magnetic recording media

Abstract

The purpose of the present invention is to provide a magnetic recording medium of high resolution.　The present invention provides a tape-shaped magnetic recording medium including a magnetic layer and an undercoat layer, wherein a core level difference Rk, in a bearing curve created on the basis of height data of a surface on the magnetic layer side acquired by using an atomic force microscope, is 5.5 nm or less, and the average thickness of the undercoat layer is 1.50 μm or less. In addition, the present invention provides a tape cartridge including the tape-shaped magnetic recording medium.

Description

[Technical Field]

[0001] The present technology relates to magnetic recording media. [Background technology]

[0002] With the development of IoT, big data, and artificial intelligence, the amount of data collected and stored is increasing dramatically. Magnetic recording media are often used as a medium for recording large amounts of data.

[0003] Various technologies have been proposed for magnetic recording media. For example, Patent Document 1 below discloses a magnetic recording medium comprising: a low-coercivity layer containing magnetic powder and a binder and having a coercivity of 15.9 kA / m (200 oersted) or less measured in the longitudinal direction; and a magnetic layer for signal recording containing magnetic powder and a binder, formed in this order on a non-magnetic support; the magnetic layer contains iron nitride-based magnetic powder as the magnetic powder, which is essentially spherical or ellipsoidal and has an average particle size of 5 to 50 nm and an average axial ratio of 1 to 2, and which contains iron or an iron-based transition element and nitrogen as essential constituent elements; the magnetic layer is substantially perpendicularly oriented; the magnetic layer thickness is 300 nm or less; and the magnetic layer has an average surface roughness Ra of 1.0 to 3.2 nm. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-159259 Summary of the Invention [Problem to be solved by the invention]

[0005] The output of a magnetic recording medium decreases as the recording wavelength becomes shorter. However, it is desirable to obtain an output equivalent to that obtained when the recording wavelength is short as compared to when the recording wavelength is long. In order to increase the output during short wavelength recording and bring it closer to the output during long wavelength recording, it is desirable for the magnetic recording medium to have a high resolution. Therefore, a main object of the present technology is to provide a magnetic recording medium that exhibits high resolution. [Means for solving the problem]

[0006] This technology is a magnetic layer and an underlayer; In a bearing curve created based on height data of the magnetic layer side surface obtained using an atomic force microscope, the core level difference Rk is 5.5 nm or less; The average thickness of the underlayer is 1.50 μm or less. A tape-shaped magnetic recording medium is provided. The height of the bearing curve at a 10.00% area ratio may be 2.80 nm or less. The height of the bearing curve at a 20.00% area ratio may be 1.70 nm or less. The height of the bearing curve at a 30.00% area ratio may be 1.00 nm or less. The height of the bearing curve at an area ratio of 40.00% may be 0.50 nm or less. The core level difference Rk may be 5.0 nm or less. The underlayer may have an average thickness of 1.35 μm or less. The underlayer may have an average thickness of 0.80 μm or less. The magnetic layer may have an average thickness of 90 nm or less. The magnetic recording medium may have an average thickness of 5.90 μm or less. The magnetic recording medium may have an average thickness of 5.30 μm or less. The power spectral density of the magnetic layer up to a spatial wavelength of 5 μm is 3.6 nm 3It may be the following: The magnetic layer may include magnetic powder, and the magnetic powder may include hexagonal ferrite, ε iron oxide, or Co-containing spinel ferrite. In addition, this technology: the tape-shaped magnetic recording medium; a communication unit for communicating with the recording / playback device; A memory unit; a control unit that stores information received from the recording and reproducing device via the communication unit in the storage unit, and that reads out information from the storage unit in response to a request from the recording and reproducing device and transmits the information to the recording and reproducing device via the communication unit; the information includes adjustment information for adjusting the tension applied to the magnetic recording medium in the longitudinal direction; Tape cartridges are also available. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram showing a part of a cross section of a magnetic recording medium. [Figure 2] Figure 2A is a schematic diagram of the layout of the data band and the servo band, and Figure 2B is an enlarged schematic diagram of the data band. [Figure 3] 1 is an example of a TEM photograph of a magnetic layer. [Figure 4] FIG. 2 is a schematic diagram showing the cross-sectional structure of a magnetic particle. [Figure 5] FIG. 10 is a schematic diagram showing the cross-sectional structure of a magnetic particle in a modified example. [Figure 6] FIG. 10 is a diagram showing an example of the results of a calculation program. [Figure 7] 10 is a graph showing an example of a bearing curve. [Figure 8] FIG. 1 is a schematic diagram of a recording and reproducing device. [Figure 9] FIG. 2 is an exploded perspective view showing an example of the configuration of a cartridge. [Figure 10] FIG. 2 is a block diagram showing an example of the configuration of a cartridge memory. [Figure 11] FIG. 10 is a schematic diagram showing a part of a cross section of a modified magnetic recording medium. DETAILED DESCRIPTION OF THE INVENTION

[0008] Preferred embodiments for carrying out the present technology will be described below. Note that the embodiments described below are representative embodiments of the present technology, and the scope of the present technology is not limited to these embodiments.

[0009] This technology will be described in the following order. 1. Description of this technology 2. Embodiments (Examples of Coating-Type Magnetic Recording Media) (1) Structure of magnetic recording medium (2) Physical properties of magnetic recording media (3) Manufacturing method of magnetic recording medium (4) Recording and playback device (5) Cartridge (6) Effects (7) Variations 3. Working Example

[0010] 1. Description of this technology

[0011] The output of a magnetic recording medium decreases as the recording wavelength becomes shorter. However, it is desirable to obtain an output equivalent to that obtained when the recording wavelength is short as compared with when the recording wavelength is long. To achieve this, it is necessary to increase the output during short wavelength recording so that it approaches the output during long wavelength recording. In order to increase the output during short wavelength recording, it is considered effective to increase the resolution, which is one of the electromagnetic conversion characteristics of the magnetic recording medium.

[0012] The present inventors have investigated technologies for improving the resolution of magnetic recording media. As a result, they have discovered that there is a high correlation between resolution and the core level difference Rk, which will be described later. They have also discovered that thinning the underlayer contributes to improved resolution. After further investigation, they have found that a magnetic recording medium in which the core level difference Rk is equal to or less than a specific value and the average thickness of the underlayer is equal to or less than a specific value exhibits high resolution. Specifically, the magnetic recording medium of the present technology includes a magnetic layer and an underlayer, and in a bearing curve created based on height data of the magnetic layer-side surface obtained using an atomic force microscope, the core level difference Rk is 5.5 nm or less and the average thickness of the underlayer is 1.50 μm or less.

[0013] In the magnetic recording medium of the present technology, the core level difference Rk is 5.5 nm or less, preferably 5.2 nm or less, more preferably 5.0 nm or less, and even more preferably 4.7 nm or less, in a bearing curve created based on height data of the magnetic layer side surface obtained using an atomic force microscope. By keeping the core level difference Rk within this numerical range, it is possible to improve the resolution.

[0014] The magnetic recording medium of the present technology exhibits high resolution, which is thought to be because the core level difference Rk of the magnetic recording medium of the present technology is below a specific value, which allows for a larger smooth portion of the surface on the magnetic layer side.

[0015] The core level difference Rk is a value calculated using a bearing curve created based on height data of the magnetic layer side surface obtained using an atomic force microscope, and is believed to reflect the properties of the magnetic layer side surface of the magnetic recording medium. Specifically, the larger the core level difference Rk, the more irregularities there are on the magnetic layer side surface, and the smaller the core level difference Rk, the more smooth the magnetic layer side surface. The smoother the magnetic layer side surface, the smaller the spacing (the distance between the magnetic recording medium and the magnetic head) tends to be. Therefore, a magnetic recording medium of the present technology with a core level difference Rk below a certain value can increase the smoothness of the magnetic layer side surface, thereby reducing spacing. This is believed to contribute to the improved resolution of the magnetic recording medium of the present technology.

[0016] The width of the magnetic recording medium of the present technology may be, for example, 5 mm to 30 mm, particularly 7 mm to 25 mm, more particularly 10 mm to 20 mm, and even more particularly 11 mm to 19 mm. The length of the tape-shaped magnetic recording medium of the present technology may be, for example, 500 m to 1500 m. For example, a tape conforming to the LTO8 standard has a width of 12.65 mm and a length of 960 m.

[0017] The magnetic recording medium of the present technology is in the form of a tape, and may be, for example, a long magnetic recording tape. The tape-shaped magnetic recording medium of the present technology may be housed in, for example, a magnetic recording cartridge. More specifically, the magnetic recording medium may be housed in the cartridge in a state where it is wound around a reel within the magnetic recording cartridge.

[0018] In one preferred embodiment of the present technology, the magnetic recording medium of the present technology may include a magnetic layer, an underlayer, a base layer, and a back layer. These four layers may be stacked in this order. The magnetic recording medium of the present technology may include other layers in addition to these layers. These other layers may be selected appropriately depending on the type of magnetic recording medium. The magnetic recording medium of the present technology may be, for example, a coating-type magnetic recording medium. The coating-type magnetic recording medium will be described in more detail in Section 2 below.

[0019] 2. Embodiments of the Present Technology (Examples of Coating-Type Magnetic Recording Media)

[0020] (1) Structure of magnetic recording medium

[0021] First, the configuration of a magnetic recording medium 10 according to one embodiment will be described with reference to Figure 1. The magnetic recording medium 10 comprises a long base layer 11, an underlayer 12 provided on one major surface of the base layer 11, a magnetic layer 13 provided on the underlayer 12, and a back layer 14 provided on the other major surface of the base layer 11. The back layer 14 is provided as needed and may be omitted.

[0022] The magnetic recording medium 10 has a long tape shape and runs in the longitudinal direction during recording and reproduction. The surface of the magnetic layer 13 is the surface on which the magnetic head runs. The magnetic recording medium 10 is preferably used in a recording and reproduction device equipped with a ring-type head as the recording head. In this specification, the term "perpendicular direction" refers to the direction perpendicular to the surface of the magnetic recording medium 10 (the thickness direction of the magnetic recording medium 10), and the term "longitudinal direction" refers to the longitudinal direction (running direction) of the magnetic recording medium 10.

[0023] (base layer)

[0024] The base layer 11 is a non-magnetic support that supports the underlayer 12 and the magnetic layer 13. The base layer 11 has the shape of a long film. The average thickness of the base layer 11 is preferably 4.2 μm or less, more preferably 3.8 μm or less, and even more preferably 3.4 μm or less. When the average thickness of the base layer 11 is 4.2 μm or less, the recording capacity that can be recorded on one data cartridge can be increased compared to that of general magnetic recording media. The average thickness of the base layer 11 is preferably 3.0 μm or more, and more preferably 3.2 μm or more. When the average thickness of the base layer 11 is 3.0 μm or more, a decrease in the strength of the base layer 11 can be suppressed.

[0025] The average thickness of the base layer 11 is determined as follows. First, a ½-inch wide magnetic recording medium 10 is prepared and cut into a length of 250 mm to prepare a sample. Next, layers other than the base layer 11 of the sample (i.e., the underlayer 12, magnetic layer 13, and back layer 14) are removed using a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, using a Mitutoyo Laser Hologram (LGH-110C) as a measuring device, the thickness of the sample (base layer 11) is measured at five or more positions, and the measured values ​​are simply averaged (arithmetic mean) to calculate the average thickness of the base layer 11. Note that the measurement positions are selected randomly from the sample.

[0026] The base layer 11 includes, for example, at least one of polyesters, polyolefins, cellulose derivatives, vinyl resins, and other polymer resins. When the base layer 11 includes two or more of the above materials, the two or more materials may be mixed, copolymerized, or laminated.

[0027] The polyesters include, for example, at least one of PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PBN (polybutylene naphthalate), PCT (polycyclohexylene dimethylene terephthalate), PEB (polyethylene-p-oxybenzoate), and polyethylene bisphenoxycarboxylate.

[0028] The polyolefins include, for example, at least one of PE (polyethylene) and PP (polypropylene). The cellulose derivatives include, for example, at least one of cellulose diacetate, cellulose triacetate, CAB (cellulose acetate butyrate), and CAP (cellulose acetate propionate). The vinyl resins include, for example, at least one of PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride).

[0029] Examples of other polymer resins include at least one of PA (polyamide, nylon), aromatic PA (aromatic polyamide, aramid), PI (polyimide), aromatic PI (aromatic polyimide), PAI (polyamideimide), aromatic PAI (aromatic polyamideimide), PBO (polybenzoxazole, such as Zylon (registered trademark)), polyether, PEK (polyetherketone), polyetherester, PES (polyethersulfone), PEI (polyetherimide), PSF (polysulfone), PPS (polyphenylene sulfide), PC (polycarbonate), PAR (polyarylate), and PU (polyurethane).

