Magnetic recording media

Abstract

The purpose of the present invention is to provide a magnetic recording medium that has excellent running stability even when stored in a high-temperature environment.　The present invention provides a magnetic recording medium in which, when dynamic viscoelasticity measurement is performed on the magnetic recording medium at a frequency of 10 Hz and a heating rate of 2°C / min, the average value A(E") of the loss elastic modulus E" in the temperature range of 60°C to 65°C is 0.06 GPa or less, and the average height Rpk of the protruding peaks measured using a non-contact profilometer using optical interference is 2.4 nm or less.

Description

[Technical Field]

[0001] This technology relates to magnetic recording media. [Background technology]

[0002] For example, with the development of IoT, big data, and artificial intelligence, the amount of data collected and stored has increased 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 describes a magnetic recording media that can be reproduced or recorded on well even after long-term storage. When dynamic viscoelasticity measurements are performed on the magnetic recording media described in the document at a frequency of 10 Hz and a heating rate of 2 °C / min, the difference between the maximum and minimum values ​​of the viscosity term E'' in the temperature range of 0 °C to 80 °C is 0.18 GPa or less. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6766988 [Overview of the project] [Problems that the invention aims to solve]

[0005] One of the objectives of this technology is to provide a magnetic recording tape that exhibits excellent running stability even when stored in a high-temperature environment. [Means for solving the problem]

[0006] This technology is When dynamic viscoelasticity measurements were performed on a magnetic recording medium at a frequency of 10 Hz and a heating rate of 2 °C / min, the average value A of the loss modulus E'' in the temperature range of 60 °C to 65 °C was obtained. (E”) The pressure is 0.06 GPa or less, and, The average height Rpk of the protruding peaks measured using a non-contact roughness meter using optical interference is 2.4 nm or less. A magnetic recording medium is provided. When the dynamic viscoelasticity measurement is performed on the magnetic recording medium, the average value A of the storage elastic modulus E' in the temperature range of 60°C to 65°C (E’) may be 6 GPa or less. When the dynamic viscoelasticity measurement is performed on the magnetic recording medium, the average value A of Tanδ (loss elastic modulus E” / storage elastic modulus E') in the temperature range of 60°C to 65°C (Tanδ) may be 0.017 or less. The average thickness t of the base layer included in the magnetic recording medium Base may be 4.5 μm or less. The average thickness t of the magnetic recording medium T may be 5.3 μm or less. The stiffness S of the magnetic recording medium may be 1.4 mgf / μm or less. When the dynamic viscoelasticity measurement is performed on the magnetic recording medium, the average value A of the loss elastic modulus E” in the temperature range of 60°C to 65°C (E”) may be 0.05 GPa or less. When the dynamic viscoelasticity measurement is performed on the magnetic recording medium, the average value A of the loss elastic modulus E” in the temperature range of 60°C to 65°C (E”) may be 0.04 GPa or less. The average height Rpk of the protruding peaks may be 2.3 nm or less. <00s00324>The average height Rpk of the protruding peaks may be 2.2 nm or less. <000m0325>When the dynamic viscoelasticity measurement is performed on the magnetic recording medium, the average value A of Tanδ (Tanδ) may be 0.016 or less. When the dynamic viscoelasticity measurement is performed on the magnetic recording medium, the average value A of Tanδ (Tanδ) may be 0.015 or less. When the magnetic recording medium is subjected to a load of 0.55 N in the longitudinal direction for 40 hours in an environment of a temperature of 65°C and a humidity of 40%, the width fluctuation amount ΔW40h However, -600 ppm ≤ ΔW 40h It may be that way. The magnetic recording medium may have a magnetic layer containing magnetic powder. The magnetic recording medium may be a vacuum thin-film type magnetic recording medium. Furthermore, this technology also provides a magnetic recording cartridge in which the magnetic recording medium is wound on a reel and housed in a case. [Brief explanation of the drawing]

[0007] [Figure 1] This is a cross-sectional view showing the configuration of a magnetic recording medium according to the first embodiment. [Figure 2] This is an exploded perspective view showing an example of the configuration of a magnetic recording cartridge. [Figure 3A] This figure shows an example of the shape of magnetic powder particles. [Figure 3B] This is an example of a TEM image of a sample cross-section. [Figure 3C] Here is another example of a TEM image of a sample cross-section. [Figure 4] This figure shows the measuring device used to measure the amplitude variation ΔW40h. [Figure 5] This diagram illustrates the arrangement of five support members in a measuring device used to measure the width variation ΔW40h. [Figure 6] This is a schematic diagram showing the configuration of a recording and playback device. [Figure 7] This is a cross-sectional view showing the configuration of a magnetic recording medium in a modified example. [Figure 8] This is an example of a schematic cross-sectional diagram of a vacuum thin-film magnetic recording medium. [Figure 9] This figure shows an example of the configuration of a sputtering machine used in the manufacture of magnetic recording media. [Figure 10] This is an example of a schematic cross-sectional diagram of a vacuum thin-film magnetic recording medium. [Figure 11] This is a cylinder representing an example of a cartridge memory configuration. [Figure 12]This is an exploded perspective view showing an example of the configuration of a modified magnetic recording cartridge. [Figure 13] This figure shows an example of the change in σsw over time as a magnetic tape moves. [Figure 14] This figure shows an example of the change in σsw over time as a magnetic tape moves. [Figure 15] This figure shows the measurement results of the storage modulus and loss modulus of the magnetic tape of Example 1. [Figure 16] This figure shows the measurement results of Tanδ for the magnetic tape of Example 1. [Figure 17] This figure shows the measurement results of the width variation of the magnetic tape in Example 1 and Comparative Example 3. [Modes for carrying out the invention]

[0008] The following describes preferred embodiments for implementing this technology. Note that the embodiments described below represent typical embodiments of this technology, and the scope of this technology is not limited to these embodiments.

[0009] This technology will be explained in the following order. 1. Description of this technology 2. First Embodiment (Coated Magnetic Recording Medium) (1) Configuration of magnetic recording medium (2) Explanation of each layer (3) Physical properties and structure (4) Method for manufacturing magnetic recording media (5) Recording and playback device (6) Variant 3. Second Embodiment (Example of a Vacuum Thin-Film Magnetic Recording Medium) (1) Configuration of magnetic recording medium (2) Explanation of each layer (3) Physical properties and structure (4) Configuration of the sputtering apparatus (5) Method for manufacturing magnetic recording media (6) Variant (7) Other examples of magnetic recording media 4. Third Embodiment (1) One embodiment of a magnetic recording cartridge (2) Modified magnetic recording cartridge 5. Examples

[0010] In this specification, unless otherwise specified regarding the measurement environment in relation to the description of the measurement method, measurements shall be performed under conditions of 25°C ± 2°C and 50% RH ± 5% RH.

[0011] 1. Description of this technology

[0012] With increasing demand for archiving, high-capacity tape storage is increasingly being integrated into cloud systems. However, current tape storage systems have a narrower recommended temperature range for actual operation and storage than HDDs and semiconductor memory. Therefore, when integrating tape storage systems into cloud systems, careful consideration must be given to temperature environment management. This leads to increased energy consumption required to maintain the environment in the cloud system's data center, which is a hindrance to introducing tape storage into data centers. For example, in a tape library system within a data center, while the temperature of the drive environment is controlled to some extent, it is desirable that the storage environment for magnetic recording cartridges that are not in recording or playback mode is not controlled, from the perspective of reducing power consumption or CO2 emissions.

[0013] By enabling tape storage systems to operate in the same temperature environment as HDDs, tape storage is expected to become more widely used in data centers. HDDs are sometimes used in high-temperature environments, and the storage stability or running stability in such high-temperature environments has not been given much consideration to tape storage until now. Therefore, it is important to address the shape deformation that may occur in high-temperature environments. Regarding this shape deformation, for example, when a magnetic tape is run in a drive, the tension on the tape pulls it longitudinally, and the creep phenomenon causes it to narrow in the width direction. To address this shape deformation, it is conceivable to adjust the storage modulus of the magnetic tape, for example, by using a base film with a high storage modulus as the base layer of the magnetic tape.

[0014] Here, it is necessary to consider that in order to achieve high total capacity tape storage, the capacity of cartridges is also increasing. Specifically, the total thickness of the tape needs to be made very thin, for example, 5.3 μm or less. In addition, in order to improve track density, the track width also needs to be made very narrow, for example, 1.5 μm or less. Furthermore, in order to reduce the spacing between the tape and the head, it is necessary to improve the surface properties of the magnetic tape while also ensuring proper contact between the tape and the head to reduce friction.

[0015] Currently, negative pressure heads are the mainstream choice for drive heads. When negative pressure heads are used, in order to ensure proper contact between the magnetic tape, which has a high storage modulus, and the recording / playback elements on the head block, it is desirable to increase the angle at which the magnetic tape enters the head to increase the negative pressure, and to widen the head block to ensure sufficient distance from the end of the head bar to the recording / playback elements to ensure proper contact. However, especially at high temperatures, increasing the negative pressure increases the contact pressure and the contact area, which can easily lead to increased friction.

[0016] Furthermore, in order to reduce the contact area, it is conceivable to employ a head block with a narrow head block width, and to use magnetic tape with a low storage modulus so that it can make proper contact with the recording and playback elements even when such a head block is used. However, magnetic tape with a low storage modulus is prone to wear of the contact surface when running in a high-temperature environment, which can cause misalignment of the tape's running position (for example, index σ). sw This makes it easier for (as represented by) to occur. Furthermore, magnetic tapes with a low storage modulus of elasticity will experience a larger change in width when stored in a high-temperature environment, making track misalignment more likely when running after storage in a high-temperature environment, and increasing the likelihood of the run stopping.

[0017] The inventors have discovered that a specific magnetic recording medium can improve storage stability in high-temperature environments and improve running stability after storage in high-temperature environments. Furthermore, the inventors have discovered that this specific magnetic recording medium can also improve electromagnetic conversion characteristics. More specifically, it was found that by using a specific loss modulus and a specific amount of surface protrusions on the magnetic layer, the change in the tape width direction during running or storage in a high-temperature environment can be reduced, and the increase in friction during running can also be suppressed. Furthermore, this technology makes it possible to achieve these effects without increasing the storage modulus.

[0018] In other words, when dynamic viscoelasticity measurements are performed on the magnetic recording medium of this technology at a frequency of 10 Hz and a heating rate of 2 °C / min, the average value A of the loss modulus E'' in the temperature range of 60 °C to 65 °C is obtained. (E”) The average value of the loss modulus E'' is 0.06 GPa or less, and the average height Rpk of the protruding peaks measured using a non-contact roughness meter with optical interference is 2.4 nm or less. (E”) Furthermore, by controlling the average height Rpk of the protruding peaks, it is possible to improve storage stability in high-temperature environments and running stability after storage in high-temperature environments. In addition, it is possible to improve electromagnetic conversion characteristics.

[0019] The magnetic recording medium according to this technology may preferably be a long magnetic recording medium, for example, a magnetic recording tape (particularly a long magnetic recording tape).

[0020] A magnetic recording medium according to this technology may have a magnetic layer, a non-magnetic layer (underlayment), a base layer, and a back layer in this order, and may also include other layers. These other layers may be appropriately selected depending on the type of magnetic recording medium. In one embodiment, the magnetic recording medium may be, for example, a coated magnetic recording medium. That is, the recording medium may have a magnetic layer containing magnetic powder. The coated magnetic recording medium will be described in more detail below in section 2. In other embodiments, the recording medium may be a vacuum thin-film type magnetic recording medium, that is, a sputtered type magnetic recording medium. The vacuum thin-film type magnetic recording medium will be described in more detail below in section 3.

[0021] The magnetic recording medium of this technology may have, for example, at least one data band and at least two servo bands. The number of data bands may be, for example, 2 to 10, particularly 3 to 6, and more particularly 4 or 5. The number of servo bands may be, for example, 3 to 11, particularly 4 to 7, and more particularly 5 or 6. These servo bands and data bands may be arranged, for example, extending in the longitudinal direction of a long magnetic recording medium (particularly a magnetic recording tape), and particularly substantially parallel to each other. The data bands and servo bands may be provided in the magnetic layer. An example of a magnetic recording medium having data bands and servo bands in this way is a magnetic recording tape conforming to the LTO (Linear Tape-Open) standard. That is, the magnetic recording medium may be a magnetic recording tape conforming to the LTO standard. For example, the magnetic recording medium may be a magnetic recording tape conforming to LTO9 or a later standard (e.g., LTO10, LTO11, or LTO12). The width of the aforementioned elongated magnetic recording medium (especially magnetic recording tape) can be, for example, 5 mm to 30 mm, more 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 elongated magnetic recording medium (especially magnetic recording tape) can be, for example, 500 m to 1500 m. For example, a tape conforming to the LTO9 standard has a width of 12.65 mm and a length of 1035 m.

[0022] 2. First Embodiment (Example of a coated magnetic recording medium)

[0023] (1) Configuration of magnetic recording medium First, with reference to Figure 1, the configuration of the magnetic recording medium 10 according to the first embodiment will be described. The magnetic recording medium 10 is, for example, a magnetic recording medium that has undergone vertical orientation processing. As shown in the figure, the magnetic recording medium 10 comprises a long base layer (also called a substrate) 11, an underlayment layer 12 provided on one main surface of the base layer 11, a magnetic layer (also called a recording layer) 13 provided on the underlayment layer 12, and a back layer 14 provided on the other main surface of the base layer 11. Hereinafter, of the two main surfaces of the magnetic recording medium 10, the surface on which the magnetic layer 13 is provided will be referred to as the magnetic surface, and the surface on the opposite side of the magnetic surface (the surface on which the back layer 14 is provided) will be referred to as the back surface.

[0024] The magnetic recording medium 10 has a long shape and is traveled in the longitudinal direction during recording and playback. The magnetic recording medium 10 may be configured to record signals at the shortest recording wavelength, 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, and can be used, for example, in a recording and playback device in which the shortest recording wavelength is within the above range. This recording and playback device may be equipped with a ring-type head as the recording head. The recording track width is, for example, 2 μm or less.

[0025] (2) Explanation of each layer

[0026] (Base layer)

[0027] The base layer 11 can function as a support for the magnetic recording medium 10, and may be, for example, a flexible, elongated nonmagnetic substrate, and in particular, a nonmagnetic film. The average thickness t of the base layer 11 Base For example, the average thickness t of the base layer 11 is 4.5 μm or less, preferably 4.2 μm or less, more preferably 4.0 μm or less, 3.8 μm or less, or 3.6 μm or less, and even more preferably 3.4 μm or less, 3.2 μm or less, or 3.0 μm or less. Base The lower limit may be determined, for example, from the viewpoint of the limitations in film formation or the function of the base layer 11, and may be, for example, 2.0 μm or more, 2.2 μm or more, 2.4 μm or more, or 2.6 μm or more. The base layer 11 may include at least one of the following: polyester resins, polyolefin resins, cellulose derivatives, vinyl resins, aromatic polyetherketone resins, and other polymer resins. If the base layer 11 includes two or more of the above materials, those two or more materials may be mixed, copolymerized, or laminated.

[0028] The polyester resin may be, for example, one or more of the following: PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PBN (polybutylene naphthalate), PCT (polycyclohexylene dimethylene terephthalate), PEB (polyethylene-p-oxybenzoate), and polyethylene bisphenoxycarboxylate.

[0029] The polyolefin resin may be, for example, one or more of PE (polyethylene) and PP (polypropylene).

[0030] The cellulose derivative may be, for example, one or a mixture of two or more of cellulose diacetate, cellulose triacetate, CAB (cellulose acetate butyrate), and CAP (cellulose acetate propionate).

[0031] The vinyl resin may be, for example, one or more of PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride).

[0032] The aromatic polyetherketone resin may be, for example, one or more of PEK (polyetherketone), PEEK (polyetheretherketone), PEKK (polyetherketoneketone), and PEEKK (polyetheretherketoneketone). According to a preferred embodiment of this technology, the base layer 11 may be formed from an aromatic polyetherketone resin, for example, from PEEK. The aromatic polyetherketone resin allows for easy adjustment of the average value of the loss modulus to the numerical range described later.

[0033] The aforementioned other polymer resins may be one or more of the following: PA (polyamide, nylon), aromatic PA (aromatic polyamide, aramid), PI (polyimide), aromatic PI (aromatic polyimide), PAI (polyamide-imide), aromatic PAI (aromatic polyamide-imide), PBO (polybenzoxazole, e.g., Zylon®), polyether, polyether ester, PES (polyethersulfone), PEI (polyetherimide), PSF (polysulfone), PPS (polyphenylene sulfide), PC (polycarbonate), PAR (polyarylate), and PU (polyurethane).

[0034] (magnetic layer)

[0035] The magnetic layer 13 may be, for example, a vertical recording layer. The magnetic layer 13 contains magnetic powder. The magnetic layer 13 may further contain a binder. The magnetic layer 13 may further contain non-magnetic particles. The magnetic layer 13 may further contain additives as needed, such as lubricants and rust inhibitors.

[0036] Average thickness t of magnetic layer 13 mThe average thickness of the magnetic layer t is preferably 80 nm or less, more preferably 70 nm or less, even more preferably 60 nm or less, 50 nm or less, and even more preferably 40 nm or less. m The lower limit is not particularly limited, but is preferably 30 nm or more. Average thickness t of the magnetic layer 13 m Having the above numerical range contributes to improving electromagnetic conversion characteristics.

[0037] The magnetic layer 13 is preferably a vertically oriented magnetic layer. In this specification, vertical orientation means that the angular ratio S1 measured in the longitudinal direction (travel direction) of the magnetic recording medium 10 is 35% or less. The magnetic layer 13 may be a magnetic layer oriented in-plane (longitudinally). In other words, the magnetic recording medium 10 may be a horizontal recording type magnetic recording medium. However, in terms of achieving high recording density, vertical orientation is more preferable.

[0038] (magnetic powder)

[0039] Examples of magnetic particles that make up the magnetic powder contained in the magnetic layer 13 include, but are not limited to, hexagonal ferrite, epsilon-type iron oxide (ε-iron oxide), Co-containing spinel ferrite, gamma hematite, magnetite, chromium dioxide, cobalt-coated iron oxide, and metal. The magnetic powder may be one of these, or a combination of two or more. Preferably, the magnetic powder may include hexagonal ferrite, ε-iron oxide, or Co-containing spinel ferrite. Particularly preferably, the magnetic powder is hexagonal ferrite. The hexagonal ferrite may particularly preferably contain at least one of Ba and Sr. The ε-iron oxide may particularly preferably contain 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 function of the tape.

[0040] The shape of magnetic particles depends on their crystal structure. For example, barium ferrite (BaFe) and strontium ferrite can be hexagonal plate-shaped. ε-iron oxide can be spherical. Cobalt ferrite can be cubic. Metals can be spindle-shaped. These magnetic particles are oriented during the manufacturing process of the magnetic recording medium 10.

[0041] 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 above average particle size may be, for example, 10 nm or more, preferably 12 nm or more.

[0042] 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.

[0043] (An embodiment containing hexagonal ferrite in magnetic powder)

[0044] In a preferred embodiment of this technology, the magnetic powder may include hexagonal ferrite, and more particularly, powder of nanoparticles containing hexagonal ferrite (hereinafter referred to as "hexagonal ferrite particles"). The hexagonal ferrite is preferably hexagonal ferrite having an M-type structure. The hexagonal ferrite may, for example, have a hexagonal plate-like or substantially hexagonal plate-like shape. The hexagonal ferrite may preferably contain 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 one or more combinations selected from, for example, barium ferrite, strontium ferrite, and calcium ferrite, and particularly preferably barium ferrite or strontium ferrite. In addition to Ba, barium ferrite may further contain at least one of Sr, Pb, and Ca. In addition to Sr, strontium ferrite may further contain at least one of Ba, Pb, and Ca.

