperature of 70 ° C. for heat treatment (heat treatment time: 36 hours). After the heat treatment, slits were made to a width of 1/2 inch to obtain a magnetic tape. By recording a servo signal on the magnetic layer of the obtained magnetic tape with a commercially available servo writer, it has a data band, a servo band, and a guide band in an arrangement according to the LTO (Linear Tape-Open) Ultra format, and has a servo. A magnetic tape having a servo pattern (timing-based servo pattern) arranged and shaped according to the LTO Ultra format on the band was obtained. The servo pattern thus formed is a servo pattern according to JIS (Japanese Industrial Standards) X6175: 2006 and Standard ECMA-319 (June 2001). The total number of servo bands is 5, and the total number of data bands is 4.
The magnetic tape (length 970 m) after forming the servo pattern was wound around a core for heat treatment, and the heat treatment was performed in a state of being wound around the core. As the core for heat treatment, a resin-made solid core member (outer diameter: 50 mm) having a flexural modulus of 0.8 GPa was used, and the tension at the time of winding was 0.6 N. The heat treatment was performed at a heat treatment temperature of 50 ° C. for 5 hours. The weight absolute humidity of the heat-treated atmosphere was 10 g / kg Dry air.
After the above heat treatment, after the magnetic tape and the heat treatment core have been sufficiently cooled, the magnetic tape is removed from the heat treatment core, wound around the temporary winding core, and then the magnetic tape cartridge (from the temporary winding core). Wind the magnetic tape for the final product length (960 m) on the reel (reel outer diameter: 44 mm) of the LTO Ultra7 data cartridge, cut off the remaining 10 m, and use a commercially available splicing tape at the end of the cut side to standard ECMA ( European Computer Manufacturers Association)-319 (June 2001) Leader tapes were bonded according to Item 9 of Section 3. As the winding core for temporary winding, a solid core-shaped member made of the same material as the winding core for heat treatment and having the same outer diameter was used, and the tension at the time of winding was 0.6N.
As described above, a single reel type magnetic tape cartridge of Example 1 in which a magnetic tape having a length of 960 m was wound on a reel was produced.
[実施例2]
 カレンダ温度を表1に示す温度とした点以外、実施例1と同様に磁気テープおよび磁気テープカートリッジを作製した。
[Example 2]
A magnetic tape and a magnetic tape cartridge were produced in the same manner as in Example 1 except that the calendar temperature was set to the temperature shown in Table 1.
[実施例3]
 突起形成剤として、表1に示す量のカーボンブラック(平均粒子サイズ:20nm)を使用した点以外、実施例1と同様に磁気テープおよび磁気テープカートリッジを作製した。
[Example 3]
A magnetic tape and a magnetic tape cartridge were produced in the same manner as in Example 1 except that the amount of carbon black (average particle size: 20 nm) shown in Table 1 was used as the protrusion forming agent.
[実施例4]
 非磁性層を以下のように2層形成し、形成した上層非磁性層上に実施例1と同様に磁性層形成用組成物を塗布して磁性層を形成した点およびカレンダ回数を1回にした点以外、実施例1と同様に磁気テープおよび磁気テープカートリッジを作製した。
[Example 4]
Two non-magnetic layers are formed as shown below, and the magnetic layer forming composition is applied onto the formed upper non-magnetic layer in the same manner as in Example 1 to form the magnetic layer and the number of calendars is once. A magnetic tape and a magnetic tape cartridge were produced in the same manner as in Example 1.