[0030] The base layer 11 contains, for example, polyester as a primary component. The polyester may be, for example, one or a mixture of two or more of PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PBN (polybutylene naphthalate), PCT (polycyclohexylene dimethylene terephthalate), PEB (polyethylene p-oxybenzoate), and polyethylene bisphenoxycarboxylate. In this specification, the term "primary component" refers to the component that is contained in the highest proportion among the components constituting the base layer. For example, "polyester as the primary component of the base layer 11" may mean that the content of polyester in the base layer 11 is, for example, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 98% by mass or more relative to the mass of the base layer 11, or may mean that the base layer 11 is composed solely of polyester. In this embodiment, the base layer 11 may contain, in addition to polyester, resins other than polyester, as described below.

[0031] According to a preferred embodiment of the present technology, the base layer 11 may be formed from PET or PEN.

[0032] (magnetic layer)

[0033] The magnetic layer 13 is a recording layer for recording signals. The magnetic layer 13 contains, for example, a magnetic powder and a binder. If necessary, the magnetic layer 13 may further contain at least one additive selected from the group consisting of a lubricant, an antistatic agent, an abrasive, a hardener, an anticorrosive agent, and non-magnetic reinforcing particles.

[0034] As shown in Fig. 2A, the magnetic layer 13 preferably has a plurality of servo bands SB and a plurality of data bands DB in advance. The plurality of servo bands SB are provided at equal intervals in the width direction of the magnetic recording medium 10. A data band DB is provided between adjacent servo bands SB. Servo signals for tracking control of the magnetic head are written in advance in the servo bands SB. User data is recorded in the data bands DB.

[0035] The total area S of the servo bands SB relative to the surface area S of the magnetic layer 13 SB The ratio R S (=(S SB From the viewpoint of ensuring a high recording capacity, the ratio of the total area S of the servo bands SB to the surface area S of the magnetic layer 13 is preferably 4.0% or less, more preferably 3.0% or less, and even more preferably 2.0% or less. SB The ratio R S is preferably 0.8% or more from the viewpoint of ensuring five or more servo tracks.

[0036] The total area S of the servo bands SB relative to the area S of the entire surface of the magnetic layer 13 SB Ratio R S For example, the magnetic recording medium 10 is developed using a ferricolloid developer (Sigma Marker Q, manufactured by Sigma High Chemical Co., Ltd.), and then the developed magnetic recording medium 10 is observed under an optical microscope to determine the servo bandwidth W SB and the number of servo bands SB. Next, calculate the ratio R from the following formula: S Ask for. Ratio R S [%]=(((Servo bandwidth W SB)×(number of servo bands)) / (width of magnetic recording medium 10))×100

[0037] The number of servo bands SB is preferably 5 or more, more preferably 5+4n or more (where n is a positive integer), and even more preferably 9+4n or more. If the number of servo bands SB is 5 or more, the effect on the servo signal due to dimensional changes in the width direction of the magnetic recording medium 10 can be suppressed, ensuring stable recording and reproduction characteristics with less off-track. The number of servo bands SB is not particularly limited, but is, for example, 33 or less.

[0038] The number of servo bands SB can be confirmed as follows: First, the surface of the magnetic layer 13 is observed using a magnetic force microscope (MFM) to obtain an MFM image, and then the number of servo bands SB is counted using the MFM image.

[0039] Servo Bandwidth W SB From the viewpoint of ensuring a high recording capacity, the servo bandwidth W is preferably 95 μm or less, more preferably 60 μm or less, and even more preferably 30 μm or less. SB is preferably 10 μm or more. SB Manufacturing a recording head capable of reading such servo signals can be difficult.

[0040] Servo Bandwidth W SB The width of the servo band width W is obtained as follows: First, the surface of the magnetic layer 13 is observed using a magnetic force microscope (MFM) to obtain an MFM image. Next, the servo band width W is obtained using the MFM image. SB Measure the width.

[0041] As shown in Fig. 2B, the magnetic layer 13 is configured so that multiple data tracks Tk can be formed on the data band DB. From the viewpoint of ensuring high recording capacity, the data track width W is preferably 2.0 µm or less, more preferably 1.5 µm or less, and even more preferably 1.0 µm or less. The data track width W is preferably 0.02 µm or more.

[0042] The data track width W is calculated as follows. For example, the data recording pattern in the data band portion of the magnetic layer 13, where data is recorded all over, is observed using a magnetic force microscope (MFM) to obtain an MFM image. The MFM used is a Digital Instruments Dimension3100 and its analysis software. The measurement area of ​​the MFM image is 10 μm × 10 μm, and this 10 μm × 10 μm measurement area is divided into 512 × 512 (= 262,144) measurement points. Three 10 μm × 10 μm measurement areas in different locations are measured using the MFM, resulting in three MFM images. From the three MFM images obtained, the track width is measured at 10 locations using the analysis software provided with the Dimension3100, and the average (simple average) is calculated. This average value is the data track width W. The MFM measurement conditions are a sweep speed of 1 Hz, a tip used: MFMR-20, a lift height of 20 nm, and correction: Flatten order 3.

[0043] The magnetic layer 13 is configured to record data such that the minimum distance between magnetization reversals L and the data track width W satisfy the relationship W / L≦200, more preferably W / L≦60, even more preferably W / L≦45, and particularly preferably W / L≦30. If the minimum distance between magnetization reversals L is a constant value and the minimum distance between magnetization reversals L and the track width W is W / L>200 (i.e., if the track width W is large), the track recording density does not increase, and there is a risk that sufficient recording capacity cannot be ensured. Also, if the track width W is a constant value and the minimum distance between magnetization reversals L and the track width W is W / L>200 (i.e., if the minimum distance between magnetization reversals L is small), the bit length decreases and the linear recording density increases, but there is a risk that the signal-to-noise ratio (SNR) may deteriorate significantly due to spacing loss. Therefore, in order to prevent deterioration of the SNR while ensuring the recording capacity, it is preferable that W / L is in the range of W / L≦60 as described above. However, W / L is not limited to the above range, and may be W / L≦23 or W / L≦13. The lower limit of W / L is not particularly limited, but is, for example, 1≦W / L.

[0044] To ensure high recording capacity, the magnetic layer 13 is configured to record data such that the minimum distance L between magnetization reversals is preferably 55 nm or less, more preferably 53 nm or less, even more preferably 52 nm or less, 50 nm or less, 48 ​​nm or less, or 44 nm or less, and particularly preferably 40 nm or less. Taking into account the magnetic grain size, the lower limit of the minimum distance L between magnetization reversals is preferably 20 nm or more. The minimum distance L between magnetization reversals is determined based on the magnetic grain size.

[0045] The minimum distance L between magnetization reversals is calculated as follows. For example, the data recording pattern in the data band portion of the magnetic layer 13, where data is recorded over the entire surface, is observed using a magnetic force microscope (MFM) to obtain an MFM image. The MFM uses a Dimension3100 manufactured by Digital Instruments and its analysis software. The measurement area of ​​the MFM image is 2 μm × 2 μm, and this 2 μm × 2 μm measurement area is divided into 512 × 512 (= 262,144) measurement points. MFM measurements are performed on three 2 μm × 2 μm measurement areas in different locations, resulting in three MFM images. Fifty inter-bit distances are measured from a two-dimensional concavo-convex chart of the recording pattern in the obtained MFM image. The inter-bit distances are measured using the analysis software provided with the Dimension3100. The minimum value L of the inter-magnetic reversal distance is determined to be the greatest common divisor of the 50 measured inter-bit distances. The measurement conditions were: sweep speed: 1 Hz, tip used: MFMR-20, lift height: 20 nm, and correction: Flatten order 3.

[0046] The average thickness t of the magnetic layer 13 m is preferably 90 nm or less, particularly preferably 80 nm or less, more preferably 70 nm or less, and even more preferably 60 nm or less. If the average thickness of magnetic layer 13 is 90 nm or less, when a ring-type head is used as the recording head, magnetization can be recorded uniformly in the thickness direction of magnetic layer 13, thereby improving electromagnetic conversion characteristics (e.g., SNR).

[0047] The average thickness t of the magnetic layer 13 m is preferably 30 nm or more, and more preferably 35 nm or more. If the average thickness of the magnetic layer 13 is 30 nm or more, output can be ensured when an MR head is used as the reproducing head, and electromagnetic conversion characteristics (e.g., SNR) can be improved.

[0048] The average thickness t of the magnetic layer 13 mThe numerical range of t may be defined by any of the above upper limit values ​​and any of the above lower limit values, and is preferably 30 nm≦t m ≦90nm, and 35nm≦t m ≦80nm, and 35nm≦t m ≦70nm, or 35nm≦t m It may be ≦60 nm.

[0049] The average thickness t of the magnetic layer 13 m is determined, for example, as follows: The magnetic recording medium 10 is processed and sliced ​​using a method such as FIB (Focused Ion Beam). When using the FIB method, a carbon film and a tungsten thin film are formed as protective films as a pretreatment for observing the cross-sectional TEM image described below. The carbon film is formed on the magnetic layer side surface and back layer side surface of the magnetic recording medium 10 by a vapor deposition method, and the tungsten thin film is further formed on the magnetic layer side surface by a vapor deposition method or a sputtering method. The slice is performed along the length direction (longitudinal direction) of the magnetic recording medium 10. In other words, the slice forms a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic recording medium 10.

[0050] The cross section of the obtained thinned sample is observed under a transmission electron microscope (TEM) under the following conditions to obtain a TEM image. Note that the magnification and acceleration voltage may be adjusted appropriately depending on the type of device. Apparatus: TEM (Hitachi H9000NAR) Accelerating voltage: 300 kV Magnification: 100,000x

[0051] Next, using the obtained TEM image, the thickness of the magnetic layer 13 is measured at at least 10 positions in the longitudinal direction of the magnetic recording medium 10. The obtained measured values ​​are simply averaged (arithmetic average) to obtain an average value, which is the average thickness t of the magnetic layer 13. m The position where the above measurement is performed shall be selected randomly from the test piece.

[0052] (magnetic powder)

[0053] Examples of magnetic particles constituting the magnetic powder contained in the magnetic layer 13 include, but are not limited to, hexagonal ferrite, epsilon iron oxide (ε-iron oxide), Co-containing spinel ferrite, gamma hematite, magnetite, chromium dioxide, cobalt-coated iron oxide, and metals. The magnetic powder may be one of these or a combination of two or more of these. Preferably, the magnetic powder contains hexagonal ferrite, ε-iron oxide, or Co-containing spinel ferrite. More preferably, the magnetic powder is hexagonal ferrite. The hexagonal ferrite particularly preferably contains at least one of Ba and Sr. The ε-iron oxide particularly preferably contains at least one of Al and Ga. These magnetic particles may be appropriately selected by those skilled in the art based on factors such as the manufacturing method of the magnetic layer 13, the specifications of the tape, and the functions of the tape.

[0054] The shape of the magnetic particles depends on the crystal structure of the magnetic particles. For example, barium ferrite (BaFe) and strontium ferrite can be hexagonal plate-shaped. ε-iron oxide can be spherical. Cobalt ferrite can be cubic. Metal can be spindle-shaped. These magnetic particles are oriented during the manufacturing process of the magnetic recording medium 10.

[0055] The average particle size of the magnetic powder is preferably 50 nm or less, more preferably 40 nm or less, and even more preferably 30 nm or less, 25 nm or less, 22 nm or less, 21 nm or less, or 20 nm or less. The average particle size may be, for example, 10 nm or more, preferably 12 nm or more.

[0056] The average aspect ratio of the magnetic powder may be, for example, 1.0 or more and 3.0 or less, or 1.0 or more and 2.9 or less.

[0057] (An embodiment in which the magnetic powder includes hexagonal ferrite)

[0058] According to a preferred embodiment of the present technology, the magnetic powder may include hexagonal ferrite, and more particularly, may include a powder of nanoparticles containing hexagonal ferrite (hereinafter referred to as "hexagonal ferrite particles"). The hexagonal ferrite is preferably a hexagonal ferrite having an M-type structure. The hexagonal ferrite has, for example, a hexagonal plate shape or a nearly hexagonal plate shape. The hexagonal ferrite may preferably include at least one of Ba, Sr, Pb, and Ca, more preferably at least one of Ba, Sr, and Ca. Specifically, the hexagonal ferrite may be, for example, one or a combination of two or more selected from barium ferrite, strontium ferrite, and calcium ferrite, and is particularly preferably barium ferrite or strontium ferrite. Barium ferrite may further include at least one of Sr, Pb, and Ca in addition to Ba. Strontium ferrite may further include at least one of Ba, Pb, and Ca in addition to Sr.

[0059] More specifically, hexagonal ferrites have the general formula MFe 12 O 19 The alloy may have an average composition represented by the formula: where M is, for example, at least one metal selected from Ba, Sr, Pb, and Ca, preferably at least one metal selected from Ba and Sr. M may be a combination of Ba and one or more metals selected from the group consisting of Sr, Pb, and Ca. M may also be a combination of Sr and one or more metals selected from the group consisting of Ba, Pb, and Ca. In the above general formula, part of Fe may be substituted with another metal element.