[0045] More specifically, hexagonal ferrite has the general formula MFe 12 O 19 It may have an average composition represented by the following: Here, M is at least one metal from among Ba, Sr, Pb, and Ca, preferably at least one metal from among 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. Alternatively, M may 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, a portion of Fe may be substituted with other metallic elements.

[0046] When the magnetic powder contains hexagonal ferrite particle powder, 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 above 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 above average particle size of the magnetic powder may be 10 nm or more and 50 nm or less, 10 nm or more and 40 nm or less, 12 nm or more and 30 nm or less, 12 nm or more and 25 nm or less, or 15 nm or more and 22 nm or less. When the average particle size of the magnetic powder is less than or equal to the above upper limit (for example, 50 nm or less, particularly 30 nm or less), good electromagnetic conversion characteristics (e.g., SNR) can be obtained in the magnetic recording medium 10 with high recording density. When the average particle size of the magnetic powder is greater than or equal to the lower limit mentioned above (for example, 10 nm or more, preferably 12 nm or more), the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0047] When the magnetic powder contains hexagonal ferrite particle powder, 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. By having the average aspect ratio of the magnetic powder within the above numerical range, aggregation of the magnetic powder can be suppressed, and furthermore, the resistance applied to the magnetic powder when vertically oriented the magnetic powder in the magnetic layer 13 formation process can be suppressed. This can lead to an improvement in the vertical orientation of the magnetic powder.

[0048] When the magnetic powder contains hexagonal ferrite particle powder, the average particle size and average aspect ratio of the magnetic powder are determined as follows. First, the magnetic recording medium (hereinafter also referred to as "magnetic tape") housed in the magnetic recording cartridge is unwound, and a section of the magnetic tape to be measured is cut out to a length of approximately 50 mm. The cutting position may be, for example, 30 m in the longitudinal direction from the connection point 221 between the magnetic tape T (magnetic recording medium 10) and the leader tape LT in the case of the magnetic recording cartridge 10A shown in Figure 2, which will be described later. Next, the magnetic tape to be measured is processed and thinned using the FIB method or the like. When using the FIB method, a carbon layer and a tungsten layer are formed as protective films as a pretreatment before observing the TEM image of the cross-section, which will be described later. The carbon layer is formed on the magnetic layer side surface and the back layer side surface of the magnetic tape by vapor deposition, and the tungsten layer is further formed on the magnetic layer side surface by vapor deposition or sputtering. This thinning is performed along the length direction (longitudinal direction) of the magnetic tape. In other words, this thinning process creates a cross-section that is parallel to both the longitudinal and thickness directions of the magnetic tape.

[0049] The cross-section of the obtained thin section sample was examined using a transmission electron microscope (Hitachi High-Technologies Corporation H-9500) with an acceleration voltage of 200kV and a total magnification of 500,000x, focusing on the magnetic layer in the thickness direction. Cross-sectional observation is performed to include the entire material layer, and TEM images are taken. Prepare enough TEM images to extract 50 particles that can measure the plate diameter DB and plate thickness DA (see Figure 3A) shown below.

[0050] In this specification, the particle size of hexagonal ferrite (hereinafter referred to as "particle size") is defined as follows: If the shape of the particle observed in the TEM image above is plate-like or columnar (however, the thickness or height is smaller than the major axis of the plate surface or base), as shown in Figure 3A, the major axis of the plate surface or base is the value of the plate diameter DB. The thickness or height of the particle observed in the TEM image above is the value of the plate thickness DA. If the plate surface or base of the particle observed in the TEM image is hexagonal, the major axis means the longest diagonal distance. If the thickness or height of particles within a single particle is not constant, the thickness or height of the largest particle is defined as the plate thickness DA.

[0051] Next, 50 particles are selected from the captured TEM images based on the following criteria: Particles whose portion extends outside the field of view of the TEM image are not measured; only particles with clear outlines and existing in isolation are measured. If there is overlap between particles, those with clear boundaries and whose overall shape can be determined are measured as individual particles; however, particles with unclear boundaries and whose overall shape cannot be determined are not measured as their shape cannot be determined.

[0052] Figures 3B and 3C show examples of TEM images. In these figures, for example, the particles indicated by arrows a and d are selected because their particle thickness (thickness or height) DA can be clearly confirmed. The particle thickness DA of each of the 50 selected particles is measured. The average particle thickness DA obtained by simply averaging (arithmetic mean) these obtained particles is then calculated. ave We will find the average plate thickness DA. ave This is the average particle thickness. Next, the diameter DB of each magnetic powder is measured. To measure the particle diameter DB, 50 particles whose diameter DB can be clearly identified are selected from the TEM images taken. For example, in these figures, the particles indicated by arrows b and c are selected because their diameter DB can be clearly identified. The diameter DB of each of the 50 selected particles is measured. The average diameter DB obtained in this way is calculated by taking a simple average (arithmetic mean) of the resulting diameter DBs. aveWe will find the average plate diameter DB. ave However, this is the average particle size.

[0053] When the magnetic powder contains hexagonal ferrite particle powder, the average particle volume of the magnetic powder is preferably 1800 nm. 3 The following, more preferably 1600nm 3 The following, and more preferably 1400 nm 3 The following, and more preferably 1200nm 3 Below, 1100nm 3 The following, or 1000nm 3 The following may also be true: The average particle volume of the magnetic powder is preferably 500 nm. 3 Above, comfortable 700nm 3 That is all that is possible.

[0054] If the average particle volume of the magnetic powder is less than or equal to the above upper limit (for example, 2000 nm) 3 When the average particle volume of the magnetic powder is greater than or equal to the above lower limit (for example, 500 nm), good electromagnetic conversion characteristics (e.g., SNR) can be obtained in the high-recording-density magnetic recording medium 10. 3 (In the above cases) the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0055] The average particle volume of magnetic powder can be determined as follows. First, as described above regarding the method for calculating the average particle size of magnetic powder, the average plate thickness DA ave and average plate diameter DB ave Next, we calculate the average particle volume V of the magnetic powder using the following formula.

[0056]

number

[0057] In a particularly preferred embodiment of this technology, the magnetic powder may be barium ferrite magnetic powder or strontium ferrite magnetic powder, and more preferably barium ferrite magnetic powder. Barium ferrite magnetic powder contains magnetic particles of iron oxide with barium ferrite as the main phase (hereinafter referred to as "barium ferrite particles"). Barium ferrite magnetic powder offers high reliability in data recording, for example, by maintaining its coercivity even in high-temperature and high-humidity environments. From this viewpoint, barium ferrite magnetic powder is preferred as the magnetic powder.

[0058] The average particle size of the barium ferrite magnetic powder is 22 nm or less, more preferably 10 nm to 20 nm, and even more preferably 12 nm to 18 nm.

[0059] When the magnetic layer 13 contains barium ferrite magnetic powder as magnetic powder, the average thickness t of the magnetic layer 13 m [nm] is preferably 90 nm or less, and more preferably 80 nm or less. For example, the average thickness t of the magnetic layer 13. m This is defined as 35nm ≤ tm ≤ 90nm, or 35nm ≤ t m It is acceptable if it is ≤80nm.

[0060] Furthermore, the coercivity 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.

[0061] (An embodiment containing magnetic powder with ε-iron oxide)

[0062] In other preferred embodiments of this technology, the magnetic powder may preferably include powder of nanoparticles containing ε-iron oxide (hereinafter referred to as "ε-iron oxide particles"). The ε-iron oxide particles may have a composite particle structure. More specifically, the ε-iron oxide particles comprise an ε-iron oxide portion and a portion having soft magnetism or a portion having magnetism with a saturation magnetization σs higher than that of ε-iron oxide and a coercivity Hc lower (hereinafter referred to as "soft magnetic portion, etc.").

[0063] The ε-iron oxide portion contains ε-iron oxide. The ε-iron oxide contained in the ε-iron oxide portion is preferably composed mainly of ε-Fe2O3 crystals, and more preferably of a single phase of ε-Fe2O3.

[0064] The soft magnetic portion is in contact with the ε-iron oxide portion in at least part of it. Specifically, the soft magnetic portion may partially cover the ε-iron oxide portion, or it may cover the entire periphery of the ε-iron oxide portion.

[0065] The portion having soft magnetism (a portion having magnetism with a saturation magnetization σs higher than that of ε-iron oxide and a coercivity Hc lower) includes, for example, soft magnetic materials such as α-Fe, Ni-Fe alloy, or Fe-Si-Al alloy. α-Fe may be obtained by reducing the ε-iron oxide contained in the ε-iron oxide portion.

[0066] Furthermore, the soft magnetic portion may include, for example, Fe3O4, γ-Fe2O3, or spinel ferrite.

[0067] By having soft magnetic portions as described above, the ε-iron oxide particles can maintain a high coercivity Hc of the ε-iron oxide portion alone in order to ensure thermal stability, while adjusting the overall coercivity Hc of the ε-iron oxide particles (composite particles) to a coercivity Hc suitable for recording.

[0068] The ε-iron oxide particles may contain additives in place of the structure of the composite particles described above, or they may have the structure of the composite particles and also contain additives. In this case, a portion of the Fe in the ε-iron oxide particles is replaced by the additives. By including additives in the ε-iron oxide particles, the coercivity Hc of the ε-iron oxide particles as a whole can be adjusted to a coercivity Hc suitable for recording, thereby improving ease of recording. The additives are at least one selected from the group consisting of metal elements other than iron, preferably trivalent metal elements, more preferably Al, Ga, and In, and even more preferably at least one selected from the group consisting of Al and Ga.

[0069] Specifically, ε-iron oxide containing additives is ε-Fe 2-x M x O3 crystal (wherein M is a metallic element other than iron, preferably a trivalent metallic element, more preferably at least one selected from the group consisting of Al, Ga, and In, and even more preferably at least one selected from the group consisting of Al and Ga. x is, for example, 0 <x<1である。)である。

[0070] 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 with a size of half the recording wavelength. Therefore, by setting the average particle size of the magnetic powder to half or less of the shortest recording wavelength, a good SNR can be obtained. Accordingly, if 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 magnetic recording medium 10 with high recording density (for example, a magnetic recording medium 10 configured to record signals at the shortest recording wavelength of 44 nm or less). On the other hand, if the average particle size of the magnetic powder is 8 nm or more, the dispersibility of the magnetic powder is further improved, and even better electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0071] 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 1.0 to 2.5. When the average aspect ratio of the magnetic powder is within the above numerical range, aggregation of the magnetic powder can be suppressed, and the resistance applied to the magnetic powder when vertically oriented the magnetic powder in the magnetic layer 13 formation process can be suppressed. Therefore, the vertical orientation of the magnetic powder can be improved.

[0072] When the magnetic powder contains ε-iron oxide particles, the average particle size and average aspect ratio of the magnetic powder are determined as follows. First, the magnetic recording medium to be measured is cut out as described for the case where the magnetic powder contains hexagonal ferrite particle powder. The magnetic recording medium to be measured is processed and thinned using the FIB (Focused Ion Beam) method or the like. When using the FIB method, a carbon film and a tungsten film are formed as protective films as a pretreatment before observing the TEM image of the cross-section described later. The carbon film is formed on the magnetic layer side surface and the back layer side surface of the magnetic recording medium by vapor deposition, and the tungsten film is further formed on the magnetic layer side surface by vapor deposition or sputtering. Thinning is performed along the length direction (longitudinal direction) of the magnetic recording medium. That is, this thinning creates a cross-section parallel to both the longitudinal and thickness directions of the magnetic recording medium.

[0073] The cross-section of the obtained thin section sample is observed using a transmission electron microscope (Hitachi High-Technologies Corporation H-9500) with an acceleration voltage of 200kV and a total magnification of 500,000x, ensuring that the entire magnetic layer 13 is included in the thickness direction of the magnetic layer 13, and a TEM image is taken.

[0074] Next, 50 particles whose shape can be clearly observed are selected from the captured TEM images, and the major axis length DL and minor axis length DS of each particle are measured. Here, the major axis length DL refers to the maximum distance between two parallel lines drawn from any angle tangent to the contour of each particle (the so-called maximum Ferret diameter). On the other hand, the minor axis length DS refers to the maximum length of the particle in the direction perpendicular to the major axis (DL).

[0075] Next, the average major axis length DL of the 50 measured particles was simply averaged (arithmetic mean) to obtain the average major axis length DL. ave We calculate the average major axis length DL obtained in this way. ave This is defined as the average particle size of the magnetic powder. Additionally, the short-axis length DS of the 50 measured particles is simply averaged (arithmetic mean) to obtain the average short-axis length DS. ave We calculate the average major axis length DL.ave and average minor axis length DS ave From the average aspect ratio of the particles (DL ave / DS ave )

[0076] The average particle volume of the magnetic powder is preferably 1800 nm. 3 The following, more preferably 1600nm 3 The following, and more preferably 1400 nm 3 The following, and more preferably 1200nm 3 Below, 1100nm 3 The following, or 1000nm 3 The following may also be true: The average particle volume of the magnetic powder is preferably 500 nm. 3 Above, comfortable 700nm 3 That is all that is possible.

[0077] If the average particle volume of the magnetic powder is less than or equal to the above upper limit (for example, 2000 nm) 3 When the average particle volume of the magnetic powder is greater than or equal to the above lower limit (for example, 500 nm), good electromagnetic conversion characteristics (e.g., SNR) can be obtained in the high-recording-density magnetic recording medium 10. 3 (In the above cases) the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0078] If the ε-iron oxide particles are spherical or nearly spherical, the average particle volume of the magnetic powder can be determined as follows: First, the average major axis length DL is calculated using the same method as described above for calculating the average particle size of the magnetic powder. ave Next, we calculate the average particle volume V of the magnetic powder using the following formula. V = (π / 6) × DL ave 3

[0079] When the ε-iron oxide particles have a cubic shape, the average particle volume of the magnetic powder is determined as follows. The magnetic recording medium 10 is processed and thinned using the FIB (Focused Ion Beam) method or the like. When using the FIB method, a carbon film and a tungsten film are formed as protective films as a pretreatment before observing the TEM image of the cross-section described later. The carbon film is formed on the magnetic layer side surface and the back layer side surface of the magnetic recording medium 10 by vapor deposition, and the tungsten film is further formed on the magnetic layer side surface by vapor deposition or sputtering. This thinning is performed along the length direction (longitudinal direction) of the magnetic recording medium 10. That is, this thinning creates a cross-section parallel to both the longitudinal direction and the thickness direction of the magnetic recording medium 10.

[0080] The obtained thin section sample is subjected to cross-sectional observation using a transmission electron microscope (Hitachi High-Technologies Corporation H-9500) with an acceleration voltage of 200kV and a total magnification of 500,000x, ensuring that the entire magnetic layer 13 is included in the thickness direction of the magnetic layer 13, and a TEM image is obtained. The magnification and acceleration voltage may be adjusted as appropriate depending on the type of instrument.

[0081] Next, 50 particles whose shape is clear from the captured TEM images are selected, and the side length DC of each particle is measured. Then, the average side length DC of the 50 measured particles is simply averaged (arithmetic mean) to obtain the average side length DC. ave Next, we calculate the average side length DC. ave Using the following formula, the average particle volume V of the magnetic powder can be derived. ave Calculate the particle volume. V ave =DC ave 3

[0082] The coercivity Hc of the ε-iron oxide particles is preferably 2500 Oe or more, and more preferably 2800 Oe or more and 4200 e or less.

[0083] (An embodiment in which magnetic powder contains Co-containing spinel ferrite)

[0084] In yet another preferred embodiment of this technology, the magnetic powder may include 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 substantially cubic shape. The Co-containing spinel ferrite may further contain one or more elements selected from the group consisting of Ni, Mn, Al, Cu, and Zn, in addition to Co.

[0085] Cobalt ferrite has an average composition that can be expressed, for example, by the following formula. Co x M y Fe2O z (However, in the above formula, M is one or more metals selected from the group consisting of, for example, Ni, Mn, Al, Cu, and Zn. x is a value in the range of 0.4 ≤ x ≤ 1.0. y is a value in the range of 0 ≤ y ≤ 0.3. However, x and y satisfy the relationship (x + y) ≤ 1.0. z is a value in the range of 3 ≤ z ≤ 4. Part of Fe may be substituted with other metallic elements.)

[0086] The average particle size of the cobalt ferrite magnetic powder is preferably 21 nm or less, more preferably 19 nm or less. The coercivity Hc of the cobalt ferrite magnetic powder is preferably 2500 Oe or more, more preferably 2600 Oe or more and 3500 Oe or less.

[0087] When the magnetic powder contains cobalt ferrite particle powder, the average particle size of the magnetic powder is preferably 25 nm or less, more preferably 10 nm to 19 nm. Such a small average particle size of the magnetic powder allows for good electromagnetic conversion characteristics (e.g., SNR) in a high-recording-density magnetic recording medium 10. On the other hand, if the average particle size of the magnetic powder is 10 nm or more, the dispersibility of the magnetic powder is further improved, resulting in even better electromagnetic conversion characteristics (e.g., SNR). When the magnetic powder contains cobalt ferrite particle powder, the average aspect ratio and average particle size of the magnetic powder are determined in the same way as when the magnetic powder contains ε-iron oxide particles.

[0088] The average particle volume of the magnetic powder is preferably 2000 nm. 3 The following, and more preferably 1900 nm 3 The following, and more preferably 1800 nm 3 The following, and more preferably 1700nm 3 Below, 1600nm 3 The following, or 1500nm 3 The following may also be true: The average particle volume of the magnetic powder is preferably 500 nm. 3 Above, comfortable 700nm 3 That is all that is possible.

[0089] If the average particle volume of the magnetic powder is less than or equal to the above upper limit (for example, 2000 nm) 3 When the average particle volume of the magnetic powder is greater than or equal to the above lower limit (for example, 500 nm), good electromagnetic conversion characteristics (e.g., SNR) can be obtained in the high-recording-density magnetic recording medium 10. 3 (In the above cases) the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0090] (Binder)

[0091] As a binder, a resin having a structure in which a crosslinking reaction has been imparted to a polyurethane resin or a vinyl chloride resin is preferred. 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 commonly used in coated magnetic recording media 10.

[0092] Examples of the aforementioned binders 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.

[0093] Furthermore, thermosetting resins or reactive resins may be used as the binder. Examples of these include phenolic resins, epoxy resins, urea resins, melamine resins, alkyd resins, silicone resins, polyamine resins, and urea-formaldehyde resins.

[0094] Furthermore, each of the above-mentioned binders may have polar functional groups such as -SO3M, -OSO3M, -COOM, and P=O(OM)2 introduced to improve the dispersibility of the magnetic powder. Here, M is a hydrogen atom or an alkali metal such as lithium, potassium, and sodium.

[0095] Furthermore, polar functional groups include -NR1R2 and -NR1R2R3. + X - Side chain type with terminal group >NR1R2 + X - Examples include the main chain type. Here, R1, R2, and R3 are hydrogen atoms or hydrocarbon groups, and X - These are halogen element ions such as fluorine, chlorine, bromine, or iodine, or inorganic or organic ions. Polar functional groups also include -OH, -SH, -CN, and epoxy groups.

[0096] (Lubricant)

[0097] The magnetic layer may contain a lubricant. The lubricant may be, for example, one or more selected from fatty acids and / or fatty acid esters, and preferably may contain both fatty acids and fatty acid esters. The fatty acid may preferably be a compound represented by the following general chemical formula (1) or general chemical formula (2). For example, the fatty acid may contain either a compound represented by the following general chemical formula (1) and a compound represented by general chemical formula (2), or both. Furthermore, the fatty acid ester may preferably be a compound represented by the following general chemical formula (3), a compound represented by the general chemical formula (4), or a compound represented by the general chemical formula (5). For example, the fatty acid ester may contain one, two, or all three of the following compounds represented by the general chemical formula (3), the compound represented by the general chemical formula (4), and the compound represented by the general chemical formula (5). The lubricant contains either one or both of the compound represented by general chemical formula (1) and the compound represented by general chemical formula (2), and one, two, or three of the compounds represented by general chemical formula (3), general chemical formula (4), and general chemical formula (5), thereby suppressing the increase in the coefficient of dynamic friction due to repeated recording or playback on the magnetic recording medium.