<下層非磁性層形成用組成物の処方>
カーボンブラック(平均粒子サイズ:20nm)      100.0部
トリオクチルアミン                     4.0部
塩化ビニル樹脂                      12.0部
ステアリン酸                        1.5部
ステアリン酸アミド                     0.3部
ブチルステアレート                     1.5部
シクロヘキサノン                    200.0部
メチルエチルケトン                   510.0部
<Prescription of composition for forming lower non-magnetic layer>
Carbon black (average particle size: 20 nm) 100.0 parts Trioctylamine 4.0 parts Vinyl chloride resin 12.0 parts Stearic acid 1.5 parts Stearic acid amide 0.3 parts Butyl stearate 1.5 parts Cyclohexanone 200. 0 parts Methyl ethyl ketone 510.0 parts
<上層非磁性層形成用組成物の処方>
非磁性無機粉末 α-酸化鉄               100.0部
 平均粒子サイズ(平均長軸長):30nm
 平均短軸長:15nm
 針状比:2.0
SONa基含有ポリウレタン樹脂             18.0部
 重量平均分子量:70,000、SONa基:0.2meq/g
ステアリン酸                        1.0部
シクロヘキサノン                    300.0部
メチルエチルケトン                   300.0部
<Prescription of composition for forming upper non-magnetic layer>
Non-magnetic inorganic powder α-iron oxide 100.0 parts Average particle size (average major axis length): 30 nm
Average minor axis length: 15 nm
Needle ratio: 2.0
SO 3 Na group-containing polyurethane resin 18.0 parts Weight average molecular weight: 70,000, SO 3 Na group: 0.2 meq / g
Stearic acid 1.0 part Cyclohexanone 300.0 part Methyl ethyl ketone 300.0 part
 上記の下層非磁性層形成用組成物および上層非磁性層形成用組成物のそれぞれについて、各成分をオープンニーダで240分間混練した後、サンドミルで分散させた。各非磁性層形成用組成物の分散条件としては、分散時間は24時間とし、分散ビーズとしてはビーズ径0.1mmのジルコニアビーズを使用した。こうして得られた分散液にポリイソシアネート(東ソー社製コロネート3041)をそれぞれ4.0部加え、更に20分間撹拌混合した後、0.5μmの孔径を有するフィルタを用いてろ過した。

 以上により、下層非磁性層形成用組成物および上層非磁性層形成用組成物を調製した。 実施例1と同様の支持体の一方の表面上に、下層非磁性層形成用組成物を乾燥後の厚みが0.25μmになるように塗布し、雰囲気温度100℃の環境下で乾燥させて下層非磁性層を形成した。下層非磁性層上に、乾燥後の厚みが0.25μmになるように上層非磁性層形成用組成物を塗布し、雰囲気温度100℃の環境下で乾燥させて上層非磁性層を形成した。
For each of the above composition for forming a lower non-magnetic layer and the composition for forming an upper non-magnetic layer, each component was kneaded with an open kneader for 240 minutes and then dispersed with a sand mill. As the dispersion conditions of each non-magnetic layer forming composition, the dispersion time was 24 hours, and zirconia beads having a bead diameter of 0.1 mm were used as the dispersed beads. 4.0 parts each of polyisocyanate (Coronate 3041 manufactured by Tosoh Corporation) was added to the dispersion obtained in this manner, and the mixture was further stirred and mixed for 20 minutes, and then filtered using a filter having a pore size of 0.5 μm.

Based on the above, a composition for forming a lower non-magnetic layer and a composition for forming an upper non-magnetic layer were prepared. The composition for forming the lower non-magnetic layer was applied onto one surface of the same support as in Example 1 so that the thickness after drying was 0.25 μm, and dried in an environment with an ambient temperature of 100 ° C. A lower non-magnetic layer was formed. A composition for forming an upper non-magnetic layer was applied onto the lower non-magnetic layer so that the thickness after drying was 0.25 μm, and the composition was dried in an environment with an atmospheric temperature of 100 ° C. to form an upper non-magnetic layer.
[実施例5]
 カレンダ温度を表1に示す温度とした点以外、実施例4と同様に磁気テープおよび磁気テープカートリッジを作製した。
[Example 5]
A magnetic tape and a magnetic tape cartridge were produced in the same manner as in Example 4, except that the calendar temperature was set to the temperature shown in Table 1.
[実施例6]
 強磁性粉末として、先に記載の方法によって作製された六方晶ストロンチウムフェライト粉末(表1中、「SrFe」)を使用した点、実施例4と同様の方法で2層の非磁性層を形成した点およびカレンダ回数を1回にした点以外、実施例3と同様に磁気テープおよび磁気テープカートリッジを作製した。
[Example 6]
As the ferromagnetic powder, a hexagonal strontium ferrite powder (“SrFe” in Table 1) prepared by the method described above was used, and two non-magnetic layers were formed by the same method as in Example 4. A magnetic tape and a magnetic tape cartridge were produced in the same manner as in Example 3, except that the points and the number of calendars were set to 1.
[実施例7]
 強磁性粉末として、先に記載の方法によって作製されたε-酸化鉄粉末(表1中、「ε-酸化鉄」)を使用した点、実施例4と同様の方法で2層の非磁性層を形成した点およびカレンダ回数を1回にした点以外、実施例3と同様に磁気テープおよび磁気テープカートリッジを作製した。
[Example 7]
As the ferromagnetic powder, ε-iron oxide powder (“ε-iron oxide” in Table 1) produced by the method described above was used, and two non-magnetic layers were used in the same manner as in Example 4. The magnetic tape and the magnetic tape cartridge were produced in the same manner as in Example 3 except that the points where the above was formed and the number of times of calendering was set to 1.