[0060] When the magnetic powder contains hexagonal ferrite particles, the average particle size of the magnetic powder is preferably 50 nm or less, more preferably 40 nm or less, even more preferably 30 nm or less, 25 nm or less, 22 nm or less, 21 nm or less, or 20 nm or less. The average particle size may be, for example, 10 nm or more, preferably 12 nm or more, and more preferably 15 nm or more. For example, the average particle size of the magnetic powder may be 10 nm or more to 50 nm or less, 10 nm or more to 40 nm or less, 12 nm or more to 30 nm or less, 12 nm or more to 25 nm or less, or 15 nm or more to 22 nm or less. When the average particle size of the magnetic powder is the upper limit or less (e.g., 50 nm or less, particularly 30 nm or less), good electromagnetic conversion characteristics (e.g., SNR) can be obtained in a high-recording-density magnetic recording medium 10. When the average particle size of the magnetic powder is equal to or greater than the lower limit (for example, 10 nm or greater, preferably 12 nm or greater), the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (for example, SNR) can be obtained.

[0061] When the magnetic powder contains hexagonal ferrite particles, the average aspect ratio of the magnetic powder is preferably 1.0 to 3.0, more preferably 1.0 to 2.9, and even more preferably 2.0 to 2.9. Having the average aspect ratio of the magnetic powder within the above range can suppress aggregation of the magnetic powder, and can also suppress the resistance applied to the magnetic powder when vertically orienting the magnetic powder in the process of forming the magnetic layer 13. This can improve the vertical orientation of the magnetic powder.

[0062] When the magnetic powder contains hexagonal ferrite particles, the average particle size and average aspect ratio of the magnetic powder can be determined as follows. First, the magnetic recording medium 10 to be measured is processed and thinned using a method such as FIB (Focused Ion Beam). When using the FIB method, a carbon film and a tungsten thin film are formed as protective films as a pretreatment for observing the cross-sectional TEM image described below. The carbon film is formed on the magnetic layer side surface and back layer side surface of the magnetic recording medium 10 by vapor deposition, and the tungsten thin film is further formed on the magnetic layer side surface by vapor deposition or sputtering. The thinning is performed along the length direction (longitudinal direction) of the magnetic recording medium 10. In other words, the thinning results in a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic recording medium 10.

[0063] The cross section of the obtained thin film sample is observed using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 200 kV and a total magnification of 500,000 times, so as to include the entire magnetic layer 13 in the thickness direction of the magnetic layer 13, and a TEM photograph is taken.

[0064] Next, 50 particles are selected from the TEM photograph that are facing the observation surface and whose particle thickness can be clearly confirmed. For example, an example of a TEM photograph is shown in Figure 3. In Figure 3, for example, particles indicated by a and d are selected because their thickness can be clearly confirmed. The maximum plate thickness DA of each of the selected 50 particles is measured. The maximum plate thicknesses DA thus obtained are simply averaged (arithmetic mean) to obtain the average maximum plate thickness DA. ave Ask for.

[0065] Next, the plate diameter DB of each magnetic powder is measured. To measure the particle plate diameter DB, 50 particles whose plate diameters can be clearly confirmed are selected from the TEM photograph. For example, in Figure 3, particles indicated by b and c are selected because their plate diameters can be clearly confirmed. The plate diameter DB of each of the selected 50 particles is measured. The plate diameters DB thus determined are simply averaged (arithmetic averaged) to obtain the average plate diameter DB. aveAverage plate diameter DB ave is the average particle size.

[0066] And the average maximum plate thickness DA ave and average plate diameter DB ave The average aspect ratio of the particles (DB ave / DA ave ) is found.

[0067] When the magnetic powder comprises a powder of hexagonal ferrite particles, the average particle volume of the magnetic powder is preferably 2500 nm 3 less than 2000 nm, preferably 3 or less, and more preferably 1800 nm 3 and even more preferably 1700 nm or less. 3 Below, 1600nm 3 or below 1500nm 3 The average particle volume of the magnetic powder is preferably 500 nm or less. 3 More preferably, 700 nm 3 It could be more than that.

[0068] When the average particle volume of the magnetic powder is equal to or less than the upper limit (for example, 2500 nm 3 When the average particle volume of the magnetic powder is equal to or greater than the lower limit (for example, 500 nm 3 or more), the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (for example, SNR) can be obtained.

[0069] The average particle volume of the magnetic powder can be calculated as follows: First, as described above in relation to the method for calculating the average particle size of the magnetic powder, the average maximum plate thickness DA ave and average plate diameter DB ave Next, calculate the average particle volume V of the magnetic powder using the following formula:

[0070]

number

[0071] According to a particularly preferred embodiment of the present technology, the magnetic powder may be barium ferrite magnetic powder or strontium ferrite magnetic powder, and more preferably barium ferrite magnetic powder. The barium ferrite magnetic powder includes magnetic particles of iron oxide with barium ferrite as the main phase (hereinafter referred to as "barium ferrite particles"). The barium ferrite magnetic powder has high reliability in data recording, for example, because the coercive force does not decrease even in a high-temperature, high-humidity environment. From this perspective, barium ferrite magnetic powder is preferred as the magnetic powder.

[0072] The average particle size of the barium ferrite magnetic powder is 50 nm or less, more preferably 10 nm or more and 40 nm or less, and even more preferably 12 nm or more and 25 nm or less.

[0073] When the magnetic layer 13 contains barium ferrite magnetic powder as the magnetic powder, the average thickness t m For example, the average thickness t [nm] of the magnetic layer 13 is preferably 90 nm or less, and more preferably 80 nm or less. m 35nm≦t m ≦90nm, or 35nm≦t m It may be ≦80 nm.

[0074] Furthermore, the coercive force Hc1 measured in the thickness direction (perpendicular direction) of the magnetic recording medium 10 is preferably 2010 [Oe] or more and 3520 [Oe] or less, more preferably 2070 [Oe] or more and 3460 [Oe] or less, and even more preferably 2140 [Oe] or more and 3390 [Oe] or less.

[0075] (Embodiment in which the magnetic powder contains ε-iron oxide)

[0076] According to another preferred embodiment of the present technology, the magnetic powder may preferably comprise a powder of nanoparticles containing ε-iron oxide (hereinafter referred to as "ε-iron oxide particles"). ε-iron oxide particles can achieve high coercivity even in their fine size. The ε-iron oxide contained in the ε-iron oxide particles preferably has a crystal orientation preferentially in the thickness direction (BR>I perpendicular direction) of the magnetic recording medium 10.

[0077] The ε-iron oxide particles are spherical or nearly spherical, or cubic or nearly cubic. Because of the above-described shape of the ε-iron oxide particles, when used as magnetic particles, the contact area between particles in the thickness direction of the medium can be reduced, and aggregation between particles can be suppressed, compared to when hexagonal plate-shaped barium ferrite particles are used as magnetic particles. This improves the dispersibility of the magnetic powder, resulting in a better SNR.

[0078] The ε-iron oxide particles may have a core-shell structure. Specifically, as shown in Fig. 4, the ε-iron oxide particles include a core 21 and a two-layer shell 22 provided around the core 21. The two-layer shell 22 includes a first shell 22a provided on the core 21 and a second shell 22b provided on the first shell 22a.

[0079] The core portion 21 contains ε-iron oxide. The ε-iron oxide contained in the core portion 21 preferably has ε-Fe2O3 crystals as its main phase, and more preferably is made of single-phase ε-Fe2O3.

[0080] The first shell portion 22a covers at least a portion of the periphery of the core portion 21. Specifically, the first shell portion 22a may cover a portion of the periphery of the core portion 21, or may cover the entire periphery of the core portion 21. From the viewpoint of ensuring sufficient exchange coupling between the core portion 21 and the first shell portion 22a and improving magnetic properties, it is preferable that the entire surface of the core portion 21 be covered.

[0081] The first shell portion 22a is a so-called soft magnetic layer and may include a soft magnetic material such as α-Fe, a Ni-Fe alloy, or an Fe-Si-Al alloy. The α-Fe may be obtained by reducing ε-iron oxide contained in the core portion 21.

[0082] The second shell portion 22b is an oxide coating serving as an anti-oxidation layer. The second shell portion 22b may contain α-iron oxide, aluminum oxide, or silicon oxide. The α-iron oxide may contain at least one iron oxide selected from Fe3O4, Fe2O3, and FeO. When the first shell portion 22a contains α-Fe (soft magnetic material), the α-iron oxide may be obtained by oxidizing the α-Fe contained in the first shell portion 22a.

[0083] The ε-iron oxide particles have the first shell portion 22a as described above, which ensures thermal stability, thereby maintaining a high coercivity Hc of the core portion 21 alone and / or adjusting the coercivity Hc of the ε-iron oxide particles (core-shell particles) as a whole to a coercivity Hc suitable for recording. Furthermore, the ε-iron oxide particles have the second shell portion 22b as described above, which prevents the ε-iron oxide particles from being exposed to air during and before the manufacturing process of the magnetic recording medium 10, which can lead to rust and other damage on the particle surface, thereby preventing deterioration of the properties of the ε-iron oxide particles. Therefore, deterioration of the properties of the magnetic recording medium 10 can be prevented.

[0084] As shown in Fig. 5, the ε-iron oxide particles may have a shell portion 23 with a single layer structure. In this case, the shell portion 23 has the same structure as the first shell portion 22a. However, from the viewpoint of suppressing deterioration of the properties of the ε-iron oxide particles, it is more preferable that the ε-iron oxide particles have a shell portion 22 with a two-layer structure.

[0085] The ε-iron oxide particles may contain an additive instead of a core-shell structure, or may have a core-shell structure and contain an additive. In these cases, a portion of the Fe in the ε-iron oxide particles is substituted with the additive. By including an additive in the ε-iron oxide particles, the coercivity Hc of the entire ε-iron oxide particles can be adjusted to a coercivity Hc suitable for recording, thereby improving ease of recording. The additive is a metal element other than iron, preferably a trivalent metal element, more preferably one or more selected from the group consisting of aluminum (Al), gallium (Ga), and indium (In).

[0086] Specifically, the ε-iron oxide containing additives is ε-Fe 2-x M x O3 crystal (wherein M is a metal element other than iron, preferably a trivalent metal element, more preferably one or more selected from the group consisting of Al, Ga, and In. x is, for example, 0 <x<1である。)である。

[0087] The average particle size (average maximum particle size) of the magnetic powder is preferably 22 nm or less, more preferably 8 nm to 22 nm, and even more preferably 12 nm to 22 nm. In the magnetic recording medium 10, the actual magnetization region is a region half the size of the recording wavelength. Therefore, a good SNR can be obtained by setting the average particle size of the magnetic powder to half the shortest recording wavelength or less. Therefore, when the average particle size of the magnetic powder is 22 nm or less, good electromagnetic conversion characteristics (e.g., SNR) can be obtained in a high-recording-density magnetic recording medium 10 (e.g., a magnetic recording medium 10 configured to record signals at the shortest recording wavelength of 44 nm or less). On the other hand, when the average particle size of the magnetic powder is 8 nm or more, the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0088] The average aspect ratio of the magnetic powder is preferably 1.0 or more and 3.0 or less, more preferably 1.0 or more and 2.9 or less, and even more preferably 1.0 or more and 2.5 or less. When the average aspect ratio of the magnetic powder is within the above range, aggregation of the magnetic powder can be suppressed, and the resistance applied to the magnetic powder when the magnetic powder is vertically oriented in the process of forming the magnetic layer 13 can be suppressed. Therefore, the vertical orientation of the magnetic powder can be improved.

[0089] When the magnetic powder contains ε-iron oxide particles, the average particle size and average aspect ratio of the magnetic powder can be determined as follows. First, the magnetic recording medium 10 to be measured is processed and thinned using a method such as FIB (Focused Ion Beam). When using the FIB method, a carbon film and a tungsten thin film are formed as protective films as a pretreatment for observing the cross-sectional TEM image described below. The carbon film is formed on the magnetic layer side surface and back layer side surface of the magnetic recording medium 10 by vapor deposition, and the tungsten thin film is further formed on the magnetic layer side surface by vapor deposition or sputtering. The thinning is performed along the length direction (longitudinal direction) of the magnetic recording medium 10. In other words, the thinning results in a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic recording medium 10.

[0090] The cross section of the obtained thin film sample is observed using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 200 kV and a total magnification of 500,000 times, so as to include the entire magnetic layer 13 in the thickness direction of the magnetic layer 13, and a TEM photograph is taken.

[0091] Next, 50 particles whose particle shapes can be clearly confirmed are selected from the TEM photographs, and the long axis length DL and short axis length DS of each particle are measured. Here, the long axis length DL refers to the maximum distance between two parallel lines drawn from any angle so as to be tangent to the outline of each particle (the so-called maximum Feret diameter). On the other hand, the short axis length DS refers to the maximum length of the particle in the direction perpendicular to the long axis (DL) of the particle.