[0098] CH3(CH2)k COOH ···(1) (However, in the general chemical 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.)

[0099] CH3(CH2) n CH=CH(CH2) m COOH ···(2) (However, in the general chemical 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.)

[0100] CH3(CH2) p COO(CH*) q CH3···(3) (However, in the general chemical formula (3), p 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, and q is an integer selected from the range of 2 or more and 5 or less, more preferably from the range of 2 or more and 4 or less.)

[0101] CH3(CH2) r COO-(CH2) s CH(CH3)2···(4) (However, in the general chemical formula (4), r is an integer selected from the range of 14 or more and 22 or less, and s is an integer selected from the range of 1 or more and 3 or less.)

[0102] CH3(CH2) t COO-(CH)(CH3)CH2(CH3) u ···(5) (However, in the general formula (5), t is an integer selected from the range of 14 or more and 22 or less, and u is an integer selected from the range of 1 or more and 3 or less.)

[0103] Note: There seems to be a small error in the original text where "COO(CH*)" in ID=19 should probably be "COO(CH2)". The translation has been made as accurately as possible based on the provided text.Examples of the lubricant include esters of monobasic fatty acids having 10 to 24 carbon atoms and monohydric to hexahydric alcohols having 2 to 12 carbon atoms, mixed esters thereof, difatty acid esters, trifatty acid esters, etc. 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, octyl myristate, etc. The magnetic layer may contain one or more of these.

[0104] The lubricant content may be, for example, 1 part by mass or more, preferably 2 parts by mass or more, per 100 parts by mass of magnetic powder. Alternatively, the content may be, for example, 10 parts by mass or less, preferably 8 parts by mass or less, and more preferably 6 parts by mass or less, per 100 parts by mass of magnetic powder.

[0105] (Additives)

[0106] The magnetic layer 13 may further contain non-magnetic reinforcing particles such as 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 type titanium oxide).

[0107] In one embodiment of this technology, the magnetic layer may contain conductive first particles and second particles having a Mohs hardness of 7 or higher. The first and second particles may form protrusions on the surface of the magnetic layer. For example, the first particles can prevent an increase in frictional force when the magnetic recording tape is running and can function as a solid lubricant component. The second particles can also provide an abrasive effect (and even an anchoring effect) for cleaning the magnetic head. By including these two components in the magnetic layer of the magnetic recording tape, it is conceivable that an increase in frictional force and cleaning of the magnetic head can be prevented, thereby improving the tape's running performance. By adjusting the type and / or content of the non-magnetic reinforcing particles, the average height Rpk of the protruding mountain portions described later can be adjusted.

[0108] The first particles have conductivity. As the first particles, fine particles mainly composed of carbon can be used. For example, they may preferably be carbon particles, and examples of such carbon particles include carbon black. As the carbon black, for example, Asahi #15 and #15HS of Asahi Carbon Co., Ltd. and Seast TA of Tokai Carbon Co., Ltd. can be used. Also, hybrid carbon in which carbon is adhered to the surface of silica particles may be used.

[0109] The average particle size (arithmetic mean value of the particle diameters measured using the electron microscopy method) of the first particles (particularly carbon particles, such as carbon black) may be, for example, 15 nm or more, preferably 30 nm or more, more preferably 50 nm or more. Also, the average particle size may be, for example, 200 nm or less, preferably 180 nm or less, more preferably 150 nm or less, 130 nm or less, or 120 nm or less. The numerical range of the average particle size may be appropriately selected from these upper and lower limit values, and may be, for example, from 50 nm to 200 nm, preferably from 50 nm to 180 nm, more preferably from 50 nm to 150 nm, and even more preferably from 50 nm to 130 nm. The nitrogen adsorption specific surface area of the first particles (particularly carbon particles, such as carbon black) is, for example, 5 m 2 / g to 50 m 2 / g, preferably 7 m 2 / g to 50 m 2 / g, more preferably 10 m 2 / g to 50 m 2 / g, even more preferably 12 m 2 / g to 50 m 2 / g. The amount of iodine adsorbed by the first particles (particularly carbon particles, such as carbon black) may be, for example, 5 mg / g to 50 mg / g, preferably 7 mg / g to 50 mg / g, more preferably 10 mg / g to 50 mg / g, and even more preferably 12 mg / g to 50 mg / g.

[0110] The second particle may have a Mohs hardness of 7 or higher, preferably 7.5 or higher, more preferably 8 or higher, and even more preferably 8.5 or higher, from the viewpoint of suppressing deformation due to contact with the magnetic head. From the viewpoint of suppressing head wear, the Mohs hardness of the second particle may be, for example, 10 or lower, preferably 9.5 or lower. That is, the second particle may be formed from a material having such a Mohs hardness. The second particles may preferably be inorganic particles. The second particles may be, for example, α-alumina (with an α-gelatinization rate of, for example, 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, needle-shaped α-iron oxide obtained by dehydrating and annealing the raw materials of magnetic iron oxide, or surface-treated with aluminum and / or silica as necessary, or diamond powder, or a combination of two or more of these. The second particles may preferably be alumina particles such as α-alumina, β-alumina, γ-alumina, or silicon carbide. These second particles may be needle-shaped, spherical, cube-shaped, etc., but those with corners in part of their shape are preferred because, for example, they have high abrasiveness.

[0111] The average particle size of the second particles (particularly inorganic particles, such as alumina) (for example, the arithmetic mean of particle diameters measured using electron microscopy) may be, for example, 15 nm or more, preferably 30 nm or more, and more preferably 50 nm or more. Alternatively, the average particle size may be, for example, 200 nm or less, preferably 180 nm or less, more preferably 150 nm or less, 130 nm or less, or 120 nm or less. The numerical range of the average particle size may be appropriately selected from these upper and lower limits, for example, 50 nm to 180 nm, preferably 60 nm to 150 nm, and more preferably 60 nm to 120 nm. The second particle (particularly an inorganic particle, such as alumina) may not be conductive. That is, the second particle may not have the same conductivity as the first particle.

[0112] (base layer)

[0113] The base layer 12 is a non-magnetic layer mainly composed of non-magnetic powder and a binder. The base layer 12 may further contain at least one additive, as needed, such as other particles, lubricants, hardeners, and rust inhibitors.

[0114] The average thickness of the underlayer 12 is preferably 1200 nm or less, preferably 1150 nm or less, 1120 nm or less, 1100 nm or less, more preferably 1000 nm or less, 900 nm or less, or 800 nm or less, or 700 nm or less, and even more preferably 600 nm or less. The lower limit of the average thickness of the underlayer is not particularly limited, but is preferably 200 nm or more, and more preferably 300 nm or more.

[0115] (Non-magnetic powder)

[0116] The non-magnetic powder contained in the base layer 12 includes, for example, at least one selected from inorganic particles and organic particles, and more particularly, at least one selected from inorganic particles. One type of non-magnetic powder may be used alone, or two or more types of non-magnetic powder may be used in combination. The non-magnetic inorganic particles may be, for example, one or a combination of two or more selected from metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. More specifically, the inorganic particles may be, for example, one or two or more selected from iron oxide, aluminum oxide, carbon black, iron oxyhydroxide, hematite, titanium oxide, silicon oxide, titanium carbide, silicon carbide, diamond, and calcium carbonate. Examples of the shape of the non-magnetic powder include needle-shaped, spherical, cubic, and plate-shaped shapes, but are not particularly limited to these.

[0117] (Binder)

[0118] The aforementioned underlayer contains a binder. The description of the binder contained in the magnetic layer 13 above also applies to the binder contained in the underlayer 12.

[0119] (Lubricant)

[0120] The aforementioned underlayer may contain a lubricant. The lubricant may be, for example, one or more selected from fatty acids and / or fatty acid esters, and the lubricant may preferably be a compound represented by general chemical formula (1) or general chemical formula (2), or general chemical formula (3) or general chemical formula (4) as described above with respect to the magnetic layer. One or more of these compounds may be included.

[0121] Examples of the lubricant include esters of monobasic fatty acids having 10 to 24 carbon atoms and monohydric to hexahydric alcohols having 2 to 12 carbon atoms, mixed esters thereof, difatty acid esters, trifatty acid esters, etc. 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, octyl myristate, etc. The magnetic layer may contain one or more of these.

[0122] (Back layer)

[0123] The back layer 14 may contain a binder and non-magnetic powder. The back layer 14 may also contain various additives such as lubricants, hardeners, and antistatic agents as needed. The description of the binder and non-magnetic powder contained in the non-magnetic layer 12 above also applies to the binder and non-magnetic powder contained in the back layer 14.

[0124] The average particle size of the inorganic particles contained in the back layer 14 is preferably 10 nm to 150 nm, more preferably 15 nm to 110 nm. The average particle size of the inorganic particles is determined in the same manner as the average particle size D of the magnetic powder described above.

[0125] Average thickness t of back layer 14 b The average thickness t of the back layer 14 is preferably 0.6 μm or less, more preferably 0.5 μm or less, even more preferably 0.4 μm or less, 0.3 μm or less, 0.25 μm or less, or 0.2 μm or less. b As long as it is within the above range, the average thickness (average total thickness) t of the magnetic recording medium 10 T to TEven when the thickness is set to ≤5.7 μm, the average thickness of the non-magnetic layer 12 and the base layer 11 can be kept thick, thereby maintaining the stability of the magnetic recording medium 10 during operation within the recording and playback device. Furthermore, the lower limit of the average thickness of the back layer is not particularly limited, but can be, for example, 0.1 μm or more, preferably 0.15 μm or more.

[0126] (3) Physical properties and structure

[0127] (Various values ​​measured by dynamic viscoelasticity measurement)

[0128] Average value A of the loss modulus E'' in the temperature range of 60°C to 65°C (E”) , the average value A of the storage modulus E' in the said temperature range (E’) , and the average value A of Tanδ (loss modulus E'' / storage modulus E') in the said temperature range. (Tanδ) These are all measured by performing dynamic viscoelasticity measurements on magnetic recording media.

[0129] In this technology, the average value A of the loss modulus E'' in the temperature range of 60°C to 65°C. (E”) The average value A of the loss modulus E'' is preferably 0.06 GPa or less, preferably 0.05 GPa or less, more preferably 0.04 GPa or less, and even more preferably 0.03 GPa or less. (E”) It is preferable for the above numerical range to be within the specified range in order to improve the storage stability of the magnetic recording medium in high-temperature environments and the running stability after storage in high-temperature environments. Furthermore, the average value A of the loss modulus E'' (E”) For example, it may be 0 GPa or higher, and more specifically, 0.001 GPa or higher, 0.005 GPa or higher, or 0.01 GPa or higher.

[0130] In this technology, the average value A of the storage modulus E' in the temperature range of 60°C to 65°C. (E’)For example, it is 6 GPa or less, more preferably 5 GPa or less, even more preferably 4 GPa or less, and particularly preferably 3.5 GPa or less, 3.2 GPa or less, 3.0 GPa or less, or 2.8 GPa or less. The average value A of the storage modulus E'. (E’) It is also preferable that the values ​​fall within the above range for improving the storage stability of the magnetic recording medium in high-temperature environments and the running stability after storage in high-temperature environments. Furthermore, the average value of the storage modulus E' is, for example, 0.1 GPa or higher, and may be particularly 0.2 GPa or higher, 0.5 GPa or higher, or 1.0 GPa or higher.

[0131] In this technology, the average value A of Tanδ (loss modulus E'' / storage modulus E') in the temperature range of 60°C to 65°C (Tanδ) For example, it is 0.017 or less, more preferably 0.016 or less, even more preferably 0.015 or less, and particularly preferably 0.014 or less. The average value A of Tanδ (Tanδ) It is also preferable that the values ​​fall within the above range for improving the storage stability of the magnetic recording medium in high-temperature environments and the running stability after storage in high-temperature environments. Furthermore, the average value A of Tanδ (Tanδ) For example, it may be 0.001 or greater, and more particularly 0.002 or greater, or 0.005 or greater.

[0132] Average value A of the loss modulus E'' in the temperature range of 60°C to 65°C (E”) , the average value A of the storage modulus E' in the said temperature range (E’) , and the average value A of Tanδ in the said temperature range (Tanδ) This is measured by dynamic viscoelasticity measurement. The dynamic viscoelasticity measurement is a temperature-dependent measurement and is specifically performed as follows.

[0133] The magnetic tape T housed in the magnetic recording cartridge 10A is unwound, and samples measuring 22.0 mm in length along the length of the tape and 4.0 mm in width along the width of the tape are cut at three locations: 20 m, 40 m, and 60 m from the connection point between the magnetic tape T and the leader tape LT. For each of these three samples, dynamic viscoelasticity measurements, as detailed below, are performed to determine the average value A of the loss modulus E'' in the temperature range of 60°C to 65°C. (E”20) , A (E”40) , and A (E”60) Obtain the average value A. (E”20) , A (E”40) , and A (E”60) These are the measurements for samples taken at distances of 20m, 40m, and 60m, respectively. And the average value A (E”20) , A (E”40) , and A (E”60) The simple average of the values ​​is the average value A of the loss modulus E'' in this technology. (E”) That is the case. The storage modulus E' is also measured by dynamic viscoelasticity measurement, which measures the loss modulus E''. Therefore, by performing this dynamic viscoelasticity measurement for each of the three samples, the average value A of the storage modulus E' can be determined. (E’20) , A (E’40) , and A (E’60) We obtain the following values. Then, the average value A (E’20) , A (E’40) , and A (E’60) The simple average of the values ​​is the average value A of the storage modulus E' in this technology. (E’) That is the case. The Tanδ is also measured by dynamic viscoelasticity measurement, which measures the loss modulus E''. Therefore, by performing this dynamic viscoelasticity measurement for each of the three samples, the average value of Tanδ A can be calculated. (Tanδ20) , A (Tanδ40) , and A (Tanδ60) We obtain the following values. Then, the average of the three values ​​A (Tanδ20) , A (Tanδ40) , and A (Tanδ60) The simple average of the values ​​is the average value of Tanδ A in this technology. (Tanδ) That is the case.

[0134] First, both longitudinal ends of the sample are clamped to the measurement section of the dynamic viscoelasticity measuring device (RSA II (RSA-SL-OPT), manufactured by TA Instruments). Then, dynamic viscoelasticity measurement is performed under the following measurement conditions. <Measurement conditions> Measurement temperature range: -10℃ to 180℃ Heating rate: 2°C / min Amplitude: The tape is stretched and compressed by an amplitude of 0.1% relative to its initial length. Measurement frequency: 10Hz Test Type: “Strain-Controlled” Measurement Type: "Dynamic" Environment in which the device is placed: Temperature 25°C, Humidity 50RH Humidity control at the measurement unit: None More detailed settings regarding the measurement conditions of the above apparatus are as follows. Specifically, as described below, in the measurement, the tension is adjusted so that it does not fall below 0, and the strain is adjusted so that it does not fall below the lower limit of the transducer. The measurement conditions for these adjustments may be set appropriately by those skilled in the art, but for the above dynamic viscoelasticity measuring apparatus, for example, the following settings may be adopted. Option settings Delay Before Test: OFF Auto Tension (a setting to adjust tension so that it never goes below 0): Mode Static Force Tracking Dynamic Force Auto Tension Direction Tension Initial Static Force 10.0g Static > Dynamic Force by 5.0% Minimum Static Force 1.0g Auto Tension Sensitivity 1.0g Auto Strain (a setting to adjust so that the strain does not fall below the transducer's lower limit): Max Applied Strain 0.1% Maximum Allowed Force: 100.0g Minimum allowed force 2.0g Strain Adjustment 3.0% MeAs Ops: Default setting

[0135] By performing the dynamic viscoelasticity measurement described above, the loss modulus E'' at a measurement temperature of 60°C to 65°C is obtained, and by simply averaging the loss modulus E'' in that temperature range, the average value of the loss modulus E'' in that temperature range is obtained. Furthermore, by performing the dynamic viscoelasticity measurement, the storage modulus E' at a measurement temperature of 60°C to 65°C can be obtained, and by simply averaging the storage modulus E' in that temperature range, the average value of the storage modulus E' in that temperature range can be obtained. Furthermore, Tanδ is calculated from the loss modulus E'' and storage modulus E' obtained at each temperature by performing the dynamic viscoelasticity measurement described above. Then, by simply averaging the Tanδ values ​​at measurement temperatures of 60°C to 65°C, the average value of Tanδ in that temperature range is obtained.

[0136] These average values ​​can be adjusted, for example, by selecting the base layer material, by adjusting the longitudinal and / or transverse strength of the base layer material (by adjusting the longitudinal and / or transverse stretching conditions), or by adjusting the composition of the magnetic layer. For example, the aromatic polyether ketone resin mentioned above may be used as the base layer material, and PEEK may be used in particular. These average values ​​can also be adjusted by adjusting the temperature and / or time of a strain relief step before cutting or a strain relief step before servo writing, which are included in the manufacturing process of the magnetic recording medium. These strain relief steps may be performed at, for example, 40°C to 120°C for 10 seconds to 100 hours. These relief steps may be performed while the machine is moving or while the roll is stationary.

[0137] (Average height Rpk of the protruding peak) The magnetic recording medium according to this technology has an average height Rpk of the protruding peaks measured using a non-contact roughness meter employing optical interference, for example, 2.4 nm or less, preferably 2.3 nm or less, and more preferably 2.2 nm or less. Having the average height Rpk within the above numerical range is preferable for improving the storage stability of the magnetic recording medium in high-temperature environments and the running stability after storage in high-temperature environments. Furthermore, the average height Rpk is, for example, 0.5 nm or more, and may be particularly 1.0 nm or more, 1.2 nm or more, or 1.5 nm or more.

[0138] The average height Rpk of the protruding peaks can be adjusted by adjusting the composition of the magnetic layer and / or the dispersion treatment time in the manufacture of the coating for forming the magnetic layer. For example, the average height Rpk of the protruding peaks can be adjusted by adjusting the type, particle size, and content of particles (especially non-magnetic reinforcing particles) contained in the magnetic layer. Furthermore, the average height Rpk of the protruding peaks can also be adjusted by adjusting the surface properties of the base layer and / or the substrate layer. With respect to the substrate layer, for example, the surface properties of the substrate layer can be adjusted by adjusting the amount of particles (e.g., carbon particles) and / or the dispersion treatment time in the manufacture of the substrate-forming coating. For example, the average height Rpk can be reduced by reducing the surface roughness of these layers.

[0139] The average height Rpk of the protruding peaks is measured using a non-contact roughness meter employing optical interference. In this measurement, a bearing curve is created by software attached to the non-contact roughness meter. The bearing curve is used to evaluate the characteristics of a surface subjected to strong mechanical contact. The bearing curve allows the surface irregularities to be divided into three parts: protruding peaks, core parts, and protruding valleys. Of these three, the protruding peaks correspond to the parts of the surface irregularities that are considered to be relatively prone to wear. By adjusting the average height Rpk of the protruding peaks on the magnetic layer side surface as described above, the running stability after storage in a high-temperature environment can be improved. Furthermore, this can also result in good electromagnetic conversion characteristics.