[比較例1]
 磁性層形成用組成物の成分として添加するコロイダルシリカ量を表1に示す量とした点およびカレンダ回数を1回にした点以外、実施例1と同様に磁気テープおよび磁気テープカートリッジを作製した。
[Comparative Example 1]
A magnetic tape and a magnetic tape cartridge were produced in the same manner as in Example 1 except that the amount of colloidal silica added as a component of the composition for forming a magnetic layer was set to the amount shown in Table 1 and the number of calendars was set to 1.
[比較例2]
 カレンダ回数を1回にした点以外、実施例3と同様に磁気テープおよび磁気テープカートリッジを作製した。
[Comparative Example 2]
A magnetic tape and a magnetic tape cartridge were produced in the same manner as in Example 3 except that the number of calendars was one.
[比較例3]
 先に示した特許文献1(特開2004-103137号公報)の実施例1に類する磁気テープを作製すべく、強磁性粉末として表1に記載のものを使用し、突起形成剤を添加せずに磁性層を形成し、乾燥後の非磁性層の厚みが1.3μmとなるように非磁性層形成用組成物を塗布し、かつカレンダ回数を1回にした点以外、実施例1と同様に磁気テープおよび磁気テープカートリッジを作製した。
[Comparative Example 3]
In order to prepare a magnetic tape similar to Example 1 of Patent Document 1 (Japanese Unexamined Patent Publication No. 2004-103137) shown above, the magnetic tape shown in Table 1 was used as the ferromagnetic powder, and no protrusion forming agent was added. The same as in Example 1 except that a magnetic layer is formed on the surface, a composition for forming a non-magnetic layer is applied so that the thickness of the non-magnetic layer after drying is 1.3 μm, and the number of calenders is one. A magnetic tape and a magnetic tape cartridge were manufactured in.
 実施例および比較例について、それぞれ磁気テープカートリッジを2つ作製し、1つを以下のHalf-Rqの測定のために使用し、他の1つを以下の電磁変換特性の評価のために使用した。 For Examples and Comparative Examples, two magnetic tape cartridges were made, one for the following Half-Rq measurements and the other for the evaluation of the following electromagnetic conversion characteristics. ..
[Half-Rqの測定]
 AFM測定条件は以下の条件とし、先に具体的なフロー例として示した例にしたがって、実施例および比較例の各磁気テープの磁性層の表面のHalf-Rqを求めた。
 AFM(Veeco社製Nanoscope4)をタッピングモードで用いて磁気記録媒体の磁性層の表面の面積40μm×40μmの領域を測定する。探針としてはBRUKER社製RTESP-300を使用し、分解能は512pixel×512pixelとし、スキャン速度は1画面(512pixel×512pixel)を341秒で測定する速度とする。
[Measurement of Half-Rq]
The AFM measurement conditions were as follows, and Half-Rq on the surface of the magnetic layer of each magnetic tape of Examples and Comparative Examples was determined according to the example shown above as a specific flow example.
AFM (Nanoscope 4 manufactured by Veeco) is used in a tapping mode to measure a region having an area of 40 μm × 40 μm on the surface of the magnetic layer of the magnetic recording medium. As the probe, RTESS-300 manufactured by BRUKER is used, the resolution is 512pixel × 512pixel, and the scanning speed is the speed at which one screen (512pixel × 512pixel) is measured in 341 seconds.