[0092] Next, the major axis lengths DL of the 50 measured particles were simply averaged (arithmetic mean) to obtain the average major axis length DL ave The average major axis length DL ave is the average particle size of the magnetic powder. The minor axis lengths DS of the 50 particles measured are simply averaged (arithmetic mean) to obtain the average minor axis length DS ave Then, calculate the average major axis length DL ave and mean minor axis length DS ave The average aspect ratio of the particles (DL ave / DS ave ) is found.

[0093] The average particle volume of the magnetic powder is preferably 2000 nm 3 or less, preferably 1900 nm 3 or less, and more preferably 1800 nm 3 and even more preferably 1700 nm or less. 3 Below, 1600nm 3 or below 1500nm 3 The average particle volume of the magnetic powder is preferably 500 nm or less. 3 More preferably, 700 nm 3 It could be more than that.

[0094] When the average particle volume of the magnetic powder is equal to or less than the upper limit (for example, 2000 nm 3 When the average particle volume of the magnetic powder is equal to or greater than the lower limit (for example, 500 nm 3 or more), the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (for example, SNR) can be obtained.

[0095] When the ε-iron oxide particles are spherical or nearly spherical, the average particle volume of the magnetic powder can be calculated as follows: First, the average major axis length DL is calculated in the same manner as in the above-mentioned method for calculating the average particle size of the magnetic powder. ave Next, calculate the average particle volume V of the magnetic powder using the following formula: V=(π / 6)×DLave 3

[0096] When the ε-iron oxide particles have a cubic shape, the average particle volume of the magnetic powder can be determined as follows. The magnetic recording medium 10 is processed and thinned by a method such as FIB (Focused Ion Beam). When using the FIB method, a carbon film and a tungsten thin film are formed as protective films as a pretreatment for observing the cross-sectional TEM image described below. The carbon film is formed on the magnetic layer side surface and the back layer side surface of the magnetic recording medium 10 by a vapor deposition method, and the tungsten thin film is further formed on the magnetic layer side surface by a vapor deposition method or a sputtering method. The thinning is performed along the length direction (longitudinal direction) of the magnetic recording medium 10. In other words, the thinning forms a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic recording medium 10.

[0097] The obtained thin film sample is observed using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 200 kV and a total magnification of 500,000 times to observe the cross section of the magnetic layer 13 in the thickness direction so as to include the entire magnetic layer 13, and a TEM photograph is obtained. Note that the magnification and acceleration voltage may be adjusted appropriately depending on the type of apparatus.

[0098] Next, 50 particles with clear particle shapes are selected from the TEM photographs, and the side length DC of each particle is measured. The side lengths DC of the 50 measured particles are then simply averaged (arithmetic mean) to obtain the average side length DC ave Next, calculate the average side length DC ave Using the following formula, the average particle volume of the magnetic powder, V ave (particle volume) is calculated. V ave =DC ave 3

[0099] The coercive force Hc of the ε iron oxide particles is preferably 2500 Oe or more, and more preferably 2800 Oe or more and 4200 Oe or less.

[0100] (An embodiment in which the magnetic powder includes Co-containing spinel ferrite)

[0101] According to yet another preferred embodiment of the present technology, the magnetic powder may include a powder of nanoparticles containing Co-containing spinel ferrite (hereinafter also referred to as "cobalt ferrite particles"). That is, the magnetic powder may be cobalt ferrite magnetic powder. The cobalt ferrite particles preferably have uniaxial crystal anisotropy. The cobalt ferrite magnetic particles have, for example, a cubic or nearly cubic shape. The Co-containing spinel ferrite may further include one or more elements selected from the group consisting of Ni, Mn, Al, Cu, and Zn in addition to Co.

[0102] Cobalt ferrite has an average composition represented by the following formula, for example. Co x M y FeO z (In the above formula, M is, for example, one or more metals selected from the group consisting of Ni, Mn, Al, Cu, and Zn. x is a value within the range of 0.4≦x≦1.0. y is a value within the range of 0≦y≦0.3, with the proviso that x and y satisfy the relationship (x+y)≦1.0. z is a value within the range of 3≦z≦4. A portion of Fe may be substituted with another metal element.)

[0103] The average particle size of the cobalt ferrite magnetic powder is preferably 25 nm or less, more preferably 23 nm or less.The coercive force Hc of the cobalt ferrite magnetic powder is preferably 2500 Oe or more, more preferably 2600 Oe to 3500 Oe.

[0104] When the magnetic powder contains cobalt ferrite particles, the average particle size of the magnetic powder is preferably 25 nm or less, more preferably 10 nm to 23 nm. When the average particle size of the magnetic powder is 25 nm or less, good electromagnetic conversion characteristics (e.g., SNR) can be obtained in a high-recording-density magnetic recording medium 10. On the other hand, when the average particle size of the magnetic powder is 10 nm or more, the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (e.g., SNR) can be obtained. When the magnetic powder contains cobalt ferrite particles, the average aspect ratio and average particle size of the magnetic powder can be determined in the same manner as when the magnetic powder contains ε-iron oxide particles.

[0105] The average particle volume of the magnetic powder is preferably 2000 nm 3 or less, preferably 1900 nm 3 or less, and more preferably 1800 nm 3 and even more preferably 1700 nm or less. 3 Below, 1600nm 3 or below 1500nm 3 The average particle volume of the magnetic powder is preferably 500 nm or less. 3 More preferably, 700 nm 3 It could be more than that.

[0106] When the average particle volume of the magnetic powder is equal to or less than the upper limit (for example, 2000 nm 3 When the average particle volume of the magnetic powder is equal to or greater than the lower limit (for example, 500 nm 3 or more), the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (for example, SNR) can be obtained.

[0107] (binder)

[0108] The binder is preferably a resin having a structure in which a crosslinking reaction has been performed on a polyurethane resin or a vinyl chloride resin, etc. However, the binder is not limited to these, and other resins may be appropriately blended depending on the physical properties required for the magnetic recording medium 10. The resin to be blended is not particularly limited as long as it is a resin that is generally used in coating-type magnetic recording media 10.

[0109] Examples of the binder include polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic acid ester-acrylonitrile copolymer, acrylic acid ester-vinyl chloride-vinylidene chloride copolymer, acrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-vinyl chloride copolymer, methacrylic acid ester-ethylene copolymer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, acrylonitrile-butadiene copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose), styrene-butadiene copolymer, polyester resin, amino resin, and synthetic rubber. One or a combination of two or more selected from these can be used.

[0110] The binder may be a thermosetting resin or a reactive resin, such as a phenolic resin, an epoxy resin, a urea resin, a melamine resin, an alkyd resin, a silicone resin, a polyamine resin, or a urea-formaldehyde resin.

[0111] Furthermore, to improve the dispersibility of the magnetic powder, polar functional groups such as -SO3M, -OSO3M, -COOM, and P=O(OM)2 may be introduced into each of the binders described above, where M is a hydrogen atom or an alkali metal such as lithium, potassium, or sodium.

[0112] Furthermore, polar functional groups include -NR1R2 and -NR1R2R3 + X - and those with a side chain having a terminal group of >NR1R2 + X - In the formula, R1, R2, and R3 are each independently a hydrogen atom or a hydrocarbon group, and X - is, for example, a halogen element ion such as fluorine, chlorine, bromine, or iodine, or an inorganic or organic ion. Examples of polar functional groups include -OH, -SH, -CN, and epoxy groups. The amount of these polar functional groups introduced into the binder is 10 -1 ~10 -8 mol / g, preferably 10 -2 ~10 -6 More preferably, it is expressed in moles / g.

[0113] (lubricant)

[0114] The magnetic layer 13 may contain a lubricant. The lubricant may be, for example, one or more selected from fatty acids and / or fatty acid esters, and may preferably contain both a fatty acid and a fatty acid ester. The fatty acid may preferably be a compound represented by the following general formula (1) or (2). For example, the fatty acid may contain one or both of a compound represented by the following general formula (1) and a compound represented by the following general formula (2).

[0115] The fatty acid ester may preferably be a compound represented by the following general formula (3) or (4). For example, the fatty acid ester may contain either or both of a compound represented by the following general formula (3) and a compound represented by the following general formula (4).

[0116] By including the lubricant in the lubricant either one or both of the compounds represented by general formula (1) and general formula (2), and either one or both of the compounds represented by general formula (3) and general formula (4), it is possible to suppress an increase in the dynamic friction coefficient of the magnetic recording medium due to repeated recording or reproduction.

[0117] CH3(CH2) k COOH (1) (However, in the above general formula (1), k is an integer selected from the range of 14 or more and 22 or less, more preferably from the range of 14 or more and 18 or less.)

[0118] CH3(CH2) n CH=CH(CH2) m COOH (2) (However, in the above general formula (2), the sum of n and m is an integer selected from the range of 12 or more and 20 or less, more preferably from the range of 14 or more and 18 or less.)

[0119] CH3(CH2) p COO(CH2) q CH3···(3) (However, in the above general formula (3), p is an integer selected from the range of 14 or more and 22 or less, more preferably 14 or more and 18 or less, and q is an integer selected from the range of 2 or more and 5 or less, more preferably 2 or more and 4 or less.)

[0120] CH3(CH2) r COO-(CH2) s CH(CH3)2 (4) (In the above general formula (4), r is an integer selected from the range of 14 to 22, and s is an integer selected from the range of 1 to 3.)

[0121] Examples of the lubricant include esters of monobasic fatty acids having 10 to 24 carbon atoms with any of monohydric to hexahydric alcohols having 2 to 12 carbon atoms, mixed esters thereof, difatty acid esters, and trifatty acid esters. Specific examples of the lubricant include lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, linolenic acid, elaidic acid, butyl stearate, pentyl stearate, heptyl stearate, octyl stearate, isooctyl stearate, and octyl myristate.

[0122] (antistatic agent)

[0123] Examples of antistatic agents include carbon black, natural surfactants, nonionic surfactants, and cationic surfactants.

[0124] (abrasive)

[0125] Examples of abrasives include acicular α-iron oxide obtained by dehydrating and annealing raw materials such as α-alumina with an α-conversion rate of 90% or more, β-alumina, γ-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, silicon nitride, titanium carbide, titanium oxide, silicon dioxide, tin oxide, magnesium oxide, tungsten oxide, zirconium oxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide, and magnetic iron oxide, and, if necessary, surface-treated with aluminum and / or silica.

[0126] (hardening agent)

[0127] Examples of the curing agent include polyisocyanates. Examples of the polyisocyanates include aromatic polyisocyanates such as an adduct of tolylene diisocyanate (TDI) and an active hydrogen compound, and aliphatic polyisocyanates such as an adduct of hexamethylene diisocyanate (HMDI) and an active hydrogen compound. The weight-average molecular weight of these polyisocyanates is preferably in the range of 100 to 4,500.

[0128] (rust inhibitor)

[0129] Examples of the rust inhibitor include phenols, naphthols, quinones, heterocyclic compounds containing a nitrogen atom, heterocyclic compounds containing an oxygen atom, and heterocyclic compounds containing a sulfur atom.

[0130] (non-magnetic reinforcing particles)

[0131] Examples of non-magnetic reinforcing particles include aluminum oxide (α, β, or γ alumina), chromium oxide, silicon oxide, diamond, garnet, emery, boron nitride, titanium carbide, silicon carbide, titanium carbide, and titanium oxide (rutile or anatase titanium oxide).

[0132] (base layer)

[0133] The underlayer 12 is a non-magnetic layer containing a non-magnetic powder and a binder. If necessary, the underlayer 12 may further contain at least one additive selected from the group consisting of a lubricant, an antistatic agent, a hardener, and an anti-rust agent.

[0134] The average thickness of the underlayer 12 is 1.50 μm or less, preferably 1.35 μm or less, more preferably 1.30 μm or less, even more preferably 1.20 μm or less, and particularly preferably 1.10 μm or less, 0.80 μm or less, 0.70 μm or less, or 0.60 μm or less. When the average thickness of the underlayer is within this range, the resolution can be improved. The average thickness of the underlayer 12 is the average thickness t m However, the magnification of the TEM image is adjusted appropriately depending on the thickness of the underlayer 12.

[0135] In a preferred embodiment of the present technology, the underlayer 12 is provided between the magnetic layer 13 and the base layer 11 .

[0136] (Non-magnetic powder)

[0137] The non-magnetic powder includes, for example, at least one of inorganic particle powder and organic particle powder. The non-magnetic powder may also include carbon powder such as carbon black. One type of non-magnetic powder may be used alone, or two or more types of non-magnetic powder may be used in combination. The inorganic particles include, for example, metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, or metal sulfides. The shape of the non-magnetic powder may be, for example, acicular, spherical, cubic, or plate-like, but is not limited to these shapes.

[0138] (binder)

[0139] The above description regarding the binder contained in the magnetic layer 13 also applies to the binder contained in the underlayer 12.