[0140] The following describes the method for measuring the average height Rpk of the protruding peak. Furthermore, in calculating the average height Rpk of the protruding peaks, the magnetic tape T housed in the magnetic recording cartridge 10A is unwound, and samples are cut at three locations: 20m, 40m, and 60m from the connection point between the magnetic tape T and the leader tape LT. These three samples are then used. For each of these three sample locations, the average height of the protruding peaks is calculated as detailed below, and Rpk is obtained. (20) Rpk (40) , and Rpk (60) Obtain Rpk. (20) Rpk (40) , and Rpk (60) The simple average of these values ​​is the average height Rpk of the protruding peaks in this technology.

[0141] The average height Rpk of the protruding peaks of the magnetic layer is measured as follows. First, a 12.65 mm wide magnetic tape T is prepared and cut to a length of 100 mm to create a sample. Next, the sample is placed on a microscope slide with the surface to be measured (the surface on the magnetic layer side) facing upwards, and the edges of the sample are secured with mending tape. A non-contact roughness meter using optical interference (VertScan, 50x objective lens) is used to measure the surface shape of the surface to be measured, and a bearing curve is drawn using the attached analysis software to determine the average height Rpk of the protruding peaks. The measurement conditions are as follows: Device: Non-contact roughness tester using optical interference (VertScan R5500GL-M100-AC, a non-contact surface and layer cross-sectional shape measurement system manufactured by Ryoka Systems Co., Ltd.) Objective lens: 50x CCD: 1 / 3 lens Measurement area: 640 x 480 pixels (Field of view: approximately 95 μm x 71 μm) Measurement mode: phase Wavelength filter: 520nm Noise reduction filter, smoothing 3x3 Surface correction: Correction using a quadratic polynomial approximation surface. Measurement software: VS-Measure Version 5.5.2 Analysis software: VS-viewer Version 5.5.5

[0142] As described above, the surface shape of the magnetic layer side of the sample is measured at at least five points along its longitudinal direction. Then, the average of the average heights Rpk of each protruding peak, automatically calculated from the bearing curves obtained at each position, is defined as the average height Rpk of the protruding peaks of the sample. The simple average of the average heights of the protruding peaks obtained for each sample at the three locations described above is the average height Rpk of the protruding peaks in this technology.

[0143] (Variable change after 40 hours)

[0144] A magnetic recording medium conforming to this technology exhibits a width variation ΔW when subjected to a load of 0.55 N in the longitudinal direction for 40 hours under conditions of 65°C and 40% humidity. 40h However, for example, -600 ppm ≤ ΔW 40h Preferably, -500 ppm ≤ ΔW 40h And more preferably, -400 ppm ≤ ΔW 40h Furthermore, more preferably -300 ppm ≤ ΔW 40h -250 ppm ≤ ΔW 40h , or -200 ppm ≤ ΔW 40h That's fine. Width variation ΔW 40h Regarding the upper limit, for example, ΔW 40h It is acceptable that ≤ 0, and in particular ΔW 40h ≤ -10, ΔW 40h ≤ -50, or ΔW 40h It is acceptable for the value to be ≤ -100. Width variation ΔW of magnetic recording medium 40h As a result of the control described above, the magnetic recording medium exhibits excellent storage stability in high-temperature environments.

[0145] Width variation ΔW 40h The measurement is performed as follows: First, a 1 / 2-inch wide magnetic recording medium 10 is prepared, and then cut to a length of 250 mm to create sample 10S. Sample 10S is obtained by unwinding the magnetic tape T housed in the magnetic recording cartridge 10A and cutting it at three locations: 20m, 40m, and 60m from the connection point between the magnetic tape T and the leader tape LT. For each of the three obtained samples, measurements are taken as follows to determine the three width variations ΔW. 40h(20) ΔW 40h(40) , and ΔW 40h(60) We obtain these three width variations ΔW 40h(20) ΔW 40h(40) , and ΔW 40h(60) The simple average of the width variation ΔW in this technology is 40h That is the case.

[0146] A measuring device, as shown in Figure 4, incorporating a Keyence LS-7000 digital dimension measuring instrument, is prepared, and the sample 10S is set in this measuring device. Specifically, one end of the elongated sample (magnetic recording medium) 10S is fixed by the fixing part 231. Next, as shown in Figure 4, the sample 10S is placed on five roughly cylindrical and rod-shaped support members 232. The sample 10S is placed on these support members so that its back surface is in contact with the five support members 232. All five support members 232 (especially their surfaces) are made of stainless steel SUS304, and their surface roughness R z The maximum height is 0.15 μm to 0.3 μm.

[0147] Furthermore, of the five support members 232, the third support member is fixed so as not to rotate, but the other four support members are all rotatable. The arrangement of the five rod-shaped support members 232 will be described while referring to FIG. 5. As shown in FIG. 5, the sample 10S is placed on the five support members 232. Regarding the five support members 232, hereinafter, starting from the one closest to the fixing portion 231, they are referred to as the "first support member", "second support member", "third support member" (having the slit 232A), "fourth support member", and "fifth support member" (closest to the weight 233). The diameter of these five support members is 7 mm. The distance d1 between the first support member and the second support member (specifically, the distance between the centers of these support members) is 20 mm. The distance d2 between the second support member and the third support member is 30 mm. The distance d3 between the third support member and the fourth support member is 30 mm. The distance d4 between the fourth support member and the fifth support member is 20 mm. Also, these three support members are arranged such that the portion of the sample 10S that lies between the second support member, the third support member, and the fourth support member forms a plane substantially perpendicular to the direction of gravity. Also, the first support member and the second support member are arranged such that the sample 10S forms an angle of θ1 = 30° with respect to the substantially perpendicular plane between the first support member and the second support member. Further, the fourth support member and the fifth support member are arranged such that the sample 10S forms an angle of θ2 = 30° with respect to the substantially perpendicular plane between the fourth support member and the fifth support member. Also, among the five support members 232, the third support member is fixed so as not to rotate, while the other four support members are all rotatable.

[0148] The sample 10S is held on the support member 232 so as not to move in the width direction of the sample 10S. Among the support members 232, a slit 232A is provided in the support member 232 that is located between the light emitter 234 and the light receiver 235 and is positioned approximately at the center between the fixing portion 231 and the portion applying the load. Light L is irradiated from the light emitter 234 to the light receiver 235 through the slit 232A. The slit width of the slit 232A is 1 mm, and the light L can pass through this width without being blocked by the frame of the slit 232A.

[0149] Subsequently, after the measuring device is housed in a chamber controlled under a constant environment of a temperature of 65°C and a relative humidity of 40%, a weight 233 for applying a load of 0.55 N is attached to the other end of the sample 10S. That is, the sample 10S is in a state where the sample 10S is longitudinally pulled with a load of 0.55 N. In this state, the sample 10S is placed in the above environment for 40 hours. Within the 40 hours in the above environment, the width of the sample 10S is measured every hour. With a load applied, light L is irradiated from the light emitter 234 toward the light receiver 235, and the width of the sample 10S with a load applied longitudinally is measured. The measurement of the width is performed in a state where the sample 10S is not curled. The light emitter 234 and the light receiver 235 are those provided in the digital dimension measuring instrument LS-7000. The difference between the width measured first (the width after 1 hour from when the load is applied) and the width measured last (the width when measured after 40 hours) is defined as the width fluctuation amount. That is, the width fluctuation amount is represented by the following formula. "Width fluctuation amount" = "Width when measured after 40 hours" - "Width after 1 hour from when the load is applied" And this width fluctuation amount is obtained for three samples obtained from three different positions as described above. And the simple average value of the three width fluctuation amounts is the width fluctuation amount ΔW according to the present technology 40h is.

[0150] (Stiffness S) The stiffness S of the magnetic recording medium according to the present technology is, for example, 1.4 mgf / μm or less, preferably 1.3 mgf / μm or less, 1.2 mgf / μm or less, 1.1 mgf / μm or less, or 1.0 mgf / μm or less, more preferably 0.9 mgf / μm or less, and even more preferably 0.8 mgf / μm or less. Having the stiffness S described above contributes to an improvement in the running stability after the magnetic recording medium is stored in a high-temperature environment. The lower limit of the stiffness S of the magnetic recording medium according to this technology is not particularly limited, but may be, for example, 0.1 mgf / μm or more, and more particularly 0.2 mgf / μm or more, 0.3 mgf / μm or more, 0.4 mgf / μm or more, or 0.5 mgf / μm or more.

[0151] The method for measuring stiffness S is described below. The magnetic tape T housed in the magnetic recording cartridge 10 is unwound, and samples are cut out at three locations: 20m, 40m, and 60m from the connection point between the magnetic tape T and the leader tape LT. The flexural rigidity of each of the three samples is measured according to ECMA-319. The arithmetic mean of the three obtained flexural rigidity values ​​is the stiffness S in this technique.

[0152] (Average thickness of magnetic recording medium (average total thickness) t) T )

[0153] The average thickness (average total thickness) of the magnetic recording medium 10 is t. T The average thickness t of the magnetic recording medium 10 may be, for example, 5.7 μm or less, preferably 5.6 μm or less, more preferably 5.5 μm or less, 5.4 μm or less, 5.3 μm or less, 5.2 μm or less, 5.1 μm or less, or 5.0 μm or less, and even more preferably 4.6 μm or less or 4.4 μm or less. T If the average thickness of the magnetic recording medium 10 is 5.5 μm or less, the recording capacity that can be recorded in one data cartridge can be increased compared to general magnetic tape. T The lower limit is not particularly restricted, but for example, it is 3.5 μm or larger.

[0154] The average thickness t of the magnetic recording medium 10 (also referred to as magnetic tape T in this specification) T The average thickness t can be calculated as follows. T is, total thickness t T It is also called [another name]. First, the magnetic tape T housed in a cartridge such as cartridge 10A (described later) is unwound, and three 250mm lengths of magnetic tape T are cut at 20m, 40m, and 60m in the longitudinal direction from the connection point 221 between the magnetic tape T and the leader tape LT, thereby creating three samples. Next, using a Mitutoyo laser hologage (LGH-110C) as a measuring device, the thickness of each sample is measured at five points, and these measurements are simply averaged (arithmetic mean) to obtain the average thickness t. T20 , t T40 , and t T60 The following is calculated. The five measurement points mentioned above will be randomly selected from the sample so that they are all at different locations along the longitudinal direction of the magnetic tape T. Average thickness t T20 , t T40 , and t T60 The arithmetic mean of is the average thickness t of the magnetic recording medium in this technology. T That is the case.

[0155] (Average thickness of the underlying layer (non-magnetic layer))

[0156] The average thickness of the base layer 12 is determined as follows. First, the magnetic tape T housed in a cartridge, such as the cartridge 10A described later, is unwound, and three samples are prepared by cutting the magnetic tape T to a length of 250 mm at three locations: 20 m, 40 m, and 60 m in the longitudinal direction from the connection point 221 between the magnetic tape T and the leader tape LT. Next, each sample is processed by FIB or the like to create thin sections. When using the FIB method, a carbon layer and a tungsten layer are formed as protective films as a pretreatment before observing the TEM image of the cross-section described later. The carbon layer is formed on the surface of the magnetic layer 13 side and the surface of the back layer 14 side of the magnetic tape T by vapor deposition, and the tungsten layer is further formed on the surface of the magnetic layer 13 side by vapor deposition or sputtering. This thinning is performed along the longitudinal direction of the magnetic tape T. That is, this thinning creates a cross-section parallel to both the longitudinal and thickness directions of the magnetic tape T.

[0157] The cross-sections of each obtained thinned sample are observed using a transmission electron microscope (TEM) under the following conditions. Equipment: TEM (Hitachi H9000NAR) Acceleration voltage: 300kV Magnification: 100,000x Next, using the obtained TEM image, the thickness of the underlying layer 12 is measured at at least 10 locations along the longitudinal direction of the magnetic tape T. These measurements are then simply averaged (arithmetic mean) to obtain the average thickness of the underlying layer for each of the three samples. The arithmetic mean of the three obtained average thicknesses of the underlying layer is the average thickness of the underlying layer contained in the magnetic recording medium according to this technique.

[0158] (Average thickness of the base layer)

[0159] The average thickness of the base layer 11 is determined as follows. First, a magnetic tape T housed in a cartridge such as the magnetic recording cartridge 10A described later is unwound, and three samples are prepared by cutting the magnetic tape T to a length of 250 mm at three locations: 20 m, 40 m, and 60 m in the longitudinal direction from the connection point 221 between the magnetic tape T and the leader tape LT. In this specification, "longitudinal direction" when referring to "the longitudinal direction from the connection point between the magnetic tape T and the leader tape LT" means the direction from one end of the leader tape LT to the other end on the opposite side.

[0160] Next, the layers of the sample other than the base layer 11 (i.e., the non-magnetic layer (underlayer) 12, the magnetic layer 13, and the back layer 14) are removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Then, using a Mitutoyo laser hologage (LGH-110C) as the measuring device, the thickness of the sample (base layer 11) is measured at five points, and these measurements are simply averaged (arithmetic mean) to calculate the average base layer thickness for each of the three samples. The five measurement points are randomly selected from the sample so that they are all different positions along the longitudinal direction of the magnetic tape T. The arithmetic mean of the three average base layer thicknesses obtained is the average thickness of the base layer contained in the magnetic recording medium according to this technology.

[0161] (Average thickness of back layer t) b )

[0162] The upper limit of the average thickness of the backing layer 14 is preferably 0.6 μm or less. When the upper limit of the average thickness of the backing layer 14 is 0.6 μm or less, even if the average thickness of the magnetic tape T is 5.6 μm or less, the thickness of the underlayment (non-magnetic layer) 12 and the base layer 11 can be kept thick, thereby maintaining the running stability of the magnetic tape T within the recording and playback device. The lower limit of the average thickness of the backing layer 14 is not particularly limited, but for example, it is 0.2 μm or more.

[0163] Average thickness t of back layer 14 b This can be calculated as follows: First, the average thickness (average total thickness) of the magnetic tape T is t. T Measure the average thickness t. T The method for measuring the (average total thickness) is as described above. Next, the magnetic tape T housed in cartridge 10A is unwound, and three 250mm lengths of magnetic tape T are cut from the connection point 221 between the magnetic tape T and the leader tape LT at three locations: 20m, 40m, and 60m in the longitudinal direction, to prepare three samples. Next, the back layer 14 of each sample is removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, the thickness of each sample is measured at five locations using a Mitutoyo laser hologaze (LGH-110C), and these measurements are simply averaged (arithmetic mean) to obtain the average value (t) of each sample. B20 , t B40 , and t B60 Calculate [μm]. B20 , t B40 , and t B60 These are the average values ​​at 20m, 40m, and 60m, respectively. Then, the arithmetic mean t of the average values ​​at these three locations is calculated. BTo obtain. Note that the above five measurement positions are randomly selected from the sample so as to be at different positions in the longitudinal direction of the magnetic tape T. Then, the average thickness t of the back layer 14 is obtained from the following formula b [μm]. t b [μm]=t T [μm] - t B [μm]

[0164] (Average thickness t of the magnetic layer m )

[0165] The average thickness t of the magnetic layer 13 is obtained as follows. First, the magnetic tape T housed in the cartridge 10A is unwound, and three samples are prepared by cutting out the magnetic tape T at three positions 20 m, 40 m, and 60 m in the longitudinal direction from the connection part 221 between the magnetic tape T and the leader tape LT, each with a length of 250 mm. Subsequently, each sample is processed by the FIB method or the like to be thinned. When using the FIB method, as a pretreatment for observing the TEM image of the cross section described later, a carbon layer and a tungsten layer are formed as protective films. The carbon layer is formed on the surface of the magnetic layer 13 side and the surface of the back layer 14 side of the magnetic tape T by vapor deposition, and the tungsten layer is further formed on the surface of the magnetic layer 13 side by vapor deposition or sputtering. The thinning is performed along the longitudinal direction of the magnetic tape T. That is, by the thinning, a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic tape T is formed.

[0166] The cross sections of the obtained thinned samples are observed by a transmission electron microscope (TEM) under the following conditions to obtain the TEM images of each thinned sample. Note that the magnification and acceleration voltage may be appropriately adjusted according to the type of the apparatus. Apparatus: TEM (H9000NAR manufactured by Hitachi, Ltd.) Acceleration voltage: 300 kV Magnification: 100,000 times

[0167] ​​ Next, the thickness of the magnetic layer 13 is measured at 10 points on each thinned sample using TEM images of each sample. The 10 measurement points on each thinned sample are randomly selected from the sample so that they are all different locations along the longitudinal direction of the magnetic tape T. The average value obtained by simply averaging (arithmetic mean) the measured values ​​of each thinned sample (a total of 30 points of magnetic layer 13 thickness) is then used to determine the average thickness t of the magnetic layer 13. m Let it be [nm].

[0168] (Ratio of sides in the vertical direction Rs²)

[0169] The square aspect ratio Rs2 in the vertical direction (thickness direction) of the magnetic recording medium of this technology is preferably 65% ​​or more, more preferably 67% or more, and even more preferably 70% or more. When the square aspect ratio Rs2 is 65% or more, the vertical orientation of the magnetic powder becomes sufficiently high, so a better SNR can be obtained. Therefore, better electromagnetic conversion characteristics can be obtained. In addition, the servo signal shape is improved, making it easier to control the drive side. Within this specification, "vertically oriented magnetic recording medium" may mean that the angularity ratio Rs2 of the magnetic recording medium is within the above numerical range (for example, 65% or more).

[0170] The aspect ratio Rs2 in the vertical direction is determined as follows. First, the magnetic tape T housed in the magnetic recording cartridge 10A is unwound, and a 250mm length of the magnetic tape T is cut at a position 30m longitudinally from the connection point 221 between the magnetic tape T and the leader tape LT to prepare a sample. After punching out this sample to 6.25mm × 64mm, it is folded into thirds to prepare a 6.25mm × 8mm measurement sample. Then, the MH hysteresis loop of the measurement sample (the entire magnetic tape T) corresponding to the vertical direction (thickness direction) of the magnetic tape T is measured using a VSM. Next, the coating (underlayer 12, magnetic layer 13, and back layer 14, etc.) is wiped off using acetone or ethanol, leaving only the base layer 11. Then, the obtained base layer 11 is punched out to 6.25mm × 64mm, folded into thirds to make a 6.25mm × 8mm sample for background correction (hereinafter simply referred to as the "correction sample"). Subsequently, the MH hysteresis loop of the correction sample (base layer 11) corresponding to the vertical direction of the base layer 11 (the vertical direction of the magnetic recording medium 10) is measured using a VSM.

[0171] For measuring the MH hysteresis loop of the measurement sample (the entire magnetic tape T) and the MH hysteresis loop of the correction sample (base layer 11), a high-sensitivity vibrating sample type magnetometer "VSM-P7-15" manufactured by Toei Kogyo Co., Ltd. is used. The measurement conditions are as follows: measurement mode: full loop, maximum magnetic field: 15 kOe, magnetic field step: 40 bits, time constant of locking amp: 0.3 sec, waiting time: 1 sec, MH average number: 20. After obtaining the MH hysteresis loops for the measurement sample (the entire magnetic tape T) and the correction sample (base layer 11), background correction is performed by subtracting the MH hysteresis loop of the correction sample (base layer 11) from the MH hysteresis loop of the measurement sample (the entire magnetic tape T), and the MH hysteresis loop after background correction is obtained. The measurement and analysis program included with the "VSM-P7-15" is used to calculate this background correction.