[電磁変換特性の評価]
 実施例および比較例の各磁気テープカートリッジを磁気記録再生装置に装着し、磁気テープを下記の走行条件で走行させ、下記の記録再生条件にて磁気信号を磁気テープの長手方向に記録し、再生ヘッド(MRヘッド)により再生した。再生信号を、シバソク社のスペクトラムアナライザーを用いて周波数分析し、300kfciの出力と、0kfci~600kfciの範囲で積分したノイズと、の比をSNR(Signal-to-Noise-ratio)とした。尚、単位kfciは、線記録密度の単位(SI単位系に換算不可)である。SNRを求める際には、磁気テープの走行を開始してから、十分に安定した信号を使用した。以下の表1には、SNRを比較例3の値をゼロとする相対値として示す。SNRの値が2.0dB以上であれば、電磁変換特性に優れると判定できる。
-走行条件-
 搬送速度(ヘッド/テープ相対速度):5.5m/秒
-記録再生条件-
(記録)
 記録トラック幅:5.0μm
 記録ギャップ:0.17μm
 磁気ヘッドの飽和磁束密度(Bs):1.8T
(再生)
 再生トラック幅:0.4μm
 シールド(shield)間距離:0.08μm
 線記録密度:300kfci
[Evaluation of electromagnetic conversion characteristics]
Each of the magnetic tape cartridges of Examples and Comparative Examples is attached to a magnetic recording / playback device, the magnetic tape is run under the following running conditions, and a magnetic signal is recorded in the longitudinal direction of the magnetic tape under the following recording / playback conditions and played back. It was reproduced by a head (MR head). The reproduced signal was frequency-analyzed using a spectrum analyzer manufactured by Shibasoku, and the ratio of the output of 300 kfci to the noise integrated in the range of 0 kfci to 600 kfci was defined as SNR (Signal-to-Noise-ratio). The unit kfci is a unit of line recording density (cannot be converted into the SI unit system). When determining the SNR, a sufficiently stable signal was used after the running of the magnetic tape was started. Table 1 below shows SNR as a relative value with the value of Comparative Example 3 as zero. If the SNR value is 2.0 dB or more, it can be determined that the electromagnetic conversion characteristics are excellent.
-Driving conditions-
Transport speed (head / tape relative speed): 5.5 m / sec-Recording / playback conditions-
(record)
Recording track width: 5.0 μm
Recording gap: 0.17 μm
Magnetic flux density of magnetic head (Bs): 1.8T
(reproduction)
Playback track width: 0.4 μm
Distance between shields: 0.08 μm
Line recording density: 300 kfci
 以上の結果を表1に示す。 The above results are shown in Table 1.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
 表1に示す結果から、実施例の磁気テープが、比較例の磁気テープと比べて電磁変換特性に優れることが確認できる。
 尚、参考値として、正の部分に加えて負の部分も含めて算出される値である二乗平均平方根粗さRqをJIS B 0601:2013にしたがい求めたところ、Rqは、実施例1:2.7nm、比較例2:2.5nm、であり、表1に示す電磁変換特性の評価結果が実施例1と比べて劣っている比較例2のRqが、実施例1のRqより小さな値であった。この結果と表1に示す結果との対比から、正の部分のみから求められるHalf-Rqの値を制御することが、電磁変換特性の向上につながることが確認できる。
From the results shown in Table 1, it can be confirmed that the magnetic tape of the example is superior in electromagnetic conversion characteristics to the magnetic tape of the comparative example.
As a reference value, the root mean square roughness Rq, which is a value calculated including the negative part in addition to the positive part, was obtained according to JIS B 0601: 2013. As a result, Rq was obtained in Example 1: 2. It is 0.7 nm, Comparative Example 2: 2.5 nm, and the evaluation result of the electromagnetic conversion characteristics shown in Table 1 is inferior to that of Example 1. The Rq of Comparative Example 2 is smaller than the Rq of Example 1. there were. From the comparison between this result and the result shown in Table 1, it can be confirmed that controlling the value of Half-Rq obtained only from the positive part leads to improvement of the electromagnetic conversion characteristic.
 本発明の一態様は、データストレージ用磁気記録媒体の技術分野において有用である。 One aspect of the present invention is useful in the technical field of magnetic recording media for data storage.

Claims (12)

  1. 非磁性支持体と、強磁性粉末を含む磁性層と、を有する磁気記録媒体であって、
    前記磁性層の表面において求められるHalf-Rqは3.0nm以下であり、
    前記Half-Rqは、前記磁性層の表面のパワースペクトラムデンシティーについて、周波数25Hz以下の成分を逆フーリエ変換して得られた表面プロファイルデータの正の部分のみについて求められた二乗平均粗さである、磁気記録媒体。
    A magnetic recording medium having a non-magnetic support and a magnetic layer containing a ferromagnetic powder.
    The Half-Rq required on the surface of the magnetic layer is 3.0 nm or less, and is
    The Half-Rq is the root mean square roughness obtained only for the positive part of the surface profile data obtained by inverse Fourier transforming the components having a frequency of 25 Hz or less with respect to the power spectrum density of the surface of the magnetic layer. , Magnetic recording medium.
  2. 前記Half-Rqは、0.5nm以上3.0nm以下である、請求項1に記載の磁気記録媒体。 The magnetic recording medium according to claim 1, wherein the Half-Rq is 0.5 nm or more and 3.0 nm or less.