[0140] (additives)

[0141] The above explanations regarding the lubricant, antistatic agent, hardener, and anticorrosive agent contained in the magnetic layer 13 also apply to the lubricant, antistatic agent, hardener, and anticorrosive agent contained in the underlayer 12.

[0142] (Back layer)

[0143] The back layer 14 may contain a binder and a non-magnetic powder. The back layer 14 may further contain at least one additive, such as a lubricant, a hardener, or an antistatic agent, as necessary. The above description of the binder and non-magnetic powder contained in the underlayer 12 also applies to the binder and non-magnetic powder contained in the back layer.

[0144] The average particle size of the non-magnetic powder is preferably 10 nm or more and 150 nm or less, more preferably 15 nm or more and 110 nm or less. The average particle size of the non-magnetic powder is determined in the same manner as the average particle size of the magnetic powder. The non-magnetic powder may contain non-magnetic powder having two or more particle size distributions.

[0145] The average thickness of the back layer 14 (referred to herein as "average thickness t b" or "t b The average thickness t of the back layer 14 is preferably 0.6 μm or less. b By keeping the average thickness t of the back layer 14 within the above range, the thickness of the underlayer 12 and the base layer 11 can be kept thick even if the average thickness of the magnetic recording medium 10 is, for example, 5.90 μm or less, thereby maintaining the running stability of the magnetic recording medium 10 in a recording / reproducing device. b The lower limit is not particularly limited, but is, for example, 0.2 μm or more.

[0146] In a preferred embodiment of the present technology, a back layer 14 is provided on one of the two surfaces of the base layer 11, the surface opposite to the surface on which the magnetic layer 13 is provided.

[0147] The average thickness t of the back layer 14 b is calculated as follows: First, the average thickness t T Measure the average thickness t T The measurement method is as described below in this specification. Next, the back layer 14 of the sample is removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, the thickness of the sample is measured at five or more points using a Mitutoyo Laser Hologram (LGH-110C), and the measured values ​​are simply averaged (arithmetic average) to obtain the average thickness t B Then, the average thickness t of the back layer 14 is calculated using the following formula: b The measurement position is selected randomly from the sample. b [μm]=t T [μm]-t B [μm]

[0148] (The average thickness of the magnetic recording medium t T )

[0149] The average thickness of the magnetic recording medium 10 (referred to herein as "average thickness t T " or "t TThe average thickness t of the magnetic recording medium 10 is preferably 5.90 μm or less, more preferably 5.60 μm or less, even more preferably 5.30 μm or less, and particularly preferably 5.20 μm or less, or 5.10 μm or less. T is within the above range (for example, t T The average thickness t of the magnetic recording medium 10 is ≦5.90 μm, which increases the recording capacity that can be recorded in one data cartridge. T The lower limit of t is not particularly limited, but for example, 3.50 μm≦t T is.

[0150] The average thickness t of the magnetic recording medium 10 T is obtained as follows. First, a magnetic recording medium 10 having a width of 1 / 2 inch is prepared and cut into a length of 250 mm to prepare a sample. Next, a Mitutoyo Laser Hologram (LGH-110C) is used as a measuring device to measure the thickness of the sample at five or more positions, and these measurements are simply averaged (arithmetic mean) to obtain the average value t T The measurement position is selected randomly from the sample.

[0151] (2) Physical properties of magnetic recording media

[0152] In the magnetic recording medium 10, the core level difference Rk is 5.5 nm or less, preferably 5.2 nm or less, more preferably 5.0 nm or less, and even more preferably 4.7 nm or less, in a bearing curve created based on height data of the magnetic layer side surface obtained using an atomic force microscope. By having the core level difference Rk within this range, resolution can be improved. The core level difference Rk may be, for example, 3.6 nm or more or 3.8 nm or more.

[0153] The core level difference Rk can be found from a bearing curve created based on height data of the magnetic layer side surface of the magnetic recording medium 10 obtained using an atomic force microscope. Below, we will first explain how to create the bearing curve, and then explain how to calculate the core level difference Rk.

[0154] (bearing curve)

[0155] The bearing curve is created as follows: First, the uneven shape of the magnetic layer side surface of the magnetic recording medium 10 is measured using an atomic force microscope (AFM). The measurement is performed at 256 × 256 (65,536) measurement points within a 40 μm × 40 μm area. The AFM suitable for the measurement is shown below. AFM: Digital Instruments Dimension 3100 Cantilever: NanoWorld NCH-10T The AFM measurement conditions are shown below. Measurement area: 40 μm x 40 μm Resolution: 256×256 AFM probe scan direction: MD direction (longitudinal direction) of magnetic tape Measurement mode: tapping mode Scan ratio: 1Hz

[0156] Next, the data obtained by the measurement is displayed in a binary editor (Binary Editor Bz), and the values ​​of Sens.Zscan [nm / V] and Z_Scale [V], as well as the measured values ​​of each measurement point, are calculated. a,b The obtained Sens.Zscan and Z_Scale values ​​are loaded into the National Instruments program LabVIEW, the matrix is ​​inverted, and 2 bits of redundant data are deleted. The values ​​obtained from LabVIEW are loaded into a calculation program. This calculation program provides the coordinate values ​​for drawing the bearing curve. The calculation flow in this calculation program is as follows:

[0157] First, calculate the height of each measurement point using the following formula: a,b Ask for.

[0158]

number

[0159] In the magnetic recording medium of the present technology, the "height data of the magnetic layer side surface obtained using an atomic force microscope" (hereinafter also simply referred to as "height data of the magnetic layer side surface") is the height of each measurement point obtained by the above formula: a,b means.

[0160] Next, a bearing curve is created based on the height data of the magnetic layer side surface. Specifically, first, the height of each measurement point is calculated by the above formula. a,b Average (average height H a ) is calculated. Then, the height of each measurement point is calculated by AFM. a,b From the value of a The height difference H d That is, the height difference H d is calculated by the following formula: Height difference H between each measurement point d [nm] = (height of each measurement point AFM a,b )-(Average height H a )

[0161] Height difference H between each measurement point d are arranged as a one-dimensional array. The one-dimensional array is then sorted in descending order of values. H of the one-dimensional array after the sorting dis the Y coordinate value of each point that describes the bearing curve. In other words, the Y coordinate value of the bearing curve is the height difference H d In this specification, the height difference H d is called the height on the bearing curve.

[0162] Next, calculate the X coordinate value of each point on the bearing curve using the following formula. X coordinate value [%] = Data Number / Total number of data x 100 (In the above formula, Data Number is the element number of the one-dimensional array after sorting in descending order, and Total Data Number is the number of all measurement points.)

[0163] In this way, the calculation program obtains the X coordinate value and the Y coordinate value. Fig. 6 shows an example of the Data Number, X coordinate value, and Y coordinate value obtained by the calculation program.

[0164] Finally, the obtained X and Y coordinate values ​​are plotted on the XY coordinate system to create a bearing curve. In the XY coordinate system, the X axis represents the area ratio, and the Y axis represents the height (specifically, the height difference H d ) The area ratio is calculated by multiplying the height (height difference H d ) is the cumulative ratio of the height (height difference H d ) are accumulated in descending order of frequency, and expressed as a percentage with the total number of measurement points measured by AFM (65,536) set to 100. For example, if the X coordinate of point P on the bearing curve is 10 (%) and the Y coordinate is 2.50 (nm), the height (height difference H d The number of measurement points where the average particle size is 2.50 nm or more is 10% of the total number of measurement points.

[0165] (Core level difference Rk)

[0166] A method for calculating the core part level difference Rk will be described with reference to FIG. 7. FIG. 7 is a graph showing an example of a bearing curve. First, of the lines passing through two points (point A and point B) on the bearing curve where the difference in area ratio is 40%, the line with the smallest slope is found. Next, the intersection of the line with the smallest slope and an area ratio of 0% is designated as point C. The intersection of the line with the smallest slope and an area ratio of 100% is designated as point D. Finally, the absolute value of the difference between the Y coordinate of point C and the Y coordinate of point D is calculated. The absolute value of this difference is the core part level difference Rk.

[0167] (height of bearing curve at a specific area ratio)

[0168] The height of the bearing curve of the magnetic recording medium 10 at a 10.00% area ratio is preferably 2.80 nm or less, more preferably 2.50 nm or less, and even more preferably 2.30 nm or less. Having the height at a 10.00% area ratio within this range can contribute to improved resolution. The height at a 10.00% area ratio may be, for example, 1.50 nm or more or 1.80 nm or more.

[0169] The height H of the bearing curve of the magnetic recording medium 10 at a 20.00% area ratio is preferably 1.70 nm or less, more preferably 1.60 nm or less, and even more preferably 1.50 nm or less. Having the height at a 20.00% area ratio within this range can contribute to improved resolution. The height at a 20.00% area ratio may be, for example, 0.90 nm or more or 1.10 nm or more.

[0170] The height of the bearing curve of the magnetic recording medium 10 at a 30.00% area ratio is preferably 1.00 nm or less, and more preferably 0.90 nm or less. Having the height at a 30.00% area ratio within this range can contribute to improved resolution. The height at a 30.00% area ratio may be, for example, 0.40 nm or more or 0.60 nm or more.

[0171] The height of the bearing curve of the magnetic recording medium 10 at a 40.00% area ratio is preferably 0.50 nm or less, and more preferably 0.40 nm or less. Having the height at a 40.00% area ratio within this range can contribute to improved resolution. The height at a 40.00% area ratio may be, for example, 0.10 nm or more or 0.20 nm or more.

[0172] The inventors have discovered that the height of the bearing curve at each area ratio of 10.00%, 20.00%, 30.00%, and 40.00% is highly correlated with the resolution. After further investigation, the inventors have found that, as described above, a magnetic recording medium exhibiting higher resolution can be obtained by making the height at a specific area ratio equal to or less than a specific value. This is because reducing the value of the height at a specific area ratio improves the magnetic recording This is presumably because it contributes to reducing the irregularities on the surface of the medium on the magnetic layer side.

[0173] (power spectral density)

[0174] The power spectrum density (PSD) of the magnetic layer up to a spatial wavelength of 5 μm can be used as an index of waviness of the magnetic layer surface. In the magnetic recording medium 10, the power spectrum density of the magnetic layer 13 up to a spatial wavelength of 5 μm is preferably 3.6 nm. 3 or less, more preferably 3.3 nm 3 less than or equal to 3.0 nm, and even more preferably 3 Below 2.6 nm, particularly preferably 3 The power spectral density being in this range can contribute to improving the resolution. This is because the power spectral density being in the range (for example, 3.6 nm) 3 This is thought to be because the spacing can be reduced by using a

[0175] The power spectral density of the magnetic layer 13 up to a spatial wavelength of 5 μm is measured as follows. First, a 12.7 mm wide magnetic recording medium 10 is cut into 10 mm long pieces to create rectangular samples measuring 12.7 mm x 10 mm. Furthermore, identical samples are created at two locations every 10 m, for a total of three samples. Each sample is fixed onto a glass slide using carbon tape or similar. The surface is observed with an atomic force microscope (AFM) to obtain two-dimensional (2D) surface profile data. The AFM suitable for the measurement is shown below. AFM: Digital Instruments Dimension 3100 Cantilever: NanoWorld NCH-10T The AFM measurement conditions are shown below. Measurement area: 40 μm x 40 μm Resolution: 256×256 AFM probe scan direction: MD direction (longitudinal direction) of magnetic tape Measurement mode: tapping mode Scan ratio: 1Hz

[0176] Next, the 2D surface profile data obtained by AFM is subjected to the following filtering process. Flatten:Secondary Planefit: 3rd order in MD and TD (width direction)

[0177] Next, a Fast Fourier Transform (FFT) is performed on each of 256 lines of the filtered 2D surface profile data in the MD direction to obtain 256 PSDs. Next, the 256 PSDs obtained in the MD direction are averaged for each wavelength, and one averaged PSD in the MD direction (hereinafter referred to as "PSD") is obtained. MD " or "PSD(k) MD ") is obtained. The following formula is used to average the PSD in the MD direction.

number

[0178] Of the PSD values ​​obtained so far for each wavelength, the PSD values ​​for wavelengths of 5 μm or less are integrated. The integrated values ​​for the three samples are simply averaged (arithmetic mean) and used as the power spectral density of the magnetic layer 13 up to a spatial wavelength of 5 μm.

[0179] (3) Manufacturing method of magnetic recording medium

[0180] Next, a method for manufacturing the magnetic recording medium 10 having the above-described configuration will be described. First, a paint for forming the base layer is prepared by kneading and dispersing non-magnetic powder, a binder, etc. in a solvent. Next, a paint for forming the magnetic layer is prepared by kneading and dispersing magnetic powder, a binder, etc. in a solvent. The following solvents, dispersing devices, and kneading devices can be used to prepare the paint for forming the magnetic layer and the paint for forming the base layer.