[0172] The obtained background-corrected saturation magnetization Ms(emu) and remanent magnetization Mr(emu) of the MH hysteresis loop are substituted into the following formula to calculate the square aspect ratio Rs²(%). Note that all MH hysteresis loop measurements are performed at 25°C. Furthermore, "demagnetization correction" is not performed when measuring the MH hysteresis loop perpendicular to the magnetic tape T. The measurement and analysis program included with the "VSM-P7-15" is used for this calculation. Squareness ratio Rs2(%)=(Mr / Ms)×100

[0173] (4) Method for manufacturing magnetic recording media

[0174] Next, a method for manufacturing the magnetic recording medium 10 having the above-described configuration will be explained. First, a coating for forming a base layer (non-magnetic layer) is prepared by kneading and / or dispersing non-magnetic powder and a binder in a solvent. Next, a coating for forming a magnetic layer is prepared by kneading and / or dispersing magnetic powder, non-magnetic particles, and a binder in a solvent. For the preparation of the coating for forming the magnetic layer and the coating for forming the base layer (non-magnetic layer), for example, the following solvent, dispersion device, and kneading device can be used. As described above, the average height Rpk of the protruding peaks can be adjusted by adjusting the type and / or content of non-magnetic reinforcing particles contained in the coating for forming the magnetic layer.

[0175] Examples of solvents used in the above-mentioned paint preparation 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. One of these may be used, or a mixture of two or more may be used.

[0176] As mixing equipment used in the above-mentioned paint preparation, for example, continuous twin-screw mixers, continuous twin-screw mixers capable of multi-stage dilution, kneaders, pressure kneaders, and roll kneaders may be used, but are not limited to these devices. Furthermore, as dispersion equipment used in the above-mentioned paint preparation, for example, bead mills, roll mills, ball mills, horizontal sand mills, vertical sand mills, spike mills, pin mills, tower mills, pearl mills (for example, Eich's "DCP mill"), homogenizers, and ultrasonic dispersers may be used, but are not limited to these devices.

[0177] Next, a primer-forming paint is applied to one main surface of the base layer 11 and dried to form the primer layer 12. Subsequently, a magnetic layer-forming paint is applied to this primer layer 12 and dried to form the magnetic layer 13 on the non-magnetic layer 12.

[0178] During drying, the magnetic powder is magnetically oriented in the thickness direction of the base layer 11, for example, using a solenoid coil. Alternatively, during drying, the magnetic powder may be magnetically oriented in the longitudinal direction (travel direction) of the base layer 11 using a solenoid coil, and then magnetically oriented in the thickness direction of the base layer 11. By performing such magnetic field orientation treatment, the ratio Hc2 / Hc1 of the coercivity force in the vertical direction "Hc1" to the coercivity force in the longitudinal direction "Hc2" can be lowered, and the degree of vertical orientation of the magnetic powder can be improved. After the formation of the magnetic layer 13, a back layer 14 is formed on the other main surface of the base layer 11. This gives rise to the magnetic recording medium 10.

[0179] The ratio Hc2 / Hc1 can be set to a desired value by adjusting, for example, the strength of the magnetic field applied to the coating of the magnetic layer forming paint, the concentration of solids in the magnetic layer forming paint, and the drying conditions (drying temperature and drying time) of the coating of the magnetic layer forming paint. The strength of the magnetic field applied to the coating is preferably two to three times the coercivity of the magnetic powder. To further increase the ratio Hc2 / Hc1, it is also preferable to magnetize the magnetic powder before it enters the orientation device used to orient the magnetic powder in a magnetic field. The method for adjusting the ratio Hc2 / Hc1 may be used alone or in combination of two or more methods.

[0180] Subsequently, the obtained magnetic recording medium 10 is rewound onto a large-diameter core and subjected to a hardening treatment. Finally, the magnetic recording medium 10 is calendered and then cut to a predetermined width (for example, 1 / 2 inch width). Furthermore, the manufacturing method may include a strain relief step to relieve the strain on the magnetic recording medium before cutting. Furthermore, the manufacturing method may include a servo signal recording step for recording a servo signal after the cutting and a strain relief step for relieving the strain of the magnetic recording medium after the servo signal recording step. By adjusting the temperature and / or time in these strain relaxation processes, the average value A of the loss modulus E'' can be adjusted. (E”) , the average value A of the storage modulus E' (E’) , and the mean value of Tanδ A (Tanδ), and the amount of variation ΔW 40h It can be adjusted. The manufacturing method described above yields the desired elongated magnetic recording medium 10.

[0181] (5) Recording and playback device

[0182] [Configuration of the recording and playback device]

[0183] Next, with reference to Figure 6, an example of the configuration of a recording and playback device 30 that records and plays back a magnetic recording medium 10 having the above-described configuration will be explained.

[0184] The recording and playback device 30 may be configured to adjust the tension applied to the magnetic recording medium 10 in the longitudinal direction. The recording and playback device 30 also has a configuration that allows for the loading of a magnetic recording cartridge 10A. For the sake of clarity, this explanation describes the case where the recording and playback device 30 has a configuration that allows for the loading of one magnetic recording cartridge 10A; however, the recording and playback device 30 may have a configuration that allows for the loading of multiple magnetic recording cartridges 10A. The recording and playback device 30 is preferably a timing servo type magnetic recording and playback device. The magnetic recording medium of this technology is suitable for use in a timing servo type magnetic recording and playback device.

[0185] The recording and playback device 30 is connected to an information processing device such as a server 41 and a personal computer (hereinafter referred to as "PC") 42 via a network 43, and is configured to record data supplied from these information processing devices onto a magnetic recording cartridge 10A. The shortest recording wavelength of the recording and playback 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.

[0186] As shown in Figure 6, the recording and playback device comprises a spindle 31, a reel 32 on the recording and playback device side, a spindle drive unit 33, a reel drive unit 34, a plurality of guide rollers 35, a head unit 36, a communication interface (hereinafter referred to as I / F) 37, and a control device 38.

[0187] The spindle 31 is configured to accommodate a magnetic recording cartridge 10A. The magnetic recording cartridge 10A conforms to the LTO (Linear Tape Open) standard and rotatably houses a single reel 10C with a magnetic recording medium 10 wound around it in a cartridge case 10B. A V-shaped servo pattern is pre-recorded on the magnetic recording medium 10 as a servo signal. The reel 32 is configured to fix the tip of the magnetic recording medium 10 as it is pulled out from the magnetic recording cartridge 10A. This technology also provides a magnetic recording cartridge containing a magnetic recording medium according to this technology. Within the magnetic recording cartridge, the magnetic recording medium may be wound on a reel, for example, and may be housed in a case while wound on the reel.

[0188] The spindle drive unit 33 is a device that rotates the spindle 31. The reel drive unit 34 is a device that rotates the reel 32. When recording or playing data on the magnetic recording medium 10, the spindle drive unit 33 and the reel drive unit 34 rotate the spindle 31 and the reel 32, thereby moving the magnetic recording medium 10. The guide roller 35 is a roller that guides the movement of the magnetic recording medium 10.

[0189] The head unit 36 ​​includes a plurality of recording heads for recording data signals on the magnetic recording medium 10, a plurality of playback 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. For example, a ring-type head can be used as the recording head, but the type of recording head is not limited to this.

[0190] Communication I / F 37 is used for communication with information processing devices such as server 41 and PC 42, and is connected to network 43.

[0191] The control device 38 controls the entire recording and playback device 30. For example, the control device 38 records data signals supplied from information processing devices such as the server 41 and PC 42 onto the magnetic recording medium 10 using the head unit 36, in response to requests from these devices. The control device 38 also reproduces the data signals recorded on the magnetic recording medium 10 using the head unit 36, in response to requests from information processing devices such as the server 41 and PC 42, and supplies them to the information processing devices.

[0192] Furthermore, the control device 38 detects changes in the width of the magnetic recording medium 10 based on the servo signals supplied from the head unit 36. Specifically, the magnetic recording medium 10 has multiple V-shaped servo patterns recorded as servo signals, and the head unit 36 ​​can simultaneously reproduce two different servo patterns using two servo heads on the head unit 36 ​​and obtain the respective servo signals. Using the relative position information between the servo pattern and the head unit obtained from these servo signals, the position of the head unit 36 ​​is controlled to track the servo pattern. At the same time, distance information between the servo patterns can also be obtained by comparing the two servo signal waveforms. By comparing this distance information between servo patterns obtained at each measurement, the change in the distance between servo patterns at each measurement can be obtained. By adding the distance information between servo patterns at the time of servo pattern recording to this, the change in the width of the magnetic recording medium 10 can also be calculated. The control device 38 controls the rotational drive of the spindle drive unit 33 and the reel drive unit 34 based on the change in distance between the servo patterns obtained as described above, or the calculated change in the width of the magnetic recording medium 10, and adjusts the longitudinal tension of the magnetic recording medium 10 so that the width of the magnetic recording medium 10 becomes a specified width or approximately a specified width. This makes it possible to suppress changes in the width of the magnetic recording medium 10.

[0193] [Operation of the recording / playback device]

[0194] Next, the operation of the recording and playback device 30 having the above configuration will be described.

[0195] First, the magnetic recording cartridge 10A is mounted in the recording / playback device 30, the leading edge of the magnetic recording medium 10 is pulled out and transported to the reel 32 via multiple guide rollers 35 and the head unit 36, and the leading edge of the magnetic recording medium 10 is attached to the reel 32.

[0196] Next, when the operating unit (not shown) is operated, the spindle drive unit 33 and the reel drive unit 34 are driven by the control device 38, and the spindle 31 and reel 32 are rotated in the same direction so that the magnetic recording medium 10 travels from reel 10C to reel 32. As a result, the magnetic recording medium 10 is wound onto reel 32, and the head unit 36 ​​records information onto the magnetic recording medium 10 or plays back information recorded on the magnetic recording medium 10.

[0197] Furthermore, when rewinding the magnetic recording medium 10 onto reel 10C, the spindle 31 and reel 32 are rotated in the opposite direction to that described above, causing the magnetic recording medium 10 to travel from reel 32 to reel 10C. During this rewinding process, the head unit 36 ​​also records information onto the magnetic recording medium 10 or plays back information recorded on the magnetic recording medium 10.

[0198] (6) Variant

[0199] [Example 1]

[0200] The magnetic recording medium 10 may further include a barrier layer 15 provided on at least one surface of the base layer 11, as shown in Figure 7. The barrier layer 15 is a layer for suppressing dimensional deformation of the base layer 11 in response to the environment. For example, one cause of such dimensional deformation is the hygroscopicity of the base layer 11, and the barrier layer 15 can reduce the rate at which moisture penetrates the base layer 11. The barrier layer 15 contains a metal or a metal oxide. As the metal, 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 can be used. As the metal oxide, at least one of Al2O3, CuO, CoO, SiO2, Cr2O3, TiO2, Ta2O5, and ZrO2 can be used, or any of the above metal oxides can be used. Alternatively, diamond-like carbon (DLC) or diamond can be used.

[0201] The average thickness of the barrier layer 15 is preferably 20 nm to 1000 nm, more preferably 50 nm to 1000 nm. The average thickness of the barrier layer 15 is equal to the average thickness of the magnetic layer 13. m It can be determined in the same manner as above. However, the magnification of the TEM image is adjusted as appropriate according to the thickness of the barrier layer 15.

[0202] [Differentiation 2]

[0203] The magnetic recording medium 10 may be incorporated into a library device. That is, the technology also provides a library device comprising at least one magnetic recording medium 10. The library device has a configuration that allows adjustment of the tension applied to the magnetic recording medium 10 in the longitudinal direction, and may comprise multiple recording and playback devices 30 as described above.

[0204] [Difference 3]

[0205] The magnetic recording medium 10 may be subjected to servo signal writing processing by a servo writer. The servo writer can maintain a constant or nearly constant width of the magnetic recording medium 10 by adjusting the longitudinal tension of the magnetic recording medium 10 when recording servo signals. In this case, the servo writer may be equipped with a detection device for detecting the width of the magnetic recording medium 10. The servo writer can adjust the longitudinal tension of the magnetic recording medium 10 based on the detection result of the detection device.

[0206] 3. Second Embodiment (Example of a Vacuum Thin-Film Magnetic Recording Medium)

[0207] (1) Configuration of magnetic recording medium

[0208] An example of a magnetic recording medium in this embodiment will be described with reference to Figure 8. The figure shows a schematic cross-sectional view of a vacuum thin-film type magnetic recording medium 810 in this embodiment. The magnetic recording medium 810 is a long, perpendicular magnetic recording medium and, as shown in the figure, comprises a film-like base layer 811, a soft magnetic underlayer (hereinafter referred to as "SUL") 812, a first seed layer 813A, a second seed layer 813B, a first underlayer 814A, a second underlayer 814B, and a magnetic layer 815. The SUL 812, the first and second seed layers 813A and 813B, the first and second underlayers 814A and 814B, and the magnetic layer 815 may be vacuum thin films, such as layers formed by sputtering (hereinafter also referred to as "sputtered layers").

[0209] SUL812, the first and second seed layers 813A and 813B, and the first and second underlay layers 814A and 814B are provided between one main surface (hereinafter referred to as the "surface") of the base layer 811 and the magnetic layer 815, and are stacked in the order of SUL812, the first seed layer 813A, the second seed layer 813B, the first underlay layer 814A, and the second underlay layer 814B from the base layer 811 toward the magnetic layer 815.

[0210] The magnetic recording medium 810 may further include, if necessary, a protective layer 816 provided on the magnetic layer 815 and a lubricating layer 817 provided on the protective layer 816. Furthermore, the magnetic recording medium 810 may further include, if necessary, a back layer 818 provided on the other main surface (hereinafter referred to as the "back surface") of the base layer 811.

[0211] The magnetic recording medium according to the second embodiment exhibits excellent storage stability when stored in a high-temperature environment and excellent running stability after such storage, similar to the first embodiment. Furthermore, this magnetic recording medium also exhibits excellent electromagnetic conversion characteristics.

[0212] Hereinafter, the longitudinal direction of the magnetic recording medium 810 (the longitudinal direction of the base layer 811) will be referred to as the machine direction (MD). Here, the machine direction means the relative direction of movement of the recording and playback heads with respect to the magnetic recording medium 810, that is, the direction in which the magnetic recording medium 810 travels during recording and playback.

[0213] The magnetic recording medium 810 is suitable for use as a storage medium for data archiving, for which demand is expected to increase significantly in the future. This magnetic recording medium 810 has an areal recording density more than 10 times that of current coated magnetic recording media for storage, i.e., 50 Gb / in². 2 It is possible to achieve the above-mentioned areal recording density. When a data cartridge for a general linear recording system is constructed using a magnetic recording medium 810 having such an areal recording density, it becomes possible to record a large capacity of 100 TB or more per data cartridge.

[0214] The magnetic recording medium 810 is suitable for use in a recording and playback device (a recording and playback device for recording and playback of data) having a ring-type recording head and a giant magnetoresistive (GMR) type or tunneling magnetoresistive (TMR) type playback head. Furthermore, in the magnetic recording medium 810 according to the second embodiment, it is preferable that a ring-type recording head is used as the servo signal writing head. Data signals are vertically recorded in the magnetic layer 815 by, for example, a ring-type recording head. Also, servo signals are vertically recorded in the magnetic layer 815 by, for example, a ring-type recording head.

[0215] (2) Explanation of each layer

[0216] (Base layer)

[0217] The description of the base layer 811 is the same as the description of the base layer 11 in the first embodiment, so the description of the base layer 811 will be omitted. The average thickness of the base layer 811 is measured in the same way as the base layer in the first embodiment, except that layers other than the base layer of each sample are removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid, and then washed with pure water.

[0218] (SUL)

[0219] SUL812 includes an amorphous soft magnetic material. The soft magnetic material includes, for example, at least one of Co-based materials and Fe-based materials. The Co-based material includes, for example, CoZrNb, CoZrTa, or CoZrTaNb. The Fe-based material includes, for example, FeCoB, FeCoZr, or FeCoTa.

[0220] SUL812 is a single-layer SUL, directly provided on the base layer 811. The average thickness of SUL812 is preferably 10 nm to 50 nm, more preferably 20 nm to 30 nm.

[0221] The average thickness of SUL812 is determined by the same method as the method for measuring the average thickness of the magnetic layer 13 in the first embodiment. The average thicknesses of the layers other than SUL812 (i.e., the average thicknesses of the first and second seed layers 813A and 813B, the first and second underlay layers 814A and 814B, and the magnetic layer 815), as described later, are also determined by the same method as the method for measuring the average thickness of the magnetic layer 13 in the first embodiment. However, the magnification of the TEM image is adjusted appropriately according to the thickness of each layer.

[0222] (First and second seed layers)

[0223] The first seed layer 813A contains an alloy containing Ti and Cr and is in an amorphous state. This alloy may also contain oxygen (O). This oxygen may be impurity oxygen present in trace amounts within the first seed layer 813A when it is deposited using a film deposition method such as sputtering.

[0224] Here, "alloy" refers to at least one of the following: solid solutions containing Ti and Cr, eutectic materials, and intermetallic compounds. "Amorphous state" means that a halo is observed by X-ray diffraction or electron diffraction, and the crystal structure cannot be determined.

[0225] The atomic ratio of Ti to the total amount of Ti and Cr contained in the first seed layer 813A is preferably in the range of 30 atomic% or more and less than 100 atomic%, more preferably in the range of 50 atomic% or more and less than 100 atomic%. If the atomic ratio of Ti is less than 30%, the (100) plane of the body-centered cubic lattice (bcc) structure of Cr will become oriented, which may reduce the orientation of the first and second underlayers 814A and 814B formed on the first seed layer 813A.

[0226] The atomic ratio of Ti mentioned above is determined as follows: While ion milling the magnetic recording medium 810 from the magnetic layer 815 side, depth profile analysis (depth profile measurement) of the first seed layer 813A is performed by Auger electron spectroscopy (hereinafter referred to as "AES"). Next, the average composition (average atomic ratio) of Ti and Cr in the film thickness direction is determined from the obtained depth profile. Then, the atomic ratio of Ti mentioned above is determined using the determined average composition of Ti and Cr.

[0227] When the first seed layer 813A contains Ti, Cr, and O, the atomic ratio of O to the total amount of Ti, Cr, and O contained in the first seed layer 813A is preferably 15 atomic% or less, more preferably 10 atomic% or less. If the atomic ratio of O exceeds 15 atomic%, TiO2 crystals will be formed, which will affect the crystal nucleation of the first and second underlayers 814A and 814B formed on the first seed layer 813A, and there is a risk that the orientation of the first and second underlayers 814A and 814B will decrease. The atomic ratio of O is determined using the same analytical method as the atomic ratio of Ti.

[0228] The alloy contained in the first seed layer 813A may further contain elements other than Ti and Cr as additive elements. These additive elements may be, for example, one or more elements selected from the group consisting of Nb, Ni, Mo, Al, and W.

[0229] The average thickness of the first seed layer 813A is preferably 2 nm to 15 nm, more preferably 3 nm to 10 nm.

[0230] The second seed layer 813B contains, for example, NiW or Ta and has a crystalline state. The average thickness of the second seed layer 813B is preferably 3 nm to 20 nm, more preferably 5 nm to 15 nm.

[0231] The first and second seed layers 813A and 813B have a crystalline structure similar to the first and second sub-layers 814A and 814B. They are not seed layers provided for the purpose of crystal growth, but rather seed layers that improve the vertical orientation of the first and second sub-layers 814A and 814B through the amorphous state of the first and second seed layers 813A and 813B.

[0232] (First and second subsoil layers)

[0233] The first and second underlayers 814A and 814B preferably have a crystal structure similar to that of the magnetic layer 815. If the magnetic layer 815 contains a Co-based alloy, the first and second underlayers 814A and 814B preferably contain a material having a hexagonal close-packed (hcp) structure similar to that of the Co-based alloy, and the c-axis of this structure is oriented perpendicular to the film plane (i.e., in the film thickness direction). This is because it enhances the orientation of the magnetic layer 815 and allows for a relatively good matching of the lattice constants between the second underlayer 814B and the magnetic layer 815. As the material having a hexagonal close-packed (hcp) structure, it is preferable to use a material containing Ru, specifically Ru alone or a Ru alloy. Examples of Ru alloys include Ru-SiO2, Ru-TiO2, and Ru-ZrO2, and the Ru alloy may be any one of these.