  3. 前記Half-Rqは、2.0nm以下である、請求項1に記載の磁気記録媒体。 The magnetic recording medium according to claim 1, wherein the Half-Rq is 2.0 nm or less.
  4. 前記Half-Rqは、0.5nm以上2.0nm以下である、請求項3に記載の磁気記録媒体。 The magnetic recording medium according to claim 3, wherein the Half-Rq is 0.5 nm or more and 2.0 nm or less.
  5. 前記非磁性支持体と前記磁性層との間に、非磁性粉末を含む非磁性層を少なくとも1層有する、請求項1~4のいずれか1項に記載の磁気記録媒体。 The magnetic recording medium according to any one of claims 1 to 4, further comprising at least one non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer.
  6. 前記非磁性層を2層有する、請求項5に記載の磁気記録媒体。 The magnetic recording medium according to claim 5, which has two non-magnetic layers.
  7. 前記2層の非磁性層のうちの磁性層側の非磁性層に非磁性酸化鉄粉末を含み、非磁性支持体側の非磁性層にカーボンブラックを含む、請求項6に記載の磁気記録媒体。 The magnetic recording medium according to claim 6, wherein the non-magnetic layer on the magnetic layer side of the two non-magnetic layers contains non-magnetic iron oxide powder, and the non-magnetic layer on the non-magnetic support side contains carbon black.
  8. 前記非磁性酸化鉄粉末は、α-酸化鉄粉末である、請求項7に記載の磁気記録媒体。 The magnetic recording medium according to claim 7, wherein the non-magnetic iron oxide powder is α-iron oxide powder.
  9. 前記非磁性支持体の前記磁性層を有する表面側とは反対の表面側に、非磁性粉末を含むバックコート層を更に有する、請求項1~8のいずれか1項に記載の磁気記録媒体。 The magnetic recording medium according to any one of claims 1 to 8, further comprising a backcoat layer containing a non-magnetic powder on the surface side of the non-magnetic support opposite to the surface side having the magnetic layer.
  10. 磁気テープである、請求項1~9のいずれか1項に記載の磁気記録媒体。 The magnetic recording medium according to any one of claims 1 to 9, which is a magnetic tape.
  11. 請求項10に記載の磁気記録媒体を含む磁気テープカートリッジ。 A magnetic tape cartridge comprising the magnetic recording medium according to claim 10.
  12. 請求項1~10のいずれか1項に記載の磁気記録媒体と、磁気ヘッドと、を含む磁気記録再生装置。 A magnetic recording / reproducing device including the magnetic recording medium according to any one of claims 1 to 10 and a magnetic head.
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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004103137A (en) * 2002-09-11 2004-04-02 Sony Corp Magnetic recording medium and manufacturing method for magnetic recording medium
JP2006065953A (en) * 2004-08-26 2006-03-09 Sony Corp Magnetic recording medium
JP2007073086A (en) * 2005-09-02 2007-03-22 Tdk Corp Manufacturing method of magnetic recording medium
JP2010024113A (en) * 2008-07-23 2010-02-04 Fujifilm Corp Method for producing hexagonal ferrite magnetic powder, and magnetic recording medium and method for producing the same
JP2010231843A (en) * 2009-03-27 2010-10-14 Fujifilm Corp Magnetic recording medium, magnetic signal reproduction system and magnetic signal reproduction method
JP2020107380A (en) * 2018-12-28 2020-07-09 富士フイルム株式会社 Magnetic tape, magnetic tape cartridge, and magnetic tape device

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004103137A (en) * 2002-09-11 2004-04-02 Sony Corp Magnetic recording medium and manufacturing method for magnetic recording medium
JP2006065953A (en) * 2004-08-26 2006-03-09 Sony Corp Magnetic recording medium
JP2007073086A (en) * 2005-09-02 2007-03-22 Tdk Corp Manufacturing method of magnetic recording medium
JP2010024113A (en) * 2008-07-23 2010-02-04 Fujifilm Corp Method for producing hexagonal ferrite magnetic powder, and magnetic recording medium and method for producing the same
JP2010231843A (en) * 2009-03-27 2010-10-14 Fujifilm Corp Magnetic recording medium, magnetic signal reproduction system and magnetic signal reproduction method
JP2020107380A (en) * 2018-12-28 2020-07-09 富士フイルム株式会社 Magnetic tape, magnetic tape cartridge, and magnetic tape device

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