[0181] Examples of solvents that can be used in preparing the coating material include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, alcohol solvents such as methanol, ethanol, and propanol, ester solvents such as methyl acetate, ethyl acetate, butyl acetate, propyl acetate, ethyl lactate, and ethylene glycol acetate, ether solvents such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran, and dioxane, aromatic hydrocarbon solvents such as benzene, toluene, and xylene, and halogenated hydrocarbon solvents such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, and chlorobenzene. These may be used alone or in appropriate combinations.

[0182] Examples of kneading devices that can be used in preparing the above-mentioned coating materials include, but are not limited to, continuous twin-screw kneaders, continuous twin-screw kneaders capable of multi-stage dilution, kneaders, pressure kneaders, roll kneaders, etc. Furthermore, examples of dispersing devices that can be used in preparing the above-mentioned coating materials include, but are not limited to, roll mills, ball mills, horizontal sand mills, vertical sand mills, spike mills, pin mills, tower mills, pearl mills (e.g., the "DCP Mill" manufactured by Eirich), homogenizers, ultrasonic dispersers, etc.

[0183] Next, a base layer forming paint is applied to one main surface of the base layer 11 and dried to form the base layer 12. Subsequently, a magnetic layer forming paint is applied to the base layer 12 and dried to form the magnetic layer 13 on the base layer 12. During drying, the magnetic powder is magnetically oriented in the thickness direction of the base layer 11, for example, by a solenoid coil. Alternatively, during drying, the magnetic powder may be magnetically oriented in the running direction (longitudinal direction) of the base layer 11, for example, by a solenoid coil, and then magnetically oriented in the thickness direction of the base layer 11. By performing such a magnetic field orientation process, the degree of perpendicular orientation of the magnetic powder can be improved. After the magnetic layer 13 is formed, a back layer 14 is formed on the other main surface of the base layer 11. This results in a magnetic recording medium 10.

[0184] The resulting magnetic recording medium 10 is then rewound around a large diameter core and hardened. Finally, the magnetic recording medium 10 is calendered and then cut to a predetermined width (e.g., 1 / 2 inch width). This completes the desired long, thin magnetic recording medium 10.

[0185] (4) Recording and playback device

[0186] (Configuration of recording / playback device)

[0187] Next, with reference to FIG. 8, an example of the configuration of a recording / reproducing device 30 that performs recording and reproducing on the magnetic recording medium 10 having the above configuration will be described.

[0188] The recording / reproducing device 30 has a configuration that allows adjustment of the tension applied in the longitudinal direction of the magnetic recording medium 10. The recording / reproducing device 30 also has a configuration that allows a magnetic recording cartridge 10A to be loaded into it. Here, for ease of explanation, a case will be described in which the recording / reproducing device 30 has a configuration that allows one magnetic recording cartridge 10A to be loaded into it, but the recording / reproducing device 30 may also have a configuration that allows multiple magnetic recording cartridges 10A to be loaded into it.

[0189] The recording / reproducing device 30 is connected to information processing devices such as a server 41 and a personal computer (hereinafter referred to as "PC") 42 via a network 43, and is configured to be able to record data supplied from these information processing devices onto the magnetic recording cartridge 10A. The shortest recording wavelength of the recording / reproducing device 30 is preferably 100 nm or less, more preferably 75 nm or less, even more preferably 60 nm or less, and particularly preferably 50 nm or less.

[0190] As shown in FIG. 8, the recording / playback device 30 includes a spindle 31, a reel 32 on the recording / playback device side, a spindle drive device 33, a reel drive device 34, a plurality of guide rollers 35, a head unit 36, a communication interface (hereinafter, I / F) 37, and a control device 38.

[0191] The spindle 31 is configured so that a magnetic recording cartridge 10A can be attached thereto. The magnetic recording cartridge 10A conforms to the LTO (Linear Tape Open) standard, and a single reel 10C around which a magnetic recording medium 10 is wound is rotatably housed in a cartridge case 10B. A V-shaped servo pattern is pre-recorded as a servo signal on the magnetic recording medium 10. The reel 32 is configured so that the leading end of the magnetic recording medium 10 pulled out from the magnetic recording cartridge 10A can be fixed.

[0192] The spindle drive device 33 is a device that rotates the spindle 31. The reel drive device 34 is a device that rotates the reel 32. When recording or reproducing data on the magnetic recording medium 10, the spindle drive device 33 and the reel drive device 34 rotate the spindle 31 and the reel 32, thereby running the magnetic recording medium 10. The guide roller 35 is a roller that guides the running of the magnetic recording medium 10.

[0193] The head unit 36 ​​includes a plurality of recording heads for recording data signals on the magnetic recording medium 10, a plurality of reproducing heads for reproducing the data signals recorded on the magnetic recording medium 10, and a plurality of servo heads for reproducing the servo signals recorded on the magnetic recording medium 10. A ring-type head can be used as the recording head, for example, but the type of recording head is not limited to this.

[0194] The communication I / F 37 is for communicating with information processing devices such as a server 41 and a PC 42, and is connected to a network 43.

[0195] The control device 38 controls the entire recording / reproducing device 30. For example, in response to a request from the information processing device, such as the server 41 or the PC 42, the control device 38 records a data signal supplied from the information processing device onto the magnetic recording medium 10 using the head unit 36. In addition, in response to a request from the information processing device, such as the server 41 or the PC 42, the control device 38 reproduces the data signal recorded on the magnetic recording medium 10 using the head unit 36, and supplies the reproduced data signal to the information processing device.

[0196] (Operation of recording / playback device)

[0197] Next, the operation of the recording / reproducing device 30 having the above configuration will be described.

[0198] First, the magnetic recording cartridge 10A is loaded into the recording / reproducing device 30, the leading end of the magnetic recording medium 10 is pulled out and transported to the reel 32 via a plurality of guide rollers 35 and a head unit 36, and the leading end of the magnetic recording medium 10 is attached to the reel 32.

[0199] Next, when an operating unit (not shown) is operated, the spindle drive device 33 and the reel drive device 34 are driven under the control of the control device 38, and the spindle 31 and the reel 32 are rotated in the same direction so that the magnetic recording medium 10 runs from the reel 10C toward the reel 32. As a result, the magnetic recording medium 10 is wound onto the reel 32, while the head unit 36 ​​records information onto the magnetic recording medium 10 or reproduces information recorded on the magnetic recording medium 10.

[0200] When the magnetic recording medium 10 is rewound onto the reel 10C, the spindle 31 and the reel 32 are rotated in the opposite direction to the above, causing the magnetic recording medium 10 to run from the reel 32 to the reel 10C. During this rewinding, the head unit 36 ​​also records information onto the magnetic recording medium 10 or reproduces information recorded on the magnetic recording medium 10.

[0201] (5) Cartridge

[0202] (Cartridge configuration)

[0203] The present technology also provides a magnetic recording cartridge (also referred to as a tape cartridge) including the magnetic recording medium of the present technology. Within the magnetic recording cartridge, the magnetic recording medium may be wound around a reel, for example. The magnetic recording cartridge may include, for example, a communication unit that communicates with a recording / reproducing device, a storage unit, and a control unit that stores information received from the recording / reproducing device via the communication unit in the storage unit, and reads information from the storage unit and transmits it to the recording / reproducing device via the communication unit in response to a request from the recording / reproducing device. The information may include adjustment information for adjusting the tension applied to the magnetic recording medium in the longitudinal direction. The adjustment information may include, for example, widthwise dimension information at multiple positions in the longitudinal direction of the magnetic recording medium. The widthwise dimension information may be dimension information obtained during (initial stage after) manufacturing of the magnetic recording medium, as described below in [Cartridge Memory Configuration], and / or dimension information obtained during recording and / or reproduction processing of the magnetic recording medium.

[0204] An example of the configuration of a cartridge 10A equipped with the magnetic recording medium 10 having the above-described configuration will be described with reference to FIG.

[0205] 9 is an exploded perspective view showing an example of the configuration of a cartridge 10A. The cartridge 10A is a magnetic recording medium cartridge that conforms to the LTO (Linear Tape-Open) standard, and includes a cartridge case 10B made up of a lower shell 212A and an upper shell 212B, a reel 10C around which magnetic tape (tape-like magnetic recording medium) 10 is wound, a reel lock 214 and a reel spring 215 for locking the rotation of the reel 10C, a spider 216 for unlocking the locked state of the reel 10C, a slide door 217 that straddles the lower shell 212A and the upper shell 212B and opens and closes a tape pull-out opening 212C provided in the cartridge case 10B, a door spring 218 that biases the slide door 217 to a closed position of the tape pull-out opening 212C, a write protect 219 for preventing accidental erasure, and a cartridge memory 211. The reel 10C is generally disk-shaped with an opening in the center, and is composed of a reel hub 213A and a flange 213B made of a hard material such as plastic. A leader pin 220 is provided at one end of the magnetic tape 10.

[0206] The cartridge memory 211 is provided near one corner of the cartridge 10A. When the cartridge 10A is loaded into the recording / reproducing device 30, the cartridge memory 211 faces a reader / writer (not shown) of the recording / reproducing device 30. The cartridge memory 211 communicates with the recording / reproducing device 30, specifically with the reader / writer (not shown), using a wireless communication standard that complies with the LTO standard.

[0207] (Cartridge memory configuration)

[0208] An example of the configuration of the cartridge memory 211 will be described with reference to FIG.

[0209] 10 is a block diagram showing an example of the configuration of the cartridge memory 211. The cartridge memory 211 includes an antenna coil (communication unit) 331 that communicates with a reader / writer (not shown) using a specified communication standard, a rectification / power circuit 332 that generates power by using induced electromotive force from radio waves received by the antenna coil 331 and rectifying it, a clock circuit 333 that generates a clock from the radio waves received by the antenna coil 331 using induced electromotive force, a detection / modulation circuit 334 that detects the radio waves received by the antenna coil 331 and modulates the signal to be transmitted by the antenna coil 331, a controller (control unit) 335 that is composed of logic circuits and the like for identifying and processing commands and data from the digital signal extracted from the detection / modulation circuit 334, and a memory (storage unit) 336 that stores information. The cartridge memory 211 also includes a capacitor 337 connected in parallel to the antenna coil 331, and the antenna coil 331 and capacitor 337 form a resonant circuit.

[0210] The memory 336 stores information related to the cartridge 10A. The memory 336 is a non-volatile memory (NVM). The memory 336 preferably has a storage capacity of approximately 32 KB or more. For example, if the cartridge 10A conforms to the LTO-9 or LTO-10 standard, the memory 336 has a storage capacity of approximately 32 KB.

[0211] The memory 336 has a first memory area 336A and a second memory area 336B. The first memory area 336A corresponds to the memory area of ​​a cartridge memory (hereinafter referred to as a "conventional cartridge memory") that conforms to the LTO standard prior to LTO8, and is an area for storing information that conforms to the LTO standard prior to LTO8. Information that conforms to the LTO standard prior to LTO8 includes, for example, manufacturing information (such as a unique number for the cartridge 10A), usage history (such as the number of times the tape has been pulled out (Thread Count)), etc.

[0212] The second memory area 336B corresponds to an extended memory area for the memory area of ​​a conventional cartridge memory. The second memory area 336B is an area for storing additional information. Here, additional information refers to information related to the cartridge 10A that is not specified in the LTO standard prior to LTO8. Examples of additional information include, but are not limited to, tension adjustment information, management ledger data, index information, and thumbnail information of videos stored on the magnetic tape 10. The tension adjustment information includes the distance between adjacent servo bands (the distance between servo patterns recorded on adjacent servo bands) when data is recorded on the magnetic tape 10. The distance between adjacent servo bands is an example of width-related information related to the width of the magnetic tape 10. The distance between servo bands will be described in detail later. In the following description, the information stored in the first memory area 336A may be referred to as "first information," and the information stored in the second memory area 336B may be referred to as "second information."

[0213] The memory 336 may have multiple banks. In this case, some of the multiple banks may form a first memory area 336A, and the remaining banks may form a second memory area 336B. Specifically, for example, if the cartridge 10A conforms to the LTO-9 or LTO-10 standard, the memory 336 may have two banks with a memory capacity of approximately 16 KB, and one of the two banks may form the first memory area 336A, and the other bank may form the second memory area 336B.

[0214] The antenna coil 331 induces an induced voltage by electromagnetic induction. The controller 335 communicates with the recording / reproducing device 30 using a specified communication standard via the antenna coil 331. Specifically, for example, mutual authentication, sending and receiving of commands, or data exchange is performed.

[0215] The controller 335 stores information received from the recording / reproducing device 30 via the antenna coil 331 in the memory 336. In response to a request from the recording / reproducing device 30, the controller 335 reads information from the memory 336 and transmits it to the recording / reproducing device 30 via the antenna coil 331.

[0216] (6) Effects

[0217] The magnetic recording medium 10 includes a magnetic layer and an underlayer, and in a bearing curve created based on height data of the magnetic layer surface obtained using an atomic force microscope, the core level difference Rk is 5.5 nm or less, and the average thickness of the underlayer is 1.50 μm or less. This allows the magnetic recording medium 10 to exhibit high resolution. As a result, the magnetic recording medium 10 can increase output during short-wavelength recording to approach the output during long-wavelength recording.