[0234] As described above, the same material can be used for the first and second underlayers 814A and 814B. However, the intended effects of the first and second underlayers 814A and 814B are different. Specifically, the second underlayer 814B has a film structure that promotes the granular structure of the magnetic layer 815 that is above it, while the first underlayer 814A has a film structure with high crystal orientation. To obtain such film structures, it is preferable to use different film deposition conditions, such as sputtering conditions, for the first and second underlayers 814A and 814B.

[0235] The average thickness of the first underlayer 814A is preferably 3 nm to 15 nm, more preferably 5 nm to 10 nm. The average thickness of the second underlayer 814B is preferably 7 nm to 40 nm, more preferably 10 nm to 25 nm.

[0236] (magnetic layer)

[0237] The magnetic layer (also called the recording layer) 815 may be a perpendicular magnetic recording layer in which the magnetic material is oriented vertically. From the viewpoint of improving recording density, the magnetic layer 815 is preferably a granular magnetic layer containing a Co-based alloy. This granular magnetic layer is composed of ferromagnetic crystalline particles containing a Co-based alloy and non-magnetic grain boundaries (non-magnetic materials) surrounding these ferromagnetic crystalline particles. More specifically, this granular magnetic layer is composed of columns (columnar crystals) containing a Co-based alloy and non-magnetic grain boundaries (e.g., oxides such as SiO2) surrounding these columns and magnetically separating each column. In this structure, a magnetic layer 815 can be constructed in which each column is magnetically separated.

[0238] Co-based alloys have a hexagonal close-packed (hcp) structure, with their c-axis oriented perpendicular to the film surface (film thickness direction). Preferably, a CoCrPt alloy containing at least Co, Cr, and Pt is used as the Co-based alloy. The CoCrPt alloy may further contain additive elements. Examples of additive elements include one or more elements selected from the group consisting of Ni and Ta.

[0239] The non-magnetic grain boundaries surrounding the ferromagnetic crystal grains include a non-magnetic metallic material. Here, the metal includes metalloids. As the non-magnetic metallic material, for example, at least one of metal oxides and metal nitrides can be used, and from the viewpoint of maintaining the granular structure more stably, it is preferable to use a metal oxide. Examples of metal oxides include metal oxides containing at least one element selected from the group consisting of Si, Cr, Co, Al, Ti, Ta, Zr, Ce, Y, and Hf, and metal oxides containing at least Si oxide (i.e., SiO2) are preferred. Specific examples of metal oxides include SiO2, Cr2O3, CoO, Al2O3, TiO2, Ta2O5, ZrO2, and HfO2. Examples of metal nitrides include metal nitrides containing at least one element selected from the group consisting of Si, Cr, Co, Al, Ti, Ta, Zr, Ce, Y, and Hf. Specific examples of metal nitrides include SiN, TiN, and AlN.

[0240] It is preferable that the CoCrPt alloy contained in the ferromagnetic crystal particles and the Si oxide contained in the non-magnetic grain boundaries have the average composition shown in the following formula (1). This is because it is possible to achieve a saturation magnetization amount Ms that suppresses the effect of the demagnetizing field and ensures sufficient playback output, thereby further improving the recording and playback characteristics. (Co x Pt y Cr 100-x-y ) 100-z -(SiO2) z ...(1) (However, in equation (1), x, y, and z are values ​​within the ranges of 69 ≤ X ≤ 75, 10 ≤ y ≤ 16, and 9 ≤ Z ≤ 12, respectively.)

[0241] The above composition can be determined as follows: While ion milling the magnetic recording medium 810 from the magnetic layer 815 side, depth profiling of the magnetic layer 815 is performed by AES to determine the average composition (average atomic ratio) of Co, Pt, Cr, Si, and O in the film thickness direction.

[0242] Average thickness t of magnetic layer 815m [nm] is preferably 9nm ≤ t m ≤90nm, 9nm ≤t m ≤20nm, more preferably 9nm ≤t m The average thickness of the magnetic layer 815 is ≤15nm. m By keeping the above numerical range within which the electromagnetic conversion characteristics can be improved.

[0243] (protective layer)

[0244] The protective layer 816 may, for example, contain a carbon material or silicon dioxide (SiO2), and from the viewpoint of the film strength of the protective layer 816, it is preferable to contain a carbon material. Examples of carbon materials include graphite, diamond-like carbon (DLC), or diamond.

[0245] (lubricating layer)

[0246] The lubrication layer 817 contains at least one type of lubricant. The lubrication layer 817 may further contain various additives, such as rust inhibitors, as needed. The lubricant contains at least one carboxylic acid compound having at least two carboxyl groups and one ester bond, and represented by the following general formula (1). The lubricant may further contain a type of lubricant other than the carboxylic acid compound represented by the following general formula (1). General formula (1): [ka] (In the formula, Rf is an unsubstituted or substituted saturated or unsaturated fluorine-containing hydrocarbon group or hydrocarbon group, Es is an ester bond, and R is optional but is an unsubstituted or substituted saturated or unsaturated hydrocarbon group.)

[0247] The above carboxylic acid compounds are preferably represented by the following general formula (2) or (3). General formula (2): [ka] (In the formula, Rf is an unsubstituted or substituted saturated or unsaturated fluorine-containing hydrocarbon group or hydrocarbon group.) General formula (3): [ka] (In the formula, Rf is an unsubstituted or substituted saturated or unsaturated fluorine-containing hydrocarbon group or hydrocarbon group.)

[0248] The lubricant preferably contains one or both of the carboxylic acid compounds represented by the above general formulas (2) and (3).

[0249] When a lubricant containing a carboxylic acid compound represented by general formula (1) is applied to the magnetic layer 815 or protective layer 816, a lubricating effect is exhibited due to the cohesive force between hydrophobic fluorine-containing hydrocarbon groups or hydrocarbon groups Rf. When the Rf group is a fluorine-containing hydrocarbon group, it is preferable that the total number of carbon atoms is 6 to 50 and the total number of carbon atoms of the fluorinated hydrocarbon group is 4 to 20. The Rf group may be, for example, a saturated or unsaturated linear, branched, or cyclic hydrocarbon group, but it is preferably a saturated linear hydrocarbon group.

[0250] For example, if the Rf group is a hydrocarbon group, it is desirable that it be a group represented by the following general formula (4). General formula (4): [ka] (However, in general formula (4), l is an integer selected from the range of 8 to 30, more preferably from 12 to 20.)

[0251] Furthermore, if the Rf group is a fluorine-containing hydrocarbon group, it is desirable that it be a group represented by the following general formula (5). General formula (5): [ka] (However, in general formula (5), m and n are integers independently chosen from the following ranges: m = 2 to 20, n = 3 to 18, more preferably m = 4 to 13, n = 3 to 10.)

[0252] The fluorinated hydrocarbon group may be concentrated in one location within the molecule as described above, or it may be dispersed as shown in general formula (6) below, and it may be -CF3 or -CF2-, as well as -CHF2 or -CHF-, etc. General formula (6): [ka] (However, in general formulas (5) and (6), n1+n2=n and m1+m2=m.)

[0253] The reason for limiting the number of carbon atoms in general formulas (4), (5), and (6) as described above is that when the number of carbon atoms constituting the alkyl group or fluorine-containing alkyl group (l, or the sum of m and n) is equal to or greater than the lower limit, the length becomes appropriate, the cohesive force between hydrophobic groups is effectively exerted, good lubrication is achieved, and friction and wear durability is improved. Furthermore, when the number of carbon atoms is equal to or less than the upper limit, the solubility of the lubricant consisting of the carboxylic acid compound in the solvent is well maintained.

[0254] In particular, the Rf group in general formulas (1), (2), and (3), when containing a fluorine atom, is effective in reducing the coefficient of friction and improving drivability. However, it is preferable to provide a hydrocarbon group between the fluorine-containing hydrocarbon group and the ester bond, thereby ensuring the stability of the ester bond and preventing hydrolysis.

[0255] Furthermore, the Rf group may have a fluoroalkyl ether group or a perfluoropolyether group.

[0256] The R group in general formula (1) is optional, but if present, it is preferably a hydrocarbon chain with a relatively small number of carbon atoms.

[0257] Furthermore, the Rf group or R group may contain one or more elements selected from nitrogen, oxygen, sulfur, phosphorus, and halogens as constituent elements, and in addition to the functional groups described above, it may further have a hydroxyl group, a carboxyl group, a carbonyl group, an amino group, an ester bond, etc.

[0258] The carboxylic acid compound represented by general formula (1) is preferably at least one of the following compounds. In other words, the lubricant preferably contains at least one of the following compounds. CF3(CF2)7(CH2) 10 COOCH(COOH)CH2COOH CF3(CF2)3(CH2) 10 COOCH(COOH)CH2COOH C 17 H 35 COOCH(COOH)CH2COOH CF3(CF2)7(CH2)2OCOCH2CH(C 18 H 37 )COOCH(COOH)CH2COOH CF3(CF2)7COOCH(COOH)CH2COOH CHF2(CF2)7COOCH(COOH)CH2COOH CF3(CF2)7(CH2)2OCOCH2CH(COOH)CH2COOH CF3(CF2)7(CH2)6OCOCH2CH(COOH)CH2COOH CF3(CF2)7(CH2) 11 OCOCH2CH(COOH)CH2COOH CF3(CF2)3(CH2)6OCOCH2CH(COOH)CH2COOH C 18 H 37 OCOCH2CH(COOH)CH2COOH CF3(CF2)7(CH2)4COOCH(COOH)CH2COOH CF3(CF2)3(CH2)4COOCH(COOH)CH2COOH CF3(CF2)3(CH2)7COOCH(COOH)CH2COOH CF3(CF2)9(CH2) 10 COOCH(COOH)CH2COOH CF3(CF2)7(CH2) 12 COOCH(COOH)CH2COOH CF3(CF2)5(CH2) 10 COOCH(COOH)CH2COOH CF3(CF2)7CH(C9H 19 )CH2CH=CH(CH2)7COOCH(COOH)CH2COOH CF3(CF2)7CH(C6H 13 )(CH2)7COOCH(COOH)CH2COOH CH3(CH2)3(CH2CH2CH(CH2CH2(CF2)9CF3))2(CH2)7COOCH(COOH)CH2COOH

[0259] Carboxylic acid compounds represented by general formula (1) are soluble in non-fluorinated solvents that have a low environmental impact, and have the advantage of being able to be used in operations such as coating, immersion, and spraying with general-purpose solvents such as hydrocarbon solvents, ketone solvents, alcohol solvents, and ester solvents. Specifically, examples of such general-purpose solvents include hexane, heptane, octane, decane, dodecane, benzene, toluene, xylene, cyclohexane, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol, isopropanol, diethyl ether, tetrahydrofuran, dioxane, and cyclohexanone.

[0260] When the protective layer 816 contains a carbon material, applying the above-mentioned carboxylic acid compound as a lubricant onto the protective layer 816 allows two carboxyl groups and at least one ester bond group, which are the polar bases of the lubricant molecule, to be adsorbed onto the protective layer 816. Due to the cohesive force between the hydrophobic groups, a particularly durable lubricating layer 817 can be formed.

[0261] Furthermore, the lubricant may not only be held as a lubricating layer 817 on the surface of the magnetic recording medium 810 as described above, but may also be contained in and held in layers such as the magnetic layer 815 and the protective layer 816 that constitute the magnetic recording medium 810.

[0262] (Back layer)

[0263] The description of the back layer 14 in the first embodiment applies to the back layer 818.

[0264] (3) Physical properties and structure

[0265] The description of the physical properties and structure described in 2.(3) above also applies to the second embodiment. The description of the physical properties and structure of the magnetic recording medium in the second embodiment is omitted except for the differences from the first embodiment. The average thickness of the base layer 811 is measured in the same way as the base layer 11 in the first embodiment, except that layers other than the base layer of each sample are removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid, and then washed with pure water.

[0266] (4) Configuration of the sputtering apparatus

[0267] The following describes an example of the configuration of a sputtering apparatus 920 used in the manufacture of a magnetic recording medium 810, with reference to Figure 9. This sputtering apparatus 920 is a continuous winding sputtering apparatus used for depositing SUL812, a first seed layer 813A, a second seed layer 813B, a first underlay layer 814A, a second underlay layer 814B, and a magnetic layer 815. As shown in the figure, it comprises a deposition chamber 921, a drum 922 which is a metal can (rotating body), cathodes 923a to 923f, a supply reel 924, a winding reel 925, and a plurality of guide rollers 927a to 927c, 928a to 928c. The sputtering apparatus 920 is, for example, a DC (direct current) magnetron sputtering apparatus, but the sputtering method is not limited to this method.

[0268] The deposition chamber 921 is connected to a vacuum pump (not shown) via an exhaust port 926, which sets the atmosphere inside the deposition chamber 921 to a predetermined vacuum level. Inside the deposition chamber 921 are a drum 922 having a rotatable configuration, a supply reel 924, and a take-up reel 925. Inside the deposition chamber 921 are a plurality of guide rollers 927a to 927c for guiding the transport of the base layer 811 between the supply reel 924 and the drum 922, and a plurality of guide rollers 928a to 928c for guiding the transport of the base layer 811 between the drum 922 and the take-up reel 925. During sputtering, the base layer 811 unwound from the supply reel 924 is wound onto the take-up reel 925 via the guide rollers 927a to 927c, the drum 922, and the guide rollers 928a to 928c. The drum 922 has a cylindrical shape, and the elongated base layer 811 is transported along the cylindrical circumferential surface of the drum 922. The drum 922 is provided with a cooling mechanism (not shown), and during sputtering, it is cooled to, for example, about -20°C. Inside the deposition chamber 921, a plurality of cathodes 923a to 923f are arranged facing the circumferential surface of the drum 922. Each of these cathodes 923a to 923f is set with a target. Specifically, cathodes 923a, 923b, 923c, 923d, 923e, and 923f are set with targets for depositing SUL 812, a first seed layer 813A, a second seed layer 813B, a first underlay layer 814A, a second underlay layer 814B, and a magnetic layer 815, respectively. These cathodes 923a to 923f simultaneously deposit multiple types of films, namely SUL812, the first seed layer 813A, the second seed layer 813B, the first underlay layer 814A, the second underlay layer 814B, and the magnetic layer 815.

[0269] In the sputtering apparatus 920 having the above configuration, SUL812, the first seed layer 813A, the second seed layer 813B, the first underlayer 814A, the second underlayer 814B, and the magnetic layer 815 can be continuously deposited by the Roll-to-Roll method.

[0270] (5) Method for manufacturing magnetic recording media

[0271] The magnetic recording medium 810 can be manufactured, for example, as follows.

[0272] First, using the sputtering apparatus 920 shown in Figure 9, SUL812, the first seed layer 813A, the second seed layer 813B, the first underlay layer 814A, the second underlay layer 814B, and the magnetic layer 815 are sequentially deposited on the surface of the base layer 811. Specifically, the deposition is carried out as follows: First, the deposition chamber 921 is evacuated to a predetermined pressure. Then, while introducing a process gas such as Ar gas into the deposition chamber 921, targets set on cathodes 923a to 923f are sputtered. As a result, SUL812, the first seed layer 813A, the second seed layer 813B, the first underlay layer 814A, the second underlay layer 814B, and the magnetic layer 815 are sequentially deposited on the surface of the moving base layer 811.

[0273] The atmosphere in the deposition chamber 921 during sputtering is, for example, 1 × 10 -5 Pa~5×10 -5 The pressure is set to approximately Pa. The film thickness and characteristics of SUL812, the first seed layer 813A, the second seed layer 813B, the first base layer 814A, the second base layer 814B, and the magnetic layer 815 can be controlled by adjusting the tape line speed for winding the base layer 811, the pressure of the process gas such as Ar gas introduced during sputtering (sputtering gas pressure), and the input power.

[0274] Next, a protective layer 816 is deposited on the magnetic layer 815. For example, chemical vapor deposition (CVD) or physical vapor deposition (PVD) can be used to deposit the protective layer 816.

[0275] Next, a coating for back layer formation is prepared by mixing and dispersing a binder, inorganic particles, and lubricant in a solvent. Then, the coating for back layer formation is applied to the back surface of the base layer 811 and dried to form a back layer 818 on the back surface of the base layer 811.

[0276] Next, for example, a lubricant is applied to the protective layer 816 to form a lubricating layer 817. Various application methods can be used for the lubricant, such as gravure coating or dip coating. Next, if necessary, the magnetic recording medium 810 is cut to a predetermined width. As a result, the magnetic recording medium 810 shown in Figure 8 is obtained.

[0277] (6) Variant

[0278] The magnetic recording medium 810 may further include an underlayer between the base layer 811 and SUL812. Since SUL812 has an amorphous state, it does not play a role in promoting the epitaxial growth of the layers formed on SUL812, but it is required that the crystal orientation of the first and second underlayers 814A and 814B formed on SUL812 is not disturbed. To this end, it is preferable that the soft magnetic material has a fine structure that does not form columns, but if the effect of gas release such as moisture from the base layer 811 is large, the soft magnetic material may coarseen, which may disturb the crystal orientation of the first and second underlayers 814A and 814B formed on SUL812. In order to suppress the effect of gas release such as moisture from the base layer 811, as described above, it is preferable to provide an underlayer containing an alloy containing Ti and Cr and having an amorphous state between the base layer 811 and SUL812. The specific configuration of this subsoil layer can be the same as that of the first seed layer 813A in the second embodiment.

[0279] The magnetic recording medium 810 does not necessarily have to include at least one of the second seed layer 813B and the second base layer 814B. However, from the viewpoint of improving SNR, it is more preferable to include both the second seed layer 813B and the second base layer 814B.

[0280] The magnetic recording medium 810 may be equipped with APC-SUL (Antiparallel Coupled SUL) instead of a single-layer SUL.

[0281] (7) Other examples of magnetic recording media

[0282] (Configuration of other examples of magnetic recording media)

[0283] The magnetic recording medium in this embodiment may be configured as the magnetic recording medium 830 described below. As shown in Figure 10, the magnetic recording medium 830 comprises a base layer 811, a SUL 812, a seed layer 831, a first underlay layer 832A, a second underlay layer 832B, and a magnetic layer 815. In the description of the magnetic recording medium 830, the same reference numerals are used for components that are the same as those in the magnetic recording medium 810, and their description is omitted.

[0284] SUL812, seed layer 831, and first and second underlayers 832A and 832B are provided between one main surface of the base layer 811 and the magnetic layer 815, and are stacked in the order of SUL812, seed layer 831, first underlayer 832A, and second underlayer 832B from the base layer 811 toward the magnetic layer 815.

[0285] (Seed layer)

[0286] The seed layer 831 contains Cr, Ni, and Fe and has a face-centered cubic (fcc) lattice structure, with the (111) plane of this face-centered cubic structure preferentially oriented parallel to the surface of the base layer 811. Here, preferential orientation means that in a θ-2θ scan of the X-ray diffraction method, the diffraction peak intensity from the (111) plane of the face-centered cubic lattice structure is greater than the diffraction peaks from other crystal planes, or that in a θ-2θ scan of the X-ray diffraction method, only the diffraction peak intensity from the (111) plane of the face-centered cubic lattice structure is observed.

[0287] From the viewpoint of improving SNR, the intensity ratio of the X-ray diffraction of the seed layer 831 is preferably 60 cps / nm or higher, more preferably 70 cps / nm or higher, and even more preferably 80 cps / nm or higher. Here, the intensity ratio of the X-ray diffraction of the seed layer 831 is the value obtained by dividing the X-ray diffraction intensity I (cps) of the seed layer 831 by the average thickness D (nm) of the seed layer 831 (I / D(cps / nm)).

[0288] The Cr, Ni, and Fe contained in the seed layer 831 preferably have an average composition represented by the following formula (2). Cr X (Ni Y Fe 100-Y ) 100-X ...(2) (However, in equation (2), X is within the range of 10 ≤ X ≤ 45 and Y is within the range of 60 ≤ Y ≤ 90.) When X is within the above range, the (111) orientation of the face-centered cubic lattice structure of Cr, Ni, and Fe is improved, and a better SNR can be obtained. Similarly, when Y is within the above range, the (111) orientation of the face-centered cubic lattice structure of Cr, Ni, and Fe is improved, and a better SNR can be obtained.

[0289] The average thickness of the seed layer 831 is preferably between 5 nm and 40 nm. By keeping the average thickness of the seed layer 831 within this range, the (111) orientation of the face-centered cubic lattice structure of Cr, Ni, and Fe can be improved, and a better SNR can be obtained. The average thickness of the seed layer 831 is determined in the same manner as the magnetic layer 13 in the first embodiment. However, the magnification of the TEM image is adjusted appropriately according to the thickness of the seed layer 831.

[0290] (First and second subsoil layers)

[0291] The first sublayer 832A contains Co and O having a face-centered cubic lattice structure and has a columnar (columnar crystal) structure. The first sublayer 832A containing Co and O provides almost the same effect (function) as the second sublayer 832B containing Ru. The concentration ratio of the average atomic concentration of O to the average atomic concentration of Co ((average atomic concentration of O) / (average atomic concentration of Co)) is 1 or greater. When the concentration ratio is 1 or greater, the effect of providing the first sublayer 832A is improved, and a better SNR can be obtained.

[0292] From the viewpoint of improving SNR, the column structure is preferably inclined. The direction of the inclination is preferably the longitudinal direction of the elongated magnetic recording medium 830. The preference for the longitudinal direction is as follows: The magnetic recording medium 830 is a so-called linear recording medium, and the recording track is parallel to the longitudinal direction of the magnetic recording medium 830. The magnetic recording medium 830 is also a so-called perpendicular magnetic recording medium, and from the viewpoint of recording characteristics, it is preferable that the crystal orientation axis of the magnetic layer 815 is perpendicular. However, due to the inclination of the column structure of the first underlayer 832A, the crystal orientation axis of the magnetic layer 815 may be inclined. In a magnetic recording medium 830 for linear recording, due to the relationship with the head magnetic field during recording, a configuration in which the crystal orientation axis of the magnetic layer 815 is inclined in the longitudinal direction of the magnetic recording medium 830 can reduce the influence of the inclination of the crystal orientation axis on recording characteristics compared to a configuration in which the crystal orientation axis of the magnetic layer 815 is inclined in the width direction of the magnetic recording medium 830. In order to tilt the crystal orientation axis of the magnetic layer 815 in the longitudinal direction of the magnetic recording medium 830, it is preferable that the tilt direction of the column structure of the first underlayer 832A be in the longitudinal direction of the magnetic recording medium 830, as described above.

[0293] The tilt angle of the column structure is preferably greater than 0° and 60° or less. In the range where the tilt angle is greater than 0° and 60° or less, the change in the tip shape of the columns contained in the first sublayer 832A is large and becomes almost triangular, so the effect of the granular structure is enhanced, noise is reduced and the SNR tends to improve. On the other hand, when the tilt angle exceeds 60°, the change in the tip shape of the columns contained in the first sublayer 832A is small and it is difficult to make it almost triangular, so the low-noise effect tends to be diminished.

[0294] The average particle size of the column structure is between 3 nm and 13 nm. If the average particle size is less than 3 nm, the average particle size of the column structure contained in the magnetic layer 815 becomes small, which may reduce the recording retention ability of current magnetic materials. On the other hand, if the average particle size is 13 nm or less, noise can be suppressed and a better SNR can be obtained.

[0295] The average thickness of the first underlayer 832A is preferably 10 nm or more and 150 nm or less. If the average thickness of the first underlayer 832A is 10 nm or more, the (111) orientation of the face-centered cubic lattice structure of the first underlayer 832A is improved, and a better SNR can be obtained. On the other hand, if the average thickness of the first underlayer 832A is 150 nm or less, the increase in column particle size can be suppressed. Therefore, noise can be suppressed and a better SNR can be obtained. The average thickness of the first underlayer 832A is determined in the same manner as the magnetic layer 13 in the first embodiment. However, the magnification of the TEM image is appropriately adjusted according to the thickness of the first underlayer 832A.

[0296] The second underlayer 832B preferably has a crystal structure similar to that of the magnetic layer 815. If the magnetic layer 815 contains a Co-based alloy, the second underlayer 832B preferably contains a material having a hexagonal close-packed (hcp) structure similar to that of the Co-based alloy, and the c-axis of that structure is oriented perpendicular to the film surface (i.e., in the film thickness direction). This is because it enhances the orientation of the magnetic layer 815 and allows for a relatively good matching of the lattice constants between the second underlayer 832B and the magnetic layer 815. As the material having a hexagonal close-packed structure, it is preferable to use a material containing Ru, specifically Ru alone or a Ru alloy. Examples of Ru alloys include Ru alloy oxides such as Ru-SiO2, Ru-TiO2, or Ru-ZrO2.

[0297] The average thickness of the second underlayer 832B may be thinner than that of an underlayer in a typical magnetic recording medium (for example, an underlayer containing Ru), and can be, for example, between 1 nm and 5 nm. Since a seed layer 831 having the above-described structure and the first underlayer 832A are provided below the second underlayer 832B, a good SNR can be obtained even if the average thickness of the second underlayer 832B is as thin as described above. The average thickness of the second underlayer 832B is determined in the same manner as the magnetic layer 13 in the first embodiment. However, the magnification of the TEM image is adjusted appropriately according to the thickness of the second underlayer 832B.

[0298] The magnetic recording medium 830 includes a seed layer 831 and a first underlayer 832A between the base layer 811 and the second underlayer 832B. The seed layer 831 contains Cr, Ni, and Fe and has a face-centered cubic lattice structure, with the (111) plane of this face-centered cubic structure preferentially oriented parallel to the surface of the base layer 811. The first underlayer 832A contains Co and O, with a ratio of the average atomic concentration of O to the average atomic concentration of Co being 1 or more, and has a column structure with an average grain size of 3 nm to 13 nm. This makes it possible to reduce the thickness of the second underlayer 832B and realize a magnetic layer 815 with good crystal orientation and high coercivity while minimizing the use of expensive material Ru.

[0299] The Ru contained in the second underlayer 832B has the same hexagonal close-packed lattice structure as Co, the main component of the magnetic layer 815. Therefore, Ru has the effect of simultaneously improving the crystal orientation and promoting granularity of the magnetic layer 815. Furthermore, in order to further improve the crystal orientation of the Ru contained in the second underlayer 832B, the first underlayer 832A and seed layer 831 are provided below the second underlayer 832B. In the magnetic recording medium 830, the first underlayer 832A, which contains inexpensive CoO having a face-centered cubic lattice structure, achieves almost the same effect (function) as the second underlayer 832B containing Ru. Therefore, the thickness of the second underlayer 832B can be reduced. In addition, a seed layer 831 containing Cr, Ni, and Fe is provided to enhance the crystal orientation of the first underlayer 832A.

[0300] 4. Third Embodiment

[0301] (1) One embodiment of a magnetic recording cartridge

[0302] [Cartridge Configuration]

[0303] This technology also provides a magnetic recording cartridge (also called a tape cartridge) containing a magnetic recording medium according to this technology. Within the magnetic recording cartridge, the magnetic recording medium may be wound, for example, on a reel. The magnetic recording cartridge may include, for example, a communication unit that communicates with a recording and playback device, a storage unit, and a control unit that stores information received from the recording and playback device via the communication unit in the storage unit, and reads the information from the storage unit and transmits it to the recording and playback device via the communication unit in response to a request from the recording and playback device. The information may include adjustment information for adjusting the tension applied in the longitudinal direction of the magnetic recording medium.

[0304] Referring to Figure 2, an example of the configuration of a magnetic recording cartridge 10A equipped with a magnetic recording medium T having the above-described configuration will be explained.

[0305] Figure 2 is an exploded perspective view showing an example of the configuration of a magnetic recording cartridge 10A. The magnetic recording cartridge 10A is a magnetic recording cartridge compliant with the LTO (Linear Tape-Open) standard, and comprises a reel 10C on which a magnetic tape (tape-shaped magnetic recording medium) T is wound, a reel lock 214 and a reel spring 215 for locking the rotation of the reel 10C, a spider 216 for releasing the locked state of the reel 10C, a sliding door 217 that opens and closes a tape outlet 212C provided in the cartridge case 10B spanning the lower shell 212A and the upper shell 212B, a door spring 218 that biases the sliding door 217 to the closed position of the tape outlet 212C, a write protect 219 for preventing accidental erasure, and a cartridge memory 211. The reel 10C is roughly disc-shaped with an opening in the center and is composed of a reel hub 213A and a flange 213B made of a hard material such as plastic. A leader tape LT is connected to one end of the magnetic tape T. A leader pin 220 is provided at the tip of the leader tape LT.

[0306] The cartridge memory 211 is located near one corner of the magnetic recording cartridge 10A. When the magnetic recording cartridge 10A is loaded into the recording / playback device 80, the cartridge memory 211 faces the reader / writer (not shown) of the recording / playback device 80. The cartridge memory 211 communicates with the recording / playback device 30, specifically the reader / writer (not shown), using a wireless communication standard compliant with the LTO standard.

[0307] [Cartridge memory configuration]

[0308] Referring to Figure 11, an example of the configuration of the cartridge memory 211 will be described. The figure 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) according to a specified communication standard, a rectifier / power supply circuit 332 that generates power using induced electromotive force from radio waves received by the antenna coil 331 and rectifies it to produce a power supply, a clock circuit 333 that generates a clock using induced electromotive force from radio waves received by the antenna coil 331, a detection / modulation circuit 334 that detects radio waves received by the antenna coil 331 and modulates the signal transmitted by the antenna coil 331, a controller (control unit) 335 composed of logic circuits, etc., that distinguishes commands and data from the digital signals extracted from the detection / modulation circuit 334 and processes them, and a memory (storage unit) 336 that stores information. The cartridge memory 211 also includes a capacitor 337 connected in parallel with the antenna coil 331, and the antenna coil 331 and capacitor 337 constitute a resonant circuit.

[0309] Memory 336 stores information related to the magnetic recording cartridge 10A. Memory 336 is non-volatile memory (NVM). The storage capacity of memory 336 is preferably about 32KB or more. For example, if the magnetic recording cartridge 10A conforms to the next-generation or later LTO format standard, memory 336 has a storage capacity of about 32KB.

[0310] Memory 336 has a first storage area 336A and a second storage area 336B. The first storage area 336A corresponds to the storage area of ​​a cartridge memory of an LTO standard prior to LTO8 (hereinafter referred to as "conventional cartridge memory") and is an area for storing information compliant with the LTO standard prior to LTO8. Information compliant with the LTO standard prior to LTO8 includes, for example, manufacturing information (e.g., unique number of magnetic recording cartridge 10A, etc.) and usage history (e.g., tape pull count (thread count), etc.).

[0311] The second memory area 336B corresponds to an extended memory area relative to the conventional cartridge memory memory. The second memory area 336B is an area for storing additional information. Here, additional information refers to information related to the magnetic recording cartridge 10A that is not specified in LTO standards prior to LTO8. Examples of additional information include, but are not limited to, tension adjustment information, management ledger data, index information, or thumbnail information of videos stored on the magnetic tape T. The tension adjustment information includes the distance between adjacent servo bands (the distance between servo patterns recorded on adjacent servo bands) when recording data on the magnetic tape T. The distance between adjacent servo bands is an example of width-related information related to the width of the magnetic tape T. Details of the distance between servo bands will be described later. In the following description, the information stored in the first memory area 336A is sometimes referred to as "first information," and the information stored in the second memory area 336B is sometimes referred to as "second information."

[0312] The memory 336 may have multiple banks. In this case, a first storage area 336A may be formed by some of the multiple banks, and a second storage area 336B may be formed by the remaining banks. Specifically, for example, if the magnetic recording cartridge 10A conforms to the next-generation or later LTO format standard, the memory 336 may have two banks with a storage capacity of approximately 16KB, with one of the two banks forming the first storage area 336A and the other bank forming the second storage area 336B.

[0313] The antenna coil 331 induces an induced voltage through electromagnetic induction. The controller 335 communicates with the recording / playback device 80 via the antenna coil 331 using a specified communication standard. Specifically, it performs tasks such as mutual authentication, sending and receiving commands, or exchanging data.

[0314] The controller 335 stores the information received from the recording / playback device 80 via the antenna coil 331 in the memory 336. In response to a request from the recording / playback device 80, the controller 335 reads the information from the memory 336 and transmits it to the recording / playback device 80 via the antenna coil 331.

[0315] (2) Modified magnetic recording cartridge

[0316] [Cartridge Configuration]

[0317] In the above-described embodiment of the magnetic recording cartridge, the case where the magnetic tape cartridge is a single-reel type cartridge was explained, but the magnetic recording cartridge of this technology may also be a two-reel type cartridge. That is, the magnetic recording cartridge of this technology may have one or more (for example, two) reels on which the magnetic tape is wound. Below, with reference to Figure 12, an example of a magnetic recording cartridge of this technology having two reels will be described.

[0318] Figure 12 is an exploded perspective view showing an example of the configuration of a two-reel type cartridge 421. The cartridge 421 comprises an upper half 402 made of synthetic resin, a transparent window member 423 fitted into and fixed to a window portion 402a opened on the upper surface of the upper half 402, a reel holder 422 fixed to the inside of the upper half 402 to prevent the reels 406 and 407 from lifting up, a lower half 405 corresponding to the upper half 402, reels 406 and 407 housed in the space created by combining the upper half 402 and the lower half 405, magnetic tape MT1 wound on the reels 406 and 407, a front lid 409 that closes the front opening created by combining the upper half 402 and the lower half 405, and a back lid 409A that protects the magnetic tape MT1 exposed to this front opening.

[0319] Reel 406 comprises a lower flange 406b having a cylindrical hub portion 406a in the center around which the magnetic tape MT1 is wound, an upper flange 406c that is approximately the same size as the lower flange 406b, and a reel plate 411 sandwiched between the hub portion 406a and the upper flange 406c. Reel 407 has a similar configuration to reel 406.

[0320] The window member 423 is provided with mounting holes 423a at positions corresponding to the reels 406 and 407 for assembling reel holders 422, which are reel holding means to prevent the reels from lifting up. The magnetic tape MT1 is the same as the magnetic tape T in the first embodiment.

[0321] This technology can also employ the following configuration: [1] When dynamic viscoelasticity measurements were performed on a magnetic recording medium at a frequency of 10 Hz and a heating rate of 2 °C / min, the average value A of the loss modulus E'' in the temperature range of 60 °C to 65 °C was obtained. (E”) The pressure is 0.06 GPa or less, and, The average height Rpk of the protruding peaks, measured using a non-contact roughness meter employing optical interference, is 2.4 nm or less. Magnetic recording medium. [2] When the aforementioned dynamic viscoelasticity measurement is performed, the average value A of the storage modulus E' in the temperature range of 60°C to 65°C is obtained. (E’) A magnetic recording medium as described in [1], wherein the power is 6 GPa or less. [3] When the aforementioned dynamic viscoelasticity measurement is performed, the average value A of Tanδ (loss modulus E'' / storage modulus E') in the temperature range of 60°C to 65°C (Tanδ) A magnetic recording medium according to [1] or [2], wherein the ratio is 0.017 or less. [4] The average thickness t of the base layer included in the magnetic recording medium Base A magnetic recording medium according to any one of [1] to [3], wherein the diameter is 4.5 μm or less. [5] The average thickness t of the magnetic recording medium TA magnetic recording medium according to any one of [1] to [4], wherein the diameter is 5.3 μm or less. [6] The magnetic recording medium according to any one of [1] to [5], wherein the stiffness S of the magnetic recording medium is 1.4 mgf / μm or less. [7] When the aforementioned dynamic viscoelasticity measurement is performed, the average value A of the loss modulus E'' in the temperature range of 60°C to 65°C is obtained. (E”) A magnetic recording medium described in any one of [1] to [6], wherein the current is 0.05 GPa or less. [8] When the aforementioned dynamic viscoelasticity measurement is performed, the average value A of the loss modulus E'' in the temperature range of 60°C to 65°C is obtained. (E”) A magnetic recording medium described in any one of [1] to [7], wherein the current is 0.04 GPa or less. [9] A magnetic recording medium according to any one of [1] to [8], wherein the average height Rpk of the protruding peaks is 2.3 nm or less.

[10] A magnetic recording medium according to any one of [1] to [9], wherein the average height Rpk of the aforementioned protruding peaks is 2.2 nm or less.

[11] When the aforementioned dynamic viscoelasticity measurement is performed, the average value of Tanδ A (Tanδ) A magnetic recording medium described in any one of [1] to

[10] , wherein the ratio is 0.016 or less.

[12] When the aforementioned dynamic viscoelasticity measurement is performed, the average value of Tanδ A (Tanδ) A magnetic recording medium described in any one of [1] to

[11] , wherein the value is 0.015 or less.

[13] The magnetic recording medium exhibits a width variation ΔW when subjected to a load of 0.55 N in the longitudinal direction for 40 hours under conditions of 65°C and 40% humidity. 40h However, -600 ppm ≤ ΔW 40h A magnetic recording medium described in any one of [1] to

[12] .

[14] The magnetic recording medium is the magnetic recording medium according to any one of [1] to

[13] , having a magnetic layer containing magnetic powder.

[15] The magnetic recording medium is a vacuum thin-film type magnetic recording medium, as described in any one of [1] to

[13] .

[16] A magnetic recording cartridge in which a magnetic recording medium described in any one of [1] to

[15] is wound onto a reel and housed in a case.

[0322] 5. Examples

[0323] The present technology will be described in more detail below with reference to examples, but the technology is not limited to these examples. Unless otherwise specified, the values ​​of the various parameters that appear in these examples were obtained by the measurement methods described above.

[0324] Magnetic tapes were obtained as described in Examples 1 to 4 and Comparative Examples 1 to 4 below.

[0325] [Example 1]

[0326] (Preparation process for coatings for forming magnetic layers) A coating for forming a magnetic layer was prepared as follows. First, a first composition with the following formulation was kneaded in an extruder. Next, the kneaded first composition and a second composition with the following formulation were added to a stirring tank equipped with a disperser and pre-mixed. Subsequently, dynomill mixing was performed, followed by filtration to prepare the coating for forming a magnetic layer.

[0327] (First composition) Barium ferrite (BaFe 12 O 19 ) Magnetic powder (hexagonal plate shape, average aspect ratio 3.0, average particle volume 1600 nm) 3 ):100 parts by mass Vinyl chloride resin (cyclohexanone solution 30% by mass): 50 parts by mass (Degree of polymerization 300, Mn=10000, contains OSO3K=0.07 mmol / g and secondary OH=0.3 mmol / g as polar groups.) Aluminum oxide powder: 5 parts by mass (α-Al2O3, average particle size 0.1 μm)

[0328] (Second composition) Carbon black: 2 parts by mass (manufactured by Tokai Carbon Co., Ltd., product name: Seast TA) Polyurethane resin (resin solution: 30% by mass of polyurethane resin, 70% by mass of cyclohexanone): 5.56 parts by mass (Polyurethane resin: Number average molecular weight Mn = 25000, Tg 110℃) 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

[0329] Finally, to the magnetic layer-forming coating prepared as described above, 3.3 parts by mass of polyisocyanate (product name: Coronate L, manufactured by Tosoh Corporation) and 2 parts by mass of stearic acid were added as curing agents.