[0218] The above-mentioned resolution means the ratio of the output during short wavelength recording to the output during long wavelength recording, expressed as a reference tape ratio. The method for calculating the resolution will be described below.

[0219] When measuring the reproduction output required to calculate the resolution, the following reference tape and the following device are used in addition to the magnetic recording medium for which the resolution is to be evaluated (hereinafter also referred to as the test tape).

[0220] Reference tape: Master Standard Reference Tape (MSRT), or a tape with a known resolution compared to the MSRT (e.g., Secondary Standard Reference Tape) Device: LTO8 Full Height drive, or a recording / playback system that can be measured under the following measurement conditions (head and tape speed): Head: LTO8 Tape speed: 2.8 m / s

[0221] First, using a function generator, recording is performed on the test tape and the reference tape at the following frequencies: Recording frequency: TRD1 (0.194 μm) → 14.4 [MHz] TRD3 (0.774 μm) → 3.61 [MHz] The recording current is set to the current value at which the output is maximum.

[0222] Next, an oscilloscope (e.g., Lecroy 9354) is used to read the playback waveforms of the test tape and the reference tape. The peak-to-peak value is taken as the output. The test tape and the reference tape are each scanned 16 or more times, and the obtained outputs are averaged (arithmetic mean). This calculates the output of each of the test tape and the reference tape.

[0223] The resolution is calculated using the following formula: Resolution [%] = (TRD1 output of test tape / TRD3 output of test tape) / (TRD1 output of reference tape / TRD3 output of reference tape) x 100

[0224] The resolution of the magnetic recording medium of the present technology is, for example, 90.0% or more, preferably 92.0% or more, more preferably 94.0% or more, even more preferably 97.0% or more, and particularly preferably 100.0% or more. Having a resolution within this range contributes to making the output during short wavelength recording closer to the output during long wavelength recording.

[0225] (7) Variations

[0226] (Variation 1)

[0227] As shown in FIG. 11 , the magnetic recording medium 10 may further include a barrier layer 15 provided on at least one surface of the base layer 11. The barrier layer 15 is a layer for suppressing dimensional changes of the base layer 11 depending on the environment. For example, one cause of such dimensional changes is the hygroscopicity of the base layer 11, and providing the barrier layer 15 can reduce the rate at which moisture penetrates into the base layer 11. The barrier layer 15 includes, for example, a metal or a metal oxide. Examples of metals that can be used include at least one of Al, Cu, Co, Mg, Si, Ti, V, Cr, Mn, Fe, Ni, Zn, Ga, Ge, Y, Zr, Mo, Ru, Pd, Ag, Ba, Pt, Au, and Ta. Examples of metal oxides that can be used include metal oxides containing one or more of the above metals. More specifically, for example, at least one of Al2O3, CuO, CoO, SiO2, Cr2O3, TiO2, Ta2O5, and ZrO2 can be used. The barrier layer 15 may also contain diamond-like carbon (DLC), diamond, or the like.

[0228] The average thickness of the barrier layer 15 is preferably 20 nm or more and 1000 nm or less, and more preferably 50 nm or more and 1000 nm or less. The average thickness of the barrier layer 15 is determined in the same manner as the average thickness of the magnetic layer 13. However, the magnification of the TEM image is adjusted appropriately depending on the thickness of the barrier layer 15.

[0229] (Variation 2)

[0230] The magnetic recording medium 10 may be incorporated into a library device. That is, the present technology also provides a library device equipped with at least one magnetic recording medium 10. The library device has a configuration capable of adjusting the tension applied to the magnetic recording medium 10 in the longitudinal direction, and may be equipped with a plurality of the above-described recording / reproducing devices 30.

[0231] 3. Working Example

[0232] Hereinafter, the present technology will be specifically explained using examples, but the present technology is not limited to these examples.

[0233] [Example 1] (Preparation process of paint for forming magnetic layer) The magnetic layer-forming paint was prepared as follows. First, a first composition having the following formulation was kneaded using an extruder. Next, the kneaded first composition and a second composition having the following formulation were added to a stirring tank equipped with a disperser and premixed. Subsequently, further sand mill mixing was performed and filtering was carried out to prepare the magnetic layer-forming paint.

[0234] (First composition) Magnetic powder (hexagonal ferrite with M-type structure, composition: Ba-Ferrite, average particle volume: 2500 nm 3 ):100 parts by mass Vinyl chloride resin (cyclohexanone solution 30% by mass): 60 parts by mass (Degree of polymerization: 300, Mn=10,000, contains polar groups OSO3K=0.07 mmol / g and secondary OH=0.3 mmol / g.) Aluminum oxide powder: 5 parts by mass (α-Al2O3, average particle size 90nm) Carbon black: 1.5 parts by mass (product name: Raven 450)

[0235] (Second composition) Vinyl chloride resin: 1.1 parts by mass (Resin solution: 30% resin by mass, 70% cyclohexanone by mass) n-Butyl stearate: 2 parts by mass Methyl ethyl ketone: 121.3 parts by mass Toluene: 121.3 parts by mass Cyclohexanone: 60.7 parts by mass

[0236] Finally, 2 parts by mass of polyisocyanate (trade name: Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) and 2 parts by mass of stearic acid were added as a curing agent to the magnetic layer-forming coating material prepared as described above.

[0237] (Preparation process of paint for forming base layer) The paint for forming the base layer was prepared as follows. First, the third composition having the following composition was kneaded using an extruder. Next, the kneaded third composition and the fourth composition having the following composition were added to a stirring tank equipped with a disperser and premixed. Subsequently, further mixing was performed using a sand mill and filtering was performed to prepare the paint for forming the base layer.

[0238] (Third composition) Acicular iron oxide powder: 100 parts by mass (α-Fe2O3, average major axis length 0.11μm) Vinyl chloride resin: 55.6 parts by mass (Resin solution: 30% resin by mass, 70% cyclohexanone by mass) Carbon black: 10 parts by mass (Average particle size 20nm) Anhydrous citric acid: 3 parts by mass

[0239] (4th composition) Polyurethane resin UR8200 (manufactured by Toyobo Co., Ltd., glass transition temperature Tg = 73 ° C.): 18.5 parts by mass n-Butyl stearate: 2 parts by mass Methyl ethyl ketone: 108.2 parts by mass Toluene: 108.2 parts by mass Cyclohexanone: 18.5 parts by mass

[0240] Finally, 2 parts by mass of stearic acid was added to the coating material for forming the undercoat layer prepared as described above.

[0241] (Preparation process of paint for forming back layer) The paint for forming the back layer was prepared as follows: The following raw materials were mixed in a stirring tank equipped with a disperser, and the mixture was filtered to prepare the paint for forming the back layer: Carbon black (manufactured by Asahi Corporation, product name: #80): 100 parts by mass Polyester polyurethane: 100 parts by mass (Nippon Polyurethane Co., Ltd., product name: N-2304) Methyl ethyl ketone: 500 parts by mass Toluene: 400 parts by mass Cyclohexanone: 100 parts by mass Polyisocyanate (manufactured by Tosoh Corporation, product name: Coronate L): 10 parts by mass

[0242] (Film forming process) Using the coating material prepared as described above, a magnetic tape was prepared as follows.

[0243] First, a long PEN film (base layer) with an average thickness of 4.0 μm was prepared as a support. Next, a base layer forming paint was applied to one main surface of the PEN film and dried to form a base layer with an average thickness of 1.30 μm on one main surface of the PEN film. Next, a magnetic layer forming paint was applied to the base layer and dried to form a magnetic layer with an average thickness of 80 nm on the base layer. During drying of the magnetic layer forming paint, a solenoid coil was used to magnetically orient the magnetic powder in the thickness direction of the PEN film.

[0244] Next, a back layer-forming coating material was applied to the other main surface of the PEN film on which the underlayer and magnetic layer were formed, and then dried to form a back layer with an average thickness of 0.5 μm. The PEN film on which the underlayer, magnetic layer, and back layer were formed was then subjected to a curing treatment. This was done at a temperature of 60°C for 20 hours. The surface of the magnetic layer was then smoothed by a calendering treatment.

[0245] (Cutting process) The magnetic tape obtained as described above was cut into a width of 1 / 2 inch (12.65 mm), thereby obtaining a long magnetic tape with an average thickness of 5.88 μm.

[0246] (writing servo signals and data signals) Servo signals and data signals were written onto the long magnetic tape obtained as described above as follows: First, a servo writer was used to write servo signals onto the magnetic tape, thereby obtaining a servo bandwidth WSB Five servo bands with a width of 96 μm were formed. By writing the servo signals, a row of V-shaped magnetic patterns was formed on each servo band.

[0247] Next, using an LTO8 Full Height drive, data signals were written to the data bands between the servo bands. The tape speed was controlled to 2.8 m / s, and the recording wavelength was controlled to 0.194 μm or 0.774 μm. The resolution was calculated from the output ratio of each wavelength.

[0248] [Example 2] The magnetic powder contained in the magnetic layer is 2500nm 3 Barium ferrite magnetic powder from 1600nm 3 A magnetic tape was obtained in the same manner as in Example 1, except that the barium ferrite magnetic powder was changed to barium ferrite magnetic powder, the aluminum oxide powder contained in the magnetic layer was changed to one with a primary particle size of 50 nm, the polyurethane resin UR8200 contained in the underlayer was changed to one with a lower glass transition temperature Tg, and the average thickness of the underlayer was changed to 0.90 μm.

[0249] [Example 3] The magnetic powder contained in the magnetic layer is 2500nm 3 Barium ferrite magnetic powder from 1600nm 3 A magnetic tape was obtained in the same manner as in Example 1, except that the barium ferrite magnetic powder was changed to barium ferrite magnetic powder, the aluminum oxide powder contained in the magnetic layer was changed to one with a primary particle size of 50 nm, the polyurethane resin UR8200 contained in the underlayer was changed to one with a lower glass transition temperature Tg, and the average thickness of the underlayer was changed to 0.60 μm.

[0250] [Example 4] The magnetic powder contained in the magnetic layer is 2500nm 3 Barium ferrite magnetic powder from 1600nm 3A magnetic tape was obtained in the same manner as in Example 1, except that the barium ferrite magnetic powder was changed to barium ferrite, the aluminum oxide powder contained in the magnetic layer was changed to one with a primary particle size of 50 nm, carbon black was added after dispersing the non-magnetic powder (acicular iron oxide powder) in the underlayer (i.e., after the above-mentioned sand mill mixing), and the average thickness of the underlayer was changed to 1.09 μm.

[0251] [Example 5] The magnetic powder contained in the magnetic layer is 2500nm 3 Barium ferrite magnetic powder from 1600nm 3 A magnetic tape was obtained in the same manner as in Example 1, except that the barium ferrite magnetic powder was changed to barium ferrite, the aluminum oxide powder contained in the magnetic layer was changed to one with a primary particle size of 50 nm, carbon black was added after dispersing non-magnetic powder (acicular iron oxide powder) in the lower layer powder (i.e., after the above-mentioned sand mill mixing), and the average thickness of the underlayer was changed to 0.57 μm.

[0252] [Example 6] The magnetic powder contained in the magnetic layer is 2500nm 3 Barium ferrite magnetic powder from 1600nm 3 A magnetic tape was obtained in the same manner as in Example 1, except that the barium ferrite magnetic powder was changed to barium ferrite, the aluminum oxide powder contained in the magnetic layer was changed to one with a primary particle size of 50 nm, the dispersion time in the underlayer (i.e., the time of the sand mill mixing) was changed to 0.8 times, and the average thickness of the underlayer was changed to 1.16 μm.

[0253] [Example 7] The magnetic powder contained in the magnetic layer is 2500nm 3 Barium ferrite magnetic powder from 1600nm 3 A magnetic tape was obtained in the same manner as in Example 1, except that the barium ferrite magnetic powder was changed to barium ferrite powder, the aluminum oxide powder contained in the magnetic layer was changed to one with a primary particle size of 50 nm, the dispersion time in the underlayer (i.e., the time of the sand mill mixing) was changed to 0.8 times, and the average thickness of the underlayer was changed to 0.69 μm.

[0254] [Example 8] The magnetic powder contained in the magnetic layer is 2500nm 3 Barium ferrite magnetic powder from 1600nm 3 A magnetic tape was obtained in the same manner as in Example 1, except that the barium ferrite magnetic powder was changed to barium ferrite, the aluminum oxide powder contained in the magnetic layer was changed to one with a primary particle size of 50 nm, the non-magnetic powder (acicular iron oxide powder) contained in the underlayer powder was changed to one with an average major axis length of 0.04 μm, and the average thickness of the underlayer was changed to 0.96 μm.