[0330] (Preparation process for paint used to form the base layer) The primer-forming coating was prepared as follows. First, the third composition with the following formulation was kneaded in an extruder. Next, the kneaded third composition and the fourth composition with the following formulation were added to a stirring tank equipped with a disperser and pre-mixed. Subsequently, dynomill mixing was performed, followed by filtration to prepare the primer-forming coating.

[0331] (Third composition) Needle-shaped iron oxide powder: 100 parts by mass (α-Fe2O3, average major axis length 0.12μm) Vinyl chloride resin (cyclohexanone solution 30% by mass): 46 parts by mass (Degree of polymerization 300, Mn=10000, contains OSO3K=0.07 mmol / g and secondary OH=0.3 mmol / g as polar groups.) (Average particle size 20nm)

[0332] (4th composition) Carbon Black: 25 parts Polyurethane resin (resin solution: 30% by mass of polyurethane resin, 70% by mass of cyclohexanone): 36 parts by mass (Polyurethane resin: Number average molecular weight Mn = 25000, Tg 110℃) 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

[0333] Finally, to the primer-forming paint prepared as described above, 2.49 parts by mass of polyisocyanate (product name: Coronate L, manufactured by Tosoh Corporation) and 2 parts by mass of stearic acid were added as curing agents.

[0334] (Preparation process for paint used to form the back layer) The coating for forming the back layer was prepared as follows: The following raw materials were mixed in a stirring tank equipped with a disperser. A coating for forming a back layer was prepared by performing a filtering process.

[0335] Carbon black (manufactured by Asahi Co., Ltd., product name: #80): 100 parts by mass Polyester polyurethane: 100 parts by mass (Manufactured by 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 (product name: Coronate L, manufactured by Tosoh Corporation): 10 parts by mass

[0336] (Film forming process) Using the paint prepared as described above, a magnetic tape was manufactured as described below.

[0337] First, a long PEEK film (base film) with an average thickness of 4.0 μm was prepared as a support to serve as the base layer of the magnetic tape. Next, a primer-forming coating was applied to one main surface of the PEEK film and dried to form a primer layer on that main surface of the PEEK film, such that the average thickness of the final product would be 820 nm. Then, a magnetic layer-forming coating was applied to the primer layer and dried to form a magnetic layer on the primer layer, such that the average thickness of the final product would be 80 nm. Furthermore, the magnetic layer was subjected to vertical orientation treatment using a solenoid coil.

[0338] Next, a back layer forming coating was applied to the other main surface of the PEEK film on which the base layer and magnetic layer had been formed, and dried to form a back layer such that the average thickness of the final product would be 0.3 μm. Then, the PEEK film with the base layer, magnetic layer, and back layer formed was subjected to a curing treatment. After that, calendering was performed to smooth the surface of the magnetic layer.

[0339] (Cutting process) The magnetic tape obtained as described above was cut into strips with a width of 1 / 2 inch (12.65 mm). This resulted in a long, rectangular magnetic tape.

[0340] A magnetic recording cartridge was obtained by winding the 1 / 2-inch wide magnetic tape onto a reel provided inside the cartridge case. A servo signal was recorded on the magnetic tape using a servo track writer. The servo signal consisted of a series of V-shaped magnetic patterns, and two or more of these magnetic patterns were pre-recorded in parallel in the longitudinal direction at a known interval between them (hereinafter referred to as "the interval of the known magnetic pattern series when pre-recorded").

[0341] Using the magnetic recording cartridge, the physical properties of the magnetic tape were measured as described in "(3) Physical Properties and Structure" of section 2 above. These measurement results are shown in Table 1 below. As shown in the same table, the average value A of the storage modulus E' of the magnetic tape in the temperature range of 60°C to 65°C.(E’) It is 2.131, and the average value A of the loss modulus E'' (E”) The value is 0.024, and the mean value of Tanδ A (Tanδ) The value was 0.011. Figure 15 shows the plots of the storage modulus E' and loss modulus E'' against temperature, as measured in the dynamic viscoelasticity measurement. Figure 16 shows the plot of Tanδ against temperature. Furthermore, the average height Rpk of the protruding peaks of the magnetic tape was 2.2. Furthermore, the width variation ΔW of the magnetic tape after 40 hours. 40h The value was -156 ppm. Also, the amplitude variation ΔW 40h The width variation over 40 hours in the measurement is shown in Figure 17 (plot of width variation ΔW against time t). The same figure also shows the width variation ΔW over 40 hours for the magnetic tape of Comparative Example 3, which will be described later.

[0342] [Example 2] A magnetic tape was obtained using the same method as in Example 1, except that the inorganic doping material contained in the magnetic layer was changed as follows. The amount of aluminum oxide powder used in Example 1 was changed from 5 parts by mass to 4 parts by mass. The carbon black used in Example 1 had an average particle size of 120 nm. In Example 2, however, carbon black with an average particle size of 95 nm (manufactured by Tokai Carbon Co., Ltd., product name: Seest SP) was used instead. The amount of carbon black used in Example 2 was the same as in Example 1.

[0343] Furthermore, a magnetic recording cartridge containing the magnetic tape was obtained, similar to Example 1. Using this magnetic recording cartridge, various values ​​were measured, as in Example 1. The measurement results are shown in Table 1.

[0344] [Example 3] A magnetic tape was obtained using the same method as in Example 1, except that the inorganic doping material contained in the magnetic layer was changed as follows. The amount of aluminum oxide powder used in Example 1 was changed from 5 parts by mass to 3.5 parts by mass. The carbon black used in Example 1 had an average particle size of 120 nm. In this example, carbon black with an average particle size of 70 nm (manufactured by Tokai Carbon Co., Ltd., product name: Seest S) was used instead. The amount of carbon black was also changed from 2 parts by mass to 1.5 parts by mass.

[0345] Furthermore, a magnetic recording cartridge containing the magnetic tape was obtained, similar to Example 1. Using this magnetic recording cartridge, various values ​​were measured, as in Example 1. The measurement results are shown in Table 1. [Example 4] A magnetic tape was obtained using the same method as in Example 2, except that a PEEK film that had been stretched in both the longitudinal and transverse directions was used.

[0346] Furthermore, a magnetic recording cartridge containing the magnetic tape was obtained, similar to Example 1. Using this magnetic recording cartridge, various values ​​were measured, as in Example 1. The measurement results are shown in Table 1. It can be seen that the storage modulus can be increased by this stretching process. Furthermore, it can be seen that the loss modulus, bending stiffness, and width variation can also be adjusted by this stretching process.

[0347] [Comparative Example 1] A magnetic tape was obtained using the same method as in Example 1, except that a PEN film was used instead of a PEEK film as the support for the base layer. Furthermore, a magnetic recording cartridge containing the magnetic tape was obtained, similar to Example 1. Using this magnetic recording cartridge, various values ​​were measured, as in Example 1. The measurement results are shown in Table 1.

[0348] [Comparative Example 2] A magnetic tape was obtained using the same method as in Example 1, except that the amount of carbon black in the magnetic layer was changed from 2 parts by mass to 3 parts by mass, and a PET film was used instead of a PEEK film as the support for the base layer. Furthermore, a magnetic recording cartridge containing the magnetic tape was obtained, similar to Example 1. Using this magnetic recording cartridge, various values ​​were measured, as in Example 1. The measurement results are shown in Table 1.

[0349] [Comparative Example 3] A magnetic tape was obtained using the same method as in Example 1, except that the time for Dynomill mixing in the preparation process of the coating for forming the magnetic layer was extended and an aramid film was used instead of a PEEK film as the support for the base layer. Furthermore, a magnetic recording cartridge containing the magnetic tape was obtained, similar to Example 1. Using this magnetic recording cartridge, various values ​​were measured, as in Example 1. The measurement results are shown in Table 1.

[0350] [Comparative Example 4] A magnetic tape was obtained using the same method as in Example 1, except that the amount of carbon black contained in the magnetic layer was changed from 2 parts by mass to 3 parts by mass. Furthermore, a magnetic recording cartridge containing the magnetic tape was obtained, similar to Example 1. Using this magnetic recording cartridge, various values ​​were measured, as in Example 1. The measurement results are shown in Table 1.

[0351] [evaluation] The full-length recording and playback characteristics and SNR of the magnetic tapes contained in each cartridge were evaluated using the magnetic recording cartridges manufactured in Examples 1-4 and Comparative Examples 1-4 after storage at 65°C. The evaluation methods for full-length recording and playback characteristics and SNR are described below.

[0352] (Driving stability during full recording and playback) After storing the magnetic recording cartridge at 65°C and 40RH for two weeks, the magnetic tape was wound onto the take-up reel 32 of the magnetic recording / recovery device 30, with the winding direction reversed (outside and inside), and stored for another two weeks. After this storage, the magnetic tape was fully recorded and reproduced using the magnetic recording / recovery device 30, and the running stability of the magnetic tape was evaluated.

[0353] To evaluate the aforementioned running stability, 40 full-volume tests were performed on each magnetic recording cartridge. In this specification, the number of full-volume tests is also referred to as the FV number. In the 40-volume test, the presence or absence of off-track occurrences during full recording and playback, and the index σ representing driving stability were used. sw The presence or absence of an increase was investigated as follows.

[0354] First, the magnetic recording cartridge was driven using an LTO drive connected to a computer via serial cable communication. Of the five servo bands written on the tape (servo bands 0, 1, 2, 3, and 4), the servo band closest to the upper edge of the tape (i.e., servo band 0) was used to activate the drive head actuator and drive the tape so that the drive head followed the servo track. From the servo signal obtained at that time, a statistical value σ indicating the nonlinearity of the servo pattern was obtained. sw-0 We measured it. Next, using the servo band closest to the lower edge of the tape (i.e., servo band 4), the statistical value σ sw-4 We measured it. The aforementioned statistical value σ sw-0 and σ sw-4 The arithmetic mean of σ is an indicator of magnetic tape running stability. sw That's what I decided. Furthermore, a method for measuring the statistical value indicating the nonlinearity is described in Japanese Patent Application Publication No. 2021-034077.

[0355] For all of the magnetic tapes of Examples 1-3 and Comparative Examples 1-4 manufactured above, the index σ sw I obtained it. Then, each of the following magnetic tapes was evaluated according to the following evaluation criteria. <Evaluation Criteria> Metric σ after 40 full-volume tests sw It was less than 50nm: OK. Metric σ after 40 full-volume tests swIf the value was greater than 50nm, or if the index σ was not reached before 40 full-volume tests were completed, sw The test was not completed because the process exceeded 50nm: NG

[0356] σ sw This indicates the amount of deviation (error) in the reading position of the servo pattern in the width direction of the magnetic recording medium 10 when the servo pattern is reproduced (read) by the recording / playback device 30. In order to accurately adjust the tension in the longitudinal direction of the magnetic recording medium 10, the linearity of the servo band when the servo pattern is read by the recording / playback device 30 should be as high as possible, that is, the amount of deviation of the reading position indicated by σ. sw It is preferable that the value be as low as possible.

[0357] Figure 13 shows the σ that occurs as the magnetic tape moves. sw This figure shows the change over time. As shown in the figure, σ when 40 full-volume tests were performed sw If the σ is less than 50 nm, it is considered that track misalignment is less likely to occur and that the running stability is good. Figure 14 shows the σ associated with the running of the magnetic tape. sw This figure shows the change over time. As shown in the figure, σ when 40 full-volume tests were performed sw When the frequency exceeds 50 nm, track misalignment occurs frequently, causing the magnetic tape to stop running, and thus the running stability is evaluated as poor.

[0358] (SNR: Evaluation of electromagnetic conversion characteristics) First, a loop tester (manufactured by Microphysics) was used to acquire the playback signal from the magnetic tape. The conditions for acquiring the playback signal are described below. head:GMR head speed: 2 m / s Signal: Single recording frequency (10MHz) Recording current: Optimal recording current

[0359] Next, the regenerated signal was captured using a spectrum analyzer with a span of 0 to 20 MHz (resolution bandwidth = 100 kHz, VBW = 30 kHz). Then, the peaks of the captured spectrum were defined as the signal intensity S, and the floor noise (excluding the peaks) was integrated to determine the noise intensity N. The ratio of signal intensity S to noise intensity N (S / N) was then calculated as the signal-to-noise ratio (SNR). Next, the calculated SNR was converted to a relative value (dB) based on the SNR of Comparative Example 1, which was used as a reference medium.

[0360] These evaluation results are listed in Table 1.

[0361] [Table 1]

[0362] As shown in Table 1, the magnetic tapes of Examples 1 to 4 exhibited good overall recording and playback characteristics after storage at 65°C. Specifically, no off-track occurred, and no increase in PES was observed. Furthermore, the width variation of the magnetic tapes of Examples 1 to 4 after storage at 65°C was also small. Moreover, the SNR of all the magnetic tapes of Examples 1 to 4 was superior to that of the magnetic tape of Comparative Example 1. On the other hand, in Comparative Examples 1 and 2, the degree of width change was large on the EOT side of the tape (the side where it connects to the reel inside the cartridge; more specifically, the final part where data can be recorded, approximately 20m inward from the final part that is wound onto the reel), and the head could not follow, causing the tape to stop running. Also, in Comparative Examples 3 and 4, σ sw The increase was significant, and without waiting for the completion of 40 full-volume tests, σ sw It exceeded 50nm. These results indicate that the magnetic recording medium and the magnetic recording cartridge containing the magnetic recording medium according to this technology exhibit excellent storage stability at high temperatures, as well as excellent running stability after storage at high temperatures. Furthermore, it can be seen that the magnetic recording medium and the magnetic recording cartridge containing the magnetic recording medium according to this technology also exhibit excellent electromagnetic conversion characteristics.

[0363] The results shown in Table 1 indicate that by adjusting the average value of the loss modulus E'' and the average height Rpk of the protruding peaks in the temperature range of 60°C to 65°C, it is possible to improve running stability and electromagnetic conversion characteristics after storage in a high-temperature environment. To achieve these effects, the average value is, for example, 0.06 GPa or less, preferably 0.05 GPa or less, more preferably 0.04 GPa or less, and even more preferably 0.03 GPa or less. Also, to achieve these effects, the average height Rpk of the protruding peaks is, for example, 2.4 nm or less, preferably 2.3 nm or less, and more preferably 2.2 nm or less.

[0364] Furthermore, as shown in Table 1, adjusting the average value of the storage modulus E' in the temperature range of 60°C to 65°C is thought to contribute to improved running stability and improved electromagnetic conversion characteristics after storage in high-temperature environments, and is particularly thought to contribute to improved electromagnetic conversion characteristics. Preferably, the average value of the storage modulus E' in the temperature range of 60°C to 65°C is, for example, 6 GPa or less, more preferably 5 GPa or less, even more preferably 4 GPa or less, and particularly preferably 3.5 GPa or less, 3.2 GPa or less, 3.0 GPa or less, or 2.8 GPa or less.

[0365] Furthermore, the results shown in Table 1 suggest that adjusting the bending stiffness of the magnetic tape contributes to improved running stability and improved electromagnetic conversion characteristics after storage in high-temperature environments, and in particular, to improved electromagnetic conversion characteristics. The bending stiffness is preferably 1.4 mgf / μm or less, more preferably 1.3 mgf / μm or less, even more preferably 1.2 mgf / μm or less, 1.1 mgf / μm or less, or 1.0 mgf / μm or less, and particularly preferably 0.9 mgf / μm or less or 0.8 mgf / μm or less.

[0366] Furthermore, as shown in Table 1, it is believed that adjusting the average value of Tanδ (loss modulus E'' / storage modulus E') in the temperature range of 60°C to 65°C also contributes to improving running stability and electromagnetic conversion characteristics after storage in high-temperature environments. Preferably, the average value of Tanδ in the temperature range of 60°C to 65°C is, for example, 0.017 or less, more preferably 0.016 or less, even more preferably 0.015 or less, and particularly preferably 0.014 or less.

[0367] Although embodiments and examples of this technology have been described in detail above, this technology is not limited to the embodiments and examples described above, and various modifications based on the technical concept of this technology are possible.

[0368] For example, the configurations, methods, processes, shapes, materials, and numerical values ​​listed in the above embodiments and examples are merely examples, and different configurations, methods, processes, shapes, materials, and numerical values ​​may be used as needed. Furthermore, the chemical formulas of compounds are representative examples, and the general name of the same compound is not limited to those listed.

[0369] Furthermore, the configurations, methods, processes, shapes, materials, and numerical values ​​of the above-described embodiments and examples can be combined with each other, as long as they do not deviate from the spirit of this technology.

[0370] Furthermore, in this specification, numerical ranges indicated using "~" represent a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described stepwise in this specification, the upper or lower limit of one step in the numerical range may be replaced with the upper or lower limit of another step in the numerical range. Unless otherwise specified, the materials exemplified in this specification may be used individually or in combination of two or more. [Explanation of Symbols]

[0371] 10 Magnetic recording media 11 Base Layer 12 Base layer 13 Magnetic layer 14 Back layer

Claims

1. When dynamic viscoelasticity measurements were performed on a magnetic recording medium at a frequency of 10 Hz and a heating rate of 2°C / min, the average value A of the loss modulus E'' in the temperature range of 60°C to 65°C was obtained. （Ｅ”） The pressure is 0.06 GPa or less, and The average height Rpk of the protruding peaks, measured using a non-contact roughness meter employing optical interference, is 2.4 nm or less. Magnetic recording medium.

2. When the aforementioned dynamic viscoelasticity measurement is performed, the average value A of the storage modulus E' in the temperature range of 60°C to 65°C is obtained. （Ｅ’） The magnetic recording medium according to claim 1, wherein the frequency is 6 GPa or less.

3. When the aforementioned dynamic viscoelasticity measurement is performed, the average value A of Tanδ (loss modulus E'' / storage modulus E') in the temperature range of 60°C to 65°C （Ｔａｎδ） The magnetic recording medium according to claim 1, wherein is 0.017 or less.

4. The average thickness t of the base layer included in the magnetic recording medium Base The magnetic recording medium according to claim 1, wherein the thickness is 4.5 μm or less.

5. The average thickness t of the magnetic recording medium Ｔ The magnetic recording medium according to claim 1, wherein the particle size is 5.3 μm or less.

6. The magnetic recording medium according to claim 1, wherein the stiffness S of the magnetic recording medium is 1.4 mgf / μm or less.

7. When the aforementioned dynamic viscoelasticity measurement is performed, the average value A of the loss modulus E'' in the temperature range of 60°C to 65°C is obtained. （Ｅ”） The magnetic recording medium according to claim 1, wherein the current is 0.05 GPa or less.

8. When the aforementioned dynamic viscoelasticity measurement is performed, the average value A of the loss modulus E'' in the temperature range of 60°C to 65°C is obtained. （Ｅ”） The magnetic recording medium according to claim 1, wherein the current is 0.04 GPa or less.

9. The magnetic recording medium according to claim 1, wherein the average height Rpk of the protruding peaks is 2.3 nm or less.

10. The magnetic recording medium according to claim 1, wherein the average height Rpk of the protruding peaks is 2.2 nm or less.

11. When the above dynamic viscoelasticity measurement is performed, the average value A of Tanδ （Ｔａｎδ） The magnetic recording medium according to claim 1, wherein is 0.016 or less.

12. When the dynamic viscoelasticity measurement is performed, the average value A of Tanδ （Ｔａｎδ） is 0.015 or less. The magnetic recording medium according to claim 1.

13. The magnetic recording medium exhibits a width variation ΔW when subjected to a load of 0.55 N in the longitudinal direction for 40 hours under conditions of 65°C and 40% humidity. 40h However, -600 ppm ≤ ΔW 40h The magnetic recording medium according to claim 1.

14. The magnetic recording medium according to claim 1, wherein the magnetic recording medium has a magnetic layer containing magnetic powder.

15. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is a vacuum thin-film type magnetic recording medium.

16. A magnetic recording cartridge in which the magnetic recording medium described in claim 1 is wound on a reel and housed in a case.

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