[0255] [Example 9] The magnetic powder contained in the magnetic layer is 2500nm 3 Barium ferrite magnetic powder from 1600nm 3 A magnetic tape was obtained in the same manner as in Example 1, except that the barium ferrite magnetic powder was changed to barium ferrite, the aluminum oxide powder contained in the magnetic layer was changed to one with a primary particle size of 50 nm, the non-magnetic powder (acicular iron oxide powder) contained in the underlayer powder was changed to one with an average major axis length of 0.04 μm, and the average thickness of the underlayer was changed to 0.47 μm.

[0256] [Example 10] A magnetic tape was obtained in the same manner as in Example 1, except that the timing of the hardening treatment was changed from before to after calendaring and the average thickness of the underlayer was changed to 1.22 μm.

[0257] [Example 11] A magnetic tape was obtained in the same manner as in Example 1, except that the timing of the curing treatment was changed from before to after calendaring, the curing temperature was changed to 80° C., and the average thickness of the underlayer was changed to 1.31 μm.

[0258] [Example 12] A magnetic tape was obtained in the same manner as in Example 1, except that the timing of the curing treatment was changed from before to after calendaring, the curing time was changed to 40 hours, and the average thickness of the underlayer was changed to 1.27 μm.

[0259] [Example 13] A magnetic tape was obtained in the same manner as in Example 1, except that the dispersion time (ie, the sand mill mixing time) for the underlayer was changed to 0.8 times and the average thickness of the underlayer was changed to 1.23 μm.

[0260] [Example 14] The magnetic powder contained in the magnetic layer is 2500nm 3 Barium ferrite magnetic powder from 1600nm 3 A magnetic tape was obtained in the same manner as in Example 1, except that the barium ferrite magnetic powder was changed to that of Example 1, the aluminum oxide powder contained in the magnetic layer was changed to one with a primary particle size of 50 nm, an additional hardening treatment was performed after the calendaring, and the average thickness of the underlayer was changed to 1.21 μm.

[0261] [Example 15] The magnetic powder contained in the magnetic layer is 2500nm 3 Barium ferrite magnetic powder from 1600nm 3 A magnetic tape was obtained in the same manner as in Example 1, except that the barium ferrite magnetic powder was changed to that of Example 1, the aluminum oxide powder contained in the magnetic layer was changed to one with a primary particle size of 50 nm, an additional hardening treatment was performed after calendering, and the average thickness of the underlayer was changed to 1.25 μm.

[0262] [Example 16] The magnetic powder contained in the magnetic layer is 2500nm 3 Barium ferrite magnetic powder from 1600nm 3 A magnetic tape was obtained in the same manner as in Example 1, except that the barium ferrite magnetic powder was changed to that of Example 1, the aluminum oxide powder contained in the magnetic layer was changed to one with a primary particle size of 50 nm, the average thickness of the magnetic layer was changed from 80 nm to 60 nm, an additional hardening treatment was performed after the calendaring, and the average thickness of the underlayer was changed to 1.18 μm.

[0263] [Comparative Example 1] A magnetic tape was obtained in the same manner as in Example 1, except that a hardening treatment was additionally performed after calendering and the average thickness of the underlayer was changed to 1.25 μm.

[0264] Comparative Example 2 A magnetic tape was obtained in the same manner as in Example 1, except that the aluminum oxide powder contained in the magnetic layer was changed to one with a primary particle size of 50 nm, magnetic field orientation was not performed when applying the lower magnetic layer, an additional hardening treatment was performed after calendaring, and the average thickness of the underlayer was changed to 1.17 μm.

[0265] Comparative Example 3 The magnetic powder contained in the magnetic layer is 2500nm 3 Barium ferrite magnetic powder from 1600nm 3 A magnetic tape was obtained in the same manner as in Example 1, except that the magnetic powder was changed to barium ferrite, the aluminum oxide powder contained in the magnetic layer was changed to one with a primary particle size of 50 nm, no magnetic field orientation was performed when applying the magnetic layer, and the average thickness of the underlayer was changed to 1.27 μm.

[0266] Comparative Example 4 A magnetic tape was obtained in the same manner as in Example 1, except that the dispersion time (i.e., the time of sand mill mixing) for the underlayer was changed to 0.8 times, an additional hardening treatment was performed after the calendar, and the average thickness of the underlayer was changed to 1.15 μm.

[0267] Comparative Example 5 A magnetic tape was obtained in the same manner as in Example 1, except that 2.5 parts by mass of citric acid was added to the underlayer, a hardening treatment was additionally performed after calendering, and the average thickness of the underlayer was changed to 1.23 μm.

[0268] For the magnetic tapes of Examples 1 to 16 and Comparative Examples 1 to 5, the average thickness of the magnetic layer, the average thickness of the underlayer, the average thickness of the magnetic tape (magnetic recording medium), the power spectral density (Mag PSD (≦5 μm)) of the magnetic layer up to a spatial wavelength of 5 μm, the height of the bearing curve at each area ratio of 10.00%, 20.00%, 30.00%, and 40.00%, the core level difference Rk, and the resolution were measured. These were determined using the measurement method described in the above-mentioned embodiment. The measurement results for the magnetic tapes of Examples 1 to 16 and Comparative Examples 1 to 5 are shown in Table 1 below.

[0269] As a reference example, the height of the bearing curve and the core level difference Rk were measured for an LTO8 manufactured by Fujifilm Corporation at area ratios of 10.00%, 20.00%, 30.00%, and 40.00%. The measurement method was the same as in the above examples and comparative examples. The measurement results for the LTO8 of the reference example are also shown in Table 1 below. In Table 1 below, "-" indicates that no measurement was performed.

[0270] [Table 1]

[0271] From Table 1, we can see the following:

[0272] Comparing the results of Examples 1 to 16 with the results of Comparative Examples 1 to 5, it is clear that the core level difference Rk of 5.5 nm or less allows the resolution to be 90% or more.

[0273] Comparing the results of Examples 1 to 16 with the results of Comparative Examples 1 to 5, it can be seen that the resolution tends to be higher when the height at a 10.00% area ratio of the bearing curve is lower. It is believed that the resolution can be improved by setting the height at a 10.00% area ratio to, for example, 2.80 nm or less, preferably 2.50 nm or less, and more preferably 2.30 nm or less.

[0274] Comparing the results of Examples 1 to 16 with the results of Comparative Examples 1 to 5, it is found that the height of the bearing curve at an area ratio of 20.00% is generally lower in Examples 1 to 16. Setting the height at an area ratio of 20.00% to, for example, 1.70 nm or less, preferably 1.60 μm or less, is thought to contribute to improving the resolution.

[0275] Comparing the results of Examples 1 to 16 with those of Comparative Examples 1 to 5, it can be seen that the power spectral density of the magnetic layer up to a spatial wavelength of 5 μm is generally lower in Examples 1 to 16.3 The following is believed to contribute to improving resolution.

[0276] It can be seen from the comparisons between Examples 2 and 3, between Examples 4 and 5, between Examples 6 and 7, and between Examples 8 and 9 that the resolution improves as the underlayer becomes thinner. It can be seen that the resolution can be improved by setting the average thickness of the underlayer to, for example, 1.35 μm or less, preferably 0.70 μm or less.

[0277] Although the embodiments and examples of the present technology have been specifically described above, the present technology is not limited to the above-described embodiments and examples, and various modifications based on the technical ideas of the present technology are possible.

[0278] For example, the configurations, methods, steps, shapes, materials, and numerical values, etc., given in the above-described embodiments and examples are merely examples, and different configurations, methods, steps, shapes, materials, and numerical values, etc., may be used as necessary. Furthermore, the chemical formulas of compounds, etc., are representative, and are not limited to the valences, etc., given as long as they are general names of the same compounds.

[0279] Furthermore, the configurations, methods, processes, shapes, materials, numerical values, and the like of the above-described embodiments and examples can be combined with each other without departing from the spirit of the present technology.

[0280] Furthermore, in this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this specification, the upper limit or lower limit of a numerical range in a certain stage may be replaced with the upper limit or lower limit of a numerical range in another stage. Unless otherwise specified, the materials exemplified in this specification can be used alone or in combination of two or more types.

[0281] The present technology can also be configured as follows. [1] a magnetic layer and an underlayer; In a bearing curve created based on height data of the magnetic layer side surface obtained using an atomic force microscope, the core level difference Rk is 5.5 nm or less; The average thickness of the underlayer is 1.50 μm or less. A tape-type magnetic recording medium. [2] The magnetic recording medium according to [1], wherein the height of the bearing curve at a 10.00% area ratio is 2.80 nm or less. [3] The magnetic recording medium according to [1] or [2], wherein the height of the bearing curve at a 20.00% area ratio is 1.70 nm or less. [4] The magnetic recording medium according to any one of [1] to [3], wherein the height of the bearing curve at an area ratio of 30.00% is 1.00 nm or less. [5] The magnetic recording medium according to any one of [1] to [4], wherein the height of the bearing curve at an area ratio of 40.00% is 0.50 nm or less. [6] The magnetic recording medium according to any one of [1] to [5], wherein the core level difference Rk is 5.0 nm or less. [7] The magnetic recording medium according to any one of [1] to [6], wherein the underlayer has an average thickness of 1.35 μm or less. [8] The magnetic recording medium according to any one of [1] to [7], wherein the underlayer has an average thickness of 0.80 μm or less. [9] The magnetic recording medium according to any one of [1] to [8], wherein the average thickness of the magnetic layer is 90 nm or less.

[10] The magnetic recording medium according to any one of [1] to [9], wherein the average thickness of the magnetic recording medium is 5.90 μm or less.

[11] The magnetic recording medium according to any one of [1] to

[10] , wherein the average thickness of the magnetic recording medium is 5.30 μm or less.

[12] The power spectral density of the magnetic layer up to a spatial wavelength of 5 μm is 3.6 nm 3 The magnetic recording medium according to any one of [1] to

[11] below.

[13] The magnetic recording medium according to any one of [1] to

[12] , wherein the magnetic layer contains magnetic powder, and the magnetic powder contains hexagonal ferrite, ε iron oxide, or Co-containing spinel ferrite.

[14] [1] to

[13] , and a tape-shaped magnetic recording medium. a communication unit for communicating with the recording / playback device; A memory unit; a control unit that stores information received from the recording and reproducing device via the communication unit in the storage unit, and that reads out information from the storage unit in response to a request from the recording and reproducing device and transmits the information to the recording and reproducing device via the communication unit; The information includes adjustment information for adjusting the tension applied to the magnetic recording medium in the longitudinal direction. Tape cartridge. [Explanation of symbols]

[0282] 10 Magnetic recording media 11 Base Layer 12 Base layer 13 Magnetic layer 14 Back layer

Claims

1. a magnetic layer and an underlayer; In a bearing curve created based on height data of the magnetic layer side surface obtained using an atomic force microscope, a core level difference Rk is 5.5 nm or less; The average thickness of the underlayer is 1.50 μm or less. A tape-type magnetic recording medium.

2. 2. The magnetic recording medium according to claim 1, wherein the height of the bearing curve at a 10.00% area ratio is 2.80 nm or less.

3. 2. The magnetic recording medium according to claim 1, wherein the height of the bearing curve at a 20.00% area ratio is 1.70 nm or less.

4. 2. The magnetic recording medium according to claim 1, wherein the height of the bearing curve at an area ratio of 30.00% is 1.00 nm or less.

5. 2. The magnetic recording medium according to claim 1, wherein the height of the bearing curve at an area ratio of 40.00% is 0.50 nm or less.

6. 2. The magnetic recording medium according to claim 1, wherein the core level difference Rk is 5.0 nm or less.

7. 2. The magnetic recording medium according to claim 1, wherein the underlayer has an average thickness of 1.35 [mu]m or less.

8. 2. The magnetic recording medium according to claim 1, wherein the underlayer has an average thickness of 0.80 [mu]m or less.

9. 2. The magnetic recording medium according to claim 1, wherein the average thickness of the magnetic layer is 90 nm or less.

10. 2. The magnetic recording medium according to claim 1, wherein the average thickness of the magnetic recording medium is 5.90 [mu]m or less.

11. 2. The magnetic recording medium according to claim 1, wherein the average thickness of the magnetic recording medium is 5.30 [mu]m or less.

12. The power spectral density of the magnetic layer up to a spatial wavelength of 5 μm is 3.6 nm ３ 2. The magnetic recording medium according to claim 1, wherein:

13. 2. The magnetic recording medium according to claim 1, wherein the magnetic layer contains magnetic powder, and the magnetic powder contains hexagonal ferrite, ε-iron oxide, or Co-containing spinel ferrite.

14. a tape-shaped magnetic recording medium according to claim 1; a communication unit for communicating with the recording / playback device; A memory unit; a control unit that stores information received from the recording and reproducing device via the communication unit in the storage unit, and that reads out information from the storage unit in response to a request from the recording and reproducing device and transmits the information to the recording and reproducing device via the communication unit; the information includes adjustment information for adjusting the tension applied to the magnetic recording medium in the longitudinal direction; Tape cartridge.